In situ silicon and lithium coating and its removal in the HL-1M tokamak

Siliconization and lithium coating of the wall in the HL-1M tokamak were pe rformed by means of DC glow discharges with a mixture of SiH4 and He and li thium evaporation in a He glow discharge, respectively. With the wall condi tioning, impurities and radiation power losses are generally lower than tho se with boronization, and strong wall pumping and low hydrogen recycling oc cur in these tokamak discharges. The excellent wall conditions lead to grea t progresses in such experiments as the multi-shot pellet injection, LHCD a nd long pulse discharges. Removal of these coatings by DC glow discharges w ith H-2 and He was demonstrated. (C) 1999 Elsevier Science B.V. All rights reserved.