The Large Hadron Collider: What Could Possibly Go Wrong?

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This morning, at 3 a.m. EST, the European Organization for Nuclear Research (CERN), flipped the switch and circulated the first proton beam around the Large Hadron Collider (LHC).

The LHC, for those of you that have been hiding on Mars, in a cave, with your fingers in your ears, is the world's largest particle accelerator (the underground circular tunnel its housed in has a circumference of 17 miles and straddles the border between Switzerland and France, crossing it at four points). By colliding opposing beams of protons, CERN scientists intend to fill in the gaps that currently exist in the Standard Model, re-create the conditions that existed an instant after the big bang and get their hands on the Higgs Boson, the only particle predicted by the Standard Model that hasn't been found.

The idea of a ginormous particle accelerator knocking protons into each other at nearly the speed of light has some people"¦concerned. Despite the analysis performed by the LHC Safety Study Group, their conclusion that the LHC posed no conceivable threat, a second review by the LHC Safety Assessment Group and their conclusion that the LHC wasn't dangerous, two lawsuits, one in the U.S. and one in Europe, have been filed to keep the hadrons from colliding (if you were wondering, a hadron is bound group of quarks, and also really easy to misspell as hardon).

What are these people so worried about? Well, just the little matter of doomsday"¦

Back in (micro) Black (holes)

Much of the legal challenge to the LHC revolves around the slim chance that two quarks, one from each proton beam zipping around the collider, both endowed with immense energy inherited from the protons that contain them, could get too close to each other, collapse under their own gravitational interaction and create a small black hole. That gravitational interaction, many physicists have noted, needs to be really strong, though. For any scenario where a black hole pops up in the LHC we'd have to assume the existence of extra dimensions accessible to gravitons (the hypothetical particles that mediate the force of gravity), but not the other particles at play in the collider.

A planet-eating (or even a Switzerland-eating) black hole being created by the LHC would be, in a word, a long-shot. We've got room for error, though. The same reasoning that suggests creating black holes is possible also says that those black holes will evaporate because of a process called Hawking radiation. As much as black holes suck, they also radiate some energy out. The intensity of this radiation is determined by the temperature of the black hole, which is inversely proportional to its mass, so the very tiny black holes that the LHC might maybe manage to create would only be there for a fraction of a second before evaporating.

Keeping Proton Beams in Line

Even if a black hole comes and goes in the blink of an eye, the LHC is still a serious piece of machinery. During operation, the two proton beams will carry a total energy of 724 megajoules, equivalent to the energy of 380 pounds of TNT detonating. But it gets better! The magnets that keep the proton beams on their path during experiments will have a total stored energy of 10 gigajoules. That's the same amount of energy created by 2.4 tons of TNT going off.

With that much energy in one place, even small malfunction could be disastrous. Once the particles are set loose on their demolition derby, is there any way to shutdown the whole operation if there's a technical problem?

Well, duh. CERN spent almost two decades devising a system of fail-safes for the collider. The longer the proton beams whip around the track, the greater the chance that they'll become unstable, so CERN does the same thing to the beams that the nuns did to me in grade school: make them stand in the corner and think about what they've done.

When its time to replace the beams, the old ones are deflected by "kicker" magnets out of their circular path and steered by "septum" magnets (if you're thinking that the LHC is the world's largest collection of weird magnets, you're wrong; that would be my grandmother's fridge) into absorbers called beam dump blocks.

On its way to the dump block, the beam passes through "“ you guessed it "“ more magnets, which fan the protons out and lower the beam's intensity. Inside the beam dump cavern is the block, a 10-ton, 27-foot long graphite cylinder encased in steel and concrete. Quite a roadblock, but still easy enough for the proton beam to eat through, so CERN engineered things so that the beam is "scanned" onto the cylinder in a pattern instead of hitting it at just one point with full strength.

September 10, 2008 - 3:00am
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