Abstract:
The High Intensity Gamma-ray Source (HIGS) is a joint project between the Triangle Universities Nuclear Laboratory (TUNL) and the Duke Free Electron Laser Laboratory
(DFELL). This facility utilizes intra-cavity back-scattering of the FEL light in order
to produce intense gamma-ray beams. An upgrade which allows for the production of
- gamma-rays up to energies of about 150 MeV having total intensities in excess of 108/sec is essentially complete. The primary component of the upgrade is a 1.2 GeV booster injector which makes it possible to replace lost electrons at full energy. In addition,
an upgrade of the present linear undulator to a helical system has made it possible
to produce nearly 100% linear and circularly polarized beams. The full system was
commissioned in the early part of 2007. A nuclear physics research program using
beams at energies below 50 MeV commenced in the fall of 2007. The proposed experimental
program includes low-energy studies of nuclear reactions of importance
in nuclear astrophysics as well as studies of nuclear structure using the technique of
nuclear resonance fluorescence (NRF). Few-body nuclear physics problems will also
be addressed by studying photodisintegration of d, 3He and 4He. Future doublepolarization
experiments include a study of the Gerasimov-Drell-Hearn Sum Rule for the deuteron and 3He, and an extensive Compton scattering program designed
to probe the internal structure of the nucleon. A major focus of these studies will
be the measurement of the electric and magnetic polarizabilities as well as the spinpolarizabilities
of the proton and the neutron. Studies at pion-threshold designed to
test the predictions of Chiral Perturbation Theory and to observe Isospin-symmetry
breaking effects are also being planned. This review will describe the principles of
operation of the upgraded facility, followed by a description of the performance
which has been achieved to date, and a projection of the performance anticipated
in the near future. Following this, we will review several of the research areas of nuclear physics which are accessible using this facility, and describe both the results
to date and proposed experiments being developed for the future.