Effects of Classical and Neo‐classical Cross‐field Transport of Tungsten Impurity in Realistic Tokamak Geometry

Abstract

The initial simulation study of the neoclassical perpendicular self-diffusion transport in the SOL/Divertor regions for a realistic tokamak geometry with the IMPGYRO code has been performed in this paper. One of the most unique features of the IMPGYRO code is calculating exact Larmor orbit of the test particle instead of assuming guiding center approximation. Therefore, effects of the magnetic drifts in realistic tokamaks are naturally taken into account in the IMPGYRO code. This feature makes it possible to calculate neoclassical transport processes, which possibly become large in the SOL/divertor plasma. Indeed, neoclassical self-diffusion process, the resultant effect of the combination of magnetic drift and Coulomb collisions with background ions, has already been included in the IMPGYRO model. In the present paper, prior to implementing the detailed model of neoclassical transport process into IMPGYRO, we have investigated the effect of neoclassical selfdiffusion in a realistic tokamak geometry with lower single null X-point. We also use a model with guiding center approximation in order to compare with the IMPGYRO full orbit model. The preliminary calculation results of each model have shown differences in the perpendicular average velocity of impurity ions at the top region of the SOL. The mechanism which leads to the difference has been discussed.

Simulation study of the influence of E× B drift on tungsten impurity transport in the scrape-off layer

“…The erosion/deposition of W has been simulated by threedimensional Monte-Carlo code ERO with drifts included for EAST [47] and JET [48], whereas W transport toward the upstream has not been discussed. The drifts of W ions have been included in the recently developed full-orbit impurity transport code IMPGYRO in simulations for ASDEX-Upgrade [49,50], JT-60U [51,52], and ITER [53], contrary to the effect of E × B drift on the background plasma. Studies on the W erosion/deposition [46] and the influence on the W erosion and leakage of divertor geometries [54] have been conducted for DIII-D, where the effect of E × B drift on the background plasma and W ions are considered using OSM-EIRENE/scape-off layer plasma simulation (SOLPS)-ITER and DIVIMP codes, respectively.…”