THE LHC ACCESS SYSTEM

This paper describes the LHC Access System, built to protect the personnel working in the LHC from radiation hazards; the system's architecture and the experience gathered of commissioning, testing and using it. The system is made of two parts: the LHC Access Control System (LACS) and the LHC Access Safety System (LASS). Using redundant, fail-safe PLCs and a supplementary cabled loop the LASS guarantees the safety of the personnel in all events. Using industrial components, the LACS regulates the access to the tunnels and experimental areas by identifying users and checking their authorizations. It allows a remote or automatic operation of the access control equipment and restricts the number of users working simultaneously in the interlocked areas. Since the beginning of the operational phase, additional efforts and studies have been done to ensure the inviolability of this protection system by users not holding the required credentials. The design, procurement and installation of the entire system took more than 4 years and the commissioning phase lasted about 12 months. The paper presents as well the return of experience of the first 2 years of operations.