Method of heating a plasma in a tokamak. Also known as RF heating.

The ions and electrons which make up a plasma gyrate around the containing magnetic field at the cyclotron frequency. Injecting electromagnetic waves at this frequency will heat the plasma and can also be used to drive current.

The RF waves are generated by a gyrotron and transmited into the plasma by an antenna. The energy is absorbed at a resonant layer within the plasma. There are three main forms of RF heating

Ion Cyclotron Resonance
RF waves are injected at the second harmonic of the ion cycltron frequency (MHz range). A fast magnetosonic wave delivers the energy. A large amount of power can be delivered this way (~10MW).

Lower Hybrid Resonance
Waves injected with frequencies near the geometric mean of ion and electron cyclotron frequencies (a few GHz). In this case, a slow wave transports the wave energy. An effective tool for driving off-axis current.

Electron Cylcotron Resonance
RF waves in the range 100-200 GHz to resonate with the electron gyration. Required development of a new generation of gyrotrons.