dorsal/arxiv
View SchemaFormation 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 |
|---|---|
| Categories | |
| ArXiv ID | physics/0410208 |
| URL | https://arxiv.org/abs/physics/0410208 |
| DOI | 10.1088/0741-3335/47/4/004 |
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.
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"abstract": "Understanding of the scrape-off layer (SOL) physics in tokamaks requires\ndiagnostics with sufficient temporal and spatial resolution. This contribution\ndescribes results of experiments performed in the SOL of the CASTOR tokamak\n(R=40 cm, a = 6 cm) by means of a ring of 124 Langmuir probes surrounding the\nwhole poloidal cross section. The individual probes measure either the ion\nsaturation current of the floating potential with the spatial resolution up to\n3 mm. Experiments are performed in a particular magnetic configuration,\ncharacterized by a long parallel connection length in the SOL, L_par ~q2piR. We\nreport on measurements in discharges, where the edge electric field is modified\nby inserting a biased electrode into the edge plasma. In particular, a complex\npicture is observed, if the biased electrode is located inside the SOL. The\npoloidal distribution of the floating potential appears to be strongly\nnon-uniform at biasing. The peaks of potential are observed at particular\npoloidal angles. This is interpreted as formation of a biased flux tube, which\nemanates from the electrode along the magnetic field lines and snakes q times\naround the torus. The resulting electric field in the SOL is 2-dimensional,\nhaving the radial as well as the poloidal component. It is demonstrated that\nthe poloidal electric field E_pol convects the edge plasma radially due to the\nE_pol x B_T drift either inward or outward depending on its sign. The\nconvective particle flux is by two orders of magnitude larger than the\nfluctuation-induced one and consequently dominates.",
"arxiv_id": "physics/0410208",
"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"
],
"categories": [
"physics.plasm-ph"
],
"doi": "10.1088/0741-3335/47/4/004",
"title": "Formation of convective cells in the scrape-off layer of the CASTOR tokamak",
"url": "https://arxiv.org/abs/physics/0410208"
},
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