EFFECT OF LITHIUM WALL CONDITIONING ON DEUTERIUM IN-VESSEL RETENTION IN THE TDEV TOKAMAK

The effect of lithium wall conditioning in a boronized tokamak was inv estigated in ohmic discharges in the TdeV. In the course of 14 dischar ges, lithium was spread on the walls to a coverage of about 10(21) ato ms/m(2) by inserting a lithium-containing graphite crucible in the scr ape-off-layer. Lithium caused an increase of some tens of percent in t he wall pumping capacity during discharges, as seen from gas puffing a nd H-alpha + D-alpha measurements. Post-shot wall outgassing also incr eased such that the short term in-vessel retention was only enhanced b y about 20%. This increased retention level was confirmed by subsequen t analysis of collector probe samples positioned in the SOL near the w all and was lower than one H or D atom per Li atom. Evidence of oxygen gettering by lithium was also found.