Neon Plasma Can Clean Fusion Reactor Walls at 800°C

Scientists have demonstrated a new way to clean critical fusion-reactor materials without opening the vacuum chamber or exposing them to air. Researchers from the Princeton Plasma Physics Laboratory, Princeton University and Pennsylvania State University tested the technique inside the Lithium Tokamak Experiment-Beta, or LTX-β. The method combines a low-temperature neon glow discharge with intense heating of porous tungsten samples to roughly 800°C. Why is this important? One promising approach for future fusion reactors uses porous tungsten components filled with liquid lithium. The tungsten behaves almost like a metallic sponge, allowing lithium to move through microscopic pores while protecting plasma-facing surfaces. But there is a problem. During manufacturing and handling, carbon, oxygen and other contaminants accumulate on the tungsten. When liquid lithium interacts with these impurities, solid compounds can form and block the pores, reducing lithium flow and degrading the performance of the plasma-facing material. Cleaning the components before installation is not enough because exposure to air can contaminate them again. So the researchers tried something different: clean the tungsten after it had already been installed inside the vacuum system. Highly contaminated porous tungsten samples were placed inside LTX-β and exposed to a neon glow discharge. The samples were then rapidly heated. The combination proved significantly more effective than plasma cleaning alone. After treatment, the fraction of clean metallic tungsten visible at the surface increased from essentially zero to 87%, while carbon contamination dropped sharply. The change was even visible to the eye: the samples went from a dull dark gray appearance to a bright metallic silver. Why neon? Neon ions are heavier than ions from gases such as helium. When they strike the tungsten surface, they can more effectively knock away carbon and oxygen contaminants. Heating plays another role by helping contaminants escape from deeper inside the porous structure so the plasma can remove them. The study was published in Nuclear Materials and Energy under the title “Testing of spark plasma sintered porous tungsten under neon glow discharge cleaning conditions in LTX-β.” The experiments also used in-vacuum analysis techniques to study how the chemical composition changed after treatment. This matters because liquid-metal plasma-facing components are being studied as one possible way to handle the enormous thermal loads inside future fusion systems. If engineers can clean and restore porous tungsten components without opening the reactor vacuum vessel, maintenance could become simpler and contamination could be reduced. However, this is still an experimental materials study. The researchers tested tungsten samples inside LTX-β; they have not yet demonstrated an automated cleaning cycle for the complete walls of a commercial fusion power plant. Even so, the experiment provides a framework for developing in-situ cleaning procedures for future reactors using liquid lithium and porous tungsten. Sometimes the path toward practical fusion energy is not only about making hotter plasma. It is also about finding better ways to keep the machine itself working. Subscribe to Xenon Lab News for more fusion energy, physics and future technology breakthroughs. #NuclearFusion #FusionEnergy #NeonPlasma #Tungsten #Tokamak #PPPL #Princeton #PlasmaPhysics #LiquidLithium #FusionReactor #CleanEnergy #FutureEnergy #NuclearPhysics #ScienceNews #FutureTechnology #TechNews #XenonLabNews