Cleaning of contaminated XUV-optics at BESSY II

Carbon contaminations as observed on XUV-optics can be removed by an in situ plasma discharge process. The method developed at BESSY is based on waterfree oxygen/argon mixture and avoids water contamination of the UHV-equipment. dio frequency based plasma cleaning method has been used at several undulator beamlines at BESSY II with a gain in flux at the carbon K-edge. At the UE56-I-plane grating monochromator, a gain in flux up to a factor 20 is observed. No loss in flux has been observed across the whole energy ranges of the “cleaned” beamlines.