It finally happened! The particle-smasher known as the Large Hadron Collider is back online after more than two years, during which its various components were upgraded to make it even meaner. A team of scientists and engineers gathered at the collider’s control room at CERN over the weekend – giving up Easter celebrations at home – to revive the giant machine so it could resume feeding its four detectors with high-energy collisions of protons.
Before the particles enter the LHC itself, they are pre-accelerated to 450 GeV by the Super Proton Synchrotron. At 11.53 am (CET), the first beam of pre-accelerated protons was injected into the LHC at Point 2 (see image), starting a clockwise journey. By 11.59 am, it’d been reported crossing Point 3, and at 12.01 pm, it was past Point 5. The anxiety in the control room was palpable when an update was posted in the live-blog: “The LHC operators watching the screen now in anticipation for Beam 1 through sector 5-6”.
Finally, at 12.12 pm, the beam had crossed Point 6. By 12.27, it had gone a full-circle around the LHC’s particles pipeline, signalling that the pathways were defect-free and ready for use. Already, as and when the beam snaked through a detector without glitches, some protons were smashed into static targets producing a so-called splash of particles like sparks, and groups of scientists erupted in cheers.
— ATLAS Experiment (@ATLASexperiment) April 5, 2015
— Dr Clara Nellist (@claranellist) April 5, 2015
Both Rolf-Dieter Heuer, the CERN Director-General, and Frederick Bordry, Director for Accelerators and Technology, were present in the control room. Earlier in the day, Heuer had announced that another beam of protons – going anti-clockwise – had passed through the LHC pipe without any problems, providing the preliminary announcement that all was well with the experiment. In fact, CERN’s scientists were originally supposed to have run these beam-checks a week ago, when an electrical glitch spotted at the last minute thwarted them.
In its new avatar, the LHC sports almost double the energy it ran at, before it shut down for upgrades in early-2013, as well as more sensitive collision detectors and fresh safety systems. For the details of the upgrades, read this. For an ‘abridged’ version of the upgrades together with what new physics experiments the new LHC will focus on, read this. Finally, here’s to another great year for high-energy physics!