SPS Personnel Protection System: From Design to Commissioning

During the second long shutdown (LS2) of the accelerator complex at CERN, the access system of the Super Proton Synchrotron (SPS) was completely renovated. This complex project was motivated by the technical obsolescence and lack of sufficient redundancy in the existing system, as well as by the need for homogenisation of technologies and practices across the different machines at CERN. The new Personnel Protection System includes 16 state-of-the-art access points making sure that only fully identified, trained and authorised personnel can enter the facility and an interlock system with a rationalized number of safety chains designed to meet the current safety standards. The control part is based on Siemens 1500 series of programmable logic controllers, complemented by a technologically diverse relay logic loop for the critical safety functions. This paper presents the new system and the design choices made to permit fast installation in a period where the access system itself was heavily used to allow vast upgrades of the SPS accelerator and its infrastructure. It also covers the verification and validation methodology and lessons learned during the commissioning phase.