77 Tonnes of ATLAS Shielding on the Move

On 22 July, CERN teams successfully completed the first major transport operation of LS3. A 77-tonne shielding component, known as the JFSU, was moved from the surface hall above the ATLAS experiment to Building 191 on CERN’s main site.

The JFSU is a massive metal structure that forms part of the ATLAS radiation shielding. Two JFSUs are installed around the particle beamline on either side of the ATLAS detector, helping to protect muon chambers from background particles produced in secondary particle interactions.

As part of the High-Luminosity LHC (HiLumi LHC) upgrade, the JFSU must be specially modified. From January 2027, a CERN robotic team will precision-machine additional slots into the component to route services to new vacuum units. Approximately one tonne of material will be removed during a three-month operation, with this first JFSU scheduled to return to ATLAS in April 2027.This complex logistical operation marked the start of the Collider-Experiment Interface activities (WP8) during Long Shutdown 3 (LS3) and brought together teams from WP8, the ATLAS Collaboration, CERN Radiation Protection, CERN Safety and CERN Heavy Transport. Similar transport operations will take place in coming years for the second JFSU and two other shielding elements.