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| Autori principali: | , , , , , , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| Soggetti: | |
| Accesso online: | https://arxiv.org/abs/2605.20993 |
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| _version_ | 1866911701226487808 |
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| author | Maan, A. Le, Tosh Boyle, D. P. Majeski, R. Banerjee, S. Wilkie, G. J. Lampert, M. Perez, C. Lopez Shousha, R. Capecchi, W. Gajani, H. |
| author_facet | Maan, A. Le, Tosh Boyle, D. P. Majeski, R. Banerjee, S. Wilkie, G. J. Lampert, M. Perez, C. Lopez Shousha, R. Capecchi, W. Gajani, H. |
| contents | We present a compact photodiode-based diagnostic array developed to study low-energy neutral beam injection in the LTX-$β$ spherical tokamak. The in-vacuum diagnostic combines filtered soft-x-ray (SXR), narrowband Lyman-$α$, and unfiltered AXUV photodiode rows with partly overlapping, nearly coincident tangential views of the plasma, including the neutral beam path. This geometry provides simultaneous sensitivity to beam-induced SXR emission; neutral-hydrogen line radiation associated with recycling, fast neutrals and fueling; and broadband emission that can include direct neutral impacts from fast-ion charge-exchange losses. Initial measurements from 12-20 keV hydrogen beam operation show beam-synchronous detector responses in all three modalities. The unfiltered AXUV signals exhibit millisecond-scale rise and fall times that are much slower than the detector response, that vary across sightlines, and depend on lithium-conditioning history. Comparison with classical slowing-down time estimates indicates that charge exchange with background neutrals contributes appreciably to the measured decay. The diagnostic can potentially be used to constrain a forward model to estimate the time-resolved balance of beam heating and fueling for small tokamaks. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_20993 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Photodiode based multi-modal diagnostic for low-energy neutral beam injection in the LTX-$β$ spherical tokamak Maan, A. Le, Tosh Boyle, D. P. Majeski, R. Banerjee, S. Wilkie, G. J. Lampert, M. Perez, C. Lopez Shousha, R. Capecchi, W. Gajani, H. Plasma Physics We present a compact photodiode-based diagnostic array developed to study low-energy neutral beam injection in the LTX-$β$ spherical tokamak. The in-vacuum diagnostic combines filtered soft-x-ray (SXR), narrowband Lyman-$α$, and unfiltered AXUV photodiode rows with partly overlapping, nearly coincident tangential views of the plasma, including the neutral beam path. This geometry provides simultaneous sensitivity to beam-induced SXR emission; neutral-hydrogen line radiation associated with recycling, fast neutrals and fueling; and broadband emission that can include direct neutral impacts from fast-ion charge-exchange losses. Initial measurements from 12-20 keV hydrogen beam operation show beam-synchronous detector responses in all three modalities. The unfiltered AXUV signals exhibit millisecond-scale rise and fall times that are much slower than the detector response, that vary across sightlines, and depend on lithium-conditioning history. Comparison with classical slowing-down time estimates indicates that charge exchange with background neutrals contributes appreciably to the measured decay. The diagnostic can potentially be used to constrain a forward model to estimate the time-resolved balance of beam heating and fueling for small tokamaks. |
| title | Photodiode based multi-modal diagnostic for low-energy neutral beam injection in the LTX-$β$ spherical tokamak |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2605.20993 |