A Spin-Polarised Thermionic Converter for High-Temperature Heat

The device examined here is a spin-polarised thermionic converter intended for converting concentrated high-temperature heat directly to direct-current power without moving parts. Its operating principle is that a heated low-work-function emitter releases electrons across a narrow vacuum gap to a cooler collector, and a spin-polarised emitter coating is used to suppress back-emission in the sizing model. The design is computed from stated assumptions throughout; it is simulated, not measured, and no prototype results are reported. The headline result is a electrical output of 35.7 W, obtained with heat input at the emitter of 900 W with a computed efficiency or performance coefficient of 3.96 per cent where that measure applies, for a unit of mass 1.8 kg whose characteristic scale is a emitter temperature of 1.4e+03 K. 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, 1.02e+04 kg per cubic metre, sits about 54 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 exponentially sensitive to emitter temperature and work function, so coating ageing moves the operating point strongly. Status: SIMULATED, NOT MEASURED.