Developing a Lithium-filled Capillary Porous System Tile for the Private Flux Region of NSTX-U

Our modeling has shown that lithium vapor injected into the private flux region of the outer divertor leg can be used to dramatically reduce the heat flux at the target in NSTX-U. Careful design of baffles and gas puffing can minimize the resulting lithium concentration in the main plasma. A stepwise approach is being taken to develop and test the critical pieces of technology needed to implement this concept in NSTX-U, as well as to understand the underlying physics. The first installation in NSTX-U is planned to be a single, pre-filled lithium tile in the private flux region of the lower divertor. The single-tile test will be used to validate models for lithium transport in the plasma and to demonstrate key elements of the technology required for a baffled, toroidally symmetric system. This presentation will provide an overview of recent activity on the design of the private flux region tile, testing of a custom high power-density heater designed to be embedded in the tile, and the selection of capillary porous materials.