(no subject)
I was lucky enough to be invited along on a tour of the LHC organised by the alumni club of my astronomy course. I signed Isabel and myself up right away, and today was the day. I was warned to be on the lookout for black holes, so I'm looking around nervously - just in case!
The tour didn't take us underground, understandably, but we got to see the above ground testing facility where they tested the integrity of the magnet assemblies before lowering them into position. This is the test bench. It looks like a railway station. It's as big as a railway station.
Here's one of our tour guides showing us one of the dipole assemblies. There are some 1,233 of these dipole magnet assembly modules, which keep the protons moving on a curved trajectory, as well as 392 quadrupole magnet assemblies to keep the beams focused. The two small side-by-side holes in the middle are the beam pipes, where the clockwise and anticlockwise protons are fired through at up to 99.9999991% of the speed of light. The rest of the dipole assembly is taken up with the superconducting magnets, shielding, superconducting wires to supply the kiloamps of current, and liquid helium to keep it all to 1.9 degrees above absolute zero.
Each of the beam pipes is about 4 cm wide by 3 cm high. I'm looking through a cross-section of a shorter one here, laid out for inquisitive visitors like us. This is where 7 TeV protons go. For 27km, and they make that circuit 11,000 times per second. Incredible, hey?
Joining these assemblies is tricky, because when they're cooled to 1.9K, each shrinks by 4.5cm. Hence they need to have corrugated joins, to handle the expansion and contraction. This is life-size but with cutaways so you can see the couplings.
And some of the neatest welding I've ever seen in a machine shop.
The ATLAS control room, not far from the testing facility, is where this is all monitored from. Right up against the glass is as close as we're going to get. It's a truly impressive facility.