Characteristic Features of the Behavior of Ecrh-Produced - and Low-Density Plasmas in the L-2M Stellarator

Results are presented from experimental studies of the behavior of plasmas with moderate (n_e≤ 3 × 10¹⁹ m^-3) down to low (n_e = 0.3 × 10¹⁹ m^-3) densities produced and heated by microwaves (f = 75 GHz) with power P≤ 400 kW It is shown that, as the plasma density is reduced, the plasma emission spectrum is modified. In spite of the fact that the second harmonic emission from the plasma increases in this case, the plasma energy measured by the diamagnetic diagnostics does not increase. This casts doubts on the correctness of ECE measurements of the plasma temperature under these conditions. The formation of an internal transport barrier was not observed in the available magnetic-field structure of L-2M.