RESEARCH
SHOCK WAVES. General Atomic's Dr. R. F . Scott uses shock tube to study plasmas by means of electromagnetically produced shock waves. H e has found a way to inject stream of hot gas into magnetic "bottles" a t high velocity
Fusion Research Moves Ahead General Atomic scientists contradict earlier reveal w o r k with plasmas and magnetic fields U.S. SCIENTISTS are steadily pecking away at the problems of controlled thermonuclear reactions. Several new developments came to light at the Texas Symposium on Nuclear Fusion, held in Austin, Tex. Among them: • A theory that contradicts Soviet predictions that power-producing fu sion reactors would have to be too enormous to be economical. • A magnetic field that promises to provide greater stability for containing hot, ionized gases. • A means of propelling ionized plasma into magnetic fields at very high velocities. The University of Texas and the Texas Atomic Energy Research Foun dation sponsored the two day confer ence. TAERF, made up of 11 utility companies operating in Texas, supports a four year, $10 million research pro gram on controlled fusion reactions at t h e John Jay Hopkins Laboratory of General Atomic (division of General Dynamics), San Diego, Calif. 40
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• Radiation Losses. Two Soviet scientists, B. A. Trubnikov and V. S. Kudryavtsev, presented Soviet thinking on the size of controlled thermonuclear reactors at the conference on peaceful uses of atomic energy, held in Geneva in September 1958. Tl· y said that cyclotron radiation losses from ex tremely hot plasma contained in a mag netic field would be seriously high. They concluded, therefore, that to pro duce enough energy to compensate for these losses, a fusion reactor would have to be extremely large, probably hun dreds of feet in diameter. Dr. Marshall N. Rosenbluth and Dr. William E . D r u m m o n d of General Atomic have rechecked the Soviet cal culations. Dr. Rosenbluth told the symposium that the Soviets were cor rect, as far as they went. They as sumed wrongly, however, that cyclo tron radiation is emitted randomly, that is, in all directions. The General Atomic theoretical physicist contends that this radiation isn't isotropic (emitted in all direci d , most of it is emitted
in planes perpendicular to the magnetic field. A s a result, h e says, the Soviet estimates of energy losses were exaggerated. W h a t ' s more, since this radiation is in the infrared region, much of it could b e reflected back into the reactor by aluminum or silver sheeting. This would reduce radiation losses even more. Based on his calculations, Dr. Rosenbluth believes that thermonuclear reactors could be m u c h smaller than predicted by the Soviets—on the order of feet, instead of hundreds of feet, in diameter. • Magnetic Cusp. One of the big problems with controlled thermonu clear reactions is how to contain the extremely hot, ionized plasma. It must be held long enough for enough nuclei to collide so that more energy will b e generated b y the reaction than was needed to heat the plasma to its reac tion temperature (about 100,000,000° C ) . To accomplish this, scien tists count on different configurations of magnetic fields, such as the "pinch" and the "mirror." General Atomic now finds that another magnetic configura tion, t h e "cusp," promises to b e more stable than the others. The "cusp" has long been well known in electromagnetism. Physicists at New York University and Los Alamos Scientific Laboratory have proposed it as a possible magnetic "bottle" for hot plasma. But, says Dr. D. W. Kerst, General Atomic's experiments are t h e first practical trials. Dr. Kerst, project leader in the fu sion research program, says the "cusp" holds plasma stahly for 10 to 20 micro seconds and indicates that even longer times are possible with it. One reason why t h e "cusp" works better: Its mag netic lines of force are convex to the gas, or plasma, pressure. Convex lines are basically more stable than concave lines, which other magnetic configura tions contain. • Gas Gun. Another General Atomic scientist, Dr. F . R. Scott, has come u p with a way to inject a high velocity stream of gas, such as deu terium, into magnetic "bottles." Dr. Scott's device is similar to a pinch tube, but one electrode is placed around a gas chamber. A capacitor is tied to it. Because of a vacuum in the chamber, no current flows through it. However, when gas is fed t o the chamber, large currents begin to flow. This heats the gas, which expands and moves down the tube into the magnetic "bottle" at extremely high velocities. Β
