STUDY OF SUPERCONDUCTING NB COATED 1.5-GHZ ACCELERATING CAVITIES

Single cell 1.5 GHz niobium coated accelerating cavities have been developed. Nb film was deposited by cylindrical magnetron sputtering. The film deposited onto the cavities was analyzed by SNMS for depth profile composition and by XRD for microstructure. Critical temperature (Tc) and residual resistance ratio (RRR) of the films were investigated on Al2O3 samples, giving (9.25 +/- 0.05) K for Tc and 14.5 for RRR. First results of RF measurements on coated cavities showed superficial resistance values in the mu Omega range. Possible superficial resistance sources are discussed