The LHC is scheduled to restart in June 2030, when CERN plans to send the first beams through the upgraded High Luminosity LHC. The machine has been offline since 27 June 2026, when Run 3 ended and Long Shutdown 3 began. CERN has published the month but not yet an exact day.
The Current Schedule
CERN's accelerator schedule puts first High Luminosity LHC beams in June 2030. That date marks the start of beam commissioning, the careful process of threading particles through a machine that has been partly rebuilt. Collisions for physics follow once commissioning proves the new hardware behaves, typically within weeks to a few months of first beam.
Between now and then, the tunnel under the French and Swiss border is a construction site. The countdown on our LHC timer tracks the June 2030 target to the middle of the month, and we update the target the day CERN announces a change.
Why the Restart Date Moved
If you followed the project years ago, you may remember earlier restart estimates. The High Luminosity upgrade was originally pencilled in to begin operation in the mid 2020s. The dates shifted for reasons that are boring in the best way: schedule reviews, component production timelines, and the decision to extend Run 3 to squeeze more physics out of the old configuration before shutting down.
The current plan settled after CERN's 2024 and 2025 schedule updates. Run 3 was extended through June 2026, Long Shutdown 3 was compressed where possible, and first HL-LHC beams landed on June 2030. Four years is actually fast for what is being done. The two previous long shutdowns each took over two years for far smaller changes.
What Has to Happen Before First Beams
The restart is not a switch being flipped. The work list for Long Shutdown 3 is the largest since the LHC was built:
- 1.2 kilometres of the ring replaced. The sections either side of the ATLAS and CMS collision points are being dismantled and rebuilt with new focusing magnets.
- New superconducting magnets. The inner triplet quadrupoles that squeeze the beams before collision are being replaced with niobium tin magnets that reach fields around 12 tesla, beyond what the old niobium titanium technology could sustain.
- Crab cavities installed. These superconducting radio frequency cavities tilt each proton bunch just before it crosses the opposing beam, so the bunches overlap more completely. It is the first use of crab cavities on a hadron collider anywhere.
- 36,000 tonnes of cryogenics warmed and recooled. The whole 27 kilometre magnet chain has to come up to room temperature for the work, then be taken back down to 1.9 kelvin.
- Detector rebuilds. ATLAS and CMS are replacing entire tracking systems so they can survive and read out the much busier collisions the upgrade will produce.
The injector chain, the smaller accelerators that feed the LHC, restarts first. CERN plans to bring the injectors back from mid 2028, giving two years of running to prepare beams before the main ring wakes up.
How the Restart Will Unfold
Based on how the 2010, 2015 and 2022 restarts went, expect a sequence rather than a moment. First comes hardware commissioning, months of powering tests with no beam at all. Then pilot beams, a handful of low intensity bunches used to check that thousands of magnets bend and focus correctly. Then the energy ramp, and finally "stable beams", the announcement that collisions for physics have begun. Our timer counts to first beams; the first physics collisions of Run 4 follow that milestone.
Could the Date Slip Again?
It could. Accelerator schedules are estimates built from thousands of dependent tasks, and CERN has moved dates before, in both directions. The honest way to track it is to watch the official schedule rather than headlines, which is what this site does. When CERN names an exact day for first beams, the countdown will switch from our mid June placeholder to the announced date. The target month has been stable since the schedule was fixed, and the work underground is proceeding on plan as of the latest CERN accelerator reports.
How This Compares to Past Restarts
The LHC has come back from darkness three times, and the pattern is encouraging. The 2009 restart followed fourteen months of repairs after the interconnect incident, and within weeks the machine held the world collision energy record. The 2015 restart followed the two year Long Shutdown 1 and nearly doubled the energy to 13 TeV. The 2022 restart followed three years of injector upgrades and delivered 13.6 TeV plus the brightest beams the machine had ever produced. Each pause has been longer than the last because each rebuild has been more ambitious, and each restart has worked. The 2030 edition is the biggest bet yet, but it is being made by the same teams with three successful revivals behind them.
One practical difference this time: the injectors get a two year head start. By the time the main ring is cold again, the smaller machines feeding it will have been running smoothly since 2028, which removes a whole class of restart surprises.
What to Do While You Wait
Physics has not stopped. The experiments are still analysing the record dataset Run 3 delivered, and results will keep publishing straight through the shutdown. If you want to understand what the machine is being turned into, start with what the HL-LHC actually is, or walk the full LHC timeline from 2008 to 2041.