Nov 18, 2008 04:00 PM | 7
It sounds like something a villain might construct in a James Bond film: a laser, trained on a thin gold target, that churns out antimatter to annihilate ordinary matter. But scientists at Lawrence Livermore National Laboratory have announced that they made just such a device, from which they were able to detect the production of more than a million positrons, the antimatter particle counterpart to electrons. (By this detection they infer the presence of many times more positrons, in the realm of 100 billion particles.)
Livermore high-energy physicist Hui Chen [pictured at left] and her colleagues used a modified electron detector to pick up the presence of positrons, which quickly destroy electrons (and themselves), radiating energy in the form of gamma-ray photons. (Electrons and positrons have the same mass but opposite charge and so are detectable by similar means.)
Antimatter is not as exotic as it sounds: anyone who has undergone a PET scan has harbored antiparticles, albeit briefly—PET stands for positron-emission tomography. But it's far less prevalent than ordinary matter, even though theory predicts the two types would have been produced in equal parts in the big bang.
Somehow matter won out over time, eventually carving a stable enough preponderance to allow life to take root. Scientists track the annihilation of positrons and electrons, and the resulting gamma rays, for many purposes, including the aforementioned medical scans and searches for the mysterious and pervasive hypothetical stuff known as dark matter.
CREDIT: Lawrence Livermore National Laboratory
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