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Fermi National Accelerator Laboratory

The dual rings of the Fermilab accelerate subatomic particles to near light speed and scientists unravel the mysteries of the universe from beams of colliding particles. The lower ring injects particles into the main Tevatron acclerator.


Fermilab continues to search for the building blocks of the universe

by Tyler Smith
March 03, 2010


FERMI

Tyler Smith/MEDILL

Ian Shipsey of Purdue University uses a fruit diagram to demonstrate how "high-energy" fruits might collide, transforming their energies into other objects. Shipsey, a Fermilab physicist, uses the diagram to explain how Fermilab's accelerator works.

From above, the atom smasher ring at the Fermi National Accelerator Laboratory looks like a large, circular moat.

But, instead of a fortress at the center, bison roam in a snow-covered prairie. The animals graze just 25 feet above  America’s largest particle accelerator at Fermilab in Batavia.

Driving into Fermilab’s 6,800-acre research park is like entering a parallel world. And it might as well be one. Experiments carried out here continue to push at the boundaries of our perception of the universe.

The accelerator, known as the Tevatron, lies beneath a circular river engineered at the laboratory and previously used for cooling the accelerator. The machine hurls protons around the 4-mile ring at the speed of light in opposite direction. When the beams of particles collide, subatomic debris explodes into detectors that analyze the fragments.

With an annual budget consistently set at about $400 million, scientists at Fermilab are trying to answer questions that at times seem more philosophical than scientific. What gives an object mass? What are the fundamental components of the universe? How do they behave?

Fermilab has been working on answering these questions since the facility opened in 1974, but there’s a new kid on the block - the Large Hadron Collider in Geneva, Switzerland. After a false start in 2008, the LHC became operational in November 2009.

Fermilab scientists are feeling the pressure. The Tevatron operates at 1 TeV, or a trillion electron volts, but it is no longer the most powerful machine of its kind.

The Large Hadron Collider is expected to have collisions measuring 7 TeV by the end of March- collisions seven times more powerful than at Fermilab. “It’s certainly the biggest scientific instrument of its kind ever built,” said Joel Butler, an operations manager at Fermilab.

“Tevatron, until very recently, was the most powerful particle accelerator in the world,” Jackson said. “But rumors of Fermilab’s imminent demise have been greatly exaggerated.”

The Tevatron will remain operational until 2011, a year later than previously expected. Delays with LHC construction have helped keep the Tevatron active in recent years.

But after the Tevatron stops smashing atoms, scientists at Fermilab will focus on related experiments in an effort to answer the same fundamental questions about particle physics. Plans are already underway to reuse part of the land occupied by the Tevatron for an experiment known as Project X.

Project X, referred to by Fermilab scientists as the proton blowtorch, would create intense beams of particles to be used for further study. The particles would be boosted to their top speed in a linear accelerator and could be directed off site or smashed into a barrier at Fermilab to examine the subatomic debris.

Fermilab is already involved in the study of neutrinos – uncharged, miniscule particles that easily travel through matter. Four hundred feet under the ground, a beam of neutrinos is shot through 500 miles of rock to a scientific facility in Minnesota. Scientists are trying to analyze if the distance has any effect on the neutral, invisible particles.
     
The Large Hadron Collider, like the Tevatron, uses powerful, super-conducting magnets to accelerate positively charged protons through a 17-mile ring. Protons are accelerated to roughly the speed of light around the ring and collide with each other in a specially designed chamber.

The superconducting magnets that propel the particles around the ring are kept at a temperature just above absolute zero- the temperature at which all matter stops vibrating. “The pipes [at the LHC] are actually the coldest place in the universe,” said Butler. “They’re colder than deep space.”

However, when the two particles traveling at the speed of light collide, some of the energy of the protons is converted into matter. Strange new particles are ejected from the resulting explosions, mimicking the particles formed in the first moments after the Big Bang.

“We slam these particles together, two protons coming from each direction, and all kinds of stuff flies out,” said Butler. “It’s like a fireball and as the fireball cools, it spews out all sorts of stuff.”

Sensitive detectors and computers analyze the subatomic particles created in the collisions. One of the primary goals of both Fermilab and the LHC is to find a theoretical particle known as the Higgs boson. According to the theory, this particle supplies matter with mass. For this reason, some scientists call the elusive Higgs the "God particle."

“We know that you can understand the universe as a whole by understanding its tiniest constituents,” said Ian Shipsey of Purdue University, who works as the coordinator of the Large Hadron Collider’s Physics Center. “Fundamental science creates incredible possibilities.”

“A lot of the things we’re looking for are extremely rare,” said Stefan Soldner, a University of Manchester scientist conducting an experiment at Fermilab. “That means we have to collect data about collisions over a long period of time.”

In terms of data collection, Fermilab has a clear advantage due to the length of time the Tevatron has been operating. “That’s one of the reasons why the Tevatron is still very competitive in this game because we have collected a huge data set" over the past years, Soldner said. 

In order to maximize results, scientists at Fermilab and the Large Hadron Collider work together on a daily basis.

The collaborative effort should pay off in the search for the Higgs and other undiscovered particles. “Then they have a chance of seeing just enough Higgs particles in their data set to say there’s something,” Soldner said.