The CMS ECAL Enfourneur: a gigantic machine with a soft touch

The electromagnetic calorimeter (ECAL) of the CMS experiment at the LHC is composed of 75848 scintillating lead tungstate crystals arranged in a barrel section and two endcaps. The barrel part is made of 36 supermodules (SM), 2.7 tons each, and is installed inside the CMS magnet. There are 18 SMs on each side of CMS, with each SM containing 1700 crystals. During Long Shutdown 3, all ECAL SMs must be extracted to refurbish the electronics in preparation for HL-LHC. A dedicated machine called the Enfourneur is used to extract and re-insert the SMs inside CMS, with a required accuracy of about 1 mm. In order to speed up the extraction and insertion process, two Enfourneurs will be employed, operating in parallel on both sides. In view of the purchase of the second Enfourneur, the design has been improved, starting from the feedback of past operations. The improvements to the new Enfourneur design include: increased space for the operators, optimization of the operations and the controls with the use of electric motors, and an updated alignment system. Handling plans inside the CMS cavern have been defined in order to be compliant with the rest of CMS structures and procedures.