Spontaneous and Induced Transient Processes in Plasma of the L-2M Stellarator in High-Power ECR Heating Regime

Comparative analysis of time evolutions of plasma macro- and microparameters during spontaneous and induced transient processes in the classical quasi-stationary stellarator L-2M is presented. Plasma heating was performed in the electron cyclotron resonance heating (ECRH) regime at the second harmonic of electron gyrofrequency under conditions of high specific energy input in the power range of 0.8−2 MW/m³. Spontaneous transient processes are observed at constant heating powers, and induced ones are initiated by a stepwise increase or decrease in heating power. Correlation between time evolutions of plasma macroparameters (primarily the energy lifetime) and the parameters of plasma turbulence is searched. Physical models of the phenomena that determine dynamic changes in plasma macroparameters are presented. Analysis of the data of high-frequency diagnostics made it possible to clear up the action of MHD and kinetic instabilities on transient processes in the stellarator hot plasma, as well as the role of plasma-wall interaction.