R & D of N[lc]b/C[lc]u clad seamless cavities at KEK

Abstract

Nb/Cu clad seamless superconducting rf cavities are proposed as a cost effective mass production for TESLA. This way can eliminate electron beam welding by applying spinning or hydro-forming in cavity fabrication, at the same time it reduces material cost remarkably by using rather thin niobium material. It keeps the niobium bulk property. Present high gradient preparation methods can be used, e.g., electropolishing, therefore this approach will guarantee the high gradient performance (greater than 30 MV/m). Since the first successful feasibility study by spinning technique in 1999, hard efforts on the R & D have been made. Recent international collaborative works with INFN-LNL, DESY and Thomas Jefferson Lab have developed the excellent potential on high performance. For a mass production, Cu/Nb/Cu sandwiched tubes have been successfully developed for hydro-forming, and 1,300 MHz mono cell cavities were successfully hydro-formed from the tubes in the collaborative work with Toshiba. KEK's own hydro-forming technique is also under developing.