{
  "id": "physics/0410208",
  "version": "v1",
  "published": "2004-10-22T13:31:18.000Z",
  "updated": "2004-10-22T13:31:18.000Z",
  "title": "Formation of convective cells in the scrape-off layer of the CASTOR tokamak",
  "authors": [
    "J. Stockel",
    "P. Devynck",
    "J. Gunn",
    "E. Martines",
    "G. Bonhomme",
    "G. Van Oost",
    "M. Hron",
    "J. Adamek",
    "J. Brotankova",
    "R. Dejarnac",
    "I. Duran",
    "T. Gorler",
    "T. Hansen",
    "R. Panek",
    "P. Stejskal",
    "V. Svoboda",
    "F. Zacek"
  ],
  "comment": "12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France)",
  "categories": [
    "physics.plasm-ph"
  ],
  "abstract": "Understanding of the scrape-off layer (SOL) physics in tokamaks requires diagnostics with sufficient temporal and spatial resolution. This contribution describes results of experiments performed in the SOL of the CASTOR tokamak (R=40 cm, a = 6 cm) by means of a ring of 124 Langmuir probes surrounding the whole poloidal cross section. The individual probes measure either the ion saturation current of the floating potential with the spatial resolution up to 3 mm. Experiments are performed in a particular magnetic configuration, characterized by a long parallel connection length in the SOL, L_par ~q2piR. We report on measurements in discharges, where the edge electric field is modified by inserting a biased electrode into the edge plasma. In particular, a complex picture is observed, if the biased electrode is located inside the SOL. The poloidal distribution of the floating potential appears to be strongly non-uniform at biasing. The peaks of potential are observed at particular poloidal angles. This is interpreted as formation of a biased flux tube, which emanates from the electrode along the magnetic field lines and snakes q times around the torus. The resulting electric field in the SOL is 2-dimensional, having the radial as well as the poloidal component. It is demonstrated that the poloidal electric field E_pol convects the edge plasma radially due to the E_pol x B_T drift either inward or outward depending on its sign. The convective particle flux is by two orders of magnitude larger than the fluctuation-induced one and consequently dominates.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2004-10-22T13:31:18.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "scrape-off layer",
      "castor tokamak",
      "convective cells",
      "edge plasma",
      "spatial resolution"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}