Thermal design and analysis of DIII-D advanced divertor

The DIII-D tokamak uses divertor plasma configurations to obtain enhanced plasma confinement. To further develop the divertor capability, a combined divertor baffle and electrically isolated toroidal-ring electrode will be installed. The high heat flux and elevated temperatures pose challenging design problems, especially for the insulating materials. The toroidal-ring support structure for the divertor is described. It must withstand a peak heat flux of 600 W/cm ² for a period of 5 s. The results of a system analysis are presented. During operation, the advanced divertor is electrically biased relative to the vessel. To provide cross field electrical insulation between the divertor and the vessel, parts of the shelf and the floor tiles will be fabricated from nonconducting materials which will be subjected to both high heat flux and a high-temperature environment. To obtain an acceptable design, thermal analyses were performed to calculate the temperature differences between the divertor structure and the vessel wall during periods of bakeout and during plasma operation. A number of finite-element thermal stress analyses of individual components were done to ensure acceptable temperatures and stresses