Beam Loss Mechanisms, Measurements and Simulations at the LHC (Quench Tests)

Monitoring and minimization of beam losses is increasingly important for high-intensity and superconducting machines. In the case of the LHC, the collimation system is designed to absorb the energy of lost particles and confine the main multi-turn losses to regions without sensitive equipment. However many loss mechanisms produce local loss events which can be located elsewhere in the machine. A beam loss monitoring system, covering the whole machine circumference is therefore essential, and is used for both machine protection and diagnostics. In order to fully understand the measured signals and set-up the beam abort thresholds, extensive simulation work is required, covering particle tracking in the accelerator and the generation of the particle showers created by the lost particles. In order to benchmark these simulations and verify beam-abort thresholds, special tests have been performed where beam losses are provoked in a controlled manner over a wide range of durations. This work summarizes the experience in understanding beam losses in the LHC during Run 1.