Evaluation of two-stage system for neutron measurement aiming at increase in count rate at Japan Atomic Energy Agency - Fusion Neutronics Source

Shinohara, Koji; Ishii, Keiichi*; Ochiai, Kentaro; Baba, Mamoru*; Sukegawa, Atsuhiko; Sasao, Mamiko*; Kitajima, Sumio*

A neutron flux array is one of the important plasma diagnostics to obtain the information on fast ion population. However, the limited flux owing to its collimator results in the small number of pulse counts and the large statistical error. The method to increase the pulse counts is required. Here, we propose a multi-stage neutron detection system, in which several sets of a scintillator and photo-multiplier tube (PMT) are placed in a line-of-sight. In order to evaluate the performance of the multi-stage detection system, we have carried out experiments on a two-stage detection system using a neutron beam at FNS (Fusion Neutronics Source) of JAEA (Japan Atomic Energy Agency). The results have shown the concept of the multi-stage detection system works as expected. In the best setup, the test two-stage system reached about 1.7 (1.8) times the efficiency of a single scintillator and PMT system for 2.54 (14) MeV neutrons.