Science: Cyclotron Man

Four years ago a promising young physicist from the University of California, Ernest Orlando Lawrence, left his sunny campus and the ramshackle old building in which he was working, traveled eastward across the U. S. and across the Atlantic to attend a European scientific conference in Brussels. He was the only U. S. scientist invited. He had invented and was already making formidable use of a curious and powerful atomic weapon—a “cyclotron” that imparted great speeds to projectiles for smashing atoms by whirling them around in a strong magnetic field.

In Brussels was Britain’s gruff, burly Lord Ernest Rutherford, great formulator of the atom’s electrical structure, revered director of Cambridge University’s Cavendish Laboratory. Also on hand was one of Rutherford’s imaginative young workers, John Douglas Cockroft, who was at that time splitting lithium atoms by hurling protons at them. Cockroft energized his protons with high voltages obtained by transformers, rectifiers and condensers.

Cockroft realized the greater potentialities of the Lawrence machine, had tried to persuade Lord Rutherford to acquire one. Rutherford was unimpressed. In Brussels, Cockroft asked Lawrence to give the old physicist a sales talk. Lawrence assented. Lord Rutherford declared it to be one of his principles that the equipment used at Cavendish should be developed there. Young Dr. Lawrence made a quick-witted thrust: “Sir, you use spectrometers in the laboratory every day, but they weren’t invented there, were they?”

Two years ago Cambridge announced that it would build an atom-smasher of the Lawrence type. The Cavendish workers now expect their machine to be running in about a month. But Lord Rutherford will never see it start. He died last week, aged 66, after failing to rally from an abdominal operation. His passing evoked expressions of grief and tribute from all over the scientific world. Said 80-year-old Sir J. J. Thomson, famed discoverer of the electron, who once was Rutherford’s teacher: ”His work was so great that it cannot be compassed in a few words. His death is one of the greatest losses ever to occur to British science.”

Ernest Rutherford was one of the old pioneers in atomic physics and Ernest Orlando Lawrence is one of the new. Last week Lawrence was again traveling eastward, bound for Rochester, N. Y. where the National Academy of Sciences meets this week. Not only as the originator of the cyclotron but as the foremost U. S. destroyer and creator of atoms, the No. 1 U. S. investigator of artificial radioactivity and the headmaster of what is in effect a school for atomic physicists, he was to receive the Comstock Prize ($2,500 and a certificate). With a membership limited to 300, the National Academy is the lordliest body of scholars in the country and the Comstock Prize, its highest honor, is awarded only once every five years. In many quarters it is regarded as the highest U. S. scientific honor.

Atom Anatomy. The largest atom is only .00000001 inch in diameter, and many of the most important atoms handled by physicists are considerably smaller. An ancient Greek, Democritus, coined the word “atom” which means indivisible. For thousands of years this was a perfectly good name but for the past two decades, since the first atoms were sundered, it has been archaic.

An atom, consists of bundles of negative and positive electricity (electrons and protons) and particles without electric charge called neutrons.* Practically all the mass of an atom is concentrated in the nucleus, which is positively charged. In a stable atom the positive charge on the nucleus balances the negative electronic field outside. The lightest atom, hydrogen, has one nuclear proton and one electron spinning around it. The heaviest, uranium, has 92 protons and 146 neutrons in the nucleus, with a cohort of 92 electrons outside.

Splitting the atom means splitting the nucleus. Physicists want to do that for the same reason that every anatomist since Vesalius has wanted to cut up human bodies—to find out what is inside and how it works, about which they still have plenty to learn.

To smash atoms requires: 1) a projectile of the same size range as the atom; 2) a means of imparting high speed to the projectile; 3) a target containing the atoms to be smashed (a platinum screen, a tungsten wire, a pinch of phosphorus) which can be placed in the path of the bullets; 4) a means of identifying the wreckage, so that the investigator may find out what has happened. A common atomic projectile is the nucleus of hydrogen, the proton. Protons are prepared by stripping the electrons from ordinary hydrogen gas by means of an ionizing electrical current.

These ionized particles are allowed to flow into an atom-smashing machine, of one kind or another, in which electrical impulses pick them up and hurl them at a target. A few protons score hits, splitting a nucleus into two or more fragments. The projectile itself may combine with a fragment or fragments to form a new substance. Or it may lodge in the nucleus, creating an overweight, unstable body which begins to give off particles and gamma rays. This is called artificial radioactivity.

Best device for studying the debris is the “cloud chamber” which won a Nobel Prize for its inventor, C. T. R. Wilson of England. If this is placed next to the target, some fragments of the disintegrated atoms fly into it. The chamber contains water vapor which condenses on the trail of the fragments as droplets of fog which can be photographed. From the thickness of the fog path and its curvature in a magnetic field, much can be told about the mass and speed of the fragments and their electric charges.

In the pioneer days of atom-smashing, projectiles energized by Nature were used: the particles which spontaneously fly out of radioactive substances (radium, polonium, thorium, et al.) at enormous speed. This was the method which Lord Rutherford used for the first demonstrable nuclear disintegrations in 1919. Physicists, however, are as firmly convinced as militarists of the virtues of mechanization. Dr. Lawrence calculates that his cyclotron, operating at 5,500,000 volts, produces as many particles as would emanate from two pounds of radium—which is more radium than exists in the world.

Machines. Atom-smashing machines, most spectacular exhibits of laboratory science, have one feature in common: they must be huge in order to build up and handle the tremendous particle energies which they require for their work. In general they are of three kinds. The first, developed both in England and the U. S.., builds up high voltages by means of transformers and condensers. The second stores static electricity on balloon-sized electrodes until the potential is such that a mighty flow of direct current crosses the gap. For technical reasons, notably the difficulty of constructing a discharge tube which will handle the flow of high-voltage particles, the practical upper limit for these types is about 2,000,000 electron-volts. Massachusetts Institute of Technology, which had a giant electrostatic generator shooting 7,000,000-volt sparks from electrode to electrode four years ago, has not yet put it to work smashing atoms because of the discharge tube problem.

The cyclotron of Ernest Orlando Lawrence neatly finesses such troubles by making a comparatively small voltage act on a particle repeatedly until it attains a speed corresponding to extremely high voltage, thus dispensing with a discharge tube altogether. Most conspicuous feature of the apparatus is an 85-ton electro-magnet whose poles face each other vertically across an 8-in. gap. In the gap is placed a shallow cylindrical tank, pumped out to a high vacuum so that particles inside may move freely without interference from air molecules. Ions such as deuterons (nuclei of heavy hydrogen) are fed in at the centre.

By means of a radio-frequency oscillator a rapidly alternating potential of 50,000 volts is maintained across the tank. Under this influence the deuterons in the centre start to move outward. The effect of the big magnet is to pull them in circles. Just as they complete a half-circle the voltage is reversed, so that they get a kick of 50,000 volts to boost them around the other side of the circle at higher speed. After another half-circle the reversed voltage hits them again, and so on. The deuterons go spiraling outward, faster and faster, toward the rim of the tank. After being kicked 100 times by 50,000 volts, they attain speeds of 5,000,000 electron-volts. As they approach the rim of the tank, they are guided by a deflecting plate through a window and thence against any target the researchers choose.

The newest set-up at Berkeley, which has been operating for two months and which Dr. Lawrence described this week in Rochester, has a vacuum tank 37 in. across, hurls deuterons at 7,800,000 volts. If these are directed into a beryllium target, the beryllium belches out at least one trillion neutrons per second, possibly ten trillion.

The “Breaks.” Lawrence conceived the basic idea of the cyclotron in 1929 when he read a paper by an obscure German on the behavior of ions in a magnetic field. Next year he and three co-workers —Niels Edlefsen, M. Stanley Livingston and David Sloan—built the first cyclotron with a tank six inches across and a small magnet. It worked, but Lawrence pined for a bigger magnet.

When Dr. Leonard Fuller, head of electrical engineering at the university, heard of this he asked Lawrence how an 85-ton magnet would suit him. Lawrence gasped. Dr. Fuller also happened to be vice-president of Federal Telegraph Co., which had built four 85-ton magnets for round-the-world radio transmission during the War. Peace came before this particular magnet could be shipped to China and ever since it had lain idle at Palo Alto. Dr. Fuller and Dr. Lawrence jumped into an automobile and roared down to Palo Alto. Soon the big magnet was installed at Berkeley.

Lawrence regards this gift as one of his two luckiest ‘”breaks.” The other was the fact that University of California’s Gilbert Lewis was making heavy water, containing heavy hydrogen, soon after its discovery by Columbia’s Urey. Lewis let Lawrence have generous samples and Lawrence was the first man to use the heavy hydrogen nuclei—deuterons—as atomic projectiles. They are more effective than protons, easier to handle than alpha particles.

Mass Attack. The volume of results piled up at Berkeley is impressive. Much of it consists of data on hundreds of radioactive elements created by bombarding almost all the 92 standard elements—what projectile was used, what energy, how quickly the artificial radiation subsides, what it consisted of. In altering atomic structures, Dr. Lawrence has even created a few atoms of gold, thus technically at least realizing the old dream of the alchemists. But the raw material for this transmutation was platinum, and the few gold atoms were not worth a fraction of the energy used in manufacturing them, although the electric current necessary to run the cyclotron for an hour costs only $1.50. “Anyway,” as Lawrence remarks with a grin, “the information we are getting is worth more than gold.”

The Berkeley researchers have also created a small trace of Radium E—not a temporarily radioactive substance but actual radium. The Lawrence cyclotron technique has in the past five years come to be recognized as the most efficient atom-smashing device in the world. Eleven cyclotrons are either in operation or being built in the U. S., one in Canada, eleven in Europe and the Orient. And many of these projects are directed or staffed by men who learned their cyclotron technique as research fellows under Ernest Lawrence at Berkeley.

Radiations & Flesh. To guard against injury from radiations in the vicinity of the cyclotron, Dr. Lawrence’s crew carry small electroscopes in their pockets which they discharge into a meter at the end of the working day to see how much radiation they have been exposed to. Since neutrons cannot be controlled by magnetic fields and slide easily through almost all substances except those rich in hydrogen, Dr. Lawrence moved the control panel 60 ft. away from the apparatus and surrounded the machine with tanks of water six feet high, three feet thick (every water molecule contains two neutron-braking hydrogen atoms). No one is allowed inside this barrier when the cyclotron is running. Experiments on rats exposed to heavy neutron bombardment revealed a destructive effect on their white blood cells, and if exposed long the rats died.

But neutron rays, and also the emanations from artificially radioactive substances, may turn out to be beneficial instead of harmful if artfully managed. Lately the biological and medicinal possibilities of cyclotron products have loomed increasingly large on the scientific horizon. In a malodorous room near the cyclotron chamber at Berkeley are stacks of cages containing white rats, labeled by splotches of blue, yellow or pink paint on their backs. These animals have been made cancerous by implantations of cancerous tissue. Preliminary experiments tend to show that neutron bombardments have a selective effect on cancer cells five times as strong as that of X-rays.

When Lawrence made sodium radioactive, the prospect arose of administering salt containing radio-sodium, as a saline solution to be swallowed or injected. The radiation dwindles by half every 15 hours and practically dies out in a few days. This was tried on some patients at the University of California hospital, and although the results were inconclusive, Lawrence feels that no such promising line of investigation should be dropped until it has been followed out further. His brother, Dr. John Lawrence of Yale Medical School, is helping him with the biological research and writing reports for medical publications. Another possibility is to trace the metabolism of iron and calcium in the body by means of radio-iron and radio-calcium.

During the past month workmen have been laying the concrete floor of a big new laboratory next to the old building. In this a tremendous cyclotron with a 220-ton magnet will be installed, hurling deuterons at 12,000,000 to 20,000,000 volts, alpha particles at 24,000,000 to 40,000,000. When completed the new building will contain biochemical laboratories and a clinic. San Francisco’s late William Henry Crocker gave $75,000 for this project, the Chemical Foundation $68,000, Dr. Lawrence estimates that he needs about $35,000 more. Designer of the new equipment is quiet, able Dr. Donald Cooksey, assistant director of the laboratory for the past three years.

Jovial Captain. Ernest Orlando Lawrence has an ideal temperament for a man who, in such a position, must be an educator and organizer as well as a crack physicist. He is jovial and easy-going but knows how to handle men and get things done. His grandfather was an immigrant from Norway, his father a schoolteacher. Born in South Dakota 36 years ago, young Ernest was a boyhood friend of Merle Anthony Tuve, now a brilliant physicist of the Carnegie Institution of Washington. One summer he clerked at night in a hotel, another summer he sold aluminum ware in the farming region, obtained a brand-new Ford by a series of progressive trades starting with a very old Ford. He went to the University of South Dakota, did graduate work at Minnesota and University of Chicago, became an assistant professor at Yale, went to California in 1928. He is married, has two children. He plays a bang-up game of tennis, not hesitating to take on a onetime Harvard tennis captain. He enjoys good food and drink and his favorite San Francisco restaurant is Pierre’s. Last commencement he received kudos from three institutions—Stevens Institute of Technology, Princeton, Yale.

*Only the hydrogen atom contains no neutrons. ,