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Building the future of physics

Alan Boyle /

Workers at Fermilab line up the first segments for

an experiment that could set the stage for the

multibillion-dollar International Linear Collider.

Particle physicists can't afford to get too sentimental about where they work. They need bigger and bigger machines to focus on smaller and smaller frontiers - and when they just can't make the machines bigger, they have to blaze a completely new trail to those frontiers.

That's the situation facing researchers at the Fermi National Accelerator Laboratory, near Chicago: Some researchers are squeezing the last ounce of performance out of the 24-year-old Tevatron accelerator, looking for a mysterious particle called the Higgs boson. Others are working on the next big machine, Europe's Large Hadron Collider. And still others have begun building something called "Project X," the prototype for a radically different kind of multibillion-dollar physics machine.

That mega-machine, known as the International Linear Collider, won't become a reality until well after 2012. But lots of experts are already working on the ILC's design - and how to pay for it - because it takes years to go from one generation of supercollider to the next.

"You're completing your experiment, but you're also always looking to the future," said the University of Florida's Jacobo Konigsberg, co-spokesman for the CDF experiment at the aging Tevatron.

The current plan (PDF file) calls for the Tevatron to keep going until at least 2009, and Fermilab's managers have recommended extending its life even further, into the federal government's 2010 fiscal year. "To me, it looks like a pretty straightforward decision," the lab's director, Pier Oddone, told me last week after I toured the site.

Oddone's rationale was that the teams using the Tevatron were "very close to making an important measurement" in the quest for the Higgs boson, the only particle predicted by the Standard Model that has not yet been detected. The Higgs boson has been called the "God particle," because it is thought to be responsible for the masses of other particles. But a better nickname might be the "goad particle," since the quest itself has become a goad for increasingly complex experiments in particle physics.

A major reason for building the Large Hadron Collider is to study the Higgs boson and its effects, and the commonly accepted view is that the LHC will render the Tevatron obsolete. "At some point, when the LHC is working well, it will wipe us out," Oddone told me.

But the LHC's official startup has been delayed from this fall to next spring, and it may take more time than expected for the next top gun to start shooting subatomic bullets. Keeping the Tevatron running through 2010, at an estimated cost of $30 million, would ensure that there's no break in the action. What's more, an analysis of the attributes of other subatomic particles recently hinted that the Higgs boson may actually be lighter than some theorists had thought - and lying in a sweet spot for the Tevatron, between 114 billion and 144 billion electron volts.

"If it is very light, it's not easy to get it in the LHC," Oddone said. "It's not a Day 1 experiment. It's one of the hardest things that the LHC can do. Eventually, they'll get it, no question. But it wouldn't be quickly. ... So there is some reason to run the Tevatron in this very important area."

Colleagues as well as competitors

Once the Tevatron is shut down, that won't be the end for Fermilab. Ironically, teams based at Fermilab play big roles at the Large Hadron Collider as well.

One of those roles was to provide superconducting magnets for the LHC's 17-mile accelerator ring. Earlier this year, Fermilab came in for some unwelcome attention when one of those magnets broke during pressure testing. The magnet failure was cited as a factor behind the decision to delay the LHC's start-up until next spring. 

CERN / CMS Outreach

Scientists can see what's up at Europe's Large Hadron

Collider from Fermilab's Remote Operations Center.

Fortunately, the magnets' design flaw was something that could be fixed in place, and Fermilab spokesman Kurt Riesselmann told me that all the magnets have gone through the required modifications. No problems have turned up in the tests so far, he said.

Once the LHC begins operation, Fermilab will serve as America's primary center for dealing with the data flowing from the accelerator in Europe. A brand-new remote operations center can be seen through a glassed-in wall on the first floor of Wilson Hall, Fermilab's headquarters building.

Particle physics isn't restricted to miles-wide accelerator rings, of course. Oddone also points to Fermilab's role in a plethora of experiments probing the mysteries of the neutrino, dark matter and dark energy, on Earth and perhaps in space. Elsewhere on the astrophysics front, Fermilab is a collaborator in the Sloan Digital Sky Survey as well as the Pierre Auger Cosmic Ray Observatory.

Building a subatomic dragstrip

The most advanced project on Oddone's agenda is Project X, which involves developing the technology for the International Linear Collider. Fermilab's Riesselmann said the Project X linear accelerator would be a "1.5 percent ILC." If Project X gets fully built out, the cost estimates would be in the range of $500 million or more. But if an international consortium gives the go-ahead for building the ILC sometime in the 2010-2012 time frame, Project X would give Fermilab a head start toward playing a lead role in that multibillion-dollar project.

Project X and the ILC would be fundamentally different from ring accelerators such as the Tevatron and the LHC. If you compare the rings to Indy-style racetracks, linear colliders are more like dragstrips. Magnetic forces pull charged particles through a series of "cavities" chained together in one straight line, revving them up to nearly the speed of light.

Alan Boyle /

Workers prepare Fermilab's New Muon Lab for

experiments that could set the stage for a new linear

collider. Blue-green blocks of concrete have been set

up as a radiation shield.

The proposed 20-mile-long International Linear Collider, which currently carries an estimated price tag of $6.7 billion (detectors not included), would not be as powerful as the LHC. But it could smash together electrons and positrons, rather than protons. That's good, because the readings from electron collisions are much more precise than the data from messy proton collisions.

When you're playing with protons, it's like playing pool with a collection of beanbags rather than billiard balls. The electrons are more like balls, and thus easier to manage. But you need a long, straight shot rather than a curved roll to accelerate those electrons to the required energies. That's why Fermilab and other physics labs are turning their attention to linear accelerators.

Project X would start out working with protons, not electrons, and it would be used primarily for neutrino studies. But the technology could be applied to building the electron-smashing ILC - as well as other next-generation linear accelerators. Riesselmann said the applications would likely benefit the general public as well as particle physicists - just as past advances sparked revolutions in medical imaging and cancer therapy.

"With this technology, you can envision hospitals having accelerators for medical applications, or homeland security using them for cargo scanning," Riesselmann told me.

Fermilab has already built its first series of eight cavities for its Project X accelerator, modeled on a German design. Last week, I watched as one group of workers tinkered with the assembly on a shoproom floor, while another group worked on the building space set aside for the project.

Project X would put Fermilab in a good position for getting a piece of the action if the ILC project moves forward, but would yield benefits even if the ILC discussions are hung up in limbo, Oddone said.

"If we've made a lot of progress by 2010 on site selection, on international arrangements, if the LHC is popping out physics that tells us this is exactly what we need to do, then we would move straightforwardly to the ILC," he explained. "If the LHC takes more time to turn on, if the physics is not easy to get, if the countries haven't engaged in discussions on site selection, then you know you have time. In the meantime ... you haven't wasted the technology. You have a vehicle by which you can industrialize in the U.S. This has many virtues."

Oddone hopes Project X will help get America back in the game for international physics projects, after fumbling the ball with the aborted Superconducting Super Collider. But that hope rests on at least one big assumption: that there will be an international physics project to bid on. Like the Superconducting Super Collider, the International Linear Collider could fade away as it gets closer, like a mirage.

The future could well depend on how much comes out of the experiments at the Tevatron and the Large Hadron Collider. If those experiments shed new light on cosmic questions - for example, what we're made of, and where we came from - it may be easier to sell the public on the prospects for more.

"It is a question of priority: Is this important?" Oddone said. "That ultimately rests with the taxpayer. Is this exciting to them, that the country gets involved in exploring this frontier? Or would we much rather have something that's economically competitive tomorrow, and we don't care about the fundamental questions? When you look at a country that is trying to be at the edge of science, as a way to the future, it seems to me that asking these questions - which are the hardest questions in physics - is an important thing to be engaged in."

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