Nb- and Nb3Sn-cavities produced by sheet material

X-band TM010cavities have been fabricated from Nb sheets by spinning and welding together. Studies of different surface preparations have shown that smooth surfaces and relatively good RF properties can be obtained by a simple chemical polishing treatment. Also the degradation caused by welding can be overcome by chemical polishing without any heat treatment. On welded TM010cavities critical flux densities of more than 70 mT and high-field Q-values of 5.10⁹have been measured. Up to this field level no electron loading was observed. This procedure is very promising for the fabrication of Nb cavities for technical applications as well as of substrates for Nb3Sn cavities.