At the beginning of December, CERN received an important shipment. It contained a cryo-assembly of two 4.2-m-long magnets developed by the Accelerator Upgrade Project in the US. These magnets are vital for the high-luminosity upgrade of the LHC (HL-LHC). With coils made from niobium–tin, instead of the niobium–titanium that the LHC currently uses, they will help focus the particle beams to an even smaller spot size at the interaction points of the ATLAS and CMS experiments.

This is the first of ten cryo-assemblies that will make the month-long journey from the US. A celebration was held at CERN on Monday, 18 December to commemorate this milestone, bringing people from both sides of the Atlantic together. “In the realm of large scientific endeavours like the HL-LHC, global collaboration and expertise play pivotal roles. The delivery of the first cryo-assembly housing fully validated niobium–tin series magnets is a tangible testament to the success of the US Accelerator Upgrade Project,” says Mike Lamont, CERN Director for Accelerators and Technology. “This event not only marks a crucial milestone in our collaboration with our US partners, but also celebrates the outstanding contributions shaping the future landscape of particle physics at CERN.”

These cryo-assemblies from the US will be used in conjunction with the 7.2-m-long magnets of the same design developed at CERN for the HL-LHC. Both types of magnet are to be installed in the inner-triplet (IT) string, a facility at CERN built to test all the components that will comprise the interaction regions at ATLAS and CMS.

“With this arrival, five out of the six cryomagnets for the IT string are now at CERN ready for testing,” says Ezio Todesco, who is in charge of the HL-LHC interaction region magnets. “The string will take on good colours in 2024.”

“This first cold-mass assembly will go into the IT string and will be extensively tested throughout 2025,” says Oliver Brüning, HL-LHC project leader. “This marks the start of a new phase of the CERN-US collaboration: the delivery of final cryo-assemblies ready for installation in the LHC.”

Giorgio Apollinari, Project Director of the HL-LHC AUP, is looking forward to this next phase of the project. “We have been building these magnets in the US for the last five years and have now completed 75% of their production,” he said. “We’ve sent the first two magnets in a final cryo-assembly after extensive tests in the US and are already putting together the next cryo-assembly, scheduled to arrive at CERN by early 2024.”

Watch a timelapse of the magnet unboxing at CERN below.