Properties of Edge Plasma and Peripheral Transport in Quasi-Stationary L-2 and L-2M Stellarators

Abstract

Studies of plasma produced and confined in quasi-stationary L-2 and L-2M stellarators are presented. In these facilities, plasma was produced by the non-inductive electron cyclotron resonance (ECR) microwave heating in the power range of P = 0.05–1 MW. The radial structure of the near-separatrix region (the relative radius of 0.8–1) and fluctuations of plasma parameters in the mode without changing macroparameters are considered. Fluctuations of the near-wall plasma parameters—density, electric potential, and magnetic field—and their evolution during discharges are analyzed. The structure of the electric field and heat flux in the near-wall plasma measured by Langmuir probes is analyzed. The relation between changes in fluctuating plasma parameters and possible small-scale instabilities is analyzed. The mechanisms of the development of permutation, peeling and temperature gradient edge instabilities are considered. A comparison is made between the simulation of the energy transfer in plasma using neoclassical models taking into account anomalous energy losses and that based on canonical pressure profiles. The possibility of using a quasi-stationary stellarator as a source of plasma flows with three-dimensional geometry for materials science is considered.