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83: Atomic Clock Shrunk

By David EpsteinJanuary 3, 2005 6:00 AM


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Researchers from the National Institute of Standards and Technology in Boulder, Colorado, are taking precision timekeeping where it has never gone before. In August they unveiled the guts of a miniature atomic clock—no larger than a sugar cube yet accurate to one second in 300 years. The downsized ticker could roll inexpensively off an assembly line, bringing atomic precision to devices ranging from cell phones to car navigation systems.

Like its desk-size cousins, the new atomic clock works by counting the vibrations of cesium atoms. Applying techniques from computer chip makers, the NIST team etched tiny holes into a silicon wafer and fixed a glass layer atop it. The researchers then injected cesium vapor into the etched cavity and sealed it with another glass layer. A laser shining through the glass tallies the cesium ticks, which calibrate a small, energy-efficient clock. “The vapor cell in an atomic clock needs to be heated,” says John Kitching of NIST, who leads the project. “Our cell is so small, it doesn’t take much power to heat—it could run on batteries.”

With built-in atomic clocks, portable GPS units could calculate their positions even more accurately than is possible today, and wireless communications could become more secure. Kitching thinks that is only the beginning: “We can’t even envision the most important uses yet.”

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