The effects of H blistering and ELMs on the thermal fatigue cracking of W by strikepoint sweeping
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arXiv
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| Autores principales: | , , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866918238980407296 |
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| author | Hargreaves, J. Vernimmen, J. Scholten, J. Morgan, T. W |
| author_facet | Hargreaves, J. Vernimmen, J. Scholten, J. Morgan, T. W |
| contents | Cyclic thermal loads imposed on a W divertor by strikepoint sweeping may induce low-cycle thermal fatigue cracking of its plasma-facing surfaces. This cracking may be accelerated by plasma-material interactions such as H implantation, blistering, fuzz and void formation. Fatigue cracking may also synergise with ELM cracking. To explore these novel forms of environmentally assisted fatigue, FEA modelling was used to design a uniaxial fatigue experiment for Magnum-PSI that represents strikepoint sweeping at 1 Hz across a 100 mm span of a divertor target. Magnum-PSI was used to combine cyclic thermal loading of W with H implantation and two forms of ELM like pre-cracking. Quantitative SEM analysis of fatigue-cracked W revealed that H implantation significantly delayed crack initiation, with preimplanted targets requiring 450-600 cycles before failure compared to 150 cycles for non-implanted samples. This was attributed to hydrogen-induced dislocation pinning, which produces a case-hardening effect that inhibits persistent slip band formation. ELM-like pre-cracking combined with strikepoint sweeping was found to give rise to localised melting and the formation of 30 micromete diameter droplets, caused by thermal isolation of W regions by fatigue cracks. The implications for the fatigue lifetime of tokamak divertors are also discussed. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_07891 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The effects of H blistering and ELMs on the thermal fatigue cracking of W by strikepoint sweeping Hargreaves, J. Vernimmen, J. Scholten, J. Morgan, T. W Plasma Physics Materials Science Cyclic thermal loads imposed on a W divertor by strikepoint sweeping may induce low-cycle thermal fatigue cracking of its plasma-facing surfaces. This cracking may be accelerated by plasma-material interactions such as H implantation, blistering, fuzz and void formation. Fatigue cracking may also synergise with ELM cracking. To explore these novel forms of environmentally assisted fatigue, FEA modelling was used to design a uniaxial fatigue experiment for Magnum-PSI that represents strikepoint sweeping at 1 Hz across a 100 mm span of a divertor target. Magnum-PSI was used to combine cyclic thermal loading of W with H implantation and two forms of ELM like pre-cracking. Quantitative SEM analysis of fatigue-cracked W revealed that H implantation significantly delayed crack initiation, with preimplanted targets requiring 450-600 cycles before failure compared to 150 cycles for non-implanted samples. This was attributed to hydrogen-induced dislocation pinning, which produces a case-hardening effect that inhibits persistent slip band formation. ELM-like pre-cracking combined with strikepoint sweeping was found to give rise to localised melting and the formation of 30 micromete diameter droplets, caused by thermal isolation of W regions by fatigue cracks. The implications for the fatigue lifetime of tokamak divertors are also discussed. |
| title | The effects of H blistering and ELMs on the thermal fatigue cracking of W by strikepoint sweeping |
| topic | Plasma Physics Materials Science |
| url | https://arxiv.org/abs/2512.07891 |