Washington: A caesium fountain clock that keeps the United Kingdom’s atomic time is now the most accurate long-term timekeeper in the world.
It was confirmed after the evaluation of the clock by a team of physicists at the National Physical Laboratory (NPL) in the United Kingdom and Penn State University in the United States.
The clock is one of an elite group of caesium fountain clocks that have been built by the timing labs in Europe, the United States, and Japan as their national “primary frequency standard” for the measurement of time.
These national standards are averaged to produce International Atomic Time and Universal Coordinated Time, which are used as time scales worldwide for such critical processes as global communications, satellite navigation and surveying, and time stamping for the computerized transactions of financial and stock markets.
The methods used to improve the U.K. clock also can be used to evaluate the caesium fountain clocks of other countries, substantially improving the world’s most accurate methods of keeping time.
“The improvements that we report in our paper have reduced significantly the caesium fountain clock’s two largest sources of measurement uncertainties -- Doppler shifts and the microwave-lensing frequency shift,” said NPL Project Leader Krzysztof Szymaniec.
The physicists evaluated the recently upgraded caesium fountain clock with physical measurements at NPL and mathematical models developed at Penn State.
The study will be published in the October 2011 issue of the international scientific journal Metrologia.