Interpretive Modeling of the Tungsten Source Distribution at the Divertor and Baffle Regions of the WEST Tokamak *

Preliminary simulations of tungsten (W) impurity transport in the WEST tokamak suggest that the baffle structure may be a significant source of W impurities in the plasma due to lower plasma density causing reduced prompt redeposition. A lower hybrid (LH) power scan is investigated, during which the injected power was increased from approximately 0.5 MW to 4.8MW. A grid is constructed extending to flux surfaces terminating at the lower divertor surface. The OSM-EIRENE code is used with divertor Langmuir probe data to create a background plasma model for these discharges. The impurity transport code DIVIMP is used to simulate transport of W impurities, verified against W-I and W-II spectroscopic data. W leakage probabilities out of the divertor and into the core are calculated for both divertor sources. Concurrently, an extended grid is constructed including flux surfaces extending to the baffle structure and upper divertor. A new DIVIMP model is used to simulate transport of W impurities on this extended-grid background and the results are compared to the traditional grid case. The comparison illustrates the relative importance of W transport near the baffle structure and its effects on global W impurity transport in WEST.

*This work is supported by the U.S. DOE under DE-SC0020414