Very high efficiency fusion reactor concept

Very high fusion reactor net efficiencies (>65%) are shown to be feasible through a new mode of advanced fuel tandem mirror operation. Inducing nonadiabaticity for fusion products not needed to sustain the plasma against losses enhances their end loss rate, leading to a narrow end loss energy spectrum and resultant very high efficiency direct electrostatic conversion. Magnetic field gradients required for non-adiabaticity are estimated, an approximate power balance is calculated, and a reference case is generated. Operation of D- 3 He reactors in this mode is particularly interesting, because of the recent discovery of a substantial 3 He resource on the lunar surface.