Giant Machines, Minute Particles

IMAGINE crossing the border between France and Switzerland thousands of times in a few seconds! ‘Impossible,’ you may say. Yet, a new strain of “borderers” are doing just that by the billion. They are minute particles hurtling along inside a giant metal ring deep in the ground at a European laboratory not far from the international airport of Geneva, Switzerland. There, huge machines called particle accelerators are helping physicists in a field of research that has long intrigued man: the secrets of matter and the laws governing the universe.

Peering Into the Infinitesimal

For thousands of years, man has dreamed of discovering the basic components of matter. At the beginning of the 20th century, scientists discovered that the atom, once thought to be the smallest fragment of matter and therefore indivisible, is made up of electrons revolving around a nucleus. It was later found that the division can go further, and now one theory is that all matter in the universe is made up of only three basic building blocks: electrons and two types of quarks, in a void.

When archaeologists discover an ancient wall, they analyze not only the bricks but also the cement used to hold them together. Similarly, modern physicists analyze the forces acting between particles. Researchers explain that two particles can be linked by exchanging a third one, somewhat in the way a ball is exchanged between two players. And just as different types of balls are used in different games, such as football, basketball, and baseball, each force, in the same way, has its own carrier-particle (or set of carriers). A study of these two types of particles (bricks and cement, players and balls) requires the use of accelerators.

Without accelerators, modern physicists would be as helpless as botanists without magnifying glasses or astronomers without telescopes. Facilities grouping several interconnected accelerators are located at CERN (European Laboratory for Particle Physics), spanning the Franco-Swiss border. Maybe we will better understand what goes on inside one of these machines if we make ourselves one million billion times smaller! Now we can follow our most unusual guide.

Journey in the Core of an Accelerator

Hello! I’m just one of the billions of protons accompanying you on your journey in the SPS (Super Proton Synchroton), CERN’s largest accelerator at present. Please try to keep up, for we will be traveling over a million kilometers (620,000 mi) in less than five seconds!

Before entering the SPS proper, we must undergo preliminary acceleration in smaller machines, in order to reach over 99 percent of the speed of light in a vacuum (300,000 kilometers [186,000 mi] per second), a speed that we cannot exceed. The SPS will raise our speed by only 0.4 percent. On the other hand, our mass will greatly increase, resulting in an energy jump from 10 GeV to 400 GeV,a and that is the result the physicists are after. So the SPS is not an accelerator in the literal sense of the term but is more like a sling whirled around at a constant speed but whose stones get heavier as they move.

We have now entered the SPS beam pipe. The entire ring, nearly seven kilometers (4.3 mi) in circumference, is housed in an underground tunnel several meters wide, where technicians can move around on bicycles when the accelerator is not in operation.

As soon as we enter the tube, we are taken in hand by 744 bending magnets. These powerful electromagnets keep us on an almost circular path. Otherwise, we would fly straight into the thick walls that absorb the dangerous radiation we give off. Since we tend to spread, we must be squeezed into a dense, narrow beam by another system of 216 focusing magnets. These could be compared to lighthouse lenses that concentrate light into a far-reaching, narrow beam.

To make our journey possible, a very high vacuum has been produced in the tube, eliminating most of the particles we would otherwise have collided with. Each time around, we receive an additional supply of energy when speeding through 20-meter-long (66 ft) radio-frequency cavities in a long straight section. The electromagnetic wave generated there imparts some of its energy to us, rather like an incoming ocean wave imparts speed to the surfer riding it.

It will now take us just over half a second to leave the accelerator in bundles of ten thousand billion. Deviated from our trajectory, we will be bombarding a target that may be a metal plate, a gas, or a liquid, depending upon the type of experiment. A portion of the energy released in the collision between protons and target particles will be converted, generally for a fleeting instant, into matter. This is just about the opposite of what happens in a nuclear reactor, where matter is converted into energy. Powerful computers linked to complex detectors then analyze particles produced in the collision.

The time has come for me to say good-bye. But if you have a few minutes to spare, there is an even more exciting experiment in store for you.

Colliding-Beam Machines

The protons that just exited have now smashed against a stationary target. However, much of their energy was wasted, being transferred to the target particles that recoil when hit. That is why 400 GeV protons smashing into other protons of stationary targets release only 28 GeV for producing new particles.

Researchers investigated the problem. In order to increase available useful energy, they came up with the idea of colliding beams. In the SPS, a beam of antiprotons (particles with the same mass as protons but with opposite electrical charges) is brought into head-on collision with a contrarotating beam of protons. When a proton and an antiproton of 270 GeV collide, practically the entire 540 GeV of energy becomes available for producing much heavier particles.

Having mastered problems pertaining to the making, accumulating, and accelerating of antiprotons, in 1983 the CERN physicists were able to provide evidence of the existence of very unstable particles called W and Z bosons. Like most of the particles generated in these accelerators, these bosons do not live long​—less than a trillionth of a trillionth of a second—​before they dissolve into energy or transform into other particles. One hundred times heavier than protons, Z bosons are the most massive particles so far discovered.

Ever Larger Machines

The hunt for more massive new particles is on the world over, especially for force carriers (the playing balls we mentioned at the start of the article). Consequently, better, ever more powerful machines are required. So in 1983, construction of a new ring got underway at CERN, near Geneva. They call it LEP (Large Electron-Positron [Collider]), a machine 27 kilometers (17 mi) in circumference, designed for accelerating electrons and positrons (antimatter counterparts of electrons). These new particle “cannonballs” should provide physicists with a new tool, a finer lancet as it were, for dissecting matter.

‘But what’s the use of all these machines?’ you may ask. True, apart from a few small accelerators used in hospitals to produce particles for destroying cancerous cells or as radioactive tracers, the technical spinoffs seem limited. However, physicists are still desirous of finding a better answer to the question: What is matter? So no doubt they will continue peering into the world of the infinitesimal, paradoxically by means of ever-larger giant accelerators.

[Footnotes]

[Box on page 25]

What Are They?

Electrons: Particles with a negative electric charge equal to that of the proton and a mass nearly 2,000 times less. An electron moves about the nucleus of the atom, with the number of electrons matching the number of protons.

Protons: Particles with a positive electric charge equal to that of the electron. A constituent of the nucleus of every atom. The nucleus of hydrogen has one proton.

Neutrons: Particles with nearly the same mass as the proton but with no electrical charge. The other constituent of the nucleus of all atoms except those of hydrogen.

Quarks: Particles believed to be the basic constituents of protons and neutrons. Quarks do not exist singly but always in combination with other quarks. Each has an electric charge, either one third or two thirds that of the electric charge of the electron.

Bosons: Particles that transmit forces between other subatomic particles. A boson that leaves one particle is absorbed by another.

Energy Transforms Into Matter

Speed and Energy: A tennis ball falling on your foot will not injure you. But if it comes fast and hits you on the nose, it could hurt you badly. Why? Because the faster the ball moves, the more energy it carries, and this energy is released upon impact. Therein lies the main purpose of an accelerator: to impart high energy to particles by accelerating them to high speeds.

Concentrated Energy Turns Into Matter: Transformation of energy into matter is not a question of quantity but of concentration. If you have a sufficient number of high-energy, fast-moving particles concentrated into a small volume, they can produce new particles (or matter) by colliding with some object or with each other.

Matter, Yes, But in Minute Quantities: Energy-voracious accelerators do not produce much matter. According to an official CERN publication, “no more than a milligram [0.000035 oz] of matter has been produced in 25 years of experiments.”

[Box/​Picture on page 26]

Recipe for Making a Cow

“Cows are not complicated to make. You just need a large amount of basic constituents​—u and d quarks and electrons. First of all, make your protons. You will need two u quarks and one d quark; then make some neutrons, using one u quark and two d quarks. You will now compose your atoms. For a cow, you will require mainly carbon, oxygen, hydrogen, and nitrogen atoms . . . The recipe for a hydrogen atom is quite straightforward: one proton with one electron circulating around it. Carbon is more complicated . . .

“Now the atoms must be assembled into molecules. Water is easy to make. Mix one oxygen and two hydrogen atoms. But for other molecules, hundreds or even thousands of atoms are required. Last of all, use these atoms to build a few tens of billions of living cells, and carefully assemble them into a cow.

“This is the recipe CERN supplies. It is strictly accurate if you take into consideration the time factor and the mysterious blueprint design that succeeded in producing a cow.”​—L’Express, French weekly magazine.

But who could have drawn up such a “mysterious blueprint”? Only a supremely intelligent Being, the One the Bible identifies as the Creator, Jehovah God.​—Psalm 104:24.

[Diagram/​Pictures on page 24]

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CERN photos, Geneva