What scientists have called "the opening shot in America's counterattack" to regain the lead in physics research was fired in Batavia, Ill., yesterday when the Fermi National Accelerator Laboratory boosted protons to an energy level higher than any previously achieved by man.

A new machine constructed at the laboratory sent protons around its four-mile circumference to an energy level of 512 billion electron-volts, about 7 billion higher than the previous record.

An electron-volt is the energy gained by an electron jolted with one volt of power. For instance, the energy of atomic particles in a fire is only a few electron-volts per particle, while the energy of particles inside the sun is a few million electron-volts.

The new machine is expected to reach a peak energy capacity of one trillion electron-volts within the next few months.

Because of its high energy output, it will be the first machine with a good chance of determining whether particles called "quarks" are in fact the final, indivisible bits of matter from which all other matter is built.

At full power, the machine will reach "beyond the area where the theorists can safely project their theories," said Leon Lederman, director of the Fermi lab. It will be possible soon to learn whether some particles are truly elementary--plain, featureless bits of matter: "whether the electron is elementary or has little people inside it," Lederman said. "Is the quark elementary , or is matter infinitely complex, just an endless regression of parts within parts within parts?"

To answer such questions, it is necessary to have machines of enormous energy. Such immense energies as 500 billion electron-volts are required to peer into the heart of matter, just as great magnifications are required for microscopes and telescopes.

But subatomic particles do not naturally reach energies near 1 trillion electron-volts. Such energies have been achieved only during the creation of the universe and the subsequent births of stars, physicists say.

So physicists must build massive particle-accelerating machines to duplicate the high-energy conditions under which matter was created, and try to see what matter is composed of.

The Fermi accelerator, about 40 miles west of Chicago, is one of the largest machines ever built. Nicknamed Tevatron, it is constructed in a circular tunnel four miles in circumference and buried 20 feet beneath the Illinois prairie.

The accelerator is the first of a two-step program to leapfrog Western European physics machines, generally acknowledged as the world's most advanced. In 1985, the new Fermi machine is to double its power to 2 trillion electron-volts.

For about four years, Western Europe has led the world in high-energy physics research after the United States dominated the field for several decades. Europeans beat several competitors in building an accelerating machine that allowed discovery of several new particles responsible for carrying one of the universe's fundamental forces.

Even as the United States tries to regain the lead in physics, the Europeans and Soviets have planned to build even larger accelerators.

Accelerators impart energy to particles by speeding them up, using 20-ton magnets to give them a push along a steel tube that, at the Fermi lab, measures four miles long by four inches in diameter.

At peak energy, the particles are crashed into a target, such as an aluminum rod or an opposing stream of particles.

In the collision, the speeding protons and target atoms are destroyed, transformed into a smear of pure energy. The energy then quickly congeals again into a new stream of particles. The number and kind of new particles, and the way they fly apart, provide a map by which physicists can read the constitution of matter.

Lederman compared such particle collisions to firing two garbage cans at one another. The idea is to find out what they contain. After the garbage cans collide, physicists try to reconstruct, from photographs of the flying debris, the contents and their precise arrangement within the cans.

U.S. domination of high-energy physics ended when large budgets for such projects began to shrink. The Fermi lab, for example, was forced to turn off its accelerator for 27 weeks a year for several years because of lack of funds.

The Europeans, using twice the staff and twice the operating budget, during that time built what has been the world's leading physics research machine. It is located near Geneva and is called the European Center for Nuclear Research (CERN in its French acronym).

The experiments ready to be carried out at Fermi and CERN are expected to end an era in physics research.

At the turn of the 20th century, physicists discovered the structure of the atom: a hard core surrounded by buzzing electrons. The next research era opened the nucleus and discovered protons, neutrons, an array of other short-lived particles and the forces that held the bundle together at the nucleus.

The most recent era went one level deeper, seeking particles that made up the protons, neutrons and other particles within the atomic nucleus. Americans Murray Gell-Mann, Richard Feynmann and others worked out a scheme by which all matter in the universe could be built up essentially from three particles, three "quarks," as Gell-Mann whimsically named them after a line in James Joyce's novel, "Finnegans Wake."

More recently, experiments have shown that more quarks must exist to explain the myriad forms taken by matter.

Lederman said physicists are unhappy with their current theoretical models because they are "all too complicated."

Physicists had hoped to see one, two or three truly fundamental particles at the heart of all matter, with no complicating properties. In the current best model of the universe, 36 types of quarks are necessary.

"Thirty-six quarks? Is that what God wanted us to find at the bottom of all matter?" Lederman asked.

So he and other physicists say they hope to break through the current barrier of complexity with this new machine and several still greater machines planned for the next decade.

The Americans hope to build rather quickly a series of machines culminating in one great national accelerator 100 times more powerful than anything in existence and having a circumference of 100 miles. It would cost between $1 billion and $2 billion.