Production and heating of a current-free plasma by an extraordinary wave in the L-2 stellarator

Experiments carried out on the production and heating of a current-free plasma by an extraordinary wave in the L-2 stellarator are reported. For an extraordinary wave with a power 100 kW in a pulse 7--9 ms long, it is possible to ionize the gas and to produce a plasma with T/sub e/approx. =500--550 eV, T/sub i/ = 60 eV, n-bar/sub e/ = (6--8) x 10/sup 12/ cm/sup -3/, and an energy approx.80 J. Under these conditions, up to 40 kW of the microwave radiation is absorbed in the central plasma. An efficient absorption of the extraordinary wave and plasma heating occur only if the electron density increases smoothly during the microwave pulse. The results of a numerical calculation of the single-pass absorption of microwave power and the results of calculations of the local thermal conductivity agree well with experimental data.