Enhanced Low Dose Rate Sensitivity at Ultra-Low Dose Rates

We present results on the effects of ELDRS at dose rates of 10, 5, 1, and 0.5 mrad(Si)/s for a variety of commercial, radiation hardened, and ELDRS-free devices. We observed low dose rate enhancement below 10 mrad(Si)/s in several different part types. The magnitudes of the low dose rate enhancement varied substantially. The most notable case showed dose rate sensitivity in the functional failures for a commercial voltage regulator, with initial failures occurring after 10 krad(Si) for the parts irradiated at 0.5 mrad(Si)/s. Radiation hardened and ELDRS-free devices also showed ELDRS at the ultra-low dose rates. An ELDRS-free high power regulator showed a low dose rate enhancement factor of ×33 after 10 krad(Si) for parts irradiated at 0.5 mrad(Si)/s. The enhanced degradation at the ultra-low dose rates present challenges for hardness assurance.