Integration of the 11-T Nb3Sn Dipoles and Collimators in the LHC

The Large Hadron Collider (LHC) collimation system upgrade plan comprises new collimators in the dispersion suppressors. The length required for each collimator along the LHC lattice is obtained by replacing an LHC main dipole and its cryostat with two shorter but stronger 11-T Nb
₃
Sn magnets keeping the equivalent integrated field of the dipole removed. This requires a modification of the continuous cryostat, in order to create room-temperature beam vacuum sectors for the integration of the new collimators. In this paper, we present a new cryostat designed to allow the installation of a collimator between the 11-T magnets, while ensuring the continuity of the cryogenics, vacuum, and magnet powering systems of the LHC continuous cryostat. Challenging constraints, in terms of fabrication, alignment, and space, led to the development of a cryostat composed of three independent modules. Two of the modules house the 11-T dipole cold masses, which are cooled in the same 1.9-K pressurized superfluid helium bath of the main dipoles. These make use of the same design features of the LHC magnet cryostats, in order to contain construction and assembly costs and benefit from well-established procedures. A third module, which is placed between the two magnets, is equipped with cold to warm transitions on the beam lines and creates the space for the collimator between the vacuum vessel of the two 11-T magnet cryostats. The main functionalities, requirements, and implemented design solutions for this new cryostat are presented and discussed, in the context of the challenging integration in the LHC continuous cryostat and its tunnel.