Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X
Abstract Experimental evidence of parametric decay instability (PDI) is observed in the Wendelstein 7-X stellarator, when high-power microwave beams cross a stationary magnetic island at the plasma edge. Here, trapping and build-up of upper hybrid waves within a density bump (measured within the isl...
Published in: | Plasma Physics and Controlled Fusion |
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Online Access: | http://dx.doi.org/10.1088/1361-6587/aca121 https://iopscience.iop.org/article/10.1088/1361-6587/aca121 https://iopscience.iop.org/article/10.1088/1361-6587/aca121/pdf |
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crioppubl:10.1088/1361-6587/aca121 2024-09-15T18:04:24+00:00 Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X Tancetti, A Nielsen, S K Rasmussen, J Moseev, D Stange, T Marsen, S Vecséi, M Killer, C Wurden, G A Jensen, T Stejner, M Anda, G Dunai, D Zoletnik, S Rahbarnia, K Brandt, C Thomsen, H Hirsch, M Hoefel, U Chaudhary, N Winters, V Kornejew, P Harris, J Laqua, H P EUROfusion enabling research grant Villum Fonden Euratom Research and Training Programme 2022 http://dx.doi.org/10.1088/1361-6587/aca121 https://iopscience.iop.org/article/10.1088/1361-6587/aca121 https://iopscience.iop.org/article/10.1088/1361-6587/aca121/pdf unknown IOP Publishing https://iopscience.iop.org/page/copyright https://iopscience.iop.org/info/page/text-and-data-mining Plasma Physics and Controlled Fusion volume 65, issue 1, page 015001 ISSN 0741-3335 1361-6587 journal-article 2022 crioppubl https://doi.org/10.1088/1361-6587/aca121 2024-08-12T04:14:33Z Abstract Experimental evidence of parametric decay instability (PDI) is observed in the Wendelstein 7-X stellarator, when high-power microwave beams cross a stationary magnetic island at the plasma edge. Here, trapping and build-up of upper hybrid waves within a density bump (measured within the island by alkali beam emission spectroscopy) is responsible for the reduction of the instability power threshold below the maximum gyrotron power. In this paper, we provide the first experimental evidence of the connection between the trapping mechanism in the island density bump and excitation of PDI-related signals. We show correlations of periodic crashes in the PDI-related signals with quasi-continuous fluctuations at the plasma edge, which, additionally, cause a flattening of the density profile in the island. We demonstrate that flattening of the experimental density profiles can suppress the trapping mechanism and inhibit the low-threshold PDI. PDI on the edge island could alter the power deposition profile and reduce the efficiency of the electron cyclotron resonance heating system, simultaneously posing a serious threat to the optimal operation of microwave-based diagnostics and plasma-facing components. Article in Journal/Newspaper Edge Island Magnetic Island IOP Publishing Plasma Physics and Controlled Fusion 65 1 015001 |
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Abstract Experimental evidence of parametric decay instability (PDI) is observed in the Wendelstein 7-X stellarator, when high-power microwave beams cross a stationary magnetic island at the plasma edge. Here, trapping and build-up of upper hybrid waves within a density bump (measured within the island by alkali beam emission spectroscopy) is responsible for the reduction of the instability power threshold below the maximum gyrotron power. In this paper, we provide the first experimental evidence of the connection between the trapping mechanism in the island density bump and excitation of PDI-related signals. We show correlations of periodic crashes in the PDI-related signals with quasi-continuous fluctuations at the plasma edge, which, additionally, cause a flattening of the density profile in the island. We demonstrate that flattening of the experimental density profiles can suppress the trapping mechanism and inhibit the low-threshold PDI. PDI on the edge island could alter the power deposition profile and reduce the efficiency of the electron cyclotron resonance heating system, simultaneously posing a serious threat to the optimal operation of microwave-based diagnostics and plasma-facing components. |
author2 |
EUROfusion enabling research grant Villum Fonden Euratom Research and Training Programme |
format |
Article in Journal/Newspaper |
author |
Tancetti, A Nielsen, S K Rasmussen, J Moseev, D Stange, T Marsen, S Vecséi, M Killer, C Wurden, G A Jensen, T Stejner, M Anda, G Dunai, D Zoletnik, S Rahbarnia, K Brandt, C Thomsen, H Hirsch, M Hoefel, U Chaudhary, N Winters, V Kornejew, P Harris, J Laqua, H P |
spellingShingle |
Tancetti, A Nielsen, S K Rasmussen, J Moseev, D Stange, T Marsen, S Vecséi, M Killer, C Wurden, G A Jensen, T Stejner, M Anda, G Dunai, D Zoletnik, S Rahbarnia, K Brandt, C Thomsen, H Hirsch, M Hoefel, U Chaudhary, N Winters, V Kornejew, P Harris, J Laqua, H P Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X |
author_facet |
Tancetti, A Nielsen, S K Rasmussen, J Moseev, D Stange, T Marsen, S Vecséi, M Killer, C Wurden, G A Jensen, T Stejner, M Anda, G Dunai, D Zoletnik, S Rahbarnia, K Brandt, C Thomsen, H Hirsch, M Hoefel, U Chaudhary, N Winters, V Kornejew, P Harris, J Laqua, H P |
author_sort |
Tancetti, A |
title |
Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X |
title_short |
Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X |
title_full |
Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X |
title_fullStr |
Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X |
title_full_unstemmed |
Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X |
title_sort |
inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of wendelstein 7-x |
publisher |
IOP Publishing |
publishDate |
2022 |
url |
http://dx.doi.org/10.1088/1361-6587/aca121 https://iopscience.iop.org/article/10.1088/1361-6587/aca121 https://iopscience.iop.org/article/10.1088/1361-6587/aca121/pdf |
genre |
Edge Island Magnetic Island |
genre_facet |
Edge Island Magnetic Island |
op_source |
Plasma Physics and Controlled Fusion volume 65, issue 1, page 015001 ISSN 0741-3335 1361-6587 |
op_rights |
https://iopscience.iop.org/page/copyright https://iopscience.iop.org/info/page/text-and-data-mining |
op_doi |
https://doi.org/10.1088/1361-6587/aca121 |
container_title |
Plasma Physics and Controlled Fusion |
container_volume |
65 |
container_issue |
1 |
container_start_page |
015001 |
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1810441901949583360 |