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Physicists Flip the Switch on World's Most Energetic Particle Smasher
10 September 2008 (All day)
MEYRIN, SWITZERLAND--If particle physics were a baseball game, then researchers here at the European particle physics laboratory, CERN, would have just hit a first-swing, out-of-the-park home run. This morning, they tried for the first time to pass a beam of particles all the way around the world's new most-energetic atom smasher, the Large Hadron Collider (LHC). They succeeded on the first attempt. A process that could have taken days had things gone badly was over in just 58 minutes. "It's fantastic," says Jonathan Ellis, a theoretical physicist at CERN. "It's amazing that this device, which is so complicated, basically worked on the first try."
The achievement marks the beginning of a new era of exploration in particle physics. Fourteen years in the making, the mammoth LHC will accelerate protons to energies seven times as high as have been achieved by the current energy champ, the Tevatron Collider at Fermi National Accelerator Laboratory in Batavia, Illinois. In the LHC's twin rings, beams will circulate in opposite directions, and the protons will collide head-on in the hearts of four gigantic particle detectors spaced around the ring. Those collisions could produce the missing link in physicist's current standard model of the known particles, the famed Higgs boson, which physicists say gives other particles their mass. The collisions might also produce a whole slew of new particles, open new dimensions of space, or even create tiny, fleeting black holes.
But first, physicists, engineers, and technicians had to get the $5.5 billion machine running. Researchers had already passed protons into and partway through both rings. But they hadn't threaded a beam all the way around, and even minutes before the test this morning, accelerator experts said that key step could be a challenge. "There is this other half of [each] pipe that has never seen the beam before, so there could be an obstacle" to success, said Georges-Henry Hemelsoet, an accelerator operator at CERN.
Adding to the pressure to succeed, CERN officials invited the press to cover the event. More than 300 journalists flocked to witness the work. Only a few television journalists were allowed into the accelerator's control room. The rest of us were herded into the Globe of Science and Innovation, an odd wooden sphere resembling an enormous Ping-Pong ball that was a hand-me-down gift from the Swiss government, where we watched the proceedings on television.
Being there was a bit like watching the launch of a rocket. Banks of computer monitors packed the accelerator's main control room, and scores of scientists and engineers stared intently at screens or milled about talking in hushed tones. But in the end, there was no rocket roaring into space, no plume of flame. The machine looks the same, running or not. So researchers have inserted thin screens into the ring, which fluoresce when the protons pass through them. We literally watched the researchers watching these hazy images on yet other televisions. Running commentary from Nisha Pillai, an announcer for the BBC, raised an occasional giggle: "You've heard of masters of the universe? At CERN we have masters of the beam."
Still, a pleasant tension developed as researchers pulled out beam stops one by one to allow bunches of protons to pass farther and farther around the first ring. At 9:34, 4 minutes after the beginning, they passed the protons through one octant of the ring. Eleven minutes later, the beam passed halfway around. At 10:14, Pillai exclaimed, "Just one more section to go!" And when, at 10:28, the beam passed all the way around one ring--the official objective of the day--even the reporters applauded. In the control room, CERN's Lyndon Evans, leader of the LHC project since its inception, quipped, "I've won my bet," later explaining that he wagered with another researcher that the beam would go around in less than an hour. At 3 p.m., researchers threaded protons through the countercirculating ring.
The easy start raises the hopes of experimenters with the four big detectors--known as ATLAS, CMS, ALICE, and LHCb--that they will soon have collisions to study. "The atmosphere in [the ATLAS control room] is absolutely electric, more than 100 people clapping and cheering," says CERN's Phillippa Wells. "Because it proves that the accelerator is ready to run." But physicists also caution that today's success is just the first step and that many hurdles may lie ahead. The next job for accelerator physicists will be to boost particles from the low "injection energy" at which they coasted today to an energy 10 times higher and to bring beams into collision. That could take a month or two.
For a physicist from the United States, the celebration conjures thoughts of what might have been. An even bigger, more energetic particle smasher, the Superconducting Super Collider (SSC) in Waxahatchie, Texas, was terminated, less than half-completed, by Congress in 1993. "Had the SSC not been canceled, we would already know the answers to the first round of questions we are going ask [at the LHC]," says Robert Cousins, an experimenter from the University of California, Los Angeles, and a member of the CMS team.
Particle physicists generally agree that the future of their field rides on what the LHC finds. If it coughs up lots of new particles and phenomena, there may be a push to build another, complementary type of collider to study those things in detail. But if the LHC sees only the expected Higgs boson and nothing else, few expect politicians will be keen to pay the billions of dollars needed for such a facility. CERN researchers have started the next great particle smasher; they may have also started the last.