Improved flux uniformity with quadrilateral irradiation configuration for in vivo neutron activation analysis with radioactive (isotopic) neutron sources

Abstract

The irradiation configuration considered consists of two pairs of crossed bilateral units B(+). A conventional parallel opposed beam irradiation system consisting of two pairs of vertically arranged bilateral units B(//) was also considered. The results imply that the validity of intercomparison between the results of different individuals in a group of subjects or the same individual over a period of time may be much higher with the use of a B(+) than with a B(//) irradiation system. The major disadvantage with the B(+) irradiation technique is that with thin subjects the incidental loss of neutrons along the sides of a supine subject results in a reduction in the level of the thermal flux that would otherwise be obtained with the B(//) irradiation configuration. For diagnostic purposes, however, such a tradeoff may be worthwhile. The use of suitable reflectors may reduce the loss of neutrons.