Performance measurement of the scintillator with optical fiber detector for boron neutron capture therapy.

The thermal neutron flux can be easily measured in real time by using the scintillator with optical fiber (SOF) detector. However the irradiation damage under high-intensity neutron flux causes deterioration of the SOF detector due to radiation damage to the plastic scintillator in which (6)LiF is blended. After irradiating the SOF detector for 4 h (thermal neutron fluence is approximately 2.0 x 10(13)neutrons/cm(2)), the sensitivity of the SOF detector decreased by 3.0%. After irradiating the SOF detector for 2 months (thermal neutron fluence approximately 6.4 x 10(14)neutrons/cm(2)), the sensitivity was reduced to 42% of baseline. Supposing that the thermal neutron fluence is 2 x 10(12)neutrons/cm(2) on the surface of a patient in a BNCT treatment, the sensitivity of the SOF detector is reduced by approximately 0.3%. This report presents investigations on the deterioration of the SOF detector in irradiation experiments.