Electron cyclotron wave absorption by the fast tail generated by the dc electric field in tokamak plasmas

Wave damping near the electron gyrofrequency in a Tokamak plasma with the energetic tail generated by the d.c. electric field is investigated. The electron tail is computed by a Fokker-Planck initial value code as a function of the relevant parameter Esub(parallel)/Esub(c)=Esub(parallel)Tsub(e)/(2πnsub(e)e3Λ). It is shown that strong damping of the e-mode occurs for oblique propagation. The results are of relevance for studies of ECRH in present-day Tokamaks and in future reactors where a mildly relativistic electron tail is naturally present for large Tsub(e). Special emphasis is therefore given to wave absorption for frequencies f significantly below the central electron gyrofrequency, and to the associated r.f.-driven current. (author)