The LHC (Large Hadron Collider) has had today its first major incident, the failure of one of the 1230 main superconducting dipole magnets. This was apparently due to a “quench” in which the magnet goes rapidly from the superconducting to the normal conducting state, which then means that the tremendous electric current in the magnet suddenly starts heating it up, causing huge internal mechanical stresses. As pointed out elsewhere, quenches are expected to happen quite often in the LHC. The magnets are designed to withstand these forces, in principle, and were tested extensively. What happened here is not clear yet, and there is no official statement from CERN. Probably best to wait for that.As for the effect on the LHC commissioning, to repair or replace the magnet requires warming up the relevant sector, then cooling back down after the repair. This takes several weeks, perhaps two months, and in the mean time, no tests with beam are possible.
