Design and fabrication of the ALT-II limiter blades

Abstract

The ALT-II limiter blade must operate in heavy thermal and mechanical loading caused by the TEXTOR plasma, making it necessary to perform material selection and design carefully for the tiles and base plates in order to fulfill the physics and engineering objectives. In material selection for the tiles, requirements of low Z character, vacuum compatibility and fracture toughness, etc. should be considered, and purified isotropic graphite was selected. The base plates should meet the requirements of high dimensional accuracy for the three-dimensional shape, high temperature resistance, and sufficient mechanical strength against off-normal conditions such as plasma disruptions. Incone1 625 was adopted as the base plate material. Easy maintenance is also a very important item to be considered for the blade design, because one of the characteristic features of the TEXTOR device is easy replacement of in-vessel components. Besides the physics and engineering considerations, the managerial viewpoint to keep the schedule of fabrication was important, since the ALT-II project was an international collaboration including hardware manufacturing. Through the great efforts of the participants, communications between the TEXTOR operating agent, US and Japan was excellent, and the project was going on very smoothly and successfully.