Runaway electrons during a coil quench in stellarators
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866917387123556352 |
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| author | Aleynikov, Pavel Helander, Per Smith, Håkan M |
| author_facet | Aleynikov, Pavel Helander, Per Smith, Håkan M |
| contents | It is shown that avalanches of runaway electrons can arise in stellarators, even if there is no net toroidal current in the plasma or the magnetic-field coils, if the current in the latter varies rapidly enough, e.g. due to a superconductor quench. In present-day devices such as W7-X, significant runaway generation is theoretically possible only at very low gas or plasma density in the vacuum vessel, e.g. between discharges, if a seed population of free electrons is present. In reactor-scale stellarators, more dangerous runaway generation may occur both between discharges and during low-density plasma operation. Since a radiation-induced seed population is necessarily present in an activated device, an accidental coil ramp-down could convert substantial magnetic energy into wall-damaging runaway currents. There is however much more time to mitigate such events than in tokamaks disruptions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_15721 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Runaway electrons during a coil quench in stellarators Aleynikov, Pavel Helander, Per Smith, Håkan M Plasma Physics It is shown that avalanches of runaway electrons can arise in stellarators, even if there is no net toroidal current in the plasma or the magnetic-field coils, if the current in the latter varies rapidly enough, e.g. due to a superconductor quench. In present-day devices such as W7-X, significant runaway generation is theoretically possible only at very low gas or plasma density in the vacuum vessel, e.g. between discharges, if a seed population of free electrons is present. In reactor-scale stellarators, more dangerous runaway generation may occur both between discharges and during low-density plasma operation. Since a radiation-induced seed population is necessarily present in an activated device, an accidental coil ramp-down could convert substantial magnetic energy into wall-damaging runaway currents. There is however much more time to mitigate such events than in tokamaks disruptions. |
| title | Runaway electrons during a coil quench in stellarators |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2509.15721 |