{
  "abstract": "The flux of protons slow-extracted from the CERN Super Proton Synchrotron (SPS) to the North Area experiments is limited by the induced radioactivity of the beam lost on the electrostatic septum during the third-integer resonant extraction. Crystal shadowing, in which a thin bent silicon crystal deflects the portion of beam that would otherwise impinge on the septum wires, has been in operation at the SPS since 2021, and a single crystal at a non-local position halved the extraction losses, short of the fourfold reduction that the activation budget of the future high-intensity operation calls for. In this paper, the design, deployment and operation of a 3-crystal Multi-Volume Reflection Array (MVRA) at the non-local position in the fourth long straight section (LSS4) are presented. The array geometry was designed by Multi-Fidelity Bayesian Optimization (MFBO), combining a multilayer-perceptron surrogate with full particle tracking, which predicts a fourfold loss reduction with three crystals and up to tenfold with an ideally aligned array of four to five. Measurements with beam confirm the prediction: at its optimum the as-built array reduces the losses by the predicted factor of four, and beam dynamics simulations matched to the measured position and angle scans reproduce them to a few per cent. The array has since been used in physics production, held on its operating plateau by an extremum-seeking controller, with a median loss reduction by a factor of 3.6 over 0.1 million extraction cycles relative to the pre-shadowing baseline. The remaining margin to the target, the limitations of the present installation and the upgrade to a 4- or 5-crystal array are discussed.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.23823",
  "author_total": 13,
  "authors": [
    {
      "name": "F. M. Velotti"
    },
    {
      "name": "M. Bay"
    },
    {
      "name": "T. Calvet"
    },
    {
      "name": "M. Calviani"
    },
    {
      "name": "G. Daher"
    },
    {
      "name": "L. S. Esposito"
    },
    {
      "name": "M. A. Fraser"
    },
    {
      "name": "B. Goddard"
    },
    {
      "name": "M. Howes"
    },
    {
      "name": "V. Kain"
    },
    {
      "name": "E. Matheson"
    },
    {
      "name": "A. Perillo Marcone"
    },
    {
      "name": "R. Seidenbinder"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3cc67q3hdkvya.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.23823",
  "fulltext_url": null,
  "id": "3cc67q3hdkvya",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.23823",
  "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.acc-ph"
    ],
    [
      "openalex",
      "2202|Particle accelerators and beam dynamics"
    ]
  ],
  "openalex": "W7214035179",
  "pdf_url": "https://arxiv.org/pdf/2609.23823",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-25",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3cc67q3hdkvya.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:24:52Z",
      "native_id": "2609.23823",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.23823"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.acc-ph",
      "subfield": "applied-instrumentation"
    }
  ],
  "title": "Design and Operation of a 3-Crystal Multi-Volume Reflection Array for Loss Reduction in CERN SPS Slow Extraction",
  "title_text": "Design and Operation of a 3-Crystal Multi-Volume Reflection Array for Loss Reduction in CERN SPS Slow Extraction",
  "type": "preprint",
  "updated_at": "2026-10-30T12:24:52Z",
  "url": "https://research.draconitic.com/paper/3cc67q3hdkvya",
  "venue": "arXiv",
  "versions": []
}