Longitudinal electric fields in the OH and ECRH heating modes of the L-2M stellarator

Abstract

The soft X-ray spectra were measured at the L-2M stellarator in the OH and ECRH modes, which occurred to be considerably non-Maxwellian. In the OH mode, the SXR spectra considerably deviate not only from the Maxwellian spectrum, but also from the model bremsstrahlung spectrum of plasma in the longitudinal electric field. This can be due to the fact that, under ohmic heating conditions, plasma waves can be excited and absorbed by plasma electrons. In the OH mode, the radial distribution of the longitudinal electric field was determined, which turned to be almost uniform over the radius. It was hypothesized that, in the ECRH experiments, the deviations of the measured SXR spectra from the Maxwellian spectrum are also caused by the presence of the longitudinal electric fields in plasma. These fields are the longitudinal vortex electric fields generated in plasma during the current drive.