Beam Interlocks for LHC and SPS

The Large Hadron Collider at CERN (LHC) will operate at 7 TeV/c with a luminosity of 10 cms. This requires two beams with about 3^10 protons/beam, corresponding to a stored energy of about 350 MJ, sufficient to heat and melt 500 kg of copper. Protection of equipment from damage in case of uncontrolled beam losses is challenging. Injection of the beam from the SPS to the LHC could already damage equipment and is only permitted when all LHC systems are correctly prepared. In case of an uncontrolled loss of the circulating LHC beams, it is required to extract the beams into a specially designed target as soon as possible. Beam loss monitors and equipment for hardware surveillance are distributed around the 26 km long accelerator. In case of failures or beam losses, the beam interlock system is informed and sends a dump request to the beam dumping system. The beam interlock system also inhibits injection when the LHC is not ready for beam. In this paper the requirements for the beam interlock system are discussed, with particular emphasis on its reliability. The architecture with 16 VME based controllers distributed around the LHC and linked by optical fibres is described. Identical hardware will be used to modernise the interlock system for the SPS (CERN Super Proton Synchrotron). This will provide validation of the controllers in a working accelerator before the LHC startup. Results from a first prototype controller tested in the SPS are presented