Divertor Plasma Physics Experiments On The Diii-D Tokamak

An overview is presented of the results and conclusions of the authors' most recent divertor physics and development work. Using an array of new divertor diagnostics, the plasma parameters were measured over the entire divertor volume and new insights into several divertor physics issues were gained. Direct experimental evidence for momentum loss along the field lines, large heat convection, and copious volume recombination during detachment is presented. These observations are supported by improved UEDGE modeling incorporating impurity radiation. Divertor exhaust enrichment of neon and argon by action of a forced scrape-off layer (SOL) flow and divertor pumping as a substitute for conventional wall conditioning were demonstrated. A divertor radiation zone with a parallel extent that is an order of magnitude larger than that estimated from a 1-D conduction limited model of plasma at coronal equilibrium was observed. Using density profile control by divertor pumping and pellet injection, H-mode confinement at densities above the Greenwald limit was attained. Erosion rates of several candidate ITER plasma facing materials are measured and compared with predictions of a numerical model.