The effects of gamma radiation on digital micromirror devices

摘要

Digital micromirror devices (DMDs) are well suited for highly multiplexed spectroscopy applications. In astron-omy, DMDs can be used as a programmable slit mask in a multi-object spectrometer (MOS). There is stronginterest in utilizing DMDs for space-based MOS instruments. Over the past several years, we have carried outa program to evaluate the viability of XGA DMDs for operation in space, including their ability to survivethe launch environment. The DMDs we tested did not show any failures or adverse effects after mechanicalvibration and shock testing. Using heavy ion irradiation, we found that DMDs are susceptible to single eventupsets (SEUs), though all SEUs are non-destructive and can be cleared by loading a new pattern. The estimatedSEU rate for "worst week" conditions in interplanetary space was 5.6 upset micromirrors (out of 786,432) per 24hours. Using high energy protons, we found that DMDs began to show adverse effects at a total ionizing dose(TID) of 30 krad(Si) (which is well above the estimated TID for a 4 year mission). In this work, we presentthe TID testing performed using gamma rays from a Co-60 source at NASA GSFC. We tested 14 XGA devicesand found that individual micromirrors appeared nonfunctional after the devices accumulated TIDs of 16-19krad(Si). Devices recovered after annealing at room temperature in as little as 24 hours. Devices subjectedto the most severe radiation testing conditions were completely recovered after 18 weeks of annealing at roomtemperature. We also tested unbiased (un-powered) devices, which showed no effects up to a TID of 76 krad(Si)(which is the highest TID we achieved during our testing). This work concludes our efiorts to space-qualify XGADMDs, and shows that these devices are well-suited for deployment in space, except in the harshest radiationenvironments.