HIGH VOLTAGE GALLIUM PHOSPHIDE POWER CONVERTERS FR BETAVOLTAIC BATTERIES

ASTROPOWER IS DEVELOPING GALLIUM PHOSPHIDE ENERGY CONVERTERS OPTIMIZED FOR RADIO LUMINESCENT LIGHT-BASED POWER SUPPLIES. A "TWO-STEP" OR "INDIRECT" PROCESS IS USED WHERE A PHOSPHOR IS EXCITED BY RADIOACTIVE DECAY PRODUCTS TO PRODUCE LIGHT THAT IS THEN CONVERTED TO ELECTRICITY BY A GAP ENERGY CONVERTER. THIS INDIRECT ENERGY CONVERSION OF BETA-RADIOATION TO ELECTRICAL ENEERGY CAN BE REALIZED BY APPLYING RECENT DEVELOPMENTS IN TRITIUM-BASED RADIO LUMINESCENT (RL) LIGHT SOURCES IN COMBINATION WITH THE HIGH CELL OPERATING VOLTAGES THAT CAN BE ACHIEVED UNDER LOW ILLUMINATION WITH GALLIUM PHOSPHIDE PHOTODIODES. ADDRESSED IS THE DEVELOPMENT OF SEMICONDUCTOR POWER CONVERTERS THAT ARE SUITABLE FOR LOW ACTIVITY RADIOISOTOPE FUELS SUCH AS TRITIUM (T2). TRITIUM HAS BEEN NEGLECTED IN SEMICONDUCTOR CONVERSION DUE TO ITS LOW AVERAGE ENERGY EMISSION, 5.7 KEV, BUT RECENT MATERIAL ADVANCES HAVE MADE TRITIUM SOURCES PRACTICAL. TRITIUM HAS A RELATIVELY LONG HALF-LIFE, A SAFE DECAY PRODUCT, IS EASILY SHIELDED, AND IS REQUIRED IN ONLY SMALL AMOUNTS FOR MILLIWATT POWER SUPPLIES.