Toward H-Power

Science took a long step toward the time when the earth's oceans can be used as fuel. Last week, joint announcements by Britain's Atomic Energy Authority and trie U.S. Atomic Energy Commission told how both nations are coming close to taming for peaceful uses the furious energy of the hydrogen bomb.

Both Britain and the U.S. use complex machines that work in about the same way toward the same simple purpose: to heat gaseous deuterium (heavy hydrogen) as hot as possible and confine it in a small space as long as possible. When deuterium atoms get hot enough, they hit each other so hard that they "fuse," forming helium 3 (and a neutron) or tritium (and a proton), and give off energy. This process happens explosively in H-bombs, but to control the reaction, the deuterium must be confined. Since ordinary, solid walls cannot hold the gas at the necessary temperature of many million degrees, fusion reactors use walls of magnetic force. They are strong, do not cool the gas and are not damaged by it. But the machines' complexity proves that magnetic walls are hard to handle.

Three Doughnuts. Britain's ZETA (Zero-Energy Thermonuclear Assembly), which was shown last week by Sir John Cockcroft at Harwell atomic laboratory, looks like three 10-ft. doughnuts laced together like links of a chain. The central horizontal torus (scientific word for a doughnut shape) is a ring-shaped aluminum vacuum chamber with a 39-in. bore. The two vertical doughnuts linked into it are the iron cores of a transformer. When a small amount of deuterium gas is fed into the evacuated torus and a heavy electric current is shot through the transformer, an even heavier current (this is how transformers work) flows in a circle through the deuterium.

The current completely ionizes the deuterium, knocking its atoms apart into positive nuclei (deuterons) and negative electrons. When a powerful current flows through this sort of "plasma," a strange thing happens. The gas is compressed by the magnetic field that the current generates. It gathers in a ring at the center of the torus, and the current flowing through the ring heats the gas to millions of degrees.

This "pinch effect" is the most promising approach to thermonuclear power, but unfortunately the pinched current wriggles so violently that it tends to slam in millionths of a second against the walls of its container. The trick, a difficult one, is to make it stand still as long as possible and not touch the walls.

5,000,000DEG. The Harwell scientists, led by Peter Clive Thonemann, have made ZETA's pinch behave by passing a second current through coils around the torus. This current creates a second magnetic field which keeps the pinch away from the walls for as long as five one-thousandths of a second. The deuterium in it is heated to 5,000,000DEG C. (one-third of the temperature at the center of the sun), and free neutrons shoot out of the torus.

The most impressive U.S. thermonuclear work was done at Los Alamos Scientific Laboratory with a machine called Perhapsatron S-3. Its doughnut is made of glass surrounded by copper, and is about as big as a scooter tire, with its minor diameter (through the dough) about 2 in. compared to ZETA's 39 in. The temperature of its pinch is higher than ZETA's (about 6,000,000DEG C.), but the pinch lasts only a few millionths of a second, about one-thousandth as long as ZETA's. Other thermonuclear machines at Los Alamos use short, straight tubes through which heavy currents are forced to flow and pinch deuterium ions. All the machines give off abundant neutrons.

The big question is whether these neutrons really come from the fusion of deuterium into helium 3. Powerful electrical discharges can give "false neutrons." formed in other and less important ways, but Scientist Cockcroft is "90% certain" that at least some of ZETA's neutrons come from a thermonuclear reaction. Dr. Thonemann of Harwell does not want to commit himself definitely. U.S. scientists are not sure either. Dr. James Tuck, head of the Los Alamos group, wants to learn more before he makes positive statements.

The British thermonuclear scientists do not say flatly that they are ahead of their U.S. colleagues, but Dr. Thonemann, master of ZETA, points out that with a small thermonuclear doughnut it is hard to keep the pinch away from the walls for long. "You have to go fairly big," he says, "if you want to put up temperature and put up containment time too." The U.S. Atomic Energy Commission apparently agrees with this reasoning; it is building at Princeton, N.J. a very large thermonuclear device, a "Stellarator," which is scheduled to start operation in 1960.

Thorny Problems. Neither the British nor U.S. scientists claim that they have made a breakthrough that will quickly yield controlled thermonuclear power. Much higher temperatures, above 100 million degrees, will be needed before the fusion of deuterium gives off even as much energy as it consumes. All sorts of thorny practical problems will have to be solved before thermonuclear energy flows through practical wires. No one wants to predict definitely how long it will take. "It couldn't possibly be less than ten years," says Sir John Cockcroft. "It might be as long as 50. Twenty plus is about the most reasonable guess."

The cost of this effort will be high, but the stakes are even higher. Deuterium, the fuel of thermonuclear power plants, can be extracted fairly easily from any kind of water, and there is enough in five gallons of water to yield as much energy as ten tons of coal. All nations with the wit to handle the difficult thermonuclear technology will have access to virtually unlimited energy.

This file is automatically generated by a robot program, so reader's discretion is required.