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

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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.