Effect of vacuum chamber boronization on the plasma parameters in the L-2M stellarator

After boronization of the vacuum chamber of the L-2M stellarator, radiative losses from ohmically and ECR heated plasmas were reduced by a factor of 3-4. Under these conditions, radiative losses in the ECRH regime comprise only 10-15% of the input microwave power. Some effects have been detected that were not observed previously: a substantial increase in the gradient of the electron temperature near the separatrix, a preferentially outward-directed radial turbulent particle flux (both throughout the discharge phase and from shot to shot), and a longer (by a factor of 2-3) duration of the plasma cooling phase. (c) 2005 Pleiades Publishing, Inc.