Direct Energy Conversion Equations
How charged fusion products can be decelerated against an electric field to produce electricity without a thermal cycle.
Skipping the heat engine
Conventional power plants convert heat to electricity through a thermal cycle limited by Carnot efficiency. If fusion products are charged, their kinetic energy can instead be converted directly to electricity by decelerating them against an electrostatic field, in principle at high efficiency. The energy balance for a single collector stage is simply:
eta = (energy delivered to load) / (initial kinetic energy) = qV_collector / E_particleA charged product entering a region held at high potential does work against it as it slows; that work appears as electrical energy in the external circuit.
Why it needs charged products
Direct conversion only works on charged particles that can be steered and decelerated by fields. Neutrons carry no charge and cannot be converted this way; their energy must be captured as heat. This is why aneutronic or low-neutron fuels are attractive for direct conversion: more of the yield is in charged particles.
Practical schemes
- Venetian-blind and multi-grid collectors sort particles by energy for efficient deceleration
- Traveling-wave and periodic-field converters handle a spread of energies
- Expander regions in mirror end cells spread the beam before collection
How it is modeled
Particle trajectories are followed through the collector fields (guiding-center or full-orbit), the energy spectrum of the escaping products is computed from the plasma distribution, and the collection efficiency is integrated over that spectrum. The space-charge limit on current sets a practical design constraint.
Burner relevance
The Kronos burner is a D-3He tandem-mirror generator whose reaction produces mostly charged products (a proton and an alpha) with only a small neutron fraction (5.44 percent). The open-ended mirror geometry naturally directs escaping charged particles into end-region direct converters, so direct energy conversion is central to its design concept. It is a design and simulation study.