D3He

D3He (deuterium–helium-3 fusion) refers to the fusion reaction between a deuteron (2H) nucleus and a helium-3 (3He) nucleus. The principal fusion channel is D + 3He → 4He + p, releasing about 18.3 MeV of energy per reaction. The reaction yields a helium-4 nucleus and a high-energy proton, with most of the energy carried by the charged products.

D-He-3 fusion is considered aneutronic because it produces very few neutrons compared with the deuterium–tritium fusion reaction. This reduces neutron-induced material activation and simplifies radiation shielding. In practice, the neutron yield is still nonzero due to competing reactions, but remains significantly lower.

Achieving meaningful rates requires very high temperatures and strong confinement. The D–He-3 cross section is smaller at practical fusion temperatures than that of D–T, and ignition temperatures are higher, making reactor-scale breakeven more challenging. Power from the reaction would be primarily in charged particles, offering potential for direct conversion of kinetic energy to electricity, bypassing a conventional thermal cycle.

Fuel availability is a major hurdle. Helium-3 is extremely scarce on Earth and costs are high; potential sources include extraterrestrial environments (e.g., lunar regolith, certain gas-giant atmospheres) or in-situ production, but no large, economical supply exists today. Some D–He-3 concepts consider breeding or using mixed fuels to improve feasibility.

Research into aneutronic fusion includes magnetic confinement and inertial confinement approaches, with ongoing theoretical and experimental work aimed at evaluating performance, safety, and economics. No net-energy D–He-3 reactor has been demonstrated.