Atomic clock. Clock history. A Brief History of Atomic Timekeeping Instruments

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 oven is a sorting magnet, which has throughput 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 hours, which is a guarantee highest precision. 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.

AT modern world, when navigation is simply indispensable, atomic clocks have become indispensable assistants. They are able to locate spaceship, satellite, ballistic missile, aircraft, submarine, car automatically by satellite.

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 the modern world, atomic clocks can be made in any country of 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 not more than matchbox and their low power consumption - less than 1 Watt. And this is not the limit, perhaps in the future technical 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, 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.

Isidore Rabi, a professor of physics at Columbia University, proposed a never-before-seen project: a clock that works on the principle of an atomic beam of magnetic resonance. This happened in 1945, and already in 1949 the National Bureau of Standards released the first working prototype. It read vibrations of the ammonia molecule. Cesium entered the business much later: the NBS-1 model appeared only in 1952.

The National Physical Laboratory in England created the first cesium beam clock in 1955. More than ten years later, during the General Conference on Weights and Measures, a more advanced clock was presented, also based on vibrations in the cesium atom. The NBS-4 model was used until 1990.

Watch types

On the this moment There are three types of atomic clocks that operate on roughly the same principle. Cesium clock, the most accurate, splits the cesium atom magnetic field. The simplest atomic clock, the rubidium clock, uses rubidium gas enclosed in a glass bulb. And, finally, hydrogen atomic clocks take as a reference point hydrogen atoms closed in a shell of special material- it does not allow atoms to quickly lose energy.

What time is it now

In 1999, the US National Institute of Standards and Technology (NIST) proposed an even more advanced version of the atomic clock. The NIST-F1 model has an error of only one second in twenty million years.

Most Accurate

But NIST physicists didn't stop there. The scientists decided to develop a new chronometer, this time based on strontium atoms. The new watch runs on 60% of the previous model, which means that it loses one second not in twenty million years, but in as much as five billion.

Time measurement

An international agreement has determined the only exact frequency for the resonance of a cesium particle. This is 9,192,631,770 hertz - dividing the output signal by this number gives exactly one cycle per second.

Have you ever noticed that your clock in the house is showing different time? And how to understand which of all the options is correct? We will learn the answers to all these questions by thoroughly studying the principle of operation of atomic clocks.

Atomic clock: description and principle of operation

Let's first understand what the mechanism of an atomic clock is. An atomic clock is a device that measures time, but it uses its own vibrations as the periodicity of the process, and everything happens at the atomic and molecular level. Hence the accuracy.

It is safe to say that atomic clocks are the most accurate! It is thanks to them that the Internet and GPS navigation function in the world, we know the exact location of the planets in solar system. The error of this device is so minimal that we can confidently say that they are world-class! Thanks to atomic clocks, the entire world synchronization takes place, it is known where certain changes are located.

Who invented, who created, and also who came up with this miracle watch?

Back in the early forties of the twentieth century, it was known about the atomic beam of magnetic resonance. At first, its application did not concern watches in any way - it was only a theory. But already in 1945, Isidor Rabi proposed to create a device, the concept of which was that they work on the basis of the above technique. But they were arranged in such a way that they showed inaccurate results. And already in 1949, the National Bureau of Standards informed the whole world about the creation of the first atomic clock, which was based on molecular compounds of ammonia, and already in 1952, technologies were mastered to create a prototype based on cesium atoms.

Hearing about the atoms of ammonia and cesium, the question arises, but are these wonderful clocks radioactive? The answer is unequivocal - no! They do not have atomic decay.

Nowadays, there are many materials from which atomic clocks are made. For example, it is silicon, quartz, aluminum and even silver.

How does the device work?

Let's take a look at how nuclear-powered clocks look and work. To do this, we offer a description of their work:

For the correct functioning of this particular clock, not a pendulum is needed, nor a quartz oscillator. They use signals that arise due to the quantum transition of one electron between two energy levels of an atom. As a result, we are able to observe an electromagnetic wave. In other words, we get frequent fluctuations and an ultra-high level of system stability. Every year, due to new discoveries, processes are modernized. Not so long ago, the specialists of The National Institute fStandardsand Technology (NIST) became champions, setting an absolute world record. They were able to bring the accuracy of the atomic clock (based on strontium) to the very minimum deviation, namely: for 15 billion years, one second runs. Yes, yes, it didn’t seem to you that this is the age that is now being assigned to our Universe. This is a huge discovery! After all, it was strontium that played the most important role in this record. The moving atoms of strontium in its spatial lattice, which scientists created using a laser, acted as an analogue of the “ticking”. As always in science, in theory everything seems enchanting and already improved, but the instability of such a system may turn out to be less joyful in practice. It is because of its instability that the cesium-based device gained worldwide popularity.

Now consider what such a device consists of. The main details here are:

• quantum discriminator;
• quartz generator;
• electronics.

A quartz oscillator is a kind of self-oscillator, but to produce a resonant element, it uses piezoelectric modes of a quartz crystal.

Having a quantum discriminator and a quartz oscillator, under the influence of their frequency, they are compared and, if a difference is detected, the circuit feedback requires the crystal oscillator to adjust to the required value and improve stability and accuracy. As a result, at the output we see on the dial exact value, which means the exact time.

Early models had quite big sizes, however, in October 2013, BathysHawaii made a splash by releasing miniature nuclear wrist watch. At first, everyone took this statement as a joke, but it soon became clear that it was really true, and they function on the basis of the atomic source Cesium 133. The safety of the device is ensured by the fact that the radioactive element is contained in the form of a gas in a special capsule. Photos of this device scattered around the world.

Many in the topic of atomic clocks are interested in the issue of a power source. The battery is a lithium-ion battery. But alas, it is not yet known how long such a battery will last.

The BathysHawaii watch was truly the first atomic wrist watch. Previously, cases of release of a relatively portable device were already known, but, unfortunately, it did not have an atomic power source, but only synchronized with real overall clocks via wireless radio. It is also worth mentioning the cost of such a gadget. The pleasure was estimated at 12 thousand US dollars. It was clear that with such a price, watches would not gain wide popularity, but the company did not strive for this, because they released them in a very limited batch.

We know of several types of atomic clocks. There are no significant differences in their design and principles, but there are still some differences. So, the main ones are in the means of finding changes and their elements. The following types of watches can be distinguished:

1. Hydrogen. Their essence lies in the fact that hydrogen atoms are supported at the right level of energy, but the walls are made of a special material. Based on this, we conclude that it is hydrogen atoms that very quickly lose their energy state.
2. cesium. The basis for them are cesium beams. It is worth noting that these watches are the most accurate.
3. Rubidium. They are the simplest and very compact.

As mentioned earlier, atomic clocks are a very expensive gadget. Thus, the pocket watch Hoptroff No. 10 is a bright representative of a new generation of toys. The price of such a stylish and very accurate accessory is 78 thousand dollars. Only 12 copies were released. The mechanism of this device uses a high-frequency oscillatory system, which is also equipped with a GPS signal.

The company did not stop there and it is in its tenth version of the watch that it wants to apply the method of placing the mechanism in a gold case, which will be printed on a popular 3D printer. It has not yet been calculated exactly how much gold will be used for such a version of the case, but the estimated retail price of this masterpiece is already known - it amounted to about 50 thousand pounds sterling. And this is not the final price, although it takes into account all the volumes of research, as well as the novelty and uniqueness of the gadget itself.

Historical facts about the use of watches

How, when talking about atomic clocks, not to mention the most interesting facts, which are associated with them and time in general:

1. Did you know that in ancient egypt the oldest sundial ever found?
2. The error of atomic clocks is minimal - it is only 1 second for 6 million years.
3. Everyone knows that there are 60 seconds in a minute. But few people delved into how many milliseconds are in one second? And they are not many and not few - a thousand!
4. Every tourist who was able to visit London was sure to want to see Big Ben with their own eyes. But unfortunately, not many people know that Big Ben is not a tower at all, but the name of a huge bell that weighs 13 tons and rings inside the tower.
5. Have you ever wondered why the hands of our clocks go exactly from left to right, or how we used to say “clockwise”? This fact is directly related to how the shadow moves on the sundial.
6. The very first wristwatch was invented in the recent 1812. They were made by the founder of Breguet for the Queen of Naples.
7. Before the First World War, wrist watches were considered only a women's accessory, but soon, due to their convenience, they were also chosen by the male part of the population.

, Galileo) are impossible without atomic clocks. Atomic clocks are also used in satellite and terrestrial telecommunications systems, including base stations mobile communications, international and national bureaus of standards and time services, which periodically broadcast time signals by radio.

Clock device

The clock consists of several parts:

• quantum Discriminator,
• electronics complex.

National Frequency Standards Centers

Many countries have formed national centers for time and frequency standards:

• (VNIIFTRI), village Mendeleevo, Moscow region;
• (NIST), Boulder (USA, Colorado);
• National Institute of Advanced Industrial Science and Technology (AIST), Tokyo (Japan);
• Federal Physical and Technical Agency (German)(PTB), Braunschweig (Germany);
• National Laboratory of Metrology and Testing (fr.)(LNE), Paris (France).
• UK National Physical Laboratory (NPL), London, UK.

Scientists different countries work on the improvement of atomic clocks and the state primary standards of time and frequency based on them, the accuracy of such clocks is steadily increasing. In Russia, extensive research aimed at improving the characteristics of atomic clocks is being carried out at.

Types of atomic clocks

Not every atom (molecule) is suitable as a discriminator for atomic clocks. Choose atoms that are insensitive to various external influences: magnetic, electric and electromagnetic fields. There are such atoms in every range of the electromagnetic radiation spectrum. These are: atoms of calcium, rubidium, cesium, strontium, molecules of hydrogen, iodine, methane, osmium (VIII) oxide, etc. The hyperfine transition of the cesium atom was chosen as the main (primary) frequency standard. The characteristics of all other (secondary) standards are compared with this standard. In order to make such a comparison, so-called optical combs are currently used. (English)- radiation with a wide frequency spectrum in the form of equidistant lines, the distance between which is tied to the atomic frequency standard. Optical combs are obtained using a mode-locked femtosecond laser and microstructured fiber, in which the spectrum is broadened to one octave.

In 2006, researchers from the US National Institute of Standards and Technology, led by Jim Bergquist (eng. Jim Bergquist) developed a single atom clock. During transitions between the energy levels of the mercury ion, photons of the visible range are generated with a stability 5 times higher than the microwave radiation of cesium-133. The new clock may also find application in studies of the dependence of fundamental physical constants on time. As of April 2015, the most accurate atomic clock were watches created in National Institute US standards and technologies. The error was only one second in 15 billion years. Relativistic geodesy was cited as one of the possible applications of clocks, the main idea of ​​which is the use of a network of clocks as gravity sensors, which will help to make incredibly detailed three-dimensional measurements of the shape of the Earth.

Active development of compact atomic clocks for use in everyday life (wristwatches, mobile devices) is underway. At the beginning of 2011, an American company Symmetricom announced the commercial release of a cesium atomic clock the size of a small chip. The clock works on the basis of the effect of coherent population trapping. Their stability is 5 10 -11 per hour, weight - 35 g, power consumption - 115 mW.

Notes

1. New record for atomic clock accuracy set (indefinite) . Membrana (February 5, 2010). Retrieved March 4, 2011. Archived from the original on February 9, 2012.
2. These frequencies are typical for precision quartz resonators, with the highest quality factor and frequency stability achievable using the piezoelectric effect. In general, crystal oscillators are used at frequencies from a few kHz to several hundred MHz. ( Altshuller G. B., Elfimov N. N., Shakulin V. G. Crystal oscillators: Help Guide. - M.: Radio and communication, 1984. - S. 121, 122. - 232 p. - 27,000 copies.)
3. N. G. Basov and V. S. Letokhov Optical frequency standards. // UFN. - 1968. - T. 96, No. 12.
4. National metrology laboratories. NIST, February 3, 2011 (Retrieved June 14, 2011)
5. Oskay W., Diddams S., Donley A., Frotier T., Heavner T., et al. Single-Atom Optical Clock with High Accuracy // Phys. Rev. Lett. . - American Physical Society, July 4, 2006. - Vol. 97, no. 2. -

A sensation has spread around the scientific world - time is evaporating from our Universe! So far, this is only a hypothesis of Spanish astrophysicists. But the fact that the flow of time on Earth and in space is different has already been proven by scientists. Time flows more slowly under the influence of gravity, accelerating as you move away from the planet. The task of synchronizing terrestrial and cosmic time is performed by hydrogen frequency standards, which are also called "atomic clocks".

First atomic time appeared along with the advent of astronautics, atomic clocks appeared in the mid-1920s. Now atomic clocks have become commonplace, each of us uses them every day: they work with digital communications, GLONAS, navigation, and transport.

Mobile phone owners hardly think about what hard work in space is carried out for tight time synchronization, but we are talking about only millionths of a second.

The standard of exact time is stored in the Moscow region, at the Scientific Institute of Physical-Technical and Radio-Technical Measurements. There are 450 such watches in the world.

Russia and the USA are the monopolists for atomic clocks, but in the USA clocks work on the basis of cesium, a radioactive metal that is very harmful to the environment, and in Russia, on the basis of hydrogen, a safer durable material.

This watch does not have a dial and hands: it looks like a big barrel made of rare and valuable metals, filled with the most advanced technologies– high-precision measuring instruments and equipment with atomic standards. The process of their creation is very long, complex and takes place in conditions of absolute sterility.

For 4 years, the clock installed on the Russian satellite has been studying dark energy. By human standards, they lose accuracy by 1 second in many millions of years.

Very soon, an atomic clock will be installed on Spektr-M, a space observatory that will see how stars and exoplanets are formed, look over the edge black hole at the center of our galaxy. According to scientists, due to the monstrous gravity, time flows here so slowly that it almost stops.

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