Burning Times for Hot Fusion; March 2000; Scientific American Magazine; by Ariza; 2 Page(s)

Electricity from fusion could be real in 50 years, a group of European scientists insisted in a Munich seminar last November. Moreover, they concluded, the International Thermonuclear Experiment Reactor (ITER) is still the correct next step. The conviction comes at a seemingly odd time for fusion in doughnut-shaped rings called tokamaks, a technological disappointment if ever there was one, at least from a commercial point of view. ITER, once a $10-billion collaboration begun in 1986 by the U.S., Russia, Europe and Japan, was to be the first tokamak to achieve a self-sustaining fusion burn. Skeptical of the design and concerned with the high price, the U.S. dropped out two years ago; because of its economic woes, Russia will only commit staff, and Europe and Japan still might pull back future funding.

Tokamak fusion relies on a mixture of the hydrogen isotopes, such as deuterium and tritium. Superconducting magnets confine the fuel in a torus; the fuel is then heated to 100 million degrees Celsius. The mixture becomes a plasma-a soup of free electrons and ionized atoms-and deuterium and tritium nuclei fuse, yielding energetic neutrons and alpha particles (helium atoms). The alpha particles heat the plasma; if there's enough of them, they will keep the plasma burning and the fusion going, so that the reactor generates more energy than it consumes. So far, though, no fusion reactor has even achieved breakeven.