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Europe's LHC To Run At Half-Energy Through 2011
quaith writes "ScienceInsider reports that Europe's Large Hadron Collider will run at half its maximum energy through 2011 and likely not at all in 2012. The previous plan was to ramp it up to 70% of maximum energy this year. Under the new plan, the LHC will run at 7 trillion electron-volts through 2011. The LHC would then shut down for a year so workers could replace all of its 10,000 interconnects with redesigned ones allowing the LHC to run at its full 14 TeV capacity in 2013. The change raises hopes at the LHC's lower-energy rival, the Tevatron Collider at Fermi National Accelerator Laboratory in Batavia, Illinois, of being extended through 2012 instead of being shut down next year. Fermilab researchers are hoping that their machine might collect enough data to beat the LHC to the discovery of the Higgs boson, a particle key to how physicists explain the origin of mass."
I'm scared for all the half-lives at risk.
Nope, we need to be fully afraid that it will destroy half the world. Hopefully the other half.
UTF-8: There and Back Again
Frankly, I'm a little sick of the "outrage" every time something doesn't go as planned. Since when does the universe have to play nice all the time?
Science, by its very nature, deals with the unknown. We're at the point now where it looks like we're going to have to assemble thousands of experts, using billions of dollars to continue to make fundamental discoveries. If any of us had a road map, I assure you that we'd use it. This means that sometimes, we spend all that time and energy and hit a dead end.
But here's the cool part: dead ends are sometimes better than confirming what we already knew. There was an interview with a theoretical physicist on the radio the other day, and the interviewer asked him what his worst fear and greatest hope for the LHC was. He said, "They're the same thing. We find out that we were completely wrong about something." This is simultaneously frightening and exhilarating, and it's what makes fundamental research so exciting.
In an equally optimistic point of view, if Higgs boson is later shown to not exist, the Tevatron Collider can claim that it was able to not find it before the LHC!
The failures, or rather misdesigns/misbuilds, are in "copper bus bars". These effectively act as shorts across the superconducting electromagnet coils. Since the coils are normally superconducting (when at cryogenic temperatures), the short does nothing. But if the coil gets ever so slightly above its critical temperature, it ceases to be superconducting. At that point, it still has very very low resistance, but the current through it is so enormous that it heats up rapidly. When it gets to a certain temperature, its resistance becomes comparable to the resistance of the copper bus bar shorting it, and the current starts to flow more and more through the copper, thus protecting the superconductor from getting too much hotter. At least, that's what is supposed to happen.
What is wrong is that some of the solder joints for the bus bars are not good, and have too high of a resistance. A higher resistance in the bus bar system means a higher superconductor temperature before the current starts to flow through the copper, and in the end, this means damage to magnets.
I'm not sure what level of testing was done, but building a short segment and testing it up to slightly above design spec is probably not really feasible. In order to get the particles to the eventual energies, you need the whole ring to be in working order, because it takes tons of complete circles around the ring to accelerate the particles. Injection from the SPS to the LHC occurs at 1/14th the design beam energy, and the LHC ring takes it up from there.
Even if you could inject 7 TeV protons into a short segment of the ring, you'd still not be able to get the design beam intensity that way, because you don't have all 2000+ bunches ready for injection at once.
You could run the magnet intensities up to what is needed to bend a beam in a tight enough circle at high enough energies even without any actual beam in there, and this was probably done. However, quenches (magnets getting above critical temp) happen principally because of the beam. The beam loses particles and energy at a fairly high rate due to a variety of effects, and all those particles and all that energy goes into heating something, usually the bending magnets. I suppose you could do a deliberate quench by playing with the cryo, though. Perhaps that was done, and we were unfortunate enough to have tested only good subsystems this way.
As you may have guessed, I am a particle physicist (on CDF), but not a beams engineer. So, some of the above is guesswork, but I hope I've been able to relieve some of your ignorance.
SIGSEGV caught, terminating
wait... not that kind of sig.