The CERN Detector Safety System for LHC Experiments

The Detector Safety System (DSS), developed at CERN in common for the four LHC experiments under the auspices of the Joint Controls Project (JCOP), will be responsible for assuring the equipment protection for these experiments. Therefore, the DSS requires a high degree of both availability and reliability. It is composed of a Front-end and a Back-end part. The Front-end is based on a redundant Siemens PLC, to which the safety-critical part of the DSS task is delegated. The PLC Front-end is capable of running autonomously and of automati-cally taking predefined protective actions whenever re-quired. It is supervised and configured by the CERN-cho-sen PVSS SCADA system via a Siemens OPC server. The supervisory layer provides the operator with a status display and with limited online reconfiguration capabili-ties. Configuration of the code running in the PLCs is completely data driven via the contents of a ?Configura-tion Database?. Thus, the DSS can easily adapt to the different and constantly evolving requirements of the LHC experiments during their construction, commis-sioning and exploitation phases. Currently, the DSS is being installed and commissioned for the construction of the CMS and LHCb.