Compton Scattering By Nuclei At HIgS

Brent Perdue

Monochromatic beams of 100% linearly polarized g-rays are produced at the High Intensity g-ray Source (HIgS) via electronic Compton scattering of FEL photons. The excellent quality of the beam coupled with its high intensity, 105-107 gammas/sec/MeV, make it ideal for nuclear physics experiments. One such application is Compton scattering by nuclei. A measurement has been made of nuclear Compton scattering by 16O. A 1 inch diameter collimated g-ray beam (measured DE/E = 10%) is incident on a 10 inch long, 1.125 inch diameter H2O target. The scattered g-rays are detected by four 10 inch by 10 inch NaI detectors. The supporting apparatus can be configured to place the detectors at any polar angle between 30° and 150° and has full azimuthal coverage. An operational mode of the OK-4/FEL that produces giant high-peak power pulses is employed to reduce room background by a factor of 100. A preliminary result of the asymmetry as a function scattering angle will be shown. 
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