Current State of Development and Expected Performance of Copper-Lithium Alloys as an Impurity Control System in Fusion Applications

Publisher Website
Google Scholar
Abstract
A new approach to impurity control involves the development of materials displaying both strong surface segregation of a low-Z component and high secondary ion fractions in the sputtering of that component. Key issues that have been studied with particular reference to copper-lithium alloys relate to the completeness of the overlayer, its rate of formation in a reactor environment, lowering of substrate sputtering and self-sputtering yields, durability of the overlayer, and depletion of the bulk alloy in the low-Z component. Other factors that must be considered in the materials selection process relate to response to disruptions, heat transfer, thermal stress, fabricability, radiation damage, activation, and tritium permeation. Copper-lithium alloys have been evaluated as a surface material for the impurity control system of the INTOR reactor. Both the medium-edge temperature limiter regime and the low-edge temperature divertor regime were examined. The analysis used TRIM code data to predict sputtering coefficients for copper-lithium with a 1.5 monolayer coverage of lithium. The REDEP code was used to evaluate the erosion performance for INTOR. Other properties such as fabrication and thermal performance were also briefly assessed. It was found from the standpoint of erosion that copper-lithium is a very good candidate material for the medium-edge temperature regime and also works well in the low-edge temperature regime. For the medium-edge temperature regime, the use of copper-lithium results in an almost negligible erosion rate over the entire surface.