Superconducting Nb3Sn-cavities

Microwave critical magnetic flux densities Bc^acup to 160 mT and higher than Bc1were obtained with niobium-cavities by special surface treatments. Breakdown in this flux density region occurs by a thermal breakdown mechanism in which no superconducting critical flux density is involved. Considerable increase in Bc^acmay be expected with high-Tc-superconductors such as Nb3Sn. Nb3Sn-layers were produced on niobium structures by exposing them to a saturated Sn-vapour at 1000 °C. Bc^ac-values up to 40 mT and surface resistances smaller than 10^-6Ω were measured with TE011-cavities at 9.5 GHz.