{
  "abstract": "We present magnetic configurations in the Helically Symmetric eXperiment (HSX) and Wendelstein 7-X (W7-X), in which the edge magnetic structure exhibits island chains which are spatially larger than the previously reported configurations. These ``giant\" island chains (with rotational transform $ι=4/3$ or $4/4$ for HSX and $ι=5/6$, $5/5$ or $5/4$ for W7-X) are obtained by reducing the coil current in main coil 6 for HSX and non-planar coil 5 for W7-X (i.e. the coil nearest the up-down symmetric cross-section $ϕ=36^\\circ$ for W7-X and $ϕ=45^\\circ$ for HSX). This appears a sufficient (but not necessary) condition for giant islands. The giant islands create X-point legs which transport plasma to the plasma-facing components (PFCs). In the most extreme cases, the island O-points leave the domain of the field line map and the divertor legs of the remaining ``unpaired\" X-points do not close around the island. We show for W7-X, via the construction of quadratic flux-minimising surfaces, that these island size trends can mostly be interpreted as changes in magnitude of a resonant perturbation on a changing resonant ``unperturbed\" magnetic surface. We use the anisotropic heat diffusion code EMC3-Lite to find ``giant island\" W7-X configurations which are promising for PFC heat loads. These configurations significantly degrade the neoclassical transport performance but allow exploration of novel divertor regimes; for example, we show that the internal island pitch can be increased. This leads to favourable downstream/upstream plasma density ratios according to simple models; an attractive finding which motivates further investigation.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2607.14722",
  "author_total": 8,
  "authors": [
    {
      "name": "Robert Davies"
    },
    {
      "name": "Dieter Boeyaert"
    },
    {
      "name": "Alexis Wolfmeister"
    },
    {
      "name": "Benedikt Geiger"
    },
    {
      "name": "Georg Harrer"
    },
    {
      "name": "Joachim Geiger"
    },
    {
      "name": "Louis Day"
    },
    {
      "name": "Lucas Sanchez-Garay"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/eqzcd0rbaw24b.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.14722",
  "fulltext_url": null,
  "id": "eqzcd0rbaw24b",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.14722",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.plasm-ph"
    ],
    [
      "openalex",
      "3106|Magnetic confinement fusion research"
    ]
  ],
  "openalex": "W7169551613",
  "pdf_url": "https://arxiv.org/pdf/2607.14722",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/eqzcd0rbaw24b.ris",
  "sources": [
    {
      "first_seen": "2026-11-03T12:20:58Z",
      "native_id": "2607.14722",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.14722"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.plasm-ph",
      "subfield": "plasma"
    }
  ],
  "title": "Computational studies of giant edge islands and unpaired X-points in HSX and W7-X by manipulating coil currents",
  "title_text": "Computational studies of giant edge islands and unpaired X-points in HSX and W7-X by manipulating coil currents",
  "type": "preprint",
  "updated_at": "2026-11-03T12:20:58Z",
  "url": "https://research.draconitic.com/paper/eqzcd0rbaw24b",
  "venue": "arXiv",
  "versions": []
}