Search

The phenomena that lead to the observed power and particle flux detachment have been studied with the code B2-Eirene for DIII-D Helium and Deuterium experiments. Contrary to the usual Deuterium experiments, a significant reduction of the power load to the divertor is observed in Helium discharges while the ion flux remains high. Modelling indicates that this is due to the longer ionisation mean free path of Helium, which can penetrate from the divertor into the bulk plasma with the consequent power loss. At this stage of Helium detachment, most of the outer divertor plasma remains at an electron temperature of ∼5-10 eV, for which Helium recombination does not occur.

A comprehensive set of experiments has been carried out on the DIII-D tokamak to measure the 2-D (R,Z) structure of the divertor plasma in a systematic way using new diagnostics. Measurements cover the divertor radially from inside the X-point to the outer target plate and vertically from the target plate to above the X-point. Identical, repeatable shots were made, each having radial sweeps of the X-point and divertor strike points, to allow complete plasma and radiation profile measurements. Data have been obtained in ohmic, L-mode, ELMing H-mode, and reversed B{sub T} operation ({gradient}B drift away from the X-point). In addition, complete measurements were made of radiative divertor plasmas with a Partially Detached Divertor (PDD) induced by D{sub 2} injection and with a Radiating Mantle induced by Impurity injection (RMI) using neon and nitrogen. The data set includes first observations of the radial and poloidal profiles of the X-point, inner and outer leg plasmas in PDD and RMI radiative divertor operation. Preliminary data analysis shows that intrinsic impurities play a critical role in determining the SOL and divertor conditions.

Chemical vapor deposition (CVD) was used to deposit silver films for superconducting wire applications. AgI, silver trifluoroacetate (Ag(TFA)), and perfluoro-1-methylpropenylsilver (Ag(PF)) produced the most promising silver films. CVD processing was optimized on these three precursors using thermodynamic calculations performed using a modified version of the SOLGASMIX-PV computer program. Ag(PF) produced the highest quality silver films at low temperatures and pressures. A fiber tow which contained a silver barrier layer and a YBa2Cu3Ox overlayer was found to be a superconductor at 72 K.