CERN successfully tested sensors and FRAS software (Full Remote Alignment System) on a prototype magnet ahead of the HL-LHC launch.
The HL-LHC is a 27 km long machine that requires components to be leveled with millimeter precision. CERN experts have discovered that the Earth’s shape affects the alignment process. Gelen Menod-Dyran from the BE-GM department stated, “We cannot consider the Earth spherical or flat. The whole complexity of its elliptical form becomes important.”
While the LHC installation and operation revealed similar technological difficulties, the HL-LHC has even higher requirements. The FRAS remote alignment system has successfully passed initial tests, proving its crucial role in ensuring accurate leveling.
The FRAS system consists of thousands of sensors distributed over 200 meters of new magnets in the Atlas and CMS detectors. These sensors allow for remote, real-time adjustments to the component positions without human intervention.
The FRAS system for HL-LHC, which covers 200 meters, introduces several innovations. It utilizes a classic capacitive technique and employs cables that are 120 meters long, designed to withstand extreme conditions, to protect the sensors from radiation.
Additionally, the system incorporates a new technology called interferometry with frequency scrolling (FSI), which measures distance using fiber and special reflective spheres. Menod-Dyran stated, “FSI technology has been developed inside CERN for eight years, and many laboratories have already shown interest in it.”
Following the successful tests this summer, FRAS will undergo further testing on HL-LHC magnets in 2024. The installation in the cave is scheduled for 2027 during a long technical downtime.