INITIAL CONDITIONING OF THE VESSEL WALL AND THE GRAPHITE LIMITERS IN DIII-D

The Doublet III tokamak has been rebuilt as the DIII-D, to accommodate large cross-section (a equals 0. 67 m), highly elongated (b/a greater than equivalent to 2) plasmas with either a dee-shaped limiter configuration or a single null, poloidal divertor. The new vacuum vessel has been conditioned by a combination of 400 degree C baking, Taylor pulsed discharge cleaning (TDC), and rf-assisted glow cleaning (RGC). Tokamak operation began in February 1986 with the attainment of an 0. 5 MA discharge on the first day plasmas were attempted. Rapid achievement of high current (I greater than equivalent to 2. 0 MA) tokamak discharges in the DIII-D device underscores the importance of high temperature bakeout in shortening the initial cleanup period for a vessel with large amounts of graphite armor.