Atomic reactors and electronic crystals Konstantin Chilovsky (b. 1881), Russian engineer, inventor. He invented a device for detecting submarines, which was widely used during the First World War (1914-1918). For the invention he was awarded the French Order

Firstly, the clock uses humanity as a means of program-time control.

Secondly, today the measurement of time is also the most accurate type of measurement of all conducted: the accuracy of time measurement is now determined by an incredibly error of the order of 1 10-11%, or 1 s in 300 thousand years.

And modern people achieved such accuracy when they began to use atoms, which, as a result of their oscillations, are the regulator of the atomic clock. Cesium atoms are in the two energy states we need (+) and (-). Electromagnetic radiation with a frequency of 9,192,631,770 hertz is produced when atoms move from the state (+) to (-), creating a precise constant periodic process - the controller of the atomic clock code.

In order for atomic clocks to work accurately, cesium must be evaporated in a furnace, as a result of which its atoms are ejected. Behind the furnace is a sorting magnet, which has the capacity of atoms in the (+) state, and in it, due to irradiation in a microwave field, the atoms go into the (-) state. The second magnet directs atoms that have changed state (+) to (-) to the receiving device. Many atoms that have changed their state are obtained only if the frequency of the microwave emitter coincides exactly with the frequency of vibrations of cesium 9 192 631 770 hertz. Otherwise, the number of atoms (-) in the receiver decreases.

Instruments constantly monitor and adjust the constancy of the frequency 9 192 631 770 hertz. So, the dream of watch designers came true, an absolutely constant periodic process was found: a frequency of 9,192,631,770 hertz, which regulates the course of atomic clocks.

Today, as a result of international agreement, the second is defined as the radiation period multiplied by 9,192,631,770, corresponding to the transition between two hyperfine structural levels of the ground state of the cesium atom (cesium-133 isotope).

To measure the exact time, you can also use vibrations of other atoms and molecules, such as atoms of calcium, rubidium, cesium, strontium, hydrogen molecules, iodine, methane, etc. However, the radiation of the cesium atom is recognized as the frequency standard. In order to compare the vibrations of different atoms with a standard (cesium), a titanium-sapphire laser was created that generates a wide frequency range in the range from 400 to 1000 nm.

The first creator of quartz and atomic clocks was an English experimental physicist Essen Lewis (1908-1997). In 1955, he created the first atomic frequency (time) standard on a beam of cesium atoms. As a result of this work, 3 years later (1958) a time service emerged based on the atomic frequency standard.

In the USSR, Academician Nikolai Gennadievich Basov put forward his ideas for creating atomic clocks.

So, atomic clock, one of the exact types of clocks is a device for measuring time, where the natural oscillations of atoms or molecules are used as a pendulum. The stability of atomic clocks is the best among all existing types of clocks, which is the key to the highest accuracy. The atomic clock generator produces more than 32,768 pulses per second, unlike conventional clocks. Oscillations of atoms do not depend on air temperature, vibrations, humidity and many other external factors.

In the modern world, when navigation is simply indispensable, atomic clocks have become indispensable assistants. They are able to determine the location of a spacecraft, satellite, ballistic missile, aircraft, submarine, car automatically via satellite communications.

Thus, for the last 50 years, atomic clocks, or rather cesium clocks, have been considered the most accurate. They have long been used by timekeeping services, and time signals are also broadcast by some radio stations.

The atomic clock device includes 3 parts:

quantum Discriminator,

quartz oscillator,

electronics complex.

A quartz oscillator generates a frequency (5 or 10 MHz). The oscillator is an RC radio generator, in which the piezoelectric modes of a quartz crystal are used as a resonant element, where the atoms that have changed the state (+) to (-) are compared. To increase stability, its frequency is constantly compared with the vibrations of the quantum discriminator (atoms or molecules) . When there is a difference in oscillations, the electronics adjusts the frequency of the quartz oscillator to zero, thereby increasing the stability and accuracy of the clock to the desired level.

In today's world, atomic clocks can be made in any country in the world for use in everyday life. They are very small in size and beautiful. The size of the latest novelty of atomic clocks is no more than a matchbox and their low power consumption is less than 1 watt. And this is not the limit, perhaps in the future technological progress will reach mobile phones. In the meantime, compact atomic clocks are installed only on strategic missiles to increase the accuracy of navigation many times over.

Today, men's and women's atomic watches for every taste and budget can be bought in online stores.

In 2011, the world's smallest atomic clock was created by Symmetricom and the Sandia National Laboratory. This watch is 100 times more compact than previous commercially available versions. The size of an atomic chronometer is no larger than a matchbox. It needs 100 mW of power to operate, which is 100 times less than its predecessors.

It was possible to reduce the size of the clock by installing instead of springs and gears a mechanism that operates on the principle of determining the frequency of electromagnetic waves emitted by cesium atoms under the influence of a laser beam of negligible power.

Such watches are used in navigation, as well as in the work of miners, divers, where it is necessary to accurately synchronize time with colleagues on the surface, as well as accurate time services, because the error of atomic clocks is less than 0.000001 fractions of a second per day. The cost of the record-breaking small Symmetricom atomic clock was about $1,500.

A new impetus in the development of devices for measuring time was given by atomic physicists.

In 1949, the first atomic clock was built, where the source of oscillations was not a pendulum or a quartz oscillator, but signals associated with the quantum transition of an electron between two energy levels of an atom.

In practice, such clocks turned out to be not very accurate, moreover, they were bulky and expensive and were not widely used. Then it was decided to turn to the chemical element - cesium. And in 1955, the first atomic clock based on cesium atoms appeared.

In 1967, it was decided to switch to the atomic time standard, since the Earth's rotation is slowing down and the magnitude of this slowdown is not constant. This greatly hampered the work of astronomers and the keepers of Time.

The Earth is currently spinning at a rate of about 2 milliseconds per 100 years.

Fluctuations in the duration of the day also reach thousandths of a second. Therefore, the accuracy of Greenwich Mean Time (the world standard since 1884) has become insufficient. In 1967, the transition to the atomic time standard took place.

Today, a second is a period of time exactly equal to 9,192,631,770 radiation periods, which corresponds to the transition between two hyperfine levels of the ground state of the Cesium 133 atom.

At the moment, Coordinated Universal Time is used as the time scale. It is formed by the International Bureau of Weights and Measures by combining data from the timekeeping laboratories of various countries, as well as data from the International Earth Rotation Service. Its accuracy is almost a million times better than the astronomical Greenwich Mean Time.

A technology has been developed that will make it possible to radically reduce the size and cost of ultra-precise atomic clocks, which will make it possible to widely use them in mobile devices for various purposes. Scientists were able to create an atomic time standard of ultra-small size. Such atomic clocks consume less than 0.075 W and have an error of no more than one second in 300 years.

A US research team has succeeded in creating an ultra-compact atomic standard. It became possible to power atomic clocks from conventional AA batteries. Ultra-precise atomic clocks, usually at least a meter high, were placed in a volume of 1.5x1.5x4 mm

An experimental atomic clock based on a single mercury ion has been developed in the United States. They are five times more accurate than cesium, which is accepted as an international standard. Cesium clocks are so accurate that a difference of one second will be reached only after 70 million years, and for mercury clocks this period will be 400 million years.

In 1982, a new astronomical object, a millisecond pulsar, intervened in the dispute between the astronomical definition of the Time standard and the atomic clock that won it. These signals are as stable as the best atomic clocks

Did you know?

The first watch in Russia

In 1412, a clock was placed in Moscow in the courtyard of the Grand Duke behind the Church of the Annunciation, and Lazar, a Serb monk who came from the Serbian land, made them. Unfortunately, the description of these first clocks in Russia has not been preserved.

How did the chimes appear on the Spasskaya Tower of the Moscow Kremlin?

In the 17th century, the Englishman Christopher Galovey made the chimes for the Spasskaya Tower: the hour circle was divided into 17 sectors, the only clock hand was motionless, pointing down and pointing at any number on the dial, but the dial itself rotated.

Often we hear the phrase that atomic clocks always show the exact time. But from their name it is difficult to understand why atomic clocks are the most accurate or how they work.

The fact that the name contains the word "atomic" does not mean at all that the watch is a danger to life, even if thoughts of an atomic bomb or a nuclear power plant immediately come to mind. In this case, we are just talking about the principle of the clock. If in ordinary mechanical clocks gears perform vibrational movements and their movements are counted, then in atomic clocks oscillations of electrons inside atoms are counted. To better understand the principle of operation, let's recall the physics of elementary particles.

All substances in our world are made up of atoms. Atoms are made up of protons, neutrons and electrons. Protons and neutrons combine with each other to form a nucleus, which is also called a nucleon. Electrons move around the nucleus, which can be at different energy levels. The most interesting thing is that when absorbing or giving off energy, an electron can move from its energy level to a higher or lower one. An electron can receive energy from electromagnetic radiation by absorbing or emitting electromagnetic radiation of a certain frequency at each transition.

Most often there are watches in which atoms of the element Cesium -133 are used to change. If in 1 second the pendulum conventional watches makes 1 oscillatory motion, then the electrons in atomic clocks based on Cesium-133, when moving from one energy level to another, they emit electromagnetic radiation with a frequency of 9192631770 Hz. It turns out that one second is divided into exactly this number of intervals, if it is calculated in atomic clocks. This value was officially adopted by the international community in 1967. Imagine a huge dial, where there are not 60, but 9192631770 divisions, which are only 1 second. It is not surprising that atomic clocks are so accurate and have a number of advantages: atoms do not age, do not wear out, and the oscillation frequency will always be the same for one chemical element, thanks to which it is possible to simultaneously compare, for example, the readings of atomic clocks far in space and on Earth, not afraid of mistakes.

Thanks to atomic clocks, mankind in practice was able to test the correctness of the theory of relativity and make sure that, than on Earth. Atomic clocks are installed on many satellites and spacecraft, they are used for telecommunications needs, for mobile communications, they compare the exact time on the entire planet. Without exaggeration, it was thanks to the invention of the atomic clock that humanity was able to enter the era of high technology.

How do atomic clocks work?

Cesium-133 is heated by evaporating cesium atoms, which are passed through a magnetic field, where atoms with the desired energy states are selected.

Then the selected atoms pass through a magnetic field with a frequency close to 9192631770 Hz, which creates a quartz oscillator. Under the influence of the field, the cesium atoms again change their energy states, and fall on the detector, which fixes when the largest number of incoming atoms will have the “correct” energy state. The maximum number of atoms with a changed energy state indicates that the frequency of the microwave field is chosen correctly, and then its value is fed into an electronic device - a frequency divider, which, reducing the frequency by an integer number of times, gets the number 1, which is the reference second.

Thus, the cesium atoms are used to check the correct frequency of the magnetic field produced by the crystal oscillator, helping to keep it constant.

It is interesting: although the atomic clocks that exist today are unprecedentedly accurate and can run without errors for millions of years, physicists are not going to stop there. Using atoms of various chemical elements, they are constantly working to improve the accuracy of atomic clocks. Of the latest inventions - atomic clocks on strontium, which are three times more accurate than their cesium counterpart. It would take them 15 billion years to be just a second behind – a time longer than the age of our universe…

If you find an error, please highlight a piece of text and click Ctrl+Enter.

High-precision atomic clocks that make an error of one second in 300 million years. This clock, which replaced an old model that had a one-second error in a hundred million years, now sets the standard for American civil time. Lenta.ru decided to recall the history of the creation of atomic clocks.

First atom

In order to create a clock, it is enough to use any periodic process. And the history of the emergence of time measuring instruments is partly the history of the emergence of either new energy sources or new oscillatory systems used in watches. The simplest clock is probably the sun clock, requiring only the sun and an object to cast a shadow to operate. The disadvantages of this method of determining the time are obvious. Water and hourglasses are no better either: they are suitable only for measuring relatively short periods of time.

The oldest mechanical clock was found in 1901 near the island of Antikythera on a sunken ship in the Aegean Sea. They contain about 30 bronze gears in a wooden case measuring 33 by 18 by 10 centimeters and date back to around 100 BC.

For almost two thousand years, mechanical watches have been the most accurate and reliable. The appearance in 1657 of the classic work of Christian Huygens "Pendulum Clock" ("Horologium oscillatorium, sive de motu pendulorum an horologia aptato demonstrationes geometrica") with a description of a time reference device with a pendulum as an oscillating system, was probably the apogee in the history of the development of mechanical devices of this type.

However, astronomers and navigators still used the starry sky and maps to determine their location and exact time. The first electric clock was invented in 1814 by Francis Ronalds. However, the first such instrument was inaccurate due to its sensitivity to temperature changes.

The further history of watches is connected with the use of different oscillatory systems in devices. Introduced in 1927 by employees of Bell Labs, quartz watches used the piezoelectric properties of a quartz crystal: when an electric current is applied to it, the crystal begins to shrink. Modern quartz chronometers can achieve an accuracy of up to 0.3 seconds per month. However, since quartz is subject to aging, over time the watch becomes less accurate.

With the development of atomic physics, scientists proposed using particles of matter as oscillatory systems. This is how the first atomic clock appeared. The idea of ​​using atomic vibrations of hydrogen to measure time was suggested back in 1879 by the English physicist Lord Kelvin, but this became possible only by the middle of the 20th century.

Reproduction of a painting by Hubert von Herkomer (1907)

In the 1930s, the American physicist and discoverer of nuclear magnetic resonance, Isidore Rabi, began working on cesium-133 atomic clocks, but the outbreak of war prevented him. Already after the war, in 1949, the first molecular clock using ammonia molecules was created at the US National Committee of Standards with the participation of Harold Lyonson. But the first such instruments for measuring time were not as accurate as modern atomic clocks.

The relatively low accuracy was due to the fact that due to the interaction of ammonia molecules with each other and with the walls of the container in which this substance was located, the energy of the molecules changed and their spectral lines broadened. This effect is very similar to the friction in a mechanical watch.

Later, in 1955, Louis Esssen of the UK's National Physical Laboratory introduced the first caesium-133 atomic clock. This clock accumulated an error of one second in a million years. The device was named NBS-1 and began to be considered a cesium frequency standard.

The circuit diagram of an atomic clock consists of a crystal oscillator controlled by a feedback discriminator. The oscillator uses the piezoelectric properties of quartz, while the discriminator uses the energy vibrations of atoms, so that the vibrations of quartz are tracked by signals from transitions from different energy levels in atoms or molecules. Between the generator and the discriminator there is a compensator tuned to the frequency of atomic vibrations and comparing it with the vibration frequency of the crystal.

The atoms used in the clock must provide stable vibrations. Each frequency of electromagnetic radiation has its own atoms: calcium, strontium, rubidium, cesium, hydrogen. Or even molecules of ammonia and iodine.

time standard

With the advent of atomic time measuring instruments, it became possible to use them as a universal standard for determining the second. Since 1884, Greenwich time, considered the world standard, has given way to the standard of atomic clocks. In 1967, by decision of the 12th General Conference of Weights and Measures, one second was defined as the duration of 9192631770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom. This definition of a second does not depend on astronomical parameters and can be reproduced anywhere on the planet. Cesium-133, used in the standard atomic clock, is the only stable isotope of cesium with 100% abundance on Earth.

Atomic clocks are also used in the satellite navigation system; they are necessary to determine the exact time and coordinates of the satellite. Thus, each satellite of the GPS system has four sets of such clocks: two rubidium and two cesium, which provide a signal transmission accuracy of 50 nanoseconds. The Russian satellites of the GLONASS system also have cesium and rubidium atomic time measuring instruments, and the satellites of the unfolding European geopositioning system Galileo are equipped with hydrogen and rubidium ones.

The accuracy of hydrogen clocks is the highest. It is 0.45 nanoseconds in 12 hours. Apparently, the use of such accurate clocks by Galileo will bring this navigation system to the fore in 2015, when its 18 satellites will be in orbit.

Compact atomic clock

Hewlett-Packard was the first company to develop a compact atomic clock. In 1964, she created the HP 5060A cesium instrument, the size of a large suitcase. The company continued to develop this direction, but since 2005 it has sold its atomic clock division to Symmetricom.

In 2011, Draper Laboratories and Sandia National Laboratories developed and Symmetricom released the first Quantum miniature atomic clock. At the time of release, they cost about 15 thousand dollars, were enclosed in a sealed case measuring 40 by 35 by 11 millimeters and weighed 35 grams. The power consumption of the watch was less than 120 milliwatts. Initially, they were developed by order of the Pentagon and were intended to serve navigation systems that function independently of GPS systems, for example, deep under water or land.

Already at the end of 2013, the American company Bathys Hawaii introduced the first "wrist" atomic clock. They use the SA.45s chip manufactured by Symmetricom as the main component. Inside the chip is a capsule with cesium-133. The design of the watch also includes photocells and a low-power laser. The latter provides heating of gaseous cesium, as a result of which its atoms begin to move from one energy level to another. The measurement of time is just made by fixing such a transition. The cost of the new device is about 12 thousand dollars.

Trends towards miniaturization, autonomy and accuracy will lead to the fact that in the near future there will be new devices using atomic clocks in all areas of human life, from space research on orbiting satellites and stations to domestic applications in indoor and wrist systems.