Tevatron Shuts Down After 28-Year Run

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Fermilab director Pierre Oddone confessed that he had a bit of a bad dream the night before today's final shutdown of the laboratory's flagship accelerator, the Tevatron.

There has always been "a certain spirit of rebellion and independence" among the physicists who work on the two main detector experiments, CDF and D-Zero. It wasn't enough to give an order; the scientists usually wanted to know why they should follow it, an attitude that Oddone deems "healthy in many ways," even if it sometimes caused delays.

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Knowing that culture, Oddone dreamt that when he gave the order to shut down each of the detectors in turn, instead of responding promptly, the teams of scientists rebelled and barricaded themselves behind the doors to their respective control rooms instead, responding, in essence, "Make me!"

Fortunately, that didn't happen today during the live Webstreaming of this historic moment in particle physics. It might have been a sad, reflective moment, but everyone played their respective roles to perfection as first CDF, then D-Zero, dutifully powered down their detectors.

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Then it was time to go back to the Main Control Room, where Oddone and other past Fermilab directors — Leon Lederman, John Peeples, and Michael Witherell — were waiting for the final shutdown.

The honor of pushing the two buttons (one red, one green) fell to Helen T. Edwards, one of the few women in a sea of white men (physics isn't the most diverse of scientific fields), who first led the effort to design and build the Tevatron.

Thomas punched the red button to shut down the proton beams being pumped into the accelerator ring. We all watched the computer display showing the red line indicating the beam's presence in the collider drop to zero.

Then she pushed the green button to shut down the high-voltage current supplying the superconducting magnets — except this time, nothing happened. The green line on the computer monitor refused to drop, until Thomas punched the green button again for good measure. Then, reluctantly, the current went to zero. "I guess it didn't want to give up so easily," joked Bob Mau, head of the accelerator division operations department.

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And then it was over: 28 years of groundbreaking physics research, including the discoveries of the tau neutrino and the top quark. (An interactive list of milestones at the Tevatron can be found here.) Any remaining particles were diverted into a metal target to absorb them, and the superconducting magnets will slowly heat back up to room temperature over the next few weeks. Then crews will start removing all the fluids and gases involved in conducting the experiments.

To those who worked there, the Tevatron is "more than a machine, it's a living creature that has the ability to see the microscopic quantum world," CDF scientist Ben Kilminster — who was in the 5th grade when the Tevatron first came online in 1985 — said as he and his team shut down their detector. "So it's going to be with heavy hearts that many of us watch it close its eyes to this world that has captivated us for so long."

Now Fermilab will enter a new post-Tevatron era of what Oddone calls the "intensity frontier": packing as many particles as possible into the smallest possible beam, enabling high-precision measurements to aid in the search for very rare processes in nature.

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Future experimental efforts will focus on neutrinos, cosmic rays, muons and kaons, and the ongoing search for dark matter and dark energy, as well as potential spinoff technologies for clean nuclear energy and handling nuclear waste.

All good accelerators eventually give way to bigger, more powerful machines, and I don't know any physicist who begrudges the passing of the worlds-highest-energy torch to the Large Hadron Collider. What's different this time around is that there is no US-based machine waiting in the wings to take its turn. Good physics will continue to be done, but America has largely ceded its leadership role in particle physics.

That would make Robert Rathburn Wilson, the very first director of Fermilab, very sad. When it was first being built, he made sure to make room for a small herd of American bison to live on the grounds, representing the frontier of physics. Wilson resigned in 1978 in protest over funding cuts for the lab, just before construction began on the Tevatron.

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A bit of a frontiersman himself, he was always a powerful advocate of pushing the frontiers of physics. Back in 1969, the Congressional Joint Committee on Atomic Energy convened in Washington, DC, to hear testimony from a number of scientists about building Fermilab. During the hearing, then-senator John Pastore questioned Wilson about what the proposed accelerator might be good for — national defense? Wilson's reply:

"It has only to do with the respect with which we regard one another, the dignity of man, our love of culture. It has to do with: Are we good painters, good sculptors, great poets? I mean all the things we really venerate in our country and are patriotic about. It has nothing to do directly with defending our country except to make it worth defending."

Accelerators can, and do, have useful afterlives, giving rise to all kinds of valuable spinoff technologies with the potential to make our world a better place; the Tevatron will be no exception.

But that's not, ultimately, why we do the kind of fundamental, curiosity-driven physics research for which the accelerator is justly famed. And with its passing, a little bit more of that bold frontier spirit passes with it.

Image credit: Fermilab