Eight-month delay for LHC

Nature News reported on the accident at the Large Hadron Collider, Eight-month delay for LHC. What strikes me is how enormously huge this project is. When you read about it, it seems like you can grasp what's going on, but as you read further it just gets huger and huger. Here are three paragraphs from the story, with my commentary:

"Officials at CERN, Europe's particle-physics laboratory near Geneva, Switzerland, say that the time is needed to overhaul a sector of the 27-kilometre-long machine, after an electrical failure on 19 September caused some 6 tonnes of ultra-cold liquid helium to leak into its tunnel. A preliminary report issued on 16 October says that as many as 29 of the nearly 10,000 magnets used to guide the accelerator's proton beam will need to be replaced. Further magnets may need to be removed and inspected, and modifications must also be made to prevent future accidents. 'It's a serious incident,' says James Gillies, a spokesman for the laboratory.'

So, 6 tonnes of liquid helium sounds like a big deal. 29 out of 10,000 magnets doesn't sound too bad. Then you read...

"Still, CERN is confident it has the resources to make the repairs. No more than 24 dipole magnets and 5 quadrupole magnets were damaged; CERN has 30 dipole magnets — each weighing 35 tonnes — in reserve, as well as sufficient quadrupoles, says Gillies. Replacement magnets are already being tested in a facility above the buried accelerator tunnel. Nevertheless, Gillies says that the damage will take all of CERN's winter shutdown period to repair. Not including labour and the spares, the work will cost an estimated 100,000 Swiss francs (US$90,000), he says."

Each "magnet" weighs 35 tonnes, which is a metric tonne. So these are just over 77,000 lbs each! Ok, that could take a while to replace. Still I'm picturing these giant cranes lifting these huge magnets and then try to imagine all this happening underground. But then...

"The LHC's superconducting magnets generate enormous fields by circulating huge electrical currents with virtually no resistance. To work correctly, they must be immersed in liquid helium and kept at a temperature of just 1.9 kelvin. During the 19 September test, the accident report says, a weld in a superconducting wire connecting two magnets heated above its operating temperature. That in effect turned the wire into a resistor — causing a massive 8.7 kiloamps of power to arc through the liquid helium and puncture into the surrounding vacuum vessel."

These 77,000 lbs magnets are each immersed in liquid helium at -456.25 degrees Fahrenheit. And the LHC has 10,000 of these!