THE TUNL-FELL INVERSE COMPTON GAMMA-RAY SOURCE AS A NUCLEAR-PHYSICS FACILITY

A new technique for producing an intense beam of polarized gamma-rays is presented. This High-Intensity Gamma-ray Source (HIGS) will utilize the facilities of the new Duke Free Electron Laser Laboratory. This s ystem includes the LINAC injector, the 1.3 GeV electron storage ring, and the OK-4 undulator. It will be shown that it is possible to tune t he electron beam in a manner which allows the FEL photons to backscatt er from an electron bunch, all within the ring. This leads to an inten se beam of almost 100% linearly polarized gamma-rays whose energy can be readily tuned from about 5 to greater than 200 MeV. Furthermore, be am energy spreads of less than 1% can be obtained by pure geometrical collimation. Derails of the beam properties and background sources wil l be presented. It will be shown that this is an ideal beam for nuclea r physics and nuclear astrophysics studies. One example of this which takes advantage of the flux, energy resolution and polarization of the beam, is the study of Delta(33) excitations in finite nuclei. These i ntense polarized beams will also make it possible to perform precision measurements of the nucleon polarizabilities. And we will see that st udies in the vicinity of the photo-pion production threshold can provi de crucial tests of many of the recent predictions (Low Energy Theorem s) of Chiral Perturbation Theory. Our final example will show how the very intense beams available at low energies can be used to determine astrophysically important capture cross sections by measurements of th e inverse reactions.