A Compton scattering method for the high flux energy spectrum measurement of inverse Compton scattering gamma-ray sources

摘要: The Very Compact Inverse Compton Scattering Gamma-ray Source (VIGAS) is a gamma-ray facility under construction at Tsinghua University. It has the ability to produce more than $10^6$ quasi-monoenergetic gamma photons per pulse within 10 ps. Due to ultra-short pulse length, conventional detectors and methods cannot directly measure the energy spectrum of the VIGAS. In this study, we employ the Compton scattering method to reduce the photon flux and collect the scattered photons in a specific direction using high-purity germanium (HPGe) detectors. The central energy and energy spread of the incident gamma rays can be determined by analyzing the spectrum of the scattered photons. To correct for the Doppler broadening effect during the Compton scattering process, both the error transfer formula method and the neural network method are developed. Monte Carlo simulations show that the energy spectrum of the VIGAS can be reconstructed accurately by both the two methods, with a central energy accuracy better than 0.1\% and energy spread accuracy better than 3\%. A proof-of-principle experiment conducted at the Shanghai Laser Electron Gamma Source (SLEGS) validates the feasibility of the Compton scattering-based reconstruction method for energy spectrum measurements.