Renovation of the SPS Personnel Protection System: A Configurable Approach

The renovation of the SPS Personnel Protection System (PPS) comprises the installation of industrial access control solutions and the implementation of a new safety instrumented system tailored to the particular needs of the accelerator. The SPS has been a working horse of the CERN accelerator complex for many decades and its configuration has changed through the many years of operation. The classic solutions for safety systems design, used in the LHC and PS machines, have not been judged adequate for this accelerator undergoing perpetual changes, composed of many sites forming several safety chains. In order to avoid expensive software modifications, each time the accelerator configuration evolves, a configurable safety software design was proposed. This paper presents the hardware architecture of the PLC-based SPS PPS and the configurable software architecture proposed. It further reports on the testing and formal verification activities performed to validate the safety software and discusses the pros and cons of the configurable approach.