High frequency plasma heating in Tokamaks within the Alfven frequency range

The present paper deals with investigations on HF fields generated by an external helical circuit within the Alfven frequency range (OMEGA<ωsub(Bi)) and absorbed in a plasma cylinder with a constant magnetic field. The investigations are performed using the dielectric constant tensor. Stationary distributions of HF field amplitudes are found from the radius with parabolically distributed densities. It is shown that in the vicinity of a local Alfven resonance r=rsub(e) (rsub(e) is the radius with the condition OMEGA=ksub(z)csub(A)met). The HF field generated by the circuit is converted into a short wavelength Alfven mode and a fast magnetic sound wave field. Resonant conditions are defined for which the short wavelength Alfven mode amplitudes reaches the maximum, and can exceed the vacuum field amplitude by one order of magnitude. The power absorbed is estimated for plasma parameters close to the thermonuclear values intended to meet the conditions in tokamak-type machines. Plasma heating up to thermonuclear parameters is ensured by absorption of the short wavelength Alfven mode as a result of Landau electron damping for HF field amplitudes of Hphi approximately equal to 100 Oe at the plasma boundary during approximately 20 ms