SCRAPE-OFF LAYER MODELING OF RADIATIVE DIVERTOR AND HIGH HEAT-FLUX EXPERIMENTS ON DIII-D

We use a new multispecies 1D fluid code, NEWT-ID, to model DIII-D scrape-off layer (SOL) behavior during radiative divertor and high heat flux experiments. The separatrix location and the width of the SOL are uncertain, and affect the comparison of the data in important ways. The model agrees with many of the experimental measurements for a particular prescription for the separatrix location. The model cannot explain the recent data on the separatrix T(i) with a conventional picture of ion and electron power flows across the separatrix. Radial transport of particles and heat in some form is required to explain the peak heat flux data before and after gas puffing. For argon puffing in the private flux region, entrainment is poor in the steady state. The calculations suggest that strike point argon puffing in a slot divertor geometry results in substantially better entrainment. Self-consistent, steady-state solutions with radiated powers up to 80% of the SOL power input are obtained in 1D. We discuss significant radial effects which warrant the development of a code which can treat strongly radiating impurities in 2D geometries.