The DIII-D upper divertor will be modified in late 1999 by installing a continuous dome in the private flux region with an independent pumping capability for the inner strike point. A 'bump' on the inner cylinder also has been considered to enhance impurity and neutral control. Using the UEDGE code, we have examined the effect of this dome and the 'bump' on core ionization and core impurity content. For typical parameters, results indicate that the planned divertor modifications enable detachment at higher heating power and the 'fueling efficiency' (ratio of core neutral ionization rate to total divertor ion current) decreases, however, the core carbon content increases. The inner 'bump' does enhance 'fueling efficiency' compared to the private flux dome alone, but it does not reduce the increased core impurity content.
展开▼
