"At peak consumption, usually from May to mid-December, CERN uses about 200 megawatts of power, which is about a third of the amount of energy used to feed the nearby city of Geneva in Switzerland."
Well, not quite. They don't shutdown in the first place because of the power usage, but they choose the timing for the shutdown when it is most economical. Regular maintenance is unavoidable.
Regular maintenance work (maybe just sweeping dust off everything or fixing minor leaks etc.) might require complete shutdowns, as the magnetic fields and temperatures around the accelerator might be dangerous. Further, scientists often move to their job for just a few months/years and hence have most of their family far away. Christmas/New Year is a traditional time to go home and spend some time with them, especially since most other institutions (schools, unis etc.) also shut down around then. Combining the two might lead to a somewhat extended “winter recess”.
> Regular maintenance work (maybe just sweeping dust off everything or fixing minor leaks etc.) might require complete shutdowns, as the magnetic fields and temperatures around the accelerator might be dangerous.
Also makes sense to have your annual shutdown when electricity prices are likely to be high: I'd guess that heating has a higher impact on these than air conditioning in Switzerland.
Current generation particle accelerators aren't commodity machines. They're custom hot rods, operating at the limits of stability in a high radiation environment. I never understood why people are surprised that they have to be rebooted from time to time. (And the reboot process is a doozy. It takes about a month to get everything properly tuned.)
The shutdown is in winter because CERN's budget is limited, and electricity is cheaper in the summer.
Can anyone shine a light on why the particle accellerator needs recess?