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The processes are studied of energy accumulation and dissipation in hot plasma created and confined in the toroidal magnetic trap L-2M stellarator. The distinctive features are studied of the plasma transition to the stationary stage of energy confinement. In the initial stage of the discharge, initiated by microwave pulse in the regime of electron cyclotron resonance plasma heating (ECR heating), plasma energy first sharply increases during the first millisecond from the beginning of microwave heating pulse, and then a fast (~100 μs) increase in plasma energy loss occurs, which recorded using the diamagnetic diagnostics. These processes result in termination of energy accumulation in the confined plasma. It is shown that at the constant microwave heating power of 400 kW, the properties of this process considerably differ for different electron densities. It is ascertained that this process is primarily associated with the processes occurring in the edge plasma region, in which there is a layer of stochastic magnetic surfaces located near the boundary of the plasma column. It is discussed whether the instabilities arising in the stochastic layer, as well as the plasma–wall interaction near the plasma boundary, can affect this process. [ABSTRACT FROM AUTHOR]

Results of measuring longitudinal electric current excited in the toroidal plasma of the L-2M stellarator as a result of high-power pulsed microwave heating (power of up to 600 kW, pulse duration of up to 20 ms) are presented. Microwave radiation generated by gyrotrons and at frequency of 75 GHz, the second harmonic of the electron cyclotron resonance for magnetic field with induction B = 1.34 T in the plasma-column center, was used in the experiments for creation and heating of plasma in the stellarator. Diagnostic systems of the stellarator designed for detection of changes in transverse and poloidal magnetic fields with time were used for measuring currents in plasma. It is demonstrated that the presence of ohmic-heating iron transformer in stellarator construction substantially affects the temporal dynamics of equilibrium currents due to considerable inductance of the toroidal plasma column. The magnitude of the current excited in plasma can be as high as 7 kA upon compensation of inductance of these devices. [ABSTRACT FROM AUTHOR]