ON THE DESIGN OF LIQUID-METAL DIVERTORS

The divertor technology has become the focus of concern for prospectiv e steady state tokamak reactors. The imposed heat flux and particle fl ux conditions cast doubt on the feasibility of any solid surface diver tor. The aim of this work is to evaluate the existing concepts of liqu id metal divertors from the physics, engineering, and safety points of view. Lithium metal is found to relatively suffer from a large tritiu m inventory that may develop in the form of solid hydride LiH, in addi tion to the fire hazard potential. Gallium does not form hydride withi n the temperature range of interest and is inactive with oxygen, there fore it is considered a more favorable metal. The flowing film and poo l type divertors are found to suffer from the possible blistering eros ion and resulting plasma contamination. The self-cooled liquid metal f ilm divertor suffers also from a linear MHD instability, in addition t o complicating factors such as the variation of the liquid metal elect ric property, dynamics of halo current, and the possible incompatibili ty with the insulator coating. The liquid gallium droplet curtain dive rtor appears to be the most feasible and robust, but its high temperat ure vapor is corrosive to most structural materials.