Charged Particle Simulation of Fast Neutron Damage

摘要

The motivation of this work is to compare atomic damage configurations associated with neutron and fast-ion damage. The question we set out to answer was: Which choice of ion mass and kinetic energy provides the best simulation of fast neutron damage. The answer which emerges is that the primary damage state, i.e. the statistical distribution of free defects, and subcascade regions before annealing, is remarkably independent of the ion species and its PKA spectrum. Experimentally single crystals of Mo were bombarded with 86Kr, 20Ne, 11B, 4He, and 1H in such a manner that the energy deposited into elastic collisions (displacement events) in the near surface region was approximately equal for each implant. The ion fluences spanned more than two orders of magnitude, and the resulting damage level at each fluence was monitored by obtaining aligned backscattered (channeling) spectra in a <111> axial direction. As an additional check on the channeling results selected implants were also examined with TEM. The channeling experiments clearly show that the final damage state, at all fluences, for 86Kr and 20Ne is the same. At low fluences, the final damage state for 86Kr, 20Ne, 11B, and 4He appears to be the same, but for high fluences there are unresolved difficulties with the 11B and 4He channeling results.