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CMS Ecal End Cap

Customer: Rutherford Appleton Laboratories

TM Specialist Engineers were awarded a contract to supply manufactured equipment for the CMS (Compact Muon Solenoid) that will be used at CERN in Switzerland. The CMS is a general purpose proton – proton detector and Rutherford Appleton Laboratories will perform an experiment called ECAL (Electromagnetic Calorimeter) to try to measure the energy of electrons, positrons and photons. This is done by using two end caps retaining 340 units holding 25 lead-tungstate crystals each. The experiments main aim is to isolate two atoms and accelerate them to collide together and hopefully break up into a number of smaller units, thus generating energy. All of the crystals are angled in such a manor that all the crystals aim at a central focal point where the collision will take place. The crystals absorb the particles and produce light. The amount of light produced is proportional to the energy of the particle.

(More information about the experiment can be found on the CERN web site http://cmsinfo.cern.ch)

TM Engineers were chosen on the basis that we supplied and project managed the manufacture and procurement of a number of large items including semi-circular Back Plates and Support Rings along with the End Cap Retaining Units.

Due to the diverse nature of some of the items required and the accuracy required, this demanded a great deal of co-operation working with several selected partners.

To assist with maintaining the very tight tolerances required on the Base Plates, the criticality of maintaining a constant temperature whilst machining was adamant. We therefore designed and developed a bath containing a temperature maintained coolant that ensured no cold spots occurred. The Back Plates were individually immersed and held whilst machining occurred ensuring the aluminium remained stable throughout the lengthy machining process.

Upon completion of machining, the Back Plates then had a series of small thin walled Stainless Steel pipes attached in a very complex pattern to allow the plate to remain at a constant cooled temperature of 18°C throughout it’s operational life. The pipes were pressure tested to 25 Bar prior to release with great success.

Recent fit up trials at CERN have provided Rutherford Appleton Laboratories with the results that were required and TM Engineers hope that further work will emerge from this highly successful project.