CERN – Tour of CMS and AMS

03 Aug. 2013

We started at noon with about 30 of us arriving early to have an informal lunch at the CERN restaurant. On the short walk inside the lab, we passed through a mini-exhibition of detectors from CERN’s past (Gargamelle / BEBC bubble chambers and LEP RF cavity) as well as an LHC dipole magnet. After lunch we returned to Reception to meet with the rest of our group. All together there were 50 of us. A coach took us to our first stop, the CERN laboratory on the French side of the border (Prevessin), where we visited the AMS Control Room ( and the CERN Control Centre ( AMS (Alpha Magnetic Spectrometer) is a cosmic ray detector that is mounted on the International Space Station. The detector is used to study the matter/antimatter asymmetry and clues for the existence of dark matter. The collaboration is led by MIT professor, Samuel C. C. Ting.

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The CERN Control Centre brings together the control rooms of the eight accelerators at CERN. The LHC beams (protons and lead ions) are constructed via an injector chain that includes the PS (Proton Synchrotron) and the SPS (Super Proton Synchrotron).

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We then continued our tour to CMS ( located at the intersection point of the LHC directly opposite of the CERN main laboratory, about a 15 minute drive away. For safety reasons only a certain number of persons were allowed to go down to the detector, located 100 meters below ground, at any one time. We split into several groups and took turns either visiting the detector or the control room and exhibits above ground. During the descent, we were required to wear hard hats and we were given some safety instructions.

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CMS is the general purpose detector that was used in the co-discovery of the Higgs boson (along with ATLAS). The international collaboration of physicists and engineers number around 3000. Although the physics goals of the two detectors are similar, CMS has a different design and is smaller than ATLAS. Nevertheless, CMS appears to be an enormous apparatus. The compact design allows for both the tracker and the calorimeters to fit into the superconducting solenoid magnet. The muon chambers are located just outside the magnet. As the detector is being refurbished during the downtime, the forward calorimeters and muon chambers were pulled out to reveal the detector interior. The amount of cabling required for all the sub-detector components was quite impressive.

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We would like to thank the CERN Visits Service for setting up the infrastructure and organisation that makes a visit like ours possible. The Service accommodates 100000 visitors per year and coordinates the volunteers (physicists and engineers) who act as guides. We would especially like to thank the seven young physicists who took the time out from their research activities in order to guide us on the tour.

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See you at our next event!

Makoto Ikeda