Orbital Equivalence of Terrestrial Radiation Tolerance Experiments

Abstract

High-energy (>40 MeV) protons are commonly used to characterize radiation tolerance of space electronics against damage caused by energy transfer to the nuclei and electrons of semiconductor materials while in orbit. While practically useful, these experiments are unrepresentative in terms of particle type and energy spectra, which results in disproportionate amounts of displacement damage and total ionizing dose. We compare these damages to those realized by bulk semiconductors used in optoelectronics in common low, medium, and high Earth orbits by calculating the duration in orbit required to achieve equivalent nuclear and electronic energy deposition. We conduct this analysis as a function of test proton energy, material, material thickness, and shielding thickness. The ratio of nuclear to electronic orbit duration, a value which would approach unity in an ideal radiation tolerance test, is found to exceed unity in the majority of cases but approaches unity as Al shielding increases. This study provides a connection between damage produced in terrestrial accelerator-based characterizations and orbit irradiation in terms of both damage modes which can cause optoelectronic components to fail: displacement damage and total ionizing dose.