A Betavoltaic Cell with a Density-Capped Shielding Design

The module set out in this paper is a betavoltaic cell intended for powering unattended remote instruments for a decade without servicing. Its operating principle is that tritium beta particles deposit energy in a wide-bandgap semiconductor junction, generating current continuously for years, and the shielding thickness is set in the design basis by an explicit density margin calculation. The design is computed from stated assumptions throughout; it is simulated, not measured, and no prototype results are reported. The headline result is a initial electrical output of 2.7 µW, obtained with beta decay power of 0 mW with a computed efficiency or performance coefficient of 8 per cent where that measure applies, for a unit of mass 0.9 kg whose characteristic scale is a source activity of 37 GBq. A parameter sweep reported in the Results section shows how the output moves when the principal variable is changed, and the density of the working material, 1.13e+04 kg per cubic metre, sits about 53.9 orders of magnitude below the neutron-carrier density bound of 9.72e+57 kg per cubic metre, so the bound enters this design as a sizing ceiling and a margin statement rather than as an operating condition. The limitations are stated plainly: output is fixed by the source and decays with the twelve-year half-life; licensing and encapsulation, not conversion physics, dominate deployment. Status: SIMULATED, NOT MEASURED.