Tungsten divertor plasma simulation with bundled charge state model by SOLPS-ITER on EAST

Research was originally carried out to evaluate plasma performance with a tungsten (W) divertor on EAST using the bundled charge state model by the coupled multi-fluid plasma and kinetic neutral code SOLPS-ITER. This work focuses on the comparisons of several bundled charge state models of W and the all W ion model in low and high recycling divertor operational regimes. It is found that bundled charge state models have a pronounced effect on the reduction of computational time and computer memory and provide an improved marked code speed by a factor of more than five. In the low recycling regime, compared to the full W charge state model, the differences in the plasma parameters at both divertor targets are within 15% for different bundling schemes. In the high recycling regime, no significant difference between bundled charge state models and the all charge state model is observed due to the very low W concentration (∼10−6). It, therefore, indicates that bundled charge state models of W can describe divertor parameters well to a considerable degree. Besides, the errors of tungsten concentration (CW) and the effective ion charge number (Zeff) at the outer mid-plane for bundled models are within 40% inside the separatrix. At the same time, highly resolved bundled models with more than 20 W fluids can describe the radiation power loss consistently within 50% as compared with the all charge state model, while it varies greatly from one aggressively bundled model to the other, especially for core radiation, which is strongly related to the bundling schemes for relatively high charge states.