Back at CERN! Good to be here, more students coming in, everybody getting pretty excited. Recent progress in the cavern is the installation of the beam pipe on one side. I guess this is pretty hard to imagine, so I thought a picture might help:
So, on the very bottom of the picture you see these copper looking flanges (they’re not copper, I believe they are Aluminum, but it is just a trick of the lighting). That is the very tip of the first Endcap plug. Underneath those flanges will be the Electromagnetic Endcap, we hope! (there’s been some delay, so it is now “critical path”) Extending from that is the beampipe (eventually the plug will slide over the beampipe) which then penetrates the barrel part of the detector. It might help to have a quick glance at the cartoon before trying to understand the following: from the outside radius moving inward (it is cylindrically symmetric, so this the easiest way to describe it) what you can see is
- Muon Chambers/Magnetic Field return – the “M” in CMS stands for Muons! This the is the red layers of steel interspersed with aluminum (silver) muon chambers- there are four cylindrical layers of chambers. The red steel in between is where the magnetic field goes so that it can form a continuous loop (magnetic fields have to go in a closed loop, and they much prefer to go through steel than air). They measure muons via the ionization trail they leave behind, and we know they are muons because anything else coming from the interaction region in the center either won’t penetrate this far to the outer detectors or won’t leave a trail at all (those would be neutrinos…) More…
- Next step in radially: Solenoidal Magnet – the “S” stands for Solenoid. This is the grey collar that looks like it has a whole bunch of metal bands going from the outside to the inside, and every few bands you can see some green cables. The bands are actually cable trays, carrying the cable connections to the inner detectors. The Solenoid itself is 13 m long and has an inner diameter of about 6 m and since it is superconducting cavities inside we can get to about 4 T, making it the most powerful magnet in the world in terms of energy stored. More…