LHC: First Magnet Failure

Well, no one said this would be easy...and it isn't. The LHC has had 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 I have not seen an 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 (I am being deliberately vague here) and in the mean time, no tests with beam are possible. This is a setback, for sure! People were getting quite excited about the possibility that the LHC could collide protons at high energy, 10 TeV in the center of mass, by late October or November, before shutting down for the winter in December. Could this still happen? My guess is that it is unlikely given this failure, but we'll know for sure soon. Stay tuned...