A model of non-Maxwellian electron distribution for the analysis of ECE in JET discharges
Recent experiments performed in JET at high level of plasma heating, in preparation of, and during the DT campaign have shown significant discrepancies between electron temperature measurements by Thomson Scattering (TS) and Electron Cyclotron Emission (ECE). In order to perform a systematic analysis of this effect, a simple model of bipolar distortion of the electron distribution function has been developed, allowing analytic calculation of the EC emission and absorption coefficients. Extensive comparisons of the modelled ECE spectra at both the 2nd and the 3rd harmonic with experimental measurements provide a compelling confirmation of bulk electron distribution distortions around 1-2 times the electron thermal velocity and prove useful for a first level of analysis of this effect.