Cryogenic Test Facility and the Indirect Pre-Cooling Method For HL-LHC MCBRD 4.5K Test At IMP

A Chinese group is collaborating with CERN in producing the HL-LHC MCBRD magnets (D2 corrector). Before delivery to CERN, the MCBRD magnets should be trained and cold tested at 4.5 K to check that the magnets are up to standard. To meet the requirements of cold testing, the IMP team made an upgrade plan for the existing cryogenic test facility and designed 4 m long anti-cryostats for the rotating coil. To control the temperature difference and avoid nitrogen contamination during the pre-cooling, the IMP team developed an indirect cooling method which can pre-cool the magnet with LN ₂ by radiation and convection through gaseous helium. With this method, the LN ₂ does not touch the magnet and even not need a circulation of the cold helium gas. The first Chinese produced magnet which is called MCBRDP2 has been tested on this stand. The details of the cryogenic test facility, the indirect cooling method, and their performances during MCBRDP2 cold testing are discussed in this paper.