“It is not sorcery,” proclaims the white letters on the large blue section of pipe poised on the extended flat bed of a tractor trailer truck. The truck and its message were part of the scenery at the CERN open house last weekend.
Why CERN—the European Center for Nuclear Research—feels obliged to proclaim that it is not engaged in witchcraft may be debatable, but it was a recurring theme at the research consortium’s highly successful event, which drew nearly 70,000 visitors and paralyzed traffic for miles around. In the spirit of the occasion, an attractive software engineer at one of the giant Large Hadron Collider’s service points in Versonnex, sported a conical witch’s hat while doling out cryogenically frozen yogurt to an enthusiastic junior audience.
She is not alone. Thousands of curious residents stood in line for up to three hours for the privilege of spending 15 minutes in the tunnel that will house the proton beams. Among the attractions, a fleeting glimpse of the gargantuan, 12,000-ton, solenoid that weighs as much as the
Leonardo, a Portuguese nuclear physicist, who did his PhD at MIT in Cambridge, Massachusetts, discretely tucked his radiation dosimeter inside his red wind breaker. Then, noticing that I was studying the words “radiation dosimetry” printed on the blue lanyard around his neck, and seeing that I was wearing a day-glo orange arm band that said “Press,” he decided to come clean. “It’s just a safety precaution,” he said. “When we fire up the streams in the tunnels, they are radioactive for a few weeks afterwards. But it is nothing to worry about, although there are some areas, I would find uncomfortable to spend much time.”
“Uncomfortable, or lethal?” I asked. “Uncomfortable,” he said. Another guide volunteered that the amount of radiation he was exposed to in a year was less than a typical chest X-ray. “If you really want to avoid radiation,” he added. “Get rid of your bones. They are a natural source, and don’t forget that you get higher readings of natural radiation the higher you go up in the mountains.” Still he admitted that it was part of the job. “It states in your contract that you are aware that you will be exposed to some radiation.”
The actual stream of protons that the LHC will generate will only be about a millimeter or less in diameter. “It’s really tiny,” one of the guides said. “The collision is like a mosquito bite.”
Maybe, but the stream of protons would very likely cut through just about anything or anyone who got in its way. And the beam is not the only thing that can go wrong. Last year, a magnet literally leaped out of its emplacement when the power was turned on. The plan, this time around, according to the CERN guides last weekend, is to start the system up in a few weeks with low power tests so that the beam can be focused and the machinery can be tested. The power would be gradually increased until the end of the year. The real experiments would probably start up sometime next year.
The velocity will approach the speed of light. The pipes that carry the proton streams will be kept under vacuum to avoid accidental collisions with other particles. When the two streams do collide, the enormous energy will create new particles that will be registered by a vast array of sensors. The Holy Grail is a particle called “Higgs Bosun,” which some refer to as the “God particle,” and which has so far only been identified in theory. It may be the missing link between energy and matter. To generate the force needed to accelerate and control the proton stream, CERN has employed a vast array of super-cooled magnets, which function at around -270 degrees centigrade. The magnets are cooled by liquid helium. “We use so much helium,” Leonardo explained, ”that it affects the world market. In fact, if we had to store all of our helium outside the collider, we wouldn’t have enough room.”
The current experiments with the LHC are actually a follow-up to an earlier series of experiments, carried out on its predecessor, the LEP—Large Electron Positron accelerator--built in 1989. The LEP was the most advanced accelerator of its time, and it was so sensitive that measurements were affected by changes in the gravitational pull resulting from variations in the water level of Lake Geneva.
But electrons were simply too light, and too difficult to accelerate to the energy levels that the LHC can achieve. Protons have more mass, and a bigger impact when they collide. Around 2,000, the LEP program ended. Its equipment was removed from the tunnel, and scientists began installing the LHC from scratch.
Like most experiments in pure science, the experiment which CERN is planning will either confirm or negate theories about the basic nature of the universe that are still debatable.
The program, which is estimated to cost between $5 billion and $10 billion, might seem like a luxury just to prove a theoretical notion, but there are collateral advantages. When the original LEP was under construction, the US still led the world in particle physics. The US had plans to build a super collider in Texas that would have outgunned the LEP and the LHC. But Ronald Reagan decided that it was too much money to spend on something the importance of which he barely understood. The Texas super collider was cancelled, and LEP remained the world’s most powerful accelerator by default. Scientists, who had dreamed of doing research in the US, began thinking about moving to Geneva instead. With them went a great deal of the acquired skills required to prove that a theory conforms to a physical reality.
The far more powerful LHC is likely to accelerate the decline of US dominance in the field. Walking through the tunnel, 100 meters under Cessy, Leonardo noted that the accelerator at Fermilab, outside Chicago, would most likely shut down later this year, as will Stanford’s Linear Accelerator. I asked Leonardo if the scientists who had been working on those accelerators would feel obliged to move to Geneva so that they could work at CERN. “They are already here,” he said.
--Cessy, France, May 2008