Recent results from tokamak divertor plasma measurements

New diagnostics have been developed to address key divertor physics questions, including: target plate heat flux reduction by radiation, basic edge transport issues, and plasma wall interactions (PWIs) such as erosion. A system of diagnostics measures the target plate heat flux (imaging ir thermography) and particle flux (probes, pressure and Penning gauges, and visible emission arrays). Recently, Te, ne, and Pe (electron pressure) have been measured in two-dimensions (2D) with divertor Thomson Scattering. During radiative divertor operation Te is less than 2 eV, indicating that new atomic processes are important. Langmuir probes measure higher Te in some cases. In addition, the measured Pe near the separatrix at the target plate is lower than the midplane pressure, implying radial momentum transport. Bolometer arrays, inverted with reconstruction algorithms, provide the two-dimensional core and divertor radiation profiles. Spectroscopic measurements identify the radiating species and provide information on impurity transport; both absolute chordal measurements and tomographic reconstructions of images are used. Either intrinsic carbon or an inert species (e.g., injected Ne) are usually observed, and absolute particle inventories are obtained. Computer codes are both benchmarked with the experimental data and provide important consistency checks. Several techniques are used to measure fundamental plasma transport and fluctuations, including probes and reflectometry. PWI issues are studied with in situ coupons and insertable samples (DiMES). Representative divertor results from DIII-D with references to results on other tokamaks will be presented. copyright 1997 American Institute of Physics