Study of Response Functions of the High-Resolution High-Energy Photon Spectrometer

Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Igashira, Masayuki*; Harada, Hideo   ; Furutaka, Kazuyoshi  ; Nakamura, Shoji  

This work aims at high-precision Monte Carlo simulations of response functions of the high-resolution high-energy photon spectrometer (HHS) to rays in the energy region of 1-20 MeV and at determination of energy distributions of high-energy laser inverse-Compton rays. The HHS is composed of two coaxial-germanium detectors (Twin Ge) surrounded by BGO scintillation detectors. Full-energy peak efficiencies and response functions of the Twin Ge were measured with standard ray sources. Response functions of the HHS to 10.7 MeV rays from the Al(p, ) reaction were measured at the Tokyo Institute of Technology. Finally, 20-, 30-, 40-MeV rays produced in laser inverse-Compton scattering were measured with the HHS at the National Institute of Advanced Industrial Science and Technology. The experimental response functions were in excellent agreement with EGS4 Monte Carlo simulations that incorporate imperfect charge collections arising from the surface channel effect. Energy distributions of the high-energy laser inverse-Compton rays were determined by means of high-precision Monte Carlo simulations.