A scaling law of the neutral opacity and Balmer-$α$ wing shape in high-temperature plasmas
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arXiv
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| Hauptverfasser: | , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866916412086288384 |
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| author | Fujii, Keisuke Hasuo, Masahiro Goto, Motoshi Lore, Jeremy D. |
| author_facet | Fujii, Keisuke Hasuo, Masahiro Goto, Motoshi Lore, Jeremy D. |
| contents | Hydrogen atoms penetrating deep inside high-temperature magnetically confined plasmas by repetitive charge-exchange collisions result in a particle source, which affects the plasma performance significantly. In this \textit{Letter}, we present an approximate solution of the fluid equations for neutral transport and the analytical representation of the neutral opacity, in a simplified plasma geometry. This analysis predicts a power-law decay in the Balmer-$α$ line wings which reflects the velocity distribution of the neutral atoms, with the power-law index analytically represented as well. These scaling laws are validated by the comparison with a simple Monte-Carlo simulation and spectroscopic observations of Large Helical Device plasmas. Since the Balmer-$α$ line wings are experimentally accessible, our formulation opens the door to directly observe the neutral opacity and thus the particle source distribution in the plasma. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2409_18064 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | A scaling law of the neutral opacity and Balmer-$α$ wing shape in high-temperature plasmas Fujii, Keisuke Hasuo, Masahiro Goto, Motoshi Lore, Jeremy D. Plasma Physics Hydrogen atoms penetrating deep inside high-temperature magnetically confined plasmas by repetitive charge-exchange collisions result in a particle source, which affects the plasma performance significantly. In this \textit{Letter}, we present an approximate solution of the fluid equations for neutral transport and the analytical representation of the neutral opacity, in a simplified plasma geometry. This analysis predicts a power-law decay in the Balmer-$α$ line wings which reflects the velocity distribution of the neutral atoms, with the power-law index analytically represented as well. These scaling laws are validated by the comparison with a simple Monte-Carlo simulation and spectroscopic observations of Large Helical Device plasmas. Since the Balmer-$α$ line wings are experimentally accessible, our formulation opens the door to directly observe the neutral opacity and thus the particle source distribution in the plasma. |
| title | A scaling law of the neutral opacity and Balmer-$α$ wing shape in high-temperature plasmas |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2409.18064 |