Lithium operations on the lithium tokamak experiment

The lithium tokamak experiment (LTX) is a small spherical tokamak currently operating to investigate the low recycling regime for magnetically confined plasmas through the utilization of liquid lithium coated plasma facing surfaces. The LTX machine is unique in that it incorporates inside the vacuum vessel a heated conducting shell that encloses about 80% of the last closed flux surface of the plasma. The conforming shell operates at temperatures up to 500°C and is coated with a thin liquid lithium film. Two retractable crucible evaporators are used to deposit the lithium film on the shell inner surfaces. Various methods and procedures for lithium deposition onto the shell surfaces have been tested by varying the component temperatures and vessel pressure, and utilizing concurrent glow discharge. Operating procedures and safety systems have been developed and implemented to ensure the safe operation with lithium at elevated temperatures. The machine has successfully operated with lithium coated shells demonstrating improved plasma performance as a result. Maintaining an active lithium surface between lithium evaporations was an issue and new features are currently being installed to address this. The machine has also been vented and the internal surfaces cleaned without any difficulty. Operating results, current status, ongoing upgrades and future plans will be presented.