CERN completes transition to lead-ion running at the LHC

Four days is all it took for the LHC operations team at CERN to complete the transition from protons to lead ions in the LHC. After extracting the final proton beam of 2010 on November 4, commissioning the lead-ion beam was underway by early afternoon.

First collisions were recorded at 12:30 am. CET on November 7, and stable running conditions marked the start of physics with heavy ions at 11:20 a.m. CET today.

''The speed of the transition to lead ions is a sign of the maturity of the LHC,'' said CERN director general Rolf Heuer. ''The machine is running like clockwork after just a few months of routine operation.''

Operating the LHC with lead ions - lead atoms stripped of electrons - is completely different from operating the machine with protons.

From the source to collisions, operational parameters have to be re-established for the new type of beam. For lead ions, as for protons before them, the procedure started with threading a single beam round the ring in one direction and steadily increasing the number of laps before repeating the process for the other beam.

Once circulating beams had been established they could be accelerated to the full energy of 287 TeV per beam. This energy is much higher than for proton beams because lead ions contain 82 protons. Another period of careful adjustment was needed before lining the beams up for collision, and then finally declaring that nominal data taking conditions, known at CERN as stable beams, had been established.