The Sciences

Beam is Back! The LHC Restarts

Cosmic VarianceBy John ConwayOct 27, 2009 3:18 PM

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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!

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