Particle accelerator Large Hadron Collider (LHC) has turned off its particle beams ahead of a shut-down period that will last two years.
The LHC is best known for its role in spotting the Higgs boson in late 2012.
But following technical faults shortly after it first switched on, the machine has never been run at the full energies for which it was designed.
A programme of repairs and upgrades should allow that in late 2014.
The LHC’s beams were “dumped” early on Thursday morning, but it will take until Saturday morning for the machine’s 1,734 magnets to warm up to room temperature.
Then an unprecedented period of upgrade and repair – dubbed “Long Shutdown 1” – will begin.
The machine ran at particle energies of 8 trillion electron-volts (TeV) in 2012, up from the prior high point of 7TeV in 2011. But when the shutdown concludes, slated for the end of November 2014, it should be set to run at 13TeV – far and away the highest-energy collisions ever attempted by scientists.
The major work required is to upgrade the connections between the magnets, such that they can handle the enormous electrical currents that may pass through them at higher particle energies and in the event of faults such as the one in 2008.
But the shutdown maintenance schedule also includes upgrades to all four of the LHC’s detectors, the shielding of electronics – even the ventilation system of the 27 km-long tunnel that houses the main accelerator ring.
The shutdown is due to conclude in late November 2014, after which the system will be put through its paces and experiments are expected to resume in February or March 2015.