Where the Charged-Particle Power Comes From

The burner is fueled to make its energy as fast charged particles, because only charged particles can be steered by fields into a direct converter.

Only charged particles can be converted directly

DEC works on charge. A magnetic field steers charged particles; an electric field does work on them. A neutron carries neither charge nor response to fields — it flies straight and deposits its energy as heat wherever it stops. So the fraction of fusion energy that DEC can capture directly is the fraction carried by charged products. Choosing a fuel and operating point that maximizes that fraction is the reason the burner runs on deuterium and helium-3.

The D-3He advantage

The primary reaction, D + 3He, releases 18.3 MeV entirely as charged particles: a 14.7 MeV proton and a 3.6 MeV helium-4 nucleus. Compare that to D-T, whose 17.6 MeV comes 80% as a neutron. For a direct converter, D-3He is the natural fuel — most of its yield arrives as steerable, decelerable charge.

The unavoidable neutrons

No D-3He plasma is purely aneutronic. Deuterium also fuses with itself, and one D-D branch makes a neutron; the tritium from the other branch can burn with deuterium to make a 14.1 MeV neutron. The burner's design point keeps this to a neutron fraction of about 5.44% of total power. Those neutrons are handled thermally — shielding, a modest heat-removal loop, and materials chosen for neutron tolerance — while the ~95% charged share feeds the DEC train.

This split is the quantitative basis for MetroVolt's low water use: because the great majority of the energy is converted directly, only the small neutron and loss fraction needs the kind of heat rejection that would otherwise call for a steam cycle and cooling water.