Gate rupture and SEB continue to be a critical problem for space systems, particularly for devices with voltage ratings > 200 V.  Tests by manufacturers have used ions with insufficient range, leading to safe operating recommendations that are far above the actual voltage where SEGR takes place.   This task will evaluate SEGR in power MOSFETs, comparing test results with “normal” and very long range ions.  Computer modeling will be used to show how ion range affects test results.  A guideline will be written for SEGR testing and recommended derating practice.