A new fast velocity-diffusion modelling for impurity transport in integrated edge plasma simulation

A fast velocity-diffusion model, which applies to an impurity Monte–Carlo (MC) code, such as IMPMC, is newly developed. The algorithm significantly reduces the computational time, especially in detached plasma, its speed attains more than 100 times faster than the conventional MC method. The performance of IMPMC is further optimized on the massive parallel computer. Thereby the IMPMC is combined with a so-called divertor code, and a self-consistent modelling of divertor plasma and impurity transport is successfully achieved. The integrated code, SONIC (SOLDOR/NEUT2D/IMPMC) is characterized by treatment for kinetic effects and complicated dissociation process of methane. As initial simulations with SONIC, the dynamic evolution of X-point MARFE in JT-60U is investigated. Neutral carbons chemically sputtered from the dome in the private region can deeply penetrate into the main plasma and are subsequently ionized/recombined near the X-point. The resultant carbon ions cause large radiation during MARFE phase.