Neutron radiation distribution sensor using flexible plastic scintillating fiber combined with the time-of-flight technique

A long fiber system has been made using two silica fibers connected to both ends of the plastic scintillating fiber (PSF). Its basic properties were investigated as a neutron radiation distribution monitor using the time-of-flight (TOF) method. From the experimental results using the fast neutron source reactor: YAYOI (University of Tokyo), the two linear relations were confirmed (1) between the incident position of and the time difference and (2) between the neutron flux level and the counting rate. The spatial resolution and the counting efficiency of this system were about 60 cm (FWHM) and about 1.0×10 ^-4 [counts/incident neutron] respectively, with the photomultiplier gain: 6×10⁵ and the discrimination level of constant fraction discriminators: 0.8 [V]. A neutron dose distribution measured by this system was compared with the result using a conventional neutron Sievert (Sv) counter. After some correction for the spatial resolution by an unfolding method, the two results were in good agreement