A neutron detector using silicon pin photodiodes

Silicon pin photodiodes in recent years have been used as detectors for charged particle and low energy X- and gamma-ray spectroscopy instead of conventional surface barrier detectors. This is because pin photodiodes have a higher energy resolution, and the cost required for these purposes is lower. The present paper describes the development of a highly sensitive and small sized neutron detector for personal monitoring using pin photodiodes with a gadolinium-foil neutron converter. A detection efficiency of 3.1 % is obtained for thermal neutrons by detecting internal conversion electrons emitted from a gadolinium-foil converter. Gamma-component contained in the output pulses is cancelled nearly completely by using twin photodiode with tin foil instead of the gadolinium converter. A low detection limit of 240 cm-2sec-1 for thermal neutron flux density is obtained under gamma-background with a dose rate of 25 μSv/hr. Since the present neutron detector is also sensitive to gamma-rays, it is suitable to measure the equivalent dose rate in a mixed field of neutrons and gamma-rays. The detector could be useful for the construction of real-time neutron dosimeters. (N.K.)