Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EAST
Transient heat flux of up to several thousand MW m ^−2 in a short pulse (∼ms) in tokamaks poses great risk to plasma-facing components (PFCs), making it a major concern for ITER. Despite numerous high heat flux tests, analysis of in situ transient heat flux-induced damage to PFCs remains necessary....
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IOP Publishing
2025-01-01
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| Series: | Nuclear Fusion |
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| Online Access: | https://doi.org/10.1088/1741-4326/adc1e0 |
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| author | Chuannan Xuan Dahuan Zhu Yang Wang Binfu Gao Wenxue Fu Zongxiao Guo Rui Ding Baoguo Wang Pengfei Zi Junling Chen the EAST Team |
| author_facet | Chuannan Xuan Dahuan Zhu Yang Wang Binfu Gao Wenxue Fu Zongxiao Guo Rui Ding Baoguo Wang Pengfei Zi Junling Chen the EAST Team |
| author_sort | Chuannan Xuan |
| collection | DOAJ |
| description | Transient heat flux of up to several thousand MW m ^−2 in a short pulse (∼ms) in tokamaks poses great risk to plasma-facing components (PFCs), making it a major concern for ITER. Despite numerous high heat flux tests, analysis of in situ transient heat flux-induced damage to PFCs remains necessary. Such damage, including the melting and cracking of tungsten (W) PFCs, is notably observed on the divertor (dome and baffle plates) and limiter in EAST. The damage is identified as being induced by runaway electron loss during plasma disruption at the beginning of each plasma campaign. It typically occurs at the leading edges or protruding parts of PFCs, sometimes accompanied by visible macrocracks. In terms of melting phenomena, three distinct grain layers can be observed from the molten surface to deeper regions, namely columnar grain, equiaxed grain (recrystallization region) and original grain. This grain distribution indicates a steep temperature gradient from the surface to the deeper regions during melting events, a characteristic feature for W under fusion-relevant transient heat flux loading. The surface morphologies of all melted PFCs are generally similar, characterized by undulated melting waves. The motion of the melting layer is primarily along the toroidal direction, as shown in the in situ melting of PFCs. The influence of the J × B force might not be significant due to the limited lifetime of the melting pool, which results in limited acceleration times and expected bulk melt displacement. The directions of plasma pressure and Marangoni flow, both along the toroidal direction, might be the dominant forces here. Additionally, cracks at the leading edges were observed on the divertor dome and baffle plates during post-mortem inspection. In some cases, dense cracks were visible in the melting region and even in areas far from the melting zone. It should be noted that cracks were only found in partially melted PFCs, which could be related to the base temperature when PFCs were hit by the runaway electron-induced transient heat flux. Furthermore, some columnar grains were observed to exfoliate from the material, indicating severe cracking. Since EAST has similar W PFCs to ITER, the transient heat flux-induced melting and cracking damage to W PFCs by runaway electrons during plasma disruption in EAST provide important references for ITER. |
| format | Article |
| id | doaj-art-efe1d013df1a4559ab3c5aedd45e8145 |
| institution | DOAJ |
| issn | 0029-5515 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | Nuclear Fusion |
| spelling | doaj-art-efe1d013df1a4559ab3c5aedd45e81452025-08-20T02:48:39ZengIOP PublishingNuclear Fusion0029-55152025-01-0165404602710.1088/1741-4326/adc1e0Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EASTChuannan Xuan0Dahuan Zhu1Yang Wang2Binfu Gao3https://orcid.org/0000-0003-3477-5229Wenxue Fu4Zongxiao Guo5Rui Ding6https://orcid.org/0000-0003-2880-9736Baoguo Wang7Pengfei Zi8Junling Chen9the EAST TeamHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, China; University of Science and Technology of China , Hefei 230036, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, China; University of Science and Technology of China , Hefei 230036, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, China; University of Science and Technology of China , Hefei 230036, ChinaCollege of Physics and Optoelectronics Engineering, Shenzhen University , Shenzhen 518060, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, ChinaHFIPS, Chinese Academy of Sciences, Institute of Plasma Physics , Hefei 230031, ChinaTransient heat flux of up to several thousand MW m ^−2 in a short pulse (∼ms) in tokamaks poses great risk to plasma-facing components (PFCs), making it a major concern for ITER. Despite numerous high heat flux tests, analysis of in situ transient heat flux-induced damage to PFCs remains necessary. Such damage, including the melting and cracking of tungsten (W) PFCs, is notably observed on the divertor (dome and baffle plates) and limiter in EAST. The damage is identified as being induced by runaway electron loss during plasma disruption at the beginning of each plasma campaign. It typically occurs at the leading edges or protruding parts of PFCs, sometimes accompanied by visible macrocracks. In terms of melting phenomena, three distinct grain layers can be observed from the molten surface to deeper regions, namely columnar grain, equiaxed grain (recrystallization region) and original grain. This grain distribution indicates a steep temperature gradient from the surface to the deeper regions during melting events, a characteristic feature for W under fusion-relevant transient heat flux loading. The surface morphologies of all melted PFCs are generally similar, characterized by undulated melting waves. The motion of the melting layer is primarily along the toroidal direction, as shown in the in situ melting of PFCs. The influence of the J × B force might not be significant due to the limited lifetime of the melting pool, which results in limited acceleration times and expected bulk melt displacement. The directions of plasma pressure and Marangoni flow, both along the toroidal direction, might be the dominant forces here. Additionally, cracks at the leading edges were observed on the divertor dome and baffle plates during post-mortem inspection. In some cases, dense cracks were visible in the melting region and even in areas far from the melting zone. It should be noted that cracks were only found in partially melted PFCs, which could be related to the base temperature when PFCs were hit by the runaway electron-induced transient heat flux. Furthermore, some columnar grains were observed to exfoliate from the material, indicating severe cracking. Since EAST has similar W PFCs to ITER, the transient heat flux-induced melting and cracking damage to W PFCs by runaway electrons during plasma disruption in EAST provide important references for ITER.https://doi.org/10.1088/1741-4326/adc1e0EASTmeltingcrackingtungsten PFCstransient heat fluxdisruption |
| spellingShingle | Chuannan Xuan Dahuan Zhu Yang Wang Binfu Gao Wenxue Fu Zongxiao Guo Rui Ding Baoguo Wang Pengfei Zi Junling Chen the EAST Team Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EAST Nuclear Fusion EAST melting cracking tungsten PFCs transient heat flux disruption |
| title | Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EAST |
| title_full | Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EAST |
| title_fullStr | Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EAST |
| title_full_unstemmed | Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EAST |
| title_short | Characterization of in situ damage to tungsten PFCs induced by transient heat flux during plasma disruption in EAST |
| title_sort | characterization of in situ damage to tungsten pfcs induced by transient heat flux during plasma disruption in east |
| topic | EAST melting cracking tungsten PFCs transient heat flux disruption |
| url | https://doi.org/10.1088/1741-4326/adc1e0 |
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