Physical erosion studies of plain and lithiated graphite

It has been observed that a thin lithium film evaporated on graphite wall tiles in tokamak fusion devices acts to improve plasma conditions. The present focus is to measure the physical erosion rate of various conditions of lithiated graphite under deuterium ion bombardment to help understand this effect. Sputter yields on untreated ATJ-graphite, pure lithium, and lithium-on-ATJ-graphite have been measured for 150, 300, 600 and 1500 nm of evaporated lithium, at an ion energy of 500 eV/ion, 45° incidence, and sample temperatures of 25 and 200 °C by using a QCM to collect the sputtered material. Sputter yields for untreated graphite were measured around 0.06 C-atoms/ion, while yields for pure lithium were around 0.10 Li-atoms/ion. However, combined lithium-on-carbon sputtering yields appeared notably lower than yields for the individual materials. TOF-SIMS analysis was used to estimate relative Li/C levels in collected sputtered material, as well as to look at the concentration versus depth of intercalated lithium in graphite.