THE EXPERIENCE WITH JETS COMBINED DC RF GLOW-DISCHARGE CLEANING (GDC)SYSTEM/

The JET Tokamak was fitted with four new electrodes of novel design, e ach powered from individual computer controlled dc and RF supplies. De tails of enhancements and problems from 15 months experience with the system are outlined. Experiments were performed to assess the effect o f RF on the glow discharge characteristics, and to establish stable gl ow at low pressure and high voltage. JET combined RF/dc glow discharge cleaning (GDC) had no significant advantages over pure dc GDC, provid ed highly stable dc current control was obtained. In fact, the mechani cally weak electrode inductor spiral required to allow RF posed a dist inct disadvantage. The electrodes were converted to simple plates, fol lowing damage caused by halo currents during Tokamak plasma disruption s. The performance of these electrodes was assessed. Future developmen ts in the JET GDC system are outlined. Copyright (C) 1996 Elsevier Sci ence Ltd.