Nov 26 – 27, 2020
RIKEN Wako Campus
Asia/Tokyo timezone

Development of a neutron detector for nuclear data measurement using high-intensity neutron beam / 高強度中性子ビームを用いた核データ測定のための中性子検出器の開発

Nov 26, 2020, 5:03 PM
1h 47m
RIBF201 (RIKEN Wako Campus)


RIKEN Wako Campus

Hirosawa 2-1, Wako City, Saitama 351-0198, Japan
Poster Presentation Poster


Hideto / 秀仁 Nakano / 中野 (Tokyo Institute of Technology / 東京工業大学)


Highly precise neutron nuclear data is required in nuclear transmutation research of long-lived minor actinides (MA) in nuclear waste. In neutron capture cross section measurement, monitoring the number of the incident neutrons is necessary. However, in measurement with J-PARC/ANNRI, direct neutron monitoring system has not been employed. To make measurement with ANNRI more robust, an additional neutron beam monitor is required. Conventional neutron detectors cannot be used as a beam monitor at ANNRI because of two reasons, high counting rate environment and gamma-flash. The neutron flux at ANNRI is one of the highest in the world. Gamma-flash, an intense gamma-ray burst produced when the proton beam pulse bombards the spallation target, can paralyze a detector generally used in nuclear data measurement. In general, a semiconductor detector or an inorganic scintillator, which is adopted for a neutron detector, has relatively longer response time and is unsuitable for beam monitoring at ANNRI.
Therefore, a combination of a thin plastic scintillator and a $^6$LiF foil was selected as a detection system, whose fast response enabled detecting neutrons at a high counting rate. Low gamma ray sensitivity of a thin plastic scintillator allows measuring fast TOF region without count loss or detector paralysis. The geometry of the $^6$LiF foil, the plastic scintillator, and photomultiplier tube (PMT) was designed. The optimal thickness of the $^6$LiF foil was determined with simulation codes, SRIM and PHITS. A $^6$LiF foil was made by vacuum deposition method. A test detector system was built to study the feasibility of the method.
The detector system was tested under the high neutron irradiation condition at J-PARC /ANNRI. A neutron TOF spectrum was successfully measured without significant count loss or detector paralysis. A neutron energy spectrum was driven from difference of TOF spectrum with and without $^6$LiF. The neutron spectrum was compared with a past neutron spectrum and good agreement was obtained. Statistic error was 0.68 % at 6.0 meV even though measurement times in this study was pretty short (~11 min).

Primary author

Hideto / 秀仁 Nakano / 中野 (Tokyo Institute of Technology / 東京工業大学)


Prof. Tatsuya Katabuchi (Tokyo Institute of Technology) Gerard Rovira Leveroni (JAEA) Yu Kodama (Tokyo Tech) Kazushi Terada (Kyoto University) Dr Atsushi Kimura (JAEA) Dr Shoji Nakamura (JAEA) Dr Shunsuke Endo (JAEA)

Presentation materials