An improved 3He nuclear reactor with provision for direct electric conversion of a relativistic proton stream into useable electric power at a voltage level compatible with the national power grid (one million V DC). Various embodiments include multiple collector cages for extracting relativistic protons of various energy levels, diverter wires for deflecting high-energy proton streams to either side of lower energy cages to avoid unwanted impact. Other embodiments include arrangements for dividing multi-megavolt voltages down to a useable one megavolt level compatible with the national power grid. Further embodiments comprise guiding the proton stream by the cusps of magnetron cavities to permit conversion of the relativistic proton energies into microwave power. A proposal is also made for harvesting 3He from the Moon to supply earth-bound and space-bound reactors. A solution to the problem of charging a potential well-forming anode in an electrostatic fusion reactor without electrical arcing is further disclosed.