Properties of co-deposited layers on graphite high heat flux components at the TEXTOR tokamak

The objective of this work was to examine the structure, composition and properties of co-deposited films from the TEXTOR tokamak. Hydrogenated films formed on the toroidal belt pump limiter (ALT-II), and on the ICRF antenna grill were studied using a set of material analysis techniques. Plasma edge diagnostics were used to assess the parameters influencing the film formation during discharges auxiliary heated by ICRF. The essential results are summarized as follows: (i) the distribution of plasma impurities co-deposited in the films is non-uniform and (ii) the surface topography, crystallographic structure, fuel retention and composition (i.e., content of re-deposited plasma impurities) of the films show significant diversity depending on the location where they were formed. These differences are associated with the local geometry, the tokamak operation scenarios and the resulting plasma edge properties.