Results from recent detachment experiments in alternative divertor configurations on TCV

TCV Team; EUROfusion MST1 TeamTheiler, CLipschultz, BHarrison, JLabit, BReimerdes, HTsui, CVijvers, W A JDuva, B PElmore, SInnocente, PKruezi, ULunt, TMaurizio, RNespoli, FSheikh, UThornton, A Jvan Limpt, S H MVerhaegh, KVianello, N2017-03-222017-03-222017-03-22201710.1088/1741-4326/aa5fb7https://infoscience.epfl.ch/handle/20.500.14299/135647WOS:000398746200001Divertor 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 gradB 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 2â 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.detachmentalternative divertorsX-divertorsuper-X divertorX-point target divertorspc_edgeResults from recent detachment experiments in alternative divertor configurations on TCVtext::journal::journal article::research article