Evolution of Evaporative Coatings of Lithium from LTX-$\beta $ with Temperature and Their Analysis with XPS and LEIS*

Plasma-material interactions (PMI) strongly influence lifetimes of plasma facing components (PFCs) and plasma performance. The choice of low-Z PFCs such as lithium (Li) offer attractive features such as lower radiative power loss and the possibility to operate in a flat temperature profile regime, as demonstrated by evaporative coatings on LTX-$\beta $. We present X-ray photoelectron spectroscopy (XPS) and low energy ion scattering spectroscopy (LEIS) analysis of witness samples using the Sample Exposure Probe (SEP), a portable ultrahigh vacuum (UHV) chamber, which introduces samples to LTX-$\beta $. These witness samples can then be transported to a surface analysis station. Li coatings on witness samples are then analyzed using XPS and LEIS to make observations on the effects of the LTX-$\beta $ environment on the first wall. The combined XPS and LEIS illustrate the oxidation of the Li coatings, forming Li$_{\mathrm{2}}$O and LiOH on top of evaporatively coated Li. The evolution of these oxides has a strong temperature dependence. We present XPS and LEIS analysis of these witness samples and how they evolve with temperature.