The CMS ECAL Enfourneur

View of the extraction and insertion tool of the CMS electromagnetic calorimeter (ECAL) called the 'Enfourneur', during and after modifications. During the third Long Shutdown (LS3), currently foreseen to start in 2025, all ECAL barrel super-modules must be extracted from CMS to replace their electronics with ones better suited for operations with high intensity beams. Each ECAL super-module weighs about 3 tonnes, and must be handled with extreme care to avoid damaging the crystals. A dedicated machine called the “enfourneur” is used to extract and insert back the super-modules inside CMS. The ECAL measures the energy of electrons and photons produced in the LHC collisions with extreme precision. It includes, as main active element, 75848 scintillating crystals made of lead tungstate, a material that is heavier than iron but transparent as glass. The crystals are arranged in a barrel section and two endcaps. The barrel part is made of 36 super-modules, 18 on each side of CMS, each containing 1700 crystals, and is installed in CMS inside the barrel hadron calorimeter (HCAL).