Tracer techniques for the assessment of material migration and surface modification of plasma-facing components

•Tracer techniques were used in the TEXTOR tokamak to determine high-Z metal migration and the retention of species used for plasma edge cooling or wall cleaning under different operation conditions.•Volatile molybdenum hexa-fluoride, nitrogen-15 and oxygen-18 were used as markers in tokamak or ion cyclotron wall conditioning discharges (ICWC).•The objective was to obtain qualitative and quantitative of a global and local deposition pattern and material mixing effects.•The deposition and retention was studied on plasma-facing components, collector probes and test limiters.•Optical spectroscopy and ex-situ analysis techniques were used to determine the plasma response to tracer injection and surface composition modification.