Effect of lithium wall conditioning on deuterium in-vessel retention in the TdeV tokamak

Abstract

The effect of lithium wall conditioning in a boronized tokamak was investigated in ohmic discharges in the TdeV. In the course of 14 discharges, lithium was spread on the walls to a coverage of about 10 21 atoms/m 2 by inserting a lithium-containing graphite crucible in the scrape-off-layer. Lithium caused an increase of some tens of percent in the wall pumping capacity during discharges, as seen from gas puffing and H α + D α measurements. Post-shot wall outgassing also increased such that the short term in-vessel retention was only enhanced by about 20%. This increased retention level was confirmed by subsequent analysis of collector probe samples positioned in the SOL near the wall and was lower than one H or D atom per Li atom. Evidence of oxygen gettering by lithium was also found.