{
  "abstract": "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.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Rev. Sci. Instrum. 97, 093512 (2026)",
  "arxiv": "2605.20993",
  "author_total": 11,
  "authors": [
    {
      "name": "A. Maan"
    },
    {
      "name": "Tosh Le"
    },
    {
      "name": "D. P. Boyle"
    },
    {
      "name": "R. Majeski"
    },
    {
      "name": "S. Banerjee"
    },
    {
      "name": "G. J. Wilkie"
    },
    {
      "name": "M. Lampert"
    },
    {
      "name": "C. Lopez Perez"
    },
    {
      "name": "R. Shousha"
    },
    {
      "name": "W. Capecchi"
    },
    {
      "name": "H. Gajani"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/74rkwbq0dwx80.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2605.20993",
  "fulltext_url": null,
  "id": "74rkwbq0dwx80",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2605.20993",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.plasm-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2605.20993",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-07",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/74rkwbq0dwx80.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:12Z",
      "native_id": "2605.20993",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2605.20993"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.plasm-ph",
      "subfield": "plasma"
    }
  ],
  "title": "Photodiode based multi-modal diagnostic for low-energy neutral beam injection in the LTX-$β$ spherical tokamak",
  "title_text": "Photodiode based multi-modal diagnostic for low-energy neutral beam injection in the LTX-β spherical tokamak",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:12Z",
  "url": "https://research.draconitic.com/paper/74rkwbq0dwx80",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1063/5.0344755",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}