Development of a small scintillation detector with an optical fiber for fast neutrons

To investigate the characteristics of a reactor and a neutron generator, a small scintillation detector with an optical fiber with ThO2 has been developed to measure fast neutrons. However, experimental facilities where 232Th can be used are limited by regulations, and S/N ratio is low because the background counts of this detector are increase by alpha decay of 232Th. The purpose of this study is to develop a new optical fiber detector for measuring fast neutrons that does not use nuclear material such as 232Th. From the measured and calculated results, the new optical fiber detector which uses ZnS(Ag) as a converter material together with a scintillator have the highest detection efficiency among several developed detectors. It is applied for the measurement of reaction rates generated from fast neutrons; furthermore, the absolute detection efficiency of this detector was obtained experimentally.