Neutron beam design for low-intensity neutron and gamma-ray radioscopy using small neutron sources

Abstract

Two small neutron sources of /sup 252/Cf and /sup 241/Am-Be radioisotopes were used for design of neutron beams applicable to low-intensity neutron and gamma-ray radioscopy (LINGR). In the design, Monte Carlo code (MCNP) was employed to generate neutron and gamma-ray beams suited to LINGR. With a view to variable neutron spectrum and neutron intensity, various arrangements were first examined, and neutron-filter, gamma-ray shield, and beam collimator were verified. Monte Carlo calculations indicated that with a suitable filter-shield-collimator arrangement, thermal neutron beam of 3900 ncm/sup -2/s/sup -1/ with neutron/gamma ratio of 7 /spl times/ 10/sup 7/, and 25 ncm/sup -2/s/sup -1/ with very large neutron/gamma ratio, respectively, could be produced by using a /sup 252/Cf (122 /spl mu/g) and a /sup 241/Am-Be (37 GBq) radioisotopes at the irradiation port of 35 cm from the neutron sources.