Gamma-ray-based fusion burn measurements

A gas Cerenkov detector with a 12-MeV threshold for gamma-ray detection has been built for use on the OMEGA laser system to record high-energy gamma r ays emitted during DT gas burn. Recording the 16.7-MeV gamma ray while disc riminating against the lower energy 14-MeV neutron-induced gammas is an imp ortant objective using this detector system. Detector design, sensitivity, and background studies were possible using the Integrated Tiger Series Mont e Carlo code modified to include Cerenkov production and full time-history of all particles. The results of this code were iterated with the ASAP opti cs code to optimize the light collection system, while providing the radiat ion shielding and stray light baffles to minimize backgrounds. As an initia l test of the instrument, 8-20 MeV electrons from the Idaho State Universit y linear accelerator were used in lieu of gamma rays. The primary results o f these tests are that electron-produced Cerenkov has been observed and the Cerenkov threshold curve established for this instrument. (C) 2001 America n Institute of Physics.