Recent results on divertor detachment experiments in alternative configurations on TCV

Recent experiments on the TCV tokamak explore the influence of the divertor magnetic geometry on the plasma exhaust performance, in particular the detachment threshold and stability. In typical TCV Single-Null shapes, poloidal flux expansion is varied by factors of up to five, resulting in a threefold increase in midplane to outer target connection length. X-Divertor geometries are generated to investigate the role of poloidal flux flaring near the outer target, and the effect of additional x-points in the main SOL, near the primary x-point and near the target, is investigated in Snowflake and X-point Target divertors. Finally, the effect of total flux expansion is studied in Super-X divertor geometries with and without a second x-point (see figure below for example equilibria). Partial detachment of the outer target is achieved in these plasmas using density ramps and nitrogen seeding. An investigation of the role of the different geometrical properties on the detachment behavior will be presented using measurements from a recently upgraded suite of edge diagnostics, including a fast reciprocating probe and wall probes, infrared thermography, divertor spectroscopy and bolometry.