Experience with the String2 Cryogenic Instrumentation and Control System

Publisher Summary This chapter reports on the experience of four years of designing, installation, commissioning and maintenance, and outlines the lessons learned for the Large Hadron Collider (LHC). String2 was a 120 m full-scale model of a regular cell of the LHC accelerator arc. It was composed of eight superconducting main magnets, fed by a separate cryogenic distribution line (QRL); an electrical feed box (DFB) which supported the superconducting current leads that powered the magnets. Bearing an intensive experimental programme, String2 was heavily instrumented. The complexity of the cryogenic instrumentation and control system was close to a full 3.3 km LHC sector. The String2 facility provided validation and additional knowledge for instruments, front-end electronics, electromagnetic compatibility, fieldbus and PLC architectures, remote electronics positionners, control algorithms, programming methodology, and SCADA. In some cases weaknesses were highlighted, triggering improvements in issues such as inter-team communication, respect of instrumentation installation procedures, and documentation production or access. It was also clear that wireless access to local area network will be essential in the LHC tunnel.