The LHC's Final Shutdown: CERN Begins a Four-Year, $1.5 Billion Transformation

LS3 Timeline and Scope

LS3 is expected to last up to four years, involving thousands of experts across CERN's sites and tunnels . The LHC's last beams were scheduled to be dumped on June 29, 2026, according to CERN's internal schedule . The injectors will continue producing beams through August 2026 before their own shutdown begins .

The LS3 programme includes major maintenance, consolidation, and the installation of the HL-LHC's core components: new 12-tesla niobium-tin quadrupole magnets (inner triplets) that will focus beams more tightly than the current 8-tesla niobium-titanium magnets, and superconducting radio-frequency crab cavities that will tilt proton bunches before collision to maximize head-on overlap and correct geometric luminosity loss . About 1.2 km of the LHC tunnel will be replaced with new technologies .

The restart of data-taking is scheduled for 2030 at the earliest, after hardware and beam commissioning . The accelerator complex is expected to gradually resume operation from mid-2028 onwards, but full physics collisions will take longer to achieve .

The $1.5 Billion Upgrade: Cost and Technical Details

The HL-LHC project is a multi-billion-Swiss-franc investment. The figure of roughly $1.5 billion (approximately 1.5–1.6 billion Swiss francs) is consistent with the project's approved budget envelope, though exact reported numbers vary by currency and year . CERN press materials describe it as a major multi-year investment covering new magnets, cryogenics, collimators, shielding, and upgraded detectors including ATLAS, CMS, ALICE, and LHCb .

The core goal is a tenfold increase in integrated luminosity, from the LHC's original design of about 300 fb⁻¹ to up to 3000 fb⁻¹ for the HL-LHC . Peak luminosity is expected to reach 5×10³⁴ cm⁻² s⁻¹, with potential to push higher . This tenfold boost means roughly 15 million Higgs bosons produced per year, enabling precision studies of Higgs couplings and self-interactions that are impossible today.

Scientific Achievements of the LHC Era (2010–2026)

• Higgs boson discovery (2012): ATLAS and CMS announced the discovery of a new boson with a mass of about 125 GeV, consistent with the Standard Model Higgs boson, completing a five-decade search . The discovery was awarded the 2013 Nobel Prize in Physics .
• Run 1 (2010–2012): First collisions at 3.5 TeV per beam, a world record, culminating in the Higgs discovery .
• Run 2 (2015–2018): Collisions at 6.5 TeV per beam; precision measurements of the Higgs boson, confirmation of Yukawa couplings to third-generation fermions, and observation of rare processes .
• Run 3 (2022–2026): Continued proton-proton and heavy-ion collisions at 13.6 TeV centre-of-mass energy, doubling the total collected dataset .

The LHC's operational era is often described as an "18-year run," though this is a round approximation of the calendar span from first collisions (2010) to the end of Run 3 (2026). The actual collision time was closer to 13 years, interrupted by Long Shutdown 1 (2013–2015), Long Shutdown 2 (2019–2021), and annual year-end technical stops .

What the HL-LHC Will Enable

Once operational, the HL-LHC will allow physicists to:

• Study the Higgs boson with unprecedented precision, measuring its couplings to other particles and searching for signs of self-interaction, which could reveal deviations from the Standard Model.
• Search for dark matter with higher sensitivity to weakly interacting massive particles and other beyond-Standard-Model signatures.
• Extend discovery reach for new heavy particles by roughly 30%, because the vastly larger dataset allows scientists to detect or exclude particles at higher masses than the current LHC could .

The HL-LHC is projected to continue operations until approximately 2041, after which CERN will decide on its successor—possibly the Future Circular Collider (FCC) . The machine will retire having served as the flagship instrument for particle physics for over three decades.

The LHC's final shutdown is not an ending but a metamorphosis. When the collider reawakens around 2030, it will be a fundamentally different machine, designed to answer the deepest questions left open by the Higgs discovery: what lies beyond the Standard Model, what dark matter is made of, and whether the universe's fundamental forces unify at higher energies.