Discharge resolved impurity flux measurements in the edge plasma of ASDEX Upgrade by exposure of collector probes

The exposure of collector probes using the ASDEX Upgrade midplane manipulator allowed to quantify the particle fluxes at the outer midplane. Time resolved measurements were carried out employing rotating cylindrical samples shielded by a narrow slit aperture. After exposure the retrieved probes were analyzed ex-situ using Rutherford back-scattering (RBS), nuclear reaction analysis (NRA) and proton induced X-ray emission (PIXE). Time resolved measurements allow to correlate impurity fluxes with well defined discharge conditions. Increased deposition is observed within the low density start-up phase as well as in configurations with small separatrix-sample distance and increased ICRH heating. Quantification of implanted deuterium as well as W and other impurity species was carried out and compared to spectroscopic data. Radial scans revealed an exponential fall-off of all species with radial decay lengths varying between ∼2.5 mm (Fe) and ∼6–10 mm (D). Also the origin of prominent impurities like Ca is clarified.