H. R. Weller, Duke University and Triangle Universities Nuclear Laboratory (TUNL)
Recent results from the HIGS facility
Physics Division Colloquium - 25 Jan. 2002

The High Intensity Gamma-ray Source (HIGS) utilizes intra-cavity back-scattering of the UV-FEL light in order to produce a g-flux enhancement of approximately 103 over existing sources. The Duke storage ring was designed to operate at energies from 200 MeV to 1.1 GeV. At present, gamma-ray beams with energies ranging from 2-to-50 MeV are available with intensities of 105-108 g/s and 100% linear polarization. An upgrade is presently underway which will allow for the production of g rays up to an energy of about 225 MeV having intensities in excess of 109 /sec/MeV. The primary component of the upgrade is a 1.2 GeV booster-injector which will permit the operation of the ring at full-flux and full energy. In addition, an upgrade of the present OK-4 FEL to a helical undulator system (OK-5) is underway. This new system has many advantages over the present one, including making switchable linear and circularly polarized beams available, an increase in power and a decrease in mirror-damaging radiation. The present schedule calls for having OK-5 operating by the end of 2002. The full system, including the booster injector, is expected to be ready for use by mid-2005.

Two recent commissioning experiments will be described:

1. d(\gamma,n)p Preliminary results have been obtained in the case of d(\gamma,n)p in the threshold region. This is an important region, relevant to Big-Bang nucleo-synthesis. The HIGS 100% linearly polarized beam allows for a separation of the M1 and the E1 parts of the cross section. Recent results from the U.Va- U.Sask- TUNL-DFELL GDH Collaboration will be described.

2. Nuclear Resonance Fluorescence: the HIGS beams have the intensity and energy resolution to allow for a new level of precision NRF spectroscopy. Preliminary results on 138Ba and 88Sr indicate the power of this facility. (PRL 88, 012502, 2002). These results will be discussed. Present plans for additional research projects, which take advantage of the unique features of HIGS, will also be presented.

ANL Physics Division Colloquium Schedule