One dee at a time

In July, the four endcap modules of the CMS electromagnetic calorimeter were lowered underground and installed in the experimental cavern.

Each dee is divided into two quadrants made up of 5 x 5 crystal blocks called supercrystals. Each block weighs some 45 kilograms.

The dees (so called because of their shape) are positioned in pairs around the beam pipe, forming two discs closing the barrel calorimeter (see Bulletin nº 43/44 from October 2007). The electromagnetic calorimeter will measure the energies of electrons, positrons and photons. Due to the extreme fragility of the 15,000 crystals that make up the dees (see Bulletin nº 18/19 from April 2008), the technicians have had to work with the greatest caution. The dees were transported from the assembly site in Prévessin to the experiment site at a speed of 5 kilometres per hour, before dawn to avoid disrupting the traffic.

For more information about the installation of the final elements of CMS’s detectors (barrel and end caps of the pixel detectors, preshower detector and the beam control monitors), visit the site of the CMS Times: