Design of the C-Mod Advanced Outer Divertor

Operational requirements and research considerations make a high-temperature, toroidally continuous outer divertor an important aspect for future operation of the Alcator C-Mod tokamak. Leading edge melting of tiles, nonuniform heat loads, large electromagnetic forces, and localized impurity sources limit the performance of bulk plasmas. These issues can be addressed by the installation of a well-aligned, toroidally continuous outer divertor. In addition, future proposed long pulse operation of C-Mod will cause the temperature of the outer divertor to reach bulk temperatures as high as 500 °C-600 °C. This future operational requirement, combined with the strong temperature dependence of plasma surface interactions (especially fuel retention), makes a controllable, high-temperature outer divertor desirable and necessary. The design and development of the C-Mod advanced outer divertor is discussed.