Momentum balance for impurities in SOLPS transport code

Abstract New form of momentum balance equations for ion species is suggested and implemented into B2SOLPS5.2 code. The original form of Braginskii parallel momentum balance equations is used with parallel electric field on the left hand side which does not require any assumptions in contrast to the existing momentum balance equations solved in SOLPS codes. General expressions for friction and thermal force which are valid for arbitrary densities of different ions are suggested. Convergence of the simulations is the same as in existing B2SOLPS versions. It is demonstrated that results for arbitrary impurity density differs from that obtained for trace impurities due to correct account of friction and thermal forces.