Fusion applications for lithium: wall conditioning in magnetic confinement devices

The application of lithium to plasma facing components (PFCs) has been widely used to improve plasma performance in magnetic confinement devices. The ability of lithium to retain hydrogen isotopes has been exploited to lower wall recycling. Low recycling leads to high edge plasma temperatures, and decreased temperature gradients reduce the free energy source for microinstabilities that cause transport. A variety of techniques have been developed to introduce lithium into fusion research devices, and its beneficial effects have been observed in their plasmas. The mechanism for the retention of hydrogen isotopes has been elucidated by detailed surface science studies, and 'first principles' molecular dynamics simulations. The remaining challenges primarily pertain to long pulse operation. Our knowledge of erosion, transport, and redeposition needs to improve for the mixed material PFCs lithium creates. Flowing liquid lithium systems also must be demonstrated for the replenishable lithium walls that fusion reactors require.