The news on the CERN website posted 18 February 2013:
On Saturday at 8.25am the shift crew in the CERN Control Centre extracted the beams from the Large Hadron Collider (LHC) for the last time before the machine's first Long Shutdown. The following message marked the event on LHC Page 1: "No beam for a while. Access required: Time estimate ~2 years."
January's proton-lead run was followed last week by four days of proton-proton collisions at 1.38 TeV. Final proton collisions in the LHC took place on Thursday at 7.24am, but beams were kept in the machine for 48 hours for "quench tests" on the magnets.
A quench is when a superconducting magnet fails to maintain a superconducting state, and therefore stops operating correctly. This can happen if a tiny amount of the beam is off orbit and deposits energy in the magnets. The tests aimed to establish what beam loss is actually required to quench the magnets.
The LHC now enters its two-year shutdown, which will see a hive of maintenance activity on all of CERN's accelerators. Work on the LHC will include the consolidation of more than 10,000 interconnections between magnets. The entire ventilation system for the 628-metre circumference Proton Synchrotron will be replaced, as will over 100 kilometres of cables on the Super Proton Synchrotron.
It's going to be a busy shutdown.