protons (normalized to fission neutron damage factors) versus NIEL. The lower line (with a slope of one) indicates a linear relationship between the damage factor ratios and NIEL. The deviations from linearity are indicated with the upper line. [After Dale89b]. A similar figure in [Dale88] also shows deviations for transistor damage factors measured for electrons. Deviations from the linear dependence of Si displacement damage factors with the NIEL energy dependence are shown in figure 7, which shows the proton to neutron damage factor ratios for several devices plotted as a function of NIEL [Dale88]. The damage factors represent changes in the minority carrier lifetime in the case of the transistor data, and the generation lifetime in the case of the CID and CCD dark current damage factors. A slope of one on the log-log plot indicates a linear relationship, and the observed deviation from linearity is noted by the top curve. Dale et al. defined a "damage enhancement factor" as the ratio of observed damage factor ratio (upper line) to that expected based on the linearity with NIEL (lower line). In this work, the PKA spectrum produced in Si by the various incoming particles was calculated. Note that the PKA spectrum varies significantly over the range of proton energies of interest in space. It may come as a surprise that the PKA spectrum of a 60 MeV electron is more like that of a 10 MeV proton, than a 10 MeV proton is like a 60 MeV proton. As seen in figure 8, the damage enhancement factor is found to correlate with the fraction of the total NIEL due to PKAs with energies less than 1 keV. It is notable that the result held for the wide range of PKA spectra produced by 4.1 MeV electrons, all the way to 1 MeV-equivalent neutrons that produce very high energy recoils. The observed deviations from linearity would be expected if there were less recombination of initial vacancy-interstitial pairs IV-65 that are formed by lower energy PKAs (which produce well-separated Frenkel pairs). This result is consistent with the