Measurements of Microwave Power Absorbed during ECR Plasma Heating at the L-2M Stellarator

The results are presented from measurements of the power absorbed in plasma of the L-2M stellarator in experiments on the electron cyclotron resonance (ECR) plasma heating at the second harmonic of the gyrofrequency. Hydrogen plasma was created and heated in the stellarator vacuum chamber as a result of the resonance absorption of microwave power supplied by the gyrotrons in the pulse-periodic operation regime. The total energy of the toroidal plasma column and the absorbed power were measured using the diamagnetic diagnostics. The shielding effect of the metal vacuum chamber on the diamagnetic signal measurements was taken into account. It was ascertained that, during the axial ECR heating, up to 90% of the inputted gyrotron power is absorbed in the plasma that is consistent with the theoretical estimates.