Measurement of neutronic characteristics in JSNS and its improvement

JSNSの中性子特性の測定とその改善

原田 正英   ; 及川 健一   ; 前川 藤夫  ; 明午 伸一郎   ; 二川 正敏  

Harada, Masahide; Oikawa, Kenichi; Maekawa, Fujio; Meigo, Shinichiro; Futakawa, Masatoshi

To validate the neutronics design of JSNS, we have measured neutron spectra at all available neutron beam lines by a current-mode TOF (C-TOF) method. Measured values were in good agreement with evaluated ones for beam lines without guide tubes. Some discrepancies in spectral intensity were found in some of beam lines using a neutron guide tube. This result indicates that the C-TOF method is very useful for checking initial installation of beam lines because neutron spectral intensity can be measured systematically in a short time (several shots). On the other hands, we also found that the C-TOF method had larger measurement error than pulse counting type detector. Therefore, to reduce measurement error, we had additional experiments. It was found that measured Li-6 contents in scintillators were different from values in specification data sheets. Then, amount of charge produced in photomultiplier by a detected neutron was measured. As a result, the measurement error could be reduced.