Isotope Energy Release and Deposition Characteristics in Betavoltaic Materials
Technical Report,15 Jun 2019,15 Feb 2020
US Army Combat Capabilities Development Command Army Research Laboratory Aberdeen Proving Ground United States
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A Monte Carlo nuclear scattering code Monte Carlo n-particle extended MCNPXhas been used to calculate electron energy losses in liquid-form radioisotope RI layers deposited on the surface of wide-bandgap semiconductor PIN junctions. The RI medium self-attenuation limits the RI layer thickness that is practical to deposit on the surface in order to achieve maximum electrical power output. The optimized RI layer thickness is defined here as the thickness that generates electrical power at 90 of the maximum energy transferrable to an underlying semiconductor layer. Liquid form isotope formats are evaluated using the optimal thickness approach as defined. It is found that for liquid form isotopes of 3 H, 63 Ni, 147 Pm, and 90 Sr, the optimal thicknesses are 2, 15, 50, and 250 m thick, respectively. These results can vary in practice because of recrystallization rate and humidity uptake in the liquid form RI over time, but are useful for design of prototypes, basis for material comparison, and providing guidance for future experimental goals. This evaluation is expected to serve as a reference that enables predictions in future design of stacked volumetric power sources.