Erosion behavior of lithium coated tungsten fuzz samples under D and He ion irradiation

As the primary candidate for the ITER divertor, tungsten (W) should be tailored to produce a more radiation tolerant plasma facing component (PFC). This alteration must overcome the surface microstructure changes such as bubbles, pores, fuzz, etc. that form under D and He ion irradiation in order to reduce tungsten erosion from the ITER divertor. Studies have shown that adding low Z impurities (C and Be) to a mixed D-He plasma can inhibit the growth of fuzz [1]. In contrast, previous studies have shown that low Z lithium (Li) does not inhibit fuzz production but does appear to persist on the surface among the fuzz. To further investigate this, we exposed $\sim$1000 nm Li coatings on a fuzz coated W to D and He ion bombardment. The erosion yield was measured with a quartz crystal microbalance and surface chemical changes were measured in operando with our HP-XPS system IGNIS (Ion-Gas-Neutral Interactions with Surfaces) at UIUC. Helium and D ion fluxes were $\sim$10$^{18}$ m$^{-2}$s$^{-1}$ at room temperature. After irradiation, the surfaces of the samples were characterized with scanning electron microscopy (SEM). These results will be presented along with SIMS results investigating the concentration depth profiles. [1] M.J. Baldwin et al., J. Nucl. Mater. 390–391 (2009) 886–890