Fusion/Fission Damage Ratios for Neutron-Induced Displacement Damage in Silicon.

摘要

Neutron induced displacement damage in silicon has been calculated and measured for a number of threat and simulator neutron spectra. The results in each case are presented as the ratio of damage produced by the source neutrons to that produced by 14 MeV (fusion) neutrons. The program to calculate damage determines the Lindhard nuclear stopping fraction corrected for multiple collisions, thus providing the fraction of the recoil energy available for displacement damage. For the measurements, wide-base silicon diodes were exposed to appropriate neutron fluences at each of the simulators. Diode changes that reflected the degradation in injected carrier lifetimes were observed. The results have produced both calculated and experimental ratios that are in generally good agreement with each other, and they are considerably smaller than the currently accepted values.