Quasi-linear evolution of electron cyclotron absorption by an RF-generated extended tail in tokamak plasmas

The authors employ quasi-linear theory to study the time evolution of the absorption coefficient for extraordinary mode electron cyclotron waves by an extended electron tail in momentum space, in a magnetized plasma under the action of externally launched lower hybrid and electron cyclotron waves. They use lower hybrid waves to generate the extended tail and then introduce electron cyclotron waves interacting with the tail electrons. Their results show that the absorption coefficient for the central ray of the spectrum of cyclotron waves increases with the width of the spectrum and also show that the asymptotic absorption coefficient may be larger than the value at the onset of electron cyclotron waves, for sufficiently large angle of injection relative to the normal to the magnetic field.