The Cryogenic Distribution System for the High Luminosity LHC upgrade at CERN

Abstract The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) will require the replacement of the final focusing superconducting magnets, the implementation of new superconducting links to power the magnets and the implementation of new Superconducting Radio-Frequency (SRF) crab cavities, totalling a length of about 150 m on both sides of the collision points of the ATLAS (P1) and of the CMS (P5) experiments in the LHC accelerator. To cool the new and reconfigured cryogenic devices, a new Cryogenic Distribution System will replace the existing LHC cryogenic distribution line on each side of the experiments. Two multi-header cryo-distribution lines (QXL) for each of P1 and P5 will transfer helium at different temperature levels, pressures, and mass flows between the HL-LHC machine components and new helium refrigerator located in a cavern next to the LHC tunnel. The QXL system, manufactured and installed by industry on the basis of CERN detailed specification, will have a total length of approximately 1.5 km and will be installed in two phases, first in the underground service galleries and then in the LHC tunnel. This paper first describes the cryogenic configuration of the new equipment of the HL-LHC machine and the main functional requirements of the QXL. The cryogenic parameters for the different circuits and operation modes are presented. The paper emphasizes the architecture of the cryogenic distribution system, the conceptual design of its main components and its integration in the HL-LHC environment.