Origins and spatial distributions of core fueling in the DIII-D tokamak

Analysis of DIII-D discharge data with fluid plasma and Monte Carlo neutral s transport codes reveals that core particle fueling stays relatively const ant between the L-mode and the ELM-free H-mode phase immediately following the L-H transition. This indicates that in the ELM-free phase nearly all of the increase in plasma electron density comes from a decrease in the cross -field transport rate and an increase In the impurity influx. This result d iffers from conclusions of previous work in that the effects of the thinner H-mode scrape-off-layer do not appear to be as important in a plasma that is fueled primarily from divertor recycling as would be expected if the fue ling from limiter recycling were dominant. In both L-mode and PI-mode the c alculated core particle confinement times are less than, but within 50% of, the corresponding energy confinement times. (C) 2001 Elsevier Science B.V. All rights reserved.