Accelerator Report: LHC protons outpacing the Easter tradition

The LHC has restarted and both beams have been circulating in the machine since 8 April, meaning that the start of the LHC beam commissioning during Easter is apparently not a constant of nature.

By Rende Steerenberg

LHC page 1 on 8 April at 12.03 p.m. Beam 1 (blue line) was the first to circulate, at 10.40 a.m. At 11.43 a.m., beam 2 (red line) was also circulating. Just after noon, both beams were injected and circulated together in the LHC for the first time in 2025. The real beam commissioning work had started.(Image: CERN)

I concluded my previous Accelerator Report with: “…if the two-week delay holds, the 2025 commissioning may once again fall during the Easter weekend. Have we discovered a new constant of nature?”, referring to the delay caused by a leak in the water-cooling system of the ATLAS argon calorimeter.

But, as is often the case at CERN when challenges arise, everyone stepped up. ATLAS mobilised its resources and the other experiments offered their support to resolve the issue as quickly as possible. Thanks to this efficient coordination and dedicated work, the expected two-week delay was reduced to just four days.

So, the start of the LHC beam commissioning during Easter is not a new constant of nature after all.

In the early hours of 8 April, the final preparations were under way: the ATLAS access shaft was being closed, the final checks were being carried out on the LHC machine and experts were gathering in the CERN Control Centre (CCC) to contribute to beam commissioning and to witness protons circulating in the LHC for the first time in 2025…

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