Last weekend CERN organised open-days. Over 70 000 people visited CERN facilities and over 20 000 of them went underground in one of six underground facilities. During this days 2 300 CERN volunteers cared about people's safety and good time. I was one of them. I was an underground guide in LHC Point 6 which is responsible for LHC beam dumping system.
On Monday CERN opened these six underground facilities for members of personnel so I had occasion to see LHCb experiment and once again LHC Point 6 - this time with a camera.
Before LHC was created, CERN worked with LEP (Large Electron Positron) Collider. At those times LHCb cavern was the place of DELPHI experiment. Because disassembling and removing of DELPHI detector would be very time consuming and very expensive, it was decided to keep part of the detector underground and move LHCb a bit aside. Thanks to that I was able to see not one but two detectors.
Then we moved to LHC Point 6 where I was a guide during the weekend. LHC beam dumping system was created because you can't leave circulated protons inside LHC after finishing a day of work. Protons have energy of moving train and if they hit any part of LHC they will destroy it. It is also not so easy to redirect them to some safe place because they travel with almost speed of light. So beam duping system contains three types of magnets that do this job.
Kickers that extract very fast beam from LHC pipes and redirect it a bit up.
MSD that redirect beam a bit left.
MKB that spread beam from 1x1 mm (when it enters the magnet) to 30x30 cm (when beam hits block of 8 meters of graphite). Beam must be spread because even 8 meters of graphite can't handle a moving train that hits 1x1 mm spot.
At the both end of LHC Point 6 you can see LHC circle curvature
I had lots of fun while guiding people through undergrounds of Point 6 and now I saw almost all of CERN underground facilities. Next stop: ALICE and LHC Point 4.