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High normal current fluences have long been reported to produce major changes in the x-ray diffraction pattern of YBa 2 Cu 3 O 7−x (YBCO). These x-ray diffraction effects have now been shown to result from the removal of barium from the YBCO near-surface lattice together with the formation of a thin barium oxide overlayer. Neutron diffraction reveals that the bulk crystallographic structure remains unaltered by charge fluences of more than 40 million C/cm 2 , and Auger electron spectroscopy confirms the presence of surface barium enrichment.

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