Wednesday, February 1, 2012

India develops caesium fountain clock for accurate record to time

By Syed Akbar
Hyderabad: India’s timekeeper National Physical Laboratory has
successfully developed a caesium fountain clock that could help in
refining the definition of one second and bettering the Indian
Standard Time. The caesium fountain clock is the most accurate of all
the atomic clocks on the earth. It is 100 times better than the
traditional caesium clocks used by timekeeping laboratories around the

“Ordinary caesium clocks are quite accurate and they either lose or
gain one second in about 30,000 to 40,000 years. The caesium fountain
clock developed by us is 100 times better than ordinary caesium
clocks. Our clock is precision-accurate and loses or gains one second
once in several million years. There are less than a dozen such clocks
on the earth,” said Dr Amitava Sen Gupta, senior scientist, time and
frequency standards, National Physical Laboratory.

To help visualise this level of accuracy – imagine measuring the
distance between the Earth and the Sun (about 150 million km) with an
accuracy of one-tenth of a millimetre.

He told this correspondent that the caesium fountain clock at NPL had
already sent the first clock signal, technically called Ramsey
Fringes. “We are presently evaluating its precision levels. The new
clock will help in increasing the accuracy of the Indian Standard
Time. It will also contribute to the International Bureau of Weights
and Measures (BIPM), which runs the world time - Coordinated Universal
Time (UTC),” Dr Amitava observed.

Since this laser-cooled caesium atoms clock also acts as primary
frequency standard, it will help in the definition of one second. The
second was last defined in 1967 and there are now demands from experts
that it needs to be redefined to meet the modern requirements of
advanced scientific, meteorological and aviation institutions.
Incidentally, time experts on Thursday debated in Switzerland whether
to do away with the leap second that is added to the world clock every
few years to adjust with the solar mean time thanks to the slowing
down of the earth’s rotation.

According to time experts, the operation of modern-day technology
requires an accurate knowledge of time. Telecommunications rely
heavily on timing to operate switches routing signals through
networks. The Global Positioning System, which is used for navigation
of ships, airplanes, etc., relies on the accuracy of the time signals
broadcast from atomic clocks on satellites orbiting the earth. In
metrology, most units are exactly defined in terms of the second.
Accurate time is required for many areas of fundamental physics such
as astrophysics, geophysics, and relativistic physics.

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