Recovery of the Electron Energy Distribution Function under Conditions of High-Power ECR Plasma Heating at the L-2M Stellarator

The electron energy distribution functions that form in the plasma heating region were recovered from data on the soft X-ray spectra in the energy range of 2−20 keV. The spectra were measured at the L-2M stellarator in the regime of electron cyclotron resonance (ECR) heating in two experiments: on the axial ECR heating (the heating power was PECRH = 250 kW, the electron density was ne = 1.9 × 1019 m–3, and the electron temperature was Te = 0.74 keV) and the off-axial ECR heating (PECRH = 350 kW, ne = 2.5 × 1019 m–3, and Te = 0.7 keV). It was shown that in both experiments the electron energy distribution functions are not Maxwellian and that considerable ensembles of suprathermal electrons form in the heating regions.