Figure 1. Cryomagnet assembly layout around the HiLumi LHC interaction points of ATLAS (Point 1) and CMS (Point 5). Q1 and Q3 cryoassemblies each contain two niobium-tin quadrupoles; Q2a and Q2b each contain a niobium-tin quadrupole and an orbit corrector magnet (MCBXFB); the corrector package (CP) contains an orbit corrector (MCBXFA) and 9 higher-order correctors; D1 contains a niobium-tin dipole; the D2 contains a dipole (MBRD) and 2 orbit correctors (MCBRD). The flags represent the countries of the related collaboration institute. Edited from figure by Ezio Todesco / CERN.
By Gerard Willering, Susana Izquierdo Bermúdez, and Florence Thompson (CERN)
Over half of the new horizontal cryomagnet assemblies required for installation in the High-Luminosity LHC (HiLumi LHC) have been qualified for tunnel deployment, giving confidence in the project’s progress as we speed towards Long Shutdown 3, when major installation works for the upgraded collider will take place.
Cryomagnet assembly qualification
28 new HiLumi LHC cryomagnet assemblies – comprising a total of 88 magnets – must be installed in the tunnel on either side of the ATLAS and CMS interaction points. The magnets, cold masses, and cryo-assemblies are produced in collaboration with institutes worldwide.
With the exception of Q1 and Q3, for which part of the testing is carried out in the United States, all cryo-assemblies undergo horizontal testing at CERN in the SM18 test facility, with 5 horizontal test benches each dedicated to a cryo-assembly type. Qualification tests include assessing quench and powering characteristics, taking magnetic field and geometry measurements, instrumentation tests, verification of electrical circuits, and cryogenic performance tests.
16 of the 28 new horizontal cryo-assemblies required for installation have been successfully tested and qualified for tunnel deployment. The results are consistently strong, marking the achievement of the halfway milestone in the qualification phase and confirming that the project has progressed beyond the midpoint.
The dedication of the test team, with the strong support of many groups, to update the benches to a highly efficient and reliable facility for HiLumi LHC cryo-assemblies has paid off, with testing through 2024 and 2025 of cryo-assemblies on arrival.
Figure 2. A corrector package (CP) cryoassembly on the horizontal test bench during tests at 1.9 K. It holds 1 orbit corrector from CIEMAT, Spain, and 9 higher-order corrector magnets from INFN, Italy. To be able to perform magnetic measurements using stretched wires or rotating coil measurement shafts, each magnet is equipped temporarily with an anti-cryostat (visible on the right), passing through the full length of the cold mass, to make the bore of the magnet accessible at room temperature. In front of the magnet, the stretched wire system is installed. Florence Thompson / CERN
Figure 3. Dashboard of testing in SM18, showing 16 cryo-magnet assemblies fully qualified (in green on the left). Gerard Willering / CERN
Completion of vertical testing of individual magnets destined for the tunnel
Before assembly into cold masses, 76 of the 88 magnets are tested vertically. The longest units – MBRD (>7.5 m) and MQXFB (>7 m) – cannot be accommodated in any vertical test station, so their full qualification is carried out only after integration into the D2 and Q2 cold masses together with their correctors.
With the successful testing at the end of April of the fourth MCBXFA magnet (a 2.5 m-long orbit corrector produced by the project’s Spanish partner, CIEMAT), vertical testing of all magnets destined for tunnel installation is now complete, and all have met the acceptance criteria.
Only 6 out of the 25 spare magnets remain to be tested, reflecting strong progress and high confidence in meeting the project’s goal of timely installation of all cryomagnets during Long Shutdown 3.
Figure 4. Orbit corrector magnet following vertical testing at CERN’s magnet testing facility. Florence Thompson / CERN
What’s next?
Throughout 2026 and 2027 the testing of series and spare units for the Hilumi LHC, including individual magnets, cold diodes, cryo-assemblies and superconducting links, will continue at a high pace and as high priority. Afterwards, the test station will continue to support special and additional tests for HiLumi LHC during hardware commissioning and operation. In parallel, the SM18 magnet test facility, unique in its capacity and versatility, and with a highly experienced team, is ready and still evolving to impact the High Field Magnet program with measurements, instrumentation, diagnostics and analysis.
Figure 5. TE-MSC-MQA magnet test team members in front of a D1 cryo-assembly on the test bench. Florence Thompson / CERN
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