Conceptual design of the cryostat for the new high luminosity (HL-LHC) triplet magnets

The High Luminosity LHC (HL-LHC) is a project to upgrade the LHC collider after 2020-2025 to increase the integrated luminosity by about one order of magnitude and extend the physics production until 2035. An upgrade of the focusing triplets insertion system for the ATLAS and CMS experiments is foreseen using superconducting magnets operating in a pressurised superfluid helium bath at 1.9 K. This will require the design and construction of four continuous cryostats, each about sixty meters in length and one meter in diameter, for the final beam focusing quadrupoles, corrector magnets and beam separation dipoles. The design is constrained by the dimensions of the existing tunnel and accessibility restrictions imposing the integration of cryogenic piping inside the cryostat, thus resulting in a very compact integration. As the alignment and position stability of the magnets is crucial for the luminosity performance of the machine, the magnet support system must be carefully designed in order to cope with parasitic forces and thermo-mechanical load cycles. In this paper, we present the conceptual design of the cryostat and discuss the approach to address the stringent and often conflicting requirements of alignment, integration and thermal aspects.