Number 421 (Story #2), March 31, 1999 by Phillip F. Schewe and Ben Stein|
TABLETOP THERMONUCLEAR FUSION. Yet another Livermore photonuclear breakthrough was reported at the APS meeting. Todd Ditmire described an experiment in which laser pulses (35 fsec long and intensities as high as 1017 W/cm2) were absorbed by a gas jet of deuterium molecules. These molecules actually resided in clusters (average size of 5 nm) which exploded under the laser bombardment. Some of the rocketing D's fused into helium-3 nuclei plus energetic neutrons. The neutrons, showing up with a characteristic energy of 2.45 MeV, were detected (about 10,000 per laser shot) via a time-of-flight technique. Ditmire said that this new approach to promoting fusion reactions (executed with a setup that fits on a 4'x11' table) could probably not be scaled up to provide commercial power, but that it might provide a cheap source of neutrons. The whole process is highly efficient: virtually all the laser energy was converted into ion kinetic energy.