Academic Journal
Helium plasma operations on ASDEX Upgrade and JET in support of the non-nuclear phases of ITER
| Title: | Helium plasma operations on ASDEX Upgrade and JET in support of the non-nuclear phases of ITER |
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| Authors: | A. Hakola, M. Balden, M. Baruzzo, R. Bisson, S. Brezinsek, T. Dittmar, D. Douai, M. Dunne, L. Garzotti, M. Groth, R. Henriques, L. Horvath, I. Jepu, E. Joffrin, A. Kappatou, D. Keeling, K. Krieger, B. Labit, M. Lennholm, J. Likonen, A. Loarte, P. Lomas, C. Lowry, M. Maslov, D. Matveev, R.A. Pitts, U. Plank, M. Rasinski, D. Ryan, S. Saarelma, S. Silburn, E.R. Solano, W. Suttrop, T. Tala, E. Tsitrone, N. Vianello, T. Wauters, A. Widdowson, M. Wischmeier, the EUROfusion Tokamak Exploitation Team, the ASDEX Upgrade Team, JET Contributors |
| Source: | Nuclear Fusion, Vol 64, Iss 9, p 096022 (2024) |
| Publisher Information: | IOP Publishing, 2024. |
| Publication Year: | 2024 |
| Collection: | LCC:Nuclear and particle physics. Atomic energy. Radioactivity |
| Subject Terms: | helium plasma, H-mode, tungsten fuzz, erosion, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798 |
| More Details: | For its initial operational phase, ITER has until recently considered using non-nuclear hydrogen (H) or helium (He) plasmas to keep nuclear activation at low levels. To this end, the Tokamak Exploitation Task Force of the EUROfusion Consortium carried out dedicated experimental campaigns in He on the ASDEX Upgrade (AUG) and JET tokamaks in 2022, with particular emphasis put on the ELMy H-mode operation and plasma-wall interaction processes as well as comparison to H or deuterium (D) plasmas. Both in pure He and mixed He + H plasmas, H-mode operation could be reached but more effort was needed to obtain a stable plasma scenario than in H or D. Even if the power threshold for the LH transition was lower in He, entering the type-I ELMy regime appeared to require equally much or even more heating power than in H. Suppression of ELMs by resonant magnetic perturbations was studied on AUG but was only possible in plasmas with a He content below 19%; the reason for this unexpected behaviour remains still unclear and various theoretical approaches are being pursued to properly understand the physics behind ELM suppression. The erosion rates of tungsten (W) plasma-facing components were an order of magnitude larger than what has been reported in hydrogenic plasmas, which can be attributed to the prominent role of He ^2+ ions in the plasma. For the first time, the formation of nanoscale structures (W fuzz) was unambiguously demonstrated in H-mode He plasmas on AUG. However, no direct evidence of fuzz creation on JET was obtained despite the main conditions for its occurrence being met. The reason could be a delicate balance between W erosion by ELMs, competition between the growth and annealing of the fuzz, and coverage of the surface with co-deposits. |
| Document Type: | article |
| File Description: | electronic resource |
| Language: | English |
| ISSN: | 1741-4326 0029-5515 |
| Relation: | https://doaj.org/toc/0029-5515 |
| DOI: | 10.1088/1741-4326/ad6335 |
| Access URL: | https://doaj.org/article/4399fbe2027b47249df40bd7c5674540 |
| Accession Number: | edsdoj.4399fbe2027b47249df40bd7c5674540 |
| Database: | Directory of Open Access Journals |
| ISSN: | 17414326 00295515 |
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| DOI: | 10.1088/1741-4326/ad6335 |
| Published in: | Nuclear Fusion |
| Language: | English |