Study of Beta Radioisotopes Direct Energy Converters

Report No. ARL-TR-4969
Authors: Y. Ngu and M. Litz
Date/Pages: September 2009; 22 pages
Abstract: Energy stored in the nucleus of radioisotopes contains energy-densities five orders of magnitude higher than the energy-density of chemical bonds. The decay modes (and decay products) of these high-energy-density materials can then be matched to direct energy conversion materials for best efficiency. The choice of converter material, packaging geometry, thickness of material layer, and number of layers will necessarily depend on the specific radioisotope output product (alphas, betas, or gammas) and the energy of the particles (17 eV up to 5.5 MeV). Samples of silicon (Si) and silicon carbide (SiC) p-i-n diodes have been irradiated with betas from 90Sr and 63Ni. The voltage and current of the devices prior to irradiation were measured and compared to measurements made during periods of radiation. The sample diodes generate on the order of 10 pW in the presence of a 7.5 mCi source. This represents a direct-energy-conversion of beta-radiation to electrical power efficiency of ~7%.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2009