Design and fabrication of a 1 m model of the 70 mm bore twin aperture superconducting quadrupole for the LHC insertions

For reasons of geometrical acceptance, 70 mm bore twin aperture quadrupoles are required in the LHC insertions. For an operating gradient of 160 T/m a t 4.5 K, a design based on a four layer coil wound from two graded 8.2 mm N bTi conductors has been developed. Three I m single aperture quadrupoles of this design have been built and successfully tested. Thereafter, the magne ts have been disassembled and the coils recollared using self-supporting co llars. In this paper, we describe the design features of the twin aperture quadrupole, and report on the initial collaring tests and procedures for co llaring and final assembly of the 1 m magnet.