The Time-Energy Response of NaI and CsI Crystals to 14 Mev Neutrons

摘要

A series of pulsed neutron and activation measurements werenperformed on bismuth and lead shielded NaI and CsI crystals. Thenmajor neutron induced reactions in the shields and crystals havenbeen identified and analyzed. Intensity ratio factors for the variousnlong terms (l sec - 4 hours) activities, as a function of thencounting energy interval, have been obtained. An expression isngiven whereby these ratio factors can be used to calculate thenbuild up of these activities in a pulsed experiment. The valuesnwhich were obtained for the ratio of σ 23 Nε (n,a) to σ 23 Na (n,p)nranged between 2.1 ± 0.4 and 4.4 ± 0.9. These values are in fair agreement with the value of 3.3 ± 0.8 which was obtained by Bormann et al (5). Pulsed measurements on bismuth and lead indicate the possibility of constructing directional fast neutron bismuth and lead counters.