Laser annealing of Nb coatings for superconducting RF accelerating cavities

The effects of laser annealing on niobium films sputter-coated on OFHC copper are reported. It is shown that single shots (40 ns, 5.5 J/cm2) of a XeCl excimer laser result in surface melting and recrystallization of the Nb film, and in turn in the complete removal of surface defects and in a large increase of grain size and RRR values. rocedure may be of practical interest to improve the performance of Nb-coated RF accelerating superconducting cavities, such as those produced for the LEP energy upgrade from 55 to about 90 GeV per beam.