ANALYSIS OF ELECTRON-CYCLOTRON EMISSION BY LOWER-HYBRID CURRENT DRIVEPLASMAS

Electron cyclotron emission may be used for diagnosing non-thermal ele ctron distribution functions generated by radio-frequency current driv e. Our attention is concentrated in the X-mode-downshifted second-harm onic range of frequencies, by inspecting at the radiation collected in the horizontal low-magnetic-field side of a tokamak. The cut-off pres ence eliminates the thermal first-harmonic emission and the non-therma l one may be observed without other inference. The electron distributi on function is modelled by a suitable sum of drifting Maxwellians for reproducing the flat tails usually obtained in the presence of lower-h ybrid power injection. This model is time saving as far as the compute r simulations are concerned and permits a lot of runs in order to acco mplish a wide parameters exploitation. A sensitivity analysis of ECE i ntensity is performed with respect to the main moments of the suprathe rmal electrons distribution function. The analysis shows that the radi ation spectra are very sensitive to the perpendicular energy and to th e number of fast electrons, while only a weak dependence on the parall el energy is found.