Oxygen impurity analysis by collector probe measurements in the carbonized TEXTOR tokamak

Rutherford backscattering spectroscopy and nuclear reaction analysis techniques were used to determine the concentration of oxygen, metals and deuterium in the surface region of collector probes exposed to the plasma discharges in the carbonized TEXTOR fusion device. This paper focuses on time- and space-resolved measurements of oxygen collected during 13 tokamak shots on three cylindrical graphite probes placed near to the plasma boundary. Each probe was exposed to several discharges. Generally, the areal concentration of oxygen was found to be 15-25 times higher than that of metals and about 5-8 times lower than that of trapped deuterium. The influence of ICR heating, plasma density and other plasma parameters upon the deposition rate of oxygen and other species are discussed. The possible chemical state of the deposited oxygen is considered. (orig.)