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by Eric Caron, Jennifer Purdes, and Michelle Walter
What do you get when you combine over 80,000 tons of scientific equipment, 4,000 workers, $304 million in annual spending and particles at almost a trillion electron volts? Hopefully, one of the smallest things in existence. This is what a large group of University physics students learned April 6 at Fermi National Accelerator Laboratory in Batavia, Illinois.
The facility commonly known as Fermilab is actually a multibillion dollar research complex, internationally renowned for its influential discoveries. The 6,800-acre complex is certainly not what is typically expected of a facility of this type. Approaching the headquarters are pi-shaped electrical poles that tower above the lush native grasses where a herd of buffalo roams over government-protected prairie. Here 55 species of birds reside in its woodland areas.
The power lines aren't the only giveaways: A 32-foot stainless steel obelisk leads the way to a 16-story office building that allows a view of Chicago on clear days.
Some of the top scientific minds in the world work inside this building, combining their abilities to solve questions that have puzzled scientists for decades: What is the smallest piece of matter in the universe? Why is there more matter than antimatter in the universe? Do neutrinos have mass? What is dark matter? Why does matter have mass? Are there forces and particles we have not yet discovered? How did the universe begin? What is matter, anyway?
What are they doing?
Fermilab uses highly accelerated particles in many of its experiments. These high-energy particles are obtained through a series of accelerators several miles long. The process starts with ionized hydrogen gas and a pre-acceleration energy of 75 keV. The ions then enter the Linear Accelerator. During the tour of the facility, the physics group got a chance to see its 1950s sci-fi-esque beginning. The Linear Accelerator's 500-foot-long copper tube accelerates the ions to 400 MeV using oscillating electric fields and then strips the electrons off, leaving only protons.
The protons pass through the Booster along their way to the Main Injector. The Main Injector has an elliptical circumference of about two miles. Completed in 1999, this unit accelerates the protons to 120 GeV using superconducting magnets and then sends some of them to the Antiproton Source. The protons are then smashed into a nickel target and result in antiprotons and other particles. The antiprotons, which have the same mass as protons but are negatively charged, are collected and stored in the Accumulator Ring.
The Main Injector also sends a portion of the 150 GeV protons and antiprotons into the Tevatron. The Tevatron is a ring similar to the Main Injector, although much larger, with a four-mile circumference. This structure, which is about 30 feet under ground, accelerates the protons and antiprotons to almost one teraelectron volt, 99.9999 percent of the speed of light. Because antiprotons and protons have a way of annihilating each when they come into contact, the particles are accelerated in opposite directions and far out of reach of each other.
Next the physicists and engineers do what they love best—smash these speeding particle to smithereens! In experiments located along the Tevatron ring, scientists study the interactions of certain particles and search for predicted ones.
In the Collider Detector at Fermilab (CDF), the proton and antiproton beams come together and collide at the rate of one million collisions per second, producing a mess of secondary particles. The CDF itself is three stories tall, weighs nearly 5,000 tons ,and consists of 130,000 smaller detectors that record statistics about the secondary particles, such as speed and direction.
For every year's worth of data collected by the detector, scientists are confronted with five years' worth of analyzing. The physicists determine the masses, momentums, and energies of the secondary particles in hopes of finding out what kind of events happen right at the collision.
DZero is another detector on the Tevatron. It is similar to the CDF and was originally designed to detect particles without using a magnetic field, as the CDF does. In 1995 the CDF and DZero jointly reported the discovery of the top quark, the counterpart to the bottom quark discovered at Fermilab in 1977.
The top quark is 100,000 times more massive than the up and down quarks, and theorists think it will play a key role in the solution to the different quark masses. These discoveries greatly contributed to the Standard Model, which represents our understanding of subatomic particles.
Neutrino physics is a growing part of research at Fermilab as well as the University. In 2000, scientists discovered the tau neutrino, which completed the neutrino trinity, joining muon and electron neutrinos. Physicists are very interested in neutrinos, which have a tendency to "change flavor," or switch from one type to the other, during long-distance travels. If these oscillations can be proven, it would imply that neutrinos must have mass, which makes them accountable for up to five percent of the "missing" or unseen mass of the universe.
Two new experiments now underway will expand our knowledge of matter even further. MiniBooNE (Mini Booster Neutrino Experiment), a study of neutrino oscillations over short distances, is currently under construction and is expected to begin taking data later this year.
The detector is a tank with a 12-meter diameter filled with mineral oil. The walls are lined with photomultiplier tubes to detect light that should be produced when muon neutrinos oscillate to electron neutrinos. If the results of this experiment are partially conclusive, MiniBooNE will be upgraded to BooNE with the addition of a 40-meter-diameter tank. The goal of this upgrade would be to find oscillation parameters and other relevant information.
The University is more heavily involved in the second experiment: NuMI (Neutrino at the Main Injector). This is Fermilab's source of neutrinos for the MINOS (Main Injector Neutrino Oscillation Search) experiment, which will receive the neutrinos and study the possible oscillation over a long distance.
MINOS is housed in the Soudan Underground Mine in northern Minnesota, and the University's experimental high-energy group is the largest university group involved in designing and building the huge detector. NuMI is still under construction and should begin sending the neutrino beam to Soudan by 2004.
Why are they doing it?
One may look at all these processes and wonder exactly what justifies Fermilab's $297 million annual budget. Fermilab's extensive research has long- and short-term goals.
At present, Fermilab researchers have already discovered remarkable applications. Fermilab has been using particle beams to treat cancer and has achieved a very impressive medical success rate. The laboratory has also been influential in developing technologies for accidental discoveries. One such invention in which Fermilab played a part was the World Wide Web. The Web was originally developed at CERN, the European Particle Physics Laboratory in Geneva, Switzerland, by physicists looking for an efficient way to share information. Fermilab's web site has been online since 1992, making it one of the first Internet sites. Fermilab's research has led to new ways of working with electrical currents and magnetism, such as making circuits more effective and magnets more powerful, two essential parts in the equation for making electronics faster and smaller. Alan Greenspan and other economists have also cited the work produced by this research team of 2,200 as a driving force behind the U.S. economy.
Secondly, Fermilab's experiments, both past and present, show that basic physics research not only expands our understanding of the world and the nature of the universe but also improves what we do have and creates untapped knowledge for future inventions.
When the electron was originally discovered in 1897, it was said to be "useless." Dr. Leon Lederman, 1988 Nobel Prize winner and former Fermilab director, explains, "In 1680, Isaac Newton worked on the abstract problem of gravity and changed the world. In 1820, Michael Faraday discovered a connection between the exotic phenomena of electricity and magnetism, and his discovery electrified the world."
Ever since Einstein published the famous equation E=mc2, the world has come to appreciate basic physics discoveries; the more basic the discoveries are, the more profound the consequences.
Without knowledge of electrons or Einstein's theories we would not have microwaves or chemotherapy. By harnessing the power of the atom we discovered nuclear energy. The powers of the electron are still being realized—the Information Age has been the product of that discovery. Science has only begun to tap into the quark; we can barely imagine the wonders and technology that our new enlightened future will hold.
In Depth Articles:
Enrico Fermi: The man behind the laboratory
Mind over matter: A particle physics timeline
FOR MORE INFORMATION:
www.cala.umn.edu/BuildingCALA.html
www.stevenholl.com
