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Particle tracker system delivered to CERN
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20/10/2006
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The CCLRC Rutherford Appleton Laboratory (RAL) has delivered a system to CERN that will help to process the vast amounts of data generated by the silicon tracking detector within the Compact Muon Solenoid experiment.
Some 40million particle collisions will occur every second inside CMS. A trigger system selects 100,000 of those collisions each second as interesting events and these are fed through to the front end driver (FED) electronics boards using optical fibres. Around 40,000 optical fibres in bundles that are 70m long carry data from the CMS detector to racks of FED boards in another cavern which is 100m underground.
Each particle collision, or event, produces about 10Mbyte of silicon detector data and one board will handle 3Tbyte of data each second. The whole system processes the equivalent of the contents of 2000 CDs every second and must operate around the clock for several months at a time each year.
The FED boards keep only the useful information in each event, extracting data from just the silicon strips in the tracking detector that have registered particle hits. This reduces the amount of information recorded by more than 90%. Each FED board corresponds to a specific part of the CMS tracker, so when the output from each FED board is passed through a switch system, the data can be assembled to create a picture of the whole particle collision inside CMS.
The FED system – which comprises 500 boards in 12 racks – cost £2m, with funding provided by the Particle Physics and Astronomy Research Council. Boards were manufactured by Exception EMS. The system also contains 15,000 fpgas.
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Author
Graham Pitcher
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