increased LET and therefore more densely ionizing track structure. The importance of proton dose in LEO missions notwithstanding, there have been few carefully controlled comparisons of Co-60 versus proton-induced TID response. A discussion of much of the relevant data is found in [Ma-89]. Investigation into p-MOSFET dosimeter response to proton dose has indicated similar behavior to that reported in [Oldh-84], but with indications of correlation between charge yield and electric field strength [Augu-82]. Figure 10, which is reproduced from the later work, indicates the relation between threshold voltage shift and gate bias on 1100 langstrom thick oxides for several different radiations, including 37 MeV protons. In [Stap-85], a clear trend was noted in the threshold voltage shifts of p-MOS transistors for the case of heavy ions versus literature data on Co-60. However, the comparison between Co-60 and 62 MeV protons showed no significant difference at a dose of 10 krad(Si). Recent comparisons of modern p-MOS dosimeters indicate similar behavior with a possible slight reduction is high energy proton response versus that from Co-60 [Peas-99]. Three papers have reported comparisons of photon versus proton-induced dose in devices other than p-MOS dosimeters. A careful experimental and modeling effort into the IV-20 GEMINATE MODEL X SOFT OXIDES COLUMNAR HARD OXIDES MODEL PROTON ENERGY (MeV) Figure 9. This figure is reproduced from [Oldh-84], and it indicates the energy dependence of the two recombination models. The yield is fractional, and at high proton energies where the geminate model applies the yield is expected to be the same as with Co-60 Co-60 GAMMAS 7-MeV ELECTRONS 37-MeV PROTONS Cu X RAYS VG(VOLTS) Figure 10. p-MOSFET dosimeter response to dose from proton and other sources indicates a correlation between charge yield and gate bias which affects electric field strength. The oxide thickness is 1100 langstroms. IV-21 response of radiochromic dye film dosimeters indicated the importance of the columnar recomb