Quasilinear modification of the spectra of cyclotron emission from a toroidal plasma near the ECRH frequency

A study is made of the modification of the spectra of electron cyclotron emission from an ECR heated plasma in a toroidal magnetic confinement system into which the heating radiation is launched from the low-field side. It is shown that, at frequencies close to the heating frequency, cyclotron emission can become more intense because of the deformation of the distribution function of the resonant electrons. This effect can be used to diagnose the slightly pronounced quasilinear perturbations of the electron distribution in the thermal energy range, which are typical of experiments on ECR plasma heating. Results of a qualitative analysis carried out for model electron distribution functions are presented, and examples of three-dimensional numerical simulations of a circular tokamak are described