STEVE INSKEEP, host:
All right. This is the final month of operation for a massive and sophisticated piece of scientific machinery. It is designed to help scientists understand what makes up the universe at its most basic level. It smashes bits of atoms together and then sifts through the tiny bits of subatomic rubble. For a quarter of a century, it was the most powerful machine that did that. NPR's Nell Greenfieldboyce reports on the end of the Tevatron and what American scientists hope will replace it.
NELL GREENFIELDBOYCE: About an hour west of Chicago is the Fermi National Accelerator Laboratory. Fermilab covers a little more than 10 square miles, and on the surface seems like a nature preserve. There's woods, a herd of buffalo and acres of restored prairie.
Dr. DMITRI DENISOV (Physicist): Wow. Look, it's beautiful. I didn't even know about these flowers. Look at this.
GREENFIELDBOYCE: A physicist named Dmitri Denisov walks up wooden steps to the top of something that looks like an abandoned railroad bed.
Dr. DENISOV: The first time I came here was 1989. So - and I came as a young sort of scientist from Soviet Union.
GREENFIELDBOYCE: Denisov came because of what he's standing on: the Tevatron. This tall mound of dirt stretches off into the distance. It forms a huge circle nearly four miles around. Beneath it is a tunnel; a high-tech race track for protons and anti-protons. They accelerate to almost the speed of light, then slam together. Their collisions spew out the hidden particles that make up matter.
Dr. DENISOV: I remember sort of coming to this point, looking and saying, wow. That's really a big machine.
GREENFIELDBOYCE: At the time, the biggest in the world. Denisov is not the only scientist who was drawn here by the power of the Tevatron to probe the building blocks of the universe. This is where the elusive top quark was discovered and where theories get tested.
(Soundbite of people talking)
GREENFIELDBOYCE: In one windowless control room filled with dozens of computer screens, researchers monitor subatomic collisions 24 hours a day. On the cinder block wall there are clocks showing time zones across the world because so many researchers came here from abroad.
Dr. DENISOV: For example, in India or in Russia or in Vietnam or in China. So, it's a little bit just to make people feel more at home here in, you know, control room at Fermilab.
GREENFIELDBOYCE: But at the end of September, this homey control room will go dark. In a special ceremony, officials will shut down the Tevatron. It's been made obsolete by the Large Hadron Collider near Geneva, Switzerland. Its circular race track for particles is 17 miles around. Denisov says this new collider is now the big draw for the world's physicists.
Dr. DENISOV: And many people, including people who work here at the Tevatron, are moving where the science is.
GREENFIELDBOYCE: Scientists here do still hope to make one last big discovery in the few weeks the Tevatron has left, about a particle also being chased in Europe.
Dr. ROB ROSER (Physicist): The big thing going on right now in terms of particle physics is the so-called race for the Higgs boson.
GREENFIELDBOYCE: That's Tevatron physicist Rob Roser. He says the Higgs is a particle that could explain one of the big mysteries of science: why things have mass.
Dr. ROSER: So, we're just hanging on, trying to get every last collision we can before we turn off to see whether we can make a statement, an important statement about it.
GREENFIELDBOYCE: So, it sounds like, you know, you all are wanting to sort of go out with a bang, as it were.
Dr. ROSER: We want to go out sprinting across the finish line, not crawling, yes.
GREENFIELDBOYCE: Even so, the end is looming for the Tevatron and researchers are reminded of that every time they go to have lunch.
(Soundbite of people talking)
GREENFIELDBOYCE: Right next to the main cafeteria at Fermilab is a new control room with a glass wall. Through it, you can see monitors linked to the Large Hadron Collider. This is so scientists can run experiments remotely on the huge European machine, which the United States contributed money to help build.
Dr. PIER ODDONE (Director, Fermilab): It's a very important part of the American program to actually exploit the Large Hadron Collider.
GREENFIELDBOYCE: Pier Oddone is the director of Fermilab.
Dr. ODDONE: I would say the mood of the community is that this is a unique time in the history that we're opening a regime where all of a sudden we have access to 10 times the energy that we could produce here at the Tevatron.
GREENFIELDBOYCE: That doesn't mean American scientists don't feel sad at losing the status that comes with having the world's best physics machine. Oddone would like to see the next big thing built right here. But that's no easy task when budgets are shrinking for the physical sciences. After all, Europe's Large Hadron Collider cost around 10 billion dollars.
Dr. ODDONE: It just simply seems very difficult, given debt issues, deficits and all of that, to ask for the required increases that we would need to build the biggest machine.
GREENFIELDBOYCE: So, instead of a bigger machine that can produce even more powerful collisions, they hope to build something different - a new machine that would produce a record number of collisions. Having lots and lots, even if they're less powerful, should let scientists see rare events that hardly ever happen.
Dr. STEVE HOLMES: There's things that happen, you know, one of out of 10 to the 17th times, which is, you know, I don't know, it's like a billion billion or something. So, it's things that happen really, really rarely.
GREENFIELDBOYCE: Steve Holmes leads the team working towards the proposed new accelerator, which they're calling Project X. He showed me a long concrete bunker painted mint green. Inside it, scientists are testing new technologies needed for Project X. It would cost a couple billion dollars and would do things the collider in Europe can't. It would be the best facility in the world for studying tricky particles like neutrinos.
Dr. HOLMES: As long as, you know, there's a commitment in the U.S. to be a world player in particle physics, which I got to believe there is, Project X is going to have to be built.
GREENFIELDBOYCE: Holmes says if Project X gets funding, it could be built by the end of this decade, and he hopes it will.
Dr. HOLMES: You know, we don't always have to be number one. It's natural that, you know, the lead goes back and forth across the ocean. But I think we always got to be in a position when the lead went someplace else, we got to plan to get it back here.
GREENFIELDBOYCE: Once the Tevatron shuts down, it won't be disassembled right away. Instead, its tunnel will be opened up to the public as a kind of museum, to let people see the vast equipment that once revealed incredibly tiny parts of the universe.
Nell Greenfieldboyce, NPR News.