Getting Closer

"It sounds like a lightning bolt is going off in the next room," says one worker. The building shakes, but researchers at Washington's Naval Research Laboratory hardly look up. They know it's only dynamic Alan Kolb, 30, at work on his thermonuclear experiment.

Last week in Upsala, Sweden, Kolb reported his preliminary results to an international conference of physicists. The data indicated that his project has made a significant advance toward the achievement of the first controlled fusion reaction, an objective that could give the human race a source of energy that would last for millions of years: one small bucket of water holds enough heavy hydrogen to make fuel equivalent to 300 gallons of gasoline.

Water for Fuel. The first step toward creating a controlled fusion reaction is to heat up deuterium gas until the nucleus (one proton and one neutron) of each atom is separated from the electron that ordinarily orbits around it (deuterium is the hydrogen isotope in heavy water, D2O). If the particles are made hot enough, the deuterium nuclei will collide with ample force to "fuse" together, forming helium 3 and giving off a neutron. When that happens, part of their mass is converted into energy--the energy of the hydrogen bomb, the stars and the sun.

The temperature required for a sustained reaction is, at a minimum, 50 million degrees. No conventional container could withstand such a temperature, so physicists surround the "plasma" of deuterium with a magnetic field whose lines of force are powerful enough to hold it. Then an enormous bolt of electricity is shot into the system to make the plasma particles move rapidly, thereby supplying the necessary heat.

Trouble is that when the big bolt strikes, the plasma writhes and twists, often breaks out of the magnetic field and dissipates its heat into the walls of whatever sort of outer container is being used.

Neutron Shower. In Kolb's experiment, the deuterium plasma is held in a quartz tube about a foot long. At each end the magnetic field is given added strength to form a magnetic "mirror," which reflects back the charged particles as they try to escape, thus sealing the gas in a magnetic bottle. A bank of 99 condensers, kept in the basement since condensers sometimes blow up, sends a jolt of 4,000,000 amperes thundering through the coil, heating the gas up to around 20 million degrees. Dr. Kolb reported that his machine had confined plasma and kept it stable at this temperature for twelve microseconds. During this period, bursts of neutrons poured out of the device. "This agrees with theoretical calculations for a fusion reaction," said Kolb cautiously.

Neither Kolb nor anyone else is claiming that a fusion reaction was definitely achieved. The British, who thought they had achieved it with their Zeta a year ago, later admitted that the neutrons produced came not from fusion but from unintended collisions of high-energy particles. Furthermore, it would take far higher temperatures before the deuterium fusion would produce more energy than it absorbed. Explained NRL Research Director Robert M. Page: "We have to go farther to get a true fusion reaction and farther still to prove it." Sustaining a fusion reaction, he explained, is like lighting a piece of paper with a match. First the paper turns brown, then it smokes, then it bursts into flame. "We think we have reached the stage where the deuterium is beginning to show a little brown." What Kolb and the Naval Research Laboratory need now is a bank of condensers ten times as powerful, i.e., a bigger match.

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