%% Papers Published
@article{fds375229,
Author = {Liu, P and Yan, J and Afanasev, A and Benson, SV and Hao, H and Mikhailov,
SF and Popov, VG and Wu, YK},
Title = {Generation of superposed orbital angular momentum beams
using a free-electron laser oscillator.},
Journal = {Optics express},
Volume = {32},
Number = {2},
Pages = {2235-2244},
Publisher = {Optica Publishing Group},
Year = {2024},
Month = {January},
url = {http://dx.doi.org/10.1364/oe.510649},
Abstract = {With wavelength tunability, free-electron lasers (FELs) are
well-suited for generating orbital angular momentum (OAM)
beams in a wide photon energy range. We report here the
first experimental demonstration of OAM beam generation
using an oscillator FEL with the tens of picosecond pulse
duration. Lasing around 458 nm, we have produced the four
lowest orders of superposed Laguerre-Gaussian beams using a
very long FEL resonator of 53.73 m. The produced beams have
good beam quality, excellent stability, and substantial
average power. We have also developed a pulsed operation
mode for these beams with a highly reproducible temporal
structure for a range of repetition rate of 1-30 Hz. This
development can be extended to short wavelengths, for
example to x-rays using a future x-ray FEL oscillator. The
OAM operation of such a storage-ring FEL also paves the way
for the generation of OAM gamma-ray beams via inverse
Compton scattering.},
Doi = {10.1364/oe.510649},
Key = {fds375229}
}
@article{fds374467,
Author = {Kochanneck, L and Ehlers, H and Mikhailov, S and Yan, J and Popov, V and Wallace, P and Swift, G and Ahmed, M and Wu, YK and Jensen, LO and Ristau,
D},
Title = {Enabling Storage Ring FEL for lasing below 170 nm and
production of 120 MeV circularly polarized γ-ray by VUV
mirrors},
Journal = {2023 Conference on Lasers and Electro-Optics Europe and
European Quantum Electronics Conference, CLEO/Europe-EQEC
2023},
Year = {2023},
Month = {January},
ISBN = {9798350345995},
url = {http://dx.doi.org/10.1109/CLEO/EUROPE-EQEC57999.2023.10231725},
Abstract = {The operation of a storage ring free-electron laser (FEL) is
constrained by the shortest wavelength that its cavity can
support. To address this limitation, significant efforts
have been made in recent decades to develop high-reflective
FEL mirrors supporting progressively shorter
wavelengths.},
Doi = {10.1109/CLEO/EUROPE-EQEC57999.2023.10231725},
Key = {fds374467}
}
@article{fds365459,
Author = {Li, W and Yan, J and Liu, P and Wu, YK},
Title = {Synchrotron radiation interferometry for beam size
measurement at low current and in large dynamic
range},
Journal = {Physical Review Accelerators and Beams},
Volume = {25},
Number = {8},
Publisher = {American Physical Society (APS)},
Year = {2022},
Month = {August},
url = {http://dx.doi.org/10.1103/PhysRevAccelBeams.25.080702},
Abstract = {The Synchrotron Radiation Interferometry (SRI) has become a
widely used technique to measure the small transverse size
of the electron beam in the storage ring. In a typical SRI
system for the routine storage ring operation, synchrotron
radiation from a dipole magnet is used to illuminate a
double slit with a small slit opening and a relatively large
slit separation to form a large number of interference
fringes on the observation plane. However, a different type
of SRI is needed for intrabeam scattering (IBS) research to
measure the beam size at ultralow currents and in a wide
dynamic range. Such a system requires a double slit with a
large slit opening to increase the light input while having
the capability of accurately measuring the beam size with a
range of visibility. By examining the impact of the
nonuniform wave amplitude of synchrotron radiation and that
of the varying visibility (due to a changing beam size) on
the beam size measurement, we propose a new physics model
for this type of SRI. This new model is validated using
simulation, showing significantly improved results when
compared with the conventional model. Based on this new
model, we have developed and tested an SRI system dedicated
to the IBS study on the Duke storage ring. This system has
been used successfully to measure electron beams with about
10 μA of current and with a higher current but a variable
size. This new physics model can also improve the
measurement accuracy and consistency of the conventional
SRIs, especially at low visibility.},
Doi = {10.1103/PhysRevAccelBeams.25.080702},
Key = {fds365459}
}
@article{fds363407,
Author = {Li, X and Ahmed, MW and Banu, A and Bartram, C and Crowe, B and Downie, EJ and Emamian, M and Feldman, G and Gao, H and Godagama, D and Grießhammer,
HW and Howell, CR and Karwowski, HJ and Kendellen, DP and Kovash, MA and Leung, KKH and Markoff, DM and McGovern, JA and Mikhailov, S and Pywell,
RE and Sikora, MH and Silano, JA and Sosa, RS and Spraker, MC and Swift, G and Wallace, P and Weller, HR and Whisnant, CS and Wu, YK and Zhao,
ZW},
Title = {Proton Compton Scattering from Linearly Polarized Gamma
Rays.},
Journal = {Physical review letters},
Volume = {128},
Number = {13},
Pages = {132502},
Year = {2022},
Month = {April},
url = {http://dx.doi.org/10.1103/physrevlett.128.132502},
Abstract = {Differential cross sections for Compton scattering from the
proton have been measured at scattering angles of 55°,
90°, and 125° in the laboratory frame using
quasimonoenergetic linearly (circularly) polarized photon
beams with a weighted mean energy value of 83.4 MeV
(81.3 MeV). These measurements were performed at the High
Intensity Gamma-Ray Source facility at the Triangle
Universities Nuclear Laboratory. The results are compared to
previous measurements and are interpreted in the chiral
effective field theory framework to extract the
electromagnetic dipole polarizabilities of the proton, which
gives α_{E1}^{p}=13.8±1.2_{stat}±0.1_{BSR}±0.3_{theo},β_{M1}^{p}=0.2∓1.2_{stat}±0.1_{BSR}∓0.3_{theo}
in units of 10^{-4} fm^{3}.},
Doi = {10.1103/physrevlett.128.132502},
Key = {fds363407}
}
@article{fds368565,
Author = {Calvin R. Howell and Mohammad W. Ahmed and Andrei Afanasev and David
Alesini, John Annand and Ani Aprahamian and Dimiter Balabanski and Stephen Benson and Aron Bernstein and Carl Brune and J.M. Byrd and Bruce
Carlsten, Arthur Champagne and Swapan Chattopadhyay and David
Davis, Evie Downie and J. Matthew Durham and Gerald Feldman and Haiyan Gao and Cameron G.R. Geddes and Harald Griesshammer and Ryoichi Hajim9 and Hao Hao and David Hornidge and Johann Isaak and R.V.F. Janssens and David Kendellen and Mike Kovash and Phillip
Martel, Ulf-G Meissner and Rory Miskimen and Barbara Pasquini and Daniel R. Phillips and Norbert Pietralla and Deniz Savran and Matthias Schinuler and Mark Sikora and W. Michael Snow and Roxanne
Springer, C.M. Sun and Chuanxiang Tang and Brian Tiburzi and Anton
Tonchev, Werner Tornow and Calin Alexander Ur and Dong Wang and H.R.
Weller, V. Werner and Ying K. Wu and Jun Yan and Zheng Zhao and Andreas
Zilges and F.Z. Zomer},
Title = {International Workshop on Next Generation Gamma-Ray
Source},
Journal = {J. Phys. G: Nucl. Part. Phys.},
Volume = {49},
Number = {010502},
Year = {2022},
Key = {fds368565}
}
@article{fds360506,
Author = {Springer, R and Ahmed, M and Howell, C and phillips, D and Griesshammer,
H and Wu, Y},
Title = {International Workshop on Next Generation Gamma-Ray
Source},
Journal = {Journal of Physics G: Nuclear and Particle
Physics},
Volume = {49},
Publisher = {IOP Publishing},
Year = {2021},
Month = {December},
Key = {fds360506}
}
@article{fds359889,
Author = {Wu, YK and Mikhailov, S and Yan, J and Wallace, P and Popov, V and Pentico,
M and Swift, G and Ahmed, MW and Kochanneck, L and Ehlers, H and Jensen,
LO},
Title = {Lasing below 170 nm using an oscillator FEL},
Journal = {Journal of Applied Physics},
Volume = {130},
Number = {18},
Year = {2021},
Month = {November},
url = {http://dx.doi.org/10.1063/5.0064942},
Abstract = {The short wavelength operation of free-electron laser (FEL)
oscillators is limited by the availability of
high-reflectivity, thermally stable, and radiation-resistant
FEL mirrors in the vacuum UV (VUV) wavelength. We report our
recent work to extend the shortest lasing wavelength of the
oscillator FEL to 168.6 nm using a storage ring FEL. This
progress has been made possible by developing a new FEL
configuration with substantially reduced undulator harmonic
radiation on the FEL mirror, a thermally stable FEL optical
cavity, and a new type of high-reflectivity fluoride-based
multilayer coating with a protective capping layer. Using
these fluoride-based mirrors, we have demonstrated storage
ring FEL lasing from 168.6 to 179.7 nm with excellent beam
stability. Employing this VUV FEL in Compton scattering, we
have produced the first 120 MeV gamma rays at the High
Intensity Gamma-ray Source (HIGS). Operating the HIGS in
this new high-energy region will create many new
opportunities for photonuclear physics research, in
particular, the low-energy quantum chromodynamics
research.},
Doi = {10.1063/5.0064942},
Key = {fds359889}
}
@article{fds355909,
Author = {Liu, P and Yan, J and Li, W and Wu, YK},
Title = {Transverse mode analysis for free-space laser beams using
Bayesian analysis.},
Journal = {Applied optics},
Volume = {60},
Number = {12},
Pages = {3344-3352},
Publisher = {The Optical Society},
Year = {2021},
Month = {April},
url = {http://dx.doi.org/10.1364/ao.420217},
Abstract = {Reliable and rapid assessment of the transverse mode quality
of a free-space laser beam has a wide range of applications
in laser development, research, and utilization. It has
become even more important with recent advances in
developing orbital angular momentum photon beams across a
broad spectral region. In this work, a general modal
analysis method for a free-space multimode laser beam has
been developed based on Bayesian analysis. After
transforming mode decomposition into a linear system
problem, a Gaussian probabilistic model is used to find a
closed-form solution. The method is found to be robust with
the presence of Gaussian noise. Prior knowledge about the
mode content can be incorporated into the method to improve
the solution for situations when coherent disturbances or
contamination are present in the laser beam. This method can
be used to analyze the mode content for laser beams in
different bases, such as Hermite-Gaussian (HG) modes and
Laguerre-Gaussian (LG) modes. Three applications of this
method are presented: a detailed modal analysis of the beam
image from the incoherent intensity addition of HG modes and
two examples of mode decomposition using the complex
wavefront from the coherent superposition of HG and LG
modes. The feasibility of this method is demonstrated using
various simulation results. Based on digital images of a
laser beam recorded without complex wavelength-limiting
optics, in principle, this method can be used in a wide
wavelength range from infrared to ultraviolet, and possibly
x ray.},
Doi = {10.1364/ao.420217},
Key = {fds355909}
}
@article{fds355746,
Author = {Laskaris, G and Ji, W and Yan, X and Zhou, J and Zimmerman, WR and Ahmed,
MW and Averett, T and Deltuva, A and Fonseca, AC and Gao, H and Golak, J and Kafkarkou, A and Karwowski, HJ and Lalremruata, B and Manfredi, J and Mueller, JM and Sauer, PU and Skibiński, R and Smith, AP and Tsang, MB and Weller, HR and Witała, H and Wu, YK and Zhao, ZW},
Title = {First measurement of the asymmetry and the
Gerasimov-Drell-Hearn integrand from the He 3- (γ-,p) H 2
reaction at an incident photon energy of 29
MeV},
Journal = {Physical Review C},
Volume = {103},
Number = {3},
Year = {2021},
Month = {March},
url = {http://dx.doi.org/10.1103/PhysRevC.103.034311},
Abstract = {The first measurement of the He3 - (γ - ,p)H2 process was
performed at the High Intensity γ-ray Source (HIγS)
facility at Triangle Universities Nuclear Laboratory using a
circularly polarized, monoenergetic γ-ray beam and a
longitudinally polarized He3 target. The spin-dependent
asymmetry and the contribution from the two-body
photodisintegration to the He3 Gerasimov-Drell-Hearn
integrand are extracted and compared with state-of-the-art
three-nucleon system calculations at the incident photon
energy of 29 MeV. The data are in general agreement with the
various theoretical predictions based on the Siegert theorem
or on explicit inclusion of meson-exchange
currents.},
Doi = {10.1103/PhysRevC.103.034311},
Key = {fds355746}
}
@article{fds349998,
Author = {Liu, P and Yan, J and Hao, H and Wu, YK},
Title = {Phase retrieval for short wavelength orbital angular
momentum beams using knife-edge diffraction},
Journal = {Optics Communications},
Volume = {474},
Year = {2020},
Month = {November},
url = {http://dx.doi.org/10.1016/j.optcom.2020.126077},
Abstract = {Laser beams operating in high order transverse modes,
especially orbital angular momentum (OAM) modes, have been
used increasingly in many frontier research areas. The
characterization of these laser modes and the related
component analysis can be carried out using the retrieved
optical phase. However, conventional iterative phase
retrieval methods, when applied to pure OAM modes, may fail
because their convergence depends on the choice of the
initial phase. Here, we present an improved phase retrieval
method which can incorporate additional phase information
obtained using knife-edge diffraction. Using no additional
optics or few optics available in a wide spectral range,
this method is particularly suitable for short wavelength
lasers such as free-electron lasers (FELs) in the VUV, EUV,
and X-ray regimes. This method has been tested using
simulated beams, and successfully applied to experimentally
generated beams from a HeNe laser and an
FEL.},
Doi = {10.1016/j.optcom.2020.126077},
Key = {fds349998}
}
@article{fds350865,
Author = {Yan, J and Hao, H and Huang, S and Li, J and Litvinenko, VN and Liu, P and Mikhailov, SF and Popov, VG and Swift, G and Vinokurov, NA and Wu,
YK},
Title = {Polarization control of a free-electron laser oscillator
using helical undulators of opposite helicities},
Journal = {Physical Review Accelerators and Beams},
Volume = {23},
Number = {6},
Year = {2020},
Month = {June},
url = {http://dx.doi.org/10.1103/PhysRevAccelBeams.23.060702},
Abstract = {Polarized photon beams provide a unique experimental tool
for the study of various polarization-dependent physical
processes. Here, we report the experimental demonstration of
full polarization control of an oscillator free-electron
laser (FEL) using helical undulators of opposite helicities.
Using two helical undulator magnets of opposite helicities
and a buncher magnet in between, we have generated a
linearly polarized FEL beam with any desirable polarization
direction. With the development of a high-precision FEL
polarimeter, we are able to optimize the highly polarized
FEL beams in visible wavelengths and measure the
polarization with high accuracy, demonstrating linear
polarization Plin>0.99 on the routine basis and with the
maximum polarization reaching Plin=0.998. In this paper, we
describe the FEL configuration, experimental setup, and
related beam diagnostics, including the newly developed
high-precision FEL polarimeter. We report our experimental
approaches to generate, tune up, and characterize the
polarization controllable FEL beams and share a new insight
into how high-degree polarization is realized based upon our
investigation of the temporal structure of the FEL beam.
This FEL polarization control technique has been used
successfully to generate a polarization controllable Compton
γ-ray beam for nuclear physics experiments.},
Doi = {10.1103/PhysRevAccelBeams.23.060702},
Key = {fds350865}
}
@article{fds330538,
Author = {Li, X and Ahmed, MW and Banu, A and Bartram, C and Crowe, B and Downie, EJ and Emamian, M and Feldman, G and Gao, H and Godagama, D and Grießhammer,
HW and Howell, CR and Karwowski, HJ and Kendellen, DP and Kovash, MA and Leung, KKH and Markoff, D and Mikhailov, S and Pywell, RE and Sikora,
MH and Silano, JA and Sosa, RS and Spraker, MC and Swift, G and Wallace, P and Weller, HR and Whisnant, CS and Wu, YK and Zhao, ZW},
Title = {Compton scattering from $^{4}\mathrm{He}$ at the TUNL
$\mathrm{HI}\ensuremath{\gamma}\mathrm{S}$
facility},
Journal = {PRC},
Volume = {101},
Number = {3},
Pages = {034618},
Publisher = {American Physical Society},
Year = {2020},
Month = {March},
url = {http://dx.doi.org/10.1103/PhysRevC.101.034618},
Abstract = {Differential cross sections for elastic Compton scattering
from He4 have been measured with high statistical precision
at the High Intensity γ-ray Source at laboratory scattering
angles of 55°, 90°, and 125° using a quasi-monoenergetic
photon beam with a weighted mean energy value of 81.3 MeV.
The results are compared to previous measurements and
similar fore-aft asymmetry in the angular distribution of
the differential cross sections is observed. This
experimental work is expected to strongly motivate the
development of effective-field-theory calculations of
Compton scattering from He4 to fully interpret the
data.},
Doi = {10.1103/PhysRevC.101.034618},
Key = {fds330538}
}
@article{fds341597,
Author = {Gai, M and Schweitzer, D and Stern, SR and Young, AH and Smith, R and Cwiok, M and Bihalowicz, JS and Czyrkowski, H and Dabrowski, R and Dominik, W and Fijalkowska, A and Janas, Z and Janiak, L and Korgul, A and Matulewicz, T and Mazzocchi, C and Pfützner, M and Zaremba, M and Balabanski, D and Gheorghe, I and Matei, C and Tesileanu, O and Zamfir,
NV and Ahmed, MW and Henshaw, SS and Howell, CR and Mueller, JM and Myers,
LS and Stave, S and Sun, C and Weller, HR and Wu, YK and Breskin, A and Dangendorf, V and Tittelmeier, K and Freer, M},
Title = {Time Projection Chamber (TPC) detectors for nuclear
astrophysics studies with gamma beams},
Journal = {Nuclear Instruments and Methods in Physics Research, Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {954},
Year = {2020},
Month = {February},
url = {http://dx.doi.org/10.1016/j.nima.2019.01.006},
Abstract = {Gamma-Beams at the HIγS facility in the USA and anticipated
at the ELI-NP facility, now constructed in Romania, present
unique new opportunities to advance research in nuclear
astrophysics; not the least of which is resolving open
questions in oxygen formation during stellar helium burning
via a precise measurement of the 12C(α,γ) reaction. Time
projection chamber (TPC) detectors operating with low
pressure gas (as an active target) are ideally suited for
such studies. We review the progress of the current research
program and plans for the future at the HIγS facility with
the optical readout TPC (O-TPC) and the development of an
electronic readout TPC for the ELI-NP facility
(ELITPC).},
Doi = {10.1016/j.nima.2019.01.006},
Key = {fds341597}
}
@article{fds353326,
Author = {Placzek, W and Abramov, A and Alden, SE and Fernandez, RA and Antsiferov, PS and Apyan, A and Bartosik, H and Bessonov, EG and Biancacci, N and Bieron, J and Bogacz, A and Bosco, A and Bruce, R and Budker, D and Cassou, K and Castelli, F and Chaikovska, I and Curatolo,
C and Czodrowski, P and Derevianko, A and Dupraz, K and Dutheil, Y and Dzierzega, K and Fedosseev, V and Martinez, NF and Gibson, SM and Goddard, B and Gorzawski, A and Hirlander, S and Jowett, JM and Kersevan, R and Kowalska, M and Krasny, MW and Kroeger, F and Kuchler,
D and Lamont, M and Lefevre, T and Manglunki, D and Marsh, B and Martens,
A and Molson, J and Nutarelli, D and Nevay, LJ and Petrenko, A and Petrillo, V and Redaelli, S and Peinaud, Y and Pustelny, S and Rochester, S and Sapinski, M and Schaumann, M and Scrivens, R and Serafini, L and Shevelko, VP and Stoehlker, T and Surzhykov, A and Tolstikhina, I and Velotti, F and Weber, G and Wu, YK and Yin-Vallgren,
C and Zanetti, M and Zimmermann, F and Zolotorev, MS and Zomer,
F},
Title = {The gamma factory project at cern: A new generation of
research tools made of light},
Journal = {Acta Physica Polonica B, Proceedings Supplement},
Volume = {13},
Number = {4},
Pages = {645-652},
Year = {2020},
Month = {January},
url = {http://dx.doi.org/10.5506/APHYSPOLBSUPP.13.645},
Abstract = {The Gamma Factory project offers the possibility of creating
novel research tools by producing relativistic beams of
highly ionised atoms in CERN's accelerator complex and
exciting their atomic degrees of freedom by lasers to
produce strongly collimated high-energy photon beams.
Intensity of such beams would exceed by several orders of
magnitude the ones offered by the presently operating light
sources, in the particularly interesting energy domain from
about 100 keV to above 400 MeV. In this energy regime, the
high-intensity photon beams can be used to produce secondary
beams of polarised electrons, polarised positrons, polarised
muons, neutrinos, neutrons and radioactive ions. New
research opportunities in many domains of physics, from
particle physics through nuclear physics to atomic physics,
can be opened by the Gamma Factory scientific programme
based on the above primary and secondary beams. Except for
basic research, it offers also a possibility for various
application studies, e.g. in medical physics and nuclear
power.},
Doi = {10.5506/APHYSPOLBSUPP.13.645},
Key = {fds353326}
}
@article{fds344683,
Author = {Yan, J and Mueller, JM and Ahmed, MW and Hao, H and Huang, S and Li, J and Litvinenko, VN and Liu, P and Mikhailov, SF and Popov, VG and Sikora,
MH and Vinokurov, NA and Wu, YK},
Title = {Precision control of gamma-ray polarization using a crossed
helical undulator free-electron laser},
Journal = {Nature Photonics},
Volume = {13},
Number = {9},
Pages = {629-635},
Year = {2019},
Month = {September},
url = {http://dx.doi.org/10.1038/s41566-019-0467-6},
Abstract = {Polarized gamma-ray beams are a precise and selective probe
for studying fundamental questions about nuclear structure
and hadron properties. Improvements to this probe require
new experimental approaches that can produce high-flux
gamma-ray beams with easily switchable pure polarization
states. Here, we report an optics-free method to precisely
control the polarization of a Compton gamma-ray beam. Using
a free-electron laser (FEL) oscillator with two helical
undulator magnets of opposite helicities, we have produced a
linearly polarized FEL beam with a variable polarization
direction and an unprecedented degree of linear
polarization, PLin = 0.997. With this FEL as a photon drive,
we are able to generate Compton gamma-ray beams having
either left/right-circular polarization or rotatable linear
polarization. The linearly polarized gamma-ray beam has been
characterized and shows PLin = 0.97. This demonstrated
polarization control technique is well suited for high-flux
gamma-ray production with any level of FEL
power.},
Doi = {10.1038/s41566-019-0467-6},
Key = {fds344683}
}
@article{fds342772,
Author = {Pan, Z and Byrd, J and Hao, H and Huang, W and Li, D and Sun, C and Wu, YK and Tang, C},
Title = {Design and dynamic studies for a compact storage ring to
generate gamma-ray light source based on Compton
backscattering technique},
Journal = {Physical Review Accelerators and Beams},
Volume = {22},
Number = {4},
Year = {2019},
Month = {April},
url = {http://dx.doi.org/10.1103/PhysRevAccelBeams.22.040702},
Abstract = {As the development of nuclear physics and atomic sciences
progresses, monochromatic and high-flux gamma-ray light
sources are highly demanded by many experiments in these
fields. We have designed a compact storage ring for
gamma-ray source generation based on the Compton
backscattering technique. The energy range of the electron
beam stored in the ring will be from 500 to 800 MeV, with
the capability of generating a gamma ray with an energy
range from about 4 to 10 MeV. The maximum energy loss for an
electron could be more than 1% for one scattering event,
which could have a significant impact on electron beam
dynamics. To study this impact, a 6D macroparticle tracking
code has been developed by including the Compton scattering,
damping, quantum excitation, and synchrotron radiation in
the storage ring. The equilibrium states have been studied
with this code, and the results show good agreement with
theoretical predictions. The electron beam loss rate induced
by Compton scattering has also been investigated by varying
the input laser beam parameters. This study allows us to
optimize the storage ring operation for a stable, high-flux,
and narrow-bandwidth gamma-ray beam generation.},
Doi = {10.1103/PhysRevAccelBeams.22.040702},
Key = {fds342772}
}
@article{fds345432,
Author = {Płaczek, W and Abramov, A and Alden, SE and Alemany Fernandez and R and Antsiferov, PS and Apyan, A and Bartosik, H and Bessonov, EG and Biancacci, N and Bieroń, J and Bogacz, A and Bosco, A and Bruce, R and Budker, D and Cassou, K and Castelli, F and Chaikovska, I and Curatolo,
C and Czodrowski, P and Derevianko, A and Dupraz, K and Dutheil, Y and Dzierżęga, K and Fedosseev, V and Fuster Martinez and N and Gibson,
SM and Goddard, B and Gorzawski, A and Hirlander, S and Jowett, J and Kersevan, R and Kowalska, M and Krasny, MW and Kroeger, F and Lamont, M and Lefevre, T and Manglunki, D and Marsh, B and Martens, A and Molson, J and Nutarelli, D and Nevay, LJ and Petrenko, A and Petrillo, V and Radaelli,
S and Pustelny, S and Rochester, S and Sapinski, M and Schaumann, M and Serafini, L and Shevelko, VP and Stoehlker, T and Surzhikov, A and Tolstikhina, I and Velotti, F and Weber, G and Wu, YK and Yin-Vallgren,
C and Zanetti, M and Zimmermann, F and Zolotorev, MS and Zomer,
F},
Title = {Gamma factory at CERN - Novel research tools made of
light},
Journal = {Acta Physica Polonica B},
Volume = {50},
Number = {6},
Pages = {1191-1203},
Year = {2019},
Month = {January},
url = {http://dx.doi.org/10.5506/APhysPolB.50.1191},
Abstract = {We discuss the possibility of creating novel research tools
by producing and storing highly relativistic beams of highly
ionised atoms in the CERN accelerator complex, and by
exciting their atomic degrees of freedom with lasers to
produce high-energy photon beams. Intensity of such photon
beams would be by several orders of magnitude higher than
offered by the presently operating light sources, in the
particularly interesting γ-ray energy domain of 0.1-400
MeV. In this energy range, the high-intensity photon beams
can be used to produce secondary beams of polarised
electrons, polarised positrons, polarised muons, neutrinos,
neutrons and radioactive ions. New research opportunities in
a wide domain of fundamental and applied physics can be
opened by the Gamma Factory scientific programme based on
the above primary and secondary beams.},
Doi = {10.5506/APhysPolB.50.1191},
Key = {fds345432}
}
@article{fds354997,
Author = {Dutheil, Y and Abramov, A and Alden, SE and Alemany Fernández and R and Antsiferov, PS and Apyan, A and Bartosik, H and Bessonov, EG and Biancacci, N and Bieron, J and Bogacz, A and Bosco, A and Bruce, R and Budker, D and Cassou, K and Castelli, F and Chaikovska, I and Curatolo,
C and Czodrowski, P and Derevianko, A and Dupraz, K and Dzierzega, K and Fedosseev, V and Fuster Martinez and N and Gibson, SM and Goddard, B and Gorzawski, A and Hirlander, S and Jowett, JM and Kersevan, R and Kowalska, M and Krasny, MW and Kroeger, F and Kuchler, D and Lamont, M and Lefevre, T and Manglunki, D and Marsh, B and Martens, A and Molson, J and Nutarelli, D and Nevay, LJ and Petrenko, A and Petrillo, V and Płaczek,
W and Redaelli, S and Peinaud, Y and Pustelny, S and Rochester, S and Sapinski, M and Schaumann, M and Scrivens, R and Serafini, L and Shevelko, VP and Stoehlker, T and Surzhykov, A and Tolstikhina, I and Velotti, F and Weber, G and Wu, YK and Yin-Vallgren, C and Zanetti, M and Zimmermann, F and Zolotorev, MS and Zomer, F},
Title = {Gamma factory for CERN initiative - Progress
report},
Journal = {Proceedings of Science},
Volume = {364},
Year = {2019},
Month = {January},
Abstract = {The Gamma Factory (GF) initiative proposes to use partially
stripped ion (PSI) beams as drivers of a new type of
high-intensity and high-energy (0.1-400MeV) photon source.
As part of the ongoing Physics Beyond Collider studies,
initial beam tests were carried out in 2017 and 2018 at the
SPS and LHC with partially stripped xenon and lead beams.
This contribution discusses the results of these tests and
the preparations for the next GF R&D step: the
proof-of-principle experiment at the SPS to study
interaction of PSI beams with the laser light.},
Key = {fds354997}
}
@article{fds341884,
Author = {Li, B and Hao, H and Li, JY and Wu, YK},
Title = {Transverse beam profile measurement system for the Duke
storage ring},
Journal = {Nuclear Instruments and Methods in Physics Research, Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {911},
Pages = {45-50},
Year = {2018},
Month = {December},
url = {http://dx.doi.org/10.1016/j.nima.2018.09.102},
Abstract = {The transverse beam emittance is a crucial parameter
determining the brightness of an electron storage ring based
synchrotron radiation source. The beam emittance is
typically determined using the transverse electron beam size
and the beta function at a particular location. For a low
energy storage ring, the direct imaging method using
visible/UV light has many advantages, including being
simple, straightforward, and cost-effective. The resolution
of such a system can be quite adequate for measuring
electron beams with a reasonably large transverse beam size.
In this work, we present the development of a new transverse
beam profile measurement system for the Duke storage ring.
This new system has been characterized to allow absolute
measurements of the electron beam size while achieving
better system resolution than previously thought possible
for the direct imaging technique. The preliminary
measurement results show that this system is capable of
measuring the horizontal beam size over a wide range of the
electron beam energies and currents. The system has also
been demonstrated as a useful tool to study the intra-beam
scattering related emittance increase in the storage
ring.},
Doi = {10.1016/j.nima.2018.09.102},
Key = {fds341884}
}
@article{fds374957,
Author = {Krasny, MW and Bessonov, EG and Budker, D and Cassou, K and Chaikovska,
I and Chehab, R and Dupraz, K and Martens, A and Zomer, F and Curatolo, C and Serafini, L and Dadoun, O and Czodrowski, P and Jowett, J and Fernandez,
RA and Kowalska, M and Lamont, M and Manglunki, D and Petrenko, A and Zimmermann, F and Placzek, W and Wu, YK and Zolotorev,
MS},
Title = {The Gamma Factory proposal for CERN},
Journal = {CERN-Proceedings},
Volume = {1},
Pages = {253-256},
Year = {2018},
Month = {January},
ISBN = {9789290835127},
url = {http://dx.doi.org/10.23727/CERN-Proceedings-2018-001.249},
Abstract = {This contribution discusses the possibility of broadening
the present CERN research programme by a new component
making use of a novel concept of the light source. The
proposed, Partially Stripped Ion beam driven, light source
is the backbone of the Gamma Factory initiative. It could be
realised at CERN by using the infrastructure of the already
existing accelerators. It could push the intensity limits of
the presently operating light-sources by at least 7 orders
of magnitude, reaching the flux of the order of 1017
photons/s, in the particularly interesting γ-ray energy
domain of 1 ≤ Ephoton ≤ 400 MeV. This domain is out of
reach for the FEL-based light sources based on subTeV
energy-range electron beams. The unprecedented-intensity,
energy-tuned, quasi-monochromatic gamma beams, together with
the gamma-beams-driven secondary beams of polarised
positrons, polarised muons, neutrinos, neutrons and
radioactive ions would constitute the basic research tools
of the proposed Gamma Factory. A broad spectrum of new
opportunities, in a vast domain of uncharted fundamental and
applied physics territories, could be opened by the Gamma
Factory research programme.},
Doi = {10.23727/CERN-Proceedings-2018-001.249},
Key = {fds374957}
}
@article{fds360077,
Author = {Pan, Z and Sun, C and Byrd, J and Huang, W and Tang, C and Wu, YK and Hao,
H},
Title = {Low energy compact storage ring design for Compton gamma-ray
light source},
Journal = {IPAC 2017 - Proceedings of the 8th International Particle
Accelerator Conference},
Pages = {921-923},
Year = {2017},
Month = {July},
ISBN = {9783954501823},
Abstract = {Gamma-ray sources with high flux and spectral densities are
highly demanded by many nuclear experiments. We design a low
energy compact storage ring to produce gamma-ray with energy
in the range of 4-20 MeV based on Compton backscattering
technique. The storage ring energy is 500-800 MeV with the
circumference of about 59 m and natural emittance of about 3
nm·rad at 500 MeV. In this paper, we present the storage
ring lattice design and propose two collision configurations
for Compton gamma-ray generation. Intrabeam scattering has
been investigated which can increase emittance from 3
nm·rad to 6 nm·rad horizontally for 500 MeV ring. We also
discuss how Compton scattering affects longitudinal and
transverse beam dynamics by tracking macro particles using
our parallel simulation code. Based on this study, we can
further optimize our storage ring lattice design for the
higher gamma-ray flux production.},
Key = {fds360077}
}
@article{fds329977,
Author = {Li, W and Hao, H and Mikhailov, SF and Popov, V and Li, WM and Wu,
YK},
Title = {Compensation for booster leakage field in the Duke storage
ring},
Journal = {Chinese Physics C},
Volume = {41},
Number = {1},
Pages = {017002-017002},
Publisher = {IOP Publishing},
Year = {2017},
Month = {January},
url = {http://dx.doi.org/10.1088/1674-1137/41/1/017002},
Abstract = {The High Intensity Gamma-ray Source (HIGS) at Duke
University is an accelerator-driven Compton gamma-ray
source, providing high flux gamma-ray beam from 1 MeV to 100
MeV for photo-nuclear physics research. The HIGS facility
operates three accelerators, a linac pre-injector (0.16
GeV), a booster injector (0.16 - 1.2 GeV), and an electron
storage ring (0.24 - 1.2 GeV). Because of the proximity of
the booster injector to the storage ring, the magnetic field
of the booster dipoles close to the ring can significantly
alter the closed orbit in the storage ring being operated in
the low energy region. This type of orbit distortion can be
a problem for certain precision experiments which demand a
high degree of energy consistency of the gamma-ray beam.
This energy consistency can be achieved by maintaining
consistent aiming of the gamma-ray beam, and therefore a
steady electron beam orbit and angle at the Compton
collision point. To overcome the booster leakage field
problem, we have developed an orbit compensation scheme.
This scheme is developed using two fast orbit correctors and
implemented as a feedforward which is operated transparently
together with the slow orbit feedback system. In this paper,
we will describe the development of this leakage field
compensation scheme, and report the measurement results,
which demonstrate the effectiveness of the
scheme.},
Doi = {10.1088/1674-1137/41/1/017002},
Key = {fds329977}
}
@article{fds350213,
Author = {Yan, J and Hao, H and Mikhailov, S and Popov, V and Huang, S and Li, JY and Litvinenko, VN and Vinokurov, NA and Wu, YK},
Title = {Polarization control of storage ring FELs using cross
polarized helical undulators},
Journal = {Proceedings of the 38th International Free-Electron Laser
Conference, FEL 2017},
Pages = {235-239},
Year = {2017},
Month = {January},
ISBN = {9783954501793},
url = {http://dx.doi.org/10.18429/JACoW-FEL2017-TUC01},
Abstract = {For more than two decades, accelerator researchers have been
working to gain control of polarization of synchrotron
radiation and FELs using non-optical means. In 2005, using
mixed linear and helical undulators, the first experimental
demonstration of polarization control of an FEL beam was
realized with the Duke storage ring FEL. With the recent
upgrade of the undulator system, the Duke FEL can be
operated with up to four helical undulators simultaneously.
Using two sets of helical undulators with opposite
helicities, for the first time, we have demonstrated full
control of the polarization of a storage ring FEL, including
helicity switching and rotat-able linear polarization. The
helicity switching of the FEL beam has been realized with
good lasing up to a few Hertz. The generation of a linearly
polarized FEL beam using a set of cross polarized helical
undulators has been demonstrated with a high degree of
polarization (Plin > 0.95). The FEL polarization direction
can be fully controlled using a buncher magnet. Furthermore,
the use of non-optical means to control the FEL polarization
allows us to extend polarization control to γ-ray beams via
Compton scattering. For the first time, we have produced
linearly polarized Compton γ-ray beams with the rotatable
polarization direction using helical undulators.},
Doi = {10.18429/JACoW-FEL2017-TUC01},
Key = {fds350213}
}
@article{fds329978,
Author = {Li, W and Hao, H and Mikhailov, SF and Xu, W and Li, JY and Li, WM and Wu,
YK},
Title = {Study of magnetic hysteresis effects in a storage ring using
precision tune measurement},
Journal = {Chinese Physics C},
Volume = {40},
Number = {12},
Pages = {127002-127002},
Publisher = {IOP Publishing},
Year = {2016},
Month = {December},
url = {http://dx.doi.org/10.1088/1674-1137/40/12/127002},
Abstract = {With the advances in accelerator science and technology in
recent decades, the accelerator community has focused on the
development of next-generation light sources, for example
diffraction-limited storage rings (DLSRs), which require
precision control of the electron beam energy and betatron
tunes. This work is aimed at understanding magnet hysteresis
effects on the electron beam energy and lattice focusing in
circular accelerators, and developing new methods to gain
better control of these effects. In this paper, we will
report our recent experimental study of the magnetic
hysteresis effects and their impacts on the Duke storage
ring lattice using the transverse feedback based precision
tune measurement system. The major magnet hysteresis effects
associated with magnet normalization and lattice ramping are
carefully studied to determine an effective procedure for
lattice preparation while maintaining a high degree of
reproducibility of lattice focusing. The local hysteresis
effects are also studied by measuring the betatron tune
shifts which result from adjusting the setting of a
quadrupole. A new technique has been developed to precisely
recover the focusing strength of the quadrupole by returning
it to a proper setting to overcome the local hysteresis
effect.},
Doi = {10.1088/1674-1137/40/12/127002},
Key = {fds329978}
}
@article{fds329979,
Author = {Yan, J and Hao, H and Li, JY and Mikhailov, SF and Popov, VG and Vinokurov,
NA and Huang, S and Wu, J and Günster, S and Wu, YK},
Title = {Storage ring two-color free-electron laser},
Journal = {Physical Review Accelerators and Beams},
Volume = {19},
Number = {7},
Publisher = {American Physical Society (APS)},
Year = {2016},
Month = {July},
url = {http://dx.doi.org/10.1103/PhysRevAccelBeams.19.070701},
Abstract = {We report a systematic experimental study of a storage ring
two-color free-electron laser (FEL) operating simultaneously
in the infrared (IR) and ultraviolet (UV) wavelength
regions. The two-color FEL lasing has been realized using a
pair of dual-band high-reflectivity FEL mirrors with two
different undulator configurations. We have demonstrated
independent wavelength tuning in a wide range for each
lasing color, as well as harmonically locked wavelength
tuning when the UV lasing occurs at the second harmonic of
the IR lasing. Precise power control of two-color lasing
with good power stability has also been achieved. In
addition, the impact of the degradation of FEL mirrors on
the two-color FEL operation is reported. Furthermore, we
have investigated the temporal structures of the two-color
FEL beams, showing simultaneous two-color micropulses with
their intensity modulations displayed as FEL
macropulses.},
Doi = {10.1103/PhysRevAccelBeams.19.070701},
Key = {fds329979}
}
@article{fds329980,
Author = {Li, W and Hao, H and Xu, W and Wu, YK},
Title = {Direct and high resolution beta-function measurements for
storage ring lattice characterization},
Journal = {IPAC 2016 - Proceedings of the 7th International Particle
Accelerator Conference},
Pages = {3272-3274},
Year = {2016},
Month = {January},
ISBN = {9783954501472},
Abstract = {Betatron functions are a set of commonly used merits to
characterize the lattice performance of a circular
accelerator. The betatron functions in many accelerators can
be computed using a lattice model trained or calibrated
using a set of closed orbit responses, which is exemplified
by the widely used Linear Optics from Closed Orbit (LOCO)
technique. However, for some accelerators, like Duke storage
ring with quad-sextupole combined function magnets, LOCO
cannot be employed in any straight forward manner. In this
case, direct measurements for betatron function are
required. One way to determine betatron functions at the
location of quadrupoles for a circular accelerator is to use
the relationship between the quadrupole strength variations
and the corresponding betatron tune change. In this paper,
we present a set of carefully developed techniques to
measure the betatron functions at the location of
quadrupoles, which allow us to achieve extremely high
resolution. Measurement errors will be discussed, and the
detailed measurement technique will be present. Finally, the
experimental results of betatron function measurements in
the Duke storage ring with statistical error on the order of
1% will be presented.},
Key = {fds329980}
}
@article{fds292654,
Author = {Laskaris, G and Yan, X and Mueller, JM and Zimmerman, WR and Xiong, W and Ahmed, MW and Averett, T and Chu, PH and Deltuva, A and Flower, C and Fonseca, AC and Gao, H and Golak, J and Heideman, JN and Karwowski, HJ and Meziane, M and Sauer, PU and Skibiński, R and Strakovsky, II and Weller, HR and Witała, H and Wu, YK},
Title = {Measurement of the doubly-polarized He3→(γ→,n)pp
reaction at 16.5 MeV and its implications for the GDH sum
rule},
Journal = {Physics Letters, Section B: Nuclear, Elementary Particle and
High-Energy Physics},
Volume = {750},
Pages = {547-551},
Publisher = {Elsevier BV},
Year = {2015},
Month = {November},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2015.09.065},
Abstract = {We report new measurements of the double-polarized
photodisintegration of 3He at an incident photon energy of
16.5 MeV, carried out at the High Intensity γ-ray Source
(HIγS) facility located at Triangle Universities Nuclear
Laboratory (TUNL). The spin-dependent double-differential
cross sections and the contribution from the three-body
channel to the Gerasimov-Drell-Hearn (GDH) integrand were
extracted and compared with the state-of-the-art three-body
calculations. The calculations, which include the Coulomb
interaction and are in good agreement with the results of
previous measurements at 12.8 and 14.7 MeV, deviate from the
new cross section results at 16.5 MeV. The GDH integrand was
found to be about one standard deviation larger than the
maximum value predicted by the theories.},
Doi = {10.1016/j.physletb.2015.09.065},
Key = {fds292654}
}
@article{fds292653,
Author = {Wu, YK and Yan, J and Hao, H and Li, JY and Mikhailov, SF and Popov, VG and Vinokurov, NA and Huang, S and Wu, J},
Title = {Widely Tunable Two-Color Free-Electron Laser on a Storage
Ring.},
Journal = {Physical review letters},
Volume = {115},
Number = {18},
Pages = {184801},
Year = {2015},
Month = {October},
ISSN = {0031-9007},
url = {http://dx.doi.org/10.1103/physrevlett.115.184801},
Abstract = {With a wide wavelength tuning range, free-electron lasers
(FELs) are well suited for producing simultaneous lasing at
multiple wavelengths. We present the first experimental
results of a novel two-color storage ring FEL. With three
undulators and a pair of dual-band mirrors, the two-color
FEL can lase simultaneously in infrared (IR) around 720 nm
and in ultraviolet (UV) around 360 nm. We have demonstrated
independent wavelength tuning in a wide range (60 nm in IR
and 24 nm in UV). We have also realized two-color harmonic
operation with the UV lasing tuned to the second harmonic of
the IR lasing. Furthermore, we have demonstrated good power
stability with two-color lasing, and good control of the
power sharing between the two colors.},
Doi = {10.1103/physrevlett.115.184801},
Key = {fds292653}
}
@article{fds249241,
Author = {Weller, HR and Ahmed, MW and Wu, YK},
Title = {Nuclear Physics Research at the High Intensity Gamma-Ray
Source (HIγS)},
Journal = {Nuclear Physics News},
Volume = {25},
Number = {3},
Pages = {19-24},
Publisher = {Informa UK Limited},
Year = {2015},
Month = {July},
ISSN = {1061-9127},
url = {http://dx.doi.org/10.1080/10619127.2015.1035932},
Abstract = {The High Intensity γ-Ray Source (HIγS), operated by the
Triangle Universities Nuclear Laboratory and located on the
campus of Duke University, is presently able to provide
nearly mono-energetic polarized gamma ray beams with
energies ranging from 1 to 100 MeV. These beams are produced
by Compton backscattering photons produced by a
free-electron laser (FEL) from the same relativistic
electron beam that powers the FEL inside of an electron
storage ring. The maximum total intensity of these g-ray
beams produced in the vicinity of 10 MeV is approximately 3
× 1010 γ/s, making HIγS the most intense Compton γ-ray
source ever built and operated [1].},
Doi = {10.1080/10619127.2015.1035932},
Key = {fds249241}
}
@article{fds320333,
Author = {Li, W and Li, J and Hao, H and Mikhailov, SF and Popov, V and Wu,
YK},
Title = {Measuring Duke storage ring lattice using tune based
technique},
Journal = {6th International Particle Accelerator Conference, IPAC
2015},
Pages = {293-296},
Year = {2015},
Month = {January},
ISBN = {9783954501687},
Abstract = {The Duke electron storage ring is a dedicated driver for
oscillator Free-Electron Lasers (FELs). A 34 m long straight
section of the storage ring is used to host up to four FEL
wigglers in several different configurations. A total of six
wigglers, two planar OK-4 wigglers and four helical OK-5
wigglers, are available for FEL research. The storage ring
magnetic lattice has to be designed with great flexibility
to enable the storage ring operation with different FEL
wigglers, at various wiggler settings, and for different
electron beam energies. Since 2012, the storage ring has
demonstrated all designed characteristics in terms of
lattice flexibility and tuning. This work is aimed at
gaining better understanding of the real storage ring
lattice by performing a series of measurements of the
beta-functions along the storage ring. Unlike the LOCO
technique, the β-functions in the quadrupoles are directly
measured with good accuracy using a tune measurement system.
We will describe our experimental design and techniques, and
measurement procedures. We will also report our preliminary
results for the lattice characterization.},
Key = {fds320333}
}
@article{fds320334,
Author = {Wu, YK},
Title = {Light source and accelerator physics research program at
Duke university},
Journal = {6th International Particle Accelerator Conference, IPAC
2015},
Pages = {1866-1868},
Year = {2015},
Month = {January},
ISBN = {9783954501687},
Abstract = {The light source and accelerator physics research program at
Duke Free-Electron Laser Laboratory (DFELL), Triangle
Universities Nuclear Laboratory, is focused on the
development of the storage ring based free-electron lasers
(FELs), and an FEL driven state-of-the-art Compton gamma-ray
source, the High Intensity Gamma-ray Source (HIGS). With a
maximum total flux about 3 × 1010 γ/s and a spectral flux
of more than 103 γ/s/eV around 10 MeV, the HIGS is the
world's most intense Compton gamma-ray source. Operated in
the energy range from 1 to 100 MeV, the HIGS is a premier
Compton gamma-ray facility in the world for a variety of
nuclear physics research programs, both fundamental and
applied. In this paper, we will describe our ongoing
accelerator physics and light source development program in
the areas of the storage ring magnetic optics
characterization and compensation, FEL physics, and
development of gamma-ray beams in the higher energy range
(100 to 158 MeV).},
Key = {fds320334}
}
@article{fds320335,
Author = {Mikhailov, SF and Hao, H and Popov, VG and Wu, YK},
Title = {Developing an improved pulsed mode operation for Duke
storage ring based FEL},
Journal = {6th International Particle Accelerator Conference, IPAC
2015},
Pages = {1860-1862},
Year = {2015},
Month = {January},
ISBN = {9783954501687},
Abstract = {The Duke FEL and High Intensity Gamma-ray Source (HIGS)
facility is operated with an e-beam from 0.24 to 1.2 GeV and
a photon beam from 190 to 1060 nm. Currently, the energy
range of the gamma-ray beam is from 1 MeV to about 100 MeV,
with the maximum total gamma-ray flux about 3E10 gammas per
second around 10 MeV. The FEL is typically operated in
quasi-CW mode. Some HIGS user experiments can benefit
tremendously from a pulsed mode of FEL operation. For that
purpose, a fast steering magnet was developed years ago [1]
to modulate the FEL gain. This allows a build-up of a high
peak power FEL pulse from a well-damped electron beam.
However, the use of this gain modulator at low e-beam
energies can dramatically limit e-beam current due to beam
instability and poor injection. It also suffers from the
problem of a significantly reduced ebeam lifetime. To
overcome these shortcomings, we developed and successfully
tested an RF frequency modulation technique to pulse the FEL
beam. In this paper, we will describe this development, and
report our preliminary results of this improved pulsed FEL
operation.},
Key = {fds320335}
}
@article{fds320336,
Author = {Wallace, PW and Emamian, M and Hao, H and Mikhailov, SF and Popov, V and Wu, YK and Li, J},
Title = {Extending ok5 wiggler operational limit at duke fel/higs
facility},
Journal = {6th International Particle Accelerator Conference, IPAC
2015},
Pages = {1863-1865},
Year = {2015},
Month = {January},
ISBN = {9783954501687},
Abstract = {Since 2007 the HIGS facility has been operated to produce
both linearly and circularly polarized gamma-ray beams using
two FELs, the planar OK-4 FEL and helical OK-5 FEL.
Presently, with the OK-5 FEL operating at 192 nm, we can
produce circularly-polarized gamma-ray beams between 1 and
100 MeV for user applications. Gamma-ray production between
80 and 100 MeV required an extension of the OK-5 wiggler
operation beyond the designed current limit of 3.0 kA. In
2009, we upgraded cooling and machine protection systems to
successfully extend OK-5 operation to 3.5 kA. To realize
HIGS gamma-ray operation beyond 100 MeV and ultimately
toward 150 MeV (the pion-threshold energy), with various
limitations of the VUV mirror technology, the OK-5 wigglers
will need to be operated at an even higher current, between
3.6 and 4.0 kA. In this paper we present our technical
solution to further extend the operation range of the OK-5
wigglers, and report our preliminary results with
high-current wiggler operation.},
Key = {fds320336}
}
@article{fds320337,
Author = {Yan, J and Wu, YK and Mikhailov, S and Hao, H and Popov, V and Li, J and Wu,
J and Vinokurov, NA and Huang, S},
Title = {Experimental study of a two-color storage ring FEL
?},
Journal = {6th International Particle Accelerator Conference, IPAC
2015},
Pages = {1198-1200},
Year = {2015},
Month = {January},
ISBN = {9783954501687},
Abstract = {Multi-color Free-electron Lasers (FELs) have been developed
on linac based FELs over the past two decades. On the
storage ring, the optical klystron (OK) FEL in its early
days was demonstrated to produce lasing at two adjacent
wavelengths with their spectral separation limited by the
bandwidth of single wiggler radiation. Here, we report a
systematic experimental study on the two-color operation at
the Duke FEL facility, the first experimental demonstration
of a tunable two-color harmonic FEL operation of a storage
ring based FEL. We demonstrate a simultaneous generation of
two FEL wavelengths, one in infrared (IR) and the other in
ultraviolet (UV) with a harmonic relationship. The
experimental results show a good performance of the
two-color FEL operation in terms of two-color wavelength
tunability, power tunability and power stability.},
Key = {fds320337}
}
@article{fds320338,
Author = {Hao, H and Mikhailov, S and Popov, V and Wu, YK and Li,
J},
Title = {Characterizing betatron tune knobs at Duke storage
ring},
Journal = {6th International Particle Accelerator Conference, IPAC
2015},
Pages = {672-674},
Year = {2015},
Month = {January},
ISBN = {9783954501687},
Abstract = {A good control of the electron beam betatron tune is
critical for the operation of a storage ring. As the driver
for Duke free-electron lasers (FELs) and the High Intensity
Gammaray Source (HIGS), the Duke storage ring is operated in
a wide energy range (0.3 GeV - 1.2 GeV), with several
different electromagnetic wiggler configurations. This
creates the challenge of controlling the betatron tune in a
global manner. As the the first step, the feedforward tune
compensation schemes were designed and implemented to the
real-time computer control system to compensate the tune
change caused by the wiggler field. To further increase the
flexibility of the operation, a set of tune knob schemes are
designed for various wiggler configurations. The β function
changes caused by these knobs are constrained within the
south straight section where the tune knob is located,
minimizing the impact on the electron beam dynamics (i.e.
injection and lifetime). The tune and β function
measurements show a good agreement with the calculation. In
addition, it is found that some tune knob schemes are
effective for new wiggler configurations that are not
originally designed for.},
Key = {fds320338}
}
@article{fds249242,
Author = {Xu, W and Li, JY and Huang, SL and Wu, WZ and Hao, H and Wang, P and Wu,
YK},
Title = {Conditioning of BPM pickup signals for operations of the
Duke storage ring with a wide range of single-bunch
current},
Journal = {Chinese Physics C},
Volume = {38},
Number = {10},
Pages = {107003-107003},
Publisher = {IOP Publishing},
Year = {2014},
Month = {October},
ISSN = {1674-1137},
url = {http://dx.doi.org/10.1088/1674-1137/38/10/107003},
Abstract = {The Duke storage ring is a dedicated driver for the storage
ring based oscillator free-electron lasers (FELs), and the
High Intensity Gamma-ray Source (HIGS). It is operated with
a beam current ranging from about 1 mA to 100 mA per bunch
for various operations and accelerator physics studies. High
performance operations of the FEL and γ-ray source require
a stable electron beam orbit, which has been realized by the
global orbit feedback system. As a critical part of the
orbit feedback system, the electron beam position monitors
(BPMs) are required to be able to precisely measure the
electron beam orbit in a wide range of the single-bunch
current. However, the high peak voltage of the BPM pickups
associated with high single-bunch current degrades the
performance of the BPM electronics, and can potentially
damage the BPM electronics. A signal conditioning method
using low pass filters is developed to reduce the peak
voltage to protect the BPM electronics, and to make the BPMs
capable of working with a wide range of single-bunch
current. Simulations and electron beam based tests are
performed. The results show that the Duke storage ring BPM
system is capable of providing precise orbit measurements to
ensure highly stable FEL and HIGS operations.},
Doi = {10.1088/1674-1137/38/10/107003},
Key = {fds249242}
}
@article{fds249245,
Author = {Laskaris, G and Ye, Q and Lalremruata, B and Ye, QJ and Ahmed, MW and Averett, T and Deltuva, A and Dutta, D and Fonseca, AC and Gao, H and Golak, J and Huang, M and Karwowski, HJ and Mueller, JM and Myers, LS and Peng, C and Perdue, BA and Qian, X and Sauer, PU and Skibiński, R and Stave, S and Tompkins, JR and Weller, HR and Witała, H and Wu, YK and Zhang, Y and Zheng, W},
Title = {Spin-dependent cross sections from the three-body
photodisintegration of He 3 at incident energies of 12.8 and
14.7 MeV},
Journal = {Physical Review C - Nuclear Physics},
Volume = {89},
Number = {2},
Publisher = {American Physical Society (APS)},
Year = {2014},
Month = {February},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.89.024002},
Abstract = {The first measurement of the three-body photodisintegration
of polarized He3 using a circularly polarized photon beam
has been performed at incident energies of 12.8 and 14.7
MeV. This measurement was carried out at the high-intensity
γ-ray source located at Triangle Universities Nuclear
Laboratory. A high-pressure He3 target, polarized via spin
exchange optical pumping with alkali metals, was used in the
experiment. The spin-dependent double- and
single-differential cross sections from 3Heâ- (γâ-,n)pp
for laboratory angles varying from 30â̂̃ to 165â̂̃ are
presented and compared with state-of-the-art three-body
calculations. The data reveal the importance of including
the Coulomb interaction between protons in the three-body
calculations. © 2014 American Physical Society.},
Doi = {10.1103/PhysRevC.89.024002},
Key = {fds249245}
}
@article{fds249244,
Author = {Huang, S and Li, JY and Jia, B and Wu, YK},
Title = {Relative spectral response measurement of spectrometers
using undulator radiation},
Journal = {Journal of Instrumentation},
Volume = {9},
Number = {3},
Pages = {P03002-P03002},
Publisher = {IOP Publishing},
Year = {2014},
Month = {January},
url = {http://dx.doi.org/10.1088/1748-0221/9/03/P03002},
Abstract = {Undulator radiation with known spectral characteristics is
recognized as an excellent light source that can be used to
measure the spectral response of a variety of spectral
measurement devices in a wide range from infrared to x-ray.
This technique has been developed at Duke Free-Electron
Laser (FEL) Laboratory to successfully measure the spectral
response of several spectrometers in the near-infrared,
visible, and ultraviolet regions. In this paper, we present
both simulation and experimental results of the spectral
response measurement, with a focus on high-accuracy spectral
response reconstruction. Using simulation studies, we have
tested and confirmed the validity of the spectral response
measurement method while taking into account major sources
of errors. Especially, it shows that the spectral response
reconstruction technique developed in this work is rather
robust against the spectral broadening of undulator
radiation. The usefulness of this spectral response
measurement method is also confirmed with the experimental
study on a spectrometer in the visible region. Overall, we
have achieved good results with the measured spectral
response, with an RMS uncertainty of about 2.7% in the range
from 414 to 591 nm. Using multiple measurements, the
reproducibility of this method has also been tested with a
relative difference of about 2.3% (RMS in the range from 415
to 590 nm). For high-accuracy measurements of a broad
radiation spectrum, the knowledge of the spectral response
of the spectrometer is critical. In this paper, we will show
that the details of the measured undulator radiation spectra
can be properly restored by correcting the raw spectrum
using the measured spectral response. The method of spectral
response measurement using undulator radiation is also
useful to calibrate spectral devices in extreme spectral
ranges such as VUV and x-ray. © 2014 IOP Publishing Ltd and
Sissa Medialab srl.},
Doi = {10.1088/1748-0221/9/03/P03002},
Key = {fds249244}
}
@article{fds303764,
Author = {Leviner, LE and Aalseth, CE and Ahmed, MW and Avignone, FT and Back, HO and Barabash, AS and Boswell, M and De Braeckeleer and L and Brudanin, VB and Chan, YD and Egorov, VG and Elliott, SR and Gehman, VM and Hossbach, TW and Kephart, JD and Kidd, MF and Konovalov, SI and Lesko, KT and Li, J and Mei,
DM and Mikhailov, S and Miley, H and Radford, DC and Reeves, J and Sandukovsky, VG and Umatov, VI and Underwood, TA and Tornow, W and Wu,
YK and Young, AR},
Title = {A segmented, enriched N-type germanium detector for
neutrinoless double beta-decay experiments},
Journal = {Nuclear Instruments and Methods in Physics Research, Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {735},
Pages = {66-77},
Publisher = {Elsevier BV},
Year = {2014},
Month = {January},
url = {http://arxiv.org/abs/1304.5477v1},
Abstract = {We present data characterizing the performance of the first
segmented, N-type Ge detector, isotopically enriched to 85%
76Ge. This detector, based on the Ortec PT6×2 design and
referred to as SEGA (Segmented, Enriched Germanium
Assembly), was developed as a possible prototype for
neutrinoless double beta-decay measurements by the Majorana
collaboration. We present some of the general
characteristics (including bias potential, efficiency,
leakage current, and integral cross-talk) for this detector
in its temporary cryostat. We also present an analysis of
the resolution of the detector, and demonstrate that for all
but two segments there is at least one channel that reaches
the Majorana resolution goal below 4 keV FWHM at 2039 keV,
and all channels are below 4.5 keV FWHM. © 2013 Elsevier
B.V.},
Doi = {10.1016/j.nima.2013.08.081},
Key = {fds303764}
}
@article{fds249246,
Author = {Wu, YK},
Title = {Accelerator physics and light source research program at
duke university},
Journal = {IPAC 2013: Proceedings of the 4th International Particle
Accelerator Conference},
Pages = {264-266},
Year = {2013},
Month = {December},
Abstract = {The accelerator physics and light source research program at
the Duke Free-Electron Laser Laboratory, Triangle
Universities Nuclear Laboratory, is focused on the
development of the storage ring based free-electron lasers
(FELs), and a state-of-the-art Compton gamma-ray source, the
High Intensity Gamma-ray Source (HIGS). Driven by the
storage ring FEL, the HIGS is the world's most intense
Compton gamma-ray source with a maximum total flux of a few
1010 γ/s (around 10 MeV). Operated in the energy range from
1 to 100 MeV, the HIGS is a premier nuclear physics research
facility in the world. In 2012, we completed a major
accelerator upgrade project with the installation of a
wiggler switchyard system which allows changeovers between
two planar and two helical FEL wigglers in the middle of the
FEL section. In this paper, we report the light source R&D
activities related to the wiggler switchyard project and VUV
FEL lasing, and provide a summary of the accelerator physics
research program at the laboratory. Copyright © 2013 by
JACoW.},
Key = {fds249246}
}
@article{fds249247,
Author = {Hao, H and Mikhailov, SF and Li, J and Wu, YK},
Title = {Design of a soft orbit bump for FEL mirror protection at
duke FEL/HIGS facility},
Journal = {IPAC 2013: Proceedings of the 4th International Particle
Accelerator Conference},
Pages = {2006-2008},
Year = {2013},
Month = {December},
Abstract = {In an oscillator Free-Electron Laser (FEL) with a high
energy electron beam, it is critical to minimize harmful
high-energy radiation on the downstream FEL mirror in order
to increase its lifetime. At the High Intensity Gammaray
Source (HIGS) facility at Duke University, effort has been
devoted to developing a variety of techniques to reduce the
amount of radiation on the FEL mirror. One of the most
effective methods was the use of a set of adjustable
in-vacuum apertures to block harmonic radiation from FEL
wigglers. In recent studies, it was determined that the edge
radiation from the end-of-the-arc bending magnet is a main
source of EUV and soft x-ray radiation which causes mirror
damage. To mitigate this effect, a soft orbit bump is
designed to change the displacement and angle of the
electron beam around the end-of-the-arc area. This soft
orbit bump is developed using the multi-objective
optimization technique. Calculation shows the soft orbit
bump can significantly reduce the flux of high energy
photons on the FEL mirror. Study will be performed to
determine the impact of this orbit bump on the injection,
beam lifetime, and the FEL and gamma-ray operation at HIGS
facility. Copyright © 2013 by JACoW.},
Key = {fds249247}
}
@article{fds249248,
Author = {Mikhailov, SF and Hao, H and Li, JY and Popov, VG and Wallace, PW and Wu,
YK},
Title = {Protection of VUV FEL mirrors using soft orbit bump at duke
FEL / HIγS facility},
Journal = {IPAC 2013: Proceedings of the 4th International Particle
Accelerator Conference},
Pages = {1301-1303},
Year = {2013},
Month = {December},
Abstract = {The Duke FEL and High Intensity Gamma-ray Source (HIγS)
facility is operated with an electron beam from 0.24 to 1.2
GeV and a photon beam from 190 to 1060 nm. Presently, the
energy range of the gamma-beam is from 1 MeV to about 100
MeV, with the maximum total gamma-flux of more then
1010gammas per second around 10 MeV. Production of high
intensity, high energy gamma-beams of 60 to 100 MeV, using
UV-VUV mirrors of 240 to 190 nm, requires high energy, high
current electron beams of 0.9 to 1.05 GeV. Synchrotron
radiation damage to the FEL mirrors becomes crucial for VUV
FEL operation at or below 190 nm. The edge radiation (ER)
from the End-of-Arc (EOA) bending magnet, instead of the
radiation of FEL wigglers, is the dominant cause of rapid
degradation of the downstream FEL mirror. We describe here a
further development of the "soft" orbit bump concept to
significantly reduce the radiation exposure to the mirror
from the EOA dipole magnet. The bump uses designated "soft"
orbit correctors with magnetic field limited to produce
radiation with a critical wavelength close to or longer than
the FEL wavelength. A first experience of HIγS user runs
with 192 nm mirrors utilizing the soft bump is also
presented. Copyright © 2013 by JACoW.},
Key = {fds249248}
}
@article{fds249249,
Author = {Li, JY and Hao, H and Wu, WZ and Mikhailov, S and Popov, V and Wu,
YK},
Title = {Compensation schemes for operation of FEL wigglers on duke
storage ring},
Journal = {IPAC 2013: Proceedings of the 4th International Particle
Accelerator Conference},
Pages = {3270-3272},
Year = {2013},
Month = {December},
Abstract = {The Duke Free-electron laser is the photon driver for the
High Intensity Gamma-ray Source (HIGS). To extend the
capabilities of the FEL and HIGS to higher photon energy
regions, an FEL wiggler switchyard system was developed in
the recent years. This system was installed and commissioned
in 2012. The FEL wiggler switchyard is used to change
between two planar OK-4 wigglers and two helical OK-5
wigglers in the middle of the FEL straight section in a
short period of time (a few days). With a total number of
six electromagnetic wigglers, the Duke FEL can be operated
in a number of wiggler configurations and with a wide range
of magnetic fields. The operation of uncompensated FEL
wigglers can cause significant changes to the electron beam
closed orbit and magnetic lattice. To maintain sufficiently
large dynamic aperture for efficient injection and good beam
lifetime, a set of complex compensation schemes, including
wiggler magnetic field and lattice compensation, have been
developed for the operation of the FEL wigglers. This paper
reports the overall architecture and performance of the FEL
wiggler compensation schemes and their implementation in the
accelerator control system using the feed-forward
mechanism.},
Key = {fds249249}
}
@article{fds249250,
Author = {Wu, YK and Hao, H and Li, J and Mikhailov, S and Popov, V and Wu, WZ and Yan,
J and Emamian, M and Busch, M and Faircloth, J and Swift, G and Wallace, P and Wang, P},
Title = {Commissioning and operation of wiggler switchyard system for
duke FEL and HIGS},
Journal = {IPAC 2013: Proceedings of the 4th International Particle
Accelerator Conference},
Pages = {267-269},
Year = {2013},
Month = {December},
Abstract = {To enable the Duke storage ring FEL to operate in VUV with
adequate gain, a major storage ring upgrade was carried out
in 2012 to install two additional helical FEL wigglers with
a wiggler switchyard system. Using the switchyard, a quick
changeover can be made between two planar OK-4 wigglers and
two helical OK-5 wigglers in the middle of the FEL straight
section. This system preserves the linear polarization
capabilities of the Duke FEL and High Intensity Gamma-ray
Source (HIGS), while enabling VUV FEL operation with a
higher gain using a longer FEL with up to four helical
wigglers. The switchyard upgrade was completed in Summer
2012, followed by a rapid and successful commissioning of
the Duke storage ring, FEL system, and HIGS. In this paper,
we describe the development of the wiggler switchyard, its
installation and commissioning, and its impact on the
research program at the HIGS. Copyright © 2013 by
JACoW.},
Key = {fds249250}
}
@article{fds249263,
Author = {Laskaris, G and Ye, Q and Lalremruata, B and Ye, QJ and Ahmed, MW and Averett, T and Deltuva, A and Dutta, D and Fonseca, AC and Gao, H and Golak, J and Huang, M and Karwowski, HJ and Mueller, JM and Myers, LS and Peng, C and Perdue, BA and Qian, X and Sauer, PU and Skibiński, R and Stave, S and Tompkins, JR and Weller, HR and Witała, H and Wu, YK and Zhang, Y and Zheng, W},
Title = {First measurements of spin-dependent double-differential
cross sections and the Gerasimov-Drell-Hearn Integrand from
3He(γ,n)pp at incident photon energies of 12.8 and 14.7
MeV.},
Journal = {Physical review letters},
Volume = {110},
Number = {20},
Pages = {202501},
Year = {2013},
Month = {May},
ISSN = {0031-9007},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000319214800002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The first measurement of the three-body photodisintegration
of longitudinally polarized (3)He with a circularly
polarized γ-ray beam was carried out at the High Intensity
γ-ray Source facility located at Triangle Universities
Nuclear Laboratory. The spin-dependent double-differential
cross sections and the contributions from the three-body
photodisintegration to the (3)He Gerasimov-Drell-Hearn
integrand are presented and compared with state-of-the-art
three-body calculations at the incident photon energies of
12.8 and 14.7 MeV. The data reveal the importance of
including the Coulomb interaction between protons in
three-body calculations.},
Doi = {10.1103/physrevlett.110.202501},
Key = {fds249263}
}
@article{fds249264,
Author = {Zimmerman, WR and Ahmed, MW and Bromberger, B and Stave, SC and Breskin,
A and Dangendorf, V and Delbar, T and Gai, M and Henshaw, SS and Mueller,
JM and Sun, C and Tittelmeier, K and Weller, HR and Wu,
YK},
Title = {Unambiguous identification of the second 2+ state in 12C and
the structure of the Hoyle state.},
Journal = {Physical review letters},
Volume = {110},
Number = {15},
Pages = {152502},
Year = {2013},
Month = {April},
ISSN = {0031-9007},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000317459300008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The second J(π)=2+ state of 12C, predicted over 50 years
ago as an excitation of the Hoyle state, has been
unambiguously identified using the 12C(γ,α0)(8)Be
reaction. The alpha particles produced by the
photodisintegration of 12C were detected using an optical
time projection chamber. Data were collected at beam
energies between 9.1 and 10.7 MeV using the intense nearly
monoenergetic gamma-ray beams at the HIγS facility. The
measured angular distributions determine the cross section
and the E1-E2 relative phases as a function of energy
leading to an unambiguous identification of the second 2+
state in 12C at 10.03(11) MeV, with a total width of
800(130) keV and a ground state gamma-decay width of 60(10)
meV; B(E2:2(2)+→0(1)+)=0.73(13)e(2) fm(4) [or 0.45(8)
W.u.]. The Hoyle state and its rotational 2+ state that are
more extended than the ground state of 12C presents a
challenge and constraints for models attempting to reveal
the nature of three alpha-particle states in 12C.
Specifically, it challenges the ab initio lattice effective
field theory calculations that predict similar rms radii for
the ground state and the Hoyle state.},
Doi = {10.1103/physrevlett.110.152502},
Key = {fds249264}
}
@article{fds249243,
Author = {Omer, M and Negm, H and Zen, H and Hori, T and Kii, T and Masuda, K and Ohgaki, H and Hajima, R and Hayakawa, T and Dait, O and Shizuma, T and Fujiwara, M and Park, SH and Kikuzawa, N and Rusev, G and Tonchev, AP and Wu, YK},
Title = {Active interrogation of nuclear materials using LaBr3: Ce
detectors},
Journal = {Energy Procedia},
Volume = {34},
Pages = {50-56},
Publisher = {Elsevier BV},
Year = {2013},
Month = {January},
ISSN = {1876-6102},
url = {http://dx.doi.org/10.1016/j.egypro.2013.06.732},
Abstract = {Active interrogation in 235U was demonstrated with LaBr3:Ce
scintillation detectors using the nuclear resonance
fluorescence (NRF) technique. An NRF experiment was
performed at the High Intensity y-ray Source (HlyS) facility
using quasi-monochromatic circularly or linearly polarized
y-ray beams. Photons scattered at 90o relative to the
incident beam were detected with two different sizes of
cylindrical LaBr3:Ce detectors. Clear NRF peaks at 1733 and
1815 keV corresponding to de-excitations to the ground state
and/or low-lying levels in 235U were observed within 77
minutes of beam time even under the high background due to
the self-activity of LaBr3:Ce and the radioactive decay of
214Bi nuclei existing in the 235U target. The present study
shows a possibility of using LaBr3:Ce detector to perform
NRF experiments, promoting many options for inspection of
special nuclear materials. © 2013 The Authors. Published by
Elsevier B.V.},
Doi = {10.1016/j.egypro.2013.06.732},
Key = {fds249243}
}
@article{fds217448,
Author = {Stepan F. Mikhailov and Hao Hao and Jingyi Li and Victor Popov and Patrick Walter Wallace and Y.K. Wu},
Title = {`Protection of VUV FEL Mirrors using Soft Orbit Bump at Duke
FEL/HIGS facility},
Journal = {Proceedings of the 2013 International Particle Accelerator
Conference (IPAC'13), Shanghai, China, May 12 -- 17,
2013},
Pages = {1301 -- 1303},
Year = {2013},
Key = {fds217448}
}
@article{fds249255,
Author = {Popov, V and Mikhailov, S and Wallace, P and Wu, Y},
Title = {Cold cathode thyratron based high-voltage kicker generators
at the duke accelerators: Six year experience},
Journal = {IPAC 2012 - International Particle Accelerator Conference
2012},
Pages = {3698-3700},
Year = {2012},
Month = {December},
Abstract = {The performance of the Duke storage ring based light
sources, the Duke storage ring FEL and High Intensity
Gamma-ray Source (HIGS), has been greatly improved since
2007 as the result of operating a new full-energy, top-off
booster injector (0.18 - 1.2 GeV) [1], allowing fixed energy
operation of the storage ring (0.25 - 1.2 GeV). The
injection/extraction kicker system is one of the key
components of the accelerator facility which determines
efficiency and reliability of the light source operation.
Pseudo-Spark Switches (PSS), also known as cold cathode
thyratrons, are the critical components of the high voltage
pulse generators for kickers. More than six years of
operation has allowed us to study the lifetime issue for the
10 kA class devices. Recently, we have tested the next
generation cold cathode thyratron, with one installed in our
storage ring kicker high voltage generators. In the paper we
present preliminary test results for this new thyratron, and
the required modifications of its triggering driver, to
improve its performance. Copyright © 2012 by
IEEE.},
Key = {fds249255}
}
@article{fds249256,
Author = {Hao, H and Li, J and Wu, YK},
Title = {New storage ring lattice for the duke fel wiggler switchyard
system},
Journal = {IPAC 2012 - International Particle Accelerator Conference
2012},
Pages = {1272-1274},
Year = {2012},
Month = {December},
Abstract = {The Duke storage ring is a dedicated driver for the OK- 4
FEL and OK-5 FEL, and forthe state-of-the-art Compton
gamma-ray source, High Intensity Gamma-Ray Source (HIGS).
Toproduce FEL lasing below 190 nm and gammaray beams above
100 MeV, the FEL system needs tobe upgraded to increase the
FEL gain by adding two more helical OK-5 wigglers to form
afour-wiggler FEL. To preserve the linear polarization
capability of the gamma-ray beamproduced by the planar OK-4
FEL, a wiggler switchyard system is under development
whichwill enable the switch between two planar OK-4 wigglers
and two helical OK-5 wigglers inthe middle of the FEL
straight. In this work, we present the new magnetic lattice
designedfor the operation of the wiggler switchyard system.
This new lattice is developed withgreat flexibility for the
operation with different numbers of FEL wigglers,
variablebetatron tunes, and adjustable electron beam sizes
at the collision point for the HIGS. Inaddition, the new
lattice is developed for the operation in a wide range of
energies, from240 MeV to 1.2 GeV, with proper nonlinear
dynamics compensations in order to realize alarge dynamic
aperture. Copyright © 2012 by IEEE.},
Key = {fds249256}
}
@article{fds249257,
Author = {Mikhailov, SF and Li, JY and Popov, VG and Wallace, PW and Wu,
YK},
Title = {Soft orbit bump for duke storage ring VUV FEL
operation},
Journal = {IPAC 2012 - International Particle Accelerator Conference
2012},
Pages = {1774-1776},
Year = {2012},
Month = {December},
Abstract = {The Duke FEL and High Intensity Gamma-ray Source (HIS)
facility is operated with anelectron beam from 0.24 to 1.2
GeV and an FEL photon beam from 190 to 1060 nm. The
energyrange of the gamma-ray beam is from 1 MeV to about 100
MeV, with the maximum totalgamma-flux of more then 1010
gammas per second around 10 MeV. Production of
thehigh-intensity, high energy gamma-beams of 60-158 MeV
using UV-VUV mirrors of 250 - 150 nmrequires high current
and high energy electron beams (0.9-1.20 GeV). Radiation
damage tothe downstream FEL mirror becomes more severe for
VUV FEL operation at 190 nm and below. Atthese VUV
wavelengths with GeV electrons, the radiation from the
end-of-arc (EOA) bendingmagnets, instead of the radiation
from helical FEL wigglers, is the dominant cause of arapid
degradation of the downstream mirror. In this work, we
propose a concept of a"soft" orbit bump using designated
orbit correctors to significantly reduce theradiation from
the EOA dipole toward the FEL mirror. The strength of
magnetic field ofthese correctors is limited to produce a
radiation with a critical wavelength close orbelow the FEL
wavelength. Copyright © 2012 by IEEE.},
Key = {fds249257}
}
@article{fds249258,
Author = {Xu, W and He, D and Wu, WZ and Li, J and Wu, YK},
Title = {Electron beam diagnostics based on transverse feedback
system at duke storage ring},
Journal = {IPAC 2012 - International Particle Accelerator Conference
2012},
Pages = {849-851},
Year = {2012},
Month = {December},
Abstract = {To combat electron beam instabilities, a field programmable
gate array (FPGA) based bunch-by-bunch transverse feedback
(TFB) has been developed for the Duke storage ring. While it
is capable of suppressing transverse beam instabilities for
multi-bunch operation, the TFB system has not been needed
for typical operation of the Duke storage ring FEL. To
explore the great potential of this system, we have focused
on the development of TFB based beam diagnostics. A TFB
based tune measurement system has been developed using two
methods: the tune scan method and tune monitoring method.
With the tune monitoring method, a much faster method of the
two, we have studied the tune stability of the electron beam
in the Duke storage ring. This tune measurement system also
allows us to conduct chromaticity measurements more quickly,
compared with the existing chromaticity measurement system
using a network analyzer. Finally, the TFB based tune system
has been used to calibrate the tune knob and chromaticity
knob for the Duke storage ring. Copyright © 2012 by
IEEE.},
Key = {fds249258}
}
@article{fds249262,
Author = {Omer, M and Negm, H and Zen, H and Hori, T and Kii, T and Masuda, K and Ohgaki, H and Hajima, R and Hayakawa, T and Daito, I and Shizuma, T and Fujiwara, M and Park, SH and Kikuzawa, N and Rusev, G and Tonchev, AP and Wu, YK},
Title = {Detection of photon-induced excitations in 235U
with LaBr 3:Ce scintillating detectors},
Journal = {IEEE Nuclear Science Symposium Conference
Record},
Pages = {55-58},
Publisher = {IEEE},
Year = {2012},
Month = {December},
ISSN = {1095-7863},
url = {http://dx.doi.org/10.1109/NSSMIC.2012.6551059},
Abstract = {Excitations in 235U were measured with LaBr3:Ce
scintillation detectors using the nuclear resonance
fluorescence (NRF) technique. A NRF experiment was performed
at the High Intensity γ-ray Source (HIγS) facility using
quasi-monochromatic circularly or linearly polarized γ-ray
beams. Photons scattered at 90°relative to the incident
beam were detected with two different sizes of cylindrical
LaBr 3:Ce detectors. Clear NRF peaks at 1733 and 1815 keV
corresponding to de-excitations to the ground state and/or
low-lying levels in 235U were observed within 77 minutes of
beam time even under the high background due to the
self-activity of LaBr3:Ce and the radioactive decay of 214Bi
nuclei existing in the 235U target. The present study shows
a possibility of using LaBr3:Ce detector to perform NRF
experiments, promoting many options for inspection of
special nuclear materials. © 2012 IEEE.},
Doi = {10.1109/NSSMIC.2012.6551059},
Key = {fds249262}
}
@article{fds249337,
Author = {Wei, X and Wu, WZ and Li, JY and Due-Hui, H and Wu, YK},
Title = {Betatron Tune Measurement System Based on Bunch-by-bunch
Transverse Feedback at Duke Storage Ring},
Journal = {Chinese Phys. C},
Volume = {37},
Number = {7},
Pages = {077006},
Year = {2012},
url = {http://dx.doi.org/10.1088/1674-1137/37/7/077006},
Abstract = {To combat electron beam instabilities, a digital
bunch-by-bunch transverse feedback (TFB) system has been
developed for the Duke storage ring. While it is capable of
suppressing transverse beam instabilities for multibunch
operation, the TFB system has not been needed for typical
operation of the Duke storage ring. To explore the great
potential of this system, we have developed beam diagnostic
techniques using the TFB, in particular, the TFB based tune
measurement techniques. The tune measurement technique
allows us to conduct fast chromaticity measurements,
compared with the existing chromaticity measurement system
using a network analyzer. This new tune measurement system
also enables us to measure the bunch tune for multibunch
operation of the Duke storage ring. With the TFB based tune
measurement system, we have studied the tune stability of
the electron beam in the Duke storage ring. This tune system
has also been used to calibrate the tune knob for the Duke
storage ring. ©2013 Chinese Physical Society and the
Institute of High Energy Physics of the Chinese Academy of
Sciences and the Institute of Modern Physics of the Chinese
Academy of Sciences and IOP Publishing Ltd.},
Doi = {10.1088/1674-1137/37/7/077006},
Key = {fds249337}
}
@article{fds249338,
Author = {Wei, X and Wu, WZ and Due-Hui, H and Wu, YK},
Title = {Design and Optimization of Longitudinal Feedback Kicker
Cavity for HLS-II Storage Ring},
Journal = {Chinese Phys. C},
Volume = {37},
Number = {3},
Pages = {037003-037003},
Publisher = {IOP Publishing},
Year = {2012},
url = {http://dx.doi.org/10.1088/1674-1137/37/3/037003},
Abstract = {In the Hefei Light Source (HLS) storage ring, multibunch
operation is used to obtain a high luminosity. Multibunch
instabilities can severely limit light source performance
with a variety of negative impacts, including beam loss, low
injection efficiency, and overall degradation of the beam
quality. Instabilities of a multibunch beam can be mitigated
using certain techniques including increasing natural
damping (operating at a higher energy), lowering the beam
current, and increasing Landau damping. However, these
methods are not adequate to stabilize a multibunch electron
beam at a low energy and with a high current. In order to
combat beam instabilities in the HLS storage ring, active
feedback systems including a longitudinal feedback system
(LFB) and a transverse feedback system (TFB) will be
developed as part of the HLS upgrade project, the HLS- II
storage ring project. As a key component of the longitudinal
bunch-by-bunch feedback system, an LFB kicker cavity with a
wide bandwidth and high shunt impedance is required. In this
paper we report our work on the design of the LFB kicker
cavity for the HLS- II storage ring and present the new
tuning and optimization techniques developed in designing
this high performance LFB kicker. © 2013 Chinese Physical
Society and the Institute of High Energy Physics of the
Chinese Academy of Sciences and the Institute of Modern
Physics of the Chinese Academy of Sciences and IOP
Publishing Ltd.},
Doi = {10.1088/1674-1137/37/3/037003},
Key = {fds249338}
}
@article{fds191675,
Author = {W. Xu and D. He and W. Z.Wu and Y. K. Wu},
Title = {Design of Longitudinal Feedback Kicker for HLS Storage
Ring},
Journal = {Proceedings of the 2011 Particle Accelerator Conference
(PAC'11)},
Pages = {612 -- 614},
Year = {2011},
Month = {March},
Key = {fds191675}
}
@article{fds191676,
Author = {Y. K. Wu and J. Y. Li and S. F. Mikhailov and V. G. Popov and G. Swift and P. Wallace and W. Z. Wu and S. Huang},
Title = {A VUV FEL for Producing 70 -- 100 MeV Circularly Polarized
Compton Gamma-ray Beams},
Journal = {Proceedings of the 2011 Particle Accelerator Conference
(PAC'11)},
Pages = {778 -- 780},
Year = {2011},
Month = {March},
Key = {fds191676}
}
@article{fds191677,
Author = {S. Huang and B. Jia and J. Y. Li and Y. K. Wu},
Title = {Calibration of Spectrometers with Undulator
Radiation},
Journal = {Proceedings of the 2011 Particle Accelerator Conference
(PAC'11)},
Pages = {2402 -- 2404},
Year = {2011},
Month = {March},
Key = {fds191677}
}
@article{fds191678,
Author = {J. Y. Li and B. Jia and S. F. Mikhailov and V. Popov and Y. K. Wu and S.
Huang},
Title = {Manipulating the FEL gain process with an In-cavity Aperture
Syste},
Journal = {Proceedings of the 2011 Particle Accelerator Conference
(PAC'11)},
Pages = {2405 -- 2407},
Year = {2011},
Month = {March},
Key = {fds191678}
}
@article{fds191679,
Author = {S. F. Mikhailov and J. Y. Li and V. Popov and Y. K.
Wu},
Title = {Experience of FEL Mirror Degradation at the Duke FEL and
HIGS Facility},
Journal = {Proceedings of the 2011 Particle Accelerator Conference
(PAC'11)},
Pages = {2489 -- 2491},
Year = {2011},
Month = {March},
Key = {fds191679}
}
@article{fds191680,
Author = {V. Popov and J. Y. Li and S. F. Mikhailov and P. Wallace and P. Wang and Y.
K. Wu},
Title = {Upgrade of the RF Photo-Injector for the Duke Storage
Ring},
Journal = {Proceedings of the 2011 Particle Accelerator Conference
(PAC'11)},
Pages = {2408 -- 2410},
Year = {2011},
Month = {March},
Key = {fds191680}
}
@article{fds249328,
Author = {Wu, WZ and Kim, Y and Li, JY and Teytelman, D and Busch, M and Wang, P and Swift, G and Park, IS and Ko, IS and Wu, YK},
Title = {Development of a bunch-by-bunch longitudinal feedback system
with a wide dynamic range for the HIGS facility},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {632},
Number = {1},
Pages = {32-42},
Publisher = {Elsevier BV},
Year = {2011},
Month = {March},
ISSN = {0168-9002},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000288049000005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {Electron beam coupled-bunch instabilities can limit and
degrade the performance of storage ring based light sources.
A longitudinal feedback system has been developed for the
Duke storage ring to suppress multi-bunch beam instabilities
which prevent stable, high-current operation of the storage
ring based free-electron lasers (FELs) and an FEL driven
Compton gamma source, the high intensity gamma-ray source
(HIGS) at Duke University. In this work, we report the
development of a state-of-the-art second generation
longitudinal feedback system which employs a field
programmable gate array (FPGA) based processor, and a
broadband, high shunt-impedance kicker cavity. With two
inputs and two outputs, the kicker cavity was designed with
a resonant frequency of 937 MHz, a bandwidth of 97 MHz, and
a shunt impedance of 1530Ω. We also developed an S-matrix
based technique to fully characterize the performance of the
kicker cavity in the cold test. This longitudinal feedback
system has been commissioned and optimized to stabilize
high-current electron beams with a wide range of electron
beam energies (250 MeV to 1.15 GeV) and a number of electron
beam bunch modes, including the single-bunch mode and all
possible symmetric bunch modes. This feedback system has
become a critical instrument to ensure stable, high-flux
operation of HIGS to produce nearly monochromatic, highly
polarized Compton gamma-ray beams. © 2010 Elsevier B.V. All
rights reserved.},
Doi = {10.1016/j.nima.2010.12.077},
Key = {fds249328}
}
@article{fds249360,
Author = {Sun, C and Wu, YK},
Title = {Theoretical and simulation studies of characteristics of a
Compton light source},
Journal = {Phys. Rev. ST Accel. Beams},
Volume = {14},
Number = {4},
Pages = {044701},
Publisher = {American Physical Society (APS)},
Year = {2011},
ISSN = {1098-4402},
url = {http://dx.doi.org/10.1103/PhysRevSTAB.14.044701},
Abstract = {Compton scattering of a laser beam with a relativistic
electron beam has been used to generate intense, highly
polarized and nearly monoenergetic x-ray or gamma-ray beams
at many facilities. The ability to predict the spatial,
spectral, and temporal characteristics of a Compton
gamma-ray beam is crucial for the optimization of the
operation of a Compton light source as well as for the
applications utilizing the Compton beam. In this paper, we
present two approaches, one based upon analytical
calculations and the other based upon Monte Carlo
simulations, to study the Compton scattering process for
various electron and laser-beam parameters as well as
different gamma-beam collimation conditions. These
approaches have been successfully applied to characterize
Compton gamma-ray beams, after being benchmarked against
experimental results at the High Intensity Gamma-ray Source
(HIγS) facility at Duke University.},
Doi = {10.1103/PhysRevSTAB.14.044701},
Key = {fds249360}
}
@article{fds249361,
Author = {Quarati, FGA and Owens, A and Dorenbos, P and deHaas, JTM and Benzoni,
G and Blasi, N and Boiano, C and Brambilla, S and Camera, F and Alba, R and Bellia, G and Maiolino, C and Santonocito, D and Ahmed, M and Brown, N and Stave, S and Weller, HR and Wu, YK},
Title = {High energy gamma-ray spectroscopy with LaBr3 scintillation
detectors},
Journal = {Nucl. Instr. Methods A},
Volume = {629},
Number = {1},
Pages = {157-169},
Publisher = {Elsevier BV},
Year = {2011},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2010.11.035},
Abstract = {Lanthanum bromide scintillation detectors produce very high
light outputs (˜60,000 ph/MeV) within a very short decay
time (typically ˜20 ns) which means that high instantaneous
currents can be generated in the photocathode and dynode
chain of the photomultiplier tube (PMT) used for the
scintillation readout. The net result is that signal
saturation can occur long before the recommended PMT biasing
conditions can be reached.In search of an optimized light
readout system for LaBr3, we have tested and compared two
different PMT configurations for detection of gamma-rays up
to 15 MeV. This range was chosen as being appropriate for
gamma-ray remote sensing and medium energy nuclear physics
applications. The experiments were conducted at two
facilities: the Laboratori Nazionali del Sud (LNS) in
Catania, Italy [1] and the High Intensity Gamma-ray Source
(HIγS) at Triangle University Nuclear Laboratory, in
Durham, North Carolina, USA [2].The PMT configurations we
have tested are (1) a standard dynode chain operated
under-biased; (2) a 4-stage reduced chain operated at
nominal inter-dynode bias.The results are that shortening
the number of active stages, as in configuration (2), has
advantages in preserving energy resolution and avoiding PMT
saturation over a large energy range.However, the use of an
under-biased PMT, configuration (1), can still be considered
a satisfactory solution, at least in the case of PMTs
manufactured by Photonis.The results of this study will be
used in support of the Mercury Gamma-ray and Neutron
Spectrometer (MGNS) on board of BepiColombo, the joint
ESA/JAXA mission to Mercury, scheduled for launch in
2014.},
Doi = {10.1016/j.nima.2010.11.035},
Key = {fds249361}
}
@article{fds249251,
Author = {Wu, YK},
Title = {Accelerator physics research and light source development at
Duke University},
Journal = {IPAC 2010 - 1st International Particle Accelerator
Conference},
Pages = {2648-2650},
Year = {2010},
Month = {December},
Abstract = {The accelerator physics and light source development
programs at the Duke Free-Electron Laser Laboratory (DFELL)
focus on beam dynamics research, beam instability studies,
FEL research, and the development of storage ring based
free-electron lasers (FELs) and Compton gamma-ray sources.
The High Intensity Gamma-ray Source (HIγS) at Duke
University is the highest flux Compton gamma-ray source
currently available with an energy tuning range from 1 to
100 MeV. In this paper, we will report our recent progress
in accelerator physics research and light source development
to meet challenges of today's and future
accelerators.},
Key = {fds249251}
}
@article{fds249252,
Author = {Sun, C and Wu, YK},
Title = {A semi-analytical algorithm for modelling Compton gamma-ray
beams},
Journal = {IPAC 2010 - 1st International Particle Accelerator
Conference},
Pages = {265-267},
Year = {2010},
Month = {December},
Abstract = {Compton scattering of a laser beam with a relativistic
electron beam has been used to generate an intense, highly
polarized, and nearly monoenergetic gamma-ray beam at
several facilities. The ability of predicting the spatial
and spectral distributions of a Compton gamma-ray beam is
crucial for the optimization of the operation of a Comp-ton
light source as well as for the applications utilizing the
Compton beam. In this paper, we present an analytical
algorithm for modelling Compton scattering process. Based
upon this algorithm, we developed a numerical integration
code to produce smooth results for the spatial and spectral
distributions of the Compton beam. This code has been used
to characterize the High Intensity Gamma-ray Source (HIγS)
at Duke University for varying electron and laser beam
parameters as well as different gamma-ray beam col-limation
conditions.},
Key = {fds249252}
}
@article{fds249253,
Author = {Mikhailov, SF and Popov, VG and Li, J and Wu, YK},
Title = {Study of FEL mirror degradation at the DUKE FEL and higs
facility},
Journal = {IPAC 2010 - 1st International Particle Accelerator
Conference},
Pages = {2275-2277},
Year = {2010},
Month = {December},
Abstract = {The Duke FEL and High Intensity Gamma-ray Source (HIγS) are
operated with a wide range of electron beam energies
(0.24-1.2 GeV) and photon beam wavelengths (190-1060 nm).
Currently, the HIγS user operation is carried out in the
gamma-beam energy range from 1 to about 65 MeV, with a
near-future extension to about 100 MeV using 190 nm FEL
mirrors. The maximum total gamma-flux produced at the HIγS
facility is up to 1010 gammas per second around 10 MeV.
Production of this high level gamma-ray flux requires a very
high average FEL photon beam power inside the FEL resonator
at one kilowatt or more. The high power FEL operation can
cause significant degradation of the FEL mirrors due to
higher-order wiggler harmonic radiation, especially when
operating the FEL in the UV region at a high electron beam
energy. This has limited the high-energy, high-flux HIγS
gamma-beam operation mostly to circular polarization when UV
mirrors are used, as higher-order harmonic radiation of
helical wigglers is peaked off-axis. To ensure the
predictability and stability of the HIγS operation for user
research program, we have developed a comprehensive program
to continuously monitor the performance of the FEL mirrors.
This program has enabled us to use a particular set of FEL
mirrors for a few hundreds hours of high gamma-flux
operation with predictable performance. In this work, we
discuss sources and consequences of the mirror degradation
for a variety of wavelengths.},
Key = {fds249253}
}
@article{fds249254,
Author = {Sun, C and Li, J and Wu, WZ and Mikhailov, SF and Popov, VG and Wu, YK and Zhang, J and Xu, HL and Chao, AW},
Title = {Electron beam polarization measurement using touschek
lifetime technique},
Journal = {IPAC 2010 - 1st International Particle Accelerator
Conference},
Pages = {262-264},
Year = {2010},
Month = {December},
Abstract = {Electron beam loss due to intra-beam scattering, the
Tou-schek effect, in a storage ring depends on the electron
beam polarization. The polarization of an electron beam can
be determined from the difference in the Touschek lifetime
compared with an unpolarized beam. In this paper, we report
on a systematic experimental procedure recently developed at
Duke FEL laboratory to study the radiative polarization of a
stored electron beam. Using this technique, we have
successfully observed the radiative polarization build-up of
an electron beam in the Duke storage ring, and determined
the equilibrium degree of polarization and the time constant
of the polarization build-up process.},
Key = {fds249254}
}
@article{fds249373,
Author = {Jia, B and Li, J and Huang, S and Schmidler, SC and Wu,
YK},
Title = {Electron beam energy spread measurements using optical
klystron radiation},
Journal = {Physical Review Special Topics - Accelerators and
Beams},
Volume = {13},
Number = {8},
Pages = {080702},
Publisher = {American Physical Society (APS)},
Year = {2010},
Month = {August},
ISSN = {1098-4402},
url = {http://hdl.handle.net/10161/4310 Duke open
access},
Abstract = {http://prst-ab.aps.org/abstract/PRSTAB/v13/i8/e080702},
Doi = {10.1103/physrevstab.13.080702},
Key = {fds249373}
}
@article{fds249371,
Author = {Jia, B and Wu, YK and Bisognano, JJ and Chao, AW and Wu,
J},
Title = {Influence of an imperfect energy profile on a seeded free
electron laser performance,},
Journal = {Phys. Rev. ST Accel. Beams},
Volume = {13},
Number = {13},
Pages = {060701},
Publisher = {American Physical Society (APS)},
Year = {2010},
ISSN = {1098-4402},
url = {http://hdl.handle.net/10161/4309 Duke open
access},
Abstract = {http://prst-ab.aps.org/abstract/PRSTAB/v13/i6/e060701},
Doi = {10.1103/PhysRevSTAB.13.060701},
Key = {fds249371}
}
@article{fds249372,
Author = {Sun, C and Zhang, J and Li, J and Wu, WZ and Mikhailov, SF and Popov, VG and Xu, HL and Chao, AW and Wu, YK},
Title = {Polarization measurement of stored electron beam using
Touschek lifetime},
Journal = {Nucl. Instr. Methods A},
Volume = {614},
Number = {3},
Pages = {339-344},
Publisher = {Elsevier BV},
Year = {2010},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2010.01.034},
Abstract = {Touschek lifetime of an electron beam in a storage ring
depends on the beam polarization through the intrabeam
scattering effect. Therefore, the electron beam polarization
can be determined from the Touschek lifetime measurement. In
this paper, we report on a systematic experimental procedure
we developed to study the radiative polarization of a stored
electron beam. Using this technique, we successfully
observed the radiative polarization of an electron beam in
the Duke storage ring, and determined the equilibrium degree
of polarization and the time constant of the polarization
build-up process.},
Doi = {10.1016/j.nima.2010.01.034},
Key = {fds249372}
}
@article{fds249327,
Author = {Sun, C and Wu, YK},
Title = {A 4D Monte Carlo Compton scattering code},
Journal = {IEEE Nuclear Science Symposium Conference
Record},
Pages = {477-480},
Publisher = {IEEE},
Year = {2009},
Month = {December},
ISSN = {1095-7863},
url = {http://dx.doi.org/10.1109/NSSMIC.2009.5401609},
Abstract = {Compton scattering of a laser beam and an electron beam in
an accelerator has been used to generate an x-ray or
gamma-ray beam at many facilities. To study the spatial,
spectral and temporal characteristics of the Compton
gamma-ray beam, we developed a 4-dimensional (3D space plus
time) Monte Carlo computer simulation code (MCCMPT) to model
the Compton scattering process. This code has been
benchmarked against the measurement results at the High
Intensity Gamma-ray Source (HIγS) facility at Duke
University. ©2009 IEEE.},
Doi = {10.1109/NSSMIC.2009.5401609},
Key = {fds249327}
}
@article{fds191672,
Author = {S. Huang and J. Y. Li and Y. K. Wu},
Title = {Experiments on Madey Theorem with Optical Klystron
Free-Electron Laser},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1244-1246},
Year = {2009},
Abstract = {The Madey theorem is a valuable research tool for
studying Free-Electron Lasers (FELs). The theorem
relates the shape of the on-axis spontaneous
radiation spectrum of FEL wigglers to the FEL
gain. The theorem predicts that degradation of the
spontaneous spectrum, for example as a result of
the increase of the electron beam energy spread,
provides a direct measure of the reduction of the
FEL gain. Extensive experiments have been
performed to study the validity of the Madey
theorem for a storage ring base optical klystron
FEL. The experimental data show that the lasing
wavelength of the FEL is very close to the maximum
slope of spontaneous spectra as predicted by the
Madey theorem with a relative wavelength
discrepancy less than 0.2%. Further analysis is
underway to understand this wavelength
difference. In addition, we have performed
direct measurements of the start up gain of the FEL
and compared it with the changing slope of the
spontaneous spectra. The preliminary results
show a good agreement between the measured FEL gain
and the prediction by Madey theorem.},
Key = {fds191672}
}
@article{fds191673,
Author = {Y. K. Wu},
Title = {Accelerator Physics Research and Development Programs at
Duke University},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1245-1247},
Year = {2009},
Abstract = {The Duke Free-Electron Laser Laboratory (DFELL)
operates several accelerators as a driver
for storage ring based Free-Electron Lasers (FELs) and
Compton gamma-ray source, the High Intensity
Gamma-ray Source (HIGS). The HIGS is the most powerful
Compton gamma-ray source in the world below 100 MeV.
Since completing a major upgrade of the HIGS in 2007,
the Duke storage ring FEL and HIGS gamma source have been
operated extensively for user research
programs. In 2008, the DFELL was merged with the
Triangle Universities Nuclear
Laboratory (TUNL) to become a major
accelerator facility of the TUNL. The
accelerator physics program at the DFELL covers
a wide range of activities, from nonlinear
dynamics research, to the study of beam
instability with advanced feedback systems, to
light source research and development, in
particular, the FEL research and Compton light
source development. In this paper, we will report
our recent progress in accelerator physics
research and light source development to meet new
challenges of today's and future accelerators.},
Key = {fds191673}
}
@article{fds167635,
Author = {Y. K. Wu},
Title = {Storage Ring Compton Gamma-ray Source},
Journal = {ICFA Beam Dynamics Newsletter},
Volume = {50},
Editor = {W. Chou},
Year = {2009},
Key = {fds167635}
}
@article{fds167637,
Author = {Y. K. Wu and M. Busch and M. Emamian and J. Faircloth and S. Hartman and C.
Howell, J. Li and S. Mikhailov and V. Popov and G. Swift and P. Wallace and P. Wang},
Title = {Performance and Capabilities of Upgraded High Intensity
Gamma-ray Source at Duke University},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {3181-3183},
Year = {2009},
Abstract = {Since 2008, the upgraded High Intensity
Gamma-ray Source (HIGS) at the Duke FEL Lab has
provided users with gamma beams of unprecedented
quality for scientific research. The
recently completed accelerator upgrades
include a HOM-damped RF cavity, a full-energy
top-off booster injector, redesigned storage ring
straight sections, and two new FELs. The HIGS
facility is now capable of producing a high
intensity gamma beam in a wide energy range (1 -
100 MeV) using commercial FEL mirrors. It has achieved
an exceptionally high flux, up to ~1010 g/s total (<
20 MeV), making it the world's most powerful Compton
gamma source. It produces almost 100% polarized
gammas, either linear or circular. At the HIGS,
the gamma energy can be changed rapidly within a
factor of three in minutes. Operated by
Triangle Universities Nuclear
Laboratory since summer 2008, the HIGS is a
dedicated Compton gamma source, capable of
producing more than 2,000 h of gamma beam time per year
with a five-day, two-shift schedule. Future
development at the HIGS includes higher energy
gamma beams toward the pion threshold and a rapid switch
of circular polarization.},
Key = {fds167637}
}
@article{fds167638,
Author = {Stepan. F. Mikhailov and Jngyi Li and Victor Popov and Patrick W.
Wallace and Ping Wang and Ying K. Wu and Oleg Anchugov},
Title = {Multibunch injection scheme for the Duke booster synchrotron
for top-off injection},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1238-1240},
Year = {2009},
Abstract = {A booster-injector synchrotron has been recently
built and commissioned at Duke University to
provide for the top-off injection into the storage
ring in the energy range of 0.24 - 1.2 GeV. Booster
injection kicker was designed with a pulse length of
18 out of 19 booster separatrixes, assuming a
long train of electron bunches to be injected from
the existing linac. Such scheme required a major linac
upgrade from single bunch photo emission mode to a
multibunch thermionic mode. A major disadvantage
of the latter was much higher radiation levels
in the facility. Since commissioning, the
booster could only operate with one or two bunches
limited by both long kicker pulse and single bunch
injection from the linac. The consequent
limitation of the injection rate restricted
the capability of production of the Compton
gamma rays in the loss mode, i.e. production of gammas
with energy above 20-25 MeV, to about 5*108 photons
per sec. Update of the linac for the repetition rate
of up to 10 Hz, and modification of the
injection kicker for 15 nS pulse length allowed us
to developed an alternative multibunch
injection scheme with a significant increase of
the injection rate into storage ring.},
Key = {fds167638}
}
@article{fds167639,
Author = {Stepan F. Mikhailov and Jingyi Li and Victor Popov and Ying K.
Wu},
Title = {Pass-by-pass multistage FEL gain measurement technique for a
storage ring FEL},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1241-1243},
Year = {2009},
Abstract = {The paper presents a novel technique of measuring
the gain of a storage ring based FEL oscillator. As
opposed to the conventional technique of
measuring the FEL gain from its macro-pulse
envelope, this new technique is based upon the
measurement of pass-by-pass FELμpulses. To record the
growth of the optical energy in the FEL
micro-pulse train, we use fast photo-diodes and
photo-multiplier tubes (PMTs). PMTs are usually
employed at the very beginning of the FEL lasing
development, while the photodiodes are used at
the latter stages when the FEL power is fully
developed and saturated. This new gain
measurement technique provides a powerful tool
to study the details of the FEL gain process starting
from spontaneous radiation to saturation. It
allows us to investigate five to seven orders of
magnitude of the FEL energy growth. As fast
photo-detectors with a sub-nanosecond time
response become available, this new technique can be
adopted for many oscillator FELs, including
those driven by super-conducting linacs. Special
attention is paid to the dynamic non-linearity
issues of the photodiodes and PMTs
associated with short length of FEL
pulses.},
Key = {fds167639}
}
@article{fds167640,
Author = {H. Hao and X. Q. Wang and Y. K. Wu},
Title = {Nonlinear Dynamics Study of Storage Ring with Super
Periods},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1904-1906},
Year = {2009},
Abstract = {Many modern light source storage rings use a basic
magnetic lattice structure consisting of a
number of repetitive periodic lattice block,
the super periods. The study of one super-period
can reveal the dynamical proprieties of the
storage ring. Unlike the traditional approach of
studying the one-turn map of the storage ring, the work
focuses on the study of a super-period lattice,
which allows us to gain new insight into the storage
ring dynamics using a simpler magnetic
structure. In this paper, both analytical and
numerical techniques, including Lie Algebra
and Normal Form, and particle tracking and
frequency analysis, are used to study the
nonlinear dynamics of one super-period of a
standard double-bend achromat (DBA) and triple-bend
achromat (TBA) with two or more nonlinear elements
(e.g. sextupoles). The relationship between the
super-period dynamics and storage ring
dynamics is explored in terms of the global
lattice tuning and local lattice selection for
straight sections.},
Key = {fds167640}
}
@article{fds167641,
Author = {W. Z. Wu and Y. Kim and J. Li and Ping Wang and Matthew Busch and Gary
Swift, Ying K. Wu and Dmitry Teytelman and In-Soo Park and In Soo
Ko},
Title = {Development and commissioning of bunch-by-bunch longitudinal
feedback system for Duke storage ring},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {4117-4119},
Year = {2009},
Abstract = {The coupled bunch mode instabilities (CBMIs)
caused by vacuum chamber impedance limit and degrade
the performance of the storage ring based light
sources. A bunch-by-bunch longitudinal feedback
(LFB) system has been developed to stabilize beams
for the operation of a storage ring based Free
Electron Laser (FEL) and the High Intensity
Gamma-ray Source (HIGS) at the Duke storage ring.
Employing a Giga-sample FPGA based processor
(iGP), the LFB is capable of damping out the dipole
mode oscillation for all 64 bunches. As a
critical subsystem of the LFB system, kicker
cavity is developed with a center frequency of
938 MHz, a wide bandwidth (> 90 MHz), and a high shunt
impedance (> {10}00 Ω). First commissioned in summer
2008, the LFB has been operated to stabilize high
current multi-bunch operation. More recently,
the LFB system is demonstrated as a critical
instrument to ensure stable operation of the
HIGS with a high intensity gamma beam above 20 MeV
with a frequent top-off injection to compensate
for the substantial and continuous electron beam
loss in the Compton scattering process. In the
future, we will perform detailed studies of the
impedance effects using the LFB system.},
Key = {fds167641}
}
@article{fds167642,
Author = {C. Sun and Y. K. Wu and J. Li and G. Rusev and A. P.
Tonchev},
Title = {Accurate energy measurement of an electron beam in a storage
ring using Compton scattering technique},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {3552-3554},
Year = {2009},
Abstract = {A gamma-ray beam produced by Compton scattering of
a laser beam and a relativistic electron beam has
been used to determine electron beam parameters.
In order to accurately measure the electron beam
energy, a fitting model based upon Compton
scattering cross section is introduced in this
paper. With this model, we have successfully
determined the energy of the electron beam in Duke
storage ring with a relative uncertainty of 3×
10-5 using a Compton gamma beam from the High
Intensity γ-ray Source (HIγS) facility at Duke
University.},
Key = {fds167642}
}
@article{fds167643,
Author = {C. Sun and Y. K. Wu and G. Rusev and A. P. Tonchev},
Title = {End-to-End Spectrum Reconstruction of Compton Gamma-Ray Beam
to Determine Electron Beam Parameter},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1363-1365},
Year = {2009},
Abstract = {A gamma-ray beam produced by Compton scattering of
a laser beam with a relativistic electron beam has
been used to determine the electron beam
parameters. In the past, the electron beam
energy and energy spread were directly fit from
the high energy edge of a measured gamma beam
spectrum using a gamma-ray detector. However,
due to non-ideal response of the detector, the
measured spectrum cannot represent the true
energy distribution of the gamma-ray beam. Thus,
the electron beam energy and energy spread could
not be accurately determined from the measured
gamma beam spectrum. In this paper, we will present a
novel end-to-end spectrum reconstruction method to
accurately extract the energy distribution
of the gamma-ray beam from the measured gamma beam
spectrum. Using this method we have accurately
determined the energy and energy spread of the
electron beam in Duke storage ring using a Compton
gamma-ray beam from the High Intensity γ-ray Source
(HIγS) facility.},
Key = {fds167643}
}
@article{fds167646,
Author = {J. Li and S. Huang and Y. K. Wu},
Title = {FEL transverse mode manipulation using an in-cavity aperture
system},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1235-1237},
Year = {2009},
Abstract = {The storage ring based free electron laser (FEL)
oscillator serves as a photon driver for the High
Intensity Gamma-Ray Source (HIGS) at Duke
University. The FEL cavity consists of two
concave mirrors with a large radius of curvature
of more than 27 m. Both cavity mirrors see very high
intensity intracavity FEL power; the
downstream mirror also receives higher harmonic
spontaneous UV-VUV radiation of wigglers. The
large heat load by various types of radiation can
deform the mirror surface, causing FEL mode
distortion. The FEL mirror can also be damaged by
intense UV-VUV wiggler harmonic radiation. To
mitigate these problems, a pair of water-cooled,
in-vacuum apertures have been installed inside the
FEL cavity. These apertures are ideal for
manipulating the FEL transverse profile. This
paper reports our study on the FEL transverse mode
shaping using these apertures, including the
characterization of the transverse mode
structure of the FEL beam under a variety of
operation conditions. These studies allow us to
minimize the diffraction loss of the fundamental
mode of the FEL while effectively reducing the
impact of off-axis UV-VUV wiggler radiation on
the FEL mirrors.},
Key = {fds167646}
}
@article{fds167644,
Author = {J. Zhang and C. Sun and W. Wu and J. Li and Y. K. Wu and A. W.
Chao},
Title = {Feasibility study of electron beam polarization measurement
using Touschek lifetime},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1671-1673},
Year = {2009},
Abstract = {Touschek scattering is the dominant loss
mechanism for the electron beam in a low energy
storage ring with a large bunch current. The Duke
Free-Electron Laser (FEL) storage ring typically
operates in the one-bunch or two-bunch mode with a very
high bunch current and a varying electron beam
energy as low as 250 MeV. The study of the Touschek
lifetime is important for improving the
performance of the Duke storage ring based light
sources, including the storage ring FELs and a FEL
driven Compton gamma source, the High Intensity
Gamma-ray Source. This work reports our lifetime
measurement results for few-bunch operation of
the Duke storage ring. The Touschek loss rate is
reduced when an electron beam is polarized in the
storage ring. The change of the Touschek lifetime can
be used as a method to monitor polarization of the
electron beam. In this work, we will also report our
preliminary results of the electron beam
energy measurements using the resonant
depolarization technique.},
Key = {fds167644}
}
@article{fds167645,
Author = {B. Jia and J. Li and Y. K. Wu},
Title = {Experimental study of storage ring FEL output power scaling
with electron beam energy spread},
Journal = {Proceedings of 2009 Particle Accelerator
Conference},
Pages = {1248-1250},
Year = {2009},
Abstract = {Accurate simultaneous measurements of
storage ring free-electron laser (SRFEL) average
power output and electron beam energy spread has
been achieved at the Duke FEL Laboratory. It is well
known that the SRFEL power is limited by the electron
beam synchrotron radiation power and the induced
energy spread of the electron beam. The two-wiggler
spectrum of an optical klystron can be used to
determine the energy spread of the electron beam.
Measuring the interference pattern of the
modulated spontaneous spectrum with the FEL
turned on, we are able to study the FEL power output as a
function of electron beam energy spread. As the
energy spread increases, the modulation in the
two-wiggler spectrum reduces, resulting in a
smaller FEL gain. During this process, the
operation of an optical klystron degrades back
to that of a conventional FEL. This paper reports
our recent experiment study of transition of the
FEL operation from an optical klystron to a
conventional FEL.},
Key = {fds167645}
}
@article{fds249374,
Author = {Pietralla, N and Li, TC and Fritzsche, M and Ahmed, MW and Costin, TAA and Enders, J and Li, J and uller, SM and Neumann-Cosel, PV and Pinayev, IV and Ponomarev, VY and Savran, D and Tonchev, AP and Tornow, W and Weller,
HR and Werner, V and Wu, YK and Zilges, A},
Title = {Competition Between Excited Core States and $1$ $\hbar
\omega$ Single-particle Excitations at Comparable Energies
in $^{207}$Pb from Photon Scattering},
Journal = {Phys. Lett. B},
Volume = {681},
Number = {2},
Pages = {134-138},
Publisher = {Elsevier BV},
Year = {2009},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2009.09.059},
Abstract = {The Pb(\vec{γ} ,γ') photon scattering reaction has been
studied with the nearly monochromatic, linearly polarized
photon beams at the High Intensity γ -ray Source (HIγ S)
at the DFELL. Azimuthal scattering intensity asymmetries
measured with respect to the polarization plane of the beam
have been used for the first time to assign both the spin
and parity quantum numbers of dipole excited states of
206,207,208Pb at excitation energies in the vicinity of 5.5
MeV. Evidence for dominant particle–core coupling is
deduced from these results along with information on
excitation energies and electromagnetic transition matrix
elements. Implications of the existence of weakly coupled
states built on highly excited core states in competition
with 1¯hω single particle (hole) excitations at comparable
energies are discussed.},
Doi = {10.1016/j.physletb.2009.09.059},
Key = {fds249374}
}
@article{fds249375,
Author = {Bernstein, AM and Ahmed, MW and Stave, S and Wu, YK and Weller,
HR},
Title = {Chiral Dynamics in Photo-Pion Physics: Theory, Experiment,
and Future Studies at the HI$\gamma$S Facility},
Journal = {Annual Review of Nuclear and Particle Science},
Volume = {59},
Number = {1},
Pages = {115-144},
Publisher = {ANNUAL REVIEWS},
Year = {2009},
ISSN = {0163-8998},
url = {http://dx.doi.org/10.1146/annurev.nucl.010909.083220},
Abstract = {We review photopion experiments on the nucleon in the
near-threshold region.We compare the results with the
predictions of the low-energy theorems of quantum
chromodynamics calculated using chiral perturbation theory
(ChPT), which is based on the spontaneous breaking of chiral
symmetry as well as explicit breaking due to the finite
quark masses. As a result of the vanishing of the threshold
amplitudes in the chiral limit, the experiments are
difficult to perform because the cross sections are small.
Nevertheless, the field is now mature in terms of accuracy
and sensitivity.We also discuss the accomplishments and
limitations of past measurements, as well as future planned
experiments at Mainz and HIγS. The technical developments
required for the HIγS facility are emphasized. Finally, we
show that future experiments will provide even more accurate
tests of ChPT and will be sensitive to isospin-breaking
dynamics due to the mass difference between the up and down
quarks.},
Doi = {10.1146/annurev.nucl.010909.083220},
Key = {fds249375}
}
@article{fds249376,
Author = {Huang, S and Li, J and Wu, YK},
Title = {Water Cooled, In-cavity Apertures for High Power Operation
of FEL Oscillators},
Journal = {Nucl. Instr. Methods A},
Volume = {606},
Number = {3},
Pages = {762-769},
Publisher = {Elsevier BV},
Year = {2009},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2009.04.017},
Abstract = {In an oscillator FEL, higher-order harmonic radiation from
wigglers can cause serious damage to the downstream FEL
resonator mirror and limit the maximum electron beam current
for FEL operation due to thermal overload. These problems
can be effectively dealt with for FELs driven by helical
wigglers using a system to block off-axis wiggler harmonic
radiation. In this paper, we report a new scheme to block
the off-axis radiation from helical wigglers using a set of
motorized, water-cooled, in-cavity apertures. These
apertures can reduce the wiggler harmonic radiation power
load on the downstream FEL resonator mirror by two orders of
magnitude or more. With these apertures, we were able to
operate the Duke FEL with record high intracavity power in
infrared and visible wavelengths and extend FEL operation
into ultraviolet wavelengths with a large electron beam
current. The technique for limiting wiggler harmonic
radiation using in-cavity apertures is expected to be useful
for other types of FEL oscillators including high average
power FEL oscillators driven by superconducting
linacs.},
Doi = {10.1016/j.nima.2009.04.017},
Key = {fds249376}
}
@article{fds249377,
Author = {Sun, C and Li, J and Rusev, G and Tonchev, AP and Wu,
YK},
Title = {Energy and energy spread measurements of an electron beam by
Compton scattering method},
Journal = {Phys. Rev. ST Accel. Beams},
Volume = {12},
Number = {6},
Pages = {062801},
Publisher = {American Physical Society (APS)},
Year = {2009},
ISSN = {1098-4402},
url = {http://dx.doi.org/10.1103/PhysRevSTAB.12.062801},
Abstract = {A gamma-ray beam produced by Compton scattering of a laser
beam with an electron beam can be used to measure the
electron beam parameters. In several published works, a
simple fitting model has been applied to determine the
electron beam energy and energy spread without considering
the gamma beam collimation and electron beam emittance
effects. This fitting model is rederived in this work, and
the underlying assumptions and resultant limitations are
discussed. To overcome these limitations, a new fitting
model is proposed, which takes into account the collimation
and emittance effects. Using the new model and a gamma-ray
beam produced at the high intensity g-ray sources facility
at Duke University, we have successfully determined the
electron beam energy with a relative uncertainty of about 3
x10^-5 around 460 MeVas well as the electron beam energy
spread.We also experimentally demonstrated for the first
time that a small relative energy change (about 4 x 10^-5)
of the electron beam by varying the storage ring dipole
field can be directly detected using the Compton scattering
technique.},
Doi = {10.1103/PhysRevSTAB.12.062801},
Key = {fds249377}
}
@article{fds249378,
Author = {Sun, C and Wu, YK and Rusev, G and Tonchev, AP},
Title = {End-to-end spectrum reconstruction method for analyzing
Compton gamma-ray beams},
Journal = {Nucl. Instr. Methods A},
Volume = {605},
Number = {3},
Pages = {312-317},
Publisher = {Elsevier BV},
Year = {2009},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2009.03.237},
Abstract = {A gamma-ray beam produced by Compton scattering of a laser
beam with a relativistic electron beam has been used for
nuclear physics research at the high intensity g-ray source
(HIgS) facility at Duke University. The success of many
experiments using the gamma-ray beam critically depends on
the accurate knowledge of the gamma-ray beam energy
distribution which is typically obtained by unfolding a
measured energy spectrum. Conventionally, the detector
response function used in the spectrum unfolding is
simulated by a simple Monte Carlo code in which an isotropic
gamma-ray event generator is used. However, for a Compton
scattered gamma-ray beam, this simulation method could lead
to an inaccurate detector response function, since it
neglects the spatial and energy distributions of the
gamma-ray beam. In this paper, we will present a novel
end-to-end gamma-ray spectrum reconstruction method by
completely modeling the process of the Compton gamma-ray
beam production, collimation, transportation and detection.
Using this method, we have successfully reconstructed the
energy distribution of HIgS beams for nuclear physics
research with a high degree of accuracy.},
Doi = {10.1016/j.nima.2009.03.237},
Key = {fds249378}
}
@article{fds249379,
Author = {Rusev, G and Tonchev, AP and Schwengner, R and Sun, C and Tornow, W and Wu,
YK},
Title = {Multipole mixing ratios of transitions in
$^{11}$B},
Journal = {Phys. Rev. C},
Volume = {79},
Number = {4},
Pages = {047601},
Publisher = {American Physical Society (APS)},
Year = {2009},
ISSN = {0556-2813},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000266634300076&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {Photon scattering experiments with photon energies up to 3.6
MeV have been performed on the axially deformed nucleus
164Dy. We observe the -decay from the scissors mode to the
-vibration for the first time in a well-deformed rotor.
Previous ambiguities in the level scheme are resolved by a
novel spectroscopic usage of the nearly-monochromatic photon
beam from laser-Compton backscattering. The observed decay
rate is sensitive to the finite size of the nuclear quantum
system.},
Doi = {10.1103/PhysRevC.79.047601},
Key = {fds249379}
}
@article{fds249260,
Author = {Huang, S and Swift, G and Wu, YK},
Title = {Controlling wiggler harmonic radiation to reduce damage to
FEL cavity mirrors},
Journal = {30th International Free Electron Laser Conference, FEL
2008},
Pages = {135-138},
Year = {2008},
Month = {December},
Abstract = {In an oscillator FEL, higher-order harmonic radiation from
wigglers can cause serious damage to the downstream FEL
resonator mirror or limit the maximum electron beam current
for FEL operation due to thermal overload. With a helical
wiggler, higher-order harmonic radiation is peaked off-axis.
By blocking the off-axis wiggler harmonic power, the
radiation damage to the FEL resonator mirror can be reduced.
In this paper, we report a recently developed scheme to
control the off-axis harmonic radiation from helical FEL
wigglers using a set of motorized, water-cooled, in-vacuum
apertures. These apertures can reduce the harmonic power
load on the downstream FEL resonator mirror by one order of
magnitude. With these apertures, high power FEL operation
with a high electron beam current will become feasible in
the UV-VUV wavelength range with Duke storage ring
FELs.},
Key = {fds249260}
}
@article{fds249261,
Author = {Mikhailov, SF and Popov, VG and Huang, S and Li, J and Wu,
YK},
Title = {A pass-by-pass gain measurement technique for oscillator
FELs},
Journal = {30th International Free Electron Laser Conference, FEL
2008},
Pages = {139-142},
Year = {2008},
Month = {December},
Abstract = {We present a new pass-by-pass gain measurement technique for
a storage ring FEL. Typically, the FEL oscillator gain is
obtained by measuring the growth of the envelope of an
optical macropulse using a slow photo-detector. While
successfully used for low-gain FEL operation at Duke FEL
laboratory for many years, this method was not adequate for
measuring higher gains of distributed optical klystron FELs.
We have developed a new gain measurement technique based
upon the direct measurement of the micropulse energy from
one pass to another using fast photo-detectors. This
technique provides a powerful tool to study the entire FEL
gain process, including the startup process of the FEL
lasing. In this work, we describe this new gain measurement
technique in detail and compare it with the old technique.
Using fast photo-detectors with a picosecond time response,
this new technique can be extended to measure the gain of
other oscillator FELs, including those driven by
superconducting linacs.},
Key = {fds249261}
}
@article{fds249326,
Author = {Blackston, MA and Ahmed, MW and Perdue, BA and Welller, HR and Bewer, B and Pywell, RE and Wurtz, WA and Igarashi, R and Kucuker, S and Norum, B and Wang, K and Li, J and Mikhailov, SF and Popov, VG and Wu, YK and Sawatzky,
BD},
Title = {Erratum: First observation of the splittings of the E1
p-wave amplitudes in low energy deuteron photodisintegration
and its implications for the Gerasimov-Drell-Hearn sum rule
integrand (Physical Review C (2008) 78 (034003))},
Journal = {Physical Review C - Nuclear Physics},
Volume = {78},
Number = {6},
Publisher = {American Physical Society (APS)},
Year = {2008},
Month = {December},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.78.069905},
Doi = {10.1103/PhysRevC.78.069905},
Key = {fds249326}
}
@article{fds304635,
Author = {Blackston, MA and Ahmed, MA and Perdue, BA and Weller, HR and Bewer, B and Pywell, RE and Wurtz, WA and Igarashi, R and Kucuker, S and Norum, B and Wang, K and Li, J and Mikhailov, SF and Popov, VG and Wu, YK and Sawatzky,
BD},
Title = {First observation of the splittings of the E1 p-wave
amplitudes in low energy deuteron photodisintegration and
its implications for the Gerasimov-Drell-Hearn Sum Rule
integrand},
Journal = {Physical Review C - Nuclear Physics},
Volume = {78},
Number = {3},
Publisher = {American Physical Society (APS)},
Year = {2008},
Month = {September},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.78.034003},
Abstract = {Angular distributions of the cross section and linear
analyzing powers have been measured for the d(γ→,n)p
reaction at the High Intensity γ-ray Source with linearly
polarized beams of 14 and 16 MeV. The outgoing neutrons were
detected using the Blowfish detector array, consisting of 88
liquid scintillator detectors with large solid angle
coverage. The amplitudes of the reduced transition matrix
elements were extracted by means of fits to the data and
good agreement was found with a recent potential model
calculation of the splittings of the triplet p-wave
amplitudes. The extracted amplitudes are used to reconstruct
the Gerasimov-Drell-Hearn sum rule integrand for the
deuteron and are compared to theory. © 2008 The American
Physical Society.},
Doi = {10.1103/PhysRevC.78.034003},
Key = {fds304635}
}
@article{fds249380,
Author = {Weller, HR and Ahmed, M and Gao, H and Tornow, W and others},
Title = {Research Opportunities at the Upgraded HIGS
Facility},
Journal = {Progress in Particle and Nuclear Physics},
Volume = {62},
Number = {DOI: 10.1016/j.ppnp.2008.07.001},
Pages = {257-303},
Publisher = {Elsevier BV},
Year = {2008},
ISSN = {0146-6410},
url = {http://dx.doi.org/10.1016/j.ppnp.2008.07.001},
Abstract = {The High Intensity γ-ray Source (HIγS) is a joint project
between the Triangle Universities Nuclear Laboratory (TUNL)
and the Duke Free Electron Laser Laboratory (DFELL). This
facility utilizes intra-cavity back-scattering of the FEL
light in order to produce intense γ-ray beams. An upgrade
which allows for the production of γ-rays up to energies of
about 100 MeV having total intensities in excess of 108/s is
essentially complete. The primary component of the upgrade
is a 1.2 GeV booster-injector which makes it possible to
replace lost electrons at full energy. In addition, an
upgrade of the present linear undulator to a helical system
has made it possible to produce nearly 100% linear and
circularly polarized beams. The full system was commissioned
in the early part of 2007. A nuclear physics research
program using beams at energies below 50 MeV commenced in
the fall of 2007. The proposed experimental program includes
low-energy studies of nuclear reactions of importance in
nuclear astrophysics as well as studies of nuclear structure
using the technique of nuclear resonance fluorescence (NRF).
Few-body nuclear physics problems will also be addressed by
studying photodisintegration of d, 3He and 4He. Future
double-polarization experiments include a study of the
Gerasimov-Drell-Hearn Sum Rule for the deuteron and 3He, and
an extensive Compton scattering program designed to probe
the internal structure of the nucleon. A major focus of
these studies will be the measurement of the electric and
magnetic polarizabilities as well as the
spin-polarizabilities of the proton and the neutron. This
review will describe the principles of operation of the
upgraded facility, followed by a description of the
performance which has been achieved to date, and a
projection of the performance anticipated in the near
future. Following this, we will review several of the
research areas of nuclear physics which are accessible using
this facility, and describe both the results to date and
proposed experiments being developed for the future. © 2008
Elsevier B.V. All rights reserved.},
Doi = {10.1016/j.ppnp.2008.07.001},
Key = {fds249380}
}
@article{fds249314,
Author = {Li, J and Wang, P and Wu, YK},
Title = {BPM signal conditioning for a wide range of single-bunch
current operation in the Duke storage ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {4042-4044},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096300144&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The beam position monitor system of the Duke storage ring
has been in operation since 1998. Recently, by injecting at
higher energy with a booster synchrotron, the single bunch
current threshold is much more increased. The high peak
voltage associated with high single-bunch current degrades
the performance of the BPM system and can potentially damage
the BPM electronics. To improve the accuracy of the orbit
measurement, we carefully studied the BPM signal and found a
way to overcome this problem. This paper reports our
findings and presents a solution to condition the signal for
a wide single-bunch current operation. ©2007
IEEE.},
Doi = {10.1109/PAC.2007.4440050},
Key = {fds249314}
}
@article{fds249315,
Author = {Popov, V and Busch, M and Hartman, S and Mikhailov, S and Oakeley, O and Wallace, P and Wu, YK},
Title = {Power supply system for a compact 1.2 GEV booster
synchrotron},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {521-523},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096301098&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {Low cost power supply system for compact full energy booster
synchrotron was designed, developed and successfully
commissioned at Duke University. 500kW second hand thyristor
controlled power supply has been completely rebuilt to
provide high accuracy ramping of current in the range
between 150A and 700A in a 1.3 sec repetition cycle.
Reproducibility of current at injection and extraction
energy of better than 0.2% was achieved. Conflict of
requirements of a fast ramp operation and a magnet
protection in the case of emergency shutdown was resolved by
means of additional thyristor switches. All trim power
supplies involved in ramp have been matched with main power
supply for the time response and voltage range. Vertical
injection to and extraction from the booster requires a
strong Y-bump. Combination of low voltage DC power supply
and pulse boosting circuit has eliminated the need of
expensive power supply for peak power about 4 kW. Challenges
of design, main parameters of the booster power supply
system and discussion of operation experience are presented
in this paper. ©2007 IEEE.},
Doi = {10.1109/PAC.2007.4440265},
Key = {fds249315}
}
@article{fds249316,
Author = {Hartman, SM and Mikhailov, SF and Popov, V and Wu,
YK},
Title = {A physics based approach for ramping magnet control in a
compact booster},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {515-517},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096301096&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {At Duke University, a booster synchrotron was recently
commissioned as part of the High Intensity Gamma-ray Source
(HIGS) upgrade. For the ramping magnet power supply
controls, a scheme was developed to present the high level
operator interface in terms of the physics quantities of the
accelerator, i.e. the effective focusing strength of the
magnets. This scheme allows for the nonlinearities of the
magnets - a result of the extremely compact footprint of
this booster - to be incorporated into the low level
software. This facilitates machine studies and simplifies
the use of physics modeling. In addition, it simplifies
operation, allowing the booster to ramp to any energy from
the 0.24 GeV of the injector linac to the 1.2 GeV maximum of
the Duke storage ring. The high level of flexibility of this
system is further advanced by incorporating the level of
tunability typically found in a storage ring control system.
Tuning changes made during steady-state operation are
automatically propagated to the waveforms which make up the
booster ramp. This approach provides a good match to the
wide operation modes of the Duke storage ring and its
associated free electron laser (FEL), and may be useful for
other compact booster synchrotrons. ©2007
IEEE.},
Doi = {10.1109/PAC.2007.4440263},
Key = {fds249316}
}
@article{fds249317,
Author = {Huang, S and Li, J and Wu, YK},
Title = {A direct electron beam energy spread measurement system for
beam instability and FEL research},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {4045-4047},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096300145&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {One of critical beam parameters for the storage ring based
light sources is the energy spread of the electron beam. An
accurate measurement of the energy spread remains a
challenge. It is well known that the energy spread of the
electron beam can degrade the spontaneous radiation spectrum
of an Optical-Klystron (OK) which consists of two wigglers
separated by a buncher magnet. The reduced modulation in the
spectrum can be used to determine the energy spread of the
beam. This paper describes our newly developed energy spread
measurement system employing a compact and versatile
spectrometer. This system is used in the beam instability
research and Free-Electron Laser (FEL) research. In
particular, by measuring the increase of electron beam
energy spread we have studied the onset of microwave
instability. ©2007 IEEE.},
Doi = {10.1109/PAC.2007.4440051},
Key = {fds249317}
}
@article{fds249318,
Author = {Wu, YK and Li, J and Popov, V and Mikhailov, SF and Wang,
P},
Title = {A tune measurement system for lowcurrent and energy ramping
operation of a booster synchrotron},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {4063-4065},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096300148&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {A betatron tune measurement system is one of the most
important diagnostic tools for any circular accelerator. For
the commissioning of a booster synchrotron newly developed
for top-off injection into the Duke storage ring, a
versatile tune measurement system employing a network
analyzer, a short stripline kicker, a space filter and a
photomultiplier tube has been developed to allow tune
measurements over a wide range of beam energies from 0.24 to
1.2 GeV, and for low current measurements at a few
micro-amperes. The signal from the highly sensitive optical
detection system is also used for fast tune measurements
with a realtime oscilloscope. This technique is being
developed for live tune monitoring during booster energy
ramping. ©2007 IEEE.},
Doi = {10.1109/PAC.2007.4440054},
Key = {fds249318}
}
@article{fds249319,
Author = {Kim, Y and Wu, W and Busch, M and Wang, P and Wu, YK and Teytelman, D and Park, IS and Ko, IS},
Title = {New generation digital longitudinal feedback system for Duke
FEL and HIγS facilities},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {518-520},
Publisher = {IEEE},
Year = {2007},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2007.4440264},
Abstract = {To cure harmful longitudinal coupled-bunch mode beam
instabilities during high-current and multi-bunch beam
operations at the Duke Free Electron Laser (FEL) and High
Intensity γ-ray Source (HIγS) facilities, we have been
developing a new generation digital bunch-by-bunch
longitudinal feedback (LFB) system which is based on an
Integrated Gigasample Processor (iGp-64F). In this paper, we
describe the new generation digital longitudinal feedback
system for the Duke FEL and HIγS facilities. ©2007
IEEE.},
Doi = {10.1109/PAC.2007.4440264},
Key = {fds249319}
}
@article{fds249320,
Author = {Sun, C and Wu, YK},
Title = {The feasibility study of measuring the polarization of a
relativistic electron beam using a compton scattering
gamma-ray source},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {4057-4059},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096300147&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The Compton scattering of a circularly polarized photon beam
and a polarized electron beam leads to an asymmetric spatial
distribution of the gamma rays. This asymmetry has been
calculated for the High Intensity Gamma-ray Source (HIGS)
beam at Duke University. Owing to the high intensity of the
HIGS beam, this asymmetry is determined to be measurable
with a small statistical error using a simple optical
imaging system for gamma-ray beams. We propose to set up
this system to measure the polarization of the electron beam
in the Duke storage ring. ©2007 IEEE.},
Doi = {10.1109/PAC.2007.4440053},
Key = {fds249320}
}
@article{fds249321,
Author = {Wu, YK},
Title = {Accelerator physics research and light source development
programs at Duke University},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {1215-1217},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096304074&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The Duke Free-Electron Laser Laboratory (DFELL) has recently
completed two major accelerator/light source development
projects - we successfully commissioned the world's first
distributed optical klystron FEL (DOK-1 FEL) and a new 0.24
- 1.2 GeV booster synchrotron. The DOK-1 FEL has a much
improved FEL gain compared with two-wiggler optical
klystrons. This allows the DOK-1 FEL to become a versatile
light source for UV-VUV operation and as a driver for a
high-flux Compton gamma-source. The top-off booster injector
for the Duke storage ring is part of the upgrade project of
High Intensity Gamma-ray Source (HIGS), a facility jointly
developed by the DFELL and Triangle Universities Nuclear
Laboratory. The accelerator and light source development has
created new opportunities for accelerator physics research.
In this paper, we will report our recent progress in
accelerator and light source development as well as the
ongoing accelerator physics research programs at the DFELL.
©2007 IEEE.},
Doi = {10.1109/PAC.2007.4441034},
Key = {fds249321}
}
@article{fds249322,
Author = {Li, J and Mikhailov, SF and Huang, S and Popov, V and Wu,
YK},
Title = {Compensation of the beam dynamics effects caused by the
extraction Lambertson septum of the HIGS
booster},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {3582-3584},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096302069&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {As part of the High Intensity Gamma-Ray Source (HIGS)
upgrade, the booster synchrotron has been built and
commissioned in 2006. It ramps the electron beam between
0.24 and 1.2 GeV for top-off injection into the Duke storage
ring. The booster has vertical injection/extraction which
uses symmetrical schemes with a bumped orbit. The
injection/extraction kickers and corresponding septum
magnets are located in the opposite straight sections of the
booster ring separated by about 1/4 of the vertical betatron
wave. Due to the non-ideal properties of the magnetic
material, the magnetic field leaks out into the stored beam
chamber, which results in orbit distortion, tune and
chromaticity shifts, and change of coupling. The dynamics
impacts due to the leaked septum fields have been
successfully compensated to achieve good injection
efficiency. ©2007 IEEE.},
Doi = {10.1109/PAC.2007.4440499},
Key = {fds249322}
}
@article{fds249323,
Author = {Mikhailov, SF and Wu, YK and Li, J and Popov, VG and Hartman,
SM},
Title = {Challenges for energy ramping in a compact booster
synchrotron},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {1212-1214},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096304073&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {A booster synchrotron has been recently commissioned at Duke
University FEL Laboratory as a part of the High Intensity
Gamma-ray Source (HIGS) facility. The booster provides
top-off injection into the storage ring in the energy range
of 0.24 - 1.2 GeV. In order to minimize the cost of the
project, the booster is designed with a very compact
footprint. As a result, unconventionally high field bending
magnets at 1.76 T are required. A main ramping power supply
drives all dipoles and quadrupoles. Quadrupole trims are
used to compensate for tune changes caused by the change of
relative focusing strength during ramping. Sextupoles
compensate for chromatic effects caused by dipole magnet
pole saturation. All these compensations have to be
performed as a function of beam energy. Above 1.1 GeV, where
the magnets are heavily saturated, the reduction of dynamic
aperture is compensated by redistribution of strength among
the sextupole families. With these compensations, effects of
the magnet saturation do not cause any considerable beam
loss during injection, energy ramping, and extraction.
©2007 IEEE.},
Doi = {10.1109/PAC.2007.4441033},
Key = {fds249323}
}
@article{fds249324,
Author = {Popov, V and Busch, M and Hartman, S and Li, J and Mikhailov, S and Wallace, P and Wang, P and Wu, YK and Kurkin, GY},
Title = {Electron beam diagnostics for compact 1.2 GEV booster
synchrotron},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {4051-4053},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2007.4440052},
Abstract = {First operational experience has been gained with the linac
and booster diagnostic system during the commissioning of
the booster synchrotron at Duke University. The booster was
designed and developed as an injector for the storage ring
as a part of the High Intensity Gamma-ray Source (HIGS)
upgrade of Duke FEL storage ring. Booster beam
instrumentation includes: beam charge measurements (Faraday
cups, Integrated Current Transformers (ICT), Modular
Parametric Current Transformer (MPCT)), beam position
monitoring (BPM), betatron tune measurements using
synchrotron radiation (SR), transverse profile and temporal
beam structure monitoring (insertable screens, striplines,
dissector). The diagnostics provided good understanding of
electron beam behavior and allowed us to adjust important
beam parameters within design specifications. An overview of
the diagnostic instrumentation of the Duke Booster
synchrotron is given along with measurement examples and
discussion of operational experience. ©2007
IEEE.},
Doi = {10.1109/PAC.2007.4440052},
Key = {fds249324}
}
@article{fds249333,
Author = {Mikhailov, SF and Busch, MD and Emamian, M and Hartman, SM and Kim, Y and Li, J and Popov, VG and Swift, G and Wallace, PW and Wang, P and Wu, YK and Howell, CR and Gavrilov, NG and Kurkin, GY and Matveev, Y and Anchugov,
OV and Shvedov, DA and Vinokurov, NA},
Title = {Commissioning of the booster injector synchrotron for the
HIGS facility at Duke University},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {1209-1211},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096304072&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {A booster synchrotron (Duke booster) has been built and
recently commissioned at Duke University Free Electron Laser
Laboratory (DFELL) as part of the High Intensity Gamma-ray
Source (HIGS) facility upgrade. HIGS is collaboration
between the DFELL and Triangle Universities Nuclear
Laboratory (TUNL). The booster provides top-off injection
into the Duke FEL storage ring in the energy range of 0.24 -
1.2 GeV. When operating the Duke storage ring to produce
high energy Compton gamma ray beams above 20 MeV, continuous
electron beam loss occurs. The lost electrons are
replenished by the booster injector operating in the top-off
mode. The presentt operational injection and extraction rate
of the machine allows us to routinely replenish up to 5·10
8 electrons per second. The compactness of the booster posed
a challenge for its development and commissioning. The
booster has been successfully commissioned in 2006. This
paper reports experience of commissioning and initial
operation of the booster. ©2007 IEEE.},
Doi = {10.1109/PAC.2007.4441032},
Key = {fds249333}
}
@article{fds249336,
Author = {Kim, Y and Li, J and Wu, Y},
Title = {Growth time of the longitudinal coupled bunch mode beam
instability at the Duke FEL facility},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Pages = {4036-4038},
Publisher = {IEEE},
Year = {2007},
Month = {December},
ISBN = {978-1-4244-0916-7},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000255096300143&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {To determine the required power of an amplifier for the
longitudinal feedback (LFB) system, the growth time of the
strongest longitudinal coupled bunch mode instability (CBMI)
in the Duke storage ring should be measured in advance. In
2005, we measured strength of the strongest longitudinal
beam instability in the Duke storage ring with four and
eight symmetrically filled buckets. By analyzing measured
data, the growth time of the strongest dipole mode of the
longitudinal CBMI in the Duke storage ring can be estimated.
At a beam energy of 274 MeV, the growth time is about 0.365
ms for a total stored beam current of 160 mA. From the
measured growth time, we estimated the required power of the
amplifier for the LFB system. To damp all harmful
longitudinal CBMIs with an energy deviation of 0.1% (rms)
within its growth time of 0.365 ms, we have to supply about
110 W (rms) to an LFB kicker whose a central frequency is
937.3875 MHz. In this paper, we describe the growth time of
the longitudinal CBMI at the Duke storage ring and the
estimation of the required power for the LFB system to damp
all CBMIs within 0.365 ms. ©2007 IEEE.},
Doi = {10.1109/PAC.2007.4440049},
Key = {fds249336}
}
@article{fds249332,
Author = {Tonchev, AP and Angell, C and Boswell, M and Chyzh, A and Howell, CR and Karwowski, HJ and Kelley, JH and Tornow, W and Tsoneva, N and Wu,
YK},
Title = {Study of collective dipole excitations below the giant
dipole resonance at HIγS},
Journal = {AIP Conference Proceedings},
Volume = {891},
Pages = {339-347},
Publisher = {AIP},
Year = {2007},
Month = {April},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.2713535},
Abstract = {The High-Intensity Gamma-ray Source utilizing intra-cavity
back-scattering of free electron laser photons from
relativistic electrons allows one to produce a unique beam
of high-flux gamma rays with 100% polarization and
selectable energy and energy resolution which is ideal for
low-energy γ-ray scattering experiments. Nuclear resonance
fluorescence experiments have been performed on N=82 nuclei.
High sensitivity studies of E1 and M1 excitations at
energies close to the neutron emission threshold have been
performed. The method allows the determination of excitation
energies, spin, parities, and decay branching ratios of the
pygmy dipole mode of excitation. The observations are
compared with calculations using statistical and
quasi-particle random-phase approximations. © 2007 American
Institute of Physics.},
Doi = {10.1063/1.2713535},
Key = {fds249332}
}
@article{fds292655,
Author = {MacDowell, AA and Feng, J and Demello, A and Doran, A and Duarte, R and Forest, E and Kelez, N and Marcus, MA and Miller, T and Padmore, HA and Raoux, S and Robin, D and Scholl, A and Schlueter, R and Schmid, P and Stöhr, J and Wan, W and Wei, DH and Wu, Y},
Title = {Progress on PEEM3 - An aberration corrected X-ray
photoemission electron microscope at the
ALS},
Journal = {AIP Conference Proceedings},
Volume = {879},
Pages = {1341-1344},
Publisher = {AIP},
Year = {2007},
Month = {March},
ISBN = {9780735403734},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.2436312},
Abstract = {A new ultrahigh-resolution photoemission electron microscope
called PEEM3 is being developed and built at the Advanced
Light Source (ALS). An electron mirror combined with a
much-simplified magnetic dipole separator is to be used to
provide simultaneous correction of spherical and chromatic
aberrations. It is installed on an elliptically polarized
undulator (EPU) beamline, and will be operated with very
high spatial resolution and high flux to study the
composition, structure, electric and magnetic properties of
complex materials. The instrument has been designed and is
described. The instrumental hardware is being deployed in 2
phases. The first phase is the deployment of a standard PEEM
type microscope consisting of the standard linear array of
electrostatic electron lenses. The second phase will be the
installation of the aberration corrected upgrade to improve
resolution and throughput. This paper describes progress as
the instrument enters the commissioning part of the first
phase. © 2007 American Institute of Physics.},
Doi = {10.1063/1.2436312},
Key = {fds292655}
}
@article{fds141063,
Author = {Y. Kim and M. D. Busch and P. Wang and W. Wu and Y. K. Wu and J. Choi and I.
S. Ko and I. S. Park and D. Teytelman},
Title = {New Generation Digital Longitudinal Feedback System for Duke
FEL and HIGS Facilities},
Pages = {518-520},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Year = {2007},
Key = {fds141063}
}
@article{fds141045,
Author = {Y. Kim and J. Li and Y. K. Wu},
Title = {Growth Time of Longitudinal Coupled Bunch Mode Instability
in the Duke FEL Facility},
Pages = {4036-4038},
Booktitle = {Proceedings of 2007 Particle Accelerator
Conference},
Year = {2007},
Key = {fds141045}
}
@article{fds249313,
Author = {Werner, V and Pietralla, N and Von Brentano and P and Kneissl, U and Pitz,
HH and Tonchev, A and Ahmed, MW and Fransen, C and Von Garrel and H and Kohstall, C and Li, J and Linnemann, A and Müller, S and Pinayev, IV and Savran, D and Scheck, M and Stedile, F and Tornow, W and Walter, S and Weller, HR and Wu, YK},
Title = {New findings for mixed-symmetry states},
Journal = {AIP Conference Proceedings},
Volume = {819},
Pages = {340-344},
Booktitle = {AIP Conf.Proc.},
Publisher = {AIP},
Editor = {A.Woehr, A.Aprahamian},
Year = {2006},
Month = {March},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.2187881},
Abstract = {This report summarizes experiments performed on 164Dy using
photon scattering techniques. The scissors mode in 164Dy has
been reinvestigated using unpolarized photons from
bremsstrahlung and polarized photons from a free electron
laser. The current experiments lead to the observation of a
new decay mode of the scissors mode in well-deformed rotors.
© 2006 American Institute of Physics.},
Doi = {10.1063/1.2187881},
Key = {fds249313}
}
@article{fds249363,
Author = {al, TCLE and Weller, IHR},
Title = {First evidence for spin-flip M1 strength in
40A},
Journal = {Physical Review C},
Volume = {73},
Number = {5},
Pages = {054306},
Publisher = {The American Physical Society},
Year = {2006},
Month = {March},
ISSN = {0556-2813},
url = {http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRVCAN000073000005054306000001&idtype=cvips&gifs=yes},
Abstract = {www.aps.org},
Doi = {10.1103/PhysRevC.73.054306},
Key = {fds249363}
}
@article{fds249366,
Author = {Wu, YK and Vinokurov, NA and Mikhailov, S and Li, J and Popov,
V},
Title = {High-Gain Lasing and Polarization Switch with a Distributed
Optical-Klystron Free-Electron Laser},
Journal = {Phys. Rev. Lett.},
Volume = {96},
Number = {22},
Pages = {224801},
Year = {2006},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16803315},
Abstract = {This Letter reports the first experimental results from the
world's first distributed optical-klystron (DOK)
free-electron laser (FEL), the DOK-1 FEL, at Duke
University. The DOK-1 FEL is a hybrid system, comprised of
four wigglers: two horizontal and two helical. With the
DOK-1 FEL, we have obtained the highest FEL gain among all
storage ring based FELs at 47.8% (±2.7%) per pass. We have
also demonstrated that the FEL gain can be enhanced by
increasing electron bunching using wigglers with a different
polarization. Furthermore, we have realized controlled
polarization switches of the FEL beam by a nonoptical means
through the manipulation of a buncher magnet.},
Doi = {10.1103/physrevlett.96.224801},
Key = {fds249366}
}
@article{fds249259,
Author = {Wu, YK and Mikhailov, S and Li, J and Popov, V and Vinokurov, NA and Gavrilov, NG and Shevchenko, OA and Vobly, PD and Kulipanov,
GN},
Title = {First lasingand initial operation ofa circularly polarized
optical klystron ok-5 felandavariably polarized distributed
optical klystron DOK-1 FEL at DUKE},
Journal = {Proceedings of the 27th International Free Electron Laser
Conference, FEL 2005},
Pages = {407-410},
Year = {2005},
Month = {December},
Abstract = {To improve the capability and performance of its light
sources, the Duke FEL lab (DFELL) is upgrading its storage
ring based FEL. The existing linearly polarized OK-4 FEL
wigglers are being replaced gradually by the next generation
OK-5 wigglers capable of producing either linearly or
circularly polarized light. In the second phase of this
upgrade in 2005, the OK-5 FEL consisting of two wigglers is
installed together with the OK-4 FEL in a specially designed
magnetic lattice. The circularly polarized OK-5 FEL was
first brought to lasing on Aug. 14, 2005. In the following
days, the first distributed optical klystron FEL with
variable polarization, the DOK-1 FEL, comprised of two
horizontal OK-4 wigglers and two circular OK-5 wigglers, was
brought to lasing for the first time. In this paper, we
report our commissioning experience and initial measurements
of both the OK-5 FEL and DOK-1 FEL.},
Key = {fds249259}
}
@article{fds249304,
Author = {Kurkin, G and Pinaev, I and Hartman, S and Mikhailov, S and Wu,
Y},
Title = {A new timing system for the Duke booster and storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {3159-3160},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1591398},
Abstract = {A dedicated booster synchrotron is being constructed at the
Duke FEL Laboratory to provide full energy injection into
the main electron storage ring. A new timing system has been
developed to coordinate the injection of electron bunches
from the linac to the booster, the ramping of energy in the
booster, and extraction of bunches into the main ring. The
timing system will allow the extraction of any bunch in the
booster into any selected bucket in the main ring to provide
top-off injection for any of the various operational bunch
patterns of the main ring. A new master oscillator has also
been developed for the RF system of the booster. The
oscillator may be tuned independently or phase-locked to the
master oscillator of the main ring. The issues of the soft
phase locking process of the new master oscillator are
discussed. The timing system and new oscillator have been
fabricated and tested and are ready for operation. © 2005
IEEE.},
Doi = {10.1109/PAC.2005.1591398},
Key = {fds249304}
}
@article{fds249305,
Author = {Wu, YK and Li, J and Wu, J},
Title = {Observations and measurements of anomalous hollow electron
beams in the duke storage ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {3082-3084},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1591371},
Abstract = {Anomalous hollow electron beams have been recently observed
in the Duke storage ring. With a single bunch beam in a
lattice with a negative chromaticity, a hollow beam can be
created. This beam consists of a solid core beam inside and
a large ring beam outside. In this paper, we report the
measurements of the hollow beam phenomenon, including its
distinct image pattern and spectrum signature, and its
evolution with time. By capturing the post-instability
bursting beam., the hollow beam is a unique model system for
studying transverse instabilities, in particular, the
interplay of the wakefield and lattice nonlinearity. The
hollow beam can also be used as a tool to study linear and
nonlinear particle dynamics in the storage ring. © 2005
IEEE.},
Doi = {10.1109/PAC.2005.1591371},
Key = {fds249305}
}
@article{fds249306,
Author = {Hartmant, SM and Mikhailov, SF and Wu, YK},
Title = {A control system for the duke booster synchrotron},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {3792-3794},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1591620},
Abstract = {The Duke Free Electron Laser Laboratory is developing a
booster synchrotron to provide full energy injection into
the Duke electron storage ring. In this paper, we describe
the development of the control system for the booster.
Requirements include the competing needs of simple and
reliable turn-key operation for the machine as a booster;
and the sophistication and flexibility of operation of the
machine as a storage ring for commissioning, machine studies
and as a light source. To simplify operations and machine
studies, the high level controls will present the system in
terms of the physics quantities of the accelerator, allowing
a tight integration between the physics model and the low
level hardware control, as we have previously implemented
for the Duke storage ring. © 2005 IEEE.},
Doi = {10.1109/PAC.2005.1591620},
Key = {fds249306}
}
@article{fds249307,
Author = {Steier, C and Robin, D and Decking, W and Laskar, J and Nadolski, L and Wu,
Y},
Title = {Measuring and understanding the momentum aperture in a
storage ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {645-649},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1590514},
Abstract = {The momentum aperture of a storage ring is a very important
parameter that strongly influences the performance,
especially the beam lifetime. For the special case of
synchrotron light sources with small emittance like the
Advanced Light Source (ALS), the momentum aperture depends
strongly on the transverse dynamics. It is very sensitive to
machine conditions such as the tunes, chromaticities,
lattice symmetry, and spurious coupling, since depending on
those conditions the Touschek scattered particles explore
different resonance regions in the phase space. In light
sources, the momentum aperture usually also depends strongly
on the vertical physical aperture. Applying frequency
analysis techniques in simulations and for turnby-turn orbit
measurement data provides a very powerful tool to measure
and understand limitations of the dynamic momentum aperture.
The techniques presented are applicable to other light
sources, as well as damping rings and many types of
colliders. © 2005 IEEE.},
Doi = {10.1109/PAC.2005.1590514},
Key = {fds249307}
}
@article{fds249308,
Author = {Li, J and Wu, YK and Sun, C},
Title = {Improved long radius of curvature measurement system for FEL
mirrors},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {1787-1789},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1590913},
Abstract = {The 53.73 meter long Duke free electron laser (FEL) cavity
consists of two concave mirrors with radius of curvature
longer than 27 meters. A proper radius of curvature is
designed to achieve an optimal and stable operation of the
FEL. This requires accurate measurements of the cavity
mirror's radius of curvature before its initial
installation. Subsequent radius of curvature measurements
are performed to ensure no significant deformation of the
mirror occurs after a period of extensive use. A direct
measurement based upon the geometric optics principles has
been used at Duke PEL Lab (DFELL) for years. Recently, we
have significantly upgraded this measurement apparatus by
utilizing a He-Ne laser as the light source and a straight
wire with a proper size as the object. In this paper we
describe the details of the measurement setup and report the
benefits of the recent upgrades. In addition, we report the
improved data analysis technique and results of recent long
radius of curvature measurements. © 2005
IEEE.},
Doi = {10.1109/PAC.2005.1590913},
Key = {fds249308}
}
@article{fds249309,
Author = {Popov, VG and Hartman, S and Mikhailov, SF and Oakeley, O and Wallace,
P and Wu, YK},
Title = {3 KA power supplies for the Duke OK-5 FEL
wigglers},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {3901-3903},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1591662},
Abstract = {The next generation electromagnetic OK-5/Duke storage ring
FEL wigglers [1], [2] require three 3kA/70V power supplies
with current stability about 20 ppm and current ripples less
than 20 ppm in their full operating range. Duke FEL
Laboratory acquired three out-of-service SCR controlled
power supplies (Trans-Rex, 5kA/100V), which were built
almost 30 years ago. The existing archaic firing circuit,
lack of any output voltage filtering and with an outdated
DCCT, would not be able to meet the above requirements. To
deliver the desirable high performance with very limited
funds, all three Trans-Rex power supplies have been
completely rebuilt in-house at DFELL. Modern high stability
electronic components and a high precision Danfysik DCCT
have been used. A new symmetrical firing circuit, efficient
passive filter and reliable transformer-coupled active
filter are used to reduce output current ripples to an
appropriate level. At the present time, all three
refurbished power supplies are in operation. One of these
power supplies was used since August, 2004 to feed OK-4
wigglers with good overall performance. Others two have been
tested and used as power supplies for magnetic measurements.
© 2005 IEEE.},
Doi = {10.1109/PAC.2005.1591662},
Key = {fds249309}
}
@article{fds249310,
Author = {Busch, M and Mikhailov, S and Emamian, M and Faircloth, J and Hartman,
S and Li, J and Popov, V and Swift, G and Vylet, V and Wallace, P and Wang, P and Wu, Y and Gavrilov, N and Kurkin, G and Matveev, Y and Shvedov, D and Anchugov, O and Vinokurov, N},
Title = {Status of the booster injector for the duke fel storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {3544-3546},
Publisher = {IEEE},
Year = {2005},
Month = {December},
ISBN = {0-7803-8859-3},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000235745200074&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {This paper presents the current status of the booster
synchrotron for the Duke Free Electron Laser Laboratory
(DFELL) storage ring. The booster will provide full energy
injection into the storage ring in a wide energy range from
0.27 to 1.2 GeV. When operating the DFELL storage ring as
the High Intensity Gamma Source (HIGS) to produce gamma
photons above 20 MeV with Compton scattering, continuous
electron loss occurs. The top-off mode operation of the
booster injector will enable the continuous operation of the
HIGS facility by replenishing the lost electrons. The design
requirement for a compact booster with the single bunch
extraction capability remains a challenge for the machine
development. Presently, the booster project is in the
installation phase. The magnetic elements, vacuum chambers,
injection and extraction kickers have been developed in
collaboration with and fabricated at the Budker Institute of
Nuclear Physics (BINP), Russia. The diagnostic and control
system is being developed at DFELL. The commissioning of the
booster synchrotron will start at the end of 2005. © 2005
IEEE.},
Doi = {10.1109/PAC.2005.1591533},
Key = {fds249310}
}
@article{fds249311,
Author = {Arbuzov, VS and Bushuev, A and Gavrilov, N and Gorniker, EI and Kenjebulatov, E and Kholopov, MA and Kondakov, AA and Krutikhin, SA and Kruchkov, YG and Kuptsov, IV and Kurkin, GY and Mironenko, LA and Mityanina, N and Motygin, SV and Osipov, VN and Petrov, V and Pilan, AM and Popov, AM and Rotov, E and Sedlyarov, I and Tribendis, AG and Volkov, V and Wang, P and Mikhailov, S and Wallace, PW and Wu, YK},
Title = {Commissioning of the new RF system with the HOM damped RF
cavity},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {1555-1556},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1590833},
Abstract = {A new 178 MHz RF system has been commissioned at Duke
Storage Ring. It consists of a 140 kW tetrode transmitter;
higher order modes (HOM) damped RF cavity and the necessary
frequency and voltage control electronics. The cavity walls
are made of copper-on-stainless steel bimetal (8 mm Cu, 7 mm
SS). The cavity has a larger beam pipe opening (700 mm in
diameter) in the down-stream side, which allows the HOM
propagating out of the cavity and being absorbed by the
ceramic loads. The design details and the commissioning
results are presented in this paper. © 2005
IEEE.},
Doi = {10.1109/PAC.2005.1590833},
Key = {fds249311}
}
@article{fds249312,
Author = {Popov, VG and Hartman, and Mikhailov, SF and Oakely, O and Wallace, P and Wu, YK},
Title = {Trim power supplies for the Duke booster and storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2005},
Pages = {3919-3921},
Publisher = {IEEE},
Year = {2005},
Month = {December},
url = {http://dx.doi.org/10.1109/PAC.2005.1591668},
Abstract = {The on-going Duke storage ring upgrades and the development
of a new booster synchrotron injector require more than 100
units of high performance unipolar and bipolar trim power
supplies in the current range of -15 A to +15 A. However,
most of the trim power supplies on the market do not deliver
two critical performance features simultaneously: a high
current stability and a low current noise. An in-house trim
power supply development program has been put in force to
design, fabricate, and test low cost linear power supplies
with current stability about 100 ppm and current ripples
less than 100 ppm in a broad band. A set of unipolar power
supplies (0-12 A) have been designed, fabricated and
successfully tested. Since August, 2004 they have been used
in storage ring operation with excellent performance. The
prototype of bipolar power supplies (±15 A) has been
designed and tested as well. The main design principles and
the performance results of both unipolar and bipolar
supplies have been presented in this paper. © 2005
IEEE.},
Doi = {10.1109/PAC.2005.1591668},
Key = {fds249312}
}
@article{fds249364,
Author = {Savran, D and Muller, S and Zilges, A and Babilon, M and Ahmed, MW and Kelley, JH and Tonchev, A and Tornow, K and Weller, HR and Pietralla, N and Li, J and Pinayev, IV and Wu, YK},
Title = {Parity Assignments in 172,174Yb using Polarized photons and
the K Quantum Number in Rare Earth Nuclei},
Journal = {Physical Review C},
Volume = {71},
Number = {3},
Pages = {034304},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {December},
ISSN = {0556-2813},
url = {http://hdl.handle.net/10161/11080 Duke open
access},
Abstract = {The 100% polarized photon beam at the high intensity γ ray
source (HIγS) at Duke University has been used to determine
the parity of six dipole excitations between 2.9 and 3.6 MeV
in the deformed nuclei 172,174Yb in photon scattering
(γ→, γ′) experiments. The measured parities are
compared with previous assignments based on the K quantum
number that had been assigned in nuclear resonance
fluorescence (NRF) experiments by using the Alaga rules. A
systematic survey of the relation between γ-decay branching
ratios and parity quantum numbers is given for the rare
earth nuclei. © 2005 The American Physical
Society.},
Doi = {10.1103/PhysRevC.71.034304},
Key = {fds249364}
}
@article{fds43902,
Author = {Y. K. Wu and J. Li and J. Wu},
Title = {Observations and Measurements of Anomalous Hollow Electron
Beams in a Storage Ring},
Journal = {Proceedings of Particle Accelerator Physics 2005, Knoxville,
TN, 2005},
Pages = {3082-3084},
Year = {2005},
Month = {May},
Abstract = {Anomalous hollow electron beams have been recently observed
in the Duke storage ring. With a single bunch beam in a
lattice with a negative chromaticity, a hollow beam can be
created. This beam consists of a solid core beam inside and
a large ring beam outside. In this paper, we report the
measurements of the hollow beam phenomenon, including its
distinct image pattern and spectrum signature, and its
evolution with time. By capturing the post-instability
bursting beam, the hollow beam is a unique model system for
studying transverse instabilities, in particular, the
interplay of the wakefield and lattice nonlinearity. The
hollow beam can also be used as a tool to study linear and
nonlinear particle dynamics in the storage
ring.},
Key = {fds43902}
}
@article{fds43901,
Author = {Y. K. Wu and Matthew D. Busch and Mark Emamian and Joe Faircloth and J.
Gustavsson, Steven M. Hartman and C. Howell and M. Johnson and Jingyi
Li, Stepan Mikhailov and Owen Oakeley and J. Patterson and Maurice
Pentico, Victor Popov and V. Rathbone and Gary Swift and Patrick
Walter Wallace and Ping},
Title = {Recommissioning of Duke Storage Ring with a HOM-Damped RF
Cavity and a New Straight Section Lattice for
FELs},
Journal = {Proceedings of Particle Accelerator Confernece 2005,
Knoxville, TN, 2005},
Pages = {3934-3936},
Year = {2005},
Month = {May},
Abstract = {The Duke FEL lab operates a unique UV/VUV storage ring FEL
and an FEL driven nearly monochromatic, highly polarized,
high intensity Compton gamma-ray source. The Duke storage
ring light source is undergoing several phases of upgrade in
order to significantly improve its light source capabilities
and performance. The recent upgrade in 2004 included an
upgrade of the RF system with a high-order mode damped RF
cavity and a new 34 meter long straight section lattice
designed to host new FEL wigglers. This upgrade was
completed in August 2004, followed by the storage ring and
light source commissioning. This paper provides an overview
of this upgrade project and reports the commissioning
experience of the Duke storage ring and light
sources.},
Key = {fds43901}
}
@article{fds249330,
Author = {Tornow, W and Esterline, JH and Howell, CR and Karwowski, HJ and Kelley,
JH and Tonchev, AP and Li, J and Mikhailov, SF and Pinayev, IV and Wu, YK and Weisel, GJ and Witała, H},
Title = {Photon analyzing power for the three-body breakup of
3He at Eγ = 15.0 MeV},
Journal = {AIP Conference Proceedings},
Volume = {768},
Pages = {138-140},
Publisher = {AMER INST PHYSICS},
Editor = {KalantarNayestanaki, N and Timmermans, RGE and Bakker,
BLG},
Year = {2005},
Month = {May},
ISBN = {0-7354-0253-1},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.1932890},
Abstract = {Photon analyzing power for the three-body breakup of 3He has
been studied at Eγ = 15.0 MeV. The measurements were done
at the HIγS facility at Duke University. © 2005 American
Institute of Physics.},
Doi = {10.1063/1.1932890},
Key = {fds249330}
}
@article{fds249365,
Author = {Wu, YK and Li, J and Wu, J},
Title = {Anomalous Hollow Electron Beams in a Storage
Ring},
Journal = {Physical Review Letter},
Volume = {94},
Number = {13},
Pages = {134802},
Year = {2005},
Month = {April},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15903998},
Abstract = {This Letter reports the first observations of an anomalous
hollow electron beam in the Duke storage ring. Created by
exciting the single-bunch beam in a lattice with a negative
chromaticity, the hollow beam consists of a solid core
inside and a large ring outside. We report the detailed
measurements of the hollow beam phenomenon, including its
distinct image pattern, spectrum signature, and its
evolution with time. By capturing the postinstability
bursting beam, the hollow beam is a unique model system for
studying the transverse instabilities, in particular, the
interplay of the wakefield and the lattice nonlinearity. In
addition, the hollow beam can be used as a powerful tool to
study the linear and nonlinear particle dynamics in the
storage ring.},
Doi = {10.1103/physrevlett.94.134802},
Key = {fds249365}
}
@article{fds249384,
Author = {Feng, J and Forest, E and MacDowell, AA and Marcus, M and Padmore, H and Raoux, S and Robin, D and Scholl, A and Schlueter, R and Schmid, P and Stöhr, J and Wan, W and Wei, DH and Wu, Y},
Title = {An X-ray Photoemission Electron Microscope Using Electron
Mirror Aberration Corrector for the Study of Complex
Materials},
Journal = {Journal of Physics: Condensed Matter},
Volume = {17},
Number = {16},
Pages = {S1339-S1350},
Publisher = {IOP Publishing},
Year = {2005},
Month = {April},
url = {http://www.iop.org/EJ/abstract/0953-8984/17/16/005},
Abstract = {A new ultrahigh-resolution photoemission electron microscope
called PEEM3 is being developed at the advanced light source
(ALS). An electron mirror combined with a sophisticated
magnetic beam separator is used to provide simultaneous
correction of spherical and chromatic aberrations. Installed
on an elliptically polarized undulator beamline, PEEM3 will
be operated with very high spatial resolution and high flux
to study the composition, structure, electric and magnetic
properties of complex materials.},
Doi = {10.1088/0953-8984/17/16/005},
Key = {fds249384}
}
@article{fds249381,
Author = {Schmid, P and Feng, J and Padmore, H and Robin, D and Rose, H and Schlueter, R and Wan, W and Forest, E and Wu, Y},
Title = {Correction and alignment strategies for the beam separator
of the photoemission electron microscope 3
(PEEM3)},
Journal = {Rev. Sci. Instrum.},
Volume = {76},
Number = {2},
Pages = {023302-023302},
Publisher = {AIP Publishing},
Year = {2005},
Month = {February},
ISSN = {0034-6748},
url = {http://dx.doi.org/10.1063/1.1841871},
Abstract = {A high-resolution aberration-corrected photoemission
electron microscope (PEEM3) will be installed on an
undulator beamline at the Advanced Light Source at the
Lawrence Berkeley National Laboratory. The aim of this
instrument is to provide a substantial flux and resolution
improvement by employing an electron mirror for correcting
both the third-order spherical aberration and the primary
chromatic aberration. In order to utilize this concept of
correction, a beam separator is a prerequisite. Crucial to
achieving a resolution of 5 nm for the high-resolution mode,
and a 16-fold increase in throughput at the same resolution
as its predecessor, PEEM2, specified as 20 nm at 2%
transmission, for the high flux mode is the double-symmetric
design of the beam separator, which eliminates all the
second-order geometric aberrations. Nonetheless, substantial
tuning capabilities must be incorporated into the PEEM3
design to compensate for both systematic and random errors.
In this article, we investigate how to correct for
nonsystematic imperfections and for systematic uncertainties
in the accuracy of the magnetic fields and focus on how
degradation of the resolution and the field of view can be
minimized. Finally, we outline a tentative correction
strategy for PEEM3. © 2005 American Institute of
Physics.},
Doi = {10.1063/1.1841871},
Key = {fds249381}
}
@article{fds376416,
Author = {Tornow, W and Esterline, JR and Howell, CR and Karwowski, HJ and Kelley,
JH and Tonchev, AP and Li, J and Mikhailov, SF and Pinayev, IV and Wu, YK and Weisel, GJ and Witala, H},
Title = {Photon analyzing power for the three-body breakup of He-3 at
E-gamma=15.0 MeV},
Journal = {Few-Body Problems in Physics},
Volume = {768},
Pages = {138-140},
Publisher = {AMER INST PHYSICS},
Year = {2005},
Month = {January},
Key = {fds376416}
}
@article{fds44056,
Author = {Vaclav Vylet and Patrick W. Wallace and Y. K.
Wu},
Title = {Towards the Top-off Mode at the Duke Free Electron Laser
Laboratory},
Journal = {JASRI/SPring-8 Report A 2005-02, Proceedings of the 3rd
workshop on radiation safety of synchrotron radiation
sources},
Year = {2005},
Key = {fds44056}
}
@article{fds249382,
Author = {Tonchev, AP and Boswell, M and Howell, CR and Karwowski, HJ and Kelley,
JH and Tornow, W and Wu, YK},
Title = {The high intensity gamma-ray source HIGS and recent
measurements},
Journal = {Nucl. Instr. Methods B.},
Volume = {241},
Number = {1-4},
Pages = {170-175},
Year = {2005},
ISSN = {0168-583X},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000234260000039&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The high intensity γ-ray source (HIγS) utilizes
intra-cavity backscattering of free electron laser photons
from the Duke electron storage ring to produce a unique
monoenergetic beam of high-flux γ-rays with high
polarization and selectable energy resolution. At present,
γ-ray beams with energies from 2 to 58 MeV are
available with intensities as high as 105–5 × 106
γ/s, energy spreads of 3% or better, and nearly 100%
linear polarization. The quality and intensity of the
γ-ray beams at HIγS are responsible for the
unprecedented performance of this facility in a broad range
of research programs in nuclear structure, nuclear
astrophysics and nuclear applications. Recent results from
excitation of isomeric states in (γ, n) reactions and
parity assignments of dipole states determined via the
(γ, γ′) reaction are presented.},
Doi = {10.1016/j.nimb.2005.07.080},
Key = {fds249382}
}
@article{fds360691,
Author = {Li, J and Wu, YK and Sun, C},
Title = {Improved long radius of curvature measurement system for FEL
mirrors},
Journal = {2005 IEEE PARTICLE ACCELERATOR CONFERENCE (PAC), VOLS
1-4},
Pages = {1494-1496},
Year = {2005},
ISBN = {0-7803-8859-3},
Key = {fds360691}
}
@article{fds360692,
Author = {Wu, YK and Li, J and Wu, J},
Title = {Observations and measurements of anomalous hollow electron
beams in the Duke storage ring},
Journal = {2005 IEEE PARTICLE ACCELERATOR CONFERENCE (PAC), VOLS
1-4},
Pages = {1012-1014},
Year = {2005},
ISBN = {0-7803-8859-3},
Key = {fds360692}
}
@article{fds360693,
Author = {Arbuzov, VS and Bushuev, A and Gavrilov, N and Gorniker, EI and Kenjebulatov, E and Kholopov, MA and Kondakov, AA and Krutikhin, SA and Kruchkov, YG and Kuptsov, IV and Kurkin, GY and Mironenko, LA and Mityanina, N and Motygin, SV and Osipov, VN and Petrov, V and Pilan, AM and Popov, AM and Rotov, E and Sedlyarov, I and Tribendis, AG and Volkov, V and Wang, P and Mikhailov, S and Wallace, PW and Wu, YK},
Title = {Commissioning of the new RF system with the HOM damped RF
cavity},
Journal = {2005 IEEE PARTICLE ACCELERATOR CONFERENCE (PAC), VOLS
1-4},
Pages = {4182-4183},
Year = {2005},
ISBN = {0-7803-8859-3},
Key = {fds360693}
}
@article{fds360694,
Author = {Popov, VG and Hartman, S and Mikhailov, SF and Oakeley, O and Wallace,
P and Wu, YK},
Title = {3 KA power supplies for the duke OK-5FEL
wigglers},
Journal = {2005 IEEE PARTICLE ACCELERATOR CONFERENCE (PAC), VOLS
1-4},
Pages = {4001-4003},
Year = {2005},
ISBN = {0-7803-8859-3},
Key = {fds360694}
}
@article{fds360695,
Author = {Popov, VG and Hartman, SM and Mikhailov, SF and Oakely, O and Wallace,
P and Wu, YK},
Title = {Trim power supplies for the duke booster and storage
ring},
Journal = {2005 IEEE PARTICLE ACCELERATOR CONFERENCE (PAC), VOLS
1-4},
Pages = {4004-4006},
Year = {2005},
ISBN = {0-7803-8859-3},
Key = {fds360695}
}
@article{fds360696,
Author = {Steier, C and Robin, D and Decking, W and Laskar, J and Nadolski, L and Wu,
Y},
Title = {Measuring and understanding the momentum aperture in a
storage ring},
Journal = {2005 IEEE PARTICLE ACCELERATOR CONFERENCE (PAC), VOLS
1-4},
Pages = {3807-3811},
Year = {2005},
ISBN = {0-7803-8859-3},
Key = {fds360696}
}
@article{fds360697,
Author = {Kurkin, G and Pinaev, I and Hartman, S and Mikhailov, S and Wu,
Y},
Title = {A new timing system for the Duke booster and storage
ring},
Journal = {2005 IEEE PARTICLE ACCELERATOR CONFERENCE (PAC), VOLS
1-4},
Pages = {469-470},
Year = {2005},
ISBN = {0-7803-8859-3},
Key = {fds360697}
}
@article{fds249386,
Author = {Fransen, C and Pietralla, N and Tonchev, AP and Ahmed, MW and Chen, J and Feldman, G and Kneissl, U and Li, J and Litvinenko, V and Perdue, B and Pinayev, IV and Pitz, HH and Prior, RM and Sabourov, K and Spraker, M and Tornow, W and Weller, HR and Werner, V and Wu, YK and Yates,
SW},
Title = {Parity Assignments to Strong Dipole Excitations of 92Zr and
96Mo},
Journal = {Physical Review},
Volume = {C70},
Number = {4},
Pages = {044317},
Publisher = {American Physical Society (APS)},
Year = {2004},
Month = {December},
ISSN = {0556-2813},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000225043100035&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {Parity quantum numbers for dipole-excited states of the
nuclei 92Zr and 96Mo have been determined from azimuthal
asymmetries of nuclear resonance fluorescence intensities
induced with the linearly polarized photon beam of the HIγS
facility at Duke University. This parity information is
crucial for an interpretation of the investigated J= 1
states as two-phonon excitations originating from
inhomogeneous phonon coupling.},
Doi = {10.1103/PhysRevC.70.044317},
Key = {fds249386}
}
@article{fds292652,
Author = {Feng, J and MacDowell, AA and Duarte, R and Doran, A and Forest, E and Kelez, N and Marcus, M and Munson, D and Padmore, H and Petermann, K and Raoux, S and Robin, D and Scholl, A and Schlueter, R and Schmid, P and Stöhr, J and Wan, W and Wei, DH and Wu, Y},
Title = {An Aberration Corrected Photoemission Electron Microscope at
the Advanced Light Source},
Journal = {AIP Conference Proceedings},
Volume = {705},
Pages = {1070-1073},
Publisher = {AIP},
Editor = {T.Warwick, J.Arthur and H.PAdmore, J.Stohr},
Year = {2004},
Month = {May},
ISBN = {0735401799},
ISSN = {0094-243X},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000222089000263&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {Design of a new aberration corrected Photoemission electron
microscope PEEM3 at the Advanced Light Source is outlined.
PEEM3 will be installed on an elliptically polarized
undulator beamline and will be used for the study of complex
materials at high spatial and spectral resolution. The
critical components of PEEM3 are the electron mirror
aberration corrector and aberration-free magnetic beam
separator. The models to calculate the optical properties of
the electron mirror are discussed. The goal of the PEEM3
project is to achieve the highest possible transmission of
the system at resolutions comparable to our present PEEM2
system (50 nm) and to enable significantly higher
resolution, albeit at the sacrifice of intensity. We have
left open the possibility to add an energy filter at a later
date, if it becomes necessary driven by scientific need to
improve the resolution further.},
Doi = {10.1063/1.1757983},
Key = {fds292652}
}
@article{fds249385,
Author = {Wu, YK and Robin, DS and Forest, E and Schlueter, R and Anders, S and Feng,
J and Padmore, H and Wei, DH},
Title = {Design and analysis of beam separator magnets for third
generation aberration compensated PEEMs},
Journal = {Nuclear Instruments and Methods in Physics Research
A},
Volume = {519},
Number = {1-2},
Pages = {230-241},
Publisher = {Elsevier BV},
Year = {2004},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2003.11.160},
Abstract = {A state of the art X-ray photoemission electron microscope
(PEEM2) is operational at the Advanced Light Source at a
resolution of typically 50 nm for a range of chemical and
magnetic surface studies. A new microscope, PEEM3, is under
development with an aim of achieving a resolution of 5 nm
and more than an order of magnitude increase in transmission
at the nominal resolution of PEEM2. The resolution and ux
improvement is realized by providing geometric and chromatic
aberration compensations in the system using an electron
mirror and a beam separator magnet. The nearly
aberration-free design of the beam separator is critical to
the performance of third generation PEEMs. In this paper, we
present the optics design model, optimal operation
parameters, analyses of aberration impact, as well as the
mechanical alignment tolerance for PEEM3 separator
prototypes. In particular, we emphasize the importance of a
new semi-analytical approach to design complex charged
particle optics using the truncated power series algebra.
Because of its ability to compute high-order aberrations,
this approach allows systematic and comprehensive analyses
of any charged particle optics systems with analytical
electric and magnetic fields.},
Doi = {10.1016/j.nima.2003.11.160},
Key = {fds249385}
}
@article{fds249294,
Author = {Wan, W and Nishimura, H and Robin, D and Steier, C and Wu, Y and Forest,
E},
Title = {ID modeling at the ALS},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2249-2251},
Year = {2003},
Month = {Winter},
Abstract = {At the Advanced Light Source there are several projects
being proposed that will require high field insertion
devices. It is important that these devices do not
significantly impact the performance of the machine. In
particular they should not degrade the beam lifetime or
injection efficiency. It is known that high field devices
with large field roll off can impact the beam lifetime. It
is therefore important to model the effect of the insertion
devices including both transverse and longitudinal field
roll off. In this paper we present the result of tracking
studies using an explicit symplectic integrator with both
transverse and longitudinal field roll off. The simulations
show where sufficiently large field roll off will impact the
beam lifetime.},
Key = {fds249294}
}
@article{fds249295,
Author = {Wu, YK and Li, J and Wang, P and Litvinenko, V},
Title = {BPM and orbit correction systems at the Duke storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2479-2481},
Year = {2003},
Month = {Winter},
Abstract = {Stable and reliable storage ring operation critically
depends on the orbit stability. At Duke, an orbit stability
program is well under way to achieve the high level of orbit
performance necessary for reliable free electron laser (FEL)
and gamma-ray operation. Progress has been made to reduce
the current dependency of BPM readings via choice of cables
and band-pass filters. Beam based alignment has been carried
out to accurately determine the locations of quadrupole
centers. A global orbit correction system and a slow orbit
feedback system have been developed. Integrated with
operation, these systems have demonstrated the ability to
significantly improve the overall storage ring
performance.},
Key = {fds249295}
}
@article{fds249296,
Author = {Steier, C and Forest, E and Nadolski, L and Nishimura, H and Robin, D and Wan, W and Wu, Y and Zholents, A},
Title = {Accelerator physics challenges of the fs-slicing upgrade at
the ALS},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {397-399},
Publisher = {IEEE},
Year = {2003},
Month = {Winter},
url = {http://dx.doi.org/10.1109/pac.2003.1288934},
Abstract = {The goal of the Femtoslicing project at the ALS is to
provide 100-200 fs long pulses of soft and hard x-rays with
moderate flux and with a repetion rate of 10-40 kHz for
experiments concerning ultrafast dynamics in solid state
physics, chemistry and biology. The femtoslicing principle
employs a femtosecond laser beam to interact resonantly
(inverse FEL interaction) with the electron beam in the ALS.
The induced energy spread over the femtosecond duration is
converted to a transverse displacement by exploiting the
dispersion of the storage ring. The displaced femtosecond
electron pulse then radiates and produces femtosecond
synchrotron radiation. To achieve the necessary spatial
separation of the energy modulated slice from the rest of
the bunch, a sizeable local vertical dispersion bump in the
undulator used as radiator is required. This presents
challenges in terms of the nonlinear dynamics and control of
the vertical emittance.},
Doi = {10.1109/pac.2003.1288934},
Key = {fds249296}
}
@article{fds249297,
Author = {Mikhailov, S and Litvinenko, V and Busch, M and Emamian, M and Hartman,
S and Pinayev, I and Popov, V and Swift, G and Wallace, P and Wu, Y and Gavrilov, N and Matveev, Y and Shvedov, D and Vinokurov, N and Vobly,
P},
Title = {Status of the booster synchrotron for Duke FEL storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2273-2275},
Year = {2003},
Month = {Winter},
Abstract = {In this paper we present current status of the Booster
Synchrotron for the Duke FEL storage ring. The Booster which
is recently under design, fabrication and construction, will
provide full energy injection into the storage ring at
energy from 0.3 to 1.2 GeV. The Duke storage ring FEL (SR
FEL) operates in lasing mode with 193-700 nm wavelength
range. The geometry of the Duke SR FEL provides for
interacting head-on collision of e-beam and FEL photons.
This mode of operation is used to generate intense beams of
γ-rays from 2 MeV to about 200 MeV (currently from 2 MeV to
58 MeV). Generation of γ-rays with energy exceeding 20 MeV
causes the loss of electrons, which will be replaced by
injection from the Booster operating in a top-off mode. The
paper presents design and status for elements of magnetic
system and vacuum system, as well as design and parameters
of fast extraction kicker with 11 nS pulse duration. All
these element are designed and will be fabricated by Budker
Institute of Nuclear Physics, Novosibirsk,
Russia.},
Key = {fds249297}
}
@article{fds249298,
Author = {Wu, YK and Popov, VG and Hartman, S and Pinayev, I and Mikhailov, SF and Morcombe, P and Oakeley, O and Wallace, P and Wang, P and Litvinenko,
V},
Title = {Improving power supply performance for the Duke storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2},
Pages = {752-754},
Year = {2003},
Month = {Winter},
Abstract = {As part of the recent Duke storage ring hardware upgrade
(2001-2002), a power supply improvement program was put in
place to bring all major DC supplies to their
specifications. In carrying out this program, power supplies
have been modified, tuned, and thoroughly tested. In its
actual operation configuration, each power supply was
subject to extensive testing to determine its DC stability,
reproducibility and linearity, AC ripple and noise, and
ramping performance. As a result, all major DC supplies have
been improved to meet most important performance
specifications for 1 GeV operation.},
Key = {fds249298}
}
@article{fds249299,
Author = {Wu, YK and Li, J and Mikhailov, SF and Litvinenko,
V},
Title = {Nonlinear dynamics in the Duke storage ring with FEL
wigglers},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {391-393},
Publisher = {IEEE},
Year = {2003},
Month = {Winter},
url = {http://dx.doi.org/10.1109/pac.2003.1288932},
Abstract = {Single particle dynamics in the storage ring can be
significantly influenced by strong nonlinearities from long
and strong-field insertion devices. This paper reports our
preliminary results on the dynamics impact of the 24 m long
OK5 FEL in the Duke ring. Initial studies are performed
using an intermediate lattice with two OK5 wigglers. The
dynamic aperture is computed using a recently developed
symplectic wiggler integrator and the frequency map
technique, NAFF. We have observed significant dynamic
aperture reduction due to OK5 wigglers at lower beam
energies. We also report our preliminary findings on the
means to improve beam dynamics with wigglers.},
Doi = {10.1109/pac.2003.1288932},
Key = {fds249299}
}
@article{fds249300,
Author = {Wu, YK and Hartman, S and Mikhailov, SF},
Title = {A physics based control system for the Duke storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2482-2484},
Year = {2003},
Month = {Fall},
Abstract = {At the Duke FEL Lab, we have developed a new storage ring
control system in terms of the physics quantities of the
accelerator. Instead of controlling power supply currents in
Amperes, this system controls the effective focusing of
magnets. By directly controlling the physics quantities,
this control system allows tighter integration of the
physics model based high level controls with the EPICS based
low-level controls. EPICS events have been extensively used
to provide time synchronization during the energy and
lattice ramping. This new control system also facilitates
the implementation of multiple functions on shared control
channels. As a result, the physics based control system
simplifies many complex control tasks, improves the beam
stability during ramping, and facilitates machine studies.
With better understanding of the accelerator, it is possible
to fine tune this control system to present users with a
virtual accelerator whose operation is independent of the
ring energy.},
Key = {fds249300}
}
@article{fds249301,
Author = {Li, J and Wu, YK and Hartman, S},
Title = {Power supply performance monitoring and analysis using
operation data},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2270-2272},
Booktitle = {Proceedings of PAC2003},
Year = {2003},
Month = {Winter},
Abstract = {Magnet power supplies are critical components of a storage
ring. The performance of power supplies directly impacts the
stability and reliability of the storage ring operation.
There are several type of DC power supplies in Duke FEL
storage ring. The performance data of power supplies can be
collected in a non-interruptive manner by an EPICS archiver
or by a MATLAB program. MATLAB based tools have been
developed to analyze the power supply data collected during
the operation. Careful evaluation of data allows us to
identify a power supply with degraded performance and
provide a reference to perform preventive
maintenance.},
Key = {fds249301}
}
@article{fds249388,
Author = {Wu, YK and Forest, E and Robin, DS},
Title = {Explicit symplectic integrator for s-dependent static
magnetic field},
Journal = {Physical Review E},
Volume = {68},
Number = {68},
Pages = {046502},
Publisher = {The American Physical Society},
Year = {2003},
Month = {October},
ISSN = {1063-651X},
url = {http://link.aps.org/abstract/PRE/v68/e046502},
Abstract = {This paper reports our recent work on explicit symplectic
integration techniques for the charged particle motion in an
s-dependent static magnetic field. Using the extended phase
space, symplectic integrators can be developed for
Hamiltonians with or without the paraxial approximation
using either the space or time as an independent variable.
This work extends the successful element-by-element tracking
method for studying single-particle nonlinear dynamics to a
set of s-dependent magnetic elements. Important applications
of this work include the studies of the charged particle
dynamics in a storage ring with various insertion devices,
superconducting magnets, large aperture magnets with
significant fringe fields, and solenoid magnets in the
interaction region. Consequently, this work is expected to
make an impact on design and optimal operation of existing
and future light source rings and high energy physics
accelerators.},
Doi = {10.1103/physreve.68.046502},
Key = {fds249388}
}
@article{fds17523,
Author = {M.W. Ahmeda and G. Feldmana and b, V.N. Litvinenkoc and S.O. Nelsona and B.E. Norumd and B. Perduea and I.V. Pinayevc and B. Sawatzkyd and A.P.
Toncheva, Y. Wu and H.R. Weller},
Title = {Background reduction in FEL-generated g-ray beam experiments
using giant high-peakpower pulses},
Journal = {Nuclear Instruments and Methods in Physics Research
A},
Number = {516},
Pages = {440-444},
Year = {2003},
Month = {August},
Abstract = {A new method to eliminate beam-uncorrelated background in
photonuclear experiments has been developed at the High
Intensity Gamma-Ray Source (HIgS). Background suppression of
over 3 orders-of-magnitude has been achieved by using a gain
modulation technique to generate giant high-peakpower (GHPP)
pulses in the OK-4/ Duke storage ring FEL. The time
structure of these laser pulses was tuned so that their
duration was B100 ms; repeated every 50 ms: The associated
FEL photons were backscattered from 780 MeV electrons to
produce linearly polarized 40 MeV g-rays having the same
time structure as the FEL pulses. As an initial test of the
technique, a nearly background-free measurement of the
analyzing power in the Compton scattering reaction 16Oð~g;
gÞ16O was performed. r 2003 Elsevier B.V. All rights
reserved.},
Key = {fds17523}
}
@article{fds249387,
Author = {Ahmed, MW and Feldman, G and Litvinenko, VN and Nelson, SO and Norum,
BE and Perdue, B and Pinayev, IV and Sawatzky, B and Tonchev, AP and Wu, Y and Weller, HR},
Title = {Background reduction in FEL-generated gamma-ray beam
experiments using giant high-peak power pulses},
Journal = {Nuclear Instruments and Methods in Physics Research
A},
Volume = {516},
Number = {2-3},
Pages = {440-444},
Publisher = {Elsevier},
Year = {2003},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2003.08.166},
Abstract = {A new method to eliminate beam-uncorrelated background in
photonuclear experiments has been developed at the High
Intensity Gamma-Ray Source (HIγS). Background suppression
of over 3 orders-of-magnitude has been achieved by using a
gain modulation technique to generate giant high-peak power
(GHPP) pulses in the OK-4/ Duke storage ring FEL. The time
structure of these laser pulses was tuned so that their
duration was ∼100 μs, repeated every 50 ms. The
associated FEL photons were backscattered from 780 MeV
electrons to produce linearly polarized 40 MeV γ-rays
having the same time structure as the FEL pulses. As an
initial test of the technique, a nearly background-free
measurement of the analyzing power in the Compton scattering
reaction 16O(γ→,γ)16O was performed. © 2003 Elsevier
B.V. All rights reserved.},
Doi = {10.1016/j.nima.2003.08.166},
Key = {fds249387}
}
@article{fds249389,
Author = {Feng, J and Padmore, H and Wei, DH and Anders, S and Wu, Y and Scholl, A and Robin, D},
Title = {Modeling the acceleration field and objective lens for an
aberration corrected photoemission electron
microscope},
Journal = {Review of Scientific Instruments},
Volume = {73},
Number = {3},
Pages = {1514-1517},
Year = {2002},
Month = {December},
ISSN = {0034-6748},
url = {http://dx.doi.org/10.1063/1.1423631},
Abstract = {The modeling of the optical properties of the acceleration
field and objective lens of a photoemission electron
microscope (PEEM) is presented. Theory to calculate the
aberrations of the extraction field was derived, and
extended to include relativistic effects. An analysis of the
microscope's electron optical performance and aberrations
has been performed using an analytical model as well as a
ray tracing method. Ray tracing has the flexibility needed
for the assessment of aberrations where the geometry is too
complex for analytical methods. This work shows that in the
case of a simple PEEM front end of the acceleration gap and
objective lens, the all orders ray tracing and full
analytical treatments agree to very high precision. This
allows us now to use the ray tracing method in situations
where analytical methods are difficult, such as an
aberration compensating electron mirror.},
Doi = {10.1063/1.1423631},
Key = {fds249389}
}
@article{fds249367,
Author = {Steier, C and Robin, D and Nadolski, L and Decking, W and Wu, Y and Laskar,
J},
Title = {Measuring and optimizing the momentum aperture in a particle
accelerator},
Journal = {Phys. Rev. E},
Volume = {65},
Number = {5 Pt 2},
Pages = {056506},
Year = {2002},
Month = {May},
ISSN = {1539-3755},
url = {http://dx.doi.org/10.1103/physreve.65.056506},
Abstract = {Particle motion in storage rings is confined by various
aperture limits, the size of which restricts the performance
of the ring in terms of injection efficiency, lifetime, etc.
Intrabeam scattering makes particles sweep a large portion
of the phase space, where their motion may eventually be
resonantly or chaotically excited to large amplitudes
leading to collision with the vacuum chamber. We report here
the studies performed at the Advanced Light Source (ALS) on
the on- and off-momentum particle motion that provides a
good understanding of these limitations. Using off-momentum
simulations and experiments together with frequency map
analysis, we could precisely correlate beam loss areas with
resonance locations. The very good agreement between
simulations and experiments allowed us to provide guidance
for avoiding these dangerous areas. This analysis results in
predictive improvements of the momentum aperture, which
actually led to a lifetime increase of 25% at the ALS for
very high bunch charge.},
Doi = {10.1103/physreve.65.056506},
Key = {fds249367}
}
@article{fds249390,
Author = {Wu, Y and Nishimura, H and Robin, DS and Zholents, AA and Forest,
E},
Title = {Mini-beta lattice for the femto-second X-ray source at the
Advanced Light Source},
Journal = {Nuclear Instruments and Methods in Physics Research, Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {481},
Number = {1-3},
Pages = {675-681},
Publisher = {Elsevier BV},
Year = {2002},
Month = {April},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01353-5},
Abstract = {After generating the first femto-second X-ray pulses at the
Advanced Light Source (ALS), it becomes critical to improve
the flux of this femto-second source for user experiments. A
narrow-gap in-vacuum undulator has been proposed to be
installed in one of the ALS straight sections. To realize
the optimal performance of this undulator, a straight
section lattice with a mini vertical beta function has been
designed. Separation of electrons has been achieved by
generating a sizable vertical dispersion via a local
dispersion bump and a closed orbit bump. Particle tracking
study shows that the modified ALS lattice for the
femto-second X-ray source has an adequate dynamic aperture.
© 2002 Published by Elsevier Science B.V.},
Doi = {10.1016/S0168-9002(01)01353-5},
Key = {fds249390}
}
@article{fds249282,
Author = {Wu, Y and Forest, E and Robin, DS and Nishimura, H and Wolski, A and Litvinenko, VN},
Title = {Symplectic models for general insertion devices},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {459-461},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {A variety of insertion devices (IDs), wigglers and
undulators, linearly or elliptically polarized, are widely
used as high brightness radiation sources at the modern
light source rings. Long and high-field wigglers have also
been proposed as the main source of radiation damping at
next generation damping rings. As a result, it becomes
increasingly important to understand the impact of IDs on
the charged particle dynamics in the storage ring. In this
paper, we report our recent development of a general
explicit symplectic model for IDs with the paraxial ray
approximation. High-order explicit symplectic integrators
are developed to study real-world insertion devices with a
number of wiggler harmonics and arbitrary
polarizations.},
Key = {fds249282}
}
@article{fds249283,
Author = {Steier, C and Atkinson, D and Byrd, J and Corlett, J and Nishimura, H and Robin, D and De Santis and S and Wolski, A and Wu, Y and Bane, K and Raubenheimer, T and Ross, M and Sheppard, J and Smith,
T},
Title = {Intra-beam scattering and minimum achievable emittance in
the advanced light source},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2938-2940},
Year = {2001},
Month = {December},
Abstract = {Intra-beam scattering (IBS) potentially limits the minimum
emittance of low-energy storage rings, and this effect
strongly influences the choice of energy of damping rings
for linear colliders. The Advanced Light Source (ALS) is a
third-generation synchrotron light source operating with
high-intensity, low-emittance beams at energies up to 2 GeV.
It can operate with an emittance coupling of below 1%. We
present measurements of the beam growth in three dimensions
as a function of current, for normalized natural horizontal
emittances of approximately 1 - 10 mm-mrad at energies of
0.7 - 1.5 GeV, values comparable to the parameters in an NLC
damping ring. Using a dedicated diagnostic beamline with an
x-ray scintillator imaging system, measurements of the
transverse beamsize are made, simultaneously with bunch
length measurements using an optical streak camera. The
bunch volume growth as a function of bunch current is
compared with theoretical estimates, for a parameter space
of IBS, where very little experimental data exists so
far.},
Key = {fds249283}
}
@article{fds249284,
Author = {Steier, C and Biocca, A and Domning, E and Jacobson, S and Portmann, G and Wu, Y},
Title = {Design of a fast global orbit feedback system for the
Advanced Light Source},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2},
Pages = {1252-1254},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {The fast stability of the closed orbit of the electron beam
at the Advanced Light Source (ALS) at Lawrence Berkeley
National Laboratory fulfills user requirements so far
without any fast active correction system. In the range
between 0.1 and 500 Hz the integrated rms closed orbit
motion is significantly below one tenth of one sigma
beamsizes. For the future there is some user demand to
improve this stability further. Moreover, the expansion of
the capabilities of the ALS creates new sources of closed
orbit noise. Therefore the design of a fast, global orbit
feedback system has been started in conjunction with a
general upgrade of the ALS control system. It will initially
operate with an update rate of 500 Hz - 1 kHz, will include
24 beam position monitors and corrector magnets in each
plane and will use standard computer and networking
architecture. The system design, measurements of transfer
functions and tests with small prototype systems will be
presented.},
Key = {fds249284}
}
@article{fds249285,
Author = {Shevchenko, OA and Litvinenko, VN and Mikhailov, SM and Vinokurov,
NA and Gavrilov, NG and Vobly, PD and Wu, Y},
Title = {The VUV/UV OK-5 Duke storage ring FEL with variable
polarization},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2833-2835},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {We discuss the design and expected performance of the OK-5
FEL, which will replace in 2002 the OK-4 FEL operating now
at the Duke storage ring. The OK-5 FEL is the first
distributed optical klystron with variable polarization. The
design of wigglers and matching sections is flexible for
providing optimal conditions for variety of operation modes.
In this paper we present calculations of the main OK-5 FEL
parameters such as its tuning range, gain and lasing power.
Based on our calculations we present the predictions for the
OK-5 gamma-ray source. We conclude with description of the
current status of the OK-5 FEL and plans for its
installation.},
Key = {fds249285}
}
@article{fds249286,
Author = {Steier, C and Robin, D and Wu, Y and Decking, W and Laskar, J and Nadolski,
L},
Title = {Understanding the dynamic momentum aperture of the advanced
light source},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {434-436},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {The lifetime of a light source with small emittance like the
Advanced Light Source (ALS) is usually limited by the
momentum acceptance of the ring. Large momentum acceptances
are reached by providing enough RF voltage and by avoiding a
degradation of the dynamic momentum aperture. At the ALS the
size of the momentum acceptance depends strongly on the
transverse dynamics. It is very sensitive to machine
conditions such as the tunes and chromaticities since
depending on those conditions the Touschek scattered
particles explore different resonance regions in the phase
space. In this paper we show that by using a single-turn
'pinger' magnet together with turn-by-turn beam position
monitors (BPM) one can identify the cause of a reduction in
momentum acceptance and take steps to improve the
acceptance.},
Key = {fds249286}
}
@article{fds249287,
Author = {Wolski, A and Wu, Y},
Title = {Effects of damping wigglers on beam dynamics in the NLC
damping rings},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {5},
Pages = {3798-3800},
Booktitle = {EFFECTS OF DAMPING WIGGLERS ON BEAM DYNAMICS Proceedings of
the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {To achieve the required damping time in the main damping
rings for the Next Linear Collider (NLC), a wiggler will be
required in each ring with integrated squared field strength
up to 110 T2m. There are concerns that nonlinear components
of the wiggler field will damage the dynamic aperture of the
ring, leading to poor injection efficiency. Severe effects
from an insertion device have been observed and corrected in
SPEAR 2. In this paper, we describe a model that we have
developed to study the effects of the damping wiggler,
compare the predictions of the model with actual experience
in the case of the SPEAR 2 wiggler, and consider the
predicted effects of current damping wiggler design on the
NLC main damping rings.},
Key = {fds249287}
}
@article{fds249288,
Author = {Hartman, S and Litvinenko, VN and Swift, G and Pinayev, I and Wu,
Y},
Title = {Control system design and upgrade considerations for the
Duke Free Electron Laser Laboratory},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2},
Pages = {785-787},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicag},
Year = {2001},
Month = {December},
Abstract = {The Duke Free Electron Laser Laboratory currently operates
two FELs: the OK-4/Duke Storage Ring FEL, and the Mark III
IR FEL. Both of these systems were among the early adopters
of the Experimental Physics and Industrial Control System
(EPICS). The Mark III EPICS control system was completed and
operational in September, 1993. The Duke Storage Ring was
commissioned in November of 1994 using EPICS. These control
systems have proven to be very robust with high reliability
over the intervening years. An overview of these current
control systems and an upgrade strategy will be
presented.},
Key = {fds249288}
}
@article{fds249289,
Author = {Mikhailov, SF and Litvinenko, VN and Wu, Y},
Title = {Low emittance lattices for the Duke FEL Storage
Ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {5},
Pages = {3528-3530},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {In this paper we present two options for a new lattice of
the I GeV Duke FEL Storage Ring reducing horizontal beam
emittance from existing 18 nm*rad to 1.4 nm*rad and 0.9
nm*rad respectively. One of proposed lattices reuses
existing magnetic elements, another is based on completely
new design. The use of combined function magnets with
dipole, quadrupole and sextupole components allows us to
keep the ring compact and fit it into existing footprint. 2D
and 3D field simulations for such a magnet showed good
quality of magnetic field. Preliminary results for dynamic
aperture simulations are also presented. We also discuss the
choice of lattice cell and tune advances and the concept of
local compensation of nonlinear aberrations.},
Key = {fds249289}
}
@article{fds249290,
Author = {Barry, W and Biocca, A and Byrd, JM and Byrne, W and Kwiatkowski, S and Martin, MC and McKinney, WR and Nishimura, H and Sannibale, F and Steier, C and Rex, K and Robin, D and Stover, G and Thur, W and Wu,
Y},
Title = {A dedicated infrared synchrotron radiation source at the
ALS},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2623-2625},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {We present ideas for a storage ring dedicated to and
optimized for the production of synchrotron radiation over
the infrared wavelength range from 1-1000 μm. The site for
the 66 m circumference ring is atop the existing ALS booster
synchrotron shielding. This area provides enough floor space
for both the ring and beamlines, and hutches. We plan to
operate the ring in two modes: as a conventional light
source and as a superradiant source in the far-IR. In the
conventional mode, our design allows greater transmission of
light at longer wavelengths in the far-infrared than typical
light sources and significantly improves beam stability. In
the superradiant mode, we hope to achieve coherent emission
of synchrotron radiation over the 200-1000 μm wavelength
range by shortening the bunches at very low bunch
current.},
Key = {fds249290}
}
@article{fds249291,
Author = {Litvinenko, VN and Shevchenko, OA and Mikhailov, SF and Wu,
Y},
Title = {Project for generation of femtosecond X-ray beams from the
Duke storage ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2614-2616},
Booktitle = {Proceedings of the 2001 Particle Accelerator Conference,
Chicago},
Year = {2001},
Month = {December},
Abstract = {We propose to develop a CW X-ray femtosecond (fsec) source
at 1.2 GeV Duke storage ring with the X-ray energy tuneable
from 1.4 KeV to 75 keV, the average flux from 1012 to 1013
ph/sec, and the average spectral brightness up to 0.51015
ph/sec/mm2/mrad2/0.1%BW. A novel RF system with strong
longitudinal focusing will compress and to sustain the
electron bunches circulating in the ring to a RMS duration
from 15 to 85 fsec. The CW fsec electron bunches will
generate the Compton hard-X-ray beams and the photon beams
from the existing light sources ranging form IR to VUV.
Beams of all colours will be synchronised by the e-beam
without jitter, making this configuration perfectly suites
for pump-probe experiments. The proposed approach promises
to outperform the popular "slicing technique" by at least
three orders of magnitude. Duke's approach can be
implemented at existing light source facilities at modest
cost.},
Key = {fds249291}
}
@article{fds249369,
Author = {Litvinenko, VN and Park, SH and Pinayev, IV and Wu,
Y},
Title = {Operation of the OK-4/Duke storage ring FEL below 200
nm},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {475},
Number = {1-3},
Pages = {195-204},
Publisher = {Elsevier BV},
Year = {2001},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01559-5},
Abstract = {For a number of years the wavelength of 200 nm was a
psychological barrier for FEL oscillators. The progress
towards short wavelength was marginal since the OK-4/VEPP-3
storage ring FEL lased at 240 nm in 1988. After 10 years, in
1998, the OK-4/Duke FEL and the NIJI-IV FEL group moved the
limit to 217 and 212 nm, respectively. Improvements of the
OK-4/Duke storage ring FEL gain above 10% and the use of
custom manufactured mirror coatings brought the success in
August 1999. The OK-4 FEL lased in the range from 193.7 to
209.8 nm using electron energies from 500 to 800 MeV. In
this paper, we present the description of the OK-4/Duke FEL
up-grades and the lasing results below 200 nm obtained in
August and October of 1999.},
Doi = {10.1016/S0168-9002(01)01559-5},
Key = {fds249369}
}
@article{fds249370,
Author = {Litvinenko, VN and Park, SH and Pinayev, IV and Wu,
Y},
Title = {Time structure of the OK-4/Duke storage ring
FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {475},
Number = {1-3},
Pages = {240-246},
Publisher = {Elsevier BV},
Year = {2001},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01569-8},
Abstract = {n this paper, we present results of experimental and
theoretical studies of macro- and micro-temporal of dynamics
of the OK-4/Duke storage ring FEL (SR FEL) and electron
beams. The experimental part of these studies utilized the
Hamamatsu C5680 dual-sweep streak-camera with 1.2 ps
resolution. We use both numerical and analytical tools for
theoretical analysis of the FEL and e-beam distributions
without any pre-imposed limitations. Our experimental
results are in good agreement with the theoretical
predictions.},
Doi = {10.1016/S0168-9002(01)01569-8},
Key = {fds249370}
}
@article{fds249383,
Author = {Litvinenko, VN and Park, SH and Pinayev, IV and Wu, Y and Lumpkin, A and Yang, B},
Title = {Fourier limited micro-pulses in the OK-4/Duke storage ring
FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {475},
Number = {1-3},
Pages = {234-239},
Publisher = {Elsevier BV},
Year = {2001},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01570-4},
Abstract = {The Super-modes are Fourier limited FEL micro-pulses
predicted by Dattoli and Renieri in 1980. The OK-4 FEL at
Duke, operating in the wavelength range from 193.7 nm to 730
nm, was the first to observe the Super-modes in a storage
ring FEL in 1996. Since 1996, the up-graded diagnostics and
improved control of the RF frequency allowed generation of
Super-modes on a regular basis and systematic study of them.
The Gaussian FEL micro-pulses with 1.3 ps RMS duration and
Fourier limited RMS linewidth were generated in 1998-1999.
In this paper we present the results of our studies and the
comparison with theoretical predictions. We also present
practical criteria for operating SR FELs with
Super-modes.},
Doi = {10.1016/S0168-9002(01)01570-4},
Key = {fds249383}
}
@article{fds249391,
Author = {Litvinenko, VN and Park, SH and Pinayev, IV and Wu,
Y},
Title = {Power limitations in the OK-4/Duke storage ring
FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {475},
Number = {1-3},
Pages = {65-73},
Publisher = {Elsevier BV},
Year = {2001},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01536-4},
Abstract = {n this paper, we present results of our experimental and
theoretical studies of average power in the OK-4/Duke
storage ring FEL. Our theoretical studies are based on the
3D FEL macro-particle model, which includes the local
interactions, diffusion, radiation damping and spontaneous
radiation. The OK-4/Duke storage ring FEL is operational
since 1996 and demonstrated lasing in a wavelength range
from 193.7 to 730 nm using electron beam energies from 220
to 800 MeV. It operated in both CW and giant pulse modes.
During this period of time we collected substantial amounts
of data regarding the FEL power and electron beam dynamics.
We compare selected results on CW lasing with our
theoretical predictions based on the rigorous numerical
model. We also discuss a number of simplified scaling laws
for the FEL gain and power as functions of electron beam
energy and current, as well as, the cavity
losses.},
Doi = {10.1016/S0168-9002(01)01536-4},
Key = {fds249391}
}
@article{fds249392,
Author = {Wu, Y and Litvinenko, VN and Mikhailov, SF and Shevchenko, OA and Vinokurov, NA and Gavrilov, NG and Shaftan, TV and Kairan,
DA},
Title = {Lattice modification and nonlinear dynamics for elliptically
polarized VUV OK-5 FEL source at Duke storage
ring},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {475},
Number = {1-3},
Pages = {253-259},
Publisher = {Elsevier BV},
Year = {2001},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01567-4},
Abstract = {The Duke storage ring is a light source ring optimized for
driving the Free Electron Lasers (FELs). To take advantage
of the high brightness of the electron beam in the storage
ring, a next generation FEL source -- an elliptically
polarized OK-5 FEL system, has been designed to match the
electron beam quality of the Duke storage ring. In this
paper, we present the storage ring lattice modifications
which are necessary to accommodate the 24 m long OK-5 FEL.
Because of its length and strong nonlinear focusing, the
OK-5 FEL is expected to have a significant impact on the
electron beam dynamics. We also present the preliminary
results on the dynamic aperture calculation for the OK-5 FEL
operated in different modes.},
Doi = {10.1016/S0168-9002(01)01567-4},
Key = {fds249392}
}
@article{fds249393,
Author = {Litvinenko, VN and Mikhailov, SF and Shevchenko, OA and Vinokurov,
NA and Gavrilov, NG and Kulipanov, GN and Shaftan, TV and Vobly, PD and Wu,
Y},
Title = {The OK-5/Duke storage ring VUV FEL with variable
polarization},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {475},
Number = {1-3},
Pages = {407-416},
Publisher = {Elsevier BV},
Year = {2001},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01548-0},
Abstract = {The OK-5/Duke storage ring free electron laser (FEL) project
was started in 1998. Presently, the components of the OK-5
FEL and the new South straight section are in the final
stage of manufacturing. This paper describes the design and
the main features of the OK-5/Duke storage ring FEL. The
basic concepts and main compromises made in the design
process are presented. Plans for the OK-5 FEL commissioning
are discussed.},
Doi = {10.1016/S0168-9002(01)01548-0},
Key = {fds249393}
}
@article{fds249394,
Author = {Mikhailov, SF and Litvinenko, VN and Wu, Y},
Title = {Low emittance lattice for the Duke storage ring soft X-ray
FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {475},
Number = {1-3},
Pages = {417-424},
Publisher = {Elsevier BV},
Year = {2001},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01636-9},
Abstract = {In this paper, we present a possible lattice for the Duke
storage ring with horizontal emittance of 1.4 nm rad at an
energy of 1 GeV. The new lattice was constrained to fit the
layout of the existing storage ring and to re-use existing
magnets. Within these constrains, the improvement of the
emittance (from current 18 nm rad) is possible due to the
use in the arcs of combined function bending magnets with
strong dipole, quadrupole and sextuple fields. We present
the results of 2D and 3D simulations of magnetic fields for
these magnets. We discuss the choice of the arc's lattice
cell and the per-cell tune advance. The lattice is based on
the concept of local compensation of the non-linear
geometrical aberrations. Preliminary studies of the dynamic
aperture for this lattice are very encouraging. We briefly
discuss the possibility further emittance reduction using
new magnets for the arcs.},
Doi = {10.1016/S0168-9002(01)01636-9},
Key = {fds249394}
}
@article{fds249292,
Author = {Pinayev, IV and Litvinenko, VN and Hee Park and S and Wu, Y and Emamian, M and Hower, N and Patterson, J and Swift, G},
Title = {Giant high-peak power pulses in the UV OK-4/Duke storage
ring FEL using the gain modulator},
Journal = {Nuclear Instruments and Methods in Physics Research, Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {475},
Number = {1-3},
Pages = {222-228},
Publisher = {Elsevier BV},
Year = {2001},
Month = {November},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01572-8},
Abstract = {We use the gain modulation technique to generate giant
pulses in the OK-4/Duke storage ring FEL for applications
requiring high peak power. This technique provides the
increase of the peak power by several orders of magnitude.
It is also very reliable, predictable and reproducible. The
design, the parameters and the gain modulator performance
are described. Comparison of expected and measured pulse
forms is presented. Application of gain modulator for future
harmonic generation experiments is also discussed. © 2001
Elsevier Science B.V. All rights reserved.},
Doi = {10.1016/S0168-9002(01)01572-8},
Key = {fds249292}
}
@article{fds4263,
Author = {C. Steier and D. Atkinson and J. Byrd and J. Corlett and H. Nishimura and D. Robin and S. de Santis},
Title = {INTRA-BEAM SCATTERING AND MINIMUM ACHIEVABLE},
Pages = {2938-2940},
Booktitle = {INTRA-BEAM SCATTERING AND MINIMUM ACHIEVABLE},
Year = {2001},
Month = {June},
Abstract = {Intra-beam scattering (IBS) potentially limits the mini-mum
emittance of low-energy storage rings, and this ef-fect
strongly influences the choice of energy of damping rings
for linear colliders. The Advanced Light Source (ALS) is a
third-generation synchrotron light source oper-ating with
high-intensity, low-emittance beams at energies up to 2 GeV.
It can operate with an emittance coupling of below 1%. We
present measurements of the beam growth in three dimensions
as a function of current, for normal-ized natural horizontal
emittances of approximately 1 - 10 mm-mrad at energies of
0.7 - 1.5 GeV, values compara-ble to the parameters in an
NLC damping ring [1]. Using a dedicated diagnostic beamline
with an x-ray scintillator imaging system, measurements of
the transverse beamsize are made, simultaneously with bunch
length measurements using an optical streak camera. The
bunch volume growth as a function of bunch current is
compared with theoretical estimates, for a parameter space
of IBS, where very little experimental data exists so
far.},
Key = {fds4263}
}
@article{fds17524,
Author = {J. H. Kelley and B. T. Crowley and V. N. Litvinenko and S.H. Park and I.V. Pinayev and E. C. Schreiber and W. Tornow and Y. Wu and H. R.
Weller},
Title = {High-Intensity y-ray Source},
Journal = {AIP Conference Proceedings},
Volume = {576},
Pages = {659},
Publisher = {American Institute of Physics},
Year = {2001},
Abstract = {A mono-energetic tunable source of 100% linearly polarized y
rays has been developed at the Duke Free- Electron Laser
Laboratory in conjunction with Triangle Universities Nuclear
Laboratory. The OK-4 PEL is coupled to a 1-GeV electron
storage ring and generates intense beams of visible or UV
photons. In y-ray production mode, the OK-4 photons Compton
scatter from high-energy electrons inside the optical cavity
leading to backscattered y rays. The strong correlation
between scattering angle and y-ray energy permits a
selection of the energy spread of the y-ray beam that
depends on a simple geometrical aperture located along the
optical axis. Results obtained/(design parameters) indicate
yray beams with energies of 2.2-587(2.0-175) MeV, AE/E<1.0%
and total fluxes greater than 107/(1010) y
rays/s.},
Key = {fds17524}
}
@article{fds292660,
Author = {Schreiber, EC and Canon, RS and Crowley, BT and Howell, CR and Kelley,
JH and Litvinenko, VN and Nelson, SO and Park, SH and Pinayev, IV and Prior, RM and Sabourov, K and Spraker, M and Tornow, W and Wu, Y and Wulf,
EA and Weller, HR},
Title = {First measurement of the near-threshold [Formula Presented]
analyzing power using a free-electron laser based [Formula
Presented]-ray source},
Journal = {Physical Review C - Nuclear Physics},
Volume = {61},
Number = {6},
Pages = {4},
Publisher = {American Physical Society (APS)},
Year = {2000},
Month = {January},
ISSN = {0556-2813},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000087575000005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The first measurement of the [Formula Presented] analyzing
power near threshold has been performed using the
High-Intensity Gamma-ray Source (HIGS) at the Duke
Free-Electron Laser Laboratory. A 3.58 MeV [Formula
Presented]-ray beam having an energy resolution of [Formula
Presented] and [Formula Presented] linear polarization was
incident on an active [Formula Presented] target. Outgoing
neutrons were detected parallel and perpendicular to the
plane of [Formula Presented]-ray polarization at a lab angle
of 150°. The experimentally determined analyzing power
provides a sensitive measurement of the relative [Formula
Presented] and [Formula Presented] contributions to the
total cross section. © 2000 The American Physical
Society.},
Doi = {10.1103/PhysRevC.61.061604},
Key = {fds292660}
}
@article{fds191709,
Author = {Y. Wu and H. Nishimura and D. S. Robin and A. A. Zholents and E.
Forest},
Title = {Mini-Beta Lattice for the Femto-Second X-Ray Source at the
Advanced Light Source},
Journal = {Proceedings of Seventh European Particle Accelerator
Conference (EPAC 2000)},
Pages = {1098-1100},
Year = {2000},
Abstract = {After generating the first femto-second X-ray pulses at the
Advanced Light Source (ALS), it becomes critical to improve
the flux of this femto-second source for user experiments. A
narrow-gap in-vacuum undulator has been proposed to be
installed in one of the ALS straight sections. To realize
the optimal performance of this undulator, a straight
section lattice with a mini vertical beta function has been
designed. Separation of electrons has been achieved by
generating a sizable vertical dispersion via a local
dispersion bump and a closed orbit bump. Particle tracking
study shows that the modified ALS lattice for the
femto-second x-ray source has an adequate dynamic
aperture.},
Key = {fds191709}
}
@article{fds249278,
Author = {Litvinenko, VN and Park, SH and Pinayev, IV and Wu, Y and Emamian, M and Hower, N and Morcombe, P and Oakeley, O and Swift, G and Wang,
P},
Title = {Deep-UV operation of the OK-4/Duke storage ring
FEL},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {221-223},
Year = {1999},
Month = {December},
Abstract = {In this paper we present the result of the deep-UV lasing
with the OK-4/Duke storage ring FEL. The OK-4 FEL was
initially commissioned in the near-UV at Duke Free Electron
Laboratory in November, 1996 followed by a year-long
shutdown. After re-establishing the storage ring operation
in early 1998, the OK-4 FEL lasing was demonstrated in the
wavelength range of 217 to 256 nm in 1998. A number of
lasing modes with electron energies ranging from 300 to 750
MeV have been established to accommodate application
research. Starting September, 1998, the coherent deep-UV
radiation is used for applications in cornea surgery, cell
biology, surface physics, and nuclear physics. In this paper
we report the results of the deep-UV lasing with the
OK-4/Duke storage ring FEL as well as our plans to advance
towards the VUV.},
Key = {fds249278}
}
@article{fds249279,
Author = {Morcombe, PH and Wu, Y and McGehee, R},
Title = {Temperature sensors and controls for the Duke FEL storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2},
Pages = {688-689},
Year = {1999},
Month = {December},
Abstract = {This paper describes a prototype system used for sensing and
control functions associated with the Duke University 1 GeV
electron storage ring. Low cost industrial control systems
have been used. The system is capable of handling at least
four hundred devices.},
Key = {fds249279}
}
@article{fds249280,
Author = {Pinayev, IV and Detweiler, G and Emamian, M and Hower, N and Johnson, M and Litvinenko, VN and Oakley, O and Park, SH and Patterson, J and Swift, G and Wu, Y},
Title = {Critical systems for high peak power storage ring
FEL},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2468-2470},
Year = {1999},
Month = {December},
Abstract = {The Duke storage ring is a facility dedicated for the deep
UV free electron laser (FEL) development. It is especially
designed for the high peak power applications, having a long
optical cavity and large energy acceptance. In this paper we
describe FEL gain modulator and optical cavity control
system, which are essential for obtaining maximal peak
power.},
Key = {fds249280}
}
@article{fds249281,
Author = {Wang, P and Hower, N and Litvinenko, V and Moallem, M and Oakeley, O and Swift, G and Wu, Y},
Title = {Beam position monitors for Duke FEL storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {3},
Pages = {2099-2101},
Year = {1999},
Month = {December},
Abstract = {The Duke FEL storage ring is a 1 Gev electron ring, which is
designed for driving UV-VUV free electron lasers. The ring
has been in operation since November of 1994 but the beam
position monitors (BPMs) were connected and operated just
recently. The BPM pick-ups are 4 stripline electrodes. In
order to reduce the higher-order-mode loss excited by the
stored beam at the BPM pick-up area, the BPM vacuum chamber
is designed with 4 grounding strips between the electrodes
that have the same diameters as the electrode. This design
allows the electron beam to see a much smoother vacuum
chamber at the BPM area. The pick-up signals are processed
by Bergoz's electronic modules, which give X/Y outputs
directly. Each BPM has its own process module and 34 modules
have been connected to the EPICS control system. The beam
orbit now can be displayed and corrected through EPICS in
the control room. The system performance and the test data
will be presented in this paper.},
Key = {fds249281}
}
@article{fds249395,
Author = {Litvinenko, VN and Park, SH and Pinayev, IV and Wu,
Y},
Title = {Performance of the OK-4/Duke storage ring
FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A:},
Volume = {470},
Number = {1-2},
Pages = {66-75},
Publisher = {Elsevier BV},
Year = {1999},
Month = {September},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(01)01025-7},
Abstract = {n this paper, we report measured parameters of the OK-4 FEL
driven by the Duke storage ring. The OK-4 FEL was being
operated continuously for 2 yr in the broad wavelength range
for user applications utilising spontaneous and coherent XUV
and UV radiation as well as Compton back-scattered -rays in
the range of 2-58 MeV. During this time, the OK-4 FEL lased
in the range from 193.7 to about 730 nm using five sets of
mirrors and electron beam energies from 240 to 800 MeV. Our
predictions for the OK-4 FEL are compared with measured
performance, both in the CW and in the giant pulse mode. We
discuss our future plans for the OK-4 FEL operation as well
as the construction and commissioning of the OK-5 FEL with
helical wigglers.},
Doi = {10.1016/S0168-9002(01)01025-7},
Key = {fds249395}
}
@article{fds249396,
Author = {Litvinenko, VN and Park, SH and Pinayev, IV and Wu, Y and Emamian, M and Hower, N and Morcombe, P and Oakeley, O and Swift, G and Wang,
P},
Title = {OK-4/Duke storage ring FEL lasing in the
deep-UV},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {429},
Number = {1},
Pages = {151-158},
Publisher = {Elsevier BV},
Year = {1999},
Month = {June},
ISSN = {0168-9002},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000081126900030&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {In this paper we present the result of the deep-UV lasing
with the OK-4/Duke storage ring FEL. The OK-4 FEL was
initially commissioned at Duke Free Electron Laboratory in
November 1996 followed by a yearlong shutdown. After
re-establishing the storage ring operation in early 1998,
the OK-4 FEL lasing was demonstrated in the wavelength range
of 226-256 nm in April 1998. The OK-4 FEL successfully lased
from 217 nm to 235 nm in August 1998. A number of lasing
modes with electron energies ranging from 300 to 750 MeV
have been established to accommodate application researches.
Starting September 1998, the coherent deep-UV radiation is
used for applications in surgery, cell biology, surface
physics, and nuclear physics.},
Doi = {10.1016/S0168-9002(99)00096-0},
Key = {fds249396}
}
@article{fds191710,
Author = {V. N. Litvinenko and S. H. Park and I. V. Pinayev and Y. Wu and M.
Emamian, N. Hower and P. Morcombe and O. Oakeley and G. Swift and P.
Wang},
Title = {The Deep-UV Operation of The OK-4/Duke Storage Ring
FEL},
Journal = {Proceedings of 1999 Particle Accelerator
Conference},
Pages = {221-223},
Year = {1999},
Abstract = {In this paper we present the result of the deep-UV lasing
with the OK-4/Duke storage ring FEL. The OK-4 FEL was
initially commissioned in the near-UV at Duke Free Electron
Laboratory in November, 1996 followed by a year-long
shutdown. After re-establishing the storage ring operation
in early 1998, the OK-4 FEL lasing was demonstrated in the
wavelength range of 217 to 256 nm in 1998. A number of
lasing modes with electron energies ranging from 300 to 750
MeV have been established to accommodate application
research. Starting September, 1998, the coherent deep-UV
radiation is used for applications in cornea surgery, cell
biology, surface physics, and nuclear physics. In this paper
we report the results of the deep-UV lasing with the
OK-4/Duke storage ring FEL as well as our plans to advance
towards the VUV.},
Key = {fds191710}
}
@article{fds249276,
Author = {Litvinenko, VN and Wu, Y and Burnham, B and Park, SH and Emamian, M and Faircloth, J and Goetz, S and Hower, N and Madey, JMJ and Meyer, J and Morcombe, P and Oakeley, O and Patterson, J and Sachtschale, R and Swift, G},
Title = {Unique features of the OK-4/Duke storage ring XUV FEL and
monochromatic γ-ray source},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {883-885},
Year = {1998},
Month = {December},
Abstract = {The OK-4 is the first storage ring FEL operating in the
United States. It was commissioned in November, 1996 and
demonstrated lasing in the near UV and visible ranges
(345-413 nm) with extracted power of 0.15 W. In addition to
lasing, the OK-4/Duke FEL generated a nearly monochromatic
(1% FWHM) γ-ray beam. In this paper we describe the initial
performance of the OK-4/Duke storage ring FEL and γ-ray
source.},
Key = {fds249276}
}
@article{fds249277,
Author = {Lumpkin, AH and Yang, BX and Litvinenko, V and Park, S and Wang, P and Wu,
Y},
Title = {Initial application of a dual-sweep streak camera to the
Duke storage ring OK-4 source},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {874-876},
Year = {1998},
Month = {December},
Abstract = {The visible and UV spontaneous emission radiation (SER) from
the Duke OK-4 wiggler has been used with a Hamamatsu C5680
dual-sweep streak camera to characterize the stored electron
beams. Particle beam energies of 270 and 500 MeV in the Duke
storage ring were used in this initial application with the
OK-4 adjusted to generate wavelengths from 500 nm to near
200 nm. The OK-4 magnetic system with its 68 periods
provided a much stronger radiation source than a nearby
bending magnet source point. Sensitivity to single-bunch,
single-turn SER was shown down to 4 μA beam current at λ =
450 nm. The capability of seeing second passes in the FEL
resonator at a wavelength near 200 nm was used to assess the
cavity length versus orbit length. These tests (besides
supporting preparation for UV-visible SR FEL startups) are
also relevant to possible diagnostics techniques for
single-pass FEL prototype facilities.},
Key = {fds249277}
}
@article{fds191715,
Author = {V. N. Litvinenko and Y. Wu},
Title = {On Possibility of Suppression of Microwave Instability and
Production of Femtosecond Pulses of Radiation in Storage
Rings},
Pages = {831-833},
Booktitle = {Proceedings of 1998 Asia Particle Accelerator
Conference},
Year = {1998},
Month = {June},
Abstract = {The microwave instability appears to be main limiting factor
in both longitudinal brightness of electron beam and
achievement of very short bunches. It causes anomalous bunch
lengthening and energy spread growth. The 6D brightness of
electron beam is the main figure of merit for their
applications for generation of coherent X-rays. In this
paper a possibility to suppress or to eliminate the
microwave instability using advanced RF system based on
inverse sub-mm FEL is discussed [1]. We present the
theoretical developments of strong focusing in longitudinal
direction and discuss results of computer simulations. A
possibility of storage ring operating with femtosecond high
peak current electron bunches and natural energy spread is
discussed. This beams can be used to generate both coherent
and spontaneous X-ray beams with femtosecond duration. We
discuss a possibility of the storage ring based FEL X-ray
light source with average spectral brightness of 1027 -1028
ph/sec/mm2/mrad2/0.01%BW. This value exceeds existing 3rd
generation light sources by 6-9 orders of magnitude, making
it a 5th generation light source.},
Key = {fds191715}
}
@article{fds249356,
Author = {Park, SH and Litvinenko, VN and Burnham, B and Wu, Y and Madey, JMJ and Canon, RS and Howell, CR and Roberson, NR and Schreiber, EC and Spraker,
M and Tornow, W and Weller, HR and Pinayev, IV},
Title = {OK-4/Duke monochromatic gamma-ray source: performance and
prediction},
Journal = {Nuclear Instruments \& Methods In Physics Research Section
A-accelerators Spectrometers Detectors And Associated
Equipment},
Volume = {407},
Number = {1-3},
Pages = {224-228},
Publisher = {Elsevier BV},
Year = {1998},
Month = {April},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(97)01400-9},
Abstract = {A beam of nearly monochromatic γ-rays was produced via
intracavity Compton backscattering in the OK-4/Duke storage
ring FEL. The OK-4 FEL operated in the near-UV range
(345-413 nm) with electron energies of 260-550 MeV. The
energy of the produced γ-rays varied from 3 to 16 MeV. In
the near future we plan to increase the energy of the
γ-rays to 50 MeV by increasing the electron energy and
reducing FEL wavelength. Results from direct measurements of
the γ-ray flux and energy resolution (using a 3 mm diameter
lead collimator) (Litvinenko et al., Phys. Rev. Lett. 78
(1997) 4569) are very close to our theoretical predictions.
The energy resolution of the γ-rays was ∼ 1%. In this
paper we present a comparison of our measurements with
theoretical predictions and our plans for future
improvements. We discuss upgrades of our system to attain an
energy resolution down to 0.1% and to increase the flux. A
brief description of the experimental program utilizing the
OK-4/Duke monochromatic γ-ray source is presented. © 1998
Elsevier Science B.V. All rights reserved.},
Doi = {10.1016/S0168-9002(97)01400-9},
Key = {fds249356}
}
@article{fds191716,
Author = {V. N. Litvinenko and S. H. Park and Y. Wu},
Title = {The Duke XUV FEL Storage Ring Facility},
Pages = {834-836},
Booktitle = {Proceedings of 1998 Asia Particle Accelerator
Conference},
Year = {1998},
Abstract = {In this paper we present status and developments of the Duke
storage ring facility. The Duke storage ring facility
provides the unique combination of phase-locked light
sources ranging from high power OK-4 XUV FEL to
quasimonochromatic g -ray beam and IR/X-ray spontaneous
radiation. The XUV OK-4 FEL, which is collaborative project
with BINP, Novosibirsk, is in operation since November,
1996. The OK-4 UV FEL is also used for production of nearly
monochromatic g -ray s with tunable energy. We present the
results of UV lasing with the OK- 4 FEL and selected results
of its applications. We will discuss our future plans for
extension of this source and status of the construction of
dedicated used facility adjacent to the FEL
building.},
Key = {fds191716}
}
@article{fds249355,
Author = {Lumpkin, AH and Yang, BX and Litvinenko, V and Burnham, B and Park, S and Wang, P and Wu, Y},
Title = {Initial Dual-Sweep Streak Camera Measurements on the Duke
Storage Ring OK-4 UV/Visible FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {407},
Number = {1-3},
Pages = {338-342},
Publisher = {Elsevier BV},
Year = {1998},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(98)00046-1},
Abstract = {Initial measurements at the Duke storage ring free electron
laser (FEL) of both spontaneous emission radiation (SER)
from the OK-4 and FEL radiation outcoupled from the
oscillator cavity have been done with a dual-sweep streak
camera. In the SER case, ANLÕs Hamamatsu C5680 streak
camera was used to characterize stored electron-beam bunch
lengths versus rf gap voltage and single-bunch current.
Electron-beam bunch lengths were observed in a range from 50
to 300 ps (FWHM). Particle beam energies of 270 and 500 MeV
in the storage ring (SR) were used with the OK-4 to generate
SER from 500 nm to less than 200 nm. Sensitivity to
single-bunch, single-turn SER was shown down to&4 lA beam
current at j"450 nm. By operating in the synchroscan mode
and at bunch currents less than 1 mA, beam orbit length vs.
the resonator round-trip time was investigated by detecting
the relative arrival time of the second pass outcoupled from
the resonator at j+200 nm. These measurements were used in
support of Þrst lasing in the UV-visible regime in November
1996. The dual-sweep streak mode was then used to monitor
lasing intensity variations on the 1 and 50 ms time scales,
to measure a lasing pulse length as short as&3 ps (p) at
j"388 nm at low beam current, and to track the orbit length
detuning curve.},
Doi = {10.1016/S0168-9002(98)00046-1},
Key = {fds249355}
}
@article{fds249357,
Author = {Litvinenko, VN and Burnham, B and Park, SH and Wu, Y and Cataldo, R and Emamian, M and Faircloth, J and Goetz, S and Hower, N and Madey, JMJ and Meyer, J and Morcombe, P and Oakeley, O and Patterson, J and Swift, G and Wang, P and Pinayev, IV and Fedotov, MG and Gavrilov, NG and Popik, VM and Repkov, VN and Isaeva, LG and Kulipanov, GN and Kurkin, GY and Mikhailov, SF and Skrinsky, AN and Vinokurov, NA and Vobly, PD and Lumpkin, A and Yang, B},
Title = {First UV/Visible Lasing with the OK-4/Duke Storage Ring
FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {407},
Number = {1-3},
Pages = {8-15},
Publisher = {Elsevier BV},
Year = {1998},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(97)01357-0},
Abstract = {In this paper, we report Þrst lasing results in the near-UV
and visible spectral ranges with the OK-4/Duke storage ring
Ð the Þrst storage ring FEL operating in the United
States. The OK-4/Duke FEL was commissioned in November 1996
and demonstrated lasing in the 345Ð413nm range with
extracted power of 0.15 W. In addition to lasing, the
OK-4/Duke FEL generated a nearly monochromatic (1% FWHM)
c-ray beams. In this paper, we describe initial performance
of the OK-4/Duke storage ring FEL and gamma-ray source in
this demonstration experiment. We brießy discuss the
present status of the project and its future user
program.},
Doi = {10.1016/S0168-9002(97)01357-0},
Key = {fds249357}
}
@article{fds249358,
Author = {Wu, Y and Litvinenko, VN and Pinayev, IV and Park, SH and Burnham,
B},
Title = {Duke FEL Storage Ring Light Sources and Applications},
Journal = {Nuclear Instruments and Methods in Physics Research Section
B},
Volume = {144},
Number = {1-4},
Pages = {90-98},
Publisher = {Elsevier BV},
Year = {1998},
url = {http://dx.doi.org/10.1016/S0168-583X(98)00299-7},
Abstract = {In this paper we present the status of the Duke UV FEL (Free
Electron Laser) storage ring, ring based light sources, and
a related multi-disciplinary application program. Using the
OK-4 optical klystron system, we have demonstrated tunable
spontaneous radiation from the near Infrared (IR) to UV,
coherent laser radiation from 345 to 413 nm, and Compton
back-scattered linearly polarized c-ray radiation from 3 to
16 MeV. We report the progress made in developing new light
source capabilities. We also report user interface
development for a pilot application program organized to
utilize various ring driven sources. We discuss future
upgrades and additions to the ring based
sources.},
Doi = {10.1016/S0168-583X(98)00299-7},
Key = {fds249358}
}
@article{fds249359,
Author = {Ade, H and Yang, W and English, SL and Hartman, J and Davis, RF and Nemanich, RJ and Litvinenko, VN and Pinayev, IV and Wu, Y and Madey,
JMJ},
Title = {A Free Electron Laser Photoemission Electron Microscope
System (FEL-PEEM)},
Journal = {Surface Review and Letters},
Volume = {5},
Number = {6},
Pages = {1257-1268},
Publisher = {World Scientific Pub Co Pte Lt},
Year = {1998},
url = {http://dx.doi.org/10.1142/S0218625X98001596},
Abstract = {We report rst results from our e ort to couple a high
resolution photoemission electron microscope (PEEM) to the
OK-4 ultraviolet free electron laser at Duke University
(OK-4 /Duke UV FEL). The OK-4 /Duke UV FEL is a high
intensity source of tunable monochromatic photons in the
3{10 eV energy range. This tunability is unique and allows
us to operate near the photoemission threshold of any
samples and thus maximize sample contrast while keeping
chromatic aberrations in the PEEM minimal. We have recorded
rst images from a variety of samples using spontaneous
radiation from the OK-4 /Duke UV FEL in the photon energy
range of 4.0{6.5 eV. Due to di erent photothreshold emission
from di erent sample areas, emission from these areas could
be turned on (or o ) selectively. We have also observed
relative intensity reversal with changes in photon energy
which are interpreted as density-of-state contrast. Usable
image quality has been achieved, even though the output
power of the FEL in spontaneous emission mode was several
orders of magnitude lower than the anticipated full laser
power. The PEEM has achieved a spatial resolution of 12
nm.},
Doi = {10.1142/S0218625X98001596},
Key = {fds249359}
}
@article{fds292656,
Author = {Pinayev, IV and Emamian, M and Litvinenko, VN and Park, SH and Wu,
Y},
Title = {System for the control and stabilizing of OK-4/Duke FEL
optical cavity},
Journal = {AIP Conference Proceedings},
Volume = {451},
Pages = {545-551},
Booktitle = {AIP Conf. Proceedings 451},
Publisher = {AIP},
Year = {1998},
ISBN = {1-56396-794-4},
ISSN = {0094-243X},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000078034100062&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {The control system of an optical cavity is described. Usage
of the piezoelectric actuators and position sensitive
photodetectors in this system allows us to reach a
resolution at a submicroradian level and to suppress mirror
vibrations below 50 Hz.},
Doi = {10.1063/1.57040},
Key = {fds292656}
}
@article{fds249275,
Author = {Litvinenko, VN and Wu, Y and Burnham, B and Park, SH and Emamian, M and Faircloth, J and Goetz, S and Hower, N and Madey, JMJ and Meyer, J and Morcombe, P and Oakeley, O and Patterson, J and Sachtschale, R and Swift, G and Wang, P and Pinayev, IV and Fedotov, MG and Gavrilov, NG and Popik, VM and Repkov, VN and Isaeva, LG and Kulipanov, GN and Kurkin,
GY and Mikhailov, SF and Skrinsky, AN and Vinokurov, NA and Vobly, PD and Zinin, EI and Lumpkin, AH and Yang, BX},
Title = {First UV/visible lasing with the OK-4/Duke storage ring FEL:
Design and initial performance},
Journal = {Proceedings of SPIE - The International Society for Optical
Engineering},
Volume = {2988},
Pages = {188-199},
Booktitle = {Free-Electron Laser Challenges},
Publisher = {SPIE},
Year = {1997},
Month = {December},
ISSN = {0277-786X},
url = {http://dx.doi.org/10.1117/12.274393},
Abstract = {The OK-4/Duke storage ring FEL was commissioned in November
1996 and demonstrated lasing in the near UV and visible
ranges (345 - 413 nm). The OK-4 is the first storage ring
FEL with the shortest wavelength and highest power for UV
FELs operating in the United States. During one month of
operation we have performed preliminary measurements of the
main parameters of the OK-4 FEL: its gain, lasing power and
temporal structure. In addition to lasing, the OK-4/Duke FEL
generated a nearly monochromatic (1% FWHM) 12.2 MeV
gamma-ray beam. In this paper we describe the design and
initial performance of the OK-4/Duke storage ring FEL. We
compare our predictions with lasing results. Our attempt to
lase in the deep UV range (around 193 nm) is discussed. The
OK-4 diagnostic systems and performance of its optical
cavity are briefly described. ©2005 Copyright SPIE - The
International Society for Optical Engineering.},
Doi = {10.1117/12.274393},
Key = {fds249275}
}
@article{fds249354,
Author = {Litvinenko, VN and Burnham, B and Emamian, M and Hower, N and Madey,
JMJ and Morcombe, P and Oshea, PG and Park, SH and Sachtschale, R and Straub, KD and Swift, G and Wang, P and Wu, Y and Canon, RS and Howell, CR and Roberson, NR and E},
Title = {Gamma-ray production in a storage ring free-electron
laser},
Journal = {Physical Review Letters},
Volume = {78},
Number = {24},
Pages = {4569-4572},
Publisher = {American Physical Society (APS)},
Year = {1997},
Month = {June},
url = {http://dx.doi.org/10.1103/PhysRevLett.78.4569},
Abstract = {A nearly monochromatic beam of 100% linearly polarized γ
rays has been produced via Compton backscattering inside a
free electron laser optical cavity. The beam of 12.2 MeV γ
rays was obtained by backscattering 379.4 nm free-electron
laser photons from 500 MeV electrons circulating in a
storage ring. A detailed description of the γ-ray beam and
the outlook for future improvements are presented. © 1997
The American Physical Society.},
Doi = {10.1103/PhysRevLett.78.4569},
Key = {fds249354}
}
@article{fds249343,
Author = {Burnham, B and Litvinenko, VN and Wu, Y and Park, SH and Cataldo, R and Emamian, M and Hower, N and Madey, JMJ and Morcombe, P and Oakeley, O and Swift, G and Wang, P and Pinayev, IV and Popik, VM and Kulipanov, GN and Mikhailov, SF and Skrinsky, AN and Vinokurov, NA and Lumpkin, A and Yang, B},
Title = {Status of the OK-4/Duke University Storage Ring XUV
FEL},
Journal = {Proceedings of SPIE, Coherent Electron-Beam X-Ray Sources:
Techniques and Applications},
Volume = {3154},
Pages = {64-71},
Publisher = {SPIE},
Year = {1997},
url = {http://dx.doi.org/10.1117/12.293371},
Abstract = {The OK-4/Duke storage ring free electron laser (FEL) was
commissioned in November, 1996 and demonstrated lasing in
the near UV and visible ranges. During one month of
operation we performed preliminary measurements of the main
parameters of the OK-4 FEL: its gain, lasing power and
temporal structure. In addition to lasing, the OK-4/Duke FEL
generated a nearly monochromatic 12.2 MeV (gamma) -ray beam.
In this paper we describe the status of the main subsystems
including the injector system and the ring itself, and
discus future and in-progress upgrades to these systems. We
also describe the parameters measured to date of the
injector, the storage ring, the generated optical laser
beams, and the backscattered (gamma) -ray
beam.},
Doi = {10.1117/12.293371},
Key = {fds249343}
}
@article{fds249353,
Author = {Wu, Y and Litvinenko, VN and Burnham, B and Park, SH and Madey,
JMJ},
Title = {Performance and Operation Modes of the Duke FEL Storage
Ring},
Journal = {IEEE Transactions on Nuclear Science},
Volume = {44},
Number = {5},
Pages = {1753-1759},
Publisher = {Institute of Electrical and Electronics Engineers
(IEEE)},
Year = {1997},
ISSN = {0018-9499},
url = {http://dx.doi.org/10.1109/23.633429},
Abstract = {We present the recent status and performance of the Duke
Free Electron Laser (FEL) storage ring. We report a large
transverse and energy aperture observed in the storage ring.
We describe the consequences of this large aperture on the
operation of the storage ring. Several unusual phenomena are
reported in this paper, including large amplitude transverse
multibunch coherent oscillations (Saturn rings) and beam
capture from outside the RF separatrix. We also present the
established operation modes for the storage ring, including
energy ramping, working point tuning, and different
bunch-mode operations to optimize the ring as a synchrotron
light source, an FEL, and a gamma-ray source. Finally, we
summarize the achieved storage ring parameters since its
first operation in November 1994.},
Doi = {10.1109/23.633429},
Key = {fds249353}
}
@article{fds249350,
Author = {Oshea, PG and Litvinenko, VN and Madey, JMJ and Roberson, NR and Schreiber, EC and Straub, KD and Weeks, KJ and Weller, HR and Wu,
Y},
Title = {Inverse Compton gamma-ray source for nuclear physics and
related applications},
Journal = {Nuclear Instruments \& Methods In Physics Research Section
A-accelerators Spectrometers Detectors And Associated
Equipment},
Volume = {375},
Number = {1-3},
Pages = {530-534},
Publisher = {Elsevier BV},
Year = {1996},
Month = {June},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(96)00052-6},
Abstract = {The development of intense, short-wavelength FEL light
sources has opened opportunities for new applications of
high-energy Compton-backscattered photons. These
applications range from medical imaging with X-rays to high
energy physics with photon colliders. In this paper we
discuss the practical aspects applications using polarized
Compton backscattered γ-rays in the 5-150 MeV range from
the Duke storage-ring-driven FEL. Such applications include:
nuclear physics, cancer therapy, radiographic imaging,
radiation effects testing, and positron production for
material science studies.},
Doi = {10.1016/0168-9002(96)00052-6},
Key = {fds249350}
}
@article{fds292657,
Author = {Burnham, B and Litvinenko, VN and Madey, JMJ and Wu,
Y},
Title = {Microbunching in storage ring},
Journal = {MICRO BUNCHES WORKSHOP},
Number = {367},
Pages = {215-224},
Publisher = {AIP PRESS},
Editor = {Blum, EB and Dienes, M and Murphy, JB},
Year = {1996},
Month = {January},
ISBN = {1-56396-555-0},
ISSN = {0094-243X},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1996BF35Z00020&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Key = {fds292657}
}
@article{fds191723,
Author = {B. Burnham and V. N. Litvinenko and J. M. J. Madey and Y.
Wu},
Title = {Microbunching in Storage Ring FELs},
Journal = {Proceedings of Micro Bunches Workshop, Editors: E. B. Blum,
M. Dienes, J. B. Murphy},
Volume = {367},
Pages = {215--224},
Booktitle = {AIP Conf. Proceedings},
Year = {1996},
Abstract = {We propose two schemes to create short electron bunches
within a storage ring free electron laser (FEL). The first
scheme proposed will operate a nearly isochronous ramwave
FEL at the Duke storage ring facility. Resonant FEL
conditions for the nun-wave will be provided by the off-axis
interaction with an electromagnetic wave. Simulation results
for the proposed mm-wave FEL operation on the Duke storage
ring will be discussed. The second proposal is to maintain
electron structure on an optical wave scale by operating the
storage ring on a high order resonance in order to produce
FEL power above the random phase approximation. The high
order resonance will be used to compensate for the natural
dispersion and loss of phase information. An N-th order
resonance will restore phase information after N turns of
the electron bunch in the storage ring. In this mode, which
does not require isochronicity of the ring, the stochastic
conditions used to derive the random phase approximation are
no longer applicable.},
Key = {fds191723}
}
@article{fds249351,
Author = {Litvinenko, VN and Burnham, B and Madey, JMJ and Park, SH and Wu,
Y},
Title = {Duke Storage Ring UV/VUV FEL: Status and
Prospects},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {375},
Number = {1-3},
Pages = {46-52},
Publisher = {Elsevier BV},
Year = {1996},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(95)01471-3},
Abstract = {A 1 .I GeV electron storage ring dedicated for UV-VUV FEL
operation was commissioned last year at the Duke University
Free Electron Laser Laboratory [V.N. Litvinenko et al..
Commissioning of the Duke storage ring, Proc. 1995 Particle
Accelerator Conf., Dallas, TX, May 1-5, 19951. The XUV FEL
project, based on the collaboration of the Duke FEL
Laboratory and Budker Institute for Nuclear Physics
(Novosibirsk, Russia) is described. The OK-4 UV FEL has
arrived from Novosibirsk at the Duke FEL laboratory and is
in the process of installation. The main parameters of the
Duke Free Electron Laser Laboratory (DFELL) storage ring,
the OK-4 optical klystron. and the experimental set-up are
presented. The parameters of the UV-VUV FEL are given and
possible future upgrades to this system are discussed. We
have developed a new macro-particle code for storage ring
simulation including all known mechanisms of storage ring
FEL interaction. We confirm our expectations on the average
and peak power for the OK-4. In addition we have studied a
giant pulse mode of operation. A new mechanism of
“super-pulse” generation was discovered during these
studies. It allows the generation of peak power up to 10 GW
using “phase-space” refreshment of the electron beam
caused by synchrotron motion [V.N. Litvinenko, B. Burnham,
J.M.J. Madey and Y. Wu, Nucl. Instr. and Meth. A 358 (1995)
3341.]},
Doi = {10.1016/0168-9002(95)01471-3},
Key = {fds249351}
}
@article{fds249352,
Author = {Wu, Y and Litvinenko, VN and Burnham, B and Madey, JMJ and Park,
SH},
Title = {The Performance of the Duke FEL Storage Ring},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {375},
Number = {1-3},
Pages = {74-77},
Publisher = {Elsevier BV},
Year = {1996},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(95)01473-X},
Abstract = {Commissioning of the Duke FEL storage ring has been
completed successfully. During commissioning and initial
operation, a series of performance measurements were
performed on the storage ring. In this paper we discuss the
techniques used in the measurements. present the
measurements results. and compare the measured parameters
with the design specifications.},
Doi = {10.1016/0168-9002(95)01473-X},
Key = {fds249352}
}
@article{fds249268,
Author = {Wang, P and Morcombe, P and Wu, Y},
Title = {RF system for the Duke 1 GeV storage ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {3},
Pages = {1841-1842},
Year = {1995},
Month = {December},
Abstract = {The RF frequency is 178.5 MHz. An amplifier built by the QEI
corporation provides 50 KW power. All the power feeds to a
single-cell RF cavity, built by BINP at Novosibirsk, Russia,
giving a gap voltage of 720 KV. An ANT circulator is used in
the feed line. There are four basic feed-back loops to
stabilize the system operation : 1) Cavity frequency tuning
loop. 2) Cavity voltage control loop. 3) RF phase
stabilization loop. 4) Synchrotron oscillation damping loop.
The whole system has been tested and operated since December
1993. It has provided secure and stable operation for the
storage ring.},
Key = {fds249268}
}
@article{fds249269,
Author = {Burnham, B and Litvinenko, VN and Wu, Y},
Title = {Application of precision magnetic measurements for control
of the Duke storage ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {524-526},
Year = {1995},
Month = {December},
Abstract = {The 1 GeV Duke storage ring is designed to drive UV and VUV
free electron laser devices. Specifics of this ring include
the use of combined function magnets: quadrupole-sextupole
and dipole-sextupole. The close spacing of magnetic elements
required the use of these combined function magnets. A
discussion on the measurement of these magnets is included,
as well as the data analysis used to create a viable control
system for the combined function magnets.},
Key = {fds249269}
}
@article{fds249270,
Author = {Litvinenko, VN and Burnham, B and Hower, N and Morcombe, P and Wu,
Y},
Title = {Duke storage ring tune measurements system using razor blade
and photomultiplier},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2461-2463},
Year = {1995},
Month = {December},
Abstract = {We present in this paper the description of the Duke storage
ring tune measurements system. An unusual feature of this
system is the use of synchrotron radiation to sense
oscillation of the electron beam. This system includes a
lens, a razor blade placed at the focus and a
photomultiplier. Our experience shows that this system can
operate on -70 dBm level and detect electron beam
oscillations as small as one micron.},
Key = {fds249270}
}
@article{fds249271,
Author = {Wu, Y and Litvinenko, VN and Burnham, B and Madey,
JMJ},
Title = {Experimental study of the Duke storage ring dynamic
aperture},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {5},
Pages = {2877-2879},
Year = {1995},
Month = {December},
Abstract = {The Duke storage ring was designed with a large dynamic
aperture for UV-VUV Free Electron Laser (FEL) operations.
During commissioning of the Duke storage ring, experiments
were performed to measure the horizontal, vertical, and
energy apertures. The experimental methods used for the
aperture measurements are presented in this paper. The
measured results are discussed and compared with the
computer simulations.},
Key = {fds249271}
}
@article{fds249272,
Author = {Dickey, C and Burnham, B and Carter, F and Fricks, R and Litvinenko, V and Nagchaudhuri, A and Morcombe, P and Pantazis, R and O'Shea, P and Sachtschale, R and Wu, Y},
Title = {EPICS at Duke University},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2217-2219},
Year = {1995},
Month = {December},
Abstract = {Since the last Particle Accelerator Conference, the
Experimental Physics and Industrial Control System (EPICS)
has been utilized for control system development and
implementation on several accelerators that have recently
been commissioned at the Free Electron Laser Laboratory
which is operated under the auspices of the Physics
Department at Duke University. The historic Mark III
infrared free electron laser formerly located at Stanford
University, a recently designed and constructed 280 MeV
electron linear accelerator and a 1 GeV storage ring
synchrotron are now operating under EPICS control.
Commissioning of the new injection linac and the storage
ring has gone extremely well. The authors feel that through
the employment of a standard controls development
environment such as EPICS, considerable amounts of
resources, both financial and human, have been saved. The
authors note generally positive experiences with EPICS. The
highlights of these experiences, as well as some suggestions
for future improvements will be presented in the body of
this report.},
Key = {fds249272}
}
@article{fds249273,
Author = {Litvinenko, VN and Wu, Y and Burnham, B and Madey, JMJ and Carter, F and Dickey, C and Emamian, M and Gustavsson, J and Hower, N and Morcombe, P and Park, SH and O'Shea, P and Sachtshale, R and Straub, D and Swift,
G},
Title = {Commissioning of the Duke Storage Ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {213-215},
Year = {1995},
Month = {December},
Abstract = {The commissioning of the 1 GeV Duke Storage Ring began in
November, 1994 with the demonstration of injection, storage
and ramping to 1 GeV at the first attempt. The ring is now
operational. The Duke project is unique in that the storage
ring and linac were designed, constructed and commissioned
by a small new University laboratory, operating on a low
budget. The team is comprised of six accelerator physicists
and graduate students, eight engineers, and fifteen
technicians.},
Key = {fds249273}
}
@article{fds249274,
Author = {Wu, Y and Burnham, B and Litvinenko, VN},
Title = {Duke storage ring control system},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2214-2216},
Year = {1995},
Month = {December},
Abstract = {The Duke storage ring is a dedicated facility for the UV-VUV
FEL operation. The low level computer control system for the
Duke storage ring is developed using EPICS. The control
hardware employs several different architectures including
CAMAC, GPIB, Allen Bradley, and VME. The high level control
is implemented in Tcl-Tk scripts running on SPARCstations.
Tcl-Tk provides the global control capabilities such as the
energy ramping, the orbit compensation, and the tune and
chromaticity control. The Duke storage ring control system
was tested and operational for storage ring commissioning in
Nov. 1994. During commissioning, additional control tools
were developed to facilitate the operation.},
Key = {fds249274}
}
@article{fds249334,
Author = {Litvinenko, VN and Wu, Y and Burnham, B and Madey, JMJ and Park,
SH},
Title = {Performance of achromatic lattice with combined function
sextupoles at Duke storage ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2},
Pages = {796-798},
Year = {1995},
Month = {December},
Abstract = {The 1 GeV Duke Storage Ring was very successfully
commissioned with performance exceeding initial
specifications. In this paper we present design and
performance data of its unique achromatic lattice with
combined function magnets in the ring arcs.},
Key = {fds249334}
}
@article{fds249335,
Author = {O'Shea, PG and Carter, F and Dickey, C and Hower, N and Litvinenko, VN and Sachtschale, R and Swift, G and Wang, P and Wu, Y and Madey,
JMJ},
Title = {Accelerator archeology - the resurrection of the Stanford
MarkIII electron linac at Duke},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {2},
Pages = {1090-1092},
Year = {1995},
Month = {December},
Abstract = {In the early 1960s, the Mark III accelerator at the Stanford
High Energy Physics Laboratory was used as the prototype
test-bed for the SLAC Two-Mile accelerator. In the mid 1980s
the accelerator was dismantled and a large part of it was
transported to the Duke University Free-Electron Laser
Laboratory to form the basis of the injector for the 1-GeV
Duke Storage Ring. The plan was to use the original
accelerator sections and some rf equipment with new magnetic
optics, vacuum system, gun and a modern control system. The
first 295-MeV portion of the linac is now operational at
Duke. The linac currently consists of eleven sections from
the old linac with a single-cell rf gun. Our guiding
principal has been one of economy and simplicity. We have
not attempted to restore the accelerator to its original
form, but have added modern components where necessary. We
discuss some of the more interesting features of the linac,
and how we have given new life to this venerable machine
here at Duke.},
Key = {fds249335}
}
@article{fds191722,
Author = {Y. Wu and B. Burnham and V. N. Litvinenko},
Title = {The Duke Storage Ring Control System},
Journal = {Proceedings of 1995 Particle Accelerator
Conference},
Pages = {2214-2216},
Year = {1995},
Abstract = {The Duke storage ring is a dedicated facility for the UV-VUV
FEL operation. The low level computer control system for the
Duke storage ring is developed using EPICS. The control
hardware employs several different architectures including
CAMAC, GPIB, Allen Bradley, and VME. The high level control
is implemented in Tcl-Tk scripts running on SPARCstations.
Tcl- Tk provides the global control capabilities such as the
energy ramping, the orbit compensation, and the tune and
chromaticity control. The Duke storage ring control system
was tested and operational for storage ring commissioning in
Nov. 1994. During commissioning, additional control tools
were developed to facilitate the operation.},
Key = {fds191722}
}
@article{fds249340,
Author = {Litvinenko, VN and Wu, Y and Burnham, B and Barnett, G and Madey,
JMJ},
Title = {Picosecond, Tunable, High Peak Brightness Hard X-Ray Inverse
Compton Source at Duke Storage Ring},
Journal = {Proceedings of SPIE},
Volume = {2521},
Pages = {2-12},
Publisher = {SPIE},
Year = {1995},
ISSN = {0277-786X},
url = {http://dx.doi.org/10.1117/12.218350},
Abstract = {We suggest a state-of-the-art X-ray source using a compact
electron storage ring with modest energy (less then 1 GeV)
and a high power mm-wave as an undulator. A source of this
type has X-ray energies and brightness comparable with third
generation synchrotron light sources while it can be very
compact and fit in a small university or industrial
laboratory or hospital. We propose to operate an isochronous
mm-wave FEL and a hard X-ray Inverse Compton source at the
Duke storage ring to test this concept. Resonant FEL
conditions for the mm-wave will be provided by the off-axis
interaction with an electromagnetic wave. A special optical
resonator with holes for the c-beam is proposed for pumping
a hard X-ray Inverse Compton source with very high
brightness. Simulation results of mm-wave FEL operation on
the Duke storage ring are discussed. Expected performance of
mm-wave FEL and bard X-ray Inverse Compton source are
presented.},
Doi = {10.1117/12.218350},
Key = {fds249340}
}
@article{fds249341,
Author = {Litvinenko, VN and Barnett, GA and Burnham, B and Hower, N and Johnson,
J and Madey, JMJ and Wu, Y},
Title = {Short Wavelength Light Sources at Duke Storage
Ring},
Journal = {Proceedings of SPIE},
Volume = {2522},
Pages = {473-482},
Publisher = {SPIE},
Year = {1995},
ISSN = {0277-786X},
url = {http://dx.doi.org/10.1117/12.221605},
Abstract = {A 1.1 GeV electron storage ring is now fully operational at
the Duke University Free Electron Laser Laboratory. This
ring is dedicated to drive a variety of very high brightness
short- wavelength sources ranging from UV to gamma-rays. In
this paper we present overview of short-wavelength radiation
sources including THE OK-4 (XUV FEL, wiggler radiation and
inverse Compton (gamma) -rays), X-ray bend-magnets
synchrotron radiation, soft X-ray NIST undulator radiation
and hard X-ray inverse Compton source. We also describe
status of the sources and our short-term and long-term
plans.},
Doi = {10.1117/12.221605},
Key = {fds249341}
}
@article{fds249342,
Author = {Litvinenko, VN and Burnham, B and Madey, JMJ and Wu,
Y},
Title = {High Peak Pulse Power Operation of the OK-4/Duke XUV
FEL},
Journal = {Proceedings of SPIE},
Volume = {2521},
Pages = {78-89},
Publisher = {SPIE},
Year = {1995},
ISSN = {0277-786X},
url = {http://dx.doi.org/10.1117/12.218368},
Abstract = {A 1 GeV electron storage ring dedicated for UV-VUV FEL
operation was commissioned last year at the Duke University
Free Electron Laser Laboratory. The XUV FEL project, based
on the collaboration of the Duke FEL Laboratory and Budker
Insititute for Nuclear Physics (Novosibirsk, Russia) is
described. The OK-4 UV FEL has arrived from Novosibirsk at
the Duke FEL laboratory and is in the process of
installation. The main parameters of the DFELL storage ring,
the OK-4 optical klystron, and the experimental set-up are
presented. The parameters of the UV-VUV FEL are given and
the possible future upgrades to this system are discussed.
We have studied the dynamics of giant pulse generation in
the Duke/OK-4 UV FEL. We have developed a new macro-particle
code for giant pulse simulation including all known
mechanisms of storage ring FEL interaction. Results of these
giant pulse simulations are presented in the paper. A new
mechanism of 'super-pulse' generation was discovered during
these studies. It allows the generation of peak power up to
10 gigawatts using 'phase- space' refreshment of the
electron beam caused by synchrotron motion.},
Doi = {10.1117/12.218368},
Key = {fds249342}
}
@article{fds249346,
Author = {Litvinenko, VN and Burnham, B and Madey, JMJ and Wu,
Y},
Title = {Dynamics of the Duke Storage Ring UV FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {358},
Number = {1-3},
Pages = {369-373},
Publisher = {Elsevier BV},
Year = {1995},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(94)01575-9},
Abstract = {The Duke 1 GeV storage ring will be commissioned this year
with a 280 MeV linac-injector. We intend to ramp the energy
to 0.7-1.0 GeV for FEL operation. The OK-4 optical klystron
will be shipped from the Budker Institute of Nuclear Physics
to Duke in early 199.5. The OK-4 will be the first FEL to
operate on the Duke storage ring. This paper is dedicated to
the study of the OK-4 performance in the CW mode of
operation in the UV range, using a 3-D code developed by the
authors.},
Doi = {10.1016/0168-9002(94)01575-9},
Key = {fds249346}
}
@article{fds249347,
Author = {Litvinenko, VN and Burnham, B and Madey, JMJ and Wu,
Y},
Title = {Giant Laser Pulses in the Duke Storage Ring UV
FEL},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {358},
Number = {1-3},
Pages = {334-337},
Publisher = {Elsevier BV},
Year = {1995},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(94)01290-3},
Abstract = {We have studied the dynamics of giant pulse generation in
the Duke UV FEL with peak power of several gigawatts. The
giant pulses will be provided by a FEL gain modulation
technique developed for the OK-4 UV FEL at Novosibirsk,
Russia. A new mechanism for “super-pulse” generation was
discovered during these studies. It allows the generation of
peak power up to 10 GW using the “phase space”
refreshment of the electron beam caused by synchrotron
motion [V. Litvinenko et al., to be published]. We have
developed a new macro-particle code for giant pulse
simulation including all known mechanisms of storage ring
FEL interaction. Results of these giant pulse simulations
are presented in the paper.},
Doi = {10.1016/0168-9002(94)01290-3},
Key = {fds249347}
}
@article{fds249348,
Author = {Litvinenko, VN and Wu, Y and Burnham, B and Madey,
JMJ},
Title = {Expected Performance of the mm-Wave Isochronous FEL at the
Duke Storage Ring},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {358},
Number = {1-3},
Pages = {349-352},
Publisher = {Elsevier BV},
Year = {1995},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(94)01415-9},
Abstract = {We propose to operate an isochronous mm-wave FEL at the Duke
storage ring. Resonant FEL conditions for mm-waves will be
provided by the off-axis interaction with an electromagnetic
wave. The intracavity power of the mm-wave FEL could be used
to pump a hard X-ray inverse Compton source with very high
brightness. This is discussed in a separate contribution to
these proceedings. Simulation results of mm-wave FEL
operation on the Duke storage ring are discussed. The
expected performance of a mm-wave FEL is
presented.},
Doi = {10.1016/0168-9002(94)01415-9},
Key = {fds249348}
}
@article{fds249349,
Author = {Litvinenko, VN and Wu, Y and Burnham, B and Barnett, G and Madey,
JMJ},
Title = {mm-Wave Isochronous FEL and Hard X-Ray Inverse Compton
Source at the Duke Storage Ring},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {358},
Number = {1-3},
Pages = {345-348},
Publisher = {Elsevier BV},
Year = {1995},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(94)01414-0},
Abstract = {We propose to operate an isochronous mm-wave FEL at the Duke
storage ring. Resonant FEL conditions for mm-waves will be
provided by the off-axis interaction with an electromagnetic
wave. A special optical resonator with holes for the e-beam
is proposed for pumping a hard X-ray inverse Compton source
with very high brightness. Simulation results for proposed
mm-wave FEL operation on the Duke storage ring are discussed
in a separate article in these proceedings. The expected
performance of the hard X-ray inverse Compton source is
presented.},
Doi = {10.1016/0168-9002(94)01414-0},
Key = {fds249349}
}
@article{fds191733,
Author = {S. Kramer and Y. Wu and V. N. Litvinenko and C. B. Mckee and B.
Burnham},
Title = {Bunch Current Density Measurements in the VUV Light
Source},
Journal = {Proceedings of 4th European Particle Accelerator Conference
(EPAC1994)},
Pages = {1696-1698},
Year = {1994},
Abstract = {Recentm easurementosf the bunch current density in the VUV
storage ring at the National Synchrotron Light Source have
been made from a stripline using a new technology of a
realtime oscilloscope with bandwidth up to 5 GHz. A
deconvolution technique has been developed to reconstruct
the bunch current distribution in the longitudinal
direction. The non-Gaussian lengthened bunch profiles at
high currents and with a 4th harmonic RF systema rc
reconstructed.},
Key = {fds191733}
}
@article{fds249345,
Author = {Wu, Y and Litvinenko, VN and Madey, JMJ},
Title = {Study of Undulator Influence on the Dynamic Aperture for the
Duke FEL Storage Ring},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {341},
Number = {1-3},
Pages = {363-366},
Publisher = {Elsevier BV},
Year = {1994},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(94)90383-2},
Abstract = {The Duke FEL storage ring is designed to accommodate FEL
undulators with a maximum length of 26 m. We present the
study of undulator influence on the dynamic aperture for the
OK-4 FEL and the future 26 m FEL.},
Doi = {10.1016/0168-9002(94)90383-2},
Key = {fds249345}
}
@article{fds249265,
Author = {Burnham, B and Hower, N and Litvinenko, VN and Madey, JMJ and Wu,
Y},
Title = {Specific features of magnet design for the Duke FEL storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {4},
Pages = {2889-2891},
Publisher = {IEEE},
Year = {1993},
Month = {December},
url = {http://dx.doi.org/10.1109/pac.1993.309495},
Abstract = {The 1 GeV Duke free electron laser (FEL) storage ring is
dedicated to drive UV and VUV free electron laser devices.
The high brightness and low emittance electron beams needed
for these devices demand high performance and tolerances on
the storage ring magnet lattice. This paper discusses how
the combined function magnets are used to eliminate discrete
elements and odd shaped end pieces which can cause magnetic
coupling saturation and severe undesirable field
nonlinearities. Also included is a discussion of a
nonstandard septum magnet with stray field compensation
which will be employed by this storage ring.},
Doi = {10.1109/pac.1993.309495},
Key = {fds249265}
}
@article{fds249267,
Author = {Wu, Y and Litvinenko, VN and Madey, JMJ},
Title = {Lattice and dynamic aperture of the Duke FEL storage
ring},
Journal = {Proceedings of the IEEE Particle Accelerator
Conference},
Volume = {1},
Pages = {218-220},
Publisher = {IEEE},
Year = {1993},
Month = {December},
url = {http://dx.doi.org/10.1109/pac.1993.308961},
Abstract = {A low emittance lattice of the Duke FEL (Free Electron
Laser) storage ring dedicated to drive UV-VUV FELs is
presented. The second order geometrical aberration is
compensated to increase the dynamic aperture. The 6-D
dynamic aperture study has been performed on this lattice
using symplectic tracking codes, which demonstrates a large
energy aperture. The influences of higher-order multipoles
(HMs), RMS errors and 6.8-m OK-4 undulator on dynamic
aperture are studied. The transverse dynamic aperture is
mainly limited by HMs in the straight section quadrupoles.
For future FEL operations, we have designed a new straight
section lattice for a 26-m long FEL undulator. The dynamic
aperture for this lattice is discussed.},
Doi = {10.1109/pac.1993.308961},
Key = {fds249267}
}
@article{fds249344,
Author = {Wu, Y and Litvinenko, VN and Forest, E and Madey,
JMJ},
Title = {Dynamic Aperture Study for the Duke FEL Storage
Ring},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A},
Volume = {331},
Number = {1-3},
Pages = {287-292},
Publisher = {Elsevier BV},
Year = {1993},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/0168-9002(93)90060-U},
Abstract = {The new lattice design of the Duke free electron laser (FEL)
storage ring is described. The results of the 6-dimensional
dynamic aperture study using single particle tracking codes
are presented. The influence of 8-m FEL undulator on the
dynamic aperture is studied.},
Doi = {10.1016/0168-9002(93)90060-U},
Key = {fds249344}
}
%% Papers Accepted
@article{fds374995,
Author = {Peifan Liu and Jun Yan and Andrei A. Fanasev and Stephen V. Benson and Hao Hao and Stepha F. Mikhailov and Victor G. Popov and Ying K.
Wu},
Title = {Generation of superposed orbital angular momentum beams
using a free-electron laser oscillator},
Journal = {Optics Express},
Year = {2023},
Month = {December},
ISSN = {1094-4087},
Key = {fds374995}
}
%% Papers Submitted
@article{fds347941,
Author = {X. Li and M.W. Ahmed and A. Banu and C. Bartram and B. Crowe and E.J.
Downie, M. Emamian and G. Feldman and H. Gao and D. Godagama and H.W.
Grießhammer, C.R. Howell and H.J. Karwowski and D.P. Kendellen and M.A. Kovash and K. Leung and D. Markoff and S. Mikhailov and R.E.
Pywell, M.H. Sikora and J.A. Silano and R.S. Sosa and M.C. Spraker and G. Swift and P. Wallace and H.R. Weller and C.S. Whisnant and Y.K. Wu and Z.W. Zhao},
Title = {Compton scattering from 4He at HIGS},
Journal = {Phys. Rev. C (submitted in 2019)},
Year = {2019},
Key = {fds347941}
}
%% Other
@misc{fds360687,
Author = {S. Mikhailov. M. Ahmed and V. Popov and M. Sikora and G. Swift and P.
Wallace, Y.K. Wu and J. Yan and H. Ehlers and L. Jensen and L.
Kochanneck},
Title = {Production of 120 MeV Gamma-ray Beams at Duke FEL and HIGS
Facility},
Year = {2021},
Key = {fds360687}
}
@misc{fds360684,
Author = {Y. K. Wu},
Title = {Accelerator and Light Source Research Program at Duke
University},
Journal = {Proceedings of the 12th International Particle Accelerator
Conference (IPAC21)},
Pages = {1636–1639},
Year = {2021},
Key = {fds360684}
}
@misc{fds360685,
Author = {P. Liu and J. Yan and W. Li and Y.K. Wu},
Title = {Eigenmode Decomposition for Free-Electron Lasers Using
Bayesian Analysis},
Journal = {Proceedings of the 12th International Particle Accelerator
Conference (IPAC21)},
Pages = {1666–1669},
Year = {2021},
Key = {fds360685}
}
@misc{fds360686,
Author = {W. Li and J. Yan and P. Liu and Y. K. Wu},
Title = {Design Study on Beam Size Measurement System Using SR
Interferometry for Low Beam Current},
Journal = {Proceedings of the 12th International Particle Accelerator
Conference (IPAC21)},
Pages = {3949–3952},
Year = {2021},
Key = {fds360686}
}
@misc{fds17607,
Author = {Y. Wu and S. Mikhailov and C. Howell and M. Busch and the HIGS
development team},
Title = {The Upgrade of the High Intensity Gamma-ray Source
(Technical Design Report, 1st version)},
Year = {2003},
Month = {August},
Key = {fds17607}
}