Degradation of boron trifluoride and helium detectors in neutron and gamma fields

Measurement of-degradation due to neutron and gamma exposure was performed for five models of boron trifluoride (BF₃) detectors from major suppliers, and for a model of reduced-sensitivity helium (³He) detector achieved using a different chemical and isotopic gas composition than that of regular ³He detectors. The detectors tested all have about the same nominal thermal neutron sensitivity and overall dimensions. The results showed widely different neutron and gamma durability for BF₃ models, an undesirable time-dependent gamma degradation followed by recovery for models, and very robust performance of the modified ³He detector