Study of liquid metal film flow characteristics under fusion relevant magnetic field conditions

The use of thin, fast flowing liquid metal films as the divertor surface is a very attractive option for effective particle pumping and surface heat removal. The major "show-stoppers" for such a design concept are the magneto-hydrodynamic (MHD) effects associated with the flow, due to the presence of strong magnetic fields that vary spatially and temporally. This paper reports the preliminary experimental findings on the liquid metal free surface film flows under magnetic field conditions, similar to those experienced at the outboard divertor region of the NSTX machine at PPPL. The main goal of the study is to understand the MHD features associated with the flow, with emphasis on the variation of film thickness in the stream-wise and span-wise direction, as well as film surface stability. This study forms a part of a larger research effort at UCLA, directed towards providing qualitative and quantitative data on the liquid metal film flow behavior and identifying design constraints for the implementation of a liquid surface divertor module in NSTX.