Why Helium-3 Is the Burner's Fuel
Helium-3 lets the burner run a mostly-aneutronic reaction with charged products, trading extreme fuel scarcity for low neutron damage and direct conversion.
The trade the burner makes
Every fusion fuel is a compromise. D–T is easy to ignite but throws 80% of its energy into 14 MeV neutrons, which activate structures and demand heavy shielding and remote handling. D–3He is far harder to burn — it needs higher temperatures and better confinement — but its primary channel is aneutronic and its products are charged. Aegis accepts the harder physics to gain a cleaner, lower-signature machine suited to fixed installations.
- Low neutron output → less activation, lighter shielding, longer component life
- Charged products → direct energy conversion is possible
- No tritium as a primary fuel in the burner → a smaller radiological inventory on site
- Cost: helium-3 is scarce and must be bred
Why the tandem mirror suits it
D–3He rewards a device that can hold a very hot, well-confined central plasma and recover charged-particle energy at the ends. The tandem mirror does both: high-field end plugs (26.49 T) build an electrostatic barrier that holds ions in the central cell, and the expanding field at the ends spreads the escaping charged flux for direct conversion. The fuel choice and the machine geometry are chosen together.
The catch is supply. p–11B is even cleaner but presently unreachable; D–3He is reachable but needs a helium-3 source. Solving that source problem on Earth is the entire point of the breeder–burner pairing.