Development of a wavelength-shifting-fibre-based scintillator neutron detector as an alternative to 3He at J-PARC/MLF

A wavelength-shifting-fibre-based scintillator detector has been developed as an alternative detector to 3He gas. The detector is intended for use in an inelastic neutronscattering instrument at J-PARC. The detector being developed, which is based on the one made for a SENJU diffractometer, is designed to cover a large scattering angle with a moderate pixel size as well as exhibiting a high detection efficiency, low gamma-ray sensitivity and low background count rate. A prototype detector with a pixel size of 20 x 20 mm and a neutron- sensitive area of 320 x 320 mm2 has been constructed. This paper describes the design of the detector and its performance relative to the original SENJU detector.