Temperature Dependence of Thermal Neutron Detection Performance of BF3 Proportional Counters

The operating temperatures of BF3 proportional counters are said to be limited to approximately 100°C for standard designs and 150°C for special designs, but no paper was found which described the details of temperature dependence of thermal neutron pulse height distributions obtained from them. All the counters tested showed a decrease in the pulse heights and a broadening of the peak widths as the temperature increased. Thermal neutron counting rates in two types of the counters stayed unchanged up to 150°C and in another type up to 100°C. The pulse risetimes did not change appreciably for the temperature change. This decrease in the pulse heights is in contrast with an increase in the pulse heights observed in He-3 proportional counters(E. Sakai, et al., IEEE Trans. Nucl. Sci., Vol. NS-27, No. 1, 776 (1980)).