IMPURITY TRANSPORT MODELING AND SIMULATION ANALYSIS OF IMPURITY BEHAVIOR IN JT-60U

A two-dimensional impurity code based on Monte Carlo techniques (IMPMC) has been developed, in order to study the impurity behavior in the divertor plasma. The model includes (1) impurity generation at the divertor plate, (2) ionization of sputtered neutrals, (3) parallel motion of impurity ions along field lines, (4) Coulomb scattering, (5) cross-field diffusion, and (6) atomic processes. This model is applied to the carbon impurity behavior in a JT-60U NB heated plasma. The impurity generation mechanism, the effect of the thermal force on impurity shielding, and the contribution of charge exchange recombination to C3+ ion density near the plates are clarified. The measured spatial profile of the CIV line indicates that the diffusion coefficient, D-perpendicular to is around 1 m(2)/s. The ion temperature measured by Doppler broadening of the CIV line is found to be shifted to lower temperature side due to the overspread distribution of C3+ ions in the SOL by the thermal force.