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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.

PΩ=ηj2
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 I.
PΩ=VI

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