Radioisotope power sources are attractive due to their power delivery capability that spans decades and comes from the long half-lives of beta (β)-emitting isotopes. Further advantages in combat are their low mass and low volume compared with chemical power sources. Damage to wide-band-gap semiconductors has been measured for high-flux-space applications. Less effort has been put into characterizing damage from lower-flux environments. Material damage is reported for two configurations. The electrical outputs from indium gallium phosphide β-photovoltaic cells with an initial exposure of 50 mCi of 63Ni nickel (99-year half-life) have been measured over a period of 19 months. The total energy conversion efficiency for this geometry is only 0.2%, and the electrical output is compared with the isotope decay over time. No measurable damage is measured within calculated statistical variation. Additionally, the electrical outputs from silicon carbide β-voltaic (βV) cells with an initial exposure of 46 mCi of 147Pm promethium (2.62-year half-life) have been measured over a period of 2.3 months. Initial results show the βV cell half-life to be 0.88 year, reduced significantly from the 2.6-year half-life of 147Pm alone.
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