Comparison of Plasma Heating at First and Second Electron Cyclotron Harmonics in the T-10 Tokamak

Abstract

In the T-10 tokamak, the results of plasma heating at the first and second electron cyclotron (EC) harmonics differ substantially. However, the problem is multi-parametric, so it is impossible to estimate the heating quality by sight. In this work, the analysis of heating at both harmonics is provided with two transport models, which were constructed separately for simulation in each mode. For the heating on the second harmonic, we solve the inverse problem of determining the profile of the absorbed power from the experimental electron temperature profile. In this mode, we are able to determine both the deposited power profile and the ratio of absorbed to deposited power. It is shown that at low plasma densities, this ratio is small, which, apparently, is a consequence of the low absorption of the heating waves during their single pass though the plasma. During the heating at the second harmonic, the absorbed power profile is much flatter than predicted by ray tracing calculations of EC waves. Multi-pass wave absorption with random reflections from the corrugated chamber wall leads to such absorption profiles. At high plasma densities, the absorbed power is close to the input power. However, in this case, the results at the second harmonic are worse than the results obtained at the first harmonic due to the flatter absorbed density profile.