Atomic clock

Atomic Clock . It is a type of watch that uses a normal atomic resonance frequency to power its counter.


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  • 1 Accuracy
  • 2 Operation
  • 3 Atomic pendulum
  • 4 News
  • 5 Sources


The UK National Laboratory’s atomic clock is the most accurate in the world, according to recent research. CsF2 is based on a cesium emission source , in which the tick is marked by the measure of energy required to change a property of the cesium atoms called “spin.”

According to the international definition, what is measured is the electromagnetic waves necessary to carry out this spin change. The international time standard is calculated with a network of more than 300 clocks worldwide. The data is sent by satellite and averaged in France .

But the ticking of any one of them may lose precision, so the average is corrected using six “primary frequency standards” in Europe , the US and Japan . That corrected result, called the “International Atomic Time”, is compared from time to time with astronomical measurements of time . Occasionally a second is added or removed to correct any time discrepancies.

Studies on its operation (published in the journal clic Metrology ) show that it is twice as accurate as previously thought. It can lose or gain less than a second in about 138 million years.

The United Kingdom is one of several nations providing the “second standard”, but international competition for precision could displace this device from first place.


Atomic clock

While the mechanical clock depends on a pendulum to function, the atomic works with the frequency of hyper-fine energy transitions (in microwave ranges ) in atoms .

At one end of the cesium clock is a furnace with a cesium plate from which ions of this metal evaporate . Ions occur in two states dependent on the spin of the last electron in cesium. These states have an energy frequency of 9,192,631,770 Hza and in each different state the ions have different magnetic properties. After evaporation , a magnet is used to separate the ions and discard those with higher energy. The ions with less energy go to a chamber.

A microwave radio transmitter emits the chamber cavity evenly with radio waves. When the frequency of the radiated wave couples with the frequency of the hyper-fine transition of cesium, cesium ions absorb radiation and emit light . A photoelectric cell captures the exact moment of emission; This cell has associated electronic instrumentation that connects it to the radio-transmitter and adjusts its frequency.

Finally, connected to said electronics there is a counter that records the times that the radio transmitter has emitted a wave in the frequency of cesium and a computer makes the remaining calculations until they are converted into a readable format or a one pulse radio transmission in the spectrum. radio in which the receiving devices listen. Of course, the real clock is the counter.

To make the measurement through these particles it is necessary to create an electromagnetic field that does not exist naturally in the Universe. The process is carried out within a “magneto-optical trap”, a sphere the size of a melon in which cesium atoms are injected and spread, locked in a magnetic field , six rays of laser light .

The clock’s electronic system marks one second when 9,192,631,770 periods of oscillation of the electric field have occurred . “From counting that number of oscillations comes the accuracy of the atomic clock.”

Atomic pendulum

Inside the clock, the cesium atoms are gathered into clusters of 100 million atoms and are passed through a cavity where they are exposed to electromagnetic waves. The color , or frequency , is adjusted until the spin is seen to change. It is then that scientists know that waves have the indicated frequency to define a second. The CsF2 provides an “atomic pendulum” that clocks from around the world can use to check that they are correcting the time.

This verification is carried out by the International Bureau of Weights and Measures (BIPM, for its French acronym), which collects second definitions of six “primary frequency standards”, the CsF2 in the United Kingdom, two in France and one in France. United States , one in Germany and one in Japan .

For those high-precision atomic pendulums, absolute precision is a permanent goal. Based on 2010 measurements , the CsF2 was on par with the rest in terms of long-term accuracy: about one part in 2,500,000,000,000,000.

But measurements by Krzystof Szymaniec of the NPL and his colleagues at the University of Pennsylvania in the United States have shown that its accuracy is double.


A cesium clock marking the UK atomic time is now the most accurate in the world, according to a new assessment of the machine by scientists at the National Laboratory for Physics (NPL) in the UK. The watch in question is an elite mechanism. It belongs to a prestigious group of cesium watches built by laboratories in Europe , the USA and Japan.

Its objective is to measure time with national standards that are averaged to produce International Atomic Time and Coordinated Universal Time, used as scales throughout the world for relevant processes such as global communication, satellite navigation , topography and computer transactions. from financial and stock markets. The methods used to improve the UK watch NPL-CSF2 can also be used to evaluate cesium chronographs from other countries.


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