MEASUREMENT AND MODELING OF THE DIII-D DIVERTOR PLASMA

We report here on a study of the DIII-D divertor plasma which combines experimental measurements and 2D plasma modeling using the Braams 82 code. New data from a set of Langmuir probes recently installed in the divertor are presented. These data complement divertor heat flux measurements and help to better characterize divertor operation in neutral-beam heated discharges. In L-mode plasmas we find that the electron temperature rises with beam power (up to 45 eV with P(beam) = 5 MW) and is a strong function of nBAR(e). The peak divertor heat flux rises linearly with power and develops a strong inboard/outboard asymmetry which depends upon the toroidal field direction. Such behavior is not seen in the B2 simulation results. Following the H-mode transition the divertor heat flux, plasma density and temperature remain low even as the main plasma density rises.