CERN switches off the Large Hadron Collider for modernization

Four years of conversion until 2030

At 05:52 and 15 seconds, CERN had already published a kind of farewell message on its website: "Mach's gut, LHC, und danke für all die Kollisionen". Shortly afterwards came the outlook: "Begeben wir uns auf den Weg zum Hilumi-LHC". This clearly sets out the next milestone: the High-Luminosity LHC, or HiLumi-LHC for short.

Key parts of the LHC will be renewed over the next four years. The new HiLumi-LHC accelerator is to be powered up in June 2030. The upgrade focuses on the area of the two major central experiments ATLAS and CMS, as well as on a roughly two-kilometre-long section of the 27-kilometre tunnel. The goal is to track down further secrets of the universe with even more proton collisions.

Helium pumping-out takes at least one month

Extensive technical work lies ahead during this period. First, all the helium has to be pumped out of the magnets – which, according to project leader Markus Zerlauth, will take at least one month on its own. Since CERN does not have sufficient storage capacity of its own, the helium has to be handed over to external companies. Only then can the components be replaced and the new, more powerful magnets and improved detectors be installed.

With the modernization, CERN aims to push the accelerator to the limits of its performance. Project leader Markus Zerlauth explained that collisions will increase by a factor of ten. The researcher Nedaa-Alexandra Asbah, who works on the ATLAS experiment, said: "Wir werden sechsmal mehr Daten haben und eine höhere Wahrscheinlichkeit, seltene Ereignisse zu beobachten". This opens up entirely new possibilities for detecting rare physical phenomena that could hardly be captured with the previous facility.

Mystery of dark matter in focus

At the centre of interest is what is known as dark matter. Together with dark energy, it makes up about 95 percent of the universe. Dark matter alone accounts for around 85 percent of the matter in the universe. However, the particles behind dark matter have never yet been detected. With the CMS experiment, the researchers hope to learn more about the nature of dark matter from 2030 onwards, using more powerful magnets and better detectors.

End of an era in sight

Physicist Filip Moortgat of CERN also sees far-reaching possibilities. He said the discovery of new dimensions of space is also conceivable. The LHC has, in fact, already made history: in 2012, the Higgs boson was discovered at CERN – a particle of central importance to the Standard Model of particle physics.

After the upgrade, the LHC is to remain in operation until around 2040 and then be definitively shut down. So while the current pause does not mean an immediate end, the end of the era of the existing LHC is in sight. The conversion phase now beginning is one of the most profound modernizations in CERN's history.

With the symbolic "No beam" bar and the online farewell, CERN publicly marked the loss of the proton beam in the 27-kilometre ring-shaped accelerator. The process went as planned – and the phase in which the LHC is to become the High-Luminosity LHC step by step has now begun. Exactly when the first collisions of the new machine will take place is now tied to the date in June 2030.