PORTLAND, Ore. — Since 1999, the National Institute of Standards and Technology (NIST) has been using an atomic clock -- called NIST-F1 -- with accuracy of plus or minus one second over 100 million years. And although that sounds plenty accurate, NIST believes some applications could use three-times greater accuracy.
The new standard called NIST-F2 unveiled this week -- after a decade of development -- is accurate to within plus or minus one second over 300 million years. NIST declines to list any applications that can make immediate use of the higher accuracy, but F2's lead designer, Steven Jefferts, noted that past releases of new more accurate clocks had spawned new unforeseen applications, and he has no reason to believe this release will be any different.
NIST-F2 is similar to NIST-F1 in that it makes use of a fountain of cesium atoms -- supercooled by six lasers -- to divide a second into 9,192,631,770 vibrations per second. However, numerous novel new features in F2 contribute to its higher accuracy, including components that shrink and expand by as much as one centimeter as the clock is cycled to and from very cold temperatures. Also the six lasers used to cool the cesium atoms have been optimized in a new configuration.
But by and far the biggest contributor to the F2's higher accuracy is the lower temperature of the vertical flight chamber that contains the cesium atomic fountain. The old F1 standard ran the flight chamber at near room temperature (80 degrees Fahrenheit) whereas the flight chamber in F2 is cooled with liquid nitrogen to minus 316 degrees Fahrenheit, thus quieting its background radiation and eliminating the need for the many small variations that had to be corrected in F1.
The National Institute of Standards and Technology (NIST) has a new atomic clock time standard that is three times as accurate over the existing standard, which is 15 years old.
NIST reported their results to the International Bureau of Weights and Measures (Paris), which has certified that NIST-F2, is now the world’s most accurate time standard. NIST will continue to run both clocks for now, servicing about 8 billion automated request per day to synchronize clocks in computers and network devices. NIST also time-stamps hundreds of billions of dollars in U.S. financial transactions each day plus updates about 50 million watches and other clocks via radio broadcasts. Anyone can access NIST's super-accurate time base by clicking on the Official NIST Time Base.
For the future, NIST is exploring a switch from the microwave frequencies of F1 and F2 to visible light frequencies that divide the second into much smaller slices. Such optical atomic clocks could potentially provide time standards that are 100 times more accurate -- to within plus or minus one second over 30 billion years.
— R. Colin Johnson, Advanced Technology Editor, EE Times