%% Books
@book{fds184712,
Author = {C.D. Bowman and E. G. Bilpuch and D.C. Bowman and A.S. Crowell and C.R.
Howell, K. McCabe and G. A. Smith and A.P. Tonchev and W. Tornow and V.
Violet, R.B. Vogelaar and R.L. Walter and J. Yingling.},
Title = {The Alternative Reactor Technology Comprising Graphite,
Molten Salt, and Accelerators.},
Booktitle = {Handbook of Nuclear Engineering},
Publisher = {Springer Science+Business Media LLC 2010},
Editor = {Dan Gabriel Cacuci},
Year = {2010},
ISBN = {DOI 10.1007/978-0-387-98149-9_24},
Key = {fds184712}
}
%% Papers Published
@article{fds313704,
Author = {Tonchev, AP and Kondev, PG and Hristov, HG and Gangrsky, YP and Balabanov, NP and Tcholakov, VD},
Title = {Isomeric yield ratio of134I in photofission
of232Th and238U},
Journal = {Journal of Radioanalytical and Nuclear Chemistry},
Volume = {155},
Number = {5},
Pages = {299-309},
Year = {1991},
Month = {November},
ISSN = {0236-5731},
url = {http://dx.doi.org/10.1007/BF02163877},
Abstract = {The isomeric yield ratios for134I, for the photofission
of232Th and238U with 25-MeV bremsstrahlung have been
determined using radiochemical techniques and
γ-spectrometry. Angular moment a of the corresponding
fission fragments, Jrms, were calculated by the statistical
procedure of Huizenga and Vandenbosch. We have discovered a
significant proton odd-even effect on Jrms values, and
demonstrated its dependence on the nuclear structure of
fragments. © 1991 Akadémiai Kiadó.},
Doi = {10.1007/BF02163877},
Key = {fds313704}
}
@article{fds313684,
Author = {Kondev, PG and Tonchev, AP and Khristov, KG and Zhuchko,
VE},
Title = {Calculation of bremsstrahlung spectra from a thick tungsten
radiator as a function of photon energy and
angle},
Journal = {Nuclear Instruments and Methods in Physics Research Section
B: Beam Interactions With Materials and Atoms},
Volume = {71},
Number = {2},
Pages = {126-131},
Year = {1992},
Month = {August},
ISSN = {0168-583X},
url = {http://dx.doi.org/10.1016/0168-583X(92)95313-G},
Abstract = {A method for the calculation of bremsstrahlung spectra
produced by 5-30 MeV electrons is described for the case of
a thick tungsten radiator at observation angles from 0° to
20°. The computation is based on Shiff integrated-over-angle
bremsstrahlung cross-section and includes energy losses,
absorption and multiple scattering of the electrons in the
radiator, the variation of the bremsstrahlung cross-section
angular distribution with photon energy, and the absorption
of radiation in the target material. The results obtained by
the offered method were compared with known experimental
data and Monte Carlo calculations of thick target
bremsstrahlung spectra. A basic advantage of this method is
that it needs only a small memory and short computing time.
© 1992.},
Doi = {10.1016/0168-583X(92)95313-G},
Key = {fds313684}
}
@article{fds313687,
Author = {Belov, AG and Gangrsky, YP and Tonchev, AP and Balabanov, NP and Hristov, HG},
Title = {Measurement of isomeric ratios in the reactions (γ, n) on
barium isotopes in the giant-dipole-resonance
region},
Journal = {Physics of Atomic Nuclei},
Volume = {59},
Number = {3},
Pages = {367-371},
Year = {1996},
Month = {March},
ISSN = {1063-7788},
Abstract = {The cross sections for the reactions (γ, n) in which odd Ba
isotopes with A = 129-137 are produced in the ground and
isomeric h11/2 states are measured in the
giant-dipole-resonance region by an activation method. The
isomeric ratio is obtained as a function of photon energy
and isotope mass number. Various factors that affect the
isomeric ratio are discussed.},
Key = {fds313687}
}
@article{fds313682,
Author = {Belov, AG and Gangrsky, YP and Tonchev, AP and Balabanov,
NP},
Title = {Excitation of isomeric 1h11/2 states in the
reactions (γ, n)},
Journal = {Physics of Atomic Nuclei},
Volume = {59},
Number = {4},
Pages = {553-559},
Year = {1996},
Month = {April},
ISSN = {1063-7788},
Abstract = {The cross sections for the reactions (γ, n) leading to the
ground and isomeric 1h11/2 states in 16 isotopes of Pd, Cd,
Sn, Te, Ba, Ce, Nd, and Sm are measured. The energy of γ
rays corresponds to the region of the giant dipole
resonance. The method of induced activity is used in the
measurements. It is found that isomeric ratios depend on the
number of intranuclear neutrons and protons and on the
excitation energy of a residual nucleus. Various factors
that affect the isomeric ratio are discussed.},
Key = {fds313682}
}
@article{fds313663,
Author = {Gangrskiǐ, YP and Tonchev, AP and Balabanov, NP},
Title = {Excitation of isomeric states in photonuclear
reactions},
Journal = {Physics of Particles and Nuclei},
Volume = {27},
Number = {4},
Pages = {428-452},
Year = {1996},
Month = {July},
ISSN = {1063-7796},
Abstract = {The experimental data on the probabilities of exciting
isomeric states in (γ,γ′) and (γ,n) photonuclear
reactions at energies from threshold to the giant dipole
resonance are reviewed. The isomeric ratios for g9/2, h11/2,
and i13/2 single-particle neutron states are given, together
with those for two-quasiparticle states and shape isomers.
The experimental values of the isomeric ratios are compared
with the values calculated using the statistical model. The
properties of nuclear levels in the energy range 1-6 MeV,
via which isomeric states are populated, are discussed. ©
1996 American Institute of Physics.},
Key = {fds313663}
}
@article{fds313688,
Author = {Belov, AG and Gangrsky, YP and Tonchev, AP and Zuzaan,
P},
Title = {Excitation of the high-spin 180Hf isomer and
de-excitation of the 180Ta isomer in (γ, γ′)
reactions},
Journal = {Hyperfine Interactions},
Volume = {107},
Number = {1-4},
Pages = {167-173},
Year = {1997},
Month = {January},
ISSN = {0304-3843},
url = {http://dx.doi.org/10.1023/a:1012011923772},
Abstract = {The reaction mechanism of excitation and de-excitation of
the high-spin isomers 180Hf (J = 8-) and 180Ta (J = 9-) in
inelastic gamma-quanta scattering was investigated. An
anomalously large integral cross section and isomeric ratio
for 180Ta in comparison to 180Hf were obtained. Level
properties influencing these relations are
discussed.},
Doi = {10.1023/a:1012011923772},
Key = {fds313688}
}
@article{fds313681,
Author = {Belov, AG and Gangrsky, YP and Zhuchko, VE and Tonchev,
AP},
Title = {Excitation of isomeric states in (γ, n) and (n, γ)
reactions on Eu isotopes},
Journal = {Physics of Atomic Nuclei},
Volume = {60},
Number = {11},
Pages = {1773-1779},
Year = {1997},
Month = {November},
ISSN = {1063-7788},
Abstract = {Isomeric ratios were measured for (γ, n) and (n, γ)
reactions on Eu isotopes, which lie at the boundary between
spherical and deformed nuclei. Targets from 151Eu and 153Eu
were irradiated by thermal neutrons and by bremsstrahlung
photons from a microtron with endpoint energies between 13
and 22 MeV. The reactions under investigation resulted in
the excitation of 0- and 8- isomeric states in 150Eu, 152Eu,
and 154Eu isotopes. The γ spectra of product nuclides were
measured to determine the reaction yields. The effect of
quadrupole deformation on the isomeric ratios is
discussed.},
Key = {fds313681}
}
@article{fds313673,
Author = {Belov, AG and Gangrsky, YP and Zuzaan, P and Tonchev,
AP},
Title = {Excitation of high-spin isomer180Hf and
deexcitation of high-spin isomer ls"Ta at inelastic
scattering of y-quanta},
Journal = {Izvestiya Akademii Nauk. Ser. Fizicheskaya},
Volume = {61},
Number = {2},
Pages = {401-406},
Year = {1997},
Month = {December},
ISSN = {0367-6765},
Key = {fds313673}
}
@article{fds313683,
Author = {Tonchev, AP and Gangrsky, YP and Belov, AG and Zhuchko,
VE},
Title = {Deformation on isomeric excitation of Eu isotopes in
[Formula Presented] and [Formula Presented]
reactions},
Journal = {Physical Review C},
Volume = {58},
Number = {5},
Pages = {2851-2857},
Year = {1998},
Month = {January},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.58.2851},
Abstract = {Isomeric ratios in [Formula Presented] and [Formula
Presented] reactions in Eu isotopes were measured. Thermal
neutrons and bremsstrahlung photons in the giant dipole
resonance energy range of 13–22 MeV were used to excite
the isomeric states. The isomeric levels [Formula Presented]
and [Formula Presented] were excited in the isotopes
[Formula Presented] and [Formula Presented] The cross
section for the reaction [Formula Presented] leading to the
high-spin isomeric state [Formula Presented] on [Formula
Presented] isotope was measured in the giant-dipole-resonance
region by the activation method. Experimental values of the
isomeric cross section ratios were compared with the
theoretical values. The influence of the nuclei quadropole
deformation on the isomeric ratio was described. © 1998 The
American Physical Society.},
Doi = {10.1103/PhysRevC.58.2851},
Key = {fds313683}
}
@article{fds313662,
Author = {Gangrsky, YP and Zuzaan, P and Kolesnikov, NN and Lukashek, VG and Tonchev, AP},
Title = {Isomeric ratios in (γ, p) reactions at giant-dipole-resonance
energies},
Journal = {Physics of Atomic Nuclei},
Volume = {62},
Number = {10},
Pages = {1615-1620},
Year = {1999},
Month = {October},
ISSN = {1063-7788},
Abstract = {Isomeric ratios in (γ, p) photonuclear reactions have been
measured at energies in the giant-dipole-resonance region.
In these measurements, 98Mo, 100Ru, 118Sn, 120Sn, and 122Sn
isotopes have been exposed to bremsstrahlung from a
microtron. The activation method has been used to measure
the reaction yields. Data obtained in this way have been
compared with the results of calculations based on the
statistical model.},
Key = {fds313662}
}
@article{fds313695,
Author = {Tonchev, AP and Harmon, JF and Brey, R},
Title = {Analysis of ore samples employing photon activation of the
metastable states of gold and silver},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {422},
Number = {1-3},
Pages = {926-928},
Year = {1999},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(98)01047-X},
Abstract = {The analytical method described here uses inelastic gamma
scattering to produce 197mAu(T1/2 = 7.8s), 107mAg(T1/2 =
44.2s) and 109mAg(T1/2 = 39.8s) with the subsequent
measurement of residual activity. Bremsstrahlung radiation
from linear electron accelerator with maximum γ quanta of 6
to 9 MeV is optimum for this purpose. Induced activity from
gold and silver was measured with a HPGe. To obtain maximum
sensitivity for detection, it is advantageous to measure
both gamma and X-ray activity. Possible interferences were
studied in detail, using the pure element spectra and also
literature data. The most evident advantage of the method is
its rapidity and relatively low cost of analysis. © 1999
Elsevier Science B.V. All rights reserved.},
Doi = {10.1016/S0168-9002(98)01047-X},
Key = {fds313695}
}
@article{fds313697,
Author = {Tonchev, AP and Harmon, JF and King, BD},
Title = {Application of low energy photon spectroscopy in isomer
production of Hf, W, Ir, Pt, Au and Hg using (γ, γ′)
reactions},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {422},
Number = {1-3},
Pages = {510-512},
Year = {1999},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(98)01076-6},
Abstract = {In the present work we present results of activation
analysis of various heavy metals using bremsstrahlung gammas
to create short lived nuclear isomers. The method uses
inelastic gamma scattering on natural samples of Hf, W, Ir,
Pt, Au, and Hg to produce the isomers 179mHf, 183mW, 191mIr,
195mPt, 197mAu, and 199mHg. For isomer detection, a
comparison is made between the minimum detection limit
achievable using either isomeric gammas or the
characteristic X-rays which follow internal conversion. This
latter mechanism has the bulk of the decay probability for
most of the nuclei studied. An election linac was used to
produce the bremsstrahlung, with electron energies between 6
and 8 MeV being optimal. Interferences were investigated and
optimal irradiation and counting times were determined using
predominantly low energy photon spectroscopy. A linear
electron accelerator producing bremsstrahlung radiation with
a maximum quanta of 6-8 MeV has proven to be optimal for the
isomeric excitation. © 1999 Elsevier Science B.V. All
rights reserved.},
Doi = {10.1016/S0168-9002(98)01076-6},
Key = {fds313697}
}
@article{fds313705,
Author = {Tonchev, AP and Gangrsky, YP and Belov, AG},
Title = {New candidates for high spin isomeric targets},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {422},
Number = {1-3},
Pages = {532-535},
Year = {1999},
Month = {December},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(98)01080-8},
Abstract = {Experimental results of the accumulation and study of
reaction mechanism of the de-excitation of high spin
isomeric targets 108mAg (Jπ = 6+), 166mHo (Jπ = 7-) and
180mTa (Jπ = 9-) are discussed. Together with other
isomers, such as 178m2Hf (Jπ = 16+), 186mRe (Jπ = 8+),
242m Am (Jπ = 5-), which can be produced by neutron-capture
reactions or in reactions involving heavy ions, they can
possibly be used for new experiments in nuclear physics. The
large integral cross section for neutron capture (usually
some barns) and enough cooling time allows the ground state
of these isomers to completely decay due to their short
half-life. The large integral de-excitation cross section
(more 10 mb MeV) in inelastic γ-quanta scattering allows
for a successful measurement on a small number of atoms ( <
1015) and makes them candidates for γ-laser on the nuclear
levels. © 1999 Elsevier Science B.V. All rights
reserved.},
Doi = {10.1016/S0168-9002(98)01080-8},
Key = {fds313705}
}
@article{fds313694,
Author = {Tsoneva, N and Stoyanov, C and Gangrsky, YP and Ponomarev, VY and Balabanov, NP and Tonchev, AP},
Title = {Population of isomers in the decay of the giant dipole
resonance},
Journal = {Physical Review C},
Volume = {61},
Number = {4},
Pages = {443031-443039},
Year = {2000},
Month = {January},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.61.044303},
Abstract = {The value of an isomeric ratio (IR) in N = 81 isotones
(137Ba, 139Ce, 141Nd, and 143Sm) is studied by means of the
(γ,n) reaction. This quantity measures a probability to
populate the isomeric state in respect to the ground state
population. In (γ,n) reactions, the giant dipole resonance
(GDR) is excited and after its decay by a neutron emission,
the nucleus has an excitation energy of a few MeV. The
forthcoming γ decay by direct or cascade transitions
deexcites the nucleus into an isomeric or ground state. It
has been observed experimentally that the IR for 137Ba and
139Ce equals about 0.13 while in two heavier isotones it is
even less than half the size. To explain this effect, the
structure of the excited states in the energy region up to
6.5 MeV has been calculated within the quasiparticle phonon
model. Many states are found connected to the ground and
isomeric states by E1, E2, and M1 transitions. The
single-particle component of the wave function is
responsible for the large values of the transitions. The
calculated value of the isomeric ratio is in very good
agreement with the experimental data for all isotones. A
slightly different value of maximum energy with which the
nuclei rest after neutron decay of the GDR is responsible
for the reported effect of the A dependence of the
IR.},
Doi = {10.1103/PhysRevC.61.044303},
Key = {fds313694}
}
@article{fds313685,
Author = {Tonchev, AP and Harmon, JF},
Title = {Excitation of the 180mTa isomer in (gamma,n) reactions and
its astrophysical relevance},
Journal = {Applied Radiation and Isotopes : Including Data,
Instrumentation and Methods for Use in Agriculture, Industry
and Medicine},
Volume = {52},
Number = {4},
Pages = {873-882},
Year = {2000},
Month = {April},
ISSN = {0969-8043},
url = {http://dx.doi.org/10.1016/s0969-8043(99)00132-3},
Abstract = {The yield has been determined for the excitation of 180gTa
(Jpi = 1+) from the 181Ta(gamma,n) reaction by measurements
of gamma rays emitted following the electron capture and
beta-decays of the 8.15 h ground state. The probability
sigmam/(sigmam + sigmag) for the production of the 180mTa
isomer (Jpi = 9-) after gamma absorption in the energy
region from 8 to 13 MeV was deduced. The role of the initial
and final spins on the reaction yield, along with the
relevance for nucleosynthesis of 180mTa, is
discussed.},
Doi = {10.1016/s0969-8043(99)00132-3},
Key = {fds313685}
}
@article{fds313644,
Author = {Nesaraja, CD and Brune, CR and Crowley, BT and Kelley, JH and Nelson,
SO and Prior, RM and Sabourov, K and Tilley, DR and Tonchev, A and Weller,
HR},
Title = {Ratio of S Factors for (p,ƒ×) Reactions on 12C and 13C at
Astrophysically Relevant Energies},
Journal = {Phys. Rev.},
Volume = {C64},
Number = {6},
Pages = {065804},
Year = {2001},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.64.0658XX},
Abstract = {We present measurements of the 12 C(p, γ 0 ) 13 N/ 13 C(p,
γ 0 ) 14 N S factor ratio at E p =160 keV. The overall
result of 0.33±0.03 is in good agreement with the value of
this ratio obtained from previous experimental values of the
S factors for the 12 C(p, γ 0 ) 13 N and the 13 C(p, γ 0 )
14 N reactions. A value for the total S factor ratio of S[
12 C(p, γ total )]/S[ 13 C(p, γ total )] = 0.24±0.03 is
computed by correcting the 13 C(p, γ 0 ) S factor for
transitions to the other intermediate states. The direct +
resonance model calculation of this ratio and the impact on
the CNO cycle are also explored.},
Doi = {10.1103/PhysRevC.64.0658XX},
Key = {fds313644}
}
@article{fds331120,
Author = {Nesaraja, CD and Brune, CR and Crowley, BT and Kelley, JH and Nelson,
SO and Prior, RM and Sabourov, K and Tilley, DR and Tonchev, A and Weller,
HR},
Title = {Ratio of S factors for [Formula Presented] reactions on
[Formula Presented] and [Formula Presented] at
astrophysically relevant energies},
Journal = {Physical Review C},
Volume = {64},
Number = {6},
Pages = {7},
Year = {2001},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevC.64.065804},
Abstract = {We present measurements of the [Formula Presented] S factor
ratio at [Formula Presented] The overall result of [Formula
Presented] is in good agreement with the value of this ratio
obtained from previous experimental values of the S factors
for the [Formula Presented] and the [Formula Presented]
reactions. A value for the total S factor ratio of [Formula
Presented] is computed by correcting the [Formula Presented]
S factor for transitions to the other intermediate states.
The direct + resonance model calculation of this ratio and
the impact on the CNO cycle are also explored. © 2001 The
American Physical Society.},
Doi = {10.1103/PhysRevC.64.065804},
Key = {fds331120}
}
@article{fds313636,
Author = {Belov, AG and Gangrsky, YP and Melnikova, LM and Ponomarev, VY and Tsoneva, N and Stoyanov, C and Tonchev, A and Balabanov,
N},
Title = {Excitation of isomeric 1h11/2 states in nuclear
reactions induced by γ rays and neutrons and in beta
decay},
Journal = {Physics of Atomic Nuclei},
Volume = {64},
Number = {11},
Pages = {1901-1908},
Year = {2001},
Month = {November},
ISSN = {1063-7788},
url = {http://dx.doi.org/10.1134/1.1423740},
Abstract = {Isomeric ratios were measured for N = 81 isotones (135Xe,
137Ba, 139Ce, 141Nd, 143Sm). In the experiment reported
here, Jπ = 11/2- isomers were excited in (n, γ) and (γ,
n) reactions and in the β+ decay of 139Pr and 141Pm. In
order to determine the reaction yields, use was made of the
activation method involving measurement of the gamma-ray
spectra of reaction products. It is found that, in the same
reactions, isomeric ratios are different for isotones
characterized by different atomic numbers Z. Isomeric ratios
were calculated with the spectra of low-lying levels and
radiative-transition probabilities established on the basis
of the quasiparticle-phonon model. Good agreement between
the experimental and calculated values of isomeric ratios is
obtained for all isotopes invesigated here. The dependence
of isomeric ratios on the atomic number Z of a nucleus is
explained by the difference of reaction energies, which
leads to different probabilities of excitation of activation
levels through which the isomers being considered are
populated. © 2001 MAIK "Nauka/Interperiodica".},
Doi = {10.1134/1.1423740},
Key = {fds313636}
}
@article{fds313674,
Author = {Gangrsky, YP and Zuzaan, P and Lukashik, NN and Tonchev,
AP},
Title = {Izomeric ratios in cross reactions (ny) and
(γn)},
Journal = {Izvestiya Akademii Nauk. Ser. Fizicheskaya},
Volume = {65},
Number = {1},
Pages = {111-116},
Year = {2001},
Month = {December},
ISSN = {0367-6765},
Key = {fds313674}
}
@article{fds331119,
Author = {Pietralla, N and Litvinenko, VN and Hartman, S and Mikhailov, FF and Pinayev, IV and Swift, G and Ahmed, MW and Kelley, JH and Nelson, SO and Prior, R and Sabourov, K and Tonchev, AP and Weller,
HR},
Title = {Identification of the [Formula Presented] two-phonon state
of [Formula Presented]},
Journal = {Physical Review C},
Volume = {65},
Number = {4},
Pages = {3},
Year = {2002},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevC.65.047305},
Abstract = {The linearly polarized γ-ray beam produced by the [Formula
Presented] facility has been used to determine the parity of
two previously known dipole excitations in [Formula
Presented] The azimuthal asymmetry of γ rays produced in
the process of nuclear resonance fluorescence indicated that
the dipole state at 4.742 MeV, recently discussed as a new
form of [Formula Presented] excitation, is in fact a
[Formula Presented] state. The [Formula Presented] state at
4.742 MeV must, therefore, be reconsidered as the [Formula
Presented] member of the quadrupole-octupole coupled
two-phonon multiplet. A second state at 7.535 MeV was also
assigned [Formula Presented]. © 2002 The American Physical
Society.},
Doi = {10.1103/PhysRevC.65.047305},
Key = {fds331119}
}
@article{fds313693,
Author = {Pietralla, N and Litvinenko, VN and Hartman, S and Mikhailov, FF and Pinayev, IV and Swift, G and Ahmed, MW and Kelley, JH and Nelson, SO and Prior, R and Sabourov, K and Tonchev, AP and Weller,
HR},
Title = {Identification of the Jπ=1-
two-phonon state of 88Sr},
Journal = {Physical Review C},
Volume = {65},
Number = {4},
Pages = {473051-473053},
Year = {2002},
Month = {January},
ISSN = {0556-2813},
Abstract = {The linearly polarized γ-ray beam produced by the HIγS
facility has been used to determine the parity of two
previously known dipole excitations in 88Sr. The azimuthal
asymmetry of γ rays produced in the process of nuclear
resonance fluorescence indicated that the dipole state at
4.742 MeV, recently discussed as a new form of M 1
excitation, is in fact a 1- (E1) state. The 1- state at
4.742 MeV must, therefore, be reconsidered as the Jπ = 1-1
member of the quadrupole-octupole coupled two-phonon
multiplet. A second state at 7.53.5 MeV was also assigned
Jπ = 1-.},
Key = {fds313693}
}
@article{fds313698,
Author = {Pietralla, N and Litvinenko, VN and Hartman, S and Mikhailov, FF and Pinayev, IV and Swift, G and Ahmed, MW and Kelley, JH and Nelson, SO and Prior, R and Sabourov, K and Tonchev, AP and Weller,
HR},
Title = {Erratum: Identification of the Jπ=1-
two-phonon state of 88Sr (Physical Review C
(2002) 65 (047305))},
Journal = {Physical Review C},
Volume = {65},
Number = {6},
Pages = {699011},
Year = {2002},
Month = {January},
ISSN = {0556-2813},
Key = {fds313698}
}
@article{fds313701,
Author = {Pietralla, N and Berant, Z and Litvinenko, VN and Hartmann, S and Mikhailov, FF and Pinayev, IV and Swift, G and Ahmed, MW and Kelley, JH and Nelson, SO and Prior, RM and Sabourov, K and Tonchev, AP and Weller,
HR},
Title = {Parity Measurements of Nuclear Levels using a
Free-Electron-Laser Generated Gamma-Ray Beam},
Journal = {Physical Review Letters},
Volume = {88},
Number = {1},
Pages = {012502},
Publisher = {American Physical Society},
Year = {2002},
Month = {January},
ISSN = {0031-9007},
url = {http://dx.doi.org/10.1103/PhysRevLett.88.012502},
Abstract = {aps.org},
Doi = {10.1103/PhysRevLett.88.012502},
Key = {fds313701}
}
@article{fds313689,
Author = {Pietralla, N and Weller, HR and Litvinenko, VN and Ahmed, MW and Tonchev, AP},
Title = {Parity measurements of nuclear dipole excitations using
FEL-generated γ-rays at HIγS},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {483},
Number = {1-2},
Pages = {556-559},
Year = {2002},
Month = {May},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/S0168-9002(02)00381-9},
Abstract = {First Nuclear Resonance Fluorescence (NRF) experiments were
performed at the storage ring FEL-driven High Intensity
Gamma Source (HIγS) at the DFELL. Azimuthal NRF intensity
ratios were measured around the polarized HIγS beam.
Electric character was deduced for 18 dipole excitations in
138Ba [1]. The measurements demonstrate the superior
performance of the HIγS facility in making such
measurements. We report here on the performance of this
set-up. © 2002 Elsevier Science B.V. All rights
reserved.},
Doi = {10.1016/S0168-9002(02)00381-9},
Key = {fds313689}
}
@article{fds313690,
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 = {fds313690}
}
@article{fds331117,
Author = {Nelson, SO and Ahmed, MW and Perdue, BA and Sabourov, K and Sabourov,
AL and Tonchev, AP and Prior, RM and Spraker, M and Weller,
HR},
Title = {Analyzing power measurement for the [Formula Presented]
reaction at astrophysically relevant energies},
Journal = {Physical Review C},
Volume = {68},
Number = {6},
Pages = {6},
Year = {2003},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevC.68.065804},
Abstract = {The [Formula Presented] reaction has been investigated by
measuring the angular distributions of its cross section and
analyzing power using a [Formula Presented] polarized proton
beam. Calculations using a direct-capture-plus-resonance
model were compared with the data. The results indicate the
presence of [Formula Presented] transition amplitudes which
were not considered in previous extrapolations of the
astrophysical [Formula Presented] factor to low energies.
The impact on the zero-energy [Formula Presented] factor of
the [Formula Presented] reaction is discussed. © 2003 The
American Physical Society.},
Doi = {10.1103/PhysRevC.68.065804},
Key = {fds331117}
}
@article{fds331118,
Author = {Tonchev, AP and Nelson, SO and Sabourov, K and Crowley, BT and Joshi, K and Weller, HR and Kelley, JH and Prior, RM and Spraker, M and Kalantar-Nayestanaki, N},
Title = {The [Formula Presented] reaction at astrophysically relevant
energies},
Journal = {Physical Review C},
Volume = {68},
Number = {4},
Pages = {12},
Year = {2003},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevC.68.045803},
Abstract = {The [Formula Presented] reaction was studied by detecting
the [Formula Presented]-rays produced when 100-, 130-, and
[Formula Presented] polarized protons were stopped in a
thick [Formula Presented] target. Polarized and unpolarized
incident beams were used to measure the cross section and
vector analyzing power as a function of angle and energy for
capture to the ground [Formula Presented], the second
[Formula Presented], and the fifth [Formula Presented]
excited states of [Formula Presented]. The data were
analyzed to obtain the amplitudes and phases of the
contributing transition-matrix elements at each measured
energy for all three transitions. Values of the
astrophysical [Formula Presented] factors were obtained from
the cross section data and are compared to previous results.
A direct capture plus resonance model calculation was
performed in an attempt to account for all measured
quantities. It was found that the large [Formula Presented]
value of [Formula Presented] observed in the case of capture
to the ground state could be accounted for by including the
sub-threshold resonance at [Formula Presented]. © 2003 The
American Physical Society.},
Doi = {10.1103/PhysRevC.68.045803},
Key = {fds331118}
}
@article{fds313649,
Author = {Nelson, SO and Ahmed, MW and Perdue, BA and Sabourov, K and Sabourov,
AL and Tonchev, AP and Prior, RM and Spraker, M and Weller,
HR},
Title = {Analyzing power measurement for the 14N(→p, γ)
15O reaction at astrophysically relevant
energies},
Journal = {Physical Review C},
Volume = {68},
Number = {6},
Pages = {658041-658046},
Year = {2003},
Month = {January},
ISSN = {0556-2813},
Abstract = {The 14N(→p, γ)15O reaction has been investigated by
measuring the angular distributions of its cross section and
analyzing power using a 270-keV polarized proton beam.
Calculations using a direct-capture-plus-resonance model
were compared with the data. The results indicate the
presence of γ transition amplitudes which were not
considered in previous extrapolations of the astrophysical S
factor to low energies. The impact on the zero-energy S
factor of the 14N(→p, γ)15O reaction is
discussed.},
Key = {fds313649}
}
@article{fds313680,
Author = {Tonchev, AP and Nelson, SO and Sabourov, K and Crowley, BT and Joshi, K and Weller, HR and Kelley, JH and Prior, RM and Spraker, M and Kalantar-Nayestanaki, N},
Title = {The 10B(p→, γ)11C reaction at
astrophysically relevant energies},
Journal = {Physical Review C},
Volume = {68},
Number = {4},
Pages = {458031-4580312},
Year = {2003},
Month = {January},
ISSN = {0556-2813},
Abstract = {The 10B(p→, γ)11C reaction was studied by detecting the
γ-rays produced when 100-, 130-, and 160-keV polarized
protons were stopped in a thick 10B target. Polarized and
unpolarized incident beams were used to measure the cross
section and vector analyzing power as a function of angle
and energy for capture to the ground (Jπ=3/2-), the second
(E=4319 keV, J π=5/2-), and the fifth (E=6478 keV, J
π=7/2-) excited states of 11C. The data were analyzed to
obtain the amplitudes and phases of the contributing
transition-matrix elements at each measured energy for all
three transitions. Values of the astrophysical S factors
were obtained from the cross section data and are compared
to previous results. A direct capture plus resonance model
calculation was performed in an attempt to account for all
measured quantities. It was found that the large (∼32%)
value of Ay(90°) observed in the case of capture to the
ground state could be accounted for by including the
subthreshold resonance at 8420 keV.},
Key = {fds313680}
}
@article{fds313641,
Author = {Perdue, BA and Ahmed, MW and Tonchev, AP and Weller, HR and Feldman, G and Litvinenko, VN and Pinayev, IV and Norum, BE and Prior, RM and Spraker,
MC and Sawatzky, BD},
Title = {Compton scattering of polarized γ rays by16O for
E γ=25-40 MeV},
Journal = {Physical Review C},
Volume = {70},
Number = {6},
Year = {2004},
Month = {January},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.70.064305},
Abstract = {Measurements of the polarization asymmetries σ(θ c.m.) and
σ(Eγ) of Compton scattering by 16O have been performed in
the energy range of 25-40 MeV over a range of scattering
angles between 90 and 150°. An analysis of the present data
combined with previous results indicates that significant,
narrow concentrations of E2 strength are not present below
an excitation energy of 40 MeV. The existence, however, of a
broad isovector giant quadrupole resonance exhausting a
large percentage of the isovector energy weighted sum rule
is not ruled out by the combined data. Additionally, the
present data are insensitive to modifications to the free
values of the nucleon polarizabilities, but cannot rule them
out.},
Doi = {10.1103/PhysRevC.70.064305},
Key = {fds313641}
}
@article{fds313642,
Author = {Prior, RM and Spraker, MC and Amthor, AM and Keeter, KJ and Nelson, SO and Sabourov, A and Sabourov, K and Tonchev, A and Ahmed, M and Kelley, JH and Tilley, DR and Weller, HR and Hofmann, HM},
Title = {Energy Dependence of the Astrophysical S-factor for the
6Li(p,gamma)7Be Reaction},
Journal = {Physical Review},
Volume = {C70},
Number = {5},
Pages = {055801},
Publisher = {THE AMERICAN PHYSICAL SOCIETY},
Year = {2004},
Month = {December},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.70.055801},
Abstract = {Polarized proton beams with energies from 80 to 130 keV have
been used to determine the slope of the astrophysical S
factor for the 6Li(p, γ,0)7Be and 6Li(p,γ1) 7Be reactions.
The slope was determined from the relative yields at five
incident proton energies. The slope of the S factor was
found to be negative. The analyzing power measurements
indicate that the reaction proceeds predominately by s-wave
capture. The negative slope does not appear to be due to
low-binding-energy effects, the effects of nearby
resonances, or electron screening of the nuclei. A
resonating group model calculation demonstrates a new
mechanism for producing a negative slope at astrophysically
relevant energies in radiative capture reactions.},
Doi = {10.1103/PhysRevC.70.055801},
Key = {fds313642}
}
@article{fds313643,
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},
Year = {2004},
Month = {December},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.70.044317},
Doi = {10.1103/PhysRevC.70.044317},
Key = {fds313643}
}
@article{fds313635,
Author = {Sabourov, K and Ahmed, MW and Canon, SR and Crowley, B and Joshi, K and Kelley, JH and Nelson, SO and Perdue, BA and Schreiber, EC and Sabourov,
A and Tonchev, A and Weller, HR and Wulf, EA and Prior, RM and Spraker, MC and Hofmann, HM and Trini, M},
Title = {Experimental and Theoretical Study of the D(d,gamma)4He
Reaction below Ecm = 60 keV},
Journal = {Physical Review},
Volume = {C70},
Number = {6},
Pages = {064601},
Publisher = {THE AMERICAN PHYSICAL SOCIETY},
Year = {2004},
Month = {December},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.70.064601},
Abstract = {New measurements of the analyzing powers A y and T 20 have
been obtained for the 2 H(d, γ) 4 He reaction at a
laboratory beam energy of 115 keV. A transition matrix
element analysis results in a unique solution which
indicates that the reaction proceeds by 55% E2, 29% E1, and
16% M2 radiation. These results are shown to be in good
agreement with the results of a new refined resonating group
model calculation. The impact of these results on the
extrapolated value of the astrophysical 5 factor for this
reaction is discussed.},
Doi = {10.1103/PhysRevC.70.064601},
Key = {fds313635}
}
@article{fds313639,
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://dx.doi.org/10.1016/j.nimb.2005.07.080},
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 = {fds313639}
}
@article{fds167396,
Author = {A.P. Tonchev and M. Boswell and C.R. Howell and H.J. Karwowski and J.H. Kelley and W. Tornow and Y.K. Wu},
Title = {The High Intensity Gamma-Ray Source (HIGS) and Recent
Results.},
Journal = {Nucl. Instr. and Methods in Phys. Res. B 241,
51474},
Year = {2005},
Key = {fds167396}
}
@article{fds313640,
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},
Year = {2005},
Month = {May},
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 = {fds313640}
}
@article{fds313638,
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},
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 = {fds313638}
}
@article{fds167386,
Author = {T.C. Li and N. Pietralla and M. Ahmed and T. Ahn and C. Angell and M.
Blackston, A. Costin and K. Keeter and J. Li and Y. Parpottas and B.
Perdue, I.V. Pinayev and G. Rainovski and A.P. Tonchev and W. Tornow and H.R. Weller and Y.K. Wu},
Title = {Search for magnetic dipole excitation strength in
40Ar},
Journal = {Phys. Rev. C 73, 054306},
Year = {2006},
Key = {fds167386}
}
@article{fds167387,
Author = {A. Sabourov and M.W. Ahmed and M.A. Blackston and A.S. Crowell and C.R.
Howell, B.A. Perdue and K. Sabourov and A. Tonchev and H.R. Weller and R.M. Prior and M.C. Spraker},
Title = {Astrophysical S factor for the 7Li(d,n0)8Be and 7Li(d,n1)8Be
reactions},
Journal = {Phys. Rev. C 73, 015801},
Year = {2006},
Key = {fds167387}
}
@article{fds313675,
Author = {Sabourov, A and Ahmed, MW and Blackston, MA and Crowell, AS and Howell,
CR and Perdue, BA and Sabourov, K and Tonchev, A and Weller, HR and Prior,
RM and Spraker, MC},
Title = {Astrophysical S factor for the Li7(d,n0)Be8 and Li7(d,n1)Be8
reactions},
Journal = {Physical Review C},
Volume = {73},
Number = {1},
Year = {2006},
Month = {January},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.73.015801},
Abstract = {The absolute astrophysical S factor and cross section for
the Li7(d,n0)Be8 and Li7(d,n1)Be8 reactions have been
determined using deuteron beams with energies between 45 and
80 keV. The slope of the S factor is consistent with zero in
the n0 case but is slightly negative in the n1 case. The S
factor for the sum of both neutron groups at c.m. energies
below 70 keV is S(E)=5400(±1500)-37(±21)E keV b, where E
is the c.m. energy in keV. © 2006 The American Physical
Society.},
Doi = {10.1103/PhysRevC.73.015801},
Key = {fds313675}
}
@article{fds313656,
Author = {Sabourov, A and Ahmed, MW and Blackston, MA and Crowell, AS and Howell,
CR and Joshi, K and Nelson, SO and Perdue, BA and Sabourov, K and Tonchev,
A and Weller, HR and Prior, RM and Spraker, MC and Braizinha, B and Kalantar-Nayestanaki, N},
Title = {The Li7(d→,n0)Be8 and Li7(d→,n1)Be8 reactions below 160
keV},
Journal = {Physical Review C},
Volume = {74},
Number = {6},
Year = {2006},
Month = {January},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.74.064611},
Abstract = {The polarization observables have been determined for the
Li7(d→,n0)Be8 and Li7(d→,n1)Be8 reactions at beam
energies between 80 and 160 keV. A Transition Matrix Element
(TME) analysis revealed unique, dominant p-wave solutions
for both neutron channels. The polarization observables were
compared with distorted wave Born approximation (DWBA) and
coupled reaction channels (CRC) calculations. The general
features of the data can be reproduced by the CRC
calculations when a large target spin-orbit interaction is
included. However, serious discrepancies are observed when
the TMEs of the theory and experiment are compared. © 2006
The American Physical Society.},
Doi = {10.1103/PhysRevC.74.064611},
Key = {fds313656}
}
@article{fds313703,
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://dx.doi.org/10.1103/PhysRevC.73.054306},
Abstract = {www.aps.org},
Doi = {10.1103/PhysRevC.73.054306},
Key = {fds313703}
}
@article{fds313668,
Author = {Tonchev, AP and Angell, C and Boswell, M and Howell, CR and Karwowski,
HJ and Kelley, JH and Tornow, W and Tsoneva, N},
Title = {Low-energy dipole modes of excitation below the neutron
separation energy},
Journal = {Aip Conference Proceedings},
Volume = {819},
Pages = {350-354},
Year = {2006},
Month = {March},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.2187883},
Abstract = {The nuclear resonance fluorescence experiments have been
performed at the High Intensity Gamma Source (HIγS) on
138Ba nuclei using four 60% efficient HPGe detectors.
Excitation energies, spin, parities, and decay branching
ratios were measured for the low-energy dipole modes of
excitations. Experimental results on the parity measurement
below the neutron separation energy shows that all dipole
states in this energy region exhibit E1 excitation. These
results are consistent with theoretical prediction of the
collective isoscalar nature of this low-energy mode of
excitation. © 2006 American Institute of
Physics.},
Doi = {10.1063/1.2187883},
Key = {fds313668}
}
@article{fds313671,
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},
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 = {fds313671}
}
@article{fds313657,
Author = {Angell, CT and Karwowski, HJ and Kelley, JH and Tonchev, AP and Tornow,
W},
Title = {Photo-induced population of the h11/2 isomeric
states in (γ, n) reactions},
Journal = {Aip Conference Proceedings},
Volume = {819},
Pages = {363-367},
Year = {2006},
Month = {March},
ISBN = {0735403139},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.2187885},
Abstract = {The mechanism of excitation of isomeric h11/2 states in
nuclei around the closed shell at N=82 have been studied at
the High-Intensity Gamma Source (HIγS). We have taken
advantage of the monoenergetic (ΔE/E=1.5%) and pulsed
γ-ray-beam from HIγS to perform in-beam spectroscopy
measurements with an improved level of precision and
sensitivity. The giant dipole resonances at 15 MeV in the
N=82 target isotones 138Ba, 140Ce, and 142Nd have been
excited, and following neutron emission the γ-ray cascades
leading to the isomeric h11/2 state and the ground state
were observed in the N=81 isotones. For all three nuclei a
very similar de-excitation scheme was found. The only level
observed from which the isomeric state was populated was
found to be Jπ = 7/2-. The ground state is principally
populated from the states with spin and parities Jπ = 1/2+,
5/2+, and 7/2+. The structure of the N=81 isotones and the
role of the gateway states in isomer population will be
discussed. The results of the measurements will be compared
with statistical model calculations. © 2006 American
Institute of Physics.},
Doi = {10.1063/1.2187885},
Key = {fds313657}
}
@article{fds346925,
Author = {Tonchev, AP and Angell, C and Boswell, M and Howell, CR and Karwowski,
HJ and Kelley, JH and Tornow, W and Tsoneva, N},
Title = {Missing dipole excitation strength below the particle
threshold},
Journal = {Proceedings of Science},
Volume = {44},
Year = {2007},
Month = {January},
Abstract = {High sensitivity studies of E1 andM1 excitations fromthe
138Ba(γ,γ') reaction at energies close to the neutron
emission threshold have been performed. The electric dipole
character of the "pygmy" mode was experimentally verified
for excitations from 5.5-8.5 MeV. Missing dipole strength
has been reveal in our photon-scattering
measurements.},
Key = {fds346925}
}
@article{fds313665,
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},
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 = {fds313665}
}
@article{fds313677,
Author = {Hutcheson, A and Angell, CT and Becker, JA and Boswell, M and Crowell,
AS and Dashdorj, D and Fallin, B and Fotiades, N and Howell, CR and Karwowski, HJ and Kelley, JH and Kiser, M and Macri, RA and Nelson, RO and Pedroni, RS and Tonchev, AP and Tornow, W and Vieira, DJ and Weisel, GJ and Wilhelmy, JB},
Title = {Pulsed and monoenergetic beams for neutron cross-section
measurements using activation and scattering techniques at
Triangle Universities Nuclear Laboratory},
Journal = {Nuclear Instruments and Methods in Physics Research Section
B: Beam Interactions With Materials and Atoms},
Volume = {261},
Number = {1-2 SPEC. ISS.},
Pages = {369-372},
Year = {2007},
Month = {August},
ISSN = {0168-583X},
url = {http://dx.doi.org/10.1016/j.nimb.2007.04.097},
Abstract = {In support of the Stewardship Science Academic Alliances
initiative, an experimental program has been developed at
Triangle Universities Nuclear Laboratory (TUNL) to measure
(n,xn) cross-sections with both in-beam and activation
techniques with the goal of improving the partial
cross-section database for the NNSA Stockpile Stewardship
Program. First experimental efforts include excitation
function measurements on 235,238U and 241Am using pulsed and
monoenergetic neutron beams with En = 5-15 MeV.
Neutron-induced partial cross-sections were measured by
detecting prompt γ rays from the residual nuclei using
various combinations of clover and planar HPGe detectors in
the TUNL shielded neutron source area. Complimentary
activation measurements using DC neutron beams have also
been performed in open geometry in our second target area.
The neutron-induced activities were measured in the TUNL
low-background counting area. In this presentation, we
include detailed information about the irradiation
procedures and facilities and preliminary data on first
measurements using this capability.},
Doi = {10.1016/j.nimb.2007.04.097},
Key = {fds313677}
}
@article{fds313650,
Author = {Elhami, E and Orce, JN and Scheck, M and Mukhopadhyay, S and Choudry,
SN and McEllistrem, MT and Yates, SW and Angell, C and Boswell, M and Fallin, B and Howell, CR and Hutcheson, A and Karwowski, HJ and Kelley,
JH and Parpottas, Y and Tonchev, AP and Tornow, W},
Title = {Experimental Study of Low-Lying Structure of 94Zr with the
(n, n0) Reaction},
Journal = {Phys. Rev. C},
Volume = {78},
Number = {6},
Pages = {064303},
Year = {2008},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.78.064303},
Abstract = {The low-lying structure of 4094Zr was studied with the
(n,n'γ) reaction, and a level scheme was established based
on excitation function and γγ coincidence measurements.
Branching ratios, multipole mixing ratios, and spin
assignments were determined from angular distribution
measurements. Lifetimes of levels up to 3.4 MeV were
measured by the Doppler-shift attenuation method, and for
many transitions the reduced transition probabilities were
determined. In addition to the anomalous 22+ state, which
has a larger B(E2;22+→01+) value than the B(E2;21+→01+),
the experimental results revealed interesting and unusual
properties of the low-lying states in Zr94. In a simple
interpretation, the excited states are classified in two
distinct categories, i.e., those populating the 22+ state
and those decaying to the 21+ state. © 2008 The American
Physical Society.},
Doi = {10.1103/PhysRevC.78.064303},
Key = {fds313650}
}
@article{fds167410,
Author = {E. Elhami and J.N. Orce and M. Scheck and S. Mukhopadhyay and S.N.
Choudry, M.T. McEllistrem and S.W. Yates and C. Angell and M.
Boswell, B. Fallin and C.R. Howell and A. Hutcheson and H.J.
Karwowski, J.H. Kelley and Y. Parpottas and A.P. Tonchev and W.
Tornow},
Title = {Experimental study of the low-lying structure of 94Zr with
the (n,n'γ) reaction},
Journal = {Phys. Rev. C 78, 064303},
Year = {2008},
Key = {fds167410}
}
@article{fds313646,
Author = {Bowman, CD and Bowman, DC and Hill, T and Long, J and Tonchev, AP and Tornow, W and Trouw, F and Vogel, S and Walter, RL and Wender, S and Yuan,
V},
Title = {Measurements of thermal neutron diffraction and inelastic
scattering in reactor-grade graphite},
Journal = {Nuclear Science and Engineering},
Volume = {159},
Number = {2},
Pages = {182-198},
Year = {2008},
Month = {January},
ISSN = {0029-5639},
url = {http://dx.doi.org/10.13182/NSE159-182},
Abstract = {High-resolution Bragg-edge transmission measurements were
conducted on granular as well as solid samples of graphite
to understand the basis for a bulk measurement of the
diffusion length 24% larger than predicted by MCNP5 for bulk
reactor-grade graphite. High resolution enabled a
measurement of the total diffraction cross section from 1 to
200 meV. This was subtracted from the total cross section to
find the inelastic cross section in the same energy range.
Small-angle scattering, which has been thought to contribute
to the total cross section in the region of the lowest Bragg
edge, is shown not to be present in our measurement or in
those of others claiming to find it. Instead, neutron total
reflection from the surface of graphite microcrystals is
shown to contribute to the cross section at low energies.
Reactor-grade graphite is shown to have an inelastic
scattering cross section over most of the energy range
larger by at least 10 than the nearly perfect crystal
structure of pyrolytic graphite. The ratio of inelastic
scattering to diffraction at 25 meV for our graphite is
inferred to be twice as large as that of graphite
manufactured 50 yr ago, and we believe that our larger
diffusion coefficient is rooted in this difference. The
distortions in the microcrystalline structure introduced in
the manufacturing of the graphite studied here at 24°C are
found to be equivalent to the uncertainty in atom positions
seen in heating perfect crystal graphite to a temperature of
∼ 1800°C.},
Doi = {10.13182/NSE159-182},
Key = {fds313646}
}
@article{fds313667,
Author = {Chadwick, MB and Little, RC and Kawano, T and Talou, P and Viera, D and Jandel, M and Bredeweg, TA and White, MC and Tonchev, AP and Becker,
JA},
Title = {Actinide ENDF/B-VII cross section evaluations and validation
testing},
Journal = {International Conference on the Physics of Reactors 2008,
Physor 08},
Volume = {1},
Pages = {131-138},
Year = {2008},
Month = {January},
ISBN = {9781617821219},
Abstract = {We describe advances made recently at Los Alamos for
ENDF/B-VII, and for future ENDF releases, of actinide cross
section evaluations. Using americium as an illustrative
example, we describe recent experiments that have largely
confirmed the nuclear theory predictions that were the basis
for the ENDF/B-VII.0 data for these americium reactions. The
goal of this paper is to highlight some of the open issues
in our understanding of the actinide nuclear data -
especially for fast reactor applications - and show examples
of how experiment, theory, and integral data validation has
advanced our understanding. We will also describe the usage
of these data in MCNP and SN radiation transport simulations
of various integral critical systems, for both criticality
and for transmutation reaction rates.},
Key = {fds313667}
}
@article{fds313645,
Author = {Tonchev, AP and Angell, CT and Boswell, M and Crowell, AS and Fallin, B and Hammond, S and Howell, CR and Hutcheson, A and Karwowski, HJ and Kelley,
JH and Pedroni, RS and Tornow, W and Becker, JA and Dashdorj, D and Kenneally, J and MacRi, RA and Stoyer, MA and Wu, CY and Bond, E and Chadwick, MB and Fitzpatrick, J and Kawano, T and Rundberg, RS and Slemmons, A and Vieira, DJ and Wilhelmy, JB},
Title = {Measurement of the Am241(n,2n) reaction cross section from
7.6 MeV to 14.5 MeV},
Journal = {Physical Review C},
Volume = {77},
Number = {5},
Year = {2008},
Month = {May},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.77.054610},
Abstract = {The (n,2n) cross section of the radioactive isotope Am241
(T1/2=432.6 y) has been measured in the incident neutron
energy range from 7.6 to 14.5 MeV in steps of a few MeV
using the activation technique. Monoenergetic neutron beams
were produced via the H2(d,n)He3 reaction by bombarding a
pressurized deuterium gas cell with an energetic deuteron
beam at the TUNL 10-MV Van de Graaff accelerator facility.
The induced γ-ray activity of Am240 was measured with
high-resolution HPGe detectors. The cross section was
determined relative to Al, Ni, and Au neutron activation
monitor foils, measured in the same geometry. Good agreement
is obtained with previous measurements at around 9 and 14
MeV, whereas for a large discrepancy is observed when our
data are compared to those reported by Perdikakis near 11
MeV. Very good agreement is found with the END-B/VII
evaluation, whereas the JENDL-3.3 evaluation is in fair
agreement with our data. © 2008 The American Physical
Society.},
Doi = {10.1103/PhysRevC.77.054610},
Key = {fds313645}
}
@article{fds313653,
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},
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 = {fds313653}
}
@article{fds313654,
Author = {Bowman, CD and Bilpuch, EG and Bowman, DC and Crowell, AS and Howell,
CR and McCabe, K and Smith, GA and Tonchev, AP and Tornow, W and Violet, V and Vogelaar, RB and Walter, RL and Yingling, J},
Title = {Reducing Parasitic Thermal Neutron Absorption in Graphite by
30%},
Journal = {Nucl. Science and Eng.},
Volume = {161},
Number = {1},
Pages = {68},
Year = {2009},
ISSN = {0029-5639},
url = {http://dx.doi.org/10.13182/NSE161-68},
Abstract = {The results of two experiments combined show that the
diffusion length D for thermal neutrons in the graphite
studied is 24% larger than expected from classical
experiments and that the boron equivalent absorption is
smaller than expected and consistent with zero. Taken
together, the results indicate a reduction in parasitic
thermal neutron absorption in heterogeneous graphite
reactors by about 30%. The first experiment measured the
z-dependence of thermal neutron flux in a column of 12 t of
granular graphite with a neutron source at the bottom. A
second measurement was made by pulsing the column with a
neutron source at its center and measuring the neutron decay
rate as a function of time after a pure exponential decay
had been established. The diffusion coefficient D adjusted
to a density of 1.60 g/cm3 is 1.05 ± 0.03 cm compared with
the commonly accepted value of 0.85 ± 0.013 cm. The
absorption in our graphite owing to impurities was found to
be < 10% of that from carbon alone. The parameter ∑a/D
that measures neutron loss was determined to be 0.000235 ±
0.000026 cm-2 for a density of 1.60 g/cm3 and may be
compared with the commonly accepted value of 0.000340. The
performance of graphite thermal spectrum reactors
constructed using our graphite would be significantly
enhanced over present expectations because neutron loss to
graphite is a major factor in the neutron economy of
graphite-moderated thermal reactors.},
Doi = {10.13182/NSE161-68},
Key = {fds313654}
}
@article{fds313664,
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},
Year = {2009},
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 = {fds313664}
}
@article{fds313686,
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},
Year = {2009},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.79.047601},
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 = {fds313686}
}
@article{fds313702,
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},
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 = {fds313702}
}
@article{fds167269,
Author = {R. Longland and C. Iliadis and G. Rusev and A.P. Tonchev and R.J.
deBoer, J. Görres and M. Wiescher.},
Title = {Photoexcitation of astrophysically important states in
26Mg.},
Journal = {Rev. C 80, 055803},
Year = {2009},
Key = {fds167269}
}
@article{fds167270,
Author = {N. Pietralla. T.C. Li and A.P. Tonchev and M.W. Ahmed and T. Ahn and A.
Costin, J. Li and S. Muler and I.V. Pinayev and D. Savran and W. Tornow and H.R. Weller and V. WernY.K. Wu.},
Title = {Spin Assignment to n(p1/2)-hole coupled E1 excitations of
the odd-mass nucleus 207Pb at HIGS.},
Journal = {Phys. Lett. B 681, 134},
Year = {2009},
Key = {fds167270}
}
@article{fds167275,
Author = {A. Hutcheson and C. Angell and J.A. Becker and A.S. Crowell and D.
Dashdorj, B. Fallin and N. Fotiades and C.R. Howell and H. J.
Karwowski and T. Kawano and J.H. Kelley and E. Kwan and R.A. Macri and R.O.
Nelson, R. S. Pedroni and A.P. Tonchev and W.
Tornow.},
Title = {Neutron-induced partial γ-ray cross-section measurements on
238U},
Journal = {Phys. Rev. C 80, 014603},
Year = {2009},
Key = {fds167275}
}
@article{fds167276,
Author = {G. Rusev and A.P. Tonchev and W. Tornow and R. Schwengner and C. Sun and Y.
K.Wu.},
Title = {Multipole mixing ratios of transitions in
11B.},
Journal = {Phys. Rev. C 79, 047601},
Year = {2009},
Key = {fds167276}
}
@article{fds167279,
Author = {A.P. Tonchev and C. Angell and S. Hammond and A. Hutcheson and H.J.
Karwowski, J.H. Kelley and E. Kwan and G. Rusev and W. Tornow and N.
Tsoneva.},
Title = {Recent Results from the Excitation of Dipole States at the
HIγS Facility.},
Journal = {AIP 1090, 74},
Year = {2009},
Key = {fds167279}
}
@article{fds313700,
Author = {Bowman, CD and Bowman, DC and Bilpuch, EG and Crowell, AS and Howell,
CR and McCabe, K and Smith, GA and Tonchev, AP and Tornow, W and Vylet, V and Walter, RL},
Title = {Neutrons from a proton-driven deuterium target as a possible
competitor to spallation for nuclear energy
applications},
Journal = {Nuclear Science and Engineering},
Volume = {161},
Number = {1},
Pages = {119-124},
Year = {2009},
Month = {January},
ISSN = {0029-5639},
url = {http://dx.doi.org/10.13182/NSE161-119},
Abstract = {Measurements are reported on the yield of neutrons from
protons in the energy range from 7 to 17 MeV striking a
stopping-length target of deuterium gas. This combination of
beam and target is being investigated as an alternative to
spallation for accelerator-driven transmutation technology
with perhaps equivalent or lower energy cost per neutron.
The concept includes neutrons produced from a cascade of
reactions starting with the p + d reaction giving rise to
subsequent fusion neutrons and neutrons from higher-order
breakup reactions. In our application the incident proton
energy is expected to be -100 MeV so that most of the
neutrons produced in these reactions will be higher-energy
neutrons that can undergo multiplication in surrounding
beryllium or lead. The results reported here for lower
proton energies indicate that the expected fusion and
higher-order breakup reactions have been observed, and they
provide the basis for a measurement at 100 MeV to confirm
the larger proton-induced cascade benefits expected at
higher proton energies.},
Doi = {10.13182/NSE161-119},
Key = {fds313700}
}
@article{fds327379,
Author = {Gunasingha, R and Howell, C and Crowell, A and Fallin, B and Yoshizumi,
T and Song, H and Tonchev, A and Brady, S and Anderson‐evans,
C},
Title = {SU‐FF‐T‐436: Comparison of Neutron Doses to a Water
Target Exposed to a 10 MeV Neutron Beam: Foil Activation
Method Vs. Monte Carlo Simulations},
Journal = {Medical Physics},
Volume = {36},
Number = {6},
Pages = {2622-2623},
Year = {2009},
Month = {January},
url = {http://dx.doi.org/10.1118/1.3181918},
Abstract = {We developed a mouse dosimetry model for neutron beam, and
compared the calculated and simulated neutron doses for a
water target (mouse) exposed to a 10 MeV neutron beam. We
also estimated the longitudinal neutron dose profile for the
water target. A water bottle (a simulated mouse, 6 cm × 1.3
cm radius) was exposed to a flux of 10 MeV neutrons produced
via the d(d, n)He reaction using the Tandem accelerator at
Triangle Universities Nuclear Laboratory at Duke University.
An estimation of the neutron flux was obtained by neutron
activations of two sets of aluminum and gold activation
foils. One foil of each type was placed at the front and
back sides of the water target. The flux was then calculated
based on gamma spectroscopy of the irradiated foils using
HPGe detectors. A Monte Carlo (MC) simulation based on
FLUKA2008 code, was also used to estimate the 10 MeV neutron
dose for the same geometry. The highest neutron flux
measured using the activation technique was (8.538×106
+/− 6.89×104) n.cm−2.s−1 at the front end of the
target. Using neutron kerma factors from ICRU data tables,
the calculated dose rate to a water target at the location
of the foil was (1.890+/− 0.015) Gy.hr−1. Using the data
from the MC simulation, the calculated neutron dose to the
front end of the water target was (1.870 +/− 0.001)
Gy.hr−1. The dose calculated using the foil activation
technique was in good agreement with the MC results. The
slight discrepancy in the measured flux was likely the
result of the closer position of the activation foils to the
neutron source than the water bottle target, and also
absorption within the activation foils. Assuming these
results are in good agreement, we estimated the dose profile
for the simulated mouse. © 2009, American Association of
Physicists in Medicine. All rights reserved.},
Doi = {10.1118/1.3181918},
Key = {fds327379}
}
@article{fds313745,
Author = {Chadwick, MB and Little, RC and Kawano, T and Talou, P and Viera, D and Jandel, M and Bredeweg, TA and White, MC and Tonchev, AP and Becker,
JA},
Title = {Actinide ENDF/B-VII cross-section evaluations and validation
testing},
Journal = {Annals of Nuclear Energy},
Volume = {36},
Number = {3},
Pages = {258-262},
Year = {2009},
Month = {April},
ISSN = {0306-4549},
url = {http://dx.doi.org/10.1016/j.anucene.2008.11.011},
Abstract = {We describe advances made recently at Los Alamos for
ENDF/B-VII, and for future ENDF releases, of actinide
cross-section evaluations. Using americium as an
illustrative example, we describe recent experiments that
have largely confirmed the nuclear theory predictions that
were the basis for the ENDF/B-VII.0 data for these americium
reactions. The goal of this paper is to highlight some of
the open issues in our understanding of the actinide nuclear
data - especially for fast reactor applications - and show
examples of how experiment, theory, and integral data
validation has advanced our understanding. We will also
describe the usage of these data in MCNP and SN radiation
transport simulations of various integral critical systems,
for both criticality and for transmutation reaction rates.
© 2008 Elsevier Ltd.},
Doi = {10.1016/j.anucene.2008.11.011},
Key = {fds313745}
}
@article{fds313647,
Author = {Fritzsche, M and Pietralla, N and Ahmed, MW and Rusev, G and Savran, D and Tonchev, AP and Weller, HR and Zweidinger, M},
Title = {Weak-coupling of the neutron hole in 207Pb to
dipole excitations of 208Pb},
Journal = {Aip Conference Proceedings},
Volume = {1090},
Pages = {591-592},
Year = {2009},
Month = {April},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.3087098},
Abstract = {With the nearly monochromatic, linearly polarized photon
beam at the High Intensity ray source (HlγS) at DFELL
photon scattering experiments on 206207208pb have been
performed. With these experiments Pb(γγ) photon scattering
reactions could be used to determine spin and parity quantum
numbers and therefore study the v(3 p-1)-hole coupling of
207Pb to dipole excitations in 208Pb. © 2009 American
Institute of Physics.},
Doi = {10.1063/1.3087098},
Key = {fds313647}
}
@article{fds313651,
Author = {Tonchev, AP and Angell, C and Hammond, S and Hutcheson, A and Karwowski,
HJ and Kelley, JH and Kwan, E and Rusev, G and Tornow, W and Tsoneva,
N},
Title = {Recent results from the excitation of dipole states at the
HlγS facility},
Journal = {Aip Conference Proceedings},
Volume = {1090},
Pages = {74-78},
Year = {2009},
Month = {April},
ISBN = {978-0-7354-0623-0},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.3087126},
Abstract = {High-sensitivity studies of El and Ml excitations observed
in the 138Ba(γ,γ') reaction at energies below the neutron
emission threshold have been performed. The electric dipole
character of the so-called "pygmy" mode was experimentally
verified for excitations from 4.0 -8.6 MeV. The fine
structure of the Ml "spin-flip" mode was observed for the
first time in N = 82 nuclei. © 2009 American Institute of
Physics.},
Doi = {10.1063/1.3087126},
Key = {fds313651}
}
@article{fds313652,
Author = {Tonchev, AP and Hammond, S and Howell, CR and Huibregtse, C and Hutcheson, A and Karwowski, HJ and Kelley, JH and Kwan, E and Rusev, G and Tornow, W and Vieira, DJ and Wilhelmy, JB},
Title = {Photodisintegration cross section of241Am},
Journal = {Aip Conference Proceedings},
Volume = {1099},
Pages = {820-823},
Year = {2009},
Month = {May},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.3120165},
Abstract = {The photodisintegration cross section of radioactive 241Am
has been obtained for the first time using monoenergetic
γ-ray beams from the HIγS facility. The induced activity
of240Am produced via the 241Am(γ,n) reaction in the γ-ray
energy range from 9.5 to 16 MeV was measured by the
activation technique utilizing high resolution HPGe
detectors. The 241Am(γ,n) cross section was determined both
by measuring the absolute γ-ray flux and by comparison to
the 197Au(γ,n) and 58Ni(γ,n) cross section standards. The
experimental data for the 241Am(γ,n ) reaction in the giant
dipole resonance energy region is compared with statistical
nuclear-model calculations. © 2009 American Institute of
Physics.},
Doi = {10.1063/1.3120165},
Key = {fds313652}
}
@article{fds313648,
Author = {Rusev, G and Angell, CT and Beyer, R and Dönau, F and Erhard, M and Grosse, E and Hammond, SL and Hutcheson, AL and Frauendorf, S and Junghans, AR and Kawowski, HJ and Kelley, JH and Klug, J and Kosev, K and Kwan, E and Nair, C and Nikolov, N and Schilling, KD and Schwengner, R and Tonchev, AP and Tornow, W and Wagner, A},
Title = {Dipole-strength distributions below the giant dipole
resonance in the stable even-mass molybdenum
isotopes},
Journal = {Aip Conference Proceedings},
Volume = {1099},
Pages = {799-802},
Year = {2009},
Month = {May},
ISBN = {978-0-7354-0633-9},
ISSN = {0094-243X},
url = {http://dx.doi.org/10.1063/1.3120158},
Abstract = {Dipole-strength distributions in the stable even-mass
molybdenum isotopes up to the neutron-separation energies
have been studied in photon-scattering experiments with
bremsstrahlung at the superconducting electron accelerator
ELBE at the Research Center Dresden-Rossendorf, Germany, and
with mono-energetic photon beams at the High Intensity
Gamma-ray Source facility at Triangle Universities Nuclear
Laboratory. In order to determine the dipole-strength
distribution, statistical methods were developed for the
analysis of the measured spectra. The data obtained for the
stable even-mass molybdenum isotopes from the present
(γ,γ') experiments are combined with (γ,n) cross sections
from the literature resulting in a photoabsorption cross
section covering the full range from about 4 to 15 MeV,
which is of interest for nuclear structure as well as for
nuclear astrophysics network calculations. Novel information
about the low- energy tail of the Giant Dipole Resonance and
the energy spreading of its strength is derived. © 2009
American Institute of Physics.},
Doi = {10.1063/1.3120158},
Key = {fds313648}
}
@article{fds313666,
Author = {Hutcheson, A and Angell, C and Becker, JA and Crowell, AS and Dashdorj,
D and Fallin, B and Fotiades, N and Howell, CR and Karwowski, HJ and Kawano, T and Kelley, JH and Kwan, E and MacRi, RA and Nelson, RO and Pedroni, RS and Tonchev, AP and Tornow, W},
Title = {Cross sections for U238(n,n'γ) and U238(n,2nγ) reactions
at incident neutron energies between 5 and 14
MeV},
Journal = {Physical Review C},
Volume = {80},
Number = {1},
Year = {2009},
Month = {August},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.80.014603},
Abstract = {Precision measurements of U238(n,n'γ) and U238(n,2nγ)
partial cross sections have been performed at Triangle
Universities Nuclear Laboratory (TUNL) to improve crucial
data needed for testing nuclear reaction models in the
actinide mass region. A pulsed and monoenergetic neutron
beam was used in combination with high-resolution γ-ray
spectroscopy to obtain partial cross sections for incident
neutron energies between 5 and 14 MeV. γ-ray yields were
measured with high-purity germanium clover and planar
detectors. Measured partial cross-section data are compared
with previous results using white and monoenergetic neutron
beams and calculations from the GNASH and TALYS
Hauser-Feshbach statistical-model codes. Present
experimental results are in fair to good agreement with most
of the existing data for the U238(n,n'γ) reaction. However,
significant discrepancies are observed for the U238(n,2nγ)
reaction. © 2009 The American Physical Society.},
Doi = {10.1103/PhysRevC.80.014603},
Key = {fds313666}
}
@article{fds313655,
Author = {Hagmann, CA and Hall, JM and Johnson, MS and McNabb, DP and Kelley, JH and Huibregtse, C and Kwan, E and Rusev, G and Tonchev,
AP},
Title = {Transmission-based detection of nuclides with nuclear
resonance fluorescence using a quasimonoenergetic photon
source},
Journal = {Journal of Applied Physics},
Volume = {106},
Number = {8},
Pages = {084901-084901},
Year = {2009},
Month = {November},
ISSN = {0021-8979},
url = {http://dx.doi.org/10.1063/1.3238328},
Abstract = {We provide a detailed experimental validation of the concept
of transmission-based isotope detection. The dominant
background processes in this class of systems were measured
by studying the detection of U238 with a quasimonochromatic
(ΔE/E∼3%) photon beam. A notch develops in the spectrum
transmitted through our test objects due to the preferential
attenuation of photons with an energy that resonantly
excites a bound nuclear state in 238U near 2 MeV. The notch
was measured downstream of our test objects by means of
resonant photon scattering from a secondary 238U target. The
dominant backgrounds measured in the notch detector due to
radioactive decay and elastic scattering of the transmitted
beam are presented. Processes that refill the notch with
off-resonance photons will obscure the signal and result in
a higher probability of false negatives. A measurement of
the refill process produced a null result, and we report an
upper limit on the magnitude of the notch fill factor. ©
2009 American Institute of Physics.},
Doi = {10.1063/1.3238328},
Key = {fds313655}
}
@article{fds313658,
Author = {Longland, R and Iliadis, C and Rusev, G and Tonchev, AP and Deboer, RJ and Görres, J and Wiescher, M},
Title = {Photoexcitation of astrophysically important states in
Mg26},
Journal = {Physical Review C},
Volume = {80},
Number = {5},
Pages = {055803},
Year = {2009},
Month = {November},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.80.055803},
Abstract = {We performed a nuclear resonance fluorescence experiment to
determine the energy and quantum numbers of excited states
in Mg26. Spin-parity ambiguities of excited states in Mg26,
the compound nucleus for the s-process neutron source
Ne22(α,n)Mg25, result in large uncertainties in the
reaction rates. The present work uses the monoenergetic
γ-ray beam from the High-Intensity γ-ray Source to probe
states in the excitation energy range of Ex=10.8 to 11.4MeV.
Five excited states were observed and unambiguous quantum
numbers were assigned at Ex=10 573.3(8)keV (Jπ=1-), Ex=10
647.3(8)keV (Jπ=1+), Ex=10 805.7(7)keV (Jπ=1-), Ex=10
949.1(8)keV (Jπ=1-), and Ex=11 153.5(10)keV (Jπ=1+). The
two natural parity states, located between the α-particle
and neutron thresholds, are expected to significantly
influence the rate of the competing Ne22(α,γ)Mg26
reaction. An important finding of this work is that the
Ex=11 154keV level has unnatural parity, contrary to
previous results, and thus does not contribute to the
Ne22+α reaction rates. © 2009 The American Physical
Society.},
Doi = {10.1103/PhysRevC.80.055803},
Key = {fds313658}
}
@article{fds313679,
Author = {Bowman, CD and Vogelaar, RB and Bilpuch, EG and Bowman, DC and Howell,
CR and Pierson, MA and Tonchev, AP and Tornow, W},
Title = {Basis for green energy multiplier*alternative nuclear
technology (GEM*ART)},
Journal = {Transactions of the American Nuclear Society},
Volume = {100},
Pages = {578-579},
Year = {2009},
Month = {December},
ISSN = {0003-018X},
Key = {fds313679}
}
@article{fds184703,
Author = {A.P. Tonchev and S. Hammond and C.R. Howell and A. Hutcheson and T.
Kawano, J.H. Kelley and E. Kwan and G. Rusev and W. Tornow and D.
Vieira and J.B. Wilhelmy},
Title = {Measurement of the 241Am(γ,n)240Am reaction in the giant
dipole resonance region},
Journal = {Phys. Rev. C},
Volume = {82},
Pages = {054620},
Year = {2010},
Key = {fds184703}
}
@article{fds313669,
Author = {Pietralla, N and Li, TC and Fritzsche, MW and Ahmed, MW and Savran, D and Tonchev, AP and Tornow, W and Weller, HR and Werner,
V},
Title = {Spin and parity assignments to dipole excitations of the
odd-mass nucleus 207Pb from nuclear resonance
fluorescence experiments with linearly-polarized γ-ray
beams},
Journal = {Journal of Physics: Conference Series},
Volume = {205},
Pages = {012036-012036},
Year = {2010},
Month = {January},
url = {http://dx.doi.org/10.1088/1742-6596/205/1/012036},
Abstract = {Pb(γ→,γ′) photon scattering reactions were studied [1]
with the nearly monochromatic, linearly polarized photon
beams at the High Intensity γ-ray Source (HIγS) 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. © 2010 IOP
Publishing Ltd.},
Doi = {10.1088/1742-6596/205/1/012036},
Key = {fds313669}
}
@article{fds313672,
Author = {Tonchev, AP and Hammond, SL and Kelley, JH and Kwan, E and Lenske, H and Rusev, G and Tornow, W and Tsoneva, N},
Title = {Spectral structure of the pygmy dipole resonance.},
Journal = {Physical Review Letters},
Volume = {104},
Number = {7},
Pages = {072501},
Year = {2010},
Month = {February},
ISSN = {0031-9007},
url = {http://hdl.handle.net/10161/4292 Duke open
access},
Abstract = {High-sensitivity studies of E1 and M1 transitions observed
in the reaction 138Ba(gamma,gamma{'}) at energies below the
one-neutron separation energy have been performed using the
nearly monoenergetic and 100% linearly polarized photon
beams of the HIgammaS facility. The electric dipole
character of the so-called "pygmy" dipole resonance was
experimentally verified for excitations from 4.0 to 8.6 MeV.
The fine structure of the M1 "spin-flip" mode was observed
for the first time in N=82 nuclei.},
Doi = {10.1103/physrevlett.104.072501},
Key = {fds313672}
}
@article{fds313744,
Author = {Carson, S and Iliadis, C and Cesaratto, J and Champagne, A and Downen,
L and Ivanovic, M and Kelley, J and Longland, R and Newton, JR and Rusev,
G and Tonchev, AP},
Title = {Ratio of germanium detector peak efficiencies at photon
energies of 4.4 and 11.7 MeV: Experiment versus
simulation},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {618},
Number = {1-3},
Pages = {190-198},
Year = {2010},
Month = {June},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2010.02.128},
Abstract = {Full-energy peak efficiencies of germanium detectors are
frequently investigated at γ-ray energies below 4 MeV using
calibrated radioactive sources, while very accurate peak
efficiencies for higher photon energies are essentially
non-existent. Peak efficiencies in the energy range of E γ
= 4212 MeV are crucial for a number of applications,
including nuclear astrophysics measurements of fusion
reactions and resonance fluorescence experiments. We report
on a novel method, using the 163 keV resonance in the 11
B(p, γ)12C reaction, of measuring accurately the ratio of
full-energy peak efficiencies at 4.44 and 11.66 MeV. We
derive this ratio for three different detector-target
distances (3, 12 and 26cm) directly from measured peak
intensities and demonstrate that corrections are small
(γ-ray branching ratios, angular correlations, coincidence
summing). Our measured full-energy peak efficiency ratios
have a precision of 1.4-1.6%. Another important goal of our
study was to determine to what precision full-energy peak
efficiencies at high γ-ray energies can be predicted using
the simulation codes Geant3 and Geant4. We imaged our
detector using computed tomography and radiographs in order
to extract reliable detector crystal dimensions. Based on
these results, extensive computer simulations are performed.
We find that the simulation results agree with the measured
peak efficiency ratios within an uncertainty of 1.6% for
Geant4 and 2.6% for Geant3. Our results are useful for
assigning uncertainties when peak efficiencies are
extrapolated from low energy data to high energies based on
simulations only. © 2010 Elsevier B.V.},
Doi = {10.1016/j.nima.2010.02.128},
Key = {fds313744}
}
@article{fds313661,
Author = {DeBoer, RJ and Wiescher, M and Görres, J and Longland, R and Iliadis,
C and Rusev, G and Tonchev, AP},
Title = {Photoexcitation of astrophysically important states in Mg26.
II. Ground-state-transition partial widths},
Journal = {Physical Review C},
Volume = {82},
Number = {2},
Pages = {025802},
Year = {2010},
Month = {August},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.82.025802},
Abstract = {The level structure of Mg26 near the neutron-separation
energy, which is of interest for s-process nucleosynthesis,
was studied at the High Intensity Gamma-Ray Source of the
Triangle Universities Nuclear Laboratory using the method of
nuclear resonance fluorescence. A nearly monoenergetic and
linearly polarized γ-ray beam was used to scan the
excitation energy range from 10.5 to 11.7 MeV. For the five
states observed, the total widths and partial widths are
determined. Precise measurement of these widths is necessary
for the prediction of neutron production for the s-process.
© 2010 The American Physical Society.},
Doi = {10.1103/PhysRevC.82.025802},
Key = {fds313661}
}
@article{fds313747,
Author = {Brady, SL and Gunasingha, R and Yoshizumi, TT and Howell, CR and Crowell, AS and Fallin, B and Tonchev, AP and Dewhirst,
MW},
Title = {A feasibility study using radiochromic films for fast
neutron 2D passive dosimetry.},
Journal = {Phys Med Biol},
Volume = {55},
Number = {17},
Pages = {4977-4992},
Year = {2010},
Month = {September},
ISSN = {0031-9155},
url = {http://dx.doi.org/10.1088/0031-9155/55/17/007},
Abstract = {The objective of this paper is threefold: (1) to establish
sensitivity of XRQA and EBT radiochromic films to fast
neutron exposure; (2) to develop a film response to
radiation dose calibration curve and (3) to investigate a
two-dimensional (2D) film dosimetry technique for use in
establishing an experimental setup for a radiobiological
irradiation of mice and to assess the dose to the mice in
this setup. The films were exposed to a 10 MeV neutron beam
via the (2)H(d,n)(3)He reaction. The XRQA film response was
a factor of 1.39 greater than EBT film response to the 10
MeV neutron beam when exposed to a neutron dose of 165 cGy.
A film response-to-soft tissue dose calibration function was
established over a range of 0-10 Gy and had a goodness of
fit of 0.9926 with the calibration data. The 2D film
dosimetry technique estimated the neutron dose to the mice
by measuring the dose using a mouse phantom and by placing a
piece of film on the exterior of the experimental mouse
setup. The film results were benchmarked using Monte Carlo
and aluminum (Al) foil activation measurements. The
radiochromic film, Monte Carlo and Al foil dose measurements
were strongly correlated, and the film within the mouse
phantom agreed to better than 7% of the externally mounted
films. These results demonstrated the potential application
of radiochromic films for passive 2D neutron
dosimetry.},
Doi = {10.1088/0031-9155/55/17/007},
Key = {fds313747}
}
@article{fds313660,
Author = {Tonchev, AP and Hammond, SL and Howell, CR and Huibregtse, C and Hutcheson, A and Kelley, JH and Kwan, E and Raut, R and Rusev, G and Tornow, W and Kawano, T and Vieira, DJ and Wilhelmy,
JB},
Title = {Measurement of the Am241(γ,n)Am240
reaction in the giant dipole resonance region},
Journal = {Physical Review C},
Volume = {82},
Number = {5},
Year = {2010},
Month = {November},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.82.054620},
Abstract = {The photodisintegration cross section of the radioactive
nucleus Am 241 has been obtained using activation techniques
and monoenergetic γ-ray beams from the HIγS facility. The
induced activity of Am 240 produced via the Am241(γ,n)
reaction was measured in the energy interval from 9 to 16
MeV utilizing high-resolution γ-ray spectroscopy. The
experimental data for the Am241(γ ,n) reaction in the giant
dipole resonance energy region are compared with statistical
nuclear-model calculations. © 2010 The American Physical
Society.},
Doi = {10.1103/PhysRevC.82.054620},
Key = {fds313660}
}
@article{fds313691,
Author = {Raut, R and Crowell, AS and Fallin, B and Howell, CR and Huibregtse, C and Kelley, JH and Kawano, T and Kwan, E and Rusev, G and Tonchev, AP and Tornow, W and Vieira, DJ and Wilhelmy, JB},
Title = {Cross section measurements of neutron induced reactions on
GaAs using monoenergetic beams from 7.5 to 15
MeV},
Journal = {Journal of Physics: Conference Series},
Volume = {312},
Number = {SECTION 6},
Pages = {044621},
Year = {2011},
Month = {January},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1088/1742-6596/312/6/062008},
Abstract = {Cross section measurements for the neutron induced reactions
on GaAs have been carried out at ten different neutron
energies from 7.5 to 15 MeV, using the activation technique.
The monoenergetic neutron beams were produced via the
2H(d,n)3He reaction, known for it's high neutron yield in
the chosen energy regime. GaAs samples were activated along
with the Au and Al monitor foils, for estimating the
incident neutron flux. The induced activiy was measured
using high resolution γ-ray spectroscopy. Five reaction
channels viz., 69Ga(n, 2n) Ga, 69Ga(n,p)69mZn,
71Ga(n,p)71mZn, 75As(n, 2n)74As and 75As(n,p)75Ge, have been
reported for the comprehensive cross section measurements.
The results are compared with the existing literature data
and the available evaluations. Statistical model
calculations, based on the Hauser-Feshbach formalism, have
been carried out using the TALYS and EMPIRE codes and are
compared with the experimental values.},
Doi = {10.1088/1742-6596/312/6/062008},
Key = {fds313691}
}
@article{fds313692,
Author = {Rusev, G and Adekola, AS and Dönau, F and Frauendorf, S and Hammond,
SL and Huibregtse, C and Kelley, JH and Kwan, E and Schwengner, R and Tonchev, AP and Tornow, W and Wagner, A},
Title = {Fine structure of the giant M1 resonance in
90Zr},
Journal = {Journal of Physics: Conference Series},
Volume = {312},
Number = {SECTION 9},
Year = {2011},
Month = {January},
ISSN = {1742-6588},
url = {http://dx.doi.org/10.1088/1742-6596/312/9/092053},
Abstract = {M1 excitations in the 90Zr nucleus have been studied in a
photon-scattering experiment with monoenergetic and 100%
linearly-polarized beams from 7 to 11 MeV. More than 40 Jπ
= 1+ states were identified for the first time from the
observed ground-state transitions revealing the fine
structure of the giant M1 resonance with center of gravity
of 9 MeV and sum strength of 3.8(3) μN2. The results of the
present work are compared with predictions from the shell
model and the quasi-particle random-phase
approximation.},
Doi = {10.1088/1742-6596/312/9/092053},
Key = {fds313692}
}
@article{fds313699,
Author = {Tonchev, AP and Hammond, SL and Kelley, JH and Kwan, E and Lenske, H and Raut, R and Rusev, G and Tornow, W and Tsoneva, N},
Title = {Coarse and fine structure of the pygmy dipole
resonance},
Journal = {Journal of Physics: Conference Series},
Volume = {312},
Number = {SECTION 9},
Pages = {092058-092058},
Year = {2011},
Month = {January},
ISSN = {1742-6588},
url = {http://dx.doi.org/10.1088/1742-6596/312/9/092058},
Abstract = {High resolution and sensitivity studies of the nuclear
dipole response in 138Ba have been performed in (γ, γ′)
experiment. The electric dipole character of the "pygmy"
mode was experimentally verified for excitations from 4.0 to
8.5 MeV. Experimental findings have been compared with the
quasiparticle phonon model. A new understanding about the
character and the evolution of the pygmy resonance emerges
from comparison of the experimental results with the
theoretical calculations.},
Doi = {10.1088/1742-6596/312/9/092058},
Key = {fds313699}
}
@article{fds313670,
Author = {Isaak, J and Savran, D and Fritzsche, M and Galaviz, D and Hartmann, T and Kamerdzhiev, S and Kelley, JH and Kwan, E and Pietralla, N and Romig, C and Rusev, G and Sonnabend, K and Tonchev, AP and Tornow, W and Zilges,
A},
Title = {Investigation of low-lying electric dipole strength in the
semimagic nucleus Ca44},
Journal = {Physical Review C},
Volume = {83},
Number = {3},
Pages = {034304},
Year = {2011},
Month = {March},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.83.034304},
Abstract = {The dipole-strength distribution in the semimagic nucleus
Ca44 has been measured up to 10 MeV excitation energy in
photon-scattering experiments using bremsstrahlung and
monoenergetic 100% linearly polarized photon beams. The
combination of both measurements allows a clear
determination of spin and parity quantum numbers of the
excited states as well as absolute cross sections and
transition probabilities. The results show that the majority
of the dipole strength in Ca44 below 10 MeV is due to E1
transitions while M1 strength plays only a minor role. The
experimental results are compared to the strength in the
neighboring doubly magic nuclei Ca40,48 and to microscopic
calculations within the extended theory of finite Fermi
systems in order to investigate the evolution of the
low-lying E1 strength in this isotopic chain. Both,
experiment and calculations, show a nontrivial dependence of
the total E1 strength as a function of the neutron number.
© 2011 American Physical Society.},
Doi = {10.1103/PhysRevC.83.034304},
Key = {fds313670}
}
@article{fds313676,
Author = {Kwan, E and Rusev, G and Adekola, AS and Dönau, F and Hammond, SL and Howell, CR and Karwowski, HJ and Kelley, JH and Pedroni, RS and Raut, R and Tonchev, AP and Tornow, W},
Title = {Discrete deexcitations in U235 below 3 MeV from nuclear
resonance fluorescence},
Journal = {Physical Review C},
Volume = {83},
Number = {4},
Pages = {041601},
Year = {2011},
Month = {April},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.83.041601},
Abstract = {Gamma-ray transitions in U235 were measured using the (γ,
γ') reaction below 3 MeV. The nuclear-resonance-fluorescence
experiment was carried out at the High-Intensity γ-ray
Source facility using nearly monoenergetic and circularly
polarized photon beams. More than 20 transitions
corresponding to deexcitations to the ground state and
low-lying levels in U235 were observed. The integrated cross
sections to the excited levels and intensities of branching
transitions were deduced. The experimental results are
compared with predictions from a quasiparticle random-phase
approximation in a deformed basis. © 2011 American Physical
Society.},
Doi = {10.1103/PhysRevC.83.041601},
Key = {fds313676}
}
@article{fds313828,
Author = {Raut, R and Crowell, AS and Fallin, B and Howell, CR and Huibregtse, C and Kelley, JH and Kawano, T and Kwan, E and Rusev, G and Tonchev, AP and Tornow, W and Vieira, DJ and Wilhelmy, JB},
Title = {Cross-section measurements of neutron-induced reactions on
GaAs using monoenergetic beams from 7.5 to 15
MeV},
Journal = {Physical Review C},
Volume = {83},
Number = {4},
Pages = {062008-062008},
Year = {2011},
Month = {April},
url = {http://dx.doi.org/10.1103/PhysRevC.83.044621},
Abstract = {Cross-section measurements for neutron-induced reactions on
GaAs have been carried out at twelve different neutron
energies from 7.5 to 15 MeV using the activation technique.
The monoenergetic neutron beams were produced via the
H2(d,n)He3 reaction. GaAs samples were activated along with
Au and Al monitor foils to determine the incident neutron
flux. The activities induced by the reaction products were
measured using high-resolution γ-ray spectroscopy. Cross
sections for five reaction channels, viz., Ga69(n,2n)Ga68,
Ga69(n,p)Zn69m, Ga71(n,p)Zn71m, As75(n,2n)As74, and
As75(n,p)Ge75, are reported. The results are compared with
the previous measurements and available data evaluations.
Statistical-model calculations, based on the Hauser-Feshbach
formalism, have been carried out using the TALYS and the
COH3 codes and are compared with the experimental results.
© 2011 American Physical Society.},
Doi = {10.1103/PhysRevC.83.044621},
Key = {fds313828}
}
@article{fds313678,
Author = {Tornow, W and Karwowski, HJ and Kelley, JH and Raut, R and Rusev, G and Stave, SC and Tonchev, AP and Deltuva, A and Fonseca, AC and Marcucci,
LE and Viviani, M and Kievsky, A and Golak, J and Skibiński, R and Witała, H and Schiavilla, R},
Title = {Two-body photodisintegration of 3He between 7 and 16
MeV},
Journal = {Physics Letters B},
Volume = {702},
Number = {2-3},
Pages = {121-126},
Year = {2011},
Month = {August},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2011.06.080},
Abstract = {A comprehensive data set is reported for the two-body
photodisintegration cross section of 3He using
mono-energetic photon beams at eleven energies between 7.0
and 16.0 MeV. A He3+Xe high-pressure gas scintillator served
as target and detector. Although our data are in much better
agreement with our state-of-the-art theoretical calculations
than the majority of the previous data, these calculations
underpredict the new data by about 10%. This disagreement
suggests an incomplete understanding of the dynamics of the
three-nucleon system and its response to electromagnetic
probes. © 2011 Elsevier B.V.},
Doi = {10.1016/j.physletb.2011.06.080},
Key = {fds313678}
}
@article{fds313706,
Author = {Raut, R and Banu, A and Iliadis, C and Kelley, JH and Rusev, G and Schwengner, R and Tonchev, AP and Tornow, W},
Title = {Cross-section measurements of the 86Kr(γ, n)
reaction to probe the s-process branching at
85Kr},
Journal = {Journal of Physics: Conference Series},
Volume = {337},
Number = {1},
Year = {2012},
Month = {January},
ISSN = {1742-6588},
url = {http://dx.doi.org/10.1088/1742-6596/337/1/012048},
Abstract = {For the first time, cross-section measurements were carried
out for the 86Kr(γ, n) reaction in order to probe the
s-process branching point nucleus 85Kr. The branching point
nuclei in the s-process path are of importance in testing
and constraining the nucleosynthesis models. Cross-section
measurement for the photoneutron reaction on the
neighbouring stable isotope is carried out to deduce the
aforesaid neutron capture cross-section, as has been adopted
in the present case of 85Kr branching point. The
cross-section results from the 86Kr(γ, n) reaction were
compared with the statistical model calculations using TALYS
code.},
Doi = {10.1088/1742-6596/337/1/012048},
Key = {fds313706}
}
@article{fds313708,
Author = {Beller, J and Wagner, J and Ahmed, M and Deleanu, D and Filipescu, DM and Glodariu, T and Isaak, J and Kelley, JH and Kwan, E and Pietralla, N and Raut, R and Romig, C and Rusev, G and Scheck, M and Stave, SC and Tonchev,
A and Tornow, W and Weller, HR and Zamfir, NV and Zweidinger,
M},
Title = {Energy separation of the 1+/1- parity
doublet in 20Ne},
Journal = {Journal of Physics: Conference Series},
Volume = {366},
Number = {1},
Pages = {012003-012003},
Year = {2012},
Month = {January},
url = {http://dx.doi.org/10.1088/1742-6596/366/1/012003},
Abstract = {The parity doublet of 1+/1- states of Ne-20 at 11.26 MeV
excitation energy is one of the best known test cases to
study the weak part of the nuclear Hamiltonian. The
feasibility of parity violation experiments depend on the
effective nuclear enhancement factor (RN/|E(1 +) - E(l-)|)
which amplifies the impact of the matrix element of the weak
interaction on observables indicating parity mixing. An
extreme large value of Rn/|E(1+) - E(l-)| = (670 ± 7000)
MeV-1 was reported for the doublet in 20Ne. The large
uncertainty depends amongst others on the large uncertainty
of |E(1 +) - E(l-)| = 7.7±5.5 keV of the parity doublet.
Nuclear resonance fluorescence (NRF) experiments with
linearly and circularly polarized photon beams were
performed at the High Intensity Gamma-Ray Source at Duke
University, Durham, NC, USA, to determine the energy
difference of the parity doublet with higher precision. The
different angular distributions for 0+ → 1- → 0+ and 0+
→ 1+ → 0+ NRF cascades in polarized γ-ray beams were
used to determine the energy difference of the parity
doublet to 2.9(13) keV.},
Doi = {10.1088/1742-6596/366/1/012003},
Key = {fds313708}
}
@article{fds313696,
Author = {Raut, R and Tornow, W and Ahmed, MW and Crowell, AS and Kelley, JH and Rusev, G and Stave, SC and Tonchev, AP},
Title = {Photodisintegration cross section of the reaction
(4)He(γ,p)(3)H between 22 and 30 MeV.},
Journal = {Physical Review Letters},
Volume = {108},
Number = {4},
Pages = {042502},
Year = {2012},
Month = {January},
ISSN = {0031-9007},
url = {http://dx.doi.org/10.1103/physrevlett.108.042502},
Abstract = {The two-body photodisintegration cross section of (4)He into
a proton and triton was measured with monoenergetic photon
beams in 0.5 MeV energy steps between 22 and 30 MeV.
High-pressure (4)He-Xe gas scintillators of various (4)He/Xe
ratios served as targets and detectors. Pure Xe gas
scintillators were used for background studies. A NaI
detector together with a plastic scintillator paddle was
employed for determining the incident photon flux. Our
comprehensive data set follows the trend of the theoretical
calculations of the Trento group very well, although our
data are consistently lower in magnitude by about 5%.
However, they differ significantly from the majority of the
previous data, especially from the recent data of Shima et
al. The latter data had put into question the validity of
theoretical approaches used to calculate core-collapse
supernova explosions and big-bang nucleosynthesis abundances
of certain light nuclei.},
Doi = {10.1103/physrevlett.108.042502},
Key = {fds313696}
}
@article{fds313707,
Author = {Hammond, SL and Adekola, AS and Angell, CT and Karwowski, HJ and Kwan,
E and Rusev, G and Tonchev, AP and Tornow, W and Howell, CR and Kelley,
JH},
Title = {Dipole response of 238U to polarized photons below the
neutron separation energy},
Journal = {Physical Review C},
Volume = {85},
Number = {4},
Year = {2012},
Month = {April},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.85.044302},
Abstract = {Nuclear resonance fluorescence experiments were carried out
at the High-Intensity γ-ray Source facility at Triangle
Universities Nuclear Laboratory to characterize the
low-energy dipole structure of 238U using 100% linearly
polarized photon beams from 2.0 to 6.2 MeV. 113 transitions
corresponding to de-excitations to the ground state in 238U
were observed and the energy, spin, parity, integrated cross
section, reduced width, and branching ratio were determined
for each of these identified levels. The total E1 γ-ray
interaction cross section was calculated and it was deduced
that the observed concentration of low-lying E1 transitions
were excited from the low-energy tail of the giant dipole
resonance and were not a pygmy dipole resonance. Comparisons
were made between quasiparticle random-phase approximation
calculations and the experimentally observed strength. The
observed and predicted M1 strength agreed well with each
other. However, there was no similar agreement for the E1
strength. © 2012 American Physical Society.},
Doi = {10.1103/PhysRevC.85.044302},
Key = {fds313707}
}
@article{fds313709,
Author = {Tornow, W and Kelley, JH and Raut, R and Rusev, G and Tonchev, AP and Ahmed, MW and Crowell, AS and Stave, SC},
Title = {Photodisintegration cross section of the reaction
4He(γ,n)3He at the giant dipole resonance
peak},
Journal = {Physical Review C},
Volume = {85},
Number = {6},
Year = {2012},
Month = {June},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.85.061001},
Abstract = {The photodisintegration cross section of 4He into a neutron
and helion was measured at incident photon energies of 27.0,
27.5, and 28.0 MeV. A high-pressure 4He-Xe gas scintillator
served as target and detector while a pure Xe gas
scintillator was used for background measurements. A NaI
detector in combination with the standard HIγS scintillator
paddle system was employed for absolute photon-flux
determination. Our data are in good agreement with the
theoretical prediction of the Trento group and the recent
data of Nilsson but deviate considerably from the
high-precision data of Shima. © 2012 American Physical
Society.},
Doi = {10.1103/PhysRevC.85.061001},
Key = {fds313709}
}
@article{fds313711,
Author = {Massarczyk, R and Schwengner, R and Dönau, F and Litvinova, E and Rusev, G and Beyer, R and Hannaske, R and Junghans, AR and Kempe, M and Kelley, JH and Kögler, T and Kosev, K and Kwan, E and Marta, M and Matic,
A and Nair, C and Raut, R and Schilling, KD and Schramm, G and Stach, D and Tonchev, AP and Tornow, W and Trompler, E and Wagner, A and Yakorev,
D},
Title = {Electromagnetic dipole strength of 136Ba below the neutron
separation energy},
Journal = {Physical Review C},
Volume = {86},
Number = {1},
Year = {2012},
Month = {July},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.86.014319},
Abstract = {The electromagnetic dipole strength of the nucleus 136Ba has
been investigated. Two measurements were performed with
electron energies of 7.0 and 11.4 MeV at the bremsstrahlung
facility at the ELBE accelerator of the Helmholtz-Zentrum
Dresden-Rossendorf. Photon scattering experiments on the
same nucleus have been performed at the high-intensity
gamma-ray source (HIγS) facility of the Triangle
Universities Nuclear Laboratory between 4.7 and 9.3 MeV. The
geant4 code has been used to determine detector response and
non-nuclear scattered events. Thus it is possible to account
for the dipole strength in the quasicontinuum of
unresolvable transitions. A statistical code was used to
simulate inelastic transitions and to determine the
branching ratios of transitions to the ground state. The
resulting photoabsorption cross section is compared to
quasiparticle random-phase approximation and relativistic
quasiparticle time blocking approximation calculations. ©
2012 American Physical Society.},
Doi = {10.1103/PhysRevC.86.014319},
Key = {fds313711}
}
@article{fds313710,
Author = {Johnson, MS and Hagmann, CA and Hall, JM and McNabb, DP and Kelley, JH and Huibregtse, C and Kwan, E and Rusev, G and Tonchev,
AP},
Title = {Searching for illicit materials using nuclear resonance
fluorescence stimulated by narrow-band photon
sources},
Journal = {Nuclear Instruments and Methods in Physics Research Section
B: Beam Interactions With Materials and Atoms},
Volume = {285},
Pages = {72-85},
Year = {2012},
Month = {August},
ISSN = {0168-583X},
url = {http://dx.doi.org/10.1016/j.nimb.2012.05.029},
Abstract = {We report the results of an experimental study of the
sensitivity of two distinct classes of systems that exploit
nuclear resonance fluorescence (NRF) to search for illicit
materials in containers. One class of systems is based on
the direct detection of NRF photons emitted from isotopes of
interest. The other class infers the presence of a
particular isotope by observing the preferential attenuation
of resonant photons in the incident beam. We developed a
detailed analytical model for both approaches. We performed
experiments to test the model using depleted uranium as a
surrogate for illicit material and used tungsten as a random
choice for shielding. We performed the experiments at Duke
University's High Intensity Gamma Source (HIGS). Using the
methodology we detail in this paper one can use this model
to estimate the performance of potential inspection systems
in certifying containers as free of illicit materials and
for detecting the presence of those same materials. © 2012
Elsevier B.V. All rights reserved.},
Doi = {10.1016/j.nimb.2012.05.029},
Key = {fds313710}
}
@article{fds313637,
Author = {Buntain, J and Lugaro, M and Iliadis, C and Raut, R and Tonchev, A and Karakas, AI},
Title = {Kr Isotopic Compositions in Stardust SiC grains and AGB
Winds},
Journal = {Proceedings of Science},
Year = {2012},
Month = {December},
Abstract = {Krypton (Kr) is a heavy noble gas that does not chemically
react and hence does not condense into dust. However, it is
found in trace amounts inside stardust silicon carbide (SiC)
grains in meteorites, which are believed to have condensed
in the C-rich envelopes of low-mass asymptotic giant branch
(AGB) stars. The measured isotopic composition of Kr clearly
reveals the signature of the s (slow neutron-capture)
process. It is likely that Kr is ionised and implanted in
stardust SiC grains via stellar winds in two different
evolutionary phases: one during the AGB phase in small
grains showing low 86Kr/82Kr, and another during the
post-AGB phase in large grains showing high 86Kr/82Kr
ratios. The low 86Kr/82Kr ratios observed in stardust SiC
grains can be explained by model predictions of AGB winds.
On the other hand, to explain the high 86Kr/82Kr ratios we
need to look at the material in the winds of the post-AGB
phase. We present Kr isotopic compositions predicted by
s-process AGB-star models of different masses and
metallicities, and compare them to data from stardust SiC
grains. We find that to match the high 86Kr/82Kr ratios
observed in the large grains, a proton ingestion during the
thermal pulse (TP) may be required. We also find that the
84Kr(n,γ)85Kr neutron-capture cross section should to be
lower than the current estimate in order for our models to
match the pure s-process value. © Copyright owned by the
author(s) under the terms of the Creative Commons
Attribution-NonCommercial-ShareAlike Licence.},
Key = {fds313637}
}
@article{fds313746,
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},
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 = {fds313746}
}
@article{fds313722,
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},
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 = {fds313722}
}
@article{fds313712,
Author = {Rusev, G and Tsoneva, N and Dönau, F and Frauendorf, S and Schwengner,
R and Tonchev, AP and Adekola, AS and Hammond, SL and Kelley, JH and Kwan,
E and Lenske, H and Tornow, W and Wagner, A},
Title = {Fine structure of the giant M1 resonance in
90Zr.},
Journal = {Physical Review Letters},
Volume = {110},
Number = {2},
Pages = {022503},
Year = {2013},
Month = {January},
url = {http://www.ncbi.nlm.nih.gov/pubmed/23383897},
Abstract = {The M1 excitations in the nuclide 90Zr have been studied in
a photon-scattering experiment with monoenergetic and
linearly polarized beams from 7 to 11 MeV. More than 40
J(π)=1+ states have been identified from observed
ground-state transitions, revealing the fine structure of
the giant M1 resonance with a centroid energy of 9 MeV and a
sum strength of 4.17(56) μ(N)(2). The result for the total
M1 strength and its fragmentation are discussed in the
framework of the three-phonon quasiparticle-phonon
model.},
Doi = {10.1103/physrevlett.110.022503},
Key = {fds313712}
}
@article{fds313713,
Author = {Schwengner, R and Massarczyk, R and Rusev, G and Tsoneva, N and Bemmerer, D and Beyer, R and Hannaske, R and Junghans, AR and Kelley,
JH and Kwan, E and Lenske, H and Marta, M and Raut, R and Schilling, KD and Tonchev, A and Tornow, W and Wagner, A},
Title = {Pygmy dipole strength in 86Kr and systematics of N=50
isotones},
Journal = {Physical Review C},
Volume = {87},
Number = {2},
Year = {2013},
Month = {February},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.87.024306},
Abstract = {The dipole strength of the N=50 nucleus 86Kr was studied in
photon-scattering experiments using bremsstrahlung produced
with electron beams of energies of 7.9 and 11.2 MeV
delivered by the linear accelerator ELBE as well as using
quasimonoenergetic and linearly polarized γ rays of 10
energies within the range from 4.7 to 9.3 MeV delivered by
the HIγS facility. A high-pressure gas target was used. We
identified 39 levels up to an excitation energy of 10.1 MeV.
Simulations of γ-ray cascades were performed to estimate
intensities of inelastic transitions and to correct the
intensities of the ground-state transitions for their
branching ratios. The photoabsorption cross section derived
in this way up to the neutron-separation energy is combined
with the photoabsorption cross section obtained from a
(γ,n) experiment at HIγS. The enhanced E1 strength found
in the range from 6 to 10 MeV is compared with the ones in
the N = 50 isotones 88Sr, 90Zr, and 92Mo and with
predictions of calculations within the quasiparticle-phonon
model. © 2013 American Physical Society.},
Doi = {10.1103/PhysRevC.87.024306},
Key = {fds313713}
}
@article{fds313743,
Author = {Ugalde, C and DiGiovine, B and Henderson, D and Holt, RJ and Rehm, KE and Sonnenschein, A and Robinson, A and Raut, R and Rusev, G and Tonchev,
AP},
Title = {First determination of an astrophysical cross section with a
bubble chamber: The N15(α,γ)F19
reaction},
Journal = {Physics Letters B},
Volume = {719},
Number = {1-3},
Pages = {74-77},
Year = {2013},
Month = {February},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2012.12.068},
Abstract = {We have devised a technique for measuring some of the most
important nuclear reactions in stars which we expect to
provide considerable improvement over previous experiments.
Adapting ideas from dark matter search experiments with
bubble chambers, we have found that a superheated liquid is
sensitive to recoils produced from γ rays
photodisintegrating the nuclei of the liquid. The main
advantage of the new target-detector system is a gain in
yield of six orders of magnitude over conventional gas
targets due to the higher mass density of liquids. Also, the
detector is practically insensitive to the γ-ray beam
itself, thus allowing it to detect only the products of the
nuclear reaction of interest. The first set of tests of a
superheated target with a narrow bandwidth γ-ray beam was
completed and the results demonstrate the feasibility of the
scheme. The new data are successfully described by an
R-matrix model using published resonance parameters. With
the increase in luminosity of the next generation γ-ray
beam facilities, the measurement of thermonuclear rates in
the stellar Gamow window would become possible. © 2013
Elsevier B.V.},
Doi = {10.1016/j.physletb.2012.12.068},
Key = {fds313743}
}
@article{fds313714,
Author = {Bhatia, C and Gooden, ME and Tornow, W and Tonchev,
AP},
Title = {Ground-state and isomeric-state cross sections for
181Ta(n,2n)180Ta between 8 and 15 MeV},
Journal = {Physical Review C},
Volume = {87},
Number = {3},
Year = {2013},
Month = {March},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.87.031601},
Abstract = {Using the activation technique, the cross section for the
reaction 181Ta(n,2n)180Tag was measured from 8 to 15 MeV in
small energy steps to resolve inconsistencies in the
existing database. The 93.4 keV γ ray from the decay of the
180Tag ground state was recorded with a high-purity
germanium (HPGe) detector. The monitor reactions
27Al(n,α)24Na and 197Au(n,2n)196Au were used for neutron
fluence determination. The ENDF VII.1 and TENDL 2011
evaluations are in considerable disagreement with the
present data, which in turn agree very well with the
majority of the existing data in the 14 MeV energy region. A
detailed analysis using the code talys was performed to
describe the present data and to predict the (n,2n) cross
section to the isomeric state of 180Ta. © 2013 American
Physical Society.},
Doi = {10.1103/PhysRevC.87.031601},
Key = {fds313714}
}
@article{fds313715,
Author = {Scheck, M and Ponomarev, VY and Aumann, T and Beller, J and Fritzsche,
M and Isaak, J and Kelley, JH and Kwan, E and Pietralla, N and Raut, R and Romig, C and Rusev, G and Savran, D and Sonnabend, K and Tonchev, AP and Tornow, W and Weller, HR and Zweidinger, M},
Title = {Decay pattern of the pygmy dipole resonance in
60Ni},
Journal = {Physical Review C},
Volume = {87},
Number = {5},
Year = {2013},
Month = {May},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.87.051304},
Abstract = {Spin-1 states in 60Ni were excited with the (γâ -, γ′)
reaction, exploiting the High Intensity γâ - -ray Source
at Triangle University Nuclear Laboratory. This facility is
capable of providing fully linearly polarized,
quasimonochromatic, Compton-backscattered photons in the
entrance channel of the reaction. The depopulation of
low-lying levels in an energy region far below the incident
quasimonochromatic photons allows us to obtain average
branching ratios of the excited spin-1 states. Levels within
the energy region associated with the PDR showed regular
behavior and ≈75% of their decays are direct ground-state
decays. The levels in the energy region above the PDR
exhibit a statistical decay behavior to a large number of
low-lying excited states and have only ≈50-60% branches to
the ground state. Within the framework of the quasiparticle
phonon model this feature can be explained with the number
of quasiparticles contributing to the wave functions of the
excited spin-1 states. Quasimonochromatic photon beams
provide a new method to test the microscopic nature of 1-
levels. © 2013 American Physical Society.},
Doi = {10.1103/PhysRevC.87.051304},
Key = {fds313715}
}
@article{fds313739,
Author = {Löher, B and Derya, V and Aumann, T and Beller, J and Cooper, N and Duchêne, M and Endres, J and Fiori, E and Isaak, J and Kelley, J and Knörzer, M and Pietralla, N and Romig, C and Savran, D and Scheck, M and Scheit, H and Silva, J and Tonchev, A and Tornow, W and Weller, H and Werner, V and Zilges, A},
Title = {The high-efficiency γ-ray spectroscopy setup γ
3 at HIγS},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {723},
Pages = {136-142},
Year = {2013},
Month = {June},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2013.04.087},
Abstract = {The existing Nuclear Resonance Fluorescence (NRF) setup at
the HIγS facility at the Triangle Universities Nuclear
Laboratory at Duke University has been extended in order to
perform γ-γ coincidence experiments. The new setup
combines large volume LaBr3:Ce detectors and high resolution
HPGe detectors in a very close geometry to offer high
efficiency, high energy resolution as well as high count
rate capabilities at the same time. The combination of a
highly efficient γ-ray spectroscopy setup with the
mono-energetic high-intensity photon beam of HIγS provides
a worldwide unique experimental facility to investigate the
γ-decay pattern of dipole excitations in atomic nuclei. The
performance of the new setup has been assessed by studying
the nucleus 32S at 8.125 MeV beam energy. The relative
γ-decay branching ratio from the 1+ level at 8125.4 keV to
the first excited 2+ state was determined to 15.7(3)%. ©
2013 Elsevier B.V.},
Doi = {10.1016/j.nima.2013.04.087},
Key = {fds313739}
}
@article{fds313716,
Author = {Elhami, E and Orce, JN and Scheck, M and Mukhopadhyay, S and Choudry,
SN and McEllistrem, MT and Yates, SW and Angell, C and Boswell, M and Fallin, B and Howell, CR and Hutcheson, A and Karwowski, HJ and Kelley,
JH and Parpottas, Y and Tonchev, AP and Tornow, W},
Title = {Erratum: Experimental study of the low-lying structure of
94Zr with the (n,n′γ) reaction (Physical
Review C - Nuclear Physics (2008) 78 (064303))},
Journal = {Physical Review C},
Volume = {88},
Number = {2},
Year = {2013},
Month = {August},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.88.029903},
Doi = {10.1103/PhysRevC.88.029903},
Key = {fds313716}
}
@article{fds313741,
Author = {Raut, R and Tonchev, AP and Rusev, G and Tornow, W and Iliadis, C and Lugaro, M and Buntain, J and Goriely, S and Kelley, JH and Schwengner,
R and Banu, A and Tsoneva, N},
Title = {Cross-section measurements of the 86Kr(γ,n) reaction to
probe the s-process branching at 85Kr.},
Journal = {Physical Review Letters},
Volume = {111},
Number = {11},
Pages = {112501},
Year = {2013},
Month = {September},
url = {http://www.ncbi.nlm.nih.gov/pubmed/24074078},
Abstract = {We have carried out photodisintegration cross-section
measurements on 86Kr using monoenergetic photon beams
ranging from the neutron separation energy, S(n) =
9.86 MeV, to 13 MeV. We combine our experimental
86Kr(γ,n)85Kr cross section with results from our recent
86Kr(γ,γ') measurement below the neutron separation energy
to obtain the complete nuclear dipole response of 86Kr. The
new experimental information is used to predict the neutron
capture cross section of 85Kr, an important branching point
nucleus on the abundance flow path during s-process
nucleosynthesis. Our new and more precise 85Kr(n,γ)86Kr
cross section allows us to produce more precise predictions
of the 86Kr abundance from s-process models. In particular,
we find that the models of the s process in asymptotic giant
branch stars of mass <1.5M⊙, where the 13C neutron source
burns convectively rather than radiatively, represent a
possible solution for the highest 86Kr:82Kr ratios observed
in meteoritic stardust SiC grains.},
Doi = {10.1103/physrevlett.111.112501},
Key = {fds313741}
}
@article{fds313717,
Author = {Scheck, M and Ponomarev, VY and Fritzsche, M and Joubert, J and Aumann,
T and Beller, J and Isaak, J and Kelley, JH and Kwan, E and Pietralla, N and Raut, R and Romig, C and Rusev, G and Savran, D and Schorrenberger, L and Sonnabend, K and Tonchev, AP and Tornow, W and Weller, HR and Zilges, A and Zweidinger, M},
Title = {Photoresponse of 60Ni below 10-MeV excitation energy:
Evolution of dipole resonances in fp-shell nuclei near
N=Z},
Journal = {Physical Review C},
Volume = {88},
Number = {4},
Year = {2013},
Month = {October},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.88.044304},
Abstract = {Background: Within the last decade, below the giant dipole
resonance the existence of a concentration of additional
electric dipole strength has been established. This
accumulation of low-lying E1 strength is commonly referred
to as pygmy dipole resonance (PDR). Purpose: The
photoresponse of 60Ni has been investigated experimentally
and theoretically to test the evolution of the PDR in a
nucleus with only a small neutron excess. Furthermore, the
isoscalar and isovector M1 resonances were investigated.
Method: Spin-1 states were excited by exploiting the
(γ,γ′) nuclear resonance fluorescence technique with
unpolarized continuous bremsstrahlung as well as with fully
linearly polarized, quasimonochromatic, Compton-backscattered
laser photons in the entrance channel of the reaction.
Results: Up to 10 MeV a detailed picture of J=1 levels was
obtained. For the preponderant number of the individual
levels spin and parity were firmly assigned. Furthermore,
branching ratios, transition widths, and reduced B(E1) or
B(M1) excitation probability were calculated from the
measured scattering cross sections. A comparison with
theoretical results obtained within the quasiparticle phonon
model allows an insight into the microscopic structure of
the observed states. Conclusions: Below 10 MeV the directly
observed E1 strength [ΣB(E1)↑=(153. 8±9.5) e2(fm)2]
exhausts 0.5% of the Thomas-Reiche-Kuhn sum rule. This value
increases to 0.8% of the sum rule [ΣB(E1)↑=(250.9±31.1)
e2(fm)2] when indirectly observed branches to lower-lying
levels are considered. Two accumulations of M1 excited
spin-1 states near 8 and 9 MeV excitation energy are
identified as isoscalar and isovector M1 resonances
dominated by proton and neutron f7/2→f5/2 spin-flip
excitations. The B(M1)↑ strength of these structures
accumulates to 3.94(27)μN2. © 2013 American Physical
Society.},
Doi = {10.1103/PhysRevC.88.044304},
Key = {fds313717}
}
@article{fds313718,
Author = {Romig, C and Beller, J and Glorius, J and Isaak, J and Kelley, JH and Kwan,
E and Pietralla, N and Ponomarev, VY and Sauerwein, A and Savran, D and Scheck, M and Schnorrenberger, L and Sonnabend, K and Tonchev, AP and Tornow, W and Weller, HR and Zilges, A and Zweidinger,
M},
Title = {Low-lying dipole strength of the open-shell nucleus
94Mo},
Journal = {Physical Review C},
Volume = {88},
Number = {4},
Year = {2013},
Month = {October},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.88.044331},
Abstract = {The low-lying dipole strength of the open-shell nucleus 94Mo
was studied via the nuclear resonance fluorescence technique
up to 8.7 MeV excitation energy at the bremsstrahlung
facility at the Superconducting Darmstadt Electron Linear
Accelerator (S-DALINAC), and with Compton backscattered
photons at the High Intensity γ-ray Source (HIγS)
facility. In total, 83 excited states were identified.
Exploiting polarized quasi-monoenergetic photons at HIγS,
parity quantum numbers were assigned to 41 states excited by
dipole transitions. The electric dipole-strength
distribution was determined up to 8.7 MeV and compared to
microscopic calculations within the quasiparticle phonon
model. Calculations and experimental data are in good
agreement for the fragmentation, as well as for the
integrated strength. The average decay pattern of the
excited states was investigated exploiting the HIγS
measurements at five energy settings. Mean branching ratios
to the ground state and first excited 21+ state were
extracted from the measurements with quasi-monoenergetic
photons and compared to γ-cascade simulations within the
statistical model. The experimentally deduced mean branching
ratios exhibit a resonance-like maximum at 6.4 MeV which
cannot be reproduced within the statistical model. This
indicates a nonstatistical structure in the energy range
between 5.5 and 7.5 MeV. © 2013 American Physical
Society.},
Doi = {10.1103/PhysRevC.88.044331},
Key = {fds313718}
}
@article{fds313720,
Author = {Massarczyk, R and Schwengner, R and Dönau, F and Frauendorf, S and Anders, M and Bemmerer, D and Beyer, R and Bhatia, C and Birgersson, E and Butterling, M and Elekes, Z and Ferrari, A and Gooden, ME and Hannaske,
R and Junghans, AR and Kempe, M and Kelley, JH and Kögler, T and Matic, A and Menzel, ML and Müller, S and Reinhardt, TP and Röder, M and Rusev, G and Schilling, KD and Schmidt, K and Schramm, G and Tonchev, AP and Tornow,
W and Wagner, A},
Title = {Nuclear deformation and neutron excess as competing effects
for pygmy dipole strength},
Volume = {112},
Number = {7},
Pages = {072501},
Year = {2013},
Month = {November},
ISSN = {0031-9007},
url = {http://dx.doi.org/10.1103/physrevlett.112.072501},
Abstract = {The electromagnetic dipole strength below the
neutron-separation energy has been studied for the xenon
isotopes with mass numbers A = 124, 128, 132, and 134 in
nuclear resonance fluorescence experiments using the ELBE
bremsstrahlung facility at Helmholtz-Zentrum
Dresden-Rossendorf and the HIgS facility at Triangle
Universities Nuclear Laboratory Durham. The systematic study
gained new information about the influence of the neutron
excess as well as of nuclear deformation on the strength in
the region of the pygmy dipole resonance. The results are
compared with those obtained for the chain of molybdenum
isotopes and with predictions of a random-phase
approximation in a deformed basis. It turned out that the
effect of nuclear deformation plays a minor role compared
with the one caused by neutron excess. A global
parametrization of the strength in terms of neutron and
proton numbers allowed us to derive a formula capable of
predicting the summed E1 strengths in the pygmy region for a
wide mass range of nuclides.},
Doi = {10.1103/physrevlett.112.072501},
Key = {fds313720}
}
@article{fds313738,
Author = {Goddard, PM and Cooper, N and Werner, V and Rusev, G and Stevenson, PD and Rios, A and Bernards, C and Chakraborty, A and Crider, BP and Glorius,
J and Ilieva, RS and Kelley, JH and Kwan, E and Peters, EE and Pietralla,
N and Raut, R and Romig, C and Savran, D and Schnorrenberger, L and Smith,
MK and Sonnabend, K and Tonchev, AP and Tornow, W and Yates,
SW},
Title = {Dipole response of 76Se above 4 MeV},
Journal = {Physical Review C},
Volume = {88},
Number = {6},
Pages = {064308},
Year = {2013},
Month = {December},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.88.064308},
Abstract = {The dipole response of 3476Se in the energy range from 4 to
9 MeV has been analyzed using a (γâ-, γ′) polarized
photon scattering technique, performed at the High Intensity
γ-Ray Source facility at Triangle Universities Nuclear
Laboratory, to complement previous work performed using
unpolarized photons. The results of this work offer both an
enhanced sensitivity scan of the dipole response and an
unambiguous determination of the parities of the observed
J=1 states. The dipole response is found to be dominated by
E1 excitations, and can reasonably be attributed to a pygmy
dipole resonance. Evidence is presented to suggest that a
significant amount of directly unobserved excitation
strength is present in the region, due to unobserved
branching transitions in the decays of resonantly excited
states. The dipole response of the region is underestimated
when considering only ground state decay branches. We
investigate the electric dipole response theoretically,
performing calculations in a three-dimensional (3D)
Cartesian-basis time-dependent Skyrme-Hartree-Fock
framework. Published by the American Physical Society under
the terms of the Creative Commons Attribution 3.0 License.
Further distribution of this work must maintain attribution
to the author(s) and the published article's title, journal
citation, and DOI.},
Doi = {10.1103/PhysRevC.88.064308},
Key = {fds313738}
}
@article{fds313719,
Author = {Isaak, J and Savran, D and Krtička, M and Ahmed, MW and Beller, J and Fiori, E and Glorius, J and Kelley, JH and Löher, B and Pietralla, N and Romig, C and Rusev, G and Scheck, M and Schnorrenberger, L and Silva, J and Sonnabend, K and Tonchev, AP and Tornow, W and Weller, HR and Zweidinger, M},
Title = {Constraining nuclear photon strength functions by the decay
properties of photo-excited states},
Journal = {Physics Letters B},
Volume = {727},
Number = {4-5},
Pages = {361-365},
Year = {2013},
Month = {December},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2013.10.040},
Abstract = {A new approach for constraining the low-energy part of the
electric dipole Photon Strength Function (E1-PSF) is
presented. Experiments at the Darmstadt High-Intensity
Photon Setup and the High Intensity γ→-Ray Source have
been performed to investigate the decay properties of 130Te
between 5.50 and 8.15 MeV excitation energy. In particular,
the average γ-ray branching ratio to the ground state and
the population intensity of low-lying excited states have
been studied. A comparison to the statistical model shows
that the latter is sensitive to the low-energy behavior of
the E1-PSF, while the average ground state branching ratio
cannot be described by the statistical model in the energy
range between 5.5 and 6.5 MeV. © 2013 Elsevier
B.V.},
Doi = {10.1016/j.physletb.2013.10.040},
Key = {fds313719}
}
@article{fds313729,
Author = {Krishichayan, and Bhike, M and Tornow, W},
Title = {Polarized photon scattering of $\^$$52$$ $ Cr: Determining
the parity of dipole states},
Journal = {Bulletin of the American Physical Society},
Volume = {59},
Number = {4},
Publisher = {American Physical Society},
Year = {2014},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.91.044328},
Doi = {10.1103/PhysRevC.91.044328},
Key = {fds313729}
}
@article{fds329813,
Author = {Grim, GP and Rundberg, R and Hayes, AC and Jungman, G and Boswell, M and Klein, A and Wilhelmy, J and Tonchev, A and Yeamans,
CB},
Title = {Measurement of reaction-in-ight neutrons using thulium
activation at the National Ignition Facility},
Journal = {Smart Structures and Materials 2005: Active Materials:
Behavior and Mechanics},
Volume = {9211},
Year = {2014},
Month = {January},
ISBN = {9781628412383},
url = {http://dx.doi.org/10.1117/12.2066249},
Abstract = {We report on the first observation of tertiary
reaction-in-ight (RIF) neutrons produced in compressed
deuterium and tritium filled capsules using the National
Ignition Facility at Lawrence Livermore National Laboratory,
Livermore, CA. RIF neutrons are produced by third-order, out
of equilibrium ("in-ight") fusion reactions, initiated by
primary fusion products. The rate of RIF reactions is
dependent upon the range of the elastically scattered fuel
ions and therefore a diagnostic of Coulomb physics within
the plasma. At plasma temperatures of∼5 keV, the presence
of neutrons with kinetic energies greater than 15 MeV is a
unique signature for RIF neutron production. The reaction
169Tm(n,3n) 167Tm has a threshold of 15.0 MeV, and a unique
decay scheme making it a suitable diagnostic for observing
RIF neutrons. RIF neutron production is quantified by the
ratio of 167Tm/168Tm observed in a 169Tm foil, where the
reaction 169Tm(n,2n) 168Tm samples the primary neutron
uence. Averaged over 4 implosions1-4 at the NIF, the
167Tm/168Tm ratio is measured to be 1.5± 0.3× 10-5,
leading to an average ratio of RIF to primary neutron ratio
of 1.0± 0.2× 10-4. These ratios are consistent with the
predictions for charged particle stopping in a quantum
degenerate plasma.},
Doi = {10.1117/12.2066249},
Key = {fds329813}
}
@article{fds313724,
Author = {Benouaret, N and Beller, J and Isaak, J and Kelley, JH and Pai, H and Pietralla, N and Ponomarev, VY and Raut, T and Romig, C and Rusev, G and Savran, D and Scheck, M and Schnorrenberger, L and Sonnabend, K and Tonchev, AP and Tornow, W and Weller, HR and Zweidinger,
M},
Title = {Photoexcitation of the stable tl isotopes below the neutron
separation energy},
Journal = {Acta Physica Polonica B},
Volume = {45},
Number = {2},
Pages = {193-198},
Year = {2014},
Month = {February},
ISSN = {0587-4254},
url = {http://dx.doi.org/10.5506/APhysPolB.45.193},
Abstract = {Although the systematics of the Pygmy Dipole Resonance was
established in several stable even-even nuclei, the
collectivity of this mode, explained in a macroscopic
picture as an oscillation of a neutron skin against an
isospin symmetric proton-neutron core, is still not well
understood. In order to guide the theoretical models, we
investigated the heavy odd mass, stable isotopes 203;205Tl
using unpolarized bremsstrahlung photon beams at the
S-DALINAC facility at TU Darmstadt. The NRF experiments were
complemented by measurements at the High Intensity -ray
Source (HIS) at the Triangle Universities Nuclear Laboratory
(TUNL) in Durham, NC, USA, with a fully linearly polarized
quasi-monoenergetic photon beam. Between 4 and 7 MeV, a
concentration of dipole strength is observed in the odd-mass
nuclide 205Tl. For the 203Tl isotope, two ground-state
transitions around 5 MeV could be resolved in the spectra.
In this report, the obtained results will be presented. The
results for the proton-odd nuclide 205Tl will be compared to
the ones for the neighbouring even-even nucleus
206Pb.},
Doi = {10.5506/APhysPolB.45.193},
Key = {fds313724}
}
@article{fds313723,
Author = {Sauerwein, A and Sonnabend, K and Fritzsche, M and Glorius, J and Kwan,
E and Pietralla, N and Romig, C and Rusev, G and Savran, D and Schnorrenberger, L and Tonchev, AP and Tornow, W and Weller,
HR},
Title = {Determination of the Ce 142 (,n) cross section using
quasi-monoenergetic Compton backscattered
rays},
Journal = {Physical Review C},
Volume = {89},
Number = {3},
Year = {2014},
Month = {March},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.89.035803},
Abstract = {Background: Knowing the energy dependence of the (,n) cross
section is mandatory to predict the abundances of heavy
elements using astrophysical models. The data can be applied
directly or used to constrain the cross section of the
inverse (n,) reaction. Purpose: The measurement of the
reaction Ce142(,n)141Ce just above the reaction threshold
amends the existing experimental database in that mass
region for p-process nucleosynthesis and helps to understand
the s-process branching at the isotope Ce141. Method: The
quasi-monoenergetic photon beam of the High Intensity -ray
Source (HIS), TUNL, USA, is used to irradiate naturally
composed Ce targets. The reaction yield is determined
afterwards with high-resolution -ray spectroscopy. Results:
The experimental data are in agreement with previous
measurements at higher energies. Since the cross-section
prediction of the Ce142(,n) reaction is exclusively
sensitive to the -ray strength function, the resulting
cross-section values were compared to Hauser-Feshbach
calculations using different -ray strength functions. A
microscopic description within the framework of the
Hartree-Fock-BCS model describes the experimental values
well within the measured energy range. Conclusions: The
measured data show that the predicted (,n) reaction rate is
correct within a factor of 2 even though the closed neutron
shell N=82 is approached. This agreement allows us to
constrain the (n,) cross section and to improve the
understanding of the s-process branching at Ce141. © 2014
American Physical Society.},
Doi = {10.1103/PhysRevC.89.035803},
Key = {fds313723}
}
@article{fds313740,
Author = {Derya, V and Savran, D and Endres, J and Harakeh, MN and Hergert, H and Kelley, JH and Papakonstantinou, P and Pietralla, N and Ponomarev,
VY and Roth, R and Rusev, G and Tonchev, AP and Tornow, W and Wörtche, HJ and Zilges, A},
Title = {Isospin properties of electric dipole excitations in
48Ca},
Journal = {Physics Letters B},
Volume = {730},
Pages = {288-292},
Year = {2014},
Month = {March},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2014.01.050},
Abstract = {Two different experimental approaches were combined to study
the electric dipole strength in the doubly-magic nucleus
48Ca below the neutron threshold. Real-photon scattering
experiments using bremsstrahlung up to 9.9 MeV and nearly
mono-energetic linearly polarized photons with energies
between 6.6 and 9.51 MeV provided strength distribution and
parities, and an (α, α 'γ) experiment at Eα = 136 MeV
gave cross sections for an isoscalar probe. The unexpected
difference observed in the dipole response is compared to
calculations using the first-order random-phase
approximation and points to an energy-dependent isospin
character. A strong isoscalar state at 7.6 MeV was
identified for the first time supporting a recent
theoretical prediction. © 2014 The Authors.},
Doi = {10.1016/j.physletb.2014.01.050},
Key = {fds313740}
}
@article{fds313721,
Author = {Isaak, J and Beller, J and Fiori, E and Krtička, M and Löher, B and Pietralla, N and Romig, C and Rusev, G and Savran, D and Scheck, M and Silva, J and Sonnabend, K and Tonchev, A and Tornow, W and Weller, H and Zweidinger, M},
Title = {Decay pattern of the pygmy dipole resonance in
130Te},
Journal = {Epj Web of Conferences},
Volume = {66},
Pages = {02055-02055},
Editor = {Lunardi, S and Bizzeti, P and Bucci, C and Chiari, M and Dainese, A and Di
Nezza, P and Menegazzo, R and Nannini, A and Signorini, C and Valiente-Dobon, J},
Year = {2014},
Month = {April},
url = {http://dx.doi.org/10.1051/epjconf/20146602055},
Abstract = {The electric dipole strength distribution in 130Te has been
investigated using the method of Nuclear Resonance
Fluorescence. The experiments were performed at the
Darmstadt High Intensity Photon Setup using bremsstrahlung
as photon source and at the High Intensity γ-Ray Source,
where quasi-monochromatic and polarized photon beams are
provided. Average decay properties of 130Te below the
neutron separation energy are determined. Comparing the
experimental data to the predictions of the statistical
model indicate, that nuclear structure effects play an
important role even at sufficiently high excitation
energies. Preliminary results will be presented. © Owned by
the authors, published by EDP Sciences, 2014.},
Doi = {10.1051/epjconf/20146602055},
Key = {fds313721}
}
@article{fds316572,
Author = {Gunsing, F and Fraval, K and Mathelie, M and Valenta, S and Bečvář,
F and Rusev, G and Tonchev, AP and Mitchell, G and Baramsai, B and Altstadt, S and Andrzejewski, J and Audouin, L and Barbagallo, M and Bécares, V and Belloni, F and Berthoumieux, E and Billowes, J and Boccone, V and Bosnar, D and Brugger, M and Calviani, M and Calviño, F and Cano-Ott, D and Carrapiço, C and Cerutti, F and Chiaveri, E and Chin,
M and Colonna, N and Cortés, G and Cortés-Giraldo, MA and Diakaki, M and Domingo-Pardo, C and Duran, I and Dressler, R and Eleftheriadis, C and Ferrari, A and Ganesan, S and García, AR and Giubrone, G and Gonçalves, IF and González-Romero, E and Griesmayer, E and Guerrero, C and Hernández-Prieto, A and Jenkins, DG and Jericha, E and Kadi, Y and Käppeler, F and Karadimos, D and Koehler, P and Kokkoris,
M and Krtička, M and Kroll, J and Lampoudis, C and Langer, C and Leal-Cidoncha, E and Lederer, C and Leeb, H and Leong, LS and Losito, R and Manousos, A and Marganiec, J and Martínez, T and Massimi, C and Mastinu, PF and Mastromarco, M and Mendoza, E and Mengoni, A and Milazzo, PM and Mingrone, F and Mirea, M and Mondalaers, W and Paradela,
C and Pavlik, A and Perkowski, J and Plompen, A and Praena, J and Quesada,
JM and Rauscher, T and Reifarth, R and Riego, A and Robles, MS and Rubbia,
C and Sabaté-Gilarte, M and Sarmento, R and Saxena, A and Schillebeeckx, P and Schmidt, S and Schumann, D and Tagliente, G and Tain, JL and Tarrío, D and Tassan-Got, L and Tsinganis, A and Vannini,
G and Variale, V and Vaz, P and Ventura, A and Vermeulen, MJ and Vlachoudis, V},
Title = {Spin measurements of n+87Sr for level density
studies},
Journal = {Nuclear Data Sheets},
Volume = {119},
Pages = {132-136},
Year = {2014},
Month = {May},
ISSN = {0090-3752},
url = {http://dx.doi.org/10.1016/j.nds.2014.08.037},
Abstract = {We have used the 4π BaF2 gamma-ray detector array at the
n_TOF neutron time-of-flight facility at CERN for an
experiment in order to determine the spins of resonances of
n+87Sr by measuring the gamma-ray spectra and multiplicity
distributions. The first results are presented here. We have
assigned the orbital momentum l to all evaluated resonances
on the basis of their neutron widths. Further we have
assigned the spin J to 16 s-wave resonances on based the
population of low-lying levels.},
Doi = {10.1016/j.nds.2014.08.037},
Key = {fds316572}
}
@article{fds313725,
Author = {Deboer, RJ and Best, A and Görres, J and Smith, K and Tan, W and Wiescher,
M and Raut, R and Rusev, G and Tonchev, AP and Tornow,
W},
Title = {Photoneutron strengths in 26Mg at energies of astrophysical
interest},
Journal = {Physical Review C},
Volume = {89},
Number = {5},
Year = {2014},
Month = {May},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.89.055802},
Abstract = {Background: The 22Ne(α,n)25Mg reaction is an important
source of neutrons for s-process nucleosynthesis. The
neutron production from the reaction is quite sensitive to
the low-energy cross section, which is dominated by narrow
resonances. The high level density of the 26Mg compound
nucleus above the α separation energy prevents simple
extrapolations from higher energy and the high Coulomb
barrier makes the direct measurements extremely difficult.
For this reason, indirect methods must be employed to study
the level properties of 26Mg. Purpose: The current
measurement utilizes the reaction 26Mg(γ,n)25Mg to probe
the level structure of the 26Mg compound nucleus from the
neutron-separation energy at 11.093 MeV up to Ex≈ 12 MeV.
Methods: The High-Intensity γ-ray Source of the Triangle
Universities Nuclear Laboratory was used to bombard a ∼16
g sample of enriched 26Mg oxide and the resulting decay
neutrons were detected with an array of nine liquid
scintillator detectors. Neutron time-of-flight peaks with
corresponding energies as low as ∼50 keV were detected. An
efficiency measurement of the detectors was made at the
University of Notre Dame's nuclear science laboratory to
energies as low as 45 keV. Results: Five resonances were
observed at Eγ = 11.150, 11.289, 11.329, 11.506, and 11.749
MeV and their strengths have been extracted. Conclusion:.
The resulting strengths at Eγ = 11.289, 11.329, 11.506, and
11.749 MeV are in good agreement with previous measurements.
The strength of the resonance at Eγ = 11.150 MeV is
somewhat lower than previously measured but is in reasonable
agreement when systematic uncertainties are considered. The
results are also consistent with those of 25Mg(n,γ)26Mg
studies where a comparison shows that many of the resonances
observed here are the result of multiple unresolved narrow
resonances. © 2014 American Physical Society.},
Doi = {10.1103/PhysRevC.89.055802},
Key = {fds313725}
}
@article{fds313726,
Author = {Bhatia, C and Fallin, B and Gooden, ME and Howell, CR and Kelley, JH and Tornow, W and Arnold, CW and Bond, EM and Bredeweg, TA and Fowler, MM and Moody, WA and Rundberg, RS and Rusev, G and Vieira, DJ and Wilhelmy, JB and Becker, JA and Macri, R and Ryan, C and Sheets, SA and Stoyer, MA and Tonchev, AP},
Title = {Dual-fission chamber and neutron beam characterization for
fission product yield measurements using monoenergetic
neutrons},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {757},
Pages = {7-19},
Year = {2014},
Month = {September},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2014.03.022},
Abstract = {A program has been initiated to measure the energy
dependence of selected high-yield fission products used in
the analysis of nuclear test data. We present out initial
work of neutron activation using a dual-fission chamber with
quasi-monoenergetic neutrons and gamma-counting method.
Quasi-monoenergetic neutrons of energies from 0.5 to 15 MeV
using the TUNL 10 MV FM tandem to provide high-precision and
self-consistent measurements of fission product yields
(FPY). The final FPY results will be coupled with
theoretical analysis to provide a more fundamental
understanding of the fission process. To accomplish this
goal, we have developed and tested a set of dual-fission
ionization chambers to provide an accurate determination of
the number of fissions occurring in a thick target located
in the middle plane of the chamber assembly. Details of the
fission chamber and its performance are presented along with
neutron beam production and characterization. Also presented
are studies on the background issues associated with
room-return and off-energy neutron production. We show that
the off-energy neutron contribution can be significant, but
correctable, while room-return neutron background levels
contribute less than <1% to the fission signal. © 2014
Elsevier B.V.},
Doi = {10.1016/j.nima.2014.03.022},
Key = {fds313726}
}
@article{fds313727,
Author = {Massarczyk, R and Rusev, G and Schwengner, R and Dönau, F and Bhatia,
C and Gooden, ME and Kelley, JH and Tonchev, AP and Tornow,
W},
Title = {Magnetic dipole strength in Xe 128 and Xe 134 in the
spin-flip resonance region},
Journal = {Physical Review C},
Volume = {90},
Number = {5},
Year = {2014},
Month = {November},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.90.054310},
Abstract = {The magnetic dipole strength in the energy region of the
spin-flip resonance is investigated in Xe128 and Xe134 using
quasimonoenergetic and linearly polarized γ-ray beams at
the High-Intensity γ-Ray Source facility in Durham, North
Carolina, USA. Absorption cross sections were deduced for
the magnetic and electric and dipole strength distributions
separately for various intervals of excitation energy,
including the strength of states in the unresolved
quasicontinuum. The magnetic dipole strength distributions
show structures resembling a resonance in the spin-flip
region around an excitation energy of 8 MeV. The electric
dipole strength distributions obtained from the present
experiments are in agreement with the ones deduced from an
earlier experiment using broad-band bremsstrahlung instead
of a quasimonoenergetic beam. The experimental magnetic and
electric dipole strength distributions are compared with
phenomenological approximations and with predictions of a
quasiparticle random phase approximation in a deformed
basis.},
Doi = {10.1103/PhysRevC.90.054310},
Key = {fds313727}
}
@article{fds313728,
Author = {Beller, J and Stumpf, C and Scheck, M and Pietralla, N and Deleanu, D and Filipescu, DM and Glodariu, T and Haxton, W and Idini, A and Kelley, JH and Kwan, E and Martinez-Pinedo, G and Raut, R and Romig, C and Roth, R and Rusev, G and Savran, D and Tonchev, AP and Tornow, W and Wagner, J and Weller, HR and Zamfir, NV and Zweidinger, M},
Title = {Separation of the 1+/1- parity doublet
in 20Ne},
Journal = {Physics Letters B},
Volume = {741},
Pages = {128-133},
Year = {2015},
Month = {February},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2014.12.018},
Abstract = {The (J, T)=(1, 1) parity doublet in 20Ne at 11.26 MeV is a
good candidate to study parity violation in nuclei. However,
its energy splitting is known with insufficient accuracy for
quantitative estimates of parity violating effects. To
improve on this unsatisfactory situation, nuclear resonance
fluorescence experiments using linearly and circularly
polarized γ-ray beams were used to determine the energy
difference of the parity doublet δE=E(1-)-E(1+)=-3.2(±0.7)stat(-1.2+0.6)sys
keV and the ratio of their integrated cross sections
Is,0(+)/Is,0(-)=29(±3)stat(-7+14)sys. Shell-model
calculations predict a parity-violating matrix element
having a value in the range 0.46-0.83 eV for the parity
doublet. The small energy difference of the parity doublet
makes 20Ne an excellent candidate to study parity violation
in nuclear excitations.},
Doi = {10.1016/j.physletb.2014.12.018},
Key = {fds313728}
}
@article{fds313742,
Author = {DiGiovine, B and Henderson, D and Holt, RJ and Raut, R and Rehm, KE and Robinson, A and Sonnenschein, A and Rusev, G and Tonchev, AP and Ugalde,
C},
Title = {Bubble chambers for experiments in nuclear
astrophysics},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {781},
Pages = {96-104},
Year = {2015},
Month = {May},
ISSN = {0168-9002},
url = {http://dx.doi.org/10.1016/j.nima.2015.01.060},
Abstract = {A bubble chamber has been developed to be used as an active
target system for low energy nuclear astrophysics
experiments. Adopting ideas from dark matter detection with
superheated liquids, a detector system compatible with
γ-ray beams has been developed. This detector alleviates
some of the limitations encountered in standard measurements
of the minute cross-sections of interest to stellar
environments. While the astrophysically relevant nuclear
reaction processes at hydrostatic burning temperatures are
dominated by radiative captures, in this experimental scheme
we measure the time-reversed processes. Such
photodisintegrations allow us to compute the radiative
capture cross-sections when transitions to excited states of
the reaction products are negligible. Due to the
transformation of phase space, the photodisintegration
cross-sections are up to two orders of magnitude higher. The
main advantage of the new target-detector system is a
density several orders of magnitude higher than conventional
gas targets. Also, the detector is virtually insensitive to
the γ-ray beam itself, thus allowing us to detect only the
products of the nuclear reaction of interest. The
development and the operation as well as the advantages and
disadvantages of the bubble chamber are discussed.},
Doi = {10.1016/j.nima.2015.01.060},
Key = {fds313742}
}
@article{fds313734,
Author = {Benouaret, N and Beller, J and Isaak, J and Kelley, JH and Pai, H and Pietralla, N and Ponomarev, VY and Raut, R and Romig, C and Rusev, G and Savran, D and Scheck, M and Schnorrenberger, L and Sonnabend, K and Tonchev, AP and Tornow, W and Weller, HR and Zweidinger,
M},
Title = {QPM analysis of 205TI nuclear excitations below
the giant dipole resonance},
Journal = {Epj Web of Conferences},
Volume = {93},
Pages = {01044-01044},
Editor = {Schwengner, R and Zuber, K},
Year = {2015},
Month = {May},
ISBN = {9782759817948},
url = {http://dx.doi.org/10.1051/epjconf/20159301044},
Abstract = {We analysed our experimental recent findings of the dipole
response of the odd-mass stable nucleus 205Tl within the
quasi-particle phonon model. Using the phonon basis
constructed for the neighbouring 204Hg and wave function
configurations for 205Tl consisting of a mixture of
quasiparticle ⊗ N-phonon configurations (N=0,1,2), only
one group of fragmented dipole excited states has been
reproduced at 5.5 MeV in comparison to the experimental
distribution which shows a second group at about 5 MeV. The
computed dipole transition strengths are mainly of E1
character which could be associated to the pygmy dipole
resonance. Owned by the authors, published by EDP Sciences,
2015.},
Doi = {10.1051/epjconf/20159301044},
Key = {fds313734}
}
@article{fds313735,
Author = {Werner, V and Cooper, N and Goddard, PM and Humby, P and Ilieva, RS and Rusev, G and Beller, J and Bernards, C and Crider, BP and Isaak, J and Kelley, JH and Kwan, E and Löher, B and Peters, EE and Pietralla, N and Romig, C and Savran, D and Scheck, M and Tonchev, AP and Tornow, W and Yates, SW and Zweidinger, M},
Title = {Dipole strength distributions from HIGS Experiments},
Journal = {Epj Web of Conferences},
Volume = {93},
Pages = {01031-01031},
Editor = {Schwengner, R and Zuber, K},
Year = {2015},
Month = {May},
ISBN = {9782759817948},
url = {http://dx.doi.org/10.1051/epjconf/20159301031},
Abstract = {A series of photon scattering experiments has been performed
on the double-beta decay partners 76Ge and 76Se, in order to
investigate their dipole response up to the neutron
separation threshold. Gamma-ray beams from bremsstrahlung at
the S-DALINAC and from Compton-backscattering at HIGS have
been used to measure absolute cross sections and parities of
dipole excited states, respectively. The HIGS data allows
for indirect measurement of averaged branching ratios, which
leads to significant corrections in the observed excitation
cross sections. Results are compared to statistical
calculations, to test photon strength functions and the
Axel-Brink hypothesis. Owned by the authors, published by
EDP Sciences, 2015.},
Doi = {10.1051/epjconf/20159301031},
Key = {fds313735}
}
@article{fds313736,
Author = {Isaak, J and Löher, B and Savran, D and Aumann, T and Beller, J and Cooper, N and Derya, V and Duchêne, M and Endres, J and Fiori, E and Kelley, JH and Knörzer, M and Pietralla, N and Ponomarev, VY and Romig,
C and Scheck, M and Scheit, H and Silva, J and Tonchev, AP and Tornow, W and Weller, HR and Werner, V and Zilges, A and Zweidinger,
M},
Title = {Decay pattern of the pygmy dipole resonance in
140Ce},
Journal = {Epj Web of Conferences},
Volume = {93},
Pages = {01048-01048},
Editor = {Schwengner, R and Zuber, K},
Year = {2015},
Month = {May},
ISBN = {9782759817948},
url = {http://dx.doi.org/10.1051/epjconf/20159301048},
Abstract = {The decay behavior of low-lying dipole states in 140Ce was
investigated exploiting the γ3-setup at the HIγS facility
using quasi-monochromatic photon beams. Branching ratios of
individual excited states as well as average branching
ratios to low-lying states have been extracted using γ -γ
coincidence measurements. The comparison of the average
branching ratios to QPM calculations shows a remarkable
agreement between experiment and theory in the energy range
from 5.0 to 8.5 MeV. Owned by the authors, published by EDP
Sciences, 2015.},
Doi = {10.1051/epjconf/20159301048},
Key = {fds313736}
}
@article{fds313737,
Author = {Tonchev, A and Bhatia, C and Kelley, J and Raut, R and Rusev, G and Tornow,
W and Tsoneva, N},
Title = {Nuclear structure studies with gamma-ray
beams},
Journal = {Epj Web of Conferences},
Volume = {93},
Pages = {01030-01030},
Editor = {Schwengner, R and Zuber, K},
Year = {2015},
Month = {May},
ISBN = {9782759817948},
url = {http://dx.doi.org/10.1051/epjconf/20159301030},
Abstract = {In stable and weakly bound neutron-rich nuclei, a
resonance-like concentration of dipole states has been
observed for excitation energies below the
neutron-separation energy. This clustering of strong dipole
states has been named the Pygmy Dipole Resonance (PDR) in
contrast to the Giant Dipole Resonance (GDR) that dominates
the E1 response. Understanding the PDR is presently of great
interest in nuclear structure and nuclear astrophysics.
High-sensitivity studies of E1 and M1 transitions in
closed-shell nuclei using monoenergetic and 100%
linearly-polarized photon beams are presented. Owned by the
authors, published by EDP Sciences, 2015.},
Doi = {10.1051/epjconf/20159301030},
Key = {fds313737}
}
@article{fds313730,
Author = {Bhatia, C and Fallin, BF and Gooden, ME and Howell, CR and Kelley, JH and Tornow, W and Arnold, CW and Bond, E and Bredeweg, TA and Fowler, MM and Moody, W and Rundberg, RS and Rusev, GY and Vieira, DJ and Wilhelmy, JB and Becker, JA and Macri, R and Ryan, C and Sheets, SA and Stoyer, MA and Tonchev, AP},
Title = {Exploratory study of fission product yields of
neutron-induced fission of U 235, U 238, and Pu 239 at 8.9
MeV EXPLORATORY STUDY of FISSION PRODUCT YIELDS ... C.
BHATIA et al.},
Journal = {Physical Review C},
Volume = {91},
Number = {6},
Year = {2015},
Month = {June},
ISSN = {0556-2813},
url = {http://dx.doi.org/10.1103/PhysRevC.91.064604},
Abstract = {Using dual-fission chambers each loaded with a thick
(200-400-mg/cm2) actinide target of 235,238U or Pu239 and
two thin (∼10-100-μg/cm2) reference foils of the same
actinide, the cumulative yields of fission products ranging
from Sr92 to Nd147 have been measured at En=8.9MeV. The
H2(d,n)He3 reaction provided the quasimonoenergetic neutron
beam. The experimental setup and methods used to determine
the fission product yield (FPY) are described, and results
for typically eight high-yield fission products are
presented. Our FPYs for U235(n,f), U238(n,f), and Pu239(n,f)
at 8.9 MeV are compared with the existing data below 8 MeV
from Glendenin et al. [Phys. Rev. C 24, 2600
(1981)10.1103/PhysRevC.24.2600], Nagy et al. [Phys. Rev. C
17, 163 (1978)10.1103/PhysRevC.17.163], Gindler et al.
[Phys. Rev. C 27, 2058 (1983)10.1103/PhysRevC.27.2058], and
those of Mac Innes et al. [Nucl. Data Sheets 112, 3135
(2011)10.1016/j.nds.2011.11.009] and Laurec et al. [Nucl.
Data Sheets 111, 2965 (2010)10.1016/j.nds.2010.11.004] at
14.5 and 14.7 MeV, respectively. This comparison indicates a
negative slope for the energy dependence of most fission
product yields obtained from U235 and Pu239, whereas for
U238 the slope issue remains unsettled.},
Doi = {10.1103/PhysRevC.91.064604},
Key = {fds313730}
}
@article{fds329812,
Author = {Hayes, AC and Jungman, G and Schulz, AE and Boswell, M and Fowler, MM and Grim, G and Klein, A and Rundberg, RS and Wilhelmy, JB and Wilson, D and Cerjan, C and Schneider, D and Sepke, SM and Tonchev, A and Yeamans,
C},
Title = {Reaction-in-flight neutrons as a test of stopping power in
degenerate plasmas},
Journal = {Physics of Plasmas},
Volume = {22},
Number = {8},
Pages = {082703-082703},
Year = {2015},
Month = {August},
url = {http://dx.doi.org/10.1063/1.4928104},
Abstract = {We present the first measurements of reaction-in-flight
(RIF) neutrons in an inertial confinement fusion system. The
experiments were carried out at the National Ignition
Facility, using both Low Foot and High Foot drives and
cryogenic plastic capsules. In both cases, the high-energy
RIF (En> 15 MeV) component of the neutron spectrum was found
to be about 10<sup>-4</sup> of the total. The majority of
the RIF neutrons were produced in the dense cold fuel
surrounding the burning hotspot of the capsule, and the data
are consistent with a compressed cold fuel that is
moderately to strongly coupled (Γ∼ 0.6) and electron
degenerate (θFermi/θe∼ 4). The production of RIF
neutrons is controlled by the stopping power in the plasma.
Thus, the current RIF measurements provide a unique test of
stopping power models in an experimentally unexplored plasma
regime. We find that the measured RIF data strongly
constrain stopping models in warm dense plasma conditions,
and some models are ruled out by our analysis of these
experiments.},
Doi = {10.1063/1.4928104},
Key = {fds329812}
}
@article{fds313731,
Author = {Gooden, ME and Arnold, CW and Becker, JA and Bhatia, C and Bhike, M and Bond, EM and Bredeweg, TA and Fallin, B and Fowler, MM and Howell, CR and others},
Title = {Energy Dependence of Fission Product Yields from 235 U, 238
U and 239 Pu for Incident Neutron Energies Between 0.5 and
14.8 MeV},
Journal = {Nuclear Data Sheets},
Volume = {131},
Pages = {319-356},
Publisher = {Academic Press},
Year = {2016},
ISSN = {0090-3752},
url = {http://dx.doi.org/10.1016/j.nds.2015.12.006},
Doi = {10.1016/j.nds.2015.12.006},
Key = {fds313731}
}
@article{fds313732,
Author = {Champine, B and Gooden, ME and Norman, EB and Scielzo, ND and Stoyer,
MA and Thomas, KJ and Tonchev, AP and Tornow, W and Wang, BS and others},
Title = {Measurement of the Tm 169 (n, 3 n) Tm 167 cross section and
the associated branching ratios in the decay of Tm
167},
Journal = {Physical Review C},
Volume = {93},
Number = {1},
Pages = {014611-014611},
Publisher = {APS},
Year = {2016},
ISSN = {2469-9985},
url = {http://dx.doi.org/10.1103/PhysRevC.93.014611},
Abstract = {The cross section for the Tm169(n,3n)Tm167 reaction was
measured from 17 to 22 MeV using quasimonoenergetic neutrons
produced by the H2(d,n)He3 reaction. This energy range was
studied to resolve the discrepancy between previous (n,3n)
cross-section measurements. In addition, the absolute γ-ray
branching ratios following the electron-capture decay of
Tm167 were measured. These results provide more reliable
nuclear data for an important diagnostic that is used at the
National Ignition Facility to estimate the yield of
reaction-in-flight neutrons produced via the
inertial-confinement-fusion plasma in deuterium-tritium
capsules.},
Doi = {10.1103/PhysRevC.93.014611},
Key = {fds313732}
}
@article{fds314803,
Author = {Isaak, J and Beller, J and Fiori, E and Glorius, J and Krtička, M and Löher, B and Pietralla, N and Romig, C and Rusev, G and Savran, D and Scheck, M and Silva, J and Sonnabend, K and Tonchev, AP and Tornow, W and Weller, HR and Zweidinger, M},
Title = {Investigation of the Photon Strength Function in
130 Te},
Journal = {Journal of Physics: Conference Series},
Volume = {665},
Number = {1},
Pages = {012039-012039},
Year = {2016},
Month = {January},
ISSN = {1742-6588},
url = {http://dx.doi.org/10.1088/1742-6596/665/1/012039},
Abstract = {The dipole strength distribution of 130Te was investigated
with the method of Nuclear Resonance Fluorescence using
continuous-energy bremsstrahlung at the Darmstadt High
Intensity Photon Setup and quasi-monoenergetic photons at
the High Intensity γ-Ray Source. The average decay
properties were determined between 5.50 and 8.15 MeV and
compared to simulations within the statistical
model.},
Doi = {10.1088/1742-6596/665/1/012039},
Key = {fds314803}
}
@article{fds313748,
Author = {Stave, S and Prinke, A and Greenwood, L and Haas, D and Burke, JT and Ressler, JJ and Tonchev, AP and Younes, W},
Title = {Reducing uncertainties for short lived cumulative fission
product yields},
Journal = {Journal of Radioanalytical and Nuclear Chemistry},
Volume = {307},
Number = {3},
Pages = {2221-2225},
Year = {2016},
Month = {March},
ISSN = {0236-5731},
url = {http://dx.doi.org/10.1007/s10967-015-4436-3},
Abstract = {Uncertainties associated with short lived (half-lives less
than 1 day) fission product yields listed in databases such
as the National Nuclear Data Center’s ENDF/B-VII are large
enough for certain isotopes to provide an opportunity for
new precision measurements to offer significant uncertainty
reductions. A series of experiments has begun where small
samples of 235U are irradiated with a pulsed, fission
neutron spectrum at the Nevada National Security Site and
placed between two broad-energy germanium detectors. The
amount of various isotopes present immediately following the
irradiation can be determined given the total counts and the
calibrated properties of the detector system. The
uncertainty on the fission yields for multiple isotopes has
been reduced by nearly an order of magnitude.},
Doi = {10.1007/s10967-015-4436-3},
Key = {fds313748}
}
@article{fds313733,
Author = {Löher, B and Savran, D and Aumann, T and Beller, J and Bhike, M and Cooper, N and Derya, V and Duchêne, M and Endres, J and Hennig, A and Humby, P and Isaak, J and Kelley, JH and Knörzer, M and Pietralla, N and Ponomarev, VY and Romig, C and Scheck, M and Scheit, H and Silva, J and Tonchev, AP and Tornow, W and Wamers, F and Weller, H and Werner, V and Zilges, A},
Title = {The decay pattern of the Pygmy Dipole Resonance of
140Ce},
Journal = {Physics Letters B},
Volume = {756},
Pages = {72-76},
Year = {2016},
Month = {May},
ISSN = {0370-2693},
url = {http://dx.doi.org/10.1016/j.physletb.2016.02.042},
Abstract = {The decay properties of the Pygmy Dipole Resonance (PDR)
have been investigated in the semi-magic N=82 nucleus 140Ce
using a novel combination of nuclear resonance fluorescence
and γ-γ coincidence techniques. Branching ratios for
transitions to low-lying excited states are determined in a
direct and model-independent way both for individual excited
states and for excitation energy intervals. Comparison of
the experimental results to microscopic calculations in the
quasi-particle phonon model exhibits an excellent agreement,
supporting the observation that the Pygmy Dipole Resonance
couples to the ground state as well as to low-lying excited
states. A 10% mixing of the PDR and the [21+×PDR] is
extracted.},
Doi = {10.1016/j.physletb.2016.02.042},
Key = {fds313733}
}
@article{fds318472,
Author = {Hayes, AC and Cerjan, CJ and Jungman, G and Fowler, MM and Gooden, ME and Grim, GP and Henry, E and Rundberg, RS and Sepke, SM and Schneider, DHG and Singleton, RL and Tonchev, AP and Wilhelmy, JB and Yeamans,
CB},
Title = {Reaction-in-Flight neutrons as a test of stopping power in
degenerate plasmas},
Journal = {Journal of Physics: Conference Series},
Volume = {717},
Number = {1},
Pages = {012022-012022},
Year = {2016},
Month = {May},
url = {http://dx.doi.org/10.1088/1742-6596/717/1/012022},
Abstract = {Cryogenically cooled inertial confinement fusion capsule
designs are suitable for studies of reaction-in-flight (RIF)
neutrons. RIF neutrons occur when energetically up-scattered
ions undergo DT reactions with a thermal ion in the plasma,
producing neutrons in the energy range 9-30 MeV. The
knock-on ions lose energy as they traverse the plasma, which
directly affects the spectrum of the produced RIF neutrons.
Here we present measurements from the National Ignition
Facility (NIF) of RIF neutrons produced in cryogenic
capsules, with energies above 15 MeV. We show that the
measured RIFs probe stopping under previously unexplored
degenerate plasma conditions and constrain stopping models
in warm dense plasma conditions.},
Doi = {10.1088/1742-6596/717/1/012022},
Key = {fds318472}
}
@article{fds318473,
Author = {Escher, JE and Tonchev, AP and Burke, JT and Bedrossian, P and Casperson, RJ and Cooper, N and Hughes, RO and Humby, P and Ilieva, RS and Ota, S and Pietralla, N and Scielzo, ND and Werner,
V},
Title = {Compound-nuclear reactions with unstable nuclei:
Constraining theory through innovative experimental
approaches},
Journal = {Epj Web of Conferences},
Volume = {122},
Pages = {12001-12001},
Editor = {Kawano, T and Chiba, S and Paris, M and Talou, P},
Year = {2016},
Month = {June},
url = {http://dx.doi.org/10.1051/epjconf/201612212001},
Abstract = {Cross sections for compound-nuclear reactions involving
unstable targets are important for many applications, but
can often not be measured directly. Several indirect methods
have recently been proposed to determine neutron capture
cross sections for unstable isotopes. We consider three
approaches that aim at constraining statistical calculations
of capture cross sections with data obtained from the decay
of the compound nucleus relevant to the desired reaction.
Each method produces this compound nucleus in a different
manner (via a light-ion reaction, a photon-induced reaction,
or β-decay) and requires additional ingredients to yield
the sought-after cross section. We give a brief outline of
the approaches and employ preliminary results from recent
measurements to illustrate the methods. We discuss the main
advantages and challenges of each approach.},
Doi = {10.1051/epjconf/201612212001},
Key = {fds318473}
}
@article{fds318471,
Author = {Benouaret, N and Beller, J and Pai, H and Pietralla, N and Ponomarev,
VY and Romig, C and Schnorrenberger, L and Zweidinger, M and Scheck, M and Isaak, J and Savran, D and Sonnabend, K and Raut, R and Rusev, G and Tonchev, AP and Tornow, W and Weller, HR and Kelley,
JH},
Title = {Dipole response of the odd-proton nucleus 205Tl
up to the neutron-separation energy},
Journal = {Journal of Physics G: Nuclear and Particle
Physics},
Volume = {43},
Number = {11},
Pages = {115101-115101},
Year = {2016},
Month = {October},
url = {http://dx.doi.org/10.1088/0954-3899/43/11/115101},
Abstract = {The low-lying electromagnetic dipole strength of the
odd-proton nuclide 205Tl has been investigated up to the
neutron separation energy exploiting the method of nuclear
resonance fluorescence. In total, 61 levels of 205Tl have
been identified. The measured strength distribution of 205Tl
is discussed and compared to those of even-even and even-odd
mass nuclei in the same mass region as well as to
calculations that have been performed within the
quasi-particle phonon model.},
Doi = {10.1088/0954-3899/43/11/115101},
Key = {fds318471}
}
@article{fds329294,
Author = {Gooden, M and Arnold, C and Bhike, M and Bredeweg, T and Fowler, M and Krishichayan, and Tonchev, A and Tornow, W and Stoyer, M and Vieira, D and others},
Title = {Energy dependence of fission product yields from 235U, 238U,
and 239Pu with monoenergetic neutrons between thermal and
14.8 MeV},
Journal = {Epj Web of Conferences},
Volume = {146},
Pages = {04024-04024},
Editor = {Plompen, A and Hambsch, F-J and Schillebeeckx, P and Mondelaers, W and Heyse, J and Kopecky, S and Siegler, P and Oberstedt,
S},
Year = {2017},
ISBN = {9782759890200},
url = {http://dx.doi.org/10.1051/epjconf/201714604024},
Abstract = {Under a joint collaboration between TUNL-LANL-LLNL, a set of
absolute fission product yield measurements has been
performed. The energy dependence of a number of cumulative
fission product yields (FPY) have been measured using
quasi-monoenergetic neutron beams for three actinide
targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The
FPYs were measured by a combination of fission counting
using specially designed dual-fission chambers and γ-ray
counting. Each dual-fission chamber is a back-to-back
ionization chamber encasing an activation target in the
center with thin deposits of the same target isotope in each
chamber. This method allows for the direct measurement of
the total number of fissions in the activation target with
no reference to the fission cross-section, thus reducing
uncertainties. γ-ray counting of the activation target was
performed on well-shielded HPGe detectors over a period of
two months post irradiation to properly identify fission
products. Reported are absolute cumulative fission product
yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6,
4.6, 5.5, 7.5, 8.9 and 14.8 MeV. Preliminary results from
thermal irradiations at the MIT research reactor will also
be presented and compared to present data and evaluations.
This work was performed under the auspices of the U.S.
Department of Energy by Los Alamos National Security, LLC
under contract DE-AC52-06NA25396, Lawrence Livermore
National Laboratory under contract DE-AC52-07NA27344 and by
DGBRe University and Triangle Universities Nuclear
Laboratory through NNSA Stewardship Science Academic
Alliance grant No. DE-FG52-09NA29465, DE-FG52-09NA29448 and
Office of Nuclear Physics Grant No. DE-FG02-97ER41033.},
Doi = {10.1051/epjconf/201714604024},
Key = {fds329294}
}
@article{fds329295,
Author = {Krishichayan, and Bhike, M and Tonchev, AP and Tornow,
W},
Title = {Fission product yield measurements using monoenergetic
photon beams},
Journal = {Epj Web of Conferences},
Volume = {146},
Pages = {04018-04018},
Editor = {Plompen, A and Hambsch, F-J and Schillebeeckx, P and Mondelaers, W and Heyse, J and Kopecky, S and Siegler, P and Oberstedt,
S},
Year = {2017},
ISBN = {9782759890200},
url = {http://dx.doi.org/10.1051/epjconf/201714604018},
Abstract = {Measurements of fission products yields (FPYs) are an
important source of information on the fission process.
During the past couple of years, a TUNL-LANL-LLNL
collaboration has provided data on the FPYs from quasi
monoenergetic neutron-induced fission on 235U, 238U, and
239Pu and has revealed an unexpected energy dependence of
both asymmetric fission fragments at energies below 4 MeV.
This peculiar FPY energy dependence was more pronounced in
neutron-induced fission of 239Pu. In an effort to understand
and compare the effect of the incoming probe on the FPY
distribution, we have carried out monoenergetic
photon-induced fission experiments on the same 235U, 238U,
and 239Pu targets. Monoenergetic photon beams of Eγ = 13.0
MeV were provided by the HIγS facility, the world's most
intense γ-ray source. In order to determine the total
number of fission events, a dual-fission chamber was used
during the irradiation. These irradiated samples were
counted at the TUNL's low-background γ-ray counting
facility using high efficient HPGe detectors over a period
of 10 weeks. Here we report on our first ever photofission
product yield measurements obtained with monoenegetic photon
beams. These results are compared with neutron-induced FPY
data.},
Doi = {10.1051/epjconf/201714604018},
Key = {fds329295}
}
@article{fds324424,
Author = {Krishichayan, and Bhike, M and Finch, SW and Howell, CR and Tonchev,
AP and Tornow, W},
Title = {Photofission cross-section ratio measurement of 235 U/238 U
using monoenergetic photons in the energy range of
9.0–16.6 MeV},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {854},
Pages = {40-44},
Publisher = {North Holland},
Year = {2017},
url = {http://dx.doi.org/10.1016/j.nima.2017.02.043},
Abstract = {© 2017 Elsevier B.V.Photofission cross-section ratios of
235U and 238U have been measured using monoenergetic photon
beams at the HIγS facility of TUNL. These measurements have
been performed in small energy steps between 9.0 and 16.6
MeV using a dual-fission ionization chamber. Measured
cross-section ratios are compared with the previous
experimental data as well as with the recent evaluated
nuclear data library ENDF.},
Doi = {10.1016/j.nima.2017.02.043},
Key = {fds324424}
}
@article{fds325703,
Author = {Bhike, M and Tornow, W and Krishichayan, and Tonchev,
AP},
Title = {Exploratory study of fission product yield determination
from photofission of Pu 239 at 11 MeV with monoenergetic
photons},
Journal = {Physical Review C},
Volume = {95},
Number = {2},
Pages = {024608-024608},
Publisher = {American Physical Society},
Year = {2017},
url = {http://dx.doi.org/10.1103/PhysRevC.95.024608},
Doi = {10.1103/PhysRevC.95.024608},
Key = {fds325703}
}
@article{fds329292,
Author = {Tonchev, AP and Escher, JE and Scielzo, N and Bedrossian, P and Ilieva,
RS and Humby, P and Cooper, N and Goddard, PM and Werner, V and Tornow, W and Rusev, G and Kelley, JH and Pietralla, N and Scheck, M and Savran, D and Löher, B and Yates, SW and Crider, BP and Peters, EE and Tsoneva, N and Goriely, S},
Title = {Capture cross sections on unstable nuclei},
Journal = {Epj Web of Conferences},
Volume = {146},
Pages = {01013-01013},
Editor = {Plompen, A and Hambsch, F-J and Schillebeeckx, P and Mondelaers, W and Heyse, J and Kopecky, S and Siegler, P and Oberstedt,
S},
Year = {2017},
Month = {September},
ISBN = {9782759890200},
url = {http://dx.doi.org/10.1051/epjconf/201714601013},
Abstract = {Accurate neutron-capture cross sections on unstable nuclei
near the line of beta stability are crucial for
understanding the s-process nucleosynthesis. However,
neutron-capture cross sections for short-lived radionuclides
are difficult to measure due to the fact that the
measurements require both highly radioactive samples and
intense neutron sources. Essential ingredients for
describing the γ decays following neutron capture are the
γ-ray strength function and level densities. We will
compare different indirect approaches for obtaining the most
relevant observables that can constrain Hauser-Feshbach
statistical-model calculations of capture cross sections.
Specifically, we will consider photon scattering using
monoenergetic and 100% linearly polarized photon beams.
Challenges that exist on the path to obtaining
neutron-capture cross sections for reactions on isotopes
near and far from stability will be discussed.},
Doi = {10.1051/epjconf/201714601013},
Key = {fds329292}
}
@article{fds329293,
Author = {Schwengner, R and Massarczyk, R and Bemmerer, D and Beyer, R and Junghans, AR and Kögler, T and Rusev, G and Tonchev, AP and Tornow, W and Wagner, A},
Title = {E1 and M1 strength functions at low energy},
Journal = {Epj Web of Conferences},
Volume = {146},
Pages = {05001-05001},
Editor = {Plompen, A and Hambsch, F-J and Schillebeeckx, P and Mondelaers, W and Heyse, J and Kopecky, S and Siegler, P and Oberstedt,
S},
Year = {2017},
Month = {September},
ISBN = {9782759890200},
url = {http://dx.doi.org/10.1051/epjconf/201714605001},
Abstract = {We report photon-scattering experiments using bremsstrahlung
at the γELBE facility of Helmholtz-Zentrum
Dresden-Rossendorf and using quasi-monoenergetic, polarized
γ beams at the HIγS facility of the Triangle Universities
Nuclear Laboratory in Durham. To deduce the photoabsorption
cross sections at high excitation energy and high level
density, unresolved strength in the quasicontinuum of
nuclear states has been taken into account. In the analysis
of the spectra measured by using bremsstrahlung at γELBE,
we perform simulations of statistical γ-ray cascades using
the code γDEX to estimate intensities of inelastic
transitions to low-lying excited states. Simulated average
branching ratios are compared with model-independent
branching ratios obtained from spectra measured by using
monoenergetic γ beams at HIγS. E1 strength in the energy
region of the pygmy dipole resonance is discussed in nuclei
around mass 90 and in xenon isotopes. M1 strength in the
region of the spin-flip resonance is also considered for
xenon isotopes. The dipole strength function of 74Ge deduced
from γELBE experiments is compared with the one obtained
from experiments at the Oslo Cyclotron Laboratory. The
low-energy upbend seen in the Oslo data is interpreted as M1
strength on the basis of shell-model calculations.},
Doi = {10.1051/epjconf/201714605001},
Key = {fds329293}
}
@article{fds329974,
Author = {Krishichayan, and Bhike, M and Tornow, W and Tonchev, AP and Kawano,
T},
Title = {Accurate U238 ( n, 2n ) U237 reaction cross-section
measurements from 6.5 to 14.8 MeV},
Journal = {Physical Review C},
Volume = {96},
Number = {4},
Publisher = {American Physical Society (APS)},
Year = {2017},
Month = {October},
url = {http://dx.doi.org/10.1103/physrevc.96.044623},
Abstract = {The cross section for the U238(n,2n)U237 reaction has been
measured in the incident neutron energy range from 6.5 to
14.8 MeV in small energy steps using an activation
technique. Monoenergetic neutron beams were produced via the
H2(d,n)He3 and H3(d,n)He4 reactions. U238 targets were
activated along with Au and Al monitor foils to determine
the incident neutron flux. The activity of the reaction
products was measured in TUNL's low-background counting
facility using high-resolution γ-ray spectroscopy. The
results are compared with previous measurements and latest
data evaluations. Statistical-model calculations, based on
the Hauser-Feshbach formalism, have been carried out using
the CoH3 code and are compared with the experimental
results. The present self-consistent and high-quality data
are important for stockpile stewardship and nuclear forensic
purposes as well as for the design and operation of fast
reactors.},
Doi = {10.1103/physrevc.96.044623},
Key = {fds329974}
}
@article{fds328275,
Author = {Tonchev, AP and Tsoneva, N and Bhatia, C and Arnold, CW and Goriely, S and Hammond, SL and Kelley, JH and Kwan, E and Lenske, H and Piekarewicz, J and Raut, R and Rusev, G and Shizuma, T and Tornow, W},
Title = {Pygmy and core polarization dipole modes in
206Pb: Connecting nuclear structure to stellar
nucleosynthesis},
Journal = {Physics Letters B},
Volume = {773},
Pages = {20-25},
Year = {2017},
Month = {October},
url = {http://dx.doi.org/10.1016/j.physletb.2017.07.062},
Abstract = {A high-resolution study of the electromagnetic response of
206Pb below the neutron separation energy is performed using
a γ→,γ′) experiment at the HIγ→S facility. Nuclear
resonance fluorescence with 100% linearly polarized photon
beams is used to measure spins, parities, branching ratios,
and decay widths of excited states in 206Pb from 4.9 to 8.1
MeV. The extracted ΣB(E1)↑ and ΣB(M1)↑ values for the
total electric and magnetic dipole strength below the
neutron separation energy are 0.9±0.2 e2fm2 and
8.3±2.0μN2, respectively. These measurements are found to
be in very good agreement with the predictions from an
energy-density functional (EDF) plus quasiparticle phonon
model (QPM). Such a detailed theoretical analysis allows to
separate the pygmy dipole resonance from both the tail of
the giant dipole resonance and multi-phonon excitations.
Combined with earlier photonuclear experiments above the
neutron separation energy, one extracts a value for the
electric dipole polarizability of 206Pb of αD=122±10
mb/MeV. When compared to predictions from both the EDF+QPM
and accurately calibrated relativistic EDFs, one deduces a
range for the neutron-skin thickness of Rskin206=0.12–0.19
fm and a corresponding range for the slope of the symmetry
energy of L=48–60 MeV. This newly obtained information is
also used to estimate the Maxwellian-averaged radiative
cross section Pb205(n,γ)Pb206 at 30 keV to be σ=130±25
mb. The astrophysical impact of this measurement—on both
the s-process in stellar nucleosynthesis and on the equation
of state of neutron-rich matter—is discussed.},
Doi = {10.1016/j.physletb.2017.07.062},
Key = {fds328275}
}
@article{fds335617,
Author = {Tonchev, AP and Tsoneva, N and Goriely, S and Bhatia, C and Arnold, CW and Hammond, SL and Kelley, JH and Kwan, E and Lenske, H and Piekarewicz, J and Raut, R and Rusev, G and Shizuma, T and Tornow, W},
Title = {Astrophysical relevance of the low-energy dipole strength of
206Pb},
Journal = {Epj Web of Conferences},
Volume = {178},
Pages = {04003-04003},
Editor = {Sun, Y},
Year = {2018},
Month = {May},
url = {http://dx.doi.org/10.1051/epjconf/201817804003},
Abstract = {The dipole strength of 206Pb was studied below the neutron
separation energy using photon scattering experiments at the
HIGS facility. Utilizing the technique of nuclear resonance
fluorescence with 100% linearly-polarized photon beams, the
spins, parities, branching ratios and decay widths of
excited states in 206Pb from 4.9 - 8.1 MeV have been
measured. The new experimental information is used to
reliably predict the neutron capture cross section of 205Pb,
an important branch point nucleus along the s-process path
of nucleosynthesis.},
Doi = {10.1051/epjconf/201817804003},
Key = {fds335617}
}
@article{fds333320,
Author = {Matthews, EF and Goldblum, BL and Bernstein, LA and Quiter, BJ and Brown, JA and Younes, W and Burke, JT and Padgett, SW and Ressler, JJ and Tonchev, AP},
Title = {FIER: Software for analytical modeling of delayed gamma-ray
spectra},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {891},
Pages = {111-117},
Year = {2018},
Month = {May},
url = {http://dx.doi.org/10.1016/j.nima.2018.02.072},
Abstract = {A new software package, the Fission Induced Electromagnetic
Response (FIER) code, has been developed to analytically
predict delayed γ-ray spectra following fission. FIER uses
evaluated nuclear data and solutions to the Bateman
equations to calculate the time-dependent populations of
fission products and their decay daughters resulting from
irradiation of a fissionable isotope. These populations are
then used in the calculation of γ-ray emission rates to
obtain the corresponding delayed γ-ray spectra. FIER output
was compared to experimental data obtained by irradiation of
a 235U sample in the Godiva critical assembly. This
investigation illuminated discrepancies in the input nuclear
data libraries, showcasing the usefulness of FIER as a tool
to address nuclear data deficiencies through comparison with
experimental data. FIER provides traceability between γ-ray
emissions and their contributing nuclear species, decay
chains, and parent fission fragments, yielding a new
capability for the nuclear science community.},
Doi = {10.1016/j.nima.2018.02.072},
Key = {fds333320}
}
@article{fds335616,
Author = {Krishichayan, and Finch, SW and Howell, CR and Tonchev, AP and Tornow,
W},
Title = {Monoenergetic photon-induced fission cross-section ratio
measurements for U235 , U238 , and Pu239 from 9.0 to 17.0
MeV},
Journal = {Physical Review C},
Volume = {98},
Number = {1},
Publisher = {American Physical Society (APS)},
Year = {2018},
Month = {July},
url = {http://dx.doi.org/10.1103/physrevc.98.014608},
Doi = {10.1103/physrevc.98.014608},
Key = {fds335616}
}
@article{fds346924,
Author = {Tornow, W and Bhike, M and Finch, SW and Krishichayan, and Tonchev,
AP},
Title = {Measurement of the in 115 (γ,γ′) in 115m inelastic
scattering cross section in the 1.8 to 3.7 MeV energy range
with monoenergetic photon beams MEASUREMENT of the in 115
(γ, ... W. TORNOW et al.},
Journal = {Physical Review C},
Volume = {98},
Number = {6},
Year = {2018},
Month = {December},
url = {http://dx.doi.org/10.1103/PhysRevC.98.064305},
Abstract = {For the first time the excitation cross section of In115 to
its first excited state at 336.24 keV has been measured with
monoenergetic photon beams at 15 energies between 1.8 and
3.7 MeV. The measurements were performed at the
High-Intensity Gamma-ray Source (HIγS) facility with
natural In targets and incident photon fluxes ranging from
0.7×107γ/(cm2s) to 3.2×107γ/(cm2s). The inelastic
scattering cross section was obtained from the yield of the
336.24 keV deexcitation γ rays. The cross-section values
varied between <0.05 and 28.7 μb at 1.8 and 3.7 MeV,
respectively. Compared to standard photon inelastic
scattering cross-section data in this energy range of
medium-mass nuclei, these extremely small values are not
completely unexpected, given the nature of the low-lying
nuclear levels of In115. Model calculations, however,
overestimate the measured cross-section data by
approximately one order of magnitude. Using different
choices for the E1 γ-ray strength function, the data can be
well described. The data are important for improving our
knowledge of the level scheme of In115, especially spin and
parity assignments of already known states.},
Doi = {10.1103/PhysRevC.98.064305},
Key = {fds346924}
}
@article{fds346923,
Author = {Pierson, BD and Prinke, AM and Greenwood, LR and Stave, SC and Wittman,
RS and Burch, JG and Burke, JT and Padgett, SW and Ressler, JJ and Slavik,
G and Tamashiro, A and Tonchev, A and Younes, W},
Title = {Improved Cumulative Fission Yield Measurements with Fission
Spectrum Neutrons on 235U},
Journal = {Nuclear Data Sheets},
Volume = {155},
Pages = {86-97},
Year = {2019},
Month = {January},
url = {http://dx.doi.org/10.1016/j.nds.2019.01.005},
Abstract = {Two isotopically-characterized targets of high-purity
(99.84±0.03%) 235U-oxide and a neutron dosimetry package
were exposed to a pulsed neutron irradiation using the
Godiva critical assembly at the National Criticality
Experiments Research Center. Following irradiation, the
fissioned targets were counted with a broad-energy germanium
detector. Estimates of the total fissions for each target
were made using measurements of well-known fission products.
The total fission values were then used to measure the
fission yields of 21 fission products with half-lives
between 636 and 119,700 seconds. Mean values of seventeen of
the measured fission products fell within the 95% confidence
level of the Evaluated Nuclear Data Files VII.1/b
(ENDF/B-VII.1) using the larger of the two uncertainties:
84gBr, 89Rb, 91Sr, 93Y, 97Zr, 101Mo, 105Ru, 128Sn, 129Sb,
130gSb, 131Sb, 131mTe, 133I, 135I, 141Ba, 142Ba, and 142La.
Seven isotopes were measured to better precision than is
listed in the ENDF/B-VII.1 database: 89Rb, 93Y, 128Sn,
129Sb, 130gSb, 131mTe, and 133I. Four of the measured
isotopes were found to be statistically different from the
ENDF/B-VII.1 database: 94Y, 134Te, 134I, and 138Xe. Two of
the isotopic analyses conducted in this paper fit the parent
and daughter data simultaneously. The parent-daughter pairs
measured in this way were the 134Te/I and 142Ba/La pairs.
The fission yield results obtained in this way are unique,
especially for 134I, because the parent and daughter
half-lives are so close. Given the limited number of direct
measurements of the 134Te/I pair from fast neutron induced
fission and the seemingly high estimate for 134Te from
previous work, it is likely that the value in this paper is
more accurate; however, additional measurements of this pair
are needed to validate this assertion.},
Doi = {10.1016/j.nds.2019.01.005},
Key = {fds346923}
}
@article{fds346922,
Author = {Shusterman, JA and Scielzo, ND and Thomas, KJ and Norman, EB and Lapi,
SE and Loveless, CS and Peters, NJ and Robertson, JD and Shaughnessy,
DA and Tonchev, AP},
Title = {The surprisingly large neutron capture cross-section of
88Zr.},
Journal = {Nature},
Volume = {565},
Number = {7739},
Pages = {328-330},
Year = {2019},
Month = {January},
url = {http://dx.doi.org/10.1038/s41586-018-0838-z},
Abstract = {The probability that a nucleus will absorb a neutron-the
neutron capture cross-section-is important to many areas of
nuclear science, including stellar nucleosynthesis, reactor
performance, nuclear medicine and defence applications.
Although neutron capture cross-sections have been measured
for most stable nuclei, fewer results exist for radioactive
isotopes, and statistical-model predictions typically have
large uncertainties<sup>1</sup>. There are almost no nuclear
data for neutron-induced reactions of the radioactive
nucleus <sup>88</sup>Zr, despite its importance as a
diagnostic for nuclear security. Here, by exposing
<sup>88</sup>Zr to the intense neutron flux of a nuclear
reactor, we determine that <sup>88</sup>Zr has a thermal
neutron capture cross-section of 861,000 ± 69,000 barns
(1σ uncertainty), which is five orders of magnitude larger
than the theoretically predicted value of 10
barns<sup>2</sup>. This is the second-largest thermal
neutron capture cross-section ever measured and no other
cross-section of comparable size has been discovered in the
past 70 years. The only other nuclei known to have values
greater than 10<sup>5</sup> barns<sup>3-6</sup> are
<sup>135</sup>Xe (2.6 × 10<sup>6</sup> barns), a
fission product that was first discovered as a poison in
early reactors<sup>7,8</sup>, and <sup>157</sup>Gd
(2.5 × 10<sup>5</sup> barns), which is used as a
detector material<sup>9,10</sup>, a burnable reactor
poison<sup>11</sup> and a potential medical neutron capture
therapy agent<sup>12</sup>. In the case of <sup>88</sup>Zr
neutron capture, both the target and the product
(<sup>89</sup>Zr) nuclei are radioactive and emit intense
γ-rays upon decay, allowing sensitive detection of
miniscule quantities of these radionuclides. This result
suggests that as additional measurements with radioactive
isotopes become feasible with the operation of new
nuclear-science facilities, further surprises may be
uncovered, with far-reaching implications for our
understanding of neutron capture reactions.},
Doi = {10.1038/s41586-018-0838-z},
Key = {fds346922}
}
@article{fds346921,
Author = {Krishichayan, and Bhike, M and Howell, CR and Tonchev, AP and Tornow,
W},
Title = {Fission product yield measurements using monoenergetic
photon beams},
Journal = {Physical Review C},
Volume = {100},
Number = {1},
Year = {2019},
Month = {July},
url = {http://dx.doi.org/10.1103/PhysRevC.100.014608},
Abstract = {Background: High-accuracy and self-consistent fission
product yield (FPY) data are needed to advance
microscopic/macroscopic descriptions of the nuclear fission
process, to improve the predictive power of phenomenological
models, and for applications in nuclear energy, nuclear
forensics, and homeland security. Purpose: In a
collaboration between the Triangle Universities Nuclear
Laboratory (TUNL), Los Alamos National Laboratory (LANL),
and Lawrence Livermore National Laboratory (LLNL), the
dependence of a number of cumulative FPYs on the incoming
neutron energy has been measured and unexpected energy
dependencies of certain fission products have been reported
[M. E. Gooden, Nucl. Data Sheets 131, 319
(2016)NDTSBA0090-375210.1016/j.nds.2015.12.006]. To
investigate whether this observation is unique to
neutron-induced fission, a program has been initiated to
measure FPYs in photon-induced fission. Method: The
photon-induced FPYs were measured by a combination of
fission counting using a specially designed dual-fission
chamber and γ-ray counting. The measurements were carried
out with a monoenergetic photon beam at the HIγS facility.
Gamma-ray counting of the activated targets was performed
with well-shielded high-purity germanium (HPGe) detectors
over a period of two months after irradiation to properly
identify the decay history of fission products. Results: We
report on our photofission product yield measurements on
U235, U238, and Pu239 using a monoenergetic photon beam of
Eγ=13MeV. More than 40 fission products were uniquely
identified, and their yield values were computed. The use of
the fission chamber with post-activation measurements has
provided absolute fission product yield data with minimal
uncertainties. Conclusion: The photon-induced cumulative
fission product yields of U235, U238, and Pu239 are compared
with previous photon- and neutron-induced fission
measurements. In the near future data will be obtained at
lower and higher photon energies.},
Doi = {10.1103/PhysRevC.100.014608},
Key = {fds346921}
}
@article{fds355821,
Author = {Finch, SW and Bhike, M and Howell, CR and Krishichayan, and Tornow, W and Tonchev, AP and Wilhelmy, JB},
Title = {Measurements of Short-Lived Isomers from Photofission as a
Method of Active Interrogation for Special Nuclear
Materials},
Journal = {Physical Review Applied},
Volume = {15},
Number = {3},
Year = {2021},
Month = {March},
url = {http://dx.doi.org/10.1103/PhysRevApplied.15.034037},
Abstract = {Isomeric fission products, such as 134mTe (T1/2=164 ns) and
136mXe (T1/2=2.95μs), are proposed as a signature of
special nuclear materials in active interrogation
applications. To test this conjecture, monoenergetic 9, 11,
and 13 MeV photons from the HIγS facility are used to
induce fission of 235U, 238U, and 239Pu targets. The
de-excitation γ rays of the isomers are measured using
time-gated spectroscopy with high-purity germanium
detectors. The 134mTe and 136mXe isomers are detected and
identified by the energy and decay half-life of their
characteristic γ-ray transitions. The ratio of yields for
these two signature γ rays, corresponding to
134mTe/(136mXe+136I), is found to be strongly correlated
with the identity of the fissioning nuclei. These results
show that fission-product isomers may be used in active
interrogation to detect and identify special nuclear
materials, even providing information on the isotopic
enrichment. The feasibility of an active interrogation
scenario using a bremsstrahlung beam is discussed.},
Doi = {10.1103/PhysRevApplied.15.034037},
Key = {fds355821}
}
@article{fds355820,
Author = {Kolos, K and Hennessy, AM and Scielzo, ND and Iacob, VE and Hardy, JC and Stoyer, MA and Tonchev, AP and Ong, WJ and Burkey, MT and Champine, B and Clark, JA and Copp, P and Gallant, A and Norman, EB and Orford, R and Park,
HI and Rohrer, J and Santiago-Gonzalez, D and Savard, G and Shaka, AJ and Wang, BS and Zhu, S},
Title = {New approach to precisely measure γ-ray intensities for
long-lived fission products, with results for the decay of
95Zr},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {1000},
Year = {2021},
Month = {June},
url = {http://dx.doi.org/10.1016/j.nima.2021.165240},
Abstract = {For many fission products, the γ rays emitted following β
decay provide an easily-detectable signature that can be
used to identify their quantities and distributions in a
sample. As a result, γ-ray spectroscopy is often exploited
to study fission-product yields, provided sufficiently
accurate information on the γ-ray intensity is available.
However, in many cases, the uncertainties in the existing
nuclear data are large enough that they compromise the
precision achievable for modern experiments and
applications. To address this need, we have developed a new
experimental method that is well suited to precisely measure
absolute γ-ray intensities in the β decay of long-lived
fission products. The approach involves the production of a
radiopure sample by implantation of a mass-separated ion
beam from the CAlifornium Rare Isotope Breeder Upgrade
(CARIBU) facility on a thin carbon foil. The emitted
β-decay radiation is detected with a 4π gas proportional
counter and a meticulously efficiency-calibrated high-purity
germanium (HPGe) detector. As a first measurement to
demonstrate the approach, we studied the absolute γ-ray
intensities of the strongest transitions following the β
decay of 95Zr and its decay-daughter 95Nb, and determined
them to fractional precisions of better than 1–2%. In
addition, with a larger sample of activity produced through
neutron irradiation of an isotopically-enriched Zr foil, we
performed a high-precision measurement of the relative
γ-ray intensities following the decay of 95Zr with just the
HPGe detector. The sample-production method at CARIBU and
the coincidence detection approach demonstrated here can be
applied to study fission products with half-lives longer
than a day, which includes isotopes important not only for
nuclear-energy and national-security applications, but also
for medical-isotope research and environmental
monitoring.},
Doi = {10.1016/j.nima.2021.165240},
Key = {fds355820}
}
@article{fds358759,
Author = {Mashtakov, KR and Ponomarev, VY and Scheck, M and Finch, SW and Isaak,
J and Zweidinger, M and Agar, O and Bathia, C and Beck, T and Beller, J and Bowry, M and Chapman, R and Chishti, MMR and Friman-Gayer, U and Gaffney, LP and Garrett, PE and Gregor, ET and Keatings, JM and Köster,
U and Löher, B and MacLean, AD and O'Donnell, D and Pai, H and Pietralla,
N and Rainovski, G and Ramdhane, M and Romig, C and Rusev, G and Savran, D and Simpson, GS and Sinclair, J and Sonnabend, K and Spagnoletti, P and Tonchev, AP and Tornow, W},
Title = {Structure of high-lying levels populated in the
96Y →96Zr β decay},
Journal = {Physics Letters B},
Volume = {820},
Year = {2021},
Month = {September},
url = {http://dx.doi.org/10.1016/j.physletb.2021.136569},
Abstract = {The nature of the high-lying final levels of the 96Ygs β
decay, one of the three most important contributors to the
high-energy reactor antineutrino spectrum, has been
investigated in high-resolution γ-ray spectroscopy
following the β decay as well as in a campaign of inelastic
photon scattering experiments. The comprehensive approach
establishes 1− levels associated with the Pygmy Dipole
Resonance as high-lying final levels in the β decay.
Branching ratios extracted from β decay complement photon
scattering and allow the absolute E1 excitation strength to
be determined for levels populated in both reactions. The
combined data represents a comprehensive approach to the
wavefunction of the 1− levels below the Qβ value, which
are investigated in the Quasiparticle Phonon Model. The
calculations reveal that the components populated in β
decay contribute only with small amplitudes to the complex
wavefunction of these 1− levels. A comparison of the β
decay results to data from total absorption γ-ray
spectroscopy demonstrates a good agreement between both
measurements.},
Doi = {10.1016/j.physletb.2021.136569},
Key = {fds358759}
}
@article{fds361370,
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 = {fds361370}
}
@article{fds361248,
Author = {Finch, SW and Gooden, ME and Hagmann, C and Howell, CR and Krishichayan, and Ramirez, APD and Silano, JA and Stoyer, MA and Tonchev, AP and Tornow,
W and Wilhelmy, JB},
Title = {Development of a rapid-transit system for precision nuclear
physics measurements},
Journal = {Nuclear Instruments and Methods in Physics Research Section
A: Accelerators, Spectrometers, Detectors and Associated
Equipment},
Volume = {1025},
Year = {2022},
Month = {February},
url = {http://dx.doi.org/10.1016/j.nima.2021.166127},
Abstract = {A Rapid Belt-driven Irradiated Target Transfer System, named
RABITTS, was developed for use at the Triangle Universities
Nuclear Laboratory. This system allows for cyclic activation
with neutron or photon beams, and measurement of reaction
products using γ-ray spectroscopy. Both a 1 meter and 10
meter transfer system have been developed with transit times
as low as 0.4 and 1.0 s, respectively. The systems are
deployed at the tandem accelerator laboratory for use with
monoenergetic neutron beams, and at the High-Intensity
γ-ray Source facility for activation using photon beams. A
detailed characterization of the systems’ performance and
sensitivity is presented. In order to produce the highest
accuracy cross-section data, a model for calculating
corrections to cyclic activation with variable beam flux is
developed and presented. We have commissioned these systems
by measuring 197mAu, where we report a measured half-life of
7.73±0.05 s and a 197Au(n,n′)197mAu isomer production
cross of 628±28 mb at neutron energy En=2.0MeV. In
addition, we measured 90mZr, where we report a measured
half-life of 799.7±8.0ms and a 90Zr(n,n′)90mZr isomer
production cross of 180±12 mb at En=4.6MeV. These measured
half-lives are in excellent agreement with the evaluated
values and the cross-section measurements are performed at
previously unmeasured incident neutron energies.},
Doi = {10.1016/j.nima.2021.166127},
Key = {fds361248}
}
%% Papers Submitted
@article{fds167265,
Author = {E. Kwan and G. Rusev and A. S. Adekola and S. Hammond and C.R. Howell and H. J. Karwowski and J.H. Kelley and R. Raut and A. P. Tonchev and W.
Tornow},
Title = {Discrete deexcitations in 235U below 3 MeV from nuclear
resonance fluorescence},
Journal = {Phys. Rev. C},
Year = {2010},
Key = {fds167265}
}
%% Other
@misc{fds167419,
Author = {Mark B. Chadwick and Robert C. Little and Toshihiko Kawano and Patrick Talou and David Viera and Marian Jandel and Todd A. Bredeweg and Morgan C. White and Anton P. Tonchev and John A.
Becker},
Title = {Actinide ENDF/BVII cross section evaluations and validation
testing},
Journal = {International Conference on Reactor Physics, “Nuclear
Power: A Sustainable Resource” Casino-Kursaal Conference
Center, Interlaken, Switzerland},
Year = {2008},
Key = {fds167419}
}