Performance simulation of divertor neutral baffles in the TCV tokamak with the SolEdge2D-EIRENE code

A gas baffle will soon be inserted in the vessel of the tokamak à configuration variable (TCV) [Reimerdes, Nucl. Mat. and Energy 2017]. This upgrade aims at achieving more favorable conditions for the onset of detachment. In this work, we simulate the effect of the baffle on the TCV edge plasma with the SolEdge2D-EIRENE code [Bufferand, Nucl. Fusion 2015], which couples a fluid plasma model to a kinetic model for neutrals and impurities. Firstly, a specific TCV shot with a baffle-compatible shape is simulated. This comparison allows to tune perpendicular transport coefficients in order to match upstream experimental profiles, and results in a good agreement with the experiment at the targets. The same simulation is then carried out including the baffle. The neutral compression ratio, namely the ratio between divertor and upstream neutral pressure, is shown to improve by a factor of order 10, resulting in bigger power and momentum losses in the divertor plasma. Next, we perform a scan in upstream density to access different divertor regimes, revealing that the neutral compression increases as we approach detachment. Finally, in view of possible future optimizations, the level of baffle closure is varied in the simulations and the feedback on plasma properties is discussed.