Possibility of steady-state thermonuclear reaction in a tokamak

A self-sustained thermonuclear D--T reaction can occur in the steady state (or in a quasisteady state) in a toroidal device of the tokamak type if the plasma radius is sufficiently large. The steady-state plasma temperature can be extremely high. For example, in a plasma of radius a=100--200 cm, with neoclassical transport, the temperature at the central part of the plasma is approx.70 keV in the steady state. The steady-state temperature distribution is reached spontaneously as the result of the onset of a thermal thermonuclear instability if the plasma is first heated to a temperature of the order of 10 keV. Steady-state thermonuclear combustion can also occur at a lower temperature if the energy balance of the plasma is controlled.