Results from recent detachment experiments in alternative divertor configurations on TCV

TitleResults from recent detachment experiments in alternative divertor configurations on TCV
Publication TypeJournal Article
Year of Publication2017
AuthorsC. Theiler, B. Lipschultz, J. Harrison, B. Labit, H. Reimerdes, C. Tsui, W.AJ Vijvers, J.A Boedo, B.P Duval, S. Elmore, P. Innocente, U. Kruezi, T. Lunt, R. Maurizio, F. Nespoli, U. Sheikh, A.J Thornton, S.HM van Limpt, K. Verhaegh, N. Vianello, TCV team, EUROfusion MST1 Team
JournalNuclear Fusion

Divertor detachment is explored on the TCV tokamak in alternative magnetic geometries. Starting from typical TCV single-null shapes, the poloidal flux expansion at the outer strikepoint is varied by a factor of 10 to investigate the X-divertor characteristics, and the total flux expansion is varied by 70% to study the properties of the super-X divertor. The effect of an additional X-point near the target is investigated in X-point target divertors. Detachment of the outer target is studied in these plasmas during Ohmic density ramps and with the ion {$\nabla $} B drift away from the primary X-point. The detachment threshold, depth of detachment, and the stability of the radiation location are investigated using target measurements from the wall-embedded Langmuir probes and two-dimensional CIII line emissivity profiles across the divertor region, obtained from inverted, toroidally-integrated camera data. It is found that increasing poloidal flux expansion results in a deeper detachment for a given line-averaged density and a reduction in the radiation location sensitivity to core density, while no large effect on the detachment threshold is observed. The total flux expansion, contrary to expectations, does not show a significant influence on any detachment characteristics in these experiments. In X-point target geometries, no evidence is found for a reduced detachment threshold despite a 2–3 fold increase in connection length. A reduced radiation location sensitivity to core plasma density in the vicinity of the target X-point is suggested by the measurements.







Alternate TitleNucl. Fusion

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