Word: fusion
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Dates: during 1970-1979
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Tiny Bombs. Still, to join enough deuterium and tritium nuclei to sustain a fusion reaction requires heroic efforts. Deuterium-tritium gas mixtures must be heated to as much as 100 million degrees Celsius and be maintained at that temperature for about one second at a density of about 1014 (100 trillion) particles per cubic centimeter. Scientists have taken two different routes in their efforts to achieve these critical conditions. One is to use a "magnetic bottle" -an enclosing magnetic field-to contain the hydrogen fuel. The other is to use lasers or electron beams to make miniature hydrogen "bombs...
...thus becomes a "plasma"-a mixture of negatively charged electrons and positively charged nuclei, or ions. Because these charged particles will not generally cross magnetic lines of force, they can be confined by a powerful magnetic field. The magnetic bottle is the only known practical container in which fusion can be sustained for any significant amount of time. If a plasma were to come in contact with the walls of a reactor, it would pick up impurities, lose energy and suffer a temperature drop that would immediately halt any fusion reaction...
Ectoplasmic Bagel. The magnetic containment devices most widely used in fusion experiments are called "tokamaks." Invented by Soviet scientists in the early 1960s, tokamaks are toruses, or doughnut-shaped chambers, surrounded by huge electromagnets. Gas is fed into the chamber and heated until it becomes a plasma. Powerful fields produced by the magnets hold the plasma and keep it from touching the chamber walls. The temperature of the plasma is raised closer to fusion temperatures by passing electric currents and shooting beams of high-energy atoms through it. With these techniques, tokamaks have come the closest of any magnetic device...
...open-ended tube surrounded by magnets. Extra-powerful magnetic fields at the ends of the tube act as "mirrors," reflecting particles toward the center of the device and reducing leakage. But none of these or other exotic magnetic devices have yet simultaneously produced all three conditions necessary for controlled fusion...
Most scientists concede that this honor could well be won by the giant Tokamak Fusion Test Reactor (TFTR) now under construction at Princeton. The TFTR is scheduled to begin operation in 1981 and is expected to prove the scientific feasibility of fusion...