Surface analysis of 1984/1985 Tokamak Fusion Test Reactor limiter tiles
Bare POCO AXF-5Q graphite tiles were installed as the plasma-facing surface of the Tokamak Fusion Test Reactor (TFTR) movable limiter for a series of approx. 2700 high power discharges (600 with up to 6 MW neutral beams). During this operating phase, erosion and deposition processes modified the surface of the limiter. In the regions of the most intense plasma contact, which reached temperatures over 2400/sup 0/C, only small amounts of metallic impurities (<5 x 10/sup 16/ atoms/cm/sup 2/) are observed during subsequent beta backscattering and proton-induced x-ray emission (PIXE) analysis. Also observed in these regions are several small areas of surface crazing, and scattered droplets of metals (approx. 1 mm diam) presumed to originate from melted internal hardware. In regions more removed from direct plasma contact, thicker metallic deposits are observed (approx. 2 x 10/sup 18/ atoms/cm/sup 2/). There are more of these deposits on the side facing the electron drift direction than on the ion drift side. The metallic deposits are composed of approx. 55% Ni, 25% Cr, and 20% Fe and several trace elements. Near-surface retained deuterium levels vary from 10/sup 16/ to 10/sup 18//cm/sup 2/ along one ion-side/electron-side pair of tiles. Deuterium from TFTR operations in the bulk of a tile may have been as much as 5 ppm. Hydrogen in the tile was approx.1 at. %. Surface roughness measured outside the intense plasma contact region is much more than the original POCO AXF-5Q graphite, whereas within the plasma contact region, tile surfaces are somewhat smoother than they were initially. Two of the tiles in high heat flux regions broke during operation. The resulting geometry change led to areas of enhanced erosion and nearby redeposition of carbon.
- Research Organization:
- Sandia National Laboratories, Livermore, California and Albuquerque, New Mexico 87185
- DOE Contract Number:
- AC04-76DP00789; AC02-76CH03073
- OSTI ID:
- 5653479
- Journal Information:
- J. Vac. Sci. Technol., A; (United States), Vol. 4:3
- Country of Publication:
- United States
- Language:
- English
Similar Records
Deposition of deuterium and metals on divertor tiles in the DIII--D tokamak
Hydrogen isotope trapping on graphite collectors during an isotope exchange experiment in the Tokamak Fusion Test Reactor
Related Subjects
LIMITERS
IMPURITIES
TFTR TOKAMAK
CHROMIUM
GRAPHITE
IRON
NICKEL
SURFACES
CARBON
ELEMENTAL MINERALS
ELEMENTS
METALS
MINERALS
NONMETALS
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS
TRANSITION ELEMENTS
700209* - Fusion Power Plant Technology- Component Development & Materials Testing