The CERN Nb/Cu Programme for the LHC and Reduced-b Superconducting Cavities

The niobium/copper (Nb/Cu) sputter technology, successfully used on a large scale for LEP2, has been applied to the LHC and reduced-b superconducting (SC) cavities. For the LHC RF system the SC cavities were chosen, not only because of their high accelerating field leading to a small contribution to the machine impedance, but also because of their high stored energy which minimizes the effects of periodic transient beam loading associated with the high beam intensity (0.5 A). There will be eight single-cell cavities per beam, each delivering 2 MV (5.3 MV/m) at 400 MHz. In this paper the results of the industrial production of 21 cavities will be presented, and high-power test results on the prototype cryomodule reported. For the reduced-beta application an R&D programme at CERN was started in 1996. The goal is to demonstrate both the feasibility of such cavities and the possibility of producing them by low-cost modifications of LEP2 cavities (once LEP is decommissioned. Four different geometries were extensively tested (b = 0.48, 0.62, 0.66 and 0.8). In the present paper results obtained with single and multicell cavities will be presented, and a possible scenario for a superconducting proton linac will be reported.