DESIGN OF THE 70-MM TWIN APERTURE SUPERCONDUCTING QUADRUPOLE FOR THE LHC-DUMP-INSERTION

The LHC dump insertion features a pair of superconducting quadrupoles located on either side of a 340 m long straight section. Two horizonta lly deflecting kickers, located in between the quadrupole pairs, and a septum in the centre of the insertion, vertically deflect the two cou nterrotating beams past the quadrupoles on the downstream sides, and i nto the dump areas. Due to the layout, the optical beta function in th e quadrupoles is around 640 m, the largest around the LHC at injection . The quadrupoles must therefore have enlarged aperture and specially designed cryostats to allow for the safe passage of both the circulati ng and ejected beams. In this paper we present the design of the twin aperture dump quadrupole based on the 70 mm four layer coil proposed f or the LHC low-beta quadrupoles. In preparation for model construction , we report on improvements of the coil design and a study of the reta ining structures.