Bigger Mini-Bangs for the Buck

By Frederic Golden

A powerful new machine accelerates U.S. high-energy physics

As they watched a green line edge across a video screen, the excitement mounted. "It's going!" exclaimed one of the exultant scientists. "Keep going! Keep going!" shouted another. The control room soon erupted into a chorus of unrestrained cheers. Bottles of champagne were broken out, and toasts resounded.

That tumultuous scene last week, reminiscent of a locker-room victory celebration, marked a more esoteric kind of triumph. When the green line made its telltale movement at the Fermi National Accelerator Laboratory, the sprawling high-energy physics research center outside Chicago, it signified a major scientific achievement. At that instant, Fermilab's newly rebuilt accelerator (physicists prefer that term to atom smasher) climbed to 512 billion electron volts (GeV),* the highest energy level ever reached by the powerful machines used by physicists to study the fundamental secrets of matter.

The record, to be sure, was only a minor increase over Fermilab's existing capability. In 1976, five years after its completion, the accelerator hit 500 GeV and has been operating close to that level ever since. But the jubilant scientists nonetheless had reason to celebrate. The test meant that years of work had finally paid off and that the $130 million set aside to make the machine the most complex accelerator ever built had really been well spent. In the months ahead, it will gradually be boosted to 800 GeV and perhaps by next year to a trillion electron volts (TeV). At full operating power, the device will not only live up to its name, Tevatron (from the Greek teras, or monster, a scientific symbol for a trillion), but will also put the U.S. back in the forefront of high-energy physics. Says Fermilab Director Leon Lederman: "The Tevatron is a leapfrog. If we hadn't done it, our program would have been seriously compromised."

The ancient Greeks needed only their powerful intellects and imaginations to postulate atoms as the basic building blocks of matter. Today, more than ever before, such exploration requires complicated machines like Fermilab's Tevatron. By pummeling the nucleus, the atom's central mass, with protons or other subatomic particles, physicists can literally tear apart the fabric of matter, somewhat like peeling layers from an onion. Every peel, however, requires increasingly powerful and costlier machines. As Stanford Physicist Wolfgang Panofsky notes, "The smaller the objects, the bigger the microscope we must use to see them."

The findings at the other end of those searching instruments have excited the entire scientific world. In the past four years, Fermilab's major overseas rivals, notably CERN (the European Organization for Nuclear Research), located outside Geneva, have discovered a group of new particles that helps confirm what physicists call the standard model. This divides matter into two basic types of particles: quarks, which are the building blocks of protons, neutrons and other "heavy" components of the atomic nucleus; and leptons, exemplified by "light" particles like the electron.

The standard model also postulates that the universe is controlled by four basic forces: gravity, the glue that holds the cosmos together; electromagnetism, which keeps electrons from breaking away from the rest of the atom; the strong force, which holds together the atomic nucleus; and the weak force, which controls the gradual disintegration of some nuclei, the process at work in radioactivity.

Einstein spent the last years of his life trying to show that the gravitational and electromagnetic forces were different aspects of the same phenomenon. Although he failed in his attempt at unification, theoretical physicists have now begun to glimpse an underlying oneness in the four basic forces. With their customary whimsy, they call these theories GUTs (for Grand Unified Theories). Central to this framework is the existence of new particles, tiny fragments of matter (or energy, since the two are interchangeable) less than a trillionth the size of a bacterium, itself only about a ten-thousandth of an inch long, that transmit these forces.

Physicists have long known that the photon, or light particle, was the carrier of electromagnetism. In 1979 in Hamburg, West Germany, they discovered the gluon, which conveys the strong force. This year CERN scored its crowning achievement by confirming the existence of three particles, the W+, W-and ZDEG, known collectively as intermediate vector bosons. They were predicted to be the agency of the weak force. That feat was a coup for a resurgent European physics community struggling to get back on its feet after World War II. It also irritated American scientists, who had regarded themselves as the world champions in high-energy physics. Ironically, the leader of the successful CERN experiment, who may win a Nobel Prize, was Italian Physicist Carlo Rubbia, a faculty member at Harvard. He had originally proposed it to Fermilab, which decided to concentrate on the new machine instead.

Tevatron should help right the transatlantic balance. Like Fermilab's existing accelerator, in whose tunnel it was built, the new machine is a giant four-mile-long circular particle race track, capable of whipping protons to within a shade of 186,000 miles per sec., the speed of light. When these high-velocity particles strike a target, for example, a metal bar, they shatter its component atoms, resulting in a burst of subatomic debris. Some of these particles are so ephemeral that they survive for only minute fractions of a second; from the trail they leave in detection devices, physicists are able to spot a single fragment among the millions that may have been created.

As physicists try to send more protons racing around the track at higher and higher speeds, increasing the power of these little bullets becomes considerably more difficult. They absorb more energy, become more massive, and the number of electrical pulses required to accelerate the protons rises sharply. It also takes increasingly powerful magnets to keep the speeding protons from flying off their curving pathway. Even though Fermilab operated only six months last year, its electric bill ran to $12 million.

The Tevatron should reduce those costs by half. It achieves that by a low-temperature phenomenon called superconductivity. At present, Fermilab's protons are guided by conventional electromagnets similar to those used in electrical motors. But these are already working at peak load. If any more electricity were pumped through them, their copper coils would melt from the high heat. For the Tevatron, a second proton race track has been added just below the existing one. Here the protons are guided by 1,000 custom-designed superconducting magnets (cost: $40,000 apiece), with coils of an exotic alloy of niobium and titanium. Cooled to -450DEG F by a liquid-helium refrigeration system, such materials lose all resistance to electricity and sharply reduce power demands. To reach its normal operating level of 400 GeV, the old machine required 60 megawatts of electricity; the new machine should consume only 20 megawatts, even when operating at a full 1,000 GeV.

Fermilab scientists, however, still have their work cut out for them. The accelerator's complex power system is only partly installed. The accelerator must also be fine-tuned so that none of the trillions of protons whirling around the track 50,000 times a second crash into the surrounding magnets, impairing their operation. But once those obstacles are overcome, Lederman and his Fermilab colleagues expect great things from their machine. "We're opening a new domain," he notes, and there are sure to be "uncovered surprises."

One object that Tevatron will seek to snare is an elusive new particle, akin to the Ws and ZDEGs, called the Higgs (after University of Edinburgh Theorist Peter Higgs). Still others that will be hunted bear such playful nomenclature as the wino, gluino and squark. All are possible inhabitants of Tevatron's high-energy world. This fiery cauldron is a replication in miniature of the earliest universe, just moments after the Big Bang, the cataclysmic explosion in which, most physicists now agree, the cosmos was born. Says CERN'S director-general, Herwig Schopper: "We are creating particles through mini Big Bangs."

Initially cool to basic research, the Reagan Administration now appears eager to maintain American leadership in high-energy physics. Says Presidential Science Adviser George Keyworth II: "Elementary particle physics is a place where truly creative genius can show its mettle." A physicist, Keyworth likens the building of big new accelerators to the Apollo program: "Apollo wasn't just learning about the geology of the moon, it was also about leading the U.S. into an era of high technology."

In the coming weeks, the Administration will have to decide on new directions in particle physics. One option, opposed by Keyworth, is to continue work on another superconducting accelerator at Fermilab's East Coast rival, Brookhaven National Laboratory on New York's Long Island, which has been seriously delayed by technical problems. Keyworth would prefer to put most of the country's limited resources for high-energy physics into a gargantuan new accelerator. It could be as much as 100 miles in circumference, cost $1.5 billion, and reach energy levels 20 times those of Tevatron. Because it was first proposed for a site in the Southwest, physicists nicknamed the project the Desertron. Says Fermilab's Lederman, another Desertron enthusiast: "This is the cutting edge of basic research and vital to maintaining U.S. creativity and ingenuity."

Even if it is built, the Desertron will not stand alone in the new era of mega-accelerators. At CERN, the West Europeans have just broken ground for a giant accelerator known as LEP (for Large Electron-Positron storage ring). Scheduled for completion in the late 1980s, it will rifle electrons and their antimatter opposites, positrons, on collision courses along a 17-mile nuclear race track extending from the present CERN lab in suburban Geneva to the base of the nearby Jura Mountains in France. The Soviets are also laying ambitious plans. At Serpukhov, 60 miles south of Moscow, they have started work on a superconducting accelerator designed to reach three times Tevatron's energy levels.

Such friendly rivalry, says CERN's Rubbia, "keeps things bubbling. That's healthy for physics, and I hope things stay that way." But Physicist Panofsky, retiring director of the Stanford Linear Accelerator Center (SLAC) in Palo Alto, Calif., the other major high-energy research facility in the U.S., takes a longer view. Even though SLAC has just got a $112 million congressional go-ahead to upgrade its machine, which uses electrons rather than protons as battering rams, Panofsky believes that such projects will become so expensive in the next 20 or 30 years that no single nation will be able to afford them. Says he: "Eventually, the next steps will have to be taken jointly, internationally."

--By Frederic Golden. Reported by J. Madeleine Nash/Chicago

* G, the symbol for a billion, stands for giga, from the Greek for giant.

With reporting by J. MADELEINE NASH This file is automatically generated by a robot program, so viewer discretion is required.