X-ray photoelectron spectroscopy (XPS) studies of oxygen and carbon bonding to tokamak walls

Abstract

The binding energies of surface atoms of stainless steel samples exposed to hydrogen plasma discharges in PDX are measured using x-ray photoelectron spectroscopy. After glow discharge conditioning the O1s line is completely shifted to a higher binding energy which is an indication of the formation of hydroxides. The Fe2p lines show a partial reduction of iron. After high power discharges, the oxygen concentration increases and the binding energy of the deposited O atoms corresponds to a metallic oxide. The deposited limiter material Ti is also completely oxidized. For both kinds of discharges the binding energies of Cr2p and C1s remain essentially unmodified.