Beam is Back! The LHC Restarts

By John Conway | October 27, 2009 1:18 pm

This past weekend saw the first beam particles in the LHC since the magnet quench incident of September 2008. Protons and lead ions were threaded in two directions around part of the ring before being dumped, and everything worked without a hitch. The graphs show the ion beam spot entering Collision Point 2 before being dumped.


The LHC machine commissioning will pick up where it left off more than a year ago, and the plan is, if all goes well, to collide beams of protons in the experiments at a center of mass energy of 7 TeV (3.5 TeV per beam) before the end of the year. The luminosity will not be large at first, but should increase steadily with time until next fall, when the long shutdown to retrofit the remaining magnets with new quench detection and helium pressure relief systems begins. By that point the experiments hope to have accumulated upwards of 200 pb-1 of integrated luminosity. This initial data sample is sorely needed to shake down the detectors and start tuning up the event reconstruction and analysis. And who knows, maybe we’ll see something totally unexpected. (Please, no black hole comments!)

The next main milestone will be beam circulating around the whole ring and captured by the RF system. That should happen by mid-November. Fingers crossed!

CATEGORIZED UNDER: Science, Technology
  • tacitus

    Cool. All fingers and toes crossed this time.

  • Peter Woit

    The latest schedule I’ve seen has collisions only a 1.1 TeV/beam by the end of the year. Evidently the decision was made to start the beam commissioning next month even though the magnets will only have been commissioned to 2kA, not the 6kA needed for 3.5 TeV/beam. The higher energy will have to wait forJanuary.
    I don’t think CERN has publicly announced this, but the news somehow did make it to the NYT blog…

  • Marc

    I’ve heard that the beams will be at 1.1 TeV for many, many months. Hope this isn’t the case….

  • Iain

    Don’t cross the beams!

    But seriously, I’m very happy to hear the news. Really, really looking forward to the results!

  • Sili



    I promise to stay away from Geneva. I have in the past had bad experiences with synchrotons. They really don’t like my presence. (Nor apparently do reactors, but at least ‘we’ still managed to get data out of the ILL.)

  • Peter Coles

    Is that why we had to put the clocks back?

  • John

    Yes, I have heard the 1.1 TeV rumors too, but they seem confident that they can achieve 3.5 TeV per beam, hopefully this year. We shall see!


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