Method of heating a plasma.
In a tokamak, ohmic heating is used in the initial phase of a plasma discharge in order to raise the temperature a little before neutral beam heating or RF heating is applied.
A toroidal current produces a magnetic field which serves both to keep the plasma in magnetic equilibrium and to provide ohmic heating.
The ohmic heating density PΩ is related to the plasma resistivity η and the current density j.
As the temperature
of the plasma
increases, the resistivity drops (η~Te-3/2
). Thus, ohmic heating is ineffective at high plasma temperatures.More simply the ohmic heating power may be expressed in terms of the voltage
Vand the total plasma current