An Implicit Monte Carlo Method for Simulation of Impurity Transport in Divertor Plasma

A new "implicit" Monte Carlo (IMC) method has been developed to simulate ionization and recombination processes of impurity ions in divertor plasmas. The IMC method takes into account many ionization and recombination processes during a time step Δt. The time step is not limited by a condition, Δt≪ τ_min(τ_min; the minimum characteristic time of atomic processes), which is forced to be adopted in conventional Monte Carlo methods. We incorporate this method into a one-dimensional impurity transport model. In this transport calculation, impurity ions are followed with the time step about 10 times larger than that used in conventional methods. The average charge state of impurities, 〈Z〉, and the radiative cooling rate,L(T_e), are calculated at the electron temperatureT_ein divertor plasmas. These results are compared with thosed obtained from the simple noncoronal model.