Of two protons and two neutrons. Protons and neutrons: pandemonium inside matter. Why all this is interesting to physicists

First of all, you need to understand that there are four separate types of energy released:

1) chemical energy that powers our cars, as well as most of the devices of modern civilization;

2) nuclear fission energy, used to generate about 15% of the electricity we consume;

3) the energy of hot nuclear fusion, which powers the sun and most stars;

4) the energy of cold nuclear fusion, which is observed by some experimenters in laboratory studies and the existence of which is rejected by most scientists.

The amount of nuclear energy released (heat/pound of fuel) of all three types is 10 million times greater than that of chemical energy. How are these types of energy different? In order to understand this issue, some knowledge in the field of chemistry and physics is required.

Using the offers of this online store selling goods for the home, you can easily buy any goods at affordable prices.

Nature has given us two kinds of stably charged particles: protons and electrons. A proton is a heavy, usually very small, positively charged particle. The electron is usually light, large, with fuzzy boundaries and has a negative charge. Positive and negative charges attract each other, just as the north pole of a magnet attracts the south pole. If a magnet is brought with its north pole to the south pole of another magnet, they will collide. The collision will release a small amount of energy in the form of heat, but it is too small to be easily measured. To separate the magnets, you have to do work, that is, expend energy. This is about the same as lifting a stone back up the hill.

When a stone rolls down a hill, a small amount of heat is released, but the process of lifting the stone back up requires energy.

In the same way, the positive charge of the proton collides with the negative charge of the electron, they "stick together", releasing energy. The result is a hydrogen atom, referred to as H. A hydrogen atom is nothing more than a blurry electron enveloping a small proton. If you knock out an electron from a hydrogen atom, you get a positively charged H + ion, which is nothing more than the original proton. "Ion" is the name applied to an atom or molecule that has lost or gained one or more electrons and is therefore no longer neutral.

As you know, in nature there is more than one kind of atoms. We have oxygen atoms, nitrogen atoms, iron atoms, helium atoms and others. How are they all different? They all have different types of nuclei, and all nuclei contain a different number of protons, which means they have a different positive charge. A helium nucleus contains 2 protons, which means it has a plus 2 charge, and it takes 2 electrons to neutralize the charge. When 2 electrons are “glued” to it, a helium atom is formed. The oxygen nucleus contains 8 protons and has a charge of 8. When 8 electrons are "glued" to it, an oxygen atom is formed. A nitrogen atom has 7 electrons, an iron atom has about 26. However, the structure of all atoms is approximately the same: a small, positively charged nucleus, located in a cloud of diffuse electrons. The difference in size between the nucleus and electrons is huge.

The diameter of the Sun is only 100 times the diameter of the Earth. The diameter of the electron cloud in an atom is 100,000 times the diameter of the nucleus. In order to get the difference in volumes, it is necessary to raise these numbers to a cube.

Now we are ready to understand what chemical energy is. Atoms, being electrically neutral, can actually bond with each other, releasing more energy. In other words, they can be combined into more stable configurations. Already in the atom, the electrons try to distribute themselves in such a way as to get as close as possible to the nucleus, but due to their fuzzy nature, they require a certain amount of space. However, when combined with the electrons of another atom, they usually form a closer configuration, which allows them to approach the nuclei. For example, 2 hydrogen atoms can combine into a more compact configuration if each hydrogen atom donates its electron to a cloud of 2 electrons, which is divided between two protons.

Thus, they form a group consisting of two electrons in a single cloud and two protons separated from each other by space, but, nevertheless, located inside the cloud of electrons. As a result, a chemical reaction occurs that proceeds with the release of heat: H + H => H G (The sign “=>” means “goes into” or “becomes”). The H 2 configuration is a hydrogen molecule; when you buy a balloon of hydrogen, you get nothing more than H molecules. Moreover, when combined, two H 2 electrons and 8 O atom electrons can form an even more compact configuration - a water molecule H O plus heat. In fact, a water molecule is a single cloud of electrons, inside of which there are three point nuclei. Such a molecule is the minimum energy configuration.

Thus, by burning oil or coal, we redistribute electrons. This leads to the formation of more stable configurations of point nuclei inside electron clouds and is accompanied by heat release. This is the nature of chemical energy.

In the previous discussion, we missed one point. Why do nuclei in nature initially contain two or more protons? Each proton has a positive charge, and when the distance between the positive charges is so small that it is commensurate with the space surrounding the nucleus, they strongly repel each other. The repulsion of like charges is similar to the repulsion that occurs between the north poles of two magnets when they are trying to connect them incorrectly. There must be something that overcomes this repulsion, otherwise only hydrogen atoms would exist. Fortunately, we see that this is not the case.

There is another type of force that acts on the proton. This is nuclear power. Due to the fact that it is very large, the particles are firmly held almost on top of each other. In addition, there is a second type of heavy particles, which differ from the proton only in that they have neither a positive nor a negative charge. They are not repelled by the positive charge of the proton. These particles are called "neutrons" because they are electrically neutral. The peculiarity is that the unchanged state of the particles is possible only inside the nucleus. When a particle is outside the nucleus, within about 10 minutes it turns into a proton, an electron, and a very light antineutrino. However, inside the nucleus, it can remain unchanged for an arbitrarily long time. Be that as it may, the neutron and the proton are very strongly attracted to each other. Having approached at a sufficient distance, they connect, forming a very strong pair, the so-called deuteron, which is denoted by D +. A single deuteron combines with a single electron to form a heavy hydrogen atom, or deuterium, denoted D.

The second nuclear reaction occurs when two deuterons interact. When two deuterons are forced to interact, they combine to form a particle that has a double charge. A grouping of two protons and two neutrons is even more stable than a proton-neutron grouping in a deuteron. The new particle, neutralized by 2 electrons, becomes the nucleus of a helium atom, which is designated He. In nature, there are also large groups that are the nuclei of carbon, nitrogen, oxygen, iron and other atoms. The existence of all these groupings is possible due to the nuclear force that arises between particles when they interact with each other or share a total volume of space equal to the size of the nucleus.

Now we can understand the nature of ordinary nuclear energy, which is actually nuclear fission energy. During the early history of the universe, massive stars formed. During the explosion of such massive stars, nuclei of many types were formed and again burst into outer space. Planets and stars, including the Sun, formed from this mass.

It is possible that during the explosion all possible stable configurations of protons and neutrons appeared, as well as such practically stable groups as the uranium nucleus. In fact, there are three types of uranium nuclei: uranium-234, uranium-235 and uranium-238. These "isotopes" differ in the number of neutrons, however, they all contain 92 protons. Nuclei of any type of uranium atom can change into lower energy configurations by ejecting helium nuclei, however, this process is so rare that terrestrial uranium retains its properties for about 4 billion years.

However, there is another way to break the configuration of the uranium nucleus. In general terms, proton and neutron clusters are most stable if they contain about 60 proton-neutron pairs. The number of such pairs contained in the nucleus of uranium is three times higher than this figure. As a result, it tends to split into two parts, while releasing a large amount of heat. However, nature does not allow it to separate. In order to do this, it first needs to move into a higher energy configuration. However, one type of uranium, uranium-235, designated 235 U, gets the energy it needs by capturing a neutron. Having thus obtained the necessary energy, the nucleus decays, releasing a huge amount of energy and releasing additional neutrons in the process. These extra neutrons can in turn fission uranium-235 nuclei, leading to a chain reaction.

This is exactly the process that takes place in nuclear power plants, where heat, which is the end product of nuclear fission, is used to boil water, generate steam, and turn an electrical generator. (The disadvantage of this method is the release of radioactive waste, which must be reliably disposed of).

Now we are ready to understand the essence of hot nuclear fusion. As mentioned in Lesson 5, proton and neutron clusters are most stable when the number of protons and neutrons approximately corresponds to their number in the nucleus of an iron atom. Like uranium, which normally contains too many neutron-protons, light elements such as hydrogen, helium, carbon, nitrogen, and oxygen contain too few of these pairs.

If you create the necessary conditions for these nuclei to interact, they will combine into more stable groupings with the release of heat. This is the process of synthesis. In nature, it is found in stars such as the Sun. In nature, compressed hydrogen is very hot, and after a while, a fusion reaction occurs. If the process had originally taken place with deuterons, which already contain a doubled proton and neutron, reactions in stars would proceed relatively easily. The speed at which an atom of each particular type moves inside a cloud of similar atoms is directly dependent on temperature. The higher the temperature, the higher the speed, and the closer the atoms are to each other, making a one-time collision.

In stars, the temperature is high enough for the electrons to leave the core. Thus, we can say that in reality we are dealing with a mixed cloud of electrons and nuclei. At a very high temperature, the nuclei at the moment of collision are so close to each other that the nuclear force is turned on, attracting them to each other. As a result, the nuclei can "stick together" and turn into a lower-energy bunch of protons and neutrons, releasing heat. Hot fusion is an attempt to carry out this process in the laboratory using deuterium and ternary hydrogen (whose nucleus contains 1 proton and 2 neutrons) as a gas. For hot fusion, it is required to maintain a gas temperature of hundreds of millions of degrees, which can be achieved using a magnetic field, but only for 1-2 seconds. It is hoped that it will be possible to maintain the temperature of the gas for a longer period of time. As long as the temperature is high enough, the nuclear reaction proceeds at the moment of collision of the nuclei.

The main form in which energy is released is the release of high-energy neutrons and protons. Protons are very quickly converted into heat. The energy of neutrons can also turn into heat, however, after that the equipment becomes radioactive. It is very difficult to decontaminate equipment, so hot fusion is not suitable as a method for commercial power generation. In any case, hot fusion energy is a dream that has been around for at least 50 years. However, most scientists view hot fusion as the only way to generate fusion energy. The process of hot fusion produces less radiation than fission, it is an environmentally friendly and practically unlimited source of fuel on Earth (relative to modern energy consumption, it would be enough for many millions of years).

Finally, we come to the explanation of cold fusion. Cold fusion could be a simple and non-radioactive way to release fusion energy. In the process of cold fusion, the protons and neutrons of one nucleus interact with the protons and neutrons of another in a completely different way.

At the same time, the nuclear force contributes to the fact that they form a more stable configuration. For any nuclear reaction, it is necessary that the reacting nuclei have a common volume of space. This requirement is called particle alignment. In hot fusion, particles are combined for a short time, when the repulsive force of two positive charges is overcome, and the nuclei collide. During cold fusion, particle alignment is achieved by forcing deuterium nuclei to behave as fuzzy particles like electrons rather than tiny point particles. When light or heavy hydrogen is added to a heavy metal, each "atom" of hydrogen takes up a position where it is surrounded on all sides by heavy metal atoms.

This form of hydrogen is called intermediate. The electrons of hydrogen atoms, together with the intermediate hydrogen, become part of the mass of electrons in the metal. Each hydrogen nucleus oscillates like a pendulum, passing through a negatively charged cloud of metal electrons. Such a vibration occurs even at very low temperatures, in accordance with the postulates of quantum mechanics. This movement is called zero point movement. In this case, the nuclei become blurry objects, like electrons in an atom. However, such fuzziness is not enough to allow one hydrogen nucleus to interact with another.

Another condition is necessary for two or more hydrogen nuclei to have the same common space. The electric current carried by electrons in a metal behaves like a vibrating material wave, not like point particles. If electrons did not behave like waves in solids, neither transistors nor modern computers would exist today. An electron in the form of a wave is called an electron of the Bloch function. The secret of cold fusion is the need to obtain a deuteron of the Bloch function. In order for two or more deuterons to have a common volume of space, wave deuterons must be produced inside or on the surface of a solid. As soon as the Bloch function deuterons are created, the nuclear force begins to act, and the protons and neutrons that make up the deuteron are reorganized into a more stable configuration of the Bloch function helium, which is accompanied by the release of heat.

To study cold fusion, the experimenter needs to make deuterons go into a wave state and keep them in that state. Cold fusion experiments demonstrating the release of excess heat prove that this is possible. However, so far no one knows how to carry out such a process in the most reliable way. The use of cold fusion promises to provide an energy resource that will last for millions of years, while there will be neither problems of global warming, nor radioactivity - that is why serious efforts should be made to study this phenomenon.

All the physical bodies of nature are built from a type of matter called matter. Substances are divided into two main groups - simple and complex substances.

Compound substances are substances that can be decomposed into other, simpler substances by chemical reactions. In contrast to complex, simple substances are those that cannot be chemically decomposed into even simpler substances.

An example of a complex substance is water, which can be decomposed by a chemical reaction into two other, simpler substances - hydrogen and oxygen. As for the last two, they can no longer be chemically decomposed into simpler substances, and therefore are simple substances, or, in other words, chemical elements.

In the first half of the 19th century, there was an assumption in science that the chemical elements are immutable substances that do not have a common relationship with each other. However, the Russian scientist D. I. Mendeleev (1834 - 1907) for the first time in 1869 revealed the relationship of chemical elements, showing that the qualitative characteristic of each of them depends on its quantitative characteristic - atomic weight.

Studying the properties of chemical elements, D. I. Mendeleev noticed that their properties are periodically repeated depending on their atomic weight. He displayed this periodicity in the form of a table, which was included in science under the name "Mendeleev's Periodic Table of Elements."

Below is the modern periodic table of chemical elements of Mendeleev.

atoms

According to modern concepts of science, each chemical element consists of a set of the smallest material (material) particles called atoms.

An atom is the smallest fraction of a chemical element that can no longer be chemically decomposed into other, smaller and simpler material particles.

Atoms of chemical elements of different nature differ from each other in their physicochemical properties, structure, size, mass, atomic weight, self-energy and some other properties. For example, a hydrogen atom differs sharply in its properties and structure from an oxygen atom, and the latter from a uranium atom, etc.

It has been established that the atoms of chemical elements are extremely small in size. If we conventionally assume that the atoms are spherical in shape, then their diameters should be equal to one hundred millionths of a centimeter. For example, the diameter of the hydrogen atom - the smallest atom in nature - is equal to one hundred millionth of a centimeter (10 -8 cm), and the diameters of the largest atoms, such as the uranium atom, do not exceed three hundred millionths of a centimeter (3 10 -8 cm). Consequently, a hydrogen atom is as many times smaller than a ball with a radius of one centimeter, how much the latter is smaller than the globe.

In accordance with the very small size of atoms, their mass is also very small. For example, the mass of a hydrogen atom is m = 1.67 10 -24 g. This means that one gram of hydrogen contains approximately 6 10 23 atoms.

1/16 of the weight of an oxygen atom is taken as a conventional unit of measurement of the atomic weights of chemical elements. In accordance with this atomic weight of a chemical element, an abstract number is called, showing how many times the weight of a given chemical element is greater than 1/16 of the weight of an oxygen atom.

In the periodic table of elements of D. I. Mendeleev, the atomic weights of all chemical elements are given (see the number placed under the name of the element). From this table, we see that the lightest atom is the hydrogen atom, which has an atomic weight of 1.008. The atomic weight of carbon is 12, oxygen is 16, and so on.

As for the heavier chemical elements, their atomic weight exceeds the atomic weight of hydrogen by more than two hundred times. So, the atomic vert of mercury is 200.6, radium - 226, etc. The higher the order of the number occupied by a chemical element in the periodic system of elements, the greater the atomic weight.

Most of the atomic weights of chemical elements are expressed as fractional numbers. This is to a certain extent explained by the fact that such chemical elements consist of a set of how many kinds of atoms that have different atom weights, but the same chemical properties.

Chemical elements that occupy the same number in the periodic system of elements, and therefore have the same chemical properties but different atomic weights, are called isotopes.

Isotopes are found in most chemical elements, it has two isotopes, calcium - four, zinc - five, tin - eleven, etc. Many isotopes are obtained by art, some of them are of great practical importance.

Elementary particles of matter

For a long time it was believed that the atoms of chemical elements are the limit of the divisibility of matter, that is, as if the elementary "bricks" of the universe. Modern science has rejected this hypothesis, establishing that the atom of any chemical element is a collection of even smaller material particles than the atom itself.

According to the electronic theory of the structure of matter, an atom of any chemical element is a system consisting of a central nucleus around which "elementary" real particles called electrons revolve. The nuclei of atoms, according to generally accepted views, consist of a set of "elementary" material particles - protons and neutrons.

To understand the structure of atoms and the physicochemical processes in them, it is necessary to at least briefly familiarize yourself with the main characteristics of the elementary particles that make up atoms.

Determined that An electron is a material particle that has the smallest negative electric charge observed in nature..

If we conditionally assume that the electron as a particle has a spherical shape, then the electron diameter should be equal to 4 · 10 -13 cm, i.e., it is tens of thousands of times smaller than the diameter of any atom.

An electron, like any other material particle, has mass. The "rest mass" of an electron, that is, the mass that it has in a state of relative rest, is equal to m o \u003d 9.1 10 -28 g.

The exceptionally small "rest mass" of the electron indicates that the inert properties of the electron are extremely weak, which means that the electron under the influence of a variable electric force can oscillate in space with a frequency of many billions of periods per second.

The mass of an electron is so small that it would take 1027 units to obtain one gram of electrons. In order to have at least some physical idea of ​​this colossally large number, we will give an example. If one gram of electrons could be placed in a straight line close to each other, they would form a chain four billion kilometers long.

The mass of an electron, like any other real microparticle, depends on the speed of its movement. An electron, being in a state of relative rest, has a "rest mass", which is of a mechanical nature, like the mass of any physical body. As for the "mass of motion" of the electron, which increases with the growth of the speed of its motion, it is of electromagnetic origin. It is due to the presence of an electromagnetic field in a moving electron as a kind of matter that has mass and electromagnetic energy.

The faster the electron moves, the more the inertial properties of its electromagnetic field are manifested, the greater, therefore, the mass of the latter and, accordingly, its electromagnetic energy. Since the electron with its electromagnetic field constitutes a single, organically connected material system, it is natural that the mass of the motion of the electromagnetic field of the electron can be directly attributed to the electron itself.

An electron, in addition to the properties of a particle, also has wave properties. It has been established by experience that the flow of electrons, like the flow of light, propagates in the form of a wave-like motion. The nature of the wave motion of the electron flow in space is confirmed by the phenomena of interference and diffraction of electronic waves.

Electron interference is the phenomenon of superposition of electronic wills on each other, and electron diffraction- this is the phenomenon of the rounding of the edges of a narrow slit by electron waves through which the electron flow passes. Therefore, an electron is not just a particle, but a "particle-wave", the length of which depends on the mass and speed of the electron.

It has been established that the electron, in addition to its translational motion, also performs a rotational motion around its axis. This type of electron motion is called "spin" (from the English word "spin" - spindle). As a result of such movement, the electron, in addition to the electrical properties due to the electric charge, also acquires magnetic properties, resembling an elementary magnet in this respect.

A proton is a material particle that has a positive electric charge equal in absolute value to the electric charge of an electron.

The proton mass is 1.67 · 10-24 g, i.e., it is approximately 1840 times greater than the "rest mass" of the electron.

Unlike the electron and proton, The neutron does not have an electric charge, i.e., it is an electrically neutral "elementary" particle of matter. The mass of a neutron is practically equal to the mass of a proton.

Electrons, protons and neutrons, being in the composition of atoms, interact with each other. In particular, electrons and protons are mutually attracted to each other as particles with opposite electric charges. At the same time, an electron from an electron and a proton from a proton are repelled as particles with the same electric charges.

The interaction of all these electrically charged particles occurs through their electric fields. These fields are a special kind of matter, consisting of a set of elementary material particles called photons. Each photon has a strictly defined inherent amount of energy (energy quantum).

The interaction of electrically charged material material particles is carried out by exchanging them with each other by photons. The force of interaction between electrically charged particles is usually called electrical force.

Neutrons and protons in the nuclei of atoms also interact with each other. However, this interaction between them is no longer carried out through an electric field, since the neutron is an electrically neutral particle of matter, but through the so-called nuclear field.

This field is also a special kind of matter, consisting of a set of elementary material particles called mesons. The interaction of neutrons and protons is carried out by exchanging mesons with each other. The force of interaction of neutrons and protons with each other is called nuclear force.

It has been established that nuclear forces act in the nuclei of atoms within extremely small distances - approximately 10 - 13 cm.

The nuclear forces are much larger than the electric forces of the mutual repulsion of protons in the nucleus of an atom. This leads to the fact that they are able not only to overcome the forces of mutual repulsion of protons inside the nuclei of atoms, but also to create very strong systems of nuclei from the totality of protons and neutrons.

The stability of the nucleus of each atom depends on the ratio of two contradictory forces - nuclear (mutual attraction of protons and neutrons) and electrical (mutual repulsion of protons).

Powerful nuclear forces acting in the nuclei of atoms contribute to the transformation of neutrons and protons into each other. These interconversions of neutrons and protons are carried out as a result of the release or absorption of lighter elementary particles, such as mesons.

The particles we have considered are called elementary because they do not consist of a collection of other, simpler particles of matter. But at the same time, we must not forget that they are capable of transforming into each other, arising at the expense of each other. Thus, these particles are some complex formations, i.e., their elementarity is conditional.

The chemical structure of atoms

The simplest atom in its structure is the hydrogen atom. It consists of a set of only two elementary particles - a proton and an electron. The proton in the system of the hydrogen atom plays the role of the central nucleus, around which the electron rotates in a certain orbit. On fig. 1 schematically shows a model of a hydrogen atom.

Rice. 1. Scheme of the structure of the hydrogen atom

This model is only a rough approximation to reality. The fact is that the electron as a "particle-wave" does not have a volume sharply delimited from the external environment. And this means that we should not talk about some exact linear orbit of the electron, but about a kind of electron cloud. In this case, the electron most often occupies a certain middle line of the cloud, which is one of its possible orbits in the atom.

It must be said that the orbit of the electron itself is not strictly unchanged and immobile in the atom - it also, due to the change in the mass of the electron, performs some rotational motion. Consequently, the motion of an electron in an atom is relatively complex. Since the nucleus of the hydrogen atom (proton) and the electron rotating around it have opposite electric charges, they are mutually attracted.

At the same time, the energy of the electron, rotating around the nucleus of the atom, develops a centrifugal force that tends to remove it from the nucleus. Consequently, the electric force of mutual attraction of the nucleus of an atom and the electron and the centrifugal force acting on the electron are contradictory forces.

At equilibrium, their electron occupies a relatively stable position in some orbit in the atom. Since the mass of an electron is very small, in order to balance the force of attraction to the nucleus of an atom, it must rotate at an enormous speed, equal to about 6 x 10 15 revolutions per second. This means that an electron in the system of the hydrogen atom, like any other atom, moves along its orbit with a linear speed exceeding a thousand kilometers per second.

Under normal conditions, an electron rotates in an atom of the genus along the orbit closest to the nucleus. At the same time, it has the minimum possible amount of energy. If, for one reason or another, for example, under the influence of some other material particles that have invaded the system of the atom, the electron moves to an orbit more distant from the atom, then it will already have a somewhat larger amount of energy.

However, the electron stays in this new orbit for a negligible time, after which it again rotates to the orbit closest to the nucleus of the atom. With this move, he gives off his excess energy in the form of a quantum of electromagnetic radiation - radiant energy (Fig. 2).

Rice. 2. An electron, when moving from a distant orbit to one closer to the nucleus of an atom, emits a quantum of radiant energy

The more energy an electron receives from the outside, the more distant from the nucleus of the atom it goes to the orbit and the more electromagnetic energy it radiates when it rotates to the orbit closest to the nucleus.

By measuring the amount of energy emitted by an electron during the transition from various orbits to the one closest to the atomic nucleus, it was possible to establish that an electron in the system of the hydrogen atom, as in the system of any other atom, cannot go to any arbitrary orbit, to a strictly defined one in accordance with that energy, which he receives under the action of an external force. The orbits that an electron can occupy in an atom are called allowed orbits.

Since the positive charge of the nucleus of the hydrogen atom (proton charge) and the negative charge of the electron are numerically equal, their total charge is zero. This means that the hydrogen atom, being in the normal state, is an electrically neutral particle.

This is true for atoms of all chemical elements: an atom of any chemical element in its normal state is an electrically neutral particle due to the numerical equality of its positive and negative charges.

Since only one "elementary" particle, the proton, is included in the nucleus of the hydrogen atom, the so-called mass number of this nucleus is equal to one. The mass number of the nucleus of an atom of any chemical element is the total number of protons and neutrons that make up this nucleus.

Natural hydrogen mainly consists of a collection of atoms with a mass number equal to one. However, it also contains another kind of hydrogen atoms, with a mass number equal to two. The atomic nuclei of this heavy hydrogen, called deuterons, consist of two particles - a proton and a neutron. This isotope of hydrogen is called deuterium.

Natural hydrogen contains very little deuterium. For every six thousand atoms of light hydrogen (the mass number is one), there is only one atom of deuterium (heavy hydrogen). There is another isotope of hydrogen - superheavy hydrogen called tritium. In the nuclei of the atom of this isotope of hydrogen, there are three particles: a proton and two neutrons, bound to each other by nuclear forces. The mass number of the nucleus of the tritium atom is three, i.e., the tritium atom is three times heavier than the light hydrogen atom.

Although the atoms of hydrogen isotopes have different masses, they nevertheless have the same chemical properties. For example, light hydrogen, entering into chemical interaction with oxygen, forms a complex substance with it - water. Similarly, the isotope of hydrogen - deuterium, when combined with oxygen, forms water, which, unlike ordinary water, is called heavy water. Heavy water is of great use in the production of nuclear (atomic) energy.

Consequently, the chemical properties of atoms do not depend on the mass of their nuclei, but only on the structure of the electron shell of the atom. Since the atoms of light hydrogen, deuterium and tritium have the same number of electrons (one for each atom), these isotopes have the same chemical properties.

It is no coincidence that the chemical element hydrogen occupies the first number in the periodic system of elements. The fact is that between the number of any element in the periodic system of elements and the value of the charge of the nucleus of an atom of this element, there is some connection. It can be formulated like this: the serial number of any chemical element in the periodic system of elements is numerically equal to the positive charge of the nucleus of this element, and, consequently, to the number of electrons rotating around it.

Since hydrogen occupies the first number in the periodic system of elements, this means that the positive charge of the nucleus of its atom is equal to one and that one electron rotates around the nucleus.

The chemical element helium occupies the second number in the periodic system of elements. This means that it has a positive electric charge of the nucleus, equal to two units, i.e., there should be two protons in its nucleus, and two electrodes in the electron shell of the atom.

Natural helium consists of two isotopes - heavy and light helium. The mass number of heavy helium is four. This means that the composition of the nucleus of a heavy helium atom, in addition to the above two protons, must include two more neutrons. As for light helium, its mass number is equal to three, i.e., in addition to two protons, its nucleus must include one more neutron.

It has been established that in natural helium the number of light helium atoms is approximately one millionth of the heavy genius atoms. On fig. 3 shows a schematic model of a helium atom.

Rice. 3. Scheme of the structure of the helium atom

Further complication of the structure of atoms of chemical elements occurs due to an increase in the number of protons and neutrons in the nuclei of these atoms and, simultaneously, due to an increase in the number of electrons revolving around the nuclei (Fig. 4). Using the periodic system of elements, it is easy to determine the number of electrons, protons and neutrons that make up various atoms.

Rice. 4. Schemes of the structure of the nuclei of atoms: 1 - helium, 2 - carbon, 3 - oxygen

The serial number of a chemical element is equal to the number of protons in the nucleus of an atom, and at the same time to the number of electrons revolving around the nucleus. As for the atomic weight, it is approximately equal to the mass number of the atom, i.e., the number of protons and neutrons taken together in the nucleus. Therefore, by subtracting from the atomic weight of an element a number equal to the ordinal number of the element, one can determine how many neutrons are contained in a given nucleus.

It has been established that the nuclei of light chemical elements, containing equally protons and neutrons, are distinguished by very high strength, since the nuclear forces in them are relatively large. For example, the nucleus of a heavy helium atom is exceptionally strong, since it is composed of two protons and two neutrons bound together by powerful nuclear forces.

The nuclei of atoms of heavier chemical elements already contain in their composition an unequal number of protons and neutrons, therefore their bond in the nucleus is weaker than in the nuclei of light chemical elements. The nuclei of these elements can be relatively easily split when bombarded with atomic "projectiles" (neutrons, nuclei of the helium atom, etc.).

As for the heaviest chemical elements, in particular radioactive ones, their nuclei are distinguished by such low strength that they spontaneously decay into their component parts. For example, atoms of the radioactive element radium, consisting of a combination of 88 protons and 138 neutrons, spontaneously decay, turning into atoms of the radioactive element radon. The atoms of the latter, in turn, break down into constituent parts, passing into atoms of other elements.

Having briefly reviewed the constituent parts of the nuclei of atoms of chemical elements, let us consider the structure of the electron shells of atoms. As is known, electrons can revolve around the nuclei of atoms only in strictly defined orbits. Moreover, they are so grouped in the electron shell of each atom that individual layers of electrons can be distinguished.

Each layer can contain the number of electrons, not exceeding a strictly defined number. So, for example, in the first electron layer closest to the nucleus of an atom, there can be a maximum of two electrons, in the second - no more than eight electrons, etc.

Those atoms in which the outer electron layers are completely filled have the most stable electron shell. This means that this atom firmly holds all its electrons and does not need to receive an additional amount of them from outside. For example, a helium atom has two electrons that completely fill the first electron layer, and a neon atom has ten electrons, of which the first two completely fill the first electron layer, and the rest - the second (Fig. 5).

Rice. 5. Scheme of the structure of the neon atom

Consequently, the atoms of helium and neon have quite stable electron shells, they do not seek to modify them quantitatively in any way. Such elements are chemically inert, that is, they do not enter into chemical interaction with other elements.

However, most chemical elements have atoms in which the outer electron layers are not completely filled with electrons. For example, a potassium atom has nineteen electrons, of which eighteen completely fill the first three layers, and the nineteenth electron is alone in the next, unfilled electron layer. Weak filling of the fourth electron layer with electrons leads to the fact that the nucleus of the atom very weakly holds the outermost - the nineteenth electron, and therefore the latter can be easily torn out of the atom. .

Or, for example, an oxygen atom has eight electrons, of which two completely fill the first layer, and the remaining six are located in the second layer. Thus, to complete the construction of the second electron layer in the oxygen atom, it lacks only two electrons. Therefore, the oxygen atom not only firmly holds its six electrons in the second layer, but also has the ability to attract two missing electrons to itself to fill its second electron layer. This he achieves by chemical combination with atoms of elements in which the outer electrons are weakly bound to their nuclei.

Chemical elements whose atoms do not have outer electron layers completely filled with electrons are, as a rule, chemically active, that is, they readily enter into chemical interaction.

So, electrons in the atoms of chemical elements are arranged in a strictly defined order, and any change in their spatial arrangement or number in the electron shell of an atom leads to a change in the physicochemical properties of the latter.

The equality of the number of electrons and protons in the system of an atom is the reason that its total electric charge is equal to zero. If the equality of the number of electrons and protons in the system of an atom is violated, then the atom becomes an electrically charged system.

An atom, in the system of which the balance of opposite electric charges is disturbed due to the fact that it has lost part of its electrons or, on the contrary, has acquired an excess number of them, is called an ion.

Conversely, if an atom acquires a certain excess number of electrons, then it becomes a negative ion. For example, a chlorine atom, having received one extra electron, turns into a singly charged negative chlorine ion Cl - . The oxygen atom, which has received an extra two electrons, turns into a doubly charged negative oxygen ion O, etc.

An atom that has turned into an ion becomes an electrically charged system in relation to the external environment. And this means that the atom began to have an electric field, together with which it constitutes a single material system and through this field carries out electrical interaction with other electrically charged particles of matter - ions, electrons, positively charged atomic nuclei, etc.

The ability of unlike ions to mutually attract each other is the reason that they are chemically combined, forming more complex particles of matter - molecules.

In conclusion, it should be noted that the dimensions of an atom are very large compared with the dimensions of those material particles of which they are composed. The nucleus of the most complex atom, together with all the electrons, occupies a billionth of the atom's volume. A simple calculation shows that if one cubic meter of platinum could be compressed so tightly that intra-atomic and inter-atomic spaces disappeared, then a volume equal to approximately one cubic millimeter would be obtained.

Aktobe, 2014

Hadron. The class of elementary particles participating in the strong interaction. Hadrons are made up of quarks and are divided into two groups: baryons (made of three quarks) and mesons (made of a quark and an antiquark). Most of the matter we observe consists of baryons: protons and nucleons that are part of the nuclei of atoms.

Radiation source activity is the ratio of the total number of decays of radioactive nuclei in a radioactive source to the decay time.

alpha radiation- type of ionizing radiation - a stream of positively charged particles (alpha particles) emitted during radioactive decay and nuclear reactions. The penetrating power of alpha radiation is low (delayed by a sheet of paper). It is extremely dangerous for alpha radiation sources to enter the body with food, air or through skin lesions.

Alpha decay(or α-decay) - spontaneous emission of alpha particles (nuclei of the helium atom) by atomic nuclei

alpha particle- a particle consisting of two protons and two neutrons. Identical to the nucleus of the helium atom.

Annihilation- the interaction of an elementary particle and an antiparticle, as a result of which they disappear, and their energy is converted into electromagnetic radiation.

Annihilation is the reaction of the transformation of a particle and an antiparticle upon collision into other particles.

An antiparticle is a particle that has the same values ​​of mass, spin, charge, and other physical properties as its "twin" particle, but differs from it in signs of some interaction characteristics (for example, in the sign of electric charge).

Antiparticles are twins of ordinary elementary particles, which differ from the latter by the sign of the electric charge and the signs of some other characteristics. Particles and antiparticles have the same masses, spins, and lifetimes.

AC- nuclear power plant - an industrial enterprise for the production of electrical or thermal energy using one or more nuclear power reactors and a set of necessary systems, devices, equipment and structures with the necessary personnel,

Atom- the smallest particle of a chemical element that retains its properties. Consists of a nucleus with protons and neutrons and electrons moving around the nucleus. The number of electrons in an atom is equal to the number of protons in the nucleus.

Atomic mass is the mass of an atom of a chemical element, expressed in atomic mass units (a.m.u.). For 1 amu 1/12 of the mass of a carbon isotope with an atomic mass of 12 is accepted. 1amu = 1.6605655 10-27 kg. The atomic mass is the sum of the masses of all the protons and neutrons in a given atom.

atomic nucleus- the positively charged central part of the atom, around which electrons revolve and in which almost the entire mass of the atom is concentrated. Consists of protons and neutrons. The nuclear charge is determined by the total charge of protons in the nucleus and corresponds to the atomic number of the chemical element in the periodic system of elements.

baryons- particles consisting of three quarks that determine their quantum numbers. All baryons, with the exception of the proton, are unstable.

storage pool- an installation located at the reactor site of a nuclear power plant for temporary storage of spent nuclear fuel under a layer of water in order to reduce radioactivity and decay heat.

becquerel(Bq) is the SI unit of the activity of a radioactive substance. 1 Bq is equal to the activity of such a radioactive substance, in which one act of decay occurs in 1 s.
β γ-rays is the flow of fast electrons.
α-rays is the flow of helium nuclei.
γ rays- electromagnetic waves with a very short wavelength (L ~ 10 -10 m).

beta radiation- type of ionizing radiation - a stream of electrons or positrons emitted during nuclear reactions or radioactive decay. Beta radiation can penetrate into the tissues of the body to a depth of 1 cm. It poses a danger to humans both in terms of external and internal exposure.

beta particles- electrons and positrons emitted by atomic nuclei, as well as a free neutron during beta decay. During the electronic beta decay of an atomic nucleus, an electron e - (as well as an antineutrino) is emitted, during the positron decay of nuclei - a positron e + (and a neutrino ν). When a free neutron (n) decays, a proton (p) is formed, an electron and an antineutrino: n → p + e - +.
Electron and positron– stable particles with spin J = 1/2 (internal mechanical angular momentum), belonging to the class of leptons. The positron is the antiparticle with respect to the electron.

Biological protection- a radiation barrier created around the reactor core and its cooling system to prevent the harmful effects of neutron and gamma radiation on personnel, the public and the environment. Concrete is the main biological protection material at a nuclear power plant. For high-power reactors, the thickness of the concrete protective screen reaches several meters.

Bosons(from the name of the Indian physicist S. Bose) - elementary particles, atomic nuclei, atoms with zero or integer spin (0ћ, 1ћ, 2ћ, ...).

fast neutrons- neutrons, the kinetic energy of which is higher than some certain value. This value can vary over a wide range and depends on the application (reactor physics, protection or dosimetry). In reactor physics, this value is most often chosen to be 0.1 MeV.

cloud chamber– a track detector of elementary charged particles, in which the track (trace) of a particle forms a chain of small droplets of liquid along the trajectory of its movement.

Gamma radiation- type of ionizing radiation - electromagnetic radiation emitted during radioactive decay and nuclear reactions, propagating at the speed of light and having high energy and penetrating power. It is effectively weakened when interacting with heavy elements, such as lead. To attenuate gamma radiation in nuclear reactors of nuclear power plants, a thick-walled protective screen made of concrete is used.

Law of radioactive decay- the law by which the number of undecayed atoms is found: N \u003d N 0 2 -t / T.

Deuterium- "heavy" isotope of hydrogen with atomic mass 2.

Ionizing radiation detector- sensitive element of the measuring instrument intended for registration of ionizing radiation. Its action is based on the phenomena that occur when radiation passes through matter.

Radiation dose- in radiation safety - a measure of the impact of ionizing radiation on a biological object, in particular a person. There are exposure, absorbed and equivalent doses.

Excess mass(or mass defect) - expressed in units of energy, the difference between the mass of a neutral atom and the product of the number of nucleons (the total number of protons and neutrons) in the nucleus of this atom per atomic mass unit

isotopes- nuclides having the same atomic number but different atomic masses (for example, uranium-235 and uranium-238).

isotopes- atomic nuclei having the same number of protons Z, a different number of neutrons N and, consequently, a different mass number A = Z + N. Example: calcium isotopes Ca (Z = 20) - 38 Ca, 39 Ca, 40 Ca, 41 Ca, 42 Ca.

Radioactive isotopes are isotope nuclei that undergo radioactive decay. Most known isotopes are radioactive (~3500).

cloud chamber- a device for observing traces of microparticles moving at high speed (electrons, protons, a-particles, etc.). Created in 1912 by the English physicist Wilson.

A quark is an elementary charged particle participating in the strong interaction. Protons and neutrons are each made up of three quarks.

cosmic radiation- background ionizing radiation, which consists of primary radiation coming from outer space and secondary radiation resulting from the interaction of primary radiation with the atmosphere.

Cosmic rays are streams of high-energy charged elementary particles (mainly protons, alpha particles and electrons) propagating in interplanetary and interstellar space and continuously "bombarding" the Earth.

multiplication factor- the most important characteristic of a fission chain reaction, showing the ratio of the number of neutrons of a given generation to the number of neutrons of the previous generation in an infinite medium. Another definition of the multiplication factor is often used - the ratio of the rates of generation and absorption of neutrons.

Critical mass- the smallest mass of fuel in which a self-sustaining chain reaction of nuclear fission can proceed with a certain design and composition of the core (depends on many factors, for example: fuel composition, moderator, core shape, etc.).

Curie (Ci)- off-system unit of activity, initially the activity of 1 g of the radium-226 isotope. 1Ci=3.7 1010 Bq.

Critical mass(t k) - the smallest mass of nuclear fuel (uranium, plutonium), at which a nuclear chain reaction is carried out.

Curie(Ki) is an off-system unit of activity of a radioactive substance. 1 Ci \u003d 3.7 10 10 Bq.

Leptons(from the Greek leptos - light, small) - a group of point particles with a spin of 1/2ћ, not participating in strong interaction. Lepton size (if it exists)<10 -17 см. Лептоны считаются точечными бесструктурными частицами. Существует три пары лептонов:

• electron (e -) and electron neutrino (ν e),
• muon (μ –) and muon neutrino (ν μ),
• tau lepton (τ –) and tau neutrino (ν τ),

Magic nuclei are atomic nuclei containing the so-called magic numbers of protons or neutrons.

Z
N

These nuclei have a binding energy greater than neighboring nuclei. They have a high nucleon separation energy and an increased abundance in nature.

Mass number(A) is the total number of nucleons (protons and neutrons) in the atomic nucleus; one of the main characteristics of the atomic nucleus.

Dose rate- the ratio of the radiation dose increment over a time interval to this interval (for example: rem/s, Sv/s, mrem/h, mSv/h, µrem/h, µSv/h).

Neutron- neutral elementary frequent with a mass close to the proton mass. Together with protons, neutrons form the atomic nucleus. In the free state, it is unstable and decays into a proton and an electron.

Nuclide- a type of atom with a certain number of protons and neutrons in the nucleus, characterized by atomic mass and atomic (serial) number.

Enrichment (by isotope):

2. A process that increases the content of a particular isotope in a mixture of isotopes.

Enrichment of uranium ore- a set of processes for the primary processing of mineral uranium-containing raw materials, with the aim of separating uranium from other minerals that make up the ore. In this case, there is no change in the composition of minerals, but only their mechanical separation with the production of ore concentrate.

Enriched nuclear fuel- nuclear fuel, in which the content of fissile nuclides is higher than in the initial natural raw material.

Enriched uranium- uranium, in which the content of the uranium-235 isotope is higher than in natural uranium.

Half life(T) is the time interval during which half of the initial number of nuclei will decay.

Half life is the time it takes for half of the radioactive nuclei to decay. This quantity, denoted T 1/2 , is a constant for a given radioactive nucleus (isotope). The value of T 1/2 clearly characterizes the decay rate of radioactive nuclei and is equivalent to two other constants that characterize this rate: the average lifetime of a radioactive nucleus τ and the probability of decay of a radioactive nucleus per unit time λ.

Absorbed radiation dose- the ratio of the absorbed energy E of ionizing radiation to the mass of the irradiated substance.

Bohr's postulates- the main assumptions introduced without proof by N. Bohr, which form the basis of the quantum theory of the atom.

Displacement rule: during a-decay, the nucleus loses its positive charge 2e, and its mass decreases by approximately 4 a.m.u.; in b-decay, the charge of the nucleus increases by 1e, and the mass does not change.

Half-life of a radionuclide is the time during which the number of nuclei of a given radionuclide decreases by half as a result of spontaneous decay.

Positron- an antiparticle of an electron with a mass equal to the mass of an electron, but with a positive electric charge.

Proton- a stable positively charged elementary particle with a charge of 1.61 10-19 C and a mass of 1.66 10-27 kg. The proton forms the nucleus of the "light" isotope of the hydrogen atom (protium). The number of protons in the nucleus of any element determines the charge of the nucleus and the atomic number of that element.

Radioactivity- spontaneous transformation (radioactive decay) of an unstable nuclide into another nuclide, accompanied by the emission of ionizing radiation.

Radioactivity- the ability of some atomic nuclei to spontaneously transform into other nuclei, while emitting various particles.

radioactive decay- spontaneous nuclear transformation.

Breeder Reactor- a fast reactor, in which the conversion factor exceeds 1 and expanded reproduction of nuclear fuel is carried out.

Geiger counter(or Geiger-Muller counter) - a gas-filled counter of charged elementary particles, the electrical signal from which is amplified due to the secondary ionization of the gas volume of the counter and does not depend on the energy left by the particle in this volume.

TVEL- a heat-generating element. The main structural element of the active zone of a heterogeneous reactor, in the form of which fuel is loaded into it. In the fuel rods, fission of heavy nuclei U-235, Pu-239 or U-233 occurs, accompanied by the release of energy, and thermal energy is transferred from them to the coolant. The fuel rods consist of a fuel core, a cladding and end pieces. The type of fuel element is determined by the type and purpose of the reactor, coolant parameters. The fuel element must ensure reliable heat removal from the fuel to the coolant.

Working body- medium (heat carrier) used to convert thermal energy into mechanical energy.

Dark matter− invisible (non-radiating and non-absorbing) substance. Its existence is definitely evidenced by gravitational effects. Observational data also indicate that this dark matter-energy is divided into two parts:

• the first is the so-called dark matter with a density
  W dm = 0.20–0.25, are unknown, weakly interacting massive particles (not baryons). These can be, for example, stable neutral particles with masses from 10 GeV/c2 to 10 TeV/c2 predicted by supersymmetric models, including hypothetical heavy neutrinos;

the second is the so-called dark energy with a density
W Λ = 0.70–0.75), which is interpreted as a vacuum. This refers to a special form of matter - the physical vacuum, i.e. the lowest energy state of the physical fields penetrating space.

thermonuclear reactions− fusion reactions (synthesis) of light nuclei occurring at high temperatures. These reactions usually proceed with the release of energy, since in the heavier nucleus formed as a result of the fusion, the nucleons are bound more strongly, i.e. have, on average, a higher binding energy than in the initial merging nuclei. The excess total binding energy of nucleons is then released in the form of the kinetic energy of the reaction products. The name “fusion reactions” reflects the fact that these reactions take place at high temperatures ( > 10 7 –10 8 K), because for merging, light nuclei must approach each other to distances equal to the radius of action of nuclear forces of attraction, i.e. up to distances ≈10 -13 cm.

Transuranium elements- chemical elements with a charge (number of protons) greater than that of uranium, i.e. Z > 92.

fission chain reaction- a self-sustaining reaction of fission of heavy nuclei, in which neutrons are continuously reproduced, dividing more and more new nuclei.

fission chain reaction- the sequence of the fission reaction of the nuclei of heavy atoms when they interact with neutrons or other elementary particles, as a result of which lighter nuclei, new neutrons or other elementary particles are formed and nuclear energy is released.

Nuclear chain reaction- a sequence of nuclear reactions excited by particles (for example, neutrons) that are born in each act of the reaction. Depending on the average number of reactions following one previous one - less than, equal to or greater than one - the reaction is called damped, self-sustaining or growing.

Chain nuclear reactions- self-sustaining nuclear reactions, in which a chain of nuclei is sequentially involved. This happens when one of the products of a nuclear reaction reacts with another nucleus, the product of the second reaction reacts with the next nucleus, and so on. A chain of successive nuclear reactions occurs. The most famous example of such a reaction is the nuclear fission reaction caused by a neutron

exothermic reactions- nuclear reactions proceeding with the release of energy.

Elementary particles- the smallest particles of physical matter. Ideas about elementary particles reflect that stage in the knowledge of the structure of matter, which has been achieved by modern science. Together with antiparticles, about 300 elementary particles have been discovered. The term "elementary particles" is arbitrary, since many elementary particles have a complex internal structure.

Elementary particles- material objects that cannot be divided into component parts. In accordance with this definition, elementary particles cannot include molecules, atoms and atomic nuclei that can be divided into constituent parts - an atom is divided into a nucleus and orbital electrons, a nucleus - into nucleons.

Energy yield of a nuclear reaction- the difference between the rest energies of nuclei and particles before and after the reaction.

Endothermic reactions- nuclear reactions proceeding with the absorption of energy.

The binding energy of the atomic nucleus(E St) - characterizes the intensity of the interaction of nucleons in the nucleus and is equal to the maximum energy that must be expended to divide the nucleus into separate non-interacting nucleons without imparting kinetic energy to them.

Mössba effect uera - the phenomenon of resonant absorption of gamma quanta by atomic nuclei without energy loss for momentum return.

Nuclear (planetary) model of the atom- in the center there is a positive charged nucleus (diameter about 10 -15 m); around the nucleus, like the planets of the solar system, electrons move in circular orbits.

nuclear models– simplified theoretical descriptions of atomic nuclei based on the representation of the nucleus as an object with predetermined characteristic properties.

Nuclear fission reaction- the reaction of fission of atomic nuclei of heavy elements under the action of neutrons.

nuclear reaction- the reaction of the transformation of atomic nuclei as a result of interaction with each other or with any elementary particles.

Nuclear power is the energy released as a result of the internal restructuring of atomic nuclei. Nuclear energy can be obtained in nuclear reactions or radioactive decay of nuclei. The main sources of nuclear energy are the fission reactions of heavy nuclei and the synthesis (combination) of light nuclei. The latter process is also called thermonuclear reactions.

nuclear forces- forces acting between nucleons in atomic nuclei and determining the structure and properties of nuclei. They are short-range, their range is 10-15 m.

Nuclear reactor- a device in which a controlled chain reaction of nuclear fission is carried out.

A self-sustaining fission chain reaction is a chain reaction in a medium for which the multiplication factor k >= 1.

nuclear accident- A nuclear accident is the loss of control of a chain reaction in a reactor, or the formation of a critical mass during reloading, transportation and storage of fuel rods. As a result of a nuclear accident, fuel rods are damaged due to the imbalance of the generated and removed heat, with the release of radioactive fission products to the outside. In this case, potentially dangerous exposure of people and contamination of the surrounding area becomes possible. .

Nuclear safety- a general term that characterizes the properties of a nuclear installation during normal operation and, in the event of an accident, to limit the radiation impact on personnel, the public and the environment to acceptable limits.

Nuclear fission- a process accompanied by the splitting of the nucleus of a heavy atom upon interaction with a neutron or other elementary particle, as a result of which lighter nuclei, new neutrons or other elementary particles are formed and energy is released.

nuclear material- any source material, special nuclear material and sometimes ores and ore waste.

nuclear transformation- the transformation of one nuclide into another.

Nuclear reactor- a device in which a controlled nuclear chain reaction is carried out. Nuclear reactors are classified according to purpose, neutron energy, type of coolant and moderator, core structure, design and other characteristic features.

nuclear reaction- the transformation of atomic nuclei, caused by their interaction with elementary particles, or with each other, and accompanied by a change in the mass, charge or energy state of the nuclei.

Nuclear fuel- material containing fissile nuclides, which, when placed in a nuclear reactor, allows a nuclear chain reaction to take place. It has a very high energy intensity (with the complete fission of 1 kg of U-235, energy equal to J is released, while the combustion of 1 kg of organic fuel releases energy of the order of (3-5) J, depending on the type of fuel).

Nuclear fuel cycle- a set of measures to ensure the operation of nuclear reactors carried out in a system of enterprises interconnected by a flow of nuclear material and including uranium mines, uranium ore processing plants, uranium conversion, fuel enrichment and fabrication, nuclear reactors, spent fuel storage facilities, spent fuel reprocessing plants fuels and associated intermediate storage and storage facilities for the disposal of radioactive waste

nuclear plant- any facility that generates, processes or handles radioactive or fissile materials in quantities such that nuclear safety issues need to be taken into account.

Nuclear power- the internal energy of atomic nuclei released during nuclear fission or nuclear reactions.

Nuclear power reactor- a nuclear reactor, the main purpose of which is to generate energy.

Nuclear reactor- a nuclear reactor is a device designed to organize a controlled self-sustaining fission chain reaction - a sequence of nuclear fission reactions, in which free neutrons are released, which are necessary for the fission of new nuclei.

Fast neutron nuclear reactor- Reactors differ significantly in the neutron spectrum - the distribution of neutrons by energy, and, consequently, in the spectrum of absorbed (causing nuclear fission) neutrons. If the core does not contain light nuclei specially designed for slowing down as a result of elastic scattering, then practically all the slowing down is due to inelastic scattering of neutrons by heavy and medium-weight nuclei. In this case, most of the fissions are caused by neutrons with energies of the order of tens and hundreds of keV. Such reactors are called fast neutron reactors.

Nuclear reactor on thermal neutrons- a reactor whose core contains such an amount of moderator - a material designed to reduce the energy of neutrons without noticeable absorption, that most fissions are caused by neutrons with energies less than 1 eV.

nuclear forces- forces holding nucleons (protons and neutrons) in the nucleus.

Nuclear forces are short-range . They appear only at very small distances between nucleons in the nucleus of the order of 10 -15 m. The length (1.5 - 2.2) 10 -15 is called range of nuclear forces .

Nuclear forces discover charge independence , i.e., the attraction between two nucleons is the same regardless of the charge state of the nucleons - proton or neutron.

Nuclear forces have saturation property , which manifests itself in the fact that the nucleon in the nucleus interacts only with a limited number of neighboring nucleons closest to it. Almost complete saturation of nuclear forces is achieved in the α-particle, which is a very stable formation.

nuclear forces depend on the orientation of the spins of the interacting nucleons . This is confirmed by the different character of neutron scattering by ortho- and steam-hydrogen molecules.

nuclear forces are not central .

By studying the structure of matter, physicists learned what atoms are made of, got to the atomic nucleus and split it into protons and neutrons. All these steps were given quite easily - it was only necessary to disperse the particles to the required energy, push them against each other, and then they themselves fell apart into their component parts.

But with protons and neutrons, this trick has not worked. Although they are composite particles, they cannot be "broken apart" in any even the most violent collision. Therefore, it took physicists decades to come up with different ways to look inside the proton, to see its structure and shape. Today, the study of the structure of the proton is one of the most active areas of elementary particle physics.

Nature gives hints

The history of studying the structure of protons and neutrons dates back to the 1930s. When, in addition to protons, neutrons were discovered (1932), by measuring their mass, physicists were surprised to find that it is very close to the mass of a proton. Moreover, it turned out that protons and neutrons "feel" the nuclear interaction in exactly the same way. So much the same that, from the point of view of nuclear forces, the proton and neutron can be considered as if two manifestations of the same particle - the nucleon: the proton is an electrically charged nucleon, and the neutron is a neutral nucleon. Swap protons for neutrons and nuclear forces will (almost) not notice anything.

Physicists express this property of nature as symmetry - the nuclear interaction is symmetrical with respect to the replacement of protons by neutrons, just as a butterfly is symmetrical with respect to the replacement of left for right. This symmetry, in addition to playing an important role in nuclear physics, was actually the first hint that nucleons have an interesting internal structure. True, then, in the 1930s, physicists did not realize this hint.

Understanding came later. It began with the fact that in the 1940s and 50s, in the reactions of proton collisions with the nuclei of various elements, scientists were surprised to discover more and more new particles. Not protons, not neutrons, pi-mesons not discovered by that time, which keep nucleons in nuclei, but some completely new particles. For all their diversity, these new particles had two common properties. First, they, like nucleons, very willingly participated in nuclear interactions - now such particles are called hadrons. And secondly, they were extremely unstable. The most unstable of them decayed into other particles in just a trillionth of a nanosecond, not even having time to fly by the size of an atomic nucleus!

For a long time, the "zoo" of hadrons was a complete hodgepodge. In the late 1950s, physicists already recognized quite a lot of different types of hadrons, began to compare them with each other, and suddenly saw a certain general symmetry, even periodicity, in their properties. It was conjectured that inside all hadrons (including nucleons) there are some simple objects, which are called "quarks". Combining quarks in different ways, it is possible to obtain different hadrons, moreover, of exactly the same type and with such properties that were found in the experiment.

What makes a proton a proton?

After physicists discovered the quark structure of hadrons and learned that quarks come in several different varieties, it became clear that many different particles could be constructed from quarks. So no one was surprised when subsequent experiments continued to find new hadrons one after another. But among all the hadrons, a whole family of particles was found, consisting, just like the proton, of only two u-quarks and one d-quark. A sort of "brothers" of the proton. And here the physicists were in for a surprise.

Let's make one simple observation first. If we have several objects consisting of the same "bricks", then heavier objects contain more "bricks", and lighter ones - less. This is a very natural principle, which can be called the principle of combination or the principle of superstructure, and it is perfectly fulfilled both in everyday life and in physics. It manifests itself even in the structure of atomic nuclei - after all, heavier nuclei simply consist of a larger number of protons and neutrons.

However, at the level of quarks, this principle does not work at all, and, admittedly, physicists have not yet fully figured out why. It turns out that the heavy brothers of the proton also consist of the same quarks as the proton, although they are one and a half or even two times heavier than the proton. They differ from the proton (and differ from each other) not composition, but mutual location quarks, by the state in which these quarks are relative to each other. It is enough to change the mutual position of the quarks - and we will get another, noticeably heavier, particle from the proton.

But what happens if you still take and collect together more than three quarks? Will a new heavy particle be obtained? Surprisingly, it will not work - the quarks will break in threes and turn into several disparate particles. For some reason, nature "does not like" to combine many quarks into one! Only very recently, literally in recent years, hints have begun to appear that some multiquark particles do exist, but this only emphasizes how much nature does not like them.

A very important and profound conclusion follows from this combinatorics - the mass of hadrons does not at all consist of the mass of quarks. But if the mass of a hadron can be increased or decreased by simply recombining its building blocks, then the quarks themselves are not at all responsible for the mass of hadrons. Indeed, in subsequent experiments, it was possible to find out that the mass of the quarks themselves is only about two percent of the mass of the proton, and the rest of the gravity arises due to the force field (special particles - gluons) that bind the quarks together. By changing the mutual arrangement of quarks, for example, by moving them away from each other, we thereby change the gluon cloud, make it more massive, which is why the mass of the hadron increases (Fig. 1).

What is going on inside a fast flying proton?

Everything described above concerns a motionless proton, in the language of physicists, this is the structure of a proton in its rest frame. However, in the experiment, the structure of the proton was first discovered in other conditions - inside fast flying proton.

In the late 1960s, in particle collision experiments at accelerators, it was noticed that protons flying at near-light speed behaved as if the energy inside them was not distributed evenly, but concentrated in separate compact objects. The famous physicist Richard Feynman proposed to call these clumps of matter inside protons partons(from English part- Part).

In subsequent experiments, many of the properties of partons were studied—for example, their electrical charge, their number, and the proportion of proton energy each carries. It turns out that charged partons are quarks and neutral partons are gluons. Yes, yes, those very gluons, which in the rest frame of the proton simply “served” the quarks, attracting them to each other, are now independent partons and, along with the quarks, carry the “matter” and energy of a fast-flying proton. Experiments have shown that approximately half of the energy is stored in quarks, and half in gluons.

Partons are most conveniently studied in the collision of protons with electrons. The fact is that, unlike a proton, an electron does not participate in strong nuclear interactions and its collision with a proton looks very simple: the electron emits a virtual photon for a very short time, which crashes into a charged parton and eventually generates a large number of particles ( Fig. 2). We can say that the electron is an excellent scalpel for "opening" the proton and splitting it into separate parts - however, only for a very short time. Knowing how often such processes occur at the accelerator, it is possible to measure the number of partons inside the proton and their charges.

Who are the real partons?

And here we come to another amazing discovery that physicists have made while studying elementary particle collisions at high energies.

Under normal conditions, the question of what this or that object consists of has a universal answer for all frames of reference. For example, a water molecule consists of two hydrogen atoms and one oxygen atom - and it does not matter whether we are looking at a stationary or moving molecule. However, this rule - it would seem so natural! - violated if we are talking about elementary particles moving at speeds close to the speed of light. In one frame of reference, a complex particle may consist of one set of subparticles, and in another frame of reference, of another. It turns out that composition is a relative concept!

How can this be? The key here is one important property: the number of particles in our world is not fixed - particles can be born and disappear. For example, if two electrons with a sufficiently high energy are pushed together, then in addition to these two electrons, either a photon, or an electron-positron pair, or some other particles can be born. All this is allowed by quantum laws, and this is exactly what happens in real experiments.

But this "law of non-conservation" of particles works in collisions particles. But how is it that the same proton from different points of view looks like it consists of a different set of particles? The fact is that a proton is not just three quarks put together. There is a gluon force field between quarks. In general, a force field (like, for example, a gravitational or electric field) is a kind of material “entity” that permeates space and allows particles to exert force on each other. In quantum theory, the field also consists of particles, though special ones - virtual ones. The number of these particles is not fixed, they are constantly "budding" from quarks and being absorbed by other quarks.

resting The proton can indeed be thought of as three quarks, between which gluons jump. But if we look at the same proton from a different frame of reference, as if from the window of a “relativistic train” passing by, we will see a completely different picture. Those virtual gluons that glued the quarks together will seem to be less virtual, "more real" particles. They, of course, are still born and absorbed by quarks, but at the same time they live on their own for some time, flying next to the quarks, like real particles. What looks like a simple force field in one frame of reference turns into a stream of particles in another frame! Note that we do not touch the proton itself, but only look at it from a different frame of reference.

Further more. The closer the speed of our "relativistic train" to the speed of light, the more amazing picture inside the proton we will see. As we approach the speed of light, we will notice that there are more and more gluons inside the proton. Moreover, they sometimes split into quark-antiquark pairs, which also fly side by side and are also considered partons. As a result, an ultrarelativistic proton, i.e., a proton moving relative to us at a speed very close to the speed of light, appears as interpenetrating clouds of quarks, antiquarks and gluons that fly together and seem to support each other (Fig. 3).

The reader familiar with the theory of relativity may be worried. All physics is based on the principle that any process proceeds in the same way in all inertial frames of reference. And here it turns out that the composition of the proton depends on the frame of reference from which we observe it?!

Yes, that's right, but it doesn't violate the principle of relativity in any way. The results of physical processes - for example, which particles and how many are born as a result of a collision - do turn out to be invariant, although the composition of the proton depends on the frame of reference.

This situation, unusual at first glance, but satisfying all the laws of physics, is schematically illustrated in Figure 4. It shows how a collision of two high-energy protons looks in different frames of reference: in the rest frame of one proton, in the center of mass frame, in the rest frame of another proton . The interaction between protons is carried out through a cascade of splitting gluons, but only in one case this cascade is considered the “inside” of one proton, in the other case it is part of another proton, and in the third case it is just an object exchanged between two protons. This cascade exists, it is real, but which part of the process it should be attributed to depends on the frame of reference.

3D portrait of a proton

All the results that we have just described were based on experiments performed quite a long time ago - in the 60s and 70s of the last century. It would seem that since then everything should already be studied and all questions should find their answers. But no - the device of the proton is still one of the most interesting topics in particle physics. Moreover, in recent years, interest in it has increased again, because physicists have figured out how to get a "three-dimensional" portrait of a fast moving proton, which turned out to be much more complicated than a portrait of a stationary proton.

Classical proton collision experiments tell only about the number of partons and their energy distribution. In such experiments, partons participate as independent objects, which means that it is impossible to learn from them how partons are located relative to each other, how exactly they add up to a proton. It can be said that for a long time only a “one-dimensional” portrait of a fast-flying proton was available to physicists.

In order to build a real, three-dimensional, portrait of the proton and to know the distribution of partons in space, much more subtle experiments are required than those that were possible 40 years ago. Physicists have learned to perform such experiments quite recently, literally in the last decade. They realized that among the huge number of different reactions that occur when an electron collides with a proton, there is one special reaction - deep virtual Compton scattering, - which will be able to tell about the three-dimensional structure of the proton.

In general, Compton scattering, or the Compton effect, is the elastic collision of a photon with some particle, such as a proton. It looks like this: a photon arrives, is absorbed by a proton, which briefly goes into an excited state, and then returns to its original state, emitting a photon in some direction.

Compton scattering of ordinary light photons does not lead to anything interesting - it is a simple reflection of light from a proton. In order to "come into play" the internal structure of the proton and "feel" the distribution of quarks, it is necessary to use photons of very high energy - billions of times more than in ordinary light. And just such photons - however, virtual - are easily generated by an incident electron. If we now combine one with the other, then we get deep-virtual Compton scattering (Fig. 5).

The main feature of this reaction is that it does not destroy the proton. The incident photon does not just hit the proton, but, as it were, carefully feels it and then flies away. The direction in which it flies away and what part of the energy the proton takes away from it depends on the structure of the proton, on the relative position of the partons inside it. That is why, by studying this process, it is possible to restore the three-dimensional appearance of the proton, as if "to fashion its sculpture."

True, it is very difficult for an experimental physicist to do this. The desired process occurs quite rarely, and it is difficult to register it. The first experimental data on this reaction were obtained only in 2001 at the HERA accelerator in the German accelerator complex DESY in Hamburg; the new data series is now being processed by experimenters. However, already today, based on the first data, theorists draw three-dimensional distributions of quarks and gluons in the proton. The physical quantity, about which physicists used to build only assumptions, finally began to “appear” from the experiment.

Are there any unexpected discoveries in this area? It is likely that yes. As an illustration, let's say that in November 2008 an interesting theoretical article appeared, which states that a fast-flying proton should not look like a flat disk, but a biconcave lens. This happens because the partons sitting in the central region of the proton are more compressed in the longitudinal direction than the partons sitting on the edges. It would be very interesting to test these theoretical predictions experimentally!

Why is all this interesting to physicists?

Why do physicists need to know exactly how matter is distributed inside protons and neutrons?

First, this is required by the very logic of the development of physics. There are many amazingly complex systems in the world that modern theoretical physics cannot yet fully cope with. Hadrons are one such system. Understanding the structure of hadrons, we hone the ability of theoretical physics, which may well turn out to be universal and perhaps help in something completely different, for example, in the study of superconductors or other materials with unusual properties.

Secondly, there is an immediate benefit for nuclear physics. Despite almost a century of history of studying atomic nuclei, theorists still do not know the exact law of the interaction of protons and neutrons.

They have to partly guess this law on the basis of experimental data, and partly construct it on the basis of knowledge about the structure of nucleons. This is where new data on the three-dimensional structure of nucleons will help.

Thirdly, a few years ago, physicists managed to obtain nothing less than a new aggregate state of matter - quark-gluon plasma. In this state, quarks do not sit inside individual protons and neutrons, but freely walk around the entire bunch of nuclear matter. It can be achieved, for example, as follows: heavy nuclei are accelerated in the accelerator to a speed very close to the speed of light, and then they collide head-on. In this collision, for a very short time, a temperature of trillions of degrees arises, which melts the nuclei into a quark-gluon plasma. So, it turns out that the theoretical calculations of this nuclear melting require a good knowledge of the three-dimensional structure of nucleons.

Finally, these data are very necessary for astrophysics. When heavy stars explode at the end of their lives, they often leave extremely compact objects - neutron and possibly quark stars. The core of these stars consists entirely of neutrons, and perhaps even of cold quark-gluon plasma. Such stars have long been discovered, but what happens inside them can only be guessed at. So a good understanding of quark distributions can lead to progress in astrophysics as well.

• Translation

At the center of every atom is the nucleus, a tiny collection of particles called protons and neutrons. In this article, we will study the nature of protons and neutrons, which consist of even smaller particles - quarks, gluons and antiquarks. (Gluons, like photons, are their own antiparticles.) Quarks and gluons, as far as we know, can be truly elementary (indivisible and not composed of something smaller). But to them later.

Surprisingly, protons and neutrons have almost the same mass - up to a percentage:

• 0.93827 GeV/c 2 for a proton,
• 0.93957 GeV/c 2 for a neutron.

This is the key to their nature - they are actually very similar. Yes, there is one obvious difference between them: the proton has a positive electrical charge, while the neutron has no charge (it is neutral, hence its name). Accordingly, electrical forces act on the first, but not on the second. At first glance, this distinction seems to be very important! But actually it is not. In all other senses, the proton and neutron are almost twins. They have identical not only masses, but also the internal structure.

Because they are so similar, and because these particles make up nuclei, protons and neutrons are often referred to as nucleons.

Protons were identified and described around 1920 (although they were discovered earlier; the nucleus of a hydrogen atom is just a single proton), and neutrons were found around 1933. The fact that protons and neutrons are so similar to each other was understood almost immediately. But the fact that they have a measurable size comparable to the size of the nucleus (about 100,000 times smaller than an atom in radius) was not known until 1954. That they are made up of quarks, antiquarks, and gluons was gradually understood from the mid-1960s to the mid-1970s. By the late 70's and early 80's, our understanding of protons, neutrons, and what they are made of had largely settled down, and has remained unchanged ever since.

Nucleons are much more difficult to describe than atoms or nuclei. This is not to say that atoms are in principle simple, but at least one can say without hesitation that a helium atom consists of two electrons in orbit around a tiny helium nucleus; and the helium nucleus is a fairly simple group of two neutrons and two protons. But with nucleons, everything is not so simple. I already wrote in the article "What is a proton, and what does it have inside?" that the atom is like an elegant minuet, and the nucleon is like a wild party.

The complexity of the proton and neutron seems to be real, and does not stem from incomplete physical knowledge. We have equations used to describe quarks, antiquarks, and gluons, and the strong nuclear forces that go on between them. These equations are called QCD, from "quantum chromodynamics". The accuracy of the equations can be tested in various ways, including measuring the number of particles that appear at the Large Hadron Collider. By plugging the QCD equations into a computer and running calculations on the properties of protons and neutrons, and other similar particles (collectively called "hadrons"), we get predictions of the properties of these particles that approximate well to observations made in the real world. Therefore, we have reason to believe that the QCD equations do not lie, and that our knowledge of the proton and neutron is based on the correct equations. But just having the right equations is not enough, because:

• Simple equations can have very complex solutions,
• Sometimes it is not possible to describe complex solutions in a simple way.

As far as we can tell, this is exactly the case with nucleons: they are complex solutions to simple QCD equations, and it is not possible to describe them in a couple of words or pictures.

Because of the inherent complexity of nucleons, you, the reader, will have to make a choice: how much do you want to know about the complexity described? No matter how far you go, you will most likely not be satisfied: the more you learn, the clearer the topic will become, but the final answer will remain the same - the proton and neutron are very complex. I can offer you three levels of understanding, with increasing detail; you can stop after any level and move on to other topics, or you can dive to the last. Each level raises questions that I can partly answer in the next, but new answers raise new questions. In the end - as I do in professional discussions with colleagues and advanced students - I can only refer you to data from real experiments, various influential theoretical arguments, and computer simulations.

First level of understanding

What are protons and neutrons made of?

Rice. 1: an oversimplified version of protons, consisting of only two up quarks and one down, and neutrons, consisting of only two down quarks and one up

To simplify matters, many books, articles and websites state that protons are made up of three quarks (two up and one down) and draw something like a figure. 1. The neutron is the same, only consisting of one up and two down quarks. This simple image illustrates what some scientists believed, mostly in the 1960s. But it soon became clear that this point of view was oversimplified to the point that it was no longer correct.

From more sophisticated sources of information, you will learn that protons are made up of three quarks (two up and one down) held together by gluons - and a picture similar to Fig. 2, where gluons are drawn as springs or strings that hold quarks. Neutrons are the same, with only one up quark and two down quarks.

Rice. 2: improvement fig. 1 due to the emphasis on the important role of the strong nuclear force, which keeps quarks in the proton

Not such a bad way to describe nucleons, as it emphasizes the important role of the strong nuclear force, which holds quarks in a proton at the expense of gluons (just like the photon, the particle that makes up light, is associated with the electromagnetic force). But that's also confusing because it doesn't really explain what gluons are or what they do.

There are reasons to go ahead and describe things the way I did in : a proton is made up of three quarks (two up and one down), a bunch of gluons, and a mountain of quark-antiquark pairs (mostly up and down quarks, but there are a few weird ones too) . They all fly back and forth at very high speeds (approaching the speed of light); this entire set is held together by the strong nuclear force. I have shown this in Fig. 3. Neutrons are again the same, but with one up and two down quarks; the quark that has changed ownership is indicated by an arrow.

Rice. 3: more realistic, though still not ideal, depiction of protons and neutrons

These quarks, antiquarks, and gluons not only scurry back and forth, but also collide with each other and turn into each other through processes such as particle annihilation (in which a quark and an antiquark of the same type turn into two gluons, or vice versa) or absorption and emission of a gluon (in which a quark and a gluon can collide and produce a quark and two gluons, or vice versa).

What do these three descriptions have in common:

• Two up quarks and a down quark (plus something else) for a proton.
• One up quark and two down quarks (plus something else) for a neutron.
• The “something else” for neutrons is the same as the “something else” for protons. That is, nucleons have “something else” the same.
• The small difference in mass between the proton and the neutron appears due to the difference in the masses of the down quark and the up quark.

And since:

• for up quarks, the electric charge is 2/3 e (where e is the charge of the proton, -e is the charge of the electron),
• down quarks have a charge of -1/3e,
• gluons have a charge of 0,
• any quark and its corresponding antiquark have a total charge of 0 (for example, the anti-down quark has a charge of +1/3e, so the down quark and down antiquark will have a charge of –1/3 e +1/3 e = 0),

Each figure assigns the electric charge of the proton to two up and one down quarks, and “something else” adds 0 to the charge. Similarly, the neutron has zero charge due to one up and two down quarks:

• total electric charge of the proton 2/3 e + 2/3 e – 1/3 e = e,
• the total electric charge of the neutron is 2/3 e – 1/3 e – 1/3 e = 0.

These descriptions differ as follows:

• how much "something else" inside the nucleon,
• what is it doing there
• where do the mass and mass energy (E = mc 2 , the energy present there even when the particle is at rest) of the nucleon come from.

Since most of the mass of an atom, and therefore of all ordinary matter, is contained in protons and neutrons, the last point is extremely important for a correct understanding of our nature.

Rice. 1 says that quarks, in fact, represent a third of a nucleon - much like a proton or a neutron represents a quarter of a helium nucleus or 1/12 of a carbon nucleus. If this picture were true, the quarks in the nucleon would move relatively slowly (at speeds much slower than the speed of light) with relatively weak forces acting between them (albeit with some powerful force holding them in place). The mass of the quark, up and down, would then be on the order of 0.3 GeV/c 2 , about a third of the mass of a proton. But this is a simple image, and the ideas it imposes are simply wrong.

Rice. 3. gives a completely different idea of ​​the proton, as a cauldron of particles scurrying through it at speeds close to the speed of light. These particles collide with each other, and in these collisions some of them annihilate and others are created in their place. Gluons have no mass, the masses of the upper quarks are about 0.004 GeV/c 2 , and the masses of the lower quarks are about 0.008 GeV/c 2 - hundreds of times less than a proton. Where does the mass energy of the proton come from, the question is complex: part of it comes from the mass energy of quarks and antiquarks, part comes from the energy of motion of quarks, antiquarks and gluons, and part (perhaps positive, perhaps negative) from the energy stored in the strong nuclear interaction, holding quarks, antiquarks, and gluons together.

In a sense, Fig. 2 tries to eliminate the difference between fig. 1 and fig. 3. It simplifies the rice. 3, removing many quark-antiquark pairs, which, in principle, can be called ephemeral, since they constantly arise and disappear, and are not necessary. But it gives the impression that the gluons in the nucleons are a direct part of the strong nuclear force that holds the protons. And it doesn't explain where the mass of the proton comes from.

At fig. 1 has another drawback, besides the narrow frames of the proton and neutron. It does not explain some of the properties of other hadrons, such as the pion and the rho meson. The same problems exist in Fig. 2.

These restrictions have led to the fact that I give my students and on my website a picture from fig. 3. But I want to warn you that it also has many limitations, which I will consider later.

It should be noted that the extreme complexity of the structure, implied in Fig. 3 is to be expected from an object held together by such a powerful force as the strong nuclear force. And one more thing: three quarks (two up and one down for a proton) that are not part of a group of quark-antiquark pairs are often called "valence quarks", and pairs of quark-antiquarks are called a "sea of ​​quark pairs." Such a language is technically convenient in many cases. But it gives the false impression that if you could look inside the proton, and look at a particular quark, you could immediately tell if it was part of the sea or a valence. This cannot be done, there is simply no such way.

Proton mass and neutron mass

Since the masses of the proton and neutron are so similar, and since the proton and neutron differ only in the replacement of an up quark by a down quark, it seems likely that their masses are provided in the same way, come from the same source, and their difference lies in the slight difference between the up and down quarks. . But the three figures above show that there are three very different views on the origin of the proton mass.

Rice. 1 says that the up and down quarks simply make up 1/3 of the mass of the proton and neutron: about 0.313 GeV/c 2 , or because of the energy needed to keep the quarks in the proton. And since the difference between the masses of a proton and a neutron is a fraction of a percent, the difference between the masses of an up and down quark must also be a fraction of a percent.

Rice. 2 is less clear. What fraction of the mass of a proton exists due to gluons? But, in principle, it follows from the figure that most of the mass of the proton still comes from the mass of quarks, as in Fig. 1.

Rice. 3 reflects a more subtle approach to how the mass of the proton actually comes about (as we can verify directly through computer calculations of the proton, and not directly using other mathematical methods). It is very different from the ideas presented in Fig. 1 and 2, and it turns out to be not so simple.

To understand how this works, one must think not in terms of the proton's mass m, but in terms of its mass energy E = mc 2 , the energy associated with mass. The conceptually correct question is not “where does the proton mass m come from”, after which you can calculate E by multiplying m by c 2 , but the opposite: “where does the energy of the proton mass E come from”, after which you can calculate the mass m by dividing E by c 2 .

It is useful to classify contributions to the proton mass energy into three groups:

A) The mass energy (rest energy) of the quarks and antiquarks contained in it (gluons, massless particles, do not make any contribution).
B) Energy of motion (kinetic energy) of quarks, antiquarks and gluons.
C) The interaction energy (binding energy or potential energy) stored in the strong nuclear interaction (more precisely, in the gluon fields) holding the proton.

Rice. 3 says that the particles inside the proton move at a high speed, and that it is full of massless gluons, so the contribution of B) is greater than A). Usually, in most physical systems, B) and C) are comparable, while C) is often negative. So the mass energy of the proton (and neutron) is mostly derived from the combination of B) and C), with A) contributing a small fraction. Therefore, the masses of the proton and neutron appear mainly not because of the masses of the particles contained in them, but because of the energies of motion of these particles and the energy of their interaction associated with the gluon fields that generate the forces that hold the proton. In most other systems we are familiar with, the balance of energies is distributed differently. For example, in atoms and in the solar system, A) dominates, while B) and C) are obtained much less and are comparable in size.

Summing up, we point out that:

• Rice. 1 suggests that the mass energy of the proton comes from the contribution A).
• Rice. 2 suggests that both contributions A) and C) are important, and B) makes a small contribution.
• Rice. 3 suggests that B) and C) are important, while the contribution of A) is negligible.

We know that rice is correct. 3. To test it, we can run computer simulations, and more importantly, thanks to various compelling theoretical arguments, we know that if the masses of the up and down quarks were zero (and everything else remained as it is), the mass of the proton is practically would change. So, apparently, the masses of quarks cannot make important contributions to the mass of the proton.

If fig. 3 is not lying, the masses of the quark and antiquark are very small. What are they really like? The mass of the top quark (as well as the antiquark) does not exceed 0.005 GeV/c 2 , which is much less than 0.313 GeV/c 2 , which follows from Fig. 1. (The mass of an up quark is difficult to measure and varies due to subtle effects, so it could be much less than 0.005 GeV/c2). The mass of the bottom quark is approximately 0.004 GeV/c 2 greater than the mass of the top one. This means that the mass of any quark or antiquark does not exceed one percent of the mass of a proton.

Note that this means (contrary to Fig. 1) that the ratio of the mass of the down quark to the up quark does not approach unity! The mass of the down quark is at least twice that of the up quark. The reason that the masses of the neutron and proton are so similar is not that the masses of the up and down quarks are similar, but that the masses of the up and down quarks are very small - and the difference between them is small, relative to the masses of the proton and neutron. Recall that to convert a proton into a neutron, you simply need to replace one of its up quarks with a down quark (Figure 3). This change is enough to make the neutron slightly heavier than the proton, and change its charge from +e to 0.

By the way, the fact that different particles inside a proton are colliding with each other, and constantly appearing and disappearing, does not affect the things we are discussing - energy is conserved in any collision. The mass energy and the energy of motion of quarks and gluons can change, as well as the energy of their interaction, but the total energy of the proton does not change, although everything inside it is constantly changing. So the mass of a proton remains constant, despite its internal vortex.

At this point, you can stop and absorb the information received. Amazing! Virtually all the mass contained in ordinary matter comes from the mass of nucleons in atoms. And most of this mass comes from the chaos inherent in the proton and neutron - from the energy of motion of quarks, gluons and antiquarks in nucleons, and from the energy of the work of strong nuclear interactions that hold the nucleon in its whole state. Yes: our planet, our bodies, our breath are the result of such a quiet and, until recently, unimaginable pandemonium.