CERN goes into its first long shutdown, after last year’s great success, and it’s time open up the CMS particle detector and get inside for maintenance and repairs. Engineers and technicians started opening the CMS detector on 7 March, but moving the parts of this 14,000-tonne behemoth is no easy feat. The open side of the CMS detector, looking upwards from the cavern floor. Image © Michael Hoch/CMS
CMS has a barrel section made of five rings, with two end caps each comprising three discs and, outside those discs, two 250-tonne forward hadron calorimeters (HF). To open CMS, the HFs, which surround the beam pipe, are opened and lowered to the cavern floor, where they are floated on air pads into storage alcoves. Then the end cap discs are moved away from the barrel, starting with one end and then going to the other.
“It took a couple of weeks of work to move the forward calorimeters and the first three discs apart,” says detector physicist David Barney of CMS. “Then we went to the other end and started to move the other three discs.”
“When the preshower is there, you should hopefully be able to tell the difference between a single photon and a pair of closely spaced photons,” says Barney. “But there’s this relatively big area of the preshower that doesn’t work because of a flaky connector that has been there for two years! We can only fix it when we open the detector,” he sighs.
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