Liverpool helps study of ‘mini big bang’


Scientist working on the EndCap-C

The Large Hadron Collider (LHC) at CERN hit the headlines again this week.

Scientists in Switzerland have successfully recreated the ‘mini Big Bang’ generating temperatures of 10 trillion degrees – a million times hotter than the centre of the sun.

The High Energy Physics Group at the University of Liverpool is part of the ATLAS Collaboration at the LHC, and the ATLAS Experiment EndCap-C was assembled in the Liverpool Semiconductor Detector Centre.

The first collisions were recorded at 00:30 Central European Time on Sunday 7 November, and stable running conditions marked the start of physics with heavy ions.

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.

The three experiments recording data with lead ions, ALICE, ATLAS and CMS can now look forward to continuous lead-ion running until CERN’s winter technical stop begins in December. Following the winter technical stop, operation of the collider will start again with protons in February and physics runs will continue through 2011.

For the latest news on lead ion collisions at the LHC, visit the CERN website

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