Analysis and oxidation of thick deposits on TEXTOR plasma facing components

Deuterium and hydrogen containing co-deposited layers formed on plasma facing components at the TEXTOR tokamak were characterised by a number of techniques including surface analysis methods and thermal desorption spectrometry. The aim of the investigation was to determine the composition and structure of the layers prior and after their exposure to air at elevated temperatures of 300 degrees C and 550 degrees C. The impact of the oxidation on the deuterium content and distribution in the surface region and in the bulk of PFC was addressed. The initial deuterium-to-carbon concentration ratio was in the range 0.04-0.06 in the flaking layers on top of the PFC and up to 0.17 on their side surfaces. The oxidation at 300 degrees C for 2 h resulted in partial removal of the deuterium, especially from thin or loosely bound layers, but the release was not accompanied by the change in the deposit structure. The content of plasma impurity atoms in the layers was also not influenced by the exposure to air. Following the oxidation at 550 degrees C partial powderisation of thick, flaking films was observed. (C) 1999 Elsevier Science B.V. All rights reserved.