In-situ studies of stainless steel exposed to hydrogen plasmas in the Lithium Tokamak Experiment (LTX)*

The Materials Analysis Particle Probe (MAPP) is an in situ characterization device for diagnosing samples exposed to fusion reactor plasmas. X-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS), thermal desorption spectroscopy (TDS) and direct recoil spectroscopy (DRS) will allow comprehensive shot-to-shot analysis of the samples. In the summer of 2013, MAPP was attached to a midplane port on LTX. The plasma-facing components (PFCs) in LTX are stainless steel, and MAPP enables evaluation of stainless steel samples before and after exposure to LTX plasmas. Initial studies compare XPS spectra from discharges with and without lithium PFC coatings. These results, combined with future measurements with TDS and ISS, provide unique insights into the relationship between the plasma behavior and the chemical structure of the first wall in fusion devices.