Development of wavelength-shifting-fiber neutron image detector with a fiber-optic taper with a high spatial resolution

Nakamura, Tatsuya  ; Yasuda, Ryo; Katagiri, Masaki*; To, Kentaro  ; Sakasai, Kaoru  ; Birumachi, Atsushi; Ebine, Masumi ; Soyama, Kazuhiko  

The neutron image detector that was based on wavelength-shifting-fibers (WLS fibres) equipped with the fibre optic taper (FOT) was developed. By inserting the FOT in between the scintillator and WLS fibers the measured neutron image was magnified on the WLS fibres, resulting in better spatial resolution. We have tested two FOTs; a square shaped one in a size of 2.6 2.6 mm and a round shaped with a diameter of 20 mm. Both FOTs have identical magnification ratios of 3.1. By implementing the larger FOT the detector has the neutron-sensitive area of 314 mm with the effective pixel size of 0.17 0.17 mm whilst the light transmission rate decreased 20% less compared to that with the small FOT. The detector equipped with the larger FOT exhibited a spatial resolution of 0.26 0.07 mm, which was similar to the one with the small FOT.