End-to-end spectrum reconstruction method for analyzing Compton gamma-ray beams

A gamma-ray beam produced by Compton scattering of a laser beam with a relativistic electron beam has been used for nuclear physics research at the high intensity γ -ray source ( HI γ S ) facility at Duke University. The success of many experiments using the gamma-ray beam critically depends on the accurate knowledge of the gamma-ray beam energy distribution which is typically obtained by unfolding a measured energy spectrum. Conventionally, the detector response function used in the spectrum unfolding is simulated by a simple Monte Carlo code in which an isotropic gamma-ray event generator is used. However, for a Compton scattered gamma-ray beam, this simulation method could lead to an inaccurate detector response function, since it neglects the spatial and energy distributions of the gamma-ray beam. In this paper, we will present a novel end-to-end gamma-ray spectrum reconstruction method by completely modeling the process of the Compton gamma-ray beam production, collimation, transportation and detection. Using this method, we have successfully reconstructed the energy distribution of HI γ S beams for nuclear physics research with a high degree of accuracy.