Deposition of deuterium and metals on divertor tiles in the DIII--D tokamak
- Idaho State University, Pocatello, Idaho 83209-8106 (United States)
- Sandia National Laboratories, Albuquerque, New Mexico 87185-5800 (United States)
- General Atomics, P. O. Box 85608, San Diego, California 92186-9784 (United States)
Hydrogen recycling and impurity influx are important issues in obtaining high confinement discharges in the DIII--D tokamak. To reduce metallic impurities in DIII--D, 40% of the wall area, including the highest heat flux zones, have been covered with graphite tiles. However, erosion, redeposition, and hydrogen retention in the tiles, as well as metal transport from the remaining Inconel walls, can lead to enhanced recycling and impurity influx. Hydrogen and metal retention in divertor floor tiles have been measured using external ion beam analysis techniques following four campaigns where tiles were exposed to several thousand tokamak discharges. The areal density of deuterium retained following exposure to tokamak plasmas was measured with external nuclear reaction analysis. External proton-induced x-ray emission analysis was used to measure the areal densities of metallic impurities deposited upon the divertor tiles either by sputtering of metallic components during discharges or as contamination during tile fabrication. Measurements for both deuterium and metallic impurities were taken on both the tile surfaces which face the operating plasma and the surfaces on the sides of the tiles which form the small gaps separating each of the tiles in the divertor. The highest areal densities of both deuterium (from 2 to 8 {times} 10{sup 18} atoms/cm{sup 2}) and metals (from 0.2 to 1 {times} 10{sup 18} atoms/cm{sup 2}) were found on the plasma-facing surface near the inner strike point region of each set of divertor tiles. Significant deposits, extending as far as 1 cm from the plasma-facing surface and containing up to 40% of the total divertor deposition, were also observed on the gap-forming surfaces of the tiles.
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 7284886
- Journal Information:
- Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (United States), Journal Name: Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (United States) Vol. 10:4; ISSN JVTAD; ISSN 0734-2101
- Country of Publication:
- United States
- Language:
- English
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Deposition of deuterium and metals on divertor tiles in the DIII-D tokamak
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