Surface Treatment of a Lithium Limiter for Spherical Torus Plasma Experiments

Abstract

The concept of a flowing lithium first wall for a fusion reactor may lead to a significant advance in reactor design, since it could virtually eliminate the concerns with power density and erosion, tritium retention, and cooling associated with solid walls. As part of investigations to determine the feasibility of this approach, plasma interaction questions in a toroidal plasma geometry are being addressed in the Current Drive eXperiment -Upgrade (CDX-U) spherical torus (ST). The first experiments involved a toroidally-local lithium limiter (L3). Measurements of pumpout rates indicated that deuterium pumping was greater for the L3 compared to conventional boron carbide limiters. The difference in the pumpout rates between the two limiter types decreased with plasma exposure, but argon glow discharge cleaning was able to restore the pumping effectiveness of the L3. At no point, however, was the extremely low recycling regime reported in previous lithium experiments achieved. This may be due to the much larger lithium surfaces that were exposed to

Performance of liquid-lithium-filled 3D-printed tungsten divertor targets under deuterium loading with ELM-like pulses in Magnum-PSI

“…Based on earlier experiments the performance of 3Dprinted tungsten CPS seems highly promising. The finely textured PFS is highly stable and can be shaped in any geometry, unlike CPS made from fine mesh layers which must in practice almost always be mounted around convex surfaces [15,20,21]. However, previously the Li-loaded 3D-printed targets were loaded with quasi steady-state helium plasmas, while in a fusion reactor the predominant plasma ion species will be deuterium and tritium, and phenomena such as ELMs may create transient power excursions at the divertor targets.…”