Plasma Source Development for a Flowing Liquid Lithium Loop

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, can getter 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 this issue, the Center for Plasma–Material Interactions (CPMI) is developing a recirculating lithium loop containing a free surface PFC. An Electron Cyclotron Resonance source producing a deuterium plasma will be installed allowing for the uptake of deuterium at the lithium PFC and its subsequent transport to be characterized. A 2.45GHz, 3kW magnetron will be used to launch microwaves through a vacuum microwave window into the chamber containing the PFC. To characterize the plasma a custom manufactured diagnostics plate will be installed in the same location as the lithium PFC prior to its operation. This plate consists of an array of 18 Langmuir probes, a retarding field energy analyzer, a radical probe and 4 thermocouples. Supplementing the internal plasma analysis, a wide band spectrometer and 4 filterscopes will be installed with line of sight to the plasma region in front of the plate. This will allow for a range of analysis techniques to be performed such as actinometry, Boltzmann plots and Voigt fitting. This presentation will give an overview of the plasma source, outline the analysis methods and touch on the design of the loop and initial operation.