Validation of SOLPS-ITER simulations with kinetic, fluid, and hybrid neutral models for JET-ILW low-confinement mode plasmas
N. Horsten, M. Groth, W. Dekeyser, Wim Van Uytven, S. Aleiferis, S. Carli, J. Karhunen, K. Lawson, B. Lomanowski, A. Meigs, S. Menmuir, A. Shaw, В. В. Солоха, B. Thomas
Abstract
For JET L-mode plasmas in low-recycling conditions (electron temperature at the outer strike point, Te,ot≳30eV), SOLPS-ITER simulations agree within the error bars for the experimental profiles at the low-field side (LFS) divertor target. The peak Balmer-α (Dα) emission in the LFS divertor agrees within the error bars of the KS3 filterscope diagnostic, but is approximately 30% lower than the peak value of the KT1 spectrometer. Simulations have been performed with fluid, kinetic, and hybrid models for the neutrals. The large fluid-kinetic discrepancies of more than a factor 2 are successfully corrected by using a hybrid fluid-kinetic approach, for which kinetic atoms are transferred to the fluid population when the local Knudsen number of the atom becomes smaller than a user-defined transition Knudsen number Knt. The hybrid-kinetic discrepancies are limited to a few % for Knt≤100. When increasing the upstream density to high-recycling conditions, at the onset of detachment (Te,ot≈5eV), the simulations predict more than a factor 2 lower peak ion saturation current to the LFS divertor than the experiments. Also the Dα emission is underpredicted with approximately a factor 2. For these high-recycling conditions, the fluid-kinetic discrepancies are limited to maximum 50%, which are again corrected by using the hybrid approach.