Prompt gamma-ray analysis using cold and thermal guided neutron beams at JAERI

A highly sensitive neutron-induced prompt gamma-ray analysis (PGA) system, usable at both cold and thermal neutron beam guides of JRR-3M, has been con structed. The system was designed to achieve the lowest gamma-ray backgroun d by using lithium fluoride tiles as neutron shielding, by placing the samp les in a He atmosphere and by using a Ge-bismuth germanate detector system for Compton suppression. The gamma-ray spectrometer can acquire three modes of spectra simultaneously: single, Compton suppression, and pair modes. Be cause of the low-energy guided neutron beams and the low-background system, analytical sensitivities and detection limits better than those in usual P GA systems have been achieved. Boron and multielemental determination by a comparative standardization have been investigated, and accuracy, precision , and detection limits for the elements in various materials were evaluated . The system has been applied to the determination of B and multielements i n samples of various fields such as medical, environmental, and geological sciences.