Time on a Chip: The Incredible Shrinking Atomic Clock

Dr. John Kitching, a physicist with the National Institute of Standards and Technology in Boulder, Co, is working to develop an atomic clock the size of a microchip. Standard atomic clocks today are about the size of a deck of cards and unlike the microchip versions can not fit inside small portable devices such as cell phones and Global positioning Systems. The NIST-F1 atomic clock provides the national time reference and is over six feet tall. Dr. Kitching's micro-clock uses the same element as the F1, cesium, as it's basic reference signal. Unlike quarts crystals, which are the standard units used in watches other small devices today, cesium atoms oscillate with a much more accurate frequency, 9.2 billion cycles per second, and don't have as large of variations with temperature. The chip for the micro-clock is basic silicon, but with a well filled with about 100 cesium atoms and covered by a tiny glass dome. A laser is shot through the atoms and "tuned" until they oscillate. To keep the atoms at the precise frequency, a small heater surrounds the well and keeps the atoms at 212 degrees F. The heater expends a lot of power, about one AA battery in a few days, and is the major drawback of the clock. Price is another drawback at the present, with each one costing around 100 dollars.