| Autor: |
T Abrams, J G Guterl, S Abe, D C Donovan, I Bykov, C A Johnson, J H Nichols, J D Elder, D A Ennis, S D Loch, D L Rudakov, G Sinclair, C H Skinner, P C Stangeby, D M Thomas, E A Unterberg, W R Wampler |
| Jazyk: |
angličtina |
| Rok vydání: |
2023 |
| Předmět: |
|
| Zdroj: |
Materials Research Express, Vol 10, Iss 12, p 126503 (2023) |
| Druh dokumentu: |
article |
| ISSN: |
2053-1591 |
| DOI: |
10.1088/2053-1591/ad0f43 |
| Popis: |
Fundamental mechanisms governing the erosion and prompt re-deposition of tungsten impurities in tokamak divertors are identified and analyzed to inform the lifetime of tungsten plasma-facing components in ITER and other future devices. Various experiments conducted at DIII-D to benchmark predictive models are presented, leveraging the DiMES removable sample exposure probe capability and the Metal Rings Campaign, in which toroidally symmetric rows of tungsten-coated tiles were installed in the DIII-D divertor. In tokamak divertors, the width of the electric sheath is of the order of the main ion Larmor radius, and a vast majority of sputtered tungsten impurities are typically ionized within the sheath. Therefore, W prompt redeposition is mainly governed by the ratio of the characteristic ionization mean-free path of neutral tungsten to the width of the sheath. In-situ monitoring of the prompt redeposition of tungsten impurities in divertors is demonstrated via the use of WII/WI line ratios and the ionizations/photon (S/XB) method in L-mode discharges. Even with this relatively limited set of emission measurements, net erosion measurements were found to be a consistent upper bound to an analytic scaling based on the ratio of the W ionization length, ${\lambda }_{{iz}},$ and the width of the magnetic sheath rather than the ratio of ${\lambda }_{{iz}}$ and the W ^+ gyro-radius. In the far-scrape-off layer (SOL) of the ITER divertor, however, it is calculated that the measurement of photon emissions associated with the ionization of tungsten impurities up to ${{\rm{W}}}^{5+}$ may be required. Finally, W deposition patterns on DiMES collector probes, interpreted via DIVIMP-WallDYN modelling, reveal the key roles of progressive W erosion/re-deposition staps and E × B drifts in regulating long-range high-Z material migration. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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