Beam Induced Quenches of LHC Magnets

In the years 2009-2013 LHC has been operated with the top beam energies of 3.5 TeV and 4 TeV instead of the nominal 7 TeV, with corresponding reduced currents in the superconducting magnets. To date only a small number of beam-induced quenches have occurred, with most of them being specially designed quench tests. During normal collider operation with stored beam there has not been a single beam induced quench. This excellent result is mainly explained by the fact that the cleaning of the beam halo worked very well and, in case of beam losses, the beam was dumped before any significant amount of energy was deposited in the magnets. However, conditions are expected to become much tougher after the long LHC shutdown, when the magnets will be working at near nominal currents in the presence of high energy and intensity beams. This paper summarizes the experience to date with beam-induced quenches. It describes the techniques used to generate controlled quench conditions which were used to study the limitations. Results are discussed along with their implication for LHC operation after the first Long Shutdown.