ON THE ENERGY BEHAVIOR OF FAST D-T NEUTRONS GENERATED BY HOLLOW-CYLINDRICAL DEUTERON BEAMS ACCELERATED ONTO PLANE TRITIUM TARGETS

There exist considerable requirements for the comprehensive characteri sation of fast neutron fields produced by extended sources. These need s are driven in part by fusion research, neutron damage studies and ef forts towards defining the efficiency of nuclear reaction production. The work contained herein concerns the spatial dependency of neutron e nergy in the vicinity of homogeneous targets. The study also examines the d-T exoergic nuclear reaction generated in nondispersive media by uniform hollow-cylindrical accelerated particle beams. In particular c ircumstances, the elementary neutron emission process can be considere d to be omnidirectional (due consideration being paid to collision kin etics, which depend upon mass and kinetic energy of the particles invo lved in nuclear collision and to nuclear reaction energy, etc.) and co nsequently, analytical expressions can be considerably simplified. Exa mination is made of an In-type functional dependence for fast neutron energies, this being typical of, for instance, ring-shaped d-T neutron sources. The spatial distribution of the energy of neutrons produced by this particular type of source passes through maximum values at poi nts whose locus is described by circles with radii depending upon the ratio of the fast neutron source emitting ring (inner and outer) radii . The consequent fast neutron iso-doses can be analytically described by quartic equations, with the ring radii ratio as a parameter and the emitter axis as the axis of symmetry. The description of spatial neut ron energy distribution as well as exoergic reaction production and ne utron dosimetry described by these expressions is supported by empiric al data obtained using 14.1 MeV d-T neutron generators. (C) 1997 Elsev ier Science Ltd. All rights reserved.