X-ray photoelectron studies on stainless steel (SUS 304) in a Heliotron E toroidal plasma confining device

This paper describes the chemical oxidization state of SUS 304 stainless steel samples in the divertor region with neutral beam injection heating (1.7 MW H0→H+) in a Heliotron E toroidal plasma confining device. X-ray photoelectron spectroscopy (ESCA) determined chemical compositions and oxidization stages in 17 channels stainless steel samples. It is found that a strongly sputtered divertor region is localized helically in a vacuum chamber. The FeO with 50 A depth is a major component of the sputtered divertor region. It is verified that impurity oxygen atoms are buried in titanium gettered surface. The main process is suggested to be that oxygen atoms are deeply trapped chemically in titanium oxide TiO2. (orig.)