Spatial distribution and polarization of γ-rays generated via Compton backscattering in the Duke/OK-4 storage ring FEL

Beams of nearly monochromatic gamma -rays are produced via intracavity Compton backscattering in the OK-4/Duke storage ring FEL, the high-intensity gamma -ray source (HI gammaS). Presently, HI gammaS generates gamma -ray beams with an energy tunable from 2 to 58 MeV and a maximum flux of 5 x 10(7) gamma -rays per second. The gamma -rays are linearly polarized with a degree of polarization close to 100% (V.N. Litvinenko, et al., Predictions and expected performance for the VUV OK-5/Duke Storage Ring FEL with variable polarization, Nucl. Instr, and Meth. A, to be published in this proceeding) and they are collimated to pencil-like semi-monoenergetic beams with RMS energy spreads as low as 0.2%. The detailed theoretical and experimental studies of the gamma -ray beam quality were conducted during the last two years (S.H. Park, Thesis, Duke University, Durham, NC, USA, 2000). In this paper, we present the theoretical analysis and the experimental results on the spatial distribution and polarization of gamma -rays from the HI gammaS facility. (C) 2001 Elsevier Science B.V. All rights reserved.