First operational experience of the upgraded cryogenic infrastructure of the vertical magnet test facility in the SM18 hall, including HFM and cluster D test stations.

As part of the R&D; program for HL-LHC, the future upgrade of the Large Hadron Collider (LHC), the vertical magnet test facility in the SM18 cryogenic test hall at CERN has seen significant development. Since the installation of HFM and Cluster D cryogenic test stations in 2017, the facility is comprised of five vertical test cryostats of various sizes operating at either 1.9 K or 4.2 K. It is now possible to test a wide range of superconducting high field magnets with weigh up to 18 tons, maximum stored energy of 10 MJ and powering requirements up to 30 kA. This article describes the first cryogenic operational experiences with these test stations, their cool-down and warm-up characteristics and the heat in-leak measurements of their components. Major upgrades made to the cryogenic infrastructure of the vertical magnet test facility as a whole are also detailed. This includes the adoption of an improved safety strategy to ensure the continued safe operation of the test facility during all operational modes. As well as the incorporation of quench recovery systems on four of the five test stations to reduce the amount of helium lost during testing and the installation helium guards on infrastructure operating at 1.9 K to avoid the ingress of air to cryogenic circuits.