No LHC beams until next year

(If you read this, you are hereby obligated to read the next post.)

Nope, the verdict is in: the LHC will not be turned on again this year, even for a shortened 10 TeV run.  The restart has been scheduled for early spring of next year, so I’ll probably get very familiar with these 14 minutes of data!

I was in a meeting at CERN when someone ran to the front of the room with a computer, then after letting the speaker finish and setting up the computer to project the press release/e-mail (agonizing moments: it was a Mac), they let us know.  I was worried that the sector with the helium explosion had collapsed like an old mine— there were rumors going around that this is a weak point in the tunnel.  (Of course there would be such rumors.)

I have learned a few more graphic details about the event in the last few days.  First off, it was two tonnes of helium, not one.  But I’ve also learned that this was a more explosive and dramatic event than I had imagined— helium is fortunately an inert gas, but the temperature gradient caused it to explode violently, probably causing physical damage to the nearby components.  And now that section of the LHC is an ice tunnel, maybe with stalagtites hanging down and a Yeti moaning in the distance.  (A Yeti may well replace Big Bird on my diagrams.)  There was enough helium released to replace all the air in a kilometer-long section of the tunnel.  The full tunnel is 27 km long, so I imagine it’s dilute enough to breathe, possibly with a squeaky voice.  (Okay, a high-pitched Yeti.)

One point that I want to set straight is that as far as I understand the term “magnet quench,” this wasn’t a quench.  It was an electrical connector between two magnets which failed under the load of 8,500 Amps of current.  When a superconducting magnet quenches, a small patch of the superconducting coils heat up over the critical temperature, making it no longer superconducting.  It gets warmer, heating up more of the surrounding region, until a runaway effect dumps all of the magnet’s energy into heat and throws things around because strong magnetic fields have just been turned off.  This was less exotic: more like a broken fuse or bad wiring (operating at hundreds of times the normal electrical consumption of a household, but still).

So that’s probably it for the regular (irregular) posts, at least until “spring.”  I should probably sit down and calculate when I’ll next be able to publish a scientific paper.  Hmm.  How tall do you think a Yeti is?

Tags: LHC, physics