The most powerful magnet in the world: Tesla.

Ultra-low temperatures are required to create ultra-powerful magnetic fields

Bird's eye view of Experiment Control Center

Experimental Control Center at NHMFL Laboratory

So far, only ten such stars have been discovered. The field strength of this star is 100 billion Tesla (in international system units, magnetic field is measured in tesla). For comparison, the Earth has only 0.00005 Tesla. It is unlikely that we will ever create a magnet of comparable power to a magnetar. But that doesn't mean we don't try. The reasons why scientists persist in building more and more powerful magnets range from “what if?” to the real need to improve medical projection equipment.

The record so far belongs to specialists from the National High Magnetic Field Laboratory (NHMFL), located in Tallahassee (Florida). In December 1999, they launched a hybrid magnet. It weighs 34 tons, is almost 7 meters high, and can create a magnetic field of 45 Tesla, which is about a million times stronger than that of Earth. This is already enough for the properties of ordinary electronic and magnetic materials to change significantly.

This magnet, developed by NHMFL, represents a very important milestone in the construction of the ISS, says laboratory director Jack Crow.

This is not a horseshoe for you

If you imagined a giant horseshoe, you will be disappointed. The Florida magnet (see photo above) is actually two working in a system. The outer layer is a super-cooled, superconducting magnet. It is the largest of its kind ever created. It is constantly cooled to a temperature close to absolute zero. For this purpose, a system with superfluid helium is used - the only one in the United States specifically designed to cool this magnet. And in the center of the contraption is a massive electromagnet, that is, a very large resistive magnet.

Despite the gigantic size of the system built at NHMFL, the experimental site is extremely small. Experiments are usually carried out on objects no larger than the tip of a pencil. In this case, the sample is placed in a bottle, like a thermos, to keep the temperature low.

When materials are exposed to ultra-high magnetic fields, very strange things begin to happen to them. For example, electrons “dance” in their orbits. And when the tension magnetic field exceeds 35 T, the properties of materials become uncertain. For example, semiconductors can change properties back and forth: at one moment they conduct current, at another - not.

Crowe says the Florida magnet's power will be gradually increased over five years to 47, then 48 and eventually 50 Tesla, and the research results have already exceeded his wildest expectations: “We got everything we hoped for and much more. Our colleagues are now overwhelming us with requests to give them the opportunity to experiment too.”

Application in medicine

While NHMFL concentrates its efforts on pure research, much of the development in the field of high-power magnets is driven by the need to develop medical technology. The Florida State University Brain Institute claims to have the largest magnet ever used in tomography. This 24-ton behemoth can detect a long list of diseases and defects in the brain and spine. Its power is 11.7 Tesla, which is 234 thousand times more than that of the Earth.

The stronger the magnetic field, the more accurate and detailed the results that can be obtained using technologies like nuclear magnetic resonance(NMR). One current project aims to show the effects of paralysis and the drugs used to treat it on brain cells. A functional nuclear magnetic resonance (fNMR) study will show exactly how much of the drug was consumed by which cells.

NMR and fNMR technologies work like this. First, with the help of a powerful magnetic field, the cell nuclei line up like the needles of a compass. A less powerful magnet then turns the nuclei. This produces a measurable signal, which is recorded and converted into a three-dimensional image using computers. The more powerful the magnets, the more cores will respond to the signal. Unlike X-rays, which show bones and hard tissue, NMR focuses on soft tissue.

The increasing use of magnets in medicine raises a natural question: is it useful? IN last years There has been much debate about the impact of nearby power lines on people and animals. But because the strength of the magnetic field drops so quickly, a person living just 15 meters from a power line receives only two milligauss (mG). Recent studies support the version that it has no effect on humans.

On the other hand, absolutely no positive effects have been found from “body” magnets, which are often sold as a universal remedy for all diseases, including arthritis. But this does not stop millions of people around the globe.

To create magnetic devices, scientists once used different materials, including even such exotic ones as platinum. However, the power of a neodymium magnet left much to be desired until 1982, when the amazing properties of neodymium were discovered and applied. Only a few decades have passed since then, but we can already say that this rare earth element has literally exploded technological processes different industries. The breakthrough was achieved thanks to several advantages of the alloy.

Characteristics of magnetic products

Firstly, today we can say with complete confidence that from the entire family similar devices the most powerful are neodymium magnets. Secondly, fantastic adhesion power is far from the only advantage of this kind of product. Just look at their famous resistance to demagnetization. While ferrite analogues almost completely lose their characteristics over 20-30 years, neodymium becomes weaker by only a couple of percent. This means that its service life is practically unlimited. Everyone who was lucky enough to buy powerful neodymium magnets was able to verify their impressive characteristics.

Among other things, the adhesion force of magnetic products is seriously affected by its weight and size parameters. In other words, the more massive the product, the great strength will be required to tear it off the iron surface. Not everyone can detach even a 50x30 disk, which weighs less than half a kilogram, from a steel plate, because this will require an effort comparable to lifting 116 kg. Therefore, anyone who decides to buy a large neodymium magnet should remember the precautions when handling it. Try to store neodymium items away from massive iron objects, do not give them to children, and do not subject them to rough mechanical impact - the material is quite fragile.

You can find magnets from a couple of grams to several kilograms and a clutch of several centners in the catalog on the website.

Magnetic storms are not usually considered to be a formidable natural phenomenon, such as earthquakes, tsunamis, or typhoons. True, they disrupt radio communications in the high latitudes of the planet and make compass needles dance. Now these interferences are no longer scary. Long-distance communications are increasingly carried out via satellites, and with their help, navigators set the course for ships and aircraft.

It would seem that the vagaries of the magnetic field may no longer bother anyone. But it is now that some facts have given rise to fears that changes in the Earth’s magnetic field can cause catastrophes that will make the most formidable forces of nature pale in comparison!

One of these field changes is happening today... Since the German mathematician and physicist Carl Gauss first gave mathematical description magnetic field, subsequent measurements - over 150 years before today— show that the Earth's magnetic field is steadily weakening.

In this regard, the questions seem natural: will the magnetic field disappear completely, and how can this threaten earthlings?

Let us remember that our planet is constantly bombarded by cosmic particles, especially intensely by protons and electrons emitted by the Sun, the so-called solar wind. They rush past the Earth at an average speed of 400 km/s. The Earth's magnetosphere does not allow charged particles to reach the surface of the planet. She directs them to the poles, where they give birth to fantastic lights in the upper atmosphere. But if there is no magnetic field, if plant and animal world finds itself under such continuous fire, we can assume that radiation damage to organisms will have the most disastrous effect on the fate of the entire biosphere.

To judge how real such a threat is, we need to remember how the Earth’s magnetic field arises and whether there are any unreliable links in this mechanism that can fail.

According to modern concepts, the core of our planet consists of a solid part and a liquid shell. Heated by the solid core and cooled by the mantle located above, the liquid substance of the core is drawn into the circulation, into convection, which breaks up into many separate circulating flows.

The same phenomenon is familiar to the Earth's oceans, when deep heat sources are close to the ocean floor, causing it to warm up. Then vertical currents arise in the water column. For example, such a current in the Pacific Ocean off the coast of Peru has been well studied. It carries a huge amount of nutrients from the depths to the surface of the water, making this area of ​​the ocean especially rich in fish...

The substance of the liquid part of the core is a melt with a high content of metals, and therefore it has good electrical conductivity. From the school course we know that if a conductor moves in a magnetic field, crossing its lines, then an electromotive force is excited in it.

A weak interplanetary magnetic field could initially interact with the melt flows. The current generated by this, in turn, created a powerful magnetic field that surrounded the planet's core in rings.

In the depths of the Earth, in principle, everything happens as in a self-excited dynamo, a schematic model of which is usually available in every school physics classroom. The difference is that instead of wires in the depths there are flows of liquid electrically conductive material. And, apparently, the analogy between the sections of the dynamo rotor and the convection flows of the melt in the bowels is quite legitimate. The mechanism that creates the Earth's magnetic field is therefore called a hydromagnetic dynamo.

But the picture, of course, is more complicated: ring fields, otherwise called toroidal, do not reach the surface of the planet. Interacting with the same electrically conductive moving liquid mass, they generate another, external field, which we deal with on the surface of the Earth.

Our planet with its external magnetic field is usually schematically depicted as a symmetrically magnetized ball with two poles. In reality, the external field is not so ideal in shape. Symmetry is broken by many magnetic anomalies.

Some of them are very significant and are called continental. One such anomaly is in Eastern Siberia, the other - in South America. Such anomalies arise because the hydromagnetic dynamo in the bowels of the Earth is not “designed” as symmetrically as electric cars, built in a factory, where they ensure the alignment of the rotor and stator and carefully balance the rotors on special machines, ensuring that their centers of mass (more precisely, the main central axis of inertia) coincide with the axis of rotation. And the power of matter flows, and temperature conditions, on which the speed of their movement depends, are far from the same in different zones of the earth's interior, where the natural dynamo operates. Most likely, a deep dynamo can be compared to a machine in which sections in the rotor winding are of different thicknesses and the gap between the rotor and stator varies.

Anomalies of a smaller scale - regional and local - are explained by the peculiarities of the composition of the earth's crust - such as, for example, the Kursk magnetic anomaly, which arose due to giant deposits of iron ore.

In a word, the mechanism that generates the Earth’s magnetic field is stable, reliable, and it seems there are no parts in it that can suddenly fail. Moreover, according to Professor of the University of Munich G. Zoffel, electrical conductivity liquid material in the depths is so great that if for some reason the hydromagnetic dynamo suddenly “turns off,” the magnetic forces on the surface of the planet will signal us about this only after many millennia.

But the “breakdown” of a natural mechanism is one thing, the gradual attenuation of its action, similar to the cold snaps that gave rise to glaciations of the planet, is another thing.

To analyze this circumstance, we will need a more detailed acquaintance with the behavior of the magnetic field: how and why it changes over time.

Any rock, any substance containing iron or other ferromagnetic element is always under the influence of the Earth's magnetic field. Elementary magnets in this material tend to orient themselves like a compass needle along the field lines.

However, if the material is heated, there will come a point when the thermal motion of the particles becomes so energetic that it destroys the magnetic order. Then, when our material cools, starting from certain temperature(it is called the Curie point) the magnetic field will prevail over the forces of chaotic motion. The elementary magnets will again line up as the field tells them, and will remain in this position if the body is not heated again. The field appears to be “frozen” in the material.

This phenomenon allows us to confidently judge the past of the earth's magnetic field. Scientists are able to penetrate into such distant times when the solid crust was cooling on the young planet. Minerals preserved from that time tell about what the magnetic field was like two billion years ago.

When it comes to studying periods much closer to us in time - within the last 10 thousand years - scientists prefer to take materials of artificial origin for analysis, rather than natural lavas or sediments. This is clay baked by humans - dishes, bricks, ritual figurines, etc., which appeared with the first steps of civilization. Advantage artificial crafts made of clay is that archaeologists can date them quite accurately.

At the Institute of Earth Physics of the Russian Academy of Sciences, the laboratory of archaeomagnetism was studying changes in the magnetic field. There was concentrated extensive data obtained in the laboratory and in leading foreign scientific centers. Russian scientists are also doing this.

Indeed, these data confirm that in our time the magnetic field is weakening. But a caveat is necessary here: precise measurements of the field’s behavior over long periods of time indicate that the planet’s magnetic field is subject to numerous oscillations with different periods. If we add them all up, we get the so-called “smoothed curve”, which coincides quite well with a sinusoid having a period of 8 thousand years.

At this time, the total value of the magnetic field is on the descending segment of the sinusoid. This is what caused concern among some authors. Behind more high values, further weakening of the field is ahead. It will continue for about another two thousand years. But then the field will begin to strengthen. This phase will last 4 thousand years, and then decline again. The previous maximum occurred at the beginning of our era. The multiplicity of magnetic field oscillations is apparently explained by the lack of balance in the moving parts of the hydromagnetic dynamo and their different electrical conductivities.

It is important to note that the amplitude of the sine wave is less than half average size field strength. In other words, these fluctuations cannot in any way reduce the field value to zero. This is the answer to those who believe that the current weakening of the field will eventually reveal the surface globe for firing particles from space.

As already mentioned, the curve is the sum of various overlapping oscillations of the Earth’s magnetic field - about a dozen of them have been identified so far. Well-defined periods have a duration of 8000, 2700, 1800, 1200, 600 and 360 years. The periods of 5400, 3600 and 900 years are less clearly visible.

Some of these periods are associated with significant phenomena in the life of the planet.

A period of 8000 years has an undoubtedly global scale, in contrast to fluctuations, for example, of 600 or 360 years, which have a regional, local character.

Interesting relationships with many natural phenomena of the period of 1800 years. Geographer A.V. Shnitnikov made a comparison of various natural rhythms of the Earth and discovered their connection to the astronomical phenomenon named. Big sares, when the Sun, Earth and Moon are on the same straight line and at the same time the Earth is located at the shortest distance from both the luminary and the satellite. In this case they reach highest value tidal forces. The Great Sares repeats itself every 1800 years (with deviations) and is accompanied by the expansion of the globe in the equatorial zone - due to a tidal wave in which the World Ocean and Earth's crust. As a consequence of this, the moment of inertia of the planet changes, and it slows down its rotation. The position of the polar ice boundary is also changing, and the ocean level is rising. Great Sares affects the Earth's climate - dry and wet periods begin to alternate differently. Such changes in nature in the past were reflected in the planet’s population: for example, the migration of peoples increased...

The Institute of Physics of the Earth set out to find out whether there were connections between the phenomena caused by the Great Sares and the behavior of the magnetic field. It turned out that the 1800-year period of field oscillations is in good agreement with the rhythm of phenomena caused by the relative positions of the Sun, Earth and Moon. The beginnings and ends of the changes and their maxima coincide... This can be explained by the fact that in the liquid mass surrounding the planet’s core, during the Great Sares, the tidal wave also reached its greatest value, therefore, the interaction of matter flows with the internal field also changed.

In the last 10 thousand years earthly nature did not suffer any disasters due to the restless magnetic field. But what does the deeper past hide? As is known, the most dramatic events in the Earth's biosphere lie far beyond 10 thousand years. Maybe they were caused by some changes in the magnetic field?

Here we will have to deal with a fact that has alarmed some scientists.

The magnetic fields of the past turned out to be “frozen” into volcanic lavas when they cooled and passed the Curie point. Magnetic fields are also imprinted in bottom sediments: particles sinking to the bottom, if they contain ferromagnets, are oriented along the lines of the magnetic field, like compass needles. It is preserved forever in fossilized sediments, unless the sediments are subjected to strong heating...

Palaeomagnetologists study ancient magnetic fields. They were able to discover truly enormous changes that the magnetic field underwent in the distant past. The phenomenon of inversion - a change in magnetic poles - was discovered. The northern one moved to the place of the southern one, the southern one to the place of the northern one.

By the way, the poles do not change so quickly - according to some estimates, the change lasts 5 or even 10 thousand years.

The last such movement occurred 700 thousand years ago. The previous one is another 96 thousand years earlier. There are hundreds of such shifts in the history of the planet. No regularity was found here - long quiet periods are known, they were replaced by times of frequent inversions.

The so-called “excursions” were also discovered - the departure of the magnetic poles from the geographic ones over long distances, ending, however, with a return to their previous place.

Many have tried to explain the polarity reversals. American scientists R. Muller and D. Morris, for example, believe that the primary cause of this was the impact of giant meteorites. The “shake-up” of the planet forced a change in the nature of the movement of melts in its depths. The authors of this hypothesis were based on the fact that 65 million years ago, the inversion and fall of a large cosmic body to Earth simultaneously occurred, as evidenced by sediments of that time, rich in cosmic iridium. The hypothesis looked impressive, but was unconvincing, if only because the temporal connection between these events was very weakly proven. Another hypothesis is that inversions are triggered by deep melt flows when giant lumps of ferromagnetic material fall into them. These lumps, concentrating the lines of the magnetic field in themselves, seem to “pull” it along with them.

And this hypothesis is controversial.

Obviously, over the billions of years of its existence, the Earth's core must have increased in size. It would seem that this could not but affect the Earth's magnetic field. Meanwhile, scientists who have information about what the planet’s magnetic field was like two billion years ago compare these data with today’s data and do not even find traces of the influence of core growth on the magnetic field. Could a phenomenon of a much more modest scale, such as the hypothetical “clumps” represent, affect the state of the field?

The currently accepted theory of the hydromagnetic dynamo is capable of explaining the inversion, but this theory does not say that a change of poles is obligatory, it just does not contradict this phenomenon.

The reason for the inversions are the same “constructive imperfections” of the natural hydromagnetic dynamo. But these are different defects than those that cause the already familiar spectrum of ten oscillations of the magnetic field, oscillations that monotonously repeat themselves after certain periods of time. Inversions do not have such a regular, systematic character.

One might believe that the phenomenon of inversion, the search for its causes and its consequences will arouse the interest only of researchers of terrestrial magnetism. But no, this phenomenon has attracted the attention of a wide range of scientists, including those who study the development of the earth’s biosphere.

IN Lately in several scientific articles It has been suggested that during reversals the Earth's magnetic field disappears. Thus, we are talking about the planet losing its invisible armor for some time. And this, apparently, can lead to the death of many species of plants and animals. That is why in the changes to which the magnetic field is subject, some see a danger more formidable than that posed by the destructive trio: earthquakes, tsunamis, typhoons.

The authors of this assumption, as proof of their correctness, cite the relationship between the extinction of dinosaurs, which disappeared from the face of the Earth 65 million years ago, and the frequent inversions characteristic of that period.

The hypothesis about such a radical influence of polar reversals on the development of all living nature on Earth was met with particular satisfaction by evolutionists, who in the recent past used a computer to simulate the history of the biosphere of our planet, starting from primary forms living matter. The program included all the factors known at that time that influenced mutations and natural selection. The results of the study were unexpected: evolution from the first cell to man in the mathematical interpretation was much slower than in real conditions of earthly nature.

Obviously, the scientists concluded, the program did not take into account some energetic factors that force nature to simultaneously change species. Now, they believe, one of such strong accelerators of evolution has been found - this is the effect on organic world cosmic radiation during those periods when the poles swapped places... Something similar, at least, to the Chernobyl disaster.

Against this background, the assertion of American geophysicists sounds either alarming or reassuring that they discovered layers of lava in Oregon, which show that the field “frozen” in them has rotated 90 degrees in just two weeks. In other words, change does not necessarily require thousands of years, but can be almost instantaneous. That is, the time of the destructive effects of cosmic radiation is short, which reduces their danger. It is not clear why the field rotated not 180 degrees, but only 90.

However, the assumption that during polarity reversals the magnetic field disappears is just an assumption, and not the truth, based on reliable facts. On the contrary, some paleomagnetic studies suggest that the field is preserved during reversals. It, however, does not have a dipole structure and is much weaker - 10, and even 20 times. The interpretation of sudden field changes found in lavas from Oregon has raised serious objections. Professor G. Zoffel, whom we mentioned, believes that the discovery of American colleagues can be explained in a completely different way, for example, this way: a magnetic field generated by lightning that struck at that moment was “frozen” into the cooling lava.

But these objections do not exclude the possibility of a direct, perhaps weakened, impact of cosmic particles on the flora and fauna. Many scientists have joined in the search for answers to the questions posed by this hypothesis.

Noteworthy are the considerations expressed at one time by V.P. Shcherbakov, an employee of the Institute of Earth Physics of the USSR Academy of Sciences. He believed that during reversals, the planet’s magnetic field, albeit weakened, retains its structure, in particular, magnetic power lines in the region of the poles they still rest against the surface of the planet. Above the moving poles during periods of inversion in the magnetosphere, there are constantly, as in our days, funnels into which cosmic particles seem to be poured.

During periods of inversions, with a weakened field, they can fly up to the surface of the green ball at the closest distances, and perhaps even reach it.

Paleontologists also joined the search. For example, the German professor G. Herm, who, in collaboration with many foreign laboratories, studied bottom sediments dating back to the end of the Cretaceous period. He found evidence that during these times there was a leap in the development of species. However, this scientist considers the inversions of that time to be just one of the factors that pushed evolution. G. Herm does not find any reason to worry about future life on the planet if sudden changes occur in the magnetic field.

Moscow State University Professor B. M. Mednikov, an evolutionary biologist, also does not consider them dangerous and explains why. The main protection from the solar wind, he says, is not the magnetic field, but the atmosphere. Protons and electrons lose their energy in its upper layers above the poles of the planet, causing air molecules to glow, “shine.” If suddenly the magnetic field disappears, then the aurora will probably be not only above the poles, where the magnetosphere now drives particles, but throughout the entire sky - but on the same high altitudes. The solar wind will still remain safe for living things.

B. M. Mednikov also says that evolution does not need “spurring” cosmic forces. The latest, more advanced computer models of evolution convince: its real speed is fully explained by molecular reasons internal to the body. When, at the birth of a new organism, its apparatus of heredity is created, in one out of a hundred thousand cases the copying of parental characteristics occurs with an error. This is quite enough for animal and plant species to keep up with changes in environment. We should not forget about the mechanism of mass spread of gene mutations through viruses.

According to magnetologists, B. M. Mednikov’s objections cannot erase the problem. If the direct influence of changes in the magnetic field on the biosphere is unlikely, then there is also an indirect one. There are, for example, undoubted relationships between the planet’s magnetic field and its climate...

As you can see, there are many serious contradictions in the problem of the relationship between the magnetic field and the biosphere. Contradictions, as always, motivate researchers to search.

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Are the most powerful thunderstorms inside the earth?The most unpredictable processes

Magnetic force is the most important property of a magnet. It is on this indicator that it depends performance and scope of application. The strength of magnets is measured in units of tesla (T). That is, to find out which magnet is the most powerful, you need to make a comparison various materials according to this indicator.

The most powerful electromagnet

Scientists in different countries They are trying to create the most powerful magnet in the world and sometimes achieve very interesting results. Today, the status of the strongest electromagnet is held by the installation at the Los Alamos National Laboratory (USA). A giant device with seven sets of coils total mass 8.2 tons produces a magnetic field with a power of 100 Tesla. This impressive figure is 2 million times the strength of our planet's magnetic field.

It is worth noting that the solenoid of the record-breaking magnet is made from a Russian copper-niobium nanocomposite. This material was developed by scientists from the Kurchatov Institute with the assistance of the All-Russian Research Institute of Inorganic Materials named after. A. A. Bochvara. Without this ultra-strong composite, the new most powerful magnet in the world would not have been able to surpass the record of its predecessor, since the main technical difficulty when operating installations of this level is maintaining integrity when exposed to the strongest magnetic pulses. The maximum recorded field strength of the electromagnet, which was destroyed by pulses during the experiment, was 730 Tesla. In the USSR, scientists, using a magnet of a special design and explosives, managed to create an impulse of 2800 Tesla.

copper-niobium

The magnetic pulses obtained in laboratories are millions of times greater than the Earth's magnetic field. But even the most powerful magnet that has been built to date is millions of times weaker neutron stars. Magnetar SGR 1806−20 has a magnetic field of 100 billion Tesla.

The strongest magnet for household use

Of course, the magnetic force of stars and the experiments of scientists are interesting, but most users want to know which magnet is the most powerful for solving specific application problems. To do this, you need to compare the strength of the magnetic field various types magnets:

1) Ferrite magnets– 0.1..0.2 T.

2) Alnico and samarium magnets– 0.4..0.5 T.

3) Neodymium magnets– up to 2 Tesla (when folded into a Habalt structure).

So, the most powerful magnet is rare earth super magnet, small powerful magnet, the main components of which are neodymium, iron and boron. The strength of its field is comparable to the power of electromagnets with a ferrite core. The neodymium-based magnetic alloy boasts unsurpassed performance in the following important parameters:

1) Coercive force. This property allows the material to be used in areas exposed to external magnetic fields.

2) Breakout force. Thanks to the maximum magnetic force, it is possible to reduce the size of products while maintaining high adhesion power.

3) Residual magnetic induction. A high level of residual magnetization provides a very important property of a neodymium magnet - the duration of retention of magnetic qualities. Essentially, losing only a few percent of its strength over a century, the magnetic alloy neodymium-iron-boron is an eternal magnet.

To maintain the strong magnetic field of a neodymium-based rare earth supermagnet, you should be aware of its weak points. In particular, the material has a powder structure, therefore strong blows and falls can lead to loss of its properties. Also, the alloy is demagnetized when heated to +70 ⁰ C (heat-resistant versions of the alloys can withstand up to +200 ⁰ C). Just take these features into account and then the products will benefit you for as long as possible.