ITER DIVERTOR RESEARCH-AND-DEVELOPMENT ACTIVITIES

One of the key challenges in designing the next generation tokamaks is the development of plasma facing components (PFC's) that can withstan d the severe environmental conditions at the plasma edge. The most int ensely loaded element of the PFC's is the divertor. The divertor must handle high fluxes of energetic plasma particles and electromagnetic r adiation without excessive impurity build-up in the plasma core. It mu st also remove helium ash while recirculating a large fraction of the unburned hydrogen fuel so that vacuum pumping requirements are not exc essive. The gas-dynamic mode of divertor operation proposed for ITER e xpands the divertor design window to include several alternate heat si nk and armor materials that were not feasible for the previous high re cycling divertor approach. In particular, beryllium armor can now be c onsidered with copper, niobium or vanadium structural materials cooled by liquid metal or possibly helium in addition to water. This paper p resents some of the results achieved under ongoing ITER Plasma Facing Components research and development tasks. The overall effort involves U.S. industry, universities and national laboratories and is directed towards developing and/or testing: (1) ductile beryllium and berylliu m joining techniques; (2) prototype divertor component design, fabrica tion and testing; (3) fiber-reinforced composites for beryllium and ca rbon; (4) beryllium plasma spray processes; (5) compliant layers for P FC armor attachment; (6) sacrificial armor layers for the divertor end -plates; and (7) tritium permeation and inventory in proposed PFC mate rials and components. The paper focuses on work being conducted by the industrial support team consisting of McDonnell Douglas Aerospace, Eb asco, General Atomics, Rocketdyne, University of Illinois and Westingh ouse.