A comparison of hydrogen vs. helium glow discharge effects on fusion device first-wall conditioning

Conference · Fri Sep 01 04:00:00 EDT 1989

OSTI ID:5723021

Dylla, H F

Hydrogen- and deuterium-fueled glow discharges are used for the initial conditioning of magnetic fusion device vacuum vessels following evacuation from atmospheric pressure. Hydrogenic glow discharge conditioning (GDC) significantly reduces the near-surface concentration of simple adsorbates, such as H/sub 2/O, CO, and CH/sub 4/, and lowers ion-induced desorption coefficients by typically three orders of magnitude. The time evolution of the residual gas production observed during hydrogen-glow discharge conditioning of the carbon first-wall structure of the TFTR device is similar to the time evolution observed during hydrogen GDC of the initial first-wall configuration in TFTR, which was primarily stainless steel. Recently, helium GDC has been investigated for several wall-conditioning tasks on a number of tokamaks including TFTR. Helium GDC shows negligible impurity removal with stainless steel walls. For impurity conditioning with carbon walls, helium GDC shows significant desorption of H/sub 2/O, CO, and CO/sub 2/; however, the total desorption yield is limited to the monolayer range. In addition, helium GDC can be used to displace hydrogen isotopes from the near-surface region of carbon first-walls in order to lower hydrogenic retention and recycling. 38 refs., 6 figs.

• Research Organization: Princeton Univ., NJ (USA). Plasma Physics Lab.
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 5723021
• Report Number(s): PPPL-2642; CONF-8904230-4; ON: DE89016954
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700209* -- Fusion Power Plant Technology-- Component Development & Materials Testing
CARBON
CONTAINERS
ELECTRIC DISCHARGES
ELEMENTAL MINERALS
ELEMENTS
FIRST WALL
FLUIDS
GASES
GLOW DISCHARGES
GRAPHITE
HELIUM
HYDROGEN ISOTOPES
IMPURITIES
ISOTOPES
MINERALS
NONMETALS
PRESSURE VESSELS
RARE GASES
TFTR TOKAMAK
THERMONUCLEAR REACTOR WALLS
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS