Direct conversion of fusion energy

Deuterium and tritium are expected to be used as fuel in the first fusion reactors. Energy is released as kinetic energy of ions and neutrons, when deuterium reacts with tritium. One way to convert the kinetic energy to electrical energy, is to let the ions and neutrons hit the reactor wall and convert the heat that is caused by the particle bombardment to electrical energy with ordinary thermal conversion. If the kinetic energy of the ions instead is converted directly to electrical energy, a higher efficiency of the energy conversion is possible. The majority of the fusion energy is released as kinetic energy of neutrons, when deuterium reacts with tritium. Fusion reactions such as the D-D reactions, the D-3He reaction and the p-11B reaction, where a larger part of the fusion energy becomes kinetic energy of charged particles, appears therefore more suitable for direct conversion. Since they have lower reactivity than the D-T reaction, they need a larger βB20 to give sufficiently high fusion power density. Because of this, the fusion configurations spherical torus (ST) and field-reversed configuration (FRC), where high β values are possible, appear interesting. Rosenbluth and Hinton come to the conclusion that efficient direct conversion isn't possible in closed field line systems and that open geometries, which facilitate direct conversion, provide inadequate confinement for D-3He. It is confirmed in this study that it doesn't seem possible to achieve as high direct conversion efficiency in closed systems as in open systems. ST and FRC fusion power plants that utilize direct conversion seem however interesting. Calculations with the help of Maple indicate that the reactor parameters needed for a D-D ST and a D3 He ST hopefully are possible to achieve. The best energy conversion option for a D-D or D3 He ST appears to be direct electrodynamic conversion (DEC) together with ordinary thermal conversion or liquid metal MHD conversion (LMMHD). For a D-T ST, LMMHD seems suitable. The FRC is suitable for application of direct energy converters, since an FRC plasma is surrounded by open magnetic field lines. Venetian-blind (VB) collectors and traveling wave direct energy converters can give a high energy conversion efficiency. Reactor studies indicate that the COE may become lower for a D-3He FRC than for a D-T tokamak