Recent Results from the Actively Pumped Open-surface Lithium Loop (APOLLO)

Flowing liquid lithium Plasma Facing Components (PFCs) offer an attractive solution to the issues faced at the first wall and divertor regions in tokamaks. Lithium is low Z, getters impurities and reduces hydrogen recycling. However, this uptake of hydrogenic species in the lithium flow, especially tritium, raises operational issues in pilot plants due to stringent limitations on inventory. To address these concerns, the Center for Plasma–Material Interactions (CPMI) designed and constructed the Actively Pumped Open-surface Lithium LOop (APOLLO). APOLLO contains an open-surface PFC inside a magnetic field, capability for either deuterium plasma or electron beam exposure and will ultimately install a distillation column to recapture hydrogenic species from the lithium flow. As of July 2024, testing of a new distributor produced near uniform lithium flow across its outlet, flow in the loop was achieved for 24 continuous hours and the lithium flow was able to be frozen and restarted three times allowing for a cumulative runtime of 60 hours.

This abstract will give an overview of the most recent results and work from APOLLO including the installation and characterization of an Electron Cyclotron Resonance (ECR) plasma source, heat flux measurements from the electron beam and the design and manufacture of a 3D ordered foam flow plate for ThermoElectric MagnetoHydro-Dynamic (TEMHD) drive. The talk will also outline the plans for APOLLO which comprise of the design of a distillation column and its incorporation into the loop, testing of diagnostics to measure hydrogen content in flowing lithium and the development of supporting components to further the technology readiness of liquid lithium as a PFC.