Arrows of time: how atomic clocks work. Atomic clock

, 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 standards bureaus, and time services, which periodically broadcast time signals by radio.

Clock device

The watch consists of several parts:

quantum discriminator,
electronics complex.

National Frequency Standards Centers

Many countries have formed national time and frequency standards centers:

(VNIIFTRI), Mendeleevo village, 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 (French)(LNE), Paris (France).
UK National Physical Laboratory (NPL), London, UK.

Scientists from different countries are working to improve atomic clocks and state primary time and frequency standards based on them; the accuracy of such clocks is steadily increasing. In Russia, extensive research aimed at improving the performance of atomic clocks is being carried out in.

Types of atomic clocks

Not every atom (molecule) is suitable as a discriminator for an atomic clock. Atoms are selected 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 performance of all other (secondary) standards is 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 produced using a mode-locked femtosecond laser and microstructured optical fiber, in which the spectrum is broadened to one octave.

In 2006, researchers from the American National Institute of Standards and Technology, led by Jim Bergquist, developed a clock operating on a single atom. Transitions between energy levels of the mercury ion generate photons in the visible range 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 changes in fundamental physical constants on time. As of April 2015, the most accurate atomic clock was a watch created at the US National Institute of Standards and Technology. The error was only one second in 15 billion years. One of the possible applications of the clocks was relativistic geodesy, the main idea of which is to use a network of clocks as gravitational sensors, which will help to carry out 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). 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 operates based on the effect of coherent population capture. Their stability is 5 10 -11 per hour, weight is 35 g, power consumption is 115 mW.

Notes

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

Isidor Rabi, a physics professor at Columbia University, has proposed a never-before-seen project: a clock operating 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 the vibrations of the ammonia molecule. Cesium came into use 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 powered by vibrations in the cesium atom. Model NBS-4 was used until 1990.

Types of watches

At the moment, there are three types of atomic clocks, which work on approximately the same principle. Cesium clocks, the most accurate, separate the cesium atom magnetic field. The simplest atomic clock, the rubidium clock, uses rubidium gas enclosed in a glass bulb. And finally, the hydrogen atomic clock takes as its reference point hydrogen atoms, closed in a shell of a special material - it prevents the atoms from quickly losing energy.

What time is it

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 allows for an error of only one second every twenty million years.

The most accurate

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

Measuring time

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

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 rotation of the Earth is slowing down and the magnitude of this slowdown is not constant. This made the work of astronomers and time keepers much more difficult.

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

Fluctuations in the length of the day also reach thousandths of a second. Therefore, the accuracy of Greenwich Mean Time (generally accepted worldwide 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 periods of radiation, which corresponds to the transition between two hyperfine levels of the ground state of the Cesium 133 atom.

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

A technology has been developed that will radically reduce the size and cost of ultra-precise atomic clocks, which will make it possible to widely use them in mobile devices for a wide variety of 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 group has succeeded in creating an ultra-compact atomic standard. It has become possible to power atomic clocks from ordinary AA batteries. Ultra-precise atomic clocks, usually at least a meter high, were placed in a volume of 1.5x1.5x4 mm

In the USA, an experimental atomic clock based on one mercury ion was developed. They are five times more accurate than cesium, which is accepted as the international standard. Cesium clocks are so accurate that it will take 70 million years for a difference of one second to be achieved, while 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 defeated it. These signals are as stable as the best atomic clocks

Did you know?

The first clocks in Rus'

In 1412 in Moscow, a clock was placed in the courtyard of the Grand Duke behind the Church of the Annunciation, and it was made by Lazar, a Serbian monk who came from the Serbian land. Unfortunately, no description of these first clocks in Rus' has been preserved.

________

How did the chiming clock appear on the Spasskaya Tower of the Moscow Kremlin?

In the 17th century, the Englishman Christopher Galloway made chimes for the Spasskaya Tower: the hour circle was divided into 17 sectors, the only clock hand was stationary, directed downwards and pointed at some number on the dial, but the dial itself rotated.

Have you ever noticed that your clock in the house shows different times? And how do you know which of all the options is correct? We will learn the answers to all these questions by thoroughly studying the operating principle of atomic clocks.

Atomic clock: description and principle of operation

Let's first understand what the atomic clock mechanism is. An atomic clock is a device with which time is measured, but it uses its own vibrations as the periodicity of the process, and everything happens at the atomic and molecular level. Hence such 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 the atomic clock, the entire world synchronization occurs; 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 had nothing to do with watches - it was only a theory. But already in 1945, Isidor Rabi proposed creating a device, the concept of which was that they would work based on the technique described above. But they were designed in such a way that they did not show accurate results. And already in 1949, the National Bureau of Standards notified 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.

Having heard about ammonia and cesium atoms, the question arises: is this wonderful clock radioactive? The answer is clear - no! There is no atomic decay in them.

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

How does the device work?

Let's figure out what a atomic energy clock looks like and how it works. To do this, we offer a description of their work:

For the correct functioning of this particular clock, neither a pendulum nor a quartz oscillator is needed. They use signals that arise from the quantum transition of a single electron between two energy levels of an atom. As a result, we are able to observe 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 long ago, specialists from The National Institute of Standards and Technology (NIST) became record holders, 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: in 15 billion years one second ticks by. Yes, yes, you didn’t think so, this is exactly the age currently assigned to our Universe. This is a colossal discovery! After all, it was strontium that played the most important role in this record. An analogue of the “tick” was the moving strontium atoms in its spatial lattice, which scientists created using a laser. 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 precisely because of its instability that the cesium device has gained worldwide popularity.

Now let's look at what such a device consists of. The main details here are:

quantum discriminator;
quartz generator;
electronics.

A quartz oscillator is similar to a 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 when 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 the exact value on the dial, and therefore the exact time.

Early models were quite large in size, but in October 2013, the Bathys Hawaii company made a splash by releasing a miniature atomic wristwatch. At first everyone took this statement as a joke, but it soon became clear that it was indeed true, and it operates on the basis of a Cesium 133 atomic source 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. A photo of this device has spread throughout the world.

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

BathysHawaii's clocks were truly the first atomic ones. wristwatch. Previously, there were already known cases of the release of a relatively portable device, but, unfortunately, it did not have an atomic power source, but only synchronized with a real dimensional clock via wireless radio. It is also worth mentioning the cost of such a gadget. The pleasure was valued at 12 thousand US dollars. It was clear that at such a price the watch would not gain wide popularity, but the company did not strive for this, because it released it 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 the means of finding changes and their elements. The following types of watches can be distinguished:

Hydrogen. Their essence lies in the fact that hydrogen atoms are supported at the required energy level, 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.
Cesium. They are based on cesium beams. It is worth noting that these watches are the most accurate.
Rubidium. They are the simplest and very compact.

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

The company did not stop there, and in its tenth version of the watch it wants to use 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 this version of the case, but the estimated retail price of this masterpiece is already known - it was 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 can we talk about atomic clocks without mentioning the most interesting facts, which are associated with them and time in general:

Did you know that the oldest sundial was found in ancient Egypt?
The error of atomic clocks is minimal - it is only 1 second per 6 million years.
Everyone knows that there are 60 seconds in a minute. But few people delved into how many milliseconds are in one second? And there are not many and not few of them - a thousand!
Every tourist who was able to visit London always wanted to see Big Ben with his 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.
Have you ever wondered why the hands of our clocks go from left to right or, as we used to say, “clockwise”? This fact is directly related to the way the shadow moves on a sundial.
The very first wristwatches were invented back in 1812. They were made by the founder of Breguet for the Queen of Neapolitan.
Before the First World War, wristwatches were considered only a women's accessory, but soon, due to their convenience, they were also chosen by the male part of the population.

Atomic clock January 27th, 2016

The birthplace of the world's first pocket watch with a built-in atomic time standard will not be Switzerland or even Japan. The idea of their creation originated in the heart of Great Britain at the London brand Hoptroff

Atomic clocks, or as they are also called “quantum clocks,” are a device that measures time using natural vibrations associated with processes occurring at the level of atoms or molecules. Richard Hoptroff decided that it was time for modern gentlemen who are interested in ultra-technological devices to exchange their mechanical pocket watches for something more extravagant and unconventional, and also in line with modern urban trends.

Thus, the public were shown elegant in their own way appearance pocket atomic clock Hoptroff No. 10, which can surprise the modern generation, sophisticated with an abundance of gadgets, not only with its retro style and fantastic accuracy, but also with its service life. According to the developers, having this watch with you, you can remain the most punctual person for at least 5 billion years.

What else can you find out interesting about them...

Photo 2.

For all those who have never been interested in such watches, it is worth briefly explaining the principle of their operation. There is nothing inside the “atomic device” that resembles a classic mechanical watch. In Hoptroff no. 10 there are no mechanical parts as such. Instead, atomic pocket watches are equipped with a sealed chamber filled with a radioactive gas, the temperature of which is controlled by a special furnace. Accurate timekeeping occurs as follows: lasers excite the atoms of a chemical element, which is a kind of “filler” of the clock, and the resonator records and measures each atomic transition. Today, the basic element of such devices is cesium. If we recall the SI system of units, then in it the value of a second is related to the number of periods of electromagnetic radiation during the transition of cesium-133 atoms from one energy level to another.

Photo 3.

If in smartphones the heart of the device is considered to be a processor chip, then in Hoptroff No. 10 this role is taken on by the reference time generator module. It is supplied by Symmetricom, and the chip itself was initially intended for use in the military industry - in unmanned aerial vehicles.

The CSAC atomic clock is equipped with a temperature-controlled thermostat, which contains a chamber containing cesium vapor. Under the influence of a laser on cesium-133 atoms, their transition from one energy state to another begins, which is measured using a microwave resonator. Since 1967 International system units (SI) defines one second as 9,192,631,770 periods of electromagnetic radiation arising during the transition between two hyperfine levels of the ground state of the cesium-133 atom. Based on this, it is difficult to imagine a more technically accurate cesium-based watch. Over time, given the latest advances in time measurement, the accuracy of new optical clock based on an aluminum ion pulsating at a frequency of ultraviolet radiation (100,000 times higher than the microwave frequencies of cesium clocks), it will hundreds of times exceed the accuracy of atomic chronometers. To put it simply, Hoptroff's new pocket model No.10 has a running error of 0.0015 seconds per year, which is 2.4 million times higher than COSC standards.

Photo 4.

The functional side of the device is also on the verge of fantasy. With its help you can find out: time, date, day of the week, year, latitude and longitude in different quantities, pressure, humidity, sidereal hours and minutes, tide forecast and many other indicators. The watch comes in gold, and the case is made from precious metal It is planned to use 3D printing.

Richard Hoptrof sincerely believes that this particular option for producing his brainchild is the most preferable. To slightly change the design component of the structure, it will not be necessary to rebuild the production line at all, but to use the functional flexibility of the 3D printing device for this. However, it is worth noting that the prototype of the watch shown was made in the classical way.

Photo 5.

Time is very expensive these days, and the Hoptroff No. 10 is a direct confirmation of this. According to preliminary information, the first batch of atomic devices will be 12 units, and as for the cost, the price for 1 copy will be $78,000.

Photo 6.

According to Richard Hoptroff, managing director of the brand, Hoptroff's London location played a key role in the emergence of this idea. “In our quartz movements we use a high-precision oscillating system with a GPS signal. But in the center of London it is not so easy to catch this very signal. One day, during a trip to the Greenwich Observatory, I saw a Hewlett Packard atomic clock there and decided to purchase something similar for myself via the Internet. And I couldn't. Instead, I came across information about a chip from Symmetricon, and after three days of thinking, I realized that it would be perfect for a pocket watch.”

The chip in question is the SA.45s cesium atomic clock (CSAC), one of the first generation of miniature atomic clocks for GPS receivers, backpack radios and unmanned vehicles. Despite its modest dimensions (40 mm x 34.75 mm), it is still unlikely to fit into a wristwatch. Therefore, Hoptroff decided to equip a pocket model with them of rather respectable dimensions (82 mm in diameter).

In addition to being the world's most accurate watch, the Hoptroff No 10 (the brand's tenth movement) also claims to be the first gold case made using 3D printing technology. Hoptroff cannot yet say with certainty how much gold will be required to make the case (work on the first prototype was completed when the issue went to press), but estimates that its cost will be “at least several thousand pounds.” And considering all that volume scientific research, required to develop the product (take, for example, the function of calculating the ebb and flow of tides using harmonic constants for 3 thousand different ports), we can expect its final retail price to be about 50 thousand pounds sterling.

Gold body of model No. 10 as it comes out of the 3D printer and in finished form

Buyers automatically become members of an exclusive club and will be required to sign a written pledge not to use the atomic clock chip as a weapon. “This is one of the conditions of our contract with the supplier,” explains Mr. Hoptroff, “since the atomic chip was originally used in missile guidance systems.” Not much to pay for the opportunity to have a watch with impeccable accuracy.

The lucky owners of the No.10 from Hoptroff will have much more at their disposal than just a high-precision watch. The model also functions as a pocket navigation device, allowing one to determine longitude with an accuracy of one nautical mile, even after many years at sea, using a simple sextant. The model will receive two dials, but the design of one of them is still kept secret. The other is a whirlwind of counters displaying as many as 28 complications: from all possible chronometric functions and calendar indicators to a compass, thermometer, hygrometer (a device for measuring humidity levels), barometer, latitude and longitude counters and a high/low tide indicator. And this is not to mention the vital indicators of the state of the atomic thermostat.

Hoptroff has plans to produce a number of new products, including electronic version George Daniels' legendary Space Traveler complication watch. It is currently being worked on to integrate Bluetooth technology into the watch to store the wearer's personal information and enable automatic adjustment of complications such as the moon phase indicator.

The first copies of No.10 will appear in next year, in the meantime, the company is looking for suitable partners among retailers. “We could, of course, try to sell it online, but this is a premium model, so you still need to hold it in your hands to really appreciate it. This means that we will still have to use the services of retailers, and we are ready to start negotiations,” says Mr. Hoptroff in conclusion.

And even The original article is on the website InfoGlaz.rf Link to the article from which this copy was made -