The LHC is being warmed up from near absolute zero to room temperature

For only the third time since it began operating in 2008, the Large Hadron Collider (LHC) is slowly being returned to room temperature after being kept at close to -271°C, just above absolute zero. With the LHC at room temperature, technicians and engineers will be able to work on the accelerator as it is transformed into the HiLumi LHC during Long Shutdown 3 (LS3).

Warming up more than 36 000 tonnes of cryogenic equipment across 27 kilometres of tunnel requires meticulous planning at every step. The cryogenics team has been running the warm-up sequence since LS3 began on 29 June 2026.

Once the electrical lockout of the LHC had been successfully completed, the first step was to remove the liquid helium stored inside the magnets and the cryogenic line. The technicians used heaters to evaporate the helium, which was then sent to the surface to be liquefied and stored ready to be used again once the accelerator resumes operation in mid-2030.

With the helium removed, large heaters are now gradually raising the temperature of the magnets while a control system keeps the process safe. The entire system should be warmed to room temperature by 11 September, at which point the magnets that need to be replaced for HiLumi LHC can start to be dismantled.