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P: Fachverband Plasmaphysik

P 5: Poster I

P 5.29: Poster

Dienstag, 31. August 2021, 14:00–16:00, P

Heat conduction simulation in plasmas with magnetic field lines of mixed topology — •Gregor Pechstein, Brendan Shanahan, and Per Helander — Max-Planck-Institut für Plasmaphysik, Wendelsteinstraße 1, 17491 Greifswald

Fusion devices must dissipate heat before it reaches the plasma-facing components. For this purpose the W7-X stellarator relies on a chain of magnetic islands close to the plasma edge channelling the plasma to a divertor. Detachment, a scenario in which energy is radiated due to collisions with neutrals, is a promising method for reducing heat flux onto the divertor. First divertor experiments on W7-X exhibit stable detachment, whose main features are reproduced by the EMC3-Eirene edge transport code. With an increase in the radiated power fraction the position of the radiation front approaches the X-point and the separatrix of the magnetic islands. Here we seek to understand the stability and position of the detached radiation front using a heat conduction model. In contrast to 1-d analytical heat conduction models used in Tokamak divertors, perpendicular transport cannot be ignored in the islands of W7-X. The importance of transport perpendicular to the magnetic field is due to the long connection lengths in the islands. Accordingly, we perform 2-d heat conduction simulations in slab geometry with an island. These simulations employ a simplified radiation function as a heat sink. Depending on the parameter varied the radiation front exhibits different patterns and stability. Concomitant to the simulations, analytical limits of the parameter space are investigated. The implications for stable detachment in W7-X will be discussed.