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 statemodel by the coupled multi-fluid plasma and kinetic neutral code SOLPS-ITER. This work focuses on the comparisons of several bundledcharge state models of W and the all W ion model in low and high recycling divertor operational regimes. It is found that bundled chargestate models have a pronounced effect on the reduction of computational time and computer memory and provide an improved marked codespeed by a factor of more than five. In the low recycling regime, compared to the full W charge state model, the differences in the plasmaparameters at both divertor targets are within 15% for different bundling schemes. In the high recycling regime, no significant differencebetween bundled charge state models and the all charge state model is observed due to the very low W concentration (∼10 −6 ). It, therefore,indicates thatbundled charge state models ofW can describe divertorparameters well to aconsiderable degree. Besides, theerrors of tungstenconcentration(C W )andtheeffectiveionchargenumber(Z eff )attheoutermid-planeforbundledmodelsarewithin40%insidetheseparatrix.At the same time, highly resolved bundled models with more than 20W 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 coreradiation, which is strongly related to the bundling schemes for relatively high charge states.