The Deuterium–Helium-3 Reaction
D + He-3 fuses to a helium-4 nucleus and a 14.7 MeV proton, releasing 18.35 MeV entirely in charged particles.
The primary branch
The reaction the burner is built around is D + 3He → 4He (3.6 MeV) + p (14.7 MeV). The total energy release is 18.35 MeV, and in this branch all of it appears as kinetic energy of charged particles — a helium-4 nucleus and a proton. No neutron is produced in the primary branch.
Because the products are charged, they are steered by the magnetic field and can be collected electrostatically. That is the physical premise for direct energy conversion. In a deuterium–tritium machine, by contrast, roughly 80% of the yield is carried by a 14.1 MeV neutron, which is uncharged and must be caught in a blanket and converted as heat.
Why the charged fraction is the point
The value of D–3He is not that it is clean of neutrons — it is not — but that the dominant energy channel is charged. Charged energy can bypass a thermal cycle. The trade is a much higher required temperature and a scarce fuel; those penalties drive the burner's honest gates.
The reaction also depends on temperature: the products above are fixed by kinematics, but how often the reaction occurs is set by the ion energy and density. At the burner's ~90 keV operating point the rate is high enough to matter, though still below D–T at the same conditions. Everything downstream — direct conversion, low activation, the fuel-supply gate — follows from this one branch and the charged particles it produces.
- Primary branch: D + 3He → 4He + p
- Yield: 18.35 MeV, entirely charged
- Enables direct conversion of the main channel
- Neutrons arise only from side reactions (~5.44%)