École Polytechnique Fédérale de Lausanne
Friday, September 9, 2016
Abstract: Recent experiments on the TCV tokamak explore the influence of the divertor magnetic geometry on the detachment behavior and the plasma exhaust performance. Starting from typical TCV Single-Null shapes, poloidal flux expansion at the outer strike point is varied by a factor ten to investigate the X-Divertor characteristics and total flux expansion is varied by 70% to study the properties of the Super-X Divertor. 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. Partial detachment of the outer target is achieved in these plasmas during ohmic density ramps. The detachment characteristics, such as threshold and sensitivity of the detachment front location on upstream density, is investigated using measurements from a recently upgraded suite of edge diagnostics and results are compared with trends from simplified SOL models.
Bio: Christian Theiler obtained his master’s degree in physics from ETH Zurich and his PhD from EPFL. After a two-year postdoctoral research position at MIT’s Alcator C-Mod tokamak, he returned to EPFL as a EUROfusion fellow. In July 2016, he has been named Tenure Track Assistant Professor in Plasma Physics at EPFL. His research focuses on tokamak boundary physics and related diagnostic techniques. He has contributed to the understanding of the formation, propagation, and control of plasma blobs and has gained detailed new insights on the structure of the edge pedestal in different high-confinement regimes. Currently, he is focusing on detachment physics in alternative divertor magnetic geometries.