Non-resonance plasma heating by radiation in the millimetre range in toroidal devices

The paper presents a new method of RF plasma heating by an extraordinary wave in toroidal devices. The method combines localization of absorption at the centre of the plasma column with a marked decrease in pumping frequency compared with cyclotron frequency. A stationary distribution of the electro-magnetic radiation as result of multiple reflections from the chamber walls is found. It is shown that, compared with linear systems, the threshold for the parametric instability decreases because of the return of oscillations to the pumping region after a circumference of the torus. The effective collision frequency, describing pump-wave conversion into plasma waves, is determined in the framework of the weak turbulence theory. Heating estimates for L-2, T-10, Alcator C and T-15 show the efficiency of the proposed method. (author)