Gamma ray diagnostics for high time resolution measurement in large helical device

Abstract

Abstract A 1-inch LaBr3:Ce gamma ray scintillation detector, characterized by high time and energy resolution, was installed to advance energetic particle physics studies in Large Helical Device (LHD). We reduced the size of the scintillator from 3 inches to 1 inch to reinforce the radiation shielding to reduce the unwanted signal in the detector induced by fast neutrons and stray gamma rays according to the commissioning results. The radiation shielding composed of 10% borated polyethylene and lead was redesigned to suppress the gamma-ray induced signal based on the Monte Carlo three-dimensional neutron and gamma-ray transport code MCNP6. We increased the lead thickness from 50 mm to 77.5 mm to suppress the stray gamma ray effect. The gamma ray spectrum was measured in the hydrogen neutral beam heated deuterium plasma with 6LiF pellet injection. We might obtain a gamma ray peak near 0.48 MeV due to the 6Li(d,p'γ)7Li reaction.