Alpha Heating and Self-Heating

The 3.5 MeV alpha from each D-T reaction stays confined and heats the plasma; at Q_sci 3.076 alpha heating is a meaningful part of the power balance.

The plasma heating itself

Of the 17.6 MeV each D-T reaction releases, 3.5 MeV goes to the alpha particle. Being charged, the alpha stays confined by the magnetic field and gradually transfers its energy to the surrounding plasma through collisions. This alpha heating is internal, free of external power, and grows with the fusion rate.

At Q_sci 3.076 the alpha heating is a significant fraction of the total plasma heating — the plasma is partly self-heated, though not self-sustaining. Higher gain means a larger self-heated fraction; ignition is the limit where alpha heating alone sustains the burn with no external input. Hyperion sits below that limit, relying on external heating on top of alpha self-heating.

Why confinement of alphas matters

Alpha heating only works if the alphas stay confined long enough to thermalize. Field ripple, MHD activity, and orbit losses can expel alphas before they deposit their energy, subtracting from self-heating and adding heat load to the wall. Confining fast alphas well is therefore part of hitting the gain target, and quantifying alpha confinement at Hyperion's parameters is a design-and-simulation task.

• 3.5 MeV alpha per reaction, confined and thermalizing in the plasma
• At Q 3.076 a meaningful part of heating is internal
• Alpha loss (ripple, MHD) subtracts from the self-heating budget

This page describes a design-and-simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. No hardware net-gain is claimed before FOAK.