End points in discharge cleaning on TFTR (Tokamak Fusion Test Reactor)

Technical Report · Sat Jul 01 04:00:00 EDT 1989

DOI:https://doi.org/10.2172/6025693· OSTI ID:6025693

Mueller, D; Dylla, H F; Bell, M G; Blanchard, W R; Bush, C E; Gettelfinger, G; Hawryluk, R J; Hill, K W; Janos, A C; Jobes, F C

It has been found necessary to perform a series of first-wall conditioning steps prior to successful high power plasma operation in the Tokamak Fusion Test Reactor (TFTR). This series begins with glow discharge cleaning (GDC) and is followed by pulse discharge cleaning (PDC). During machine conditioning, the production of impurities is monitored by a Residual Gas Analyzer (RGA). PDC is made in two distinct modes: Taylor discharge cleaning (TDC), where the plasma current is kept low (15--50 kA) and of short duration (50 ms) by means of a relatively high prefill pressure and aggressive PDC, where lower prefill pressure and higher toroidal field result in higher current (200--400 kA) limited by disruptions at q(a) /approx/ 3 at /approx/ 250 ms. At a constant repetition rate of 12 discharges/minute, the production rate of H/sub 2/O, CO, or other impurities has been found to be an unreliable measure of progress in cleaning. However, the ability to produce aggressive PDC with substantial limiter heating, but without the production of x-rays from runaway electrons, is an indication that TDC is no longer necessary after /approx/ 10/sup 5/ pulses. During aggressive PDC, the uncooled limiters are heated by the plasma from the bakeout temperature of 150/degree/C to about 250/degree/C over a period of three to eight hours. This limiter heating is important to enhance the rate at which H/sub 2/O is removed from the graphite limiter. 14 refs., 3 figs., 1 tab.

• Research Organization: Princeton Univ., NJ (USA). Plasma Physics Lab.
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 6025693
• Report Number(s): PPPL-2633; ON: DE89014335
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700201* -- Fusion Power Plant Technology-- Blanket Engineering
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CLEANING
ELECTRIC DISCHARGES
ELECTRON DENSITY
FIRST WALL
GLOW DISCHARGES
HYDROGEN COMPOUNDS
IMPURITIES
LIMITERS
OXIDES
OXYGEN COMPOUNDS
SURFACE CLEANING
SURFACE FINISHING
TFTR TOKAMAK
THERMONUCLEAR REACTOR WALLS
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS
WATER