Design Challenges for a Wide-Aperture Insertion Quadrupole Magnet

Abstract

Abstract-The design and development of a superconducting (Nb-Ti) quadrupole with 120-mm aperture, for an upgrade of the LHC insertion region, faces challenges arising from the LHC beam optics requirements and the heat-deposition. The first triggered extensive studies of coil alternatives with four and six coil-blocks in view of field quality and operation margins. The latter requires more porous insulation schemes for both the cables and the ground-plane. This in turn necessitates extensive heat propagation and quench-velocity studies, as well as more efficient quench heaters. The engineering design of the magnet includes innovative features such as self-locking collars, which will enable the collaring to be performed with the coils on a horizontal assembly bench, a spring-loaded and collapsible assembly mandrel, tuning-shims for field quality, porous collaring-shoes, and coil end-spacer design based on differential geometry methods. The project also initiated code extensions in the quench-simulation and CAD/CAM modules of the CERN field computation program ROXIE.Index Terms-Low-beta insertions, magnet design, superconducting quadrupole.

Testing Results for Nb-Ti, 120-mm-Aperture, Low-B Quadrupole Models for the LHC High-Luminosity Insertion

“…Non-allowed multipoles are pretty good, with only two components (a 3 and a 4 ) above one unit. A magnetic shimming [3] has been proposed to improve field quality. Eight 8-mmdiameter holes, located in the collars, at 105 mm from the magnet center and at 30° from the coil mid-plane can be filled with magnetic rods.…”

“…OR the phase-1 luminosity upgrade of the Large Hadron Collider at CERN, a development program was started in 2007 in collaboration with CEA Sacly to develop a (Nb-Ti) 120 mm aperture quadrupole with a gradient of 120 T/m and the ability to extract very high heat loads on the order of 500 W. This quadrupole, called MQXC [1][2][3][4] had the innovative feature of a insulation scheme allowing a direct path from the helium bath to the superconducting strands [5]. Subsequently it was decided to move directly to the phase-2 insertion design requiring Nb 3 Sn technology and larger apertures.…”

“…Subsequently it was decided to move directly to the phase-2 insertion design requiring Nb 3 Sn technology and larger apertures. MQXC was needed for a backup technology in case the Nb 3 Sn magnet could not achieve the design targets and reliability within a relatively short time scale of about10 years. Moreover, the high heat load technology for the Nb-Ti magnet is a feature required for future magnets in the matching sections, namely the separation dipoles D1 and D2, the two/in/one quadrupole Q4 and several correctors [6,7].…”

Engineering Design and Manufacturing Challenges for a Wide-Aperture, Superconducting Quadrupole Magnet

“…Quench simulation has shown that for 10-m-long magnets, quench heaters are mandatory for magnet protection [6]. In order to quench as many conductors as possible, the quench heater strips were moved to the space between the inner and the outer coils, thus making contact to both coils.…”

“…G.A.Kirby, corresponding author, e-mail Glyn.Kirby@cern.ch revised operational schedule, and the performance limitations imposed by a minimum * of 30-40 cm (if only changing the triplets and separation dipoles) [6], the project was re-scoped in 2010. The baseline is now to concentrate on one single upgrade at a later stage around 2020, which will allow studying the potential of Nb 3 Sn superconductor technology and a mitigation of the above-mentioned constraints.…”