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The paper generalizes the results of plasma heating experiments in the FT-2 tokamak. It is shown that the generation of fast ions is associated not with the region of linear transformation, nLH, but with the parametric decay region, nd ≃ (0.3-0.5)nLH. In the narrow zone nd, strongly slowed down waves were observed (by a method relying on enhanced scattering of microwave radiation) at a frequency of about 0.7f0 (where f0 is the frequency of the heating radiation); these waves had a narrow spectrum with a width of a few megahertz. As the plasma density increases, the decay region is shifted towards the edge, but it remains ‘attached’, for all practical purposes, to one local density. This process helps to explain the central heating of the main ion component, the generation of fast ions at the edge, and the switching off of the interaction between the lower hybrid wave and the electrons, which stops current drive.

An effective electron and ion heating by LH waves was obtained in the FT-2 tokamak (η = 10 × 10 13 eV cm −3 kW −1 ). It was observed in a narrow density range close to the current drive cut-off density. A transition from the parametric to the classical mechanism may take place during a single pulse. The electron temperature appears to be the main 'hidden' parameter determining the heating.