United States Air Force trying to develop Antimatter Weapons

The most powerful potential energy source presently thought to be available to humanity, antimatter is a term normally heard in science-fiction films and TV shows, whose heroes fly "antimatter-powered spaceships" and do battle with "antimatter guns."
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During the Cold War, the Air Force funded numerous scientific studies of the basic physics of antimatter. With the knowledge gained, some Air Force insiders are beginning to think seriously about potential military uses -- for example, antimatter bombs small enough to hold in one's hand, and antimatter engines for 24/7 surveillance aircraft.

More cataclysmic possible uses include a new generation of super weapons -- either pure antimatter bombs or antimatter-triggered nuclear weapons; the former wouldn't emit radioactive fallout. Another possibility is antimatter- powered "electromagnetic pulse" weapons that could fry an enemy's electric power grid and communications networks, leaving him literally in the dark and unable to operate his society and armed forces.
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In 1929, Dirac suggested that the building blocks of atoms -- electrons (negatively charged particles) and protons (positively charged particles) -- have antimatter counterparts: antielectrons and antiprotons. One fundamental difference between matter and antimatter is that their subatomic building blocks carry opposite electric charges. Thus, while an ordinary electron is negatively charged, an antielectron is positively charged (hence the term positrons, which means "positive electrons"); and while an ordinary proton is positively charged, an antiproton is negative.
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Unlike regular nuclear bombs, positron bombs wouldn't eject plumes of radioactive debris. When large numbers of positrons and antielectrons collide, the primary product is an invisible but extremely dangerous burst of gamma radiation. Thus, in principle, a positron bomb could be a step toward one of the military's dreams from the early Cold War: a so-called "clean" superbomb that could kill large numbers of soldiers without ejecting radioactive contaminants over the countryside.
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But talk of "clean" superbombs worries critics. " 'Clean' nuclear weapons are more dangerous than dirty ones because they are more likely to be used," said an e-mail from science historian George Dyson of the Institute for Advanced Study in Princeton, N.J., author of "Project Orion," a 2002 study on a Cold War-era attempt to design a nuclear spaceship. Still, Dyson adds, antimatter weapons are "a long, long way off."
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Edwards' point man in that effort is Gerald Smith, former chairman of physics and Antimatter Project leader at Pennsylvania State University. Smith now operates a small firm, Positronics Research LLC, in Santa Fe, N.M. So far, the Air Force has given Smith and his colleagues $3.7 million for positron research, Smith told The Chronicle in August.

Smith is looking to store positrons in a quasi-stable form called positronium. A positronium "atom" (as physicists dub it) consists of an electron and antielectron, orbiting each other. Normally these two particles would quickly collide and self-annihilate within a fraction of a second -- but by manipulating electrical and magnetic fields in their vicinity, Smith hopes to make positronium atoms last much longer.

Smith's storage effort is the "world's first attempt to store large quantities of positronium atoms in a laboratory experiment," Edwards noted in his March speech. "If successful, this approach will open the door to storing militarily significant quantities of positronium atoms."
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In the meantime, the Air Force has been investigating the possibility of making use of a powerful positron-generating accelerator under development at Washington State University in Pullman, Wash. One goal: to see if positrons generated by the accelerator can be stored for long periods inside a new type of "antimatter trap" proposed by scientists, including Washington State physicist Kelvin Lynn, head of the school's Center for Materials Research.

A new generation of military explosives is worth developing, and antimatter might fill the bill, Lynn told The Chronicle: "If we spend another $10 billion (using ordinary chemical techniques), we're going to get better high explosives, but the gains are incremental because we're getting near the theoretical limits of chemical energy."