Laboratory experiment on lithium chemistry and its application to effective wall conditioning

Laboratory studies on the physical chemistry of lithium wall conditioning e ffects observed in fusion reactors are reported, focusing on a role of lith ium in dramatic decrease in carbon impurities in TFTR. Auger depth analysis of lithium-deposited graphite shows deep intercalation of lithium into gra phite at room temperature. Helium ion bombardment (150-200 eV) on the lithi um-saturated graphite leads to preferential sputtering of lithium and reduc tion of the net sputtering yield of carbon by an order of magnitude. Finall y, general precautions to achieve reproducible lithium effects in fusion ma chines are described. (C) 1999 Elsevier Science B.V. All rights reserved.