Particle control in steady state magnetic fusion reactors by solid and liquid lithium plasma-facing components

Hydrogen and helium recycling behaviour from solid and liquid lithium has been observed with optical spectroscopy focused on H-alpha and He (I) in a newly built facility: VEHICLE- 1 (the Vertical and Horizontal positions Interchangeable test stand for Components and Liquids for fusion Experiments). The plasma density and electron temperature in VEHICLE- I are of the order of 10(10) cm(-3) and around 4 eV, respectively. The ion bombarding energy is varied from the floating potential to 100 V, applying negative dc bias voltages on lithium targets. The lithium temperature range is from 30 to 300 degrees C. It has been found that hydrogen recycling from standing liquid lithium is significantly reduced, compared with that from solid lithium, presumably due to the formation of lithium hydride particulates that can be transported beyond the implantation depth. In contrast, despite its chemical inertness, helium recycling from both moving and standing solid lithium at room temperature has been found to be noticeably reduced, relative to that from liquid lithium. Lattice imperfections in solid lithium appear to play an important role in reducing steady state helium recycling.