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The gamma radiation flux, after passing through the controlled object and the film, enters the detection working unit, where it is converted into statistically distributed electrical pulses. The average rate of pulse arrival from the sensor output is proportional to the exposure dose rate. The blackening density of the film is determined by the exposure dose; therefore, the required exposure time, which ensures the optimal blackening density of the film, can be set by the number of pulses.
Density occurs when a stream of gamma radiation interacts with matter.
Sources of ionizing radiation during a nuclear explosion are fluxes of gamma radiation and neutrons, which have a damaging effect in the area of the explosion within 10 - 15 seconds from the moment of explosion, as well as gamma quanta, alpha and beta particles of radioactive substances - fission fragments of nuclear charge matter , falling in the area of the explosion and along the path of movement of the resulting radioactive cloud and contaminating an area of tens and hundreds of kilometers. The degree of damage is determined by the dose of ionizing radiation - the amount of energy absorbed by 1 cm3 of the medium.
Radiation level detectors operate on the principle that the intensity of the gamma radiation flux depends on the density of the controlled environment. The source and receiver of radioactive radiation are installed at a given level on opposite sides of the controlled container. An increase or decrease in the flow of gamma rays triggers the executive relay.
The principle of operation of a gamma relay is that the intensity of the gamma radiation flux incident on the converting element depends on the density of the medium through which it penetrates. The receiving station and the gamma radiation source unit are installed on opposite sides of the capacitance being measured at controlled levels.
Experimental verification of the above-discussed technique was carried out both for the case of modulation of gamma radiation fluxes, and for the case of modulation of light fluxes.
So, approximately 1/4 (1/2 1/2) of the total luminosity will be observed as a large flux of gamma rays, and the rest as soft X-rays.
Radiation source blocks KO, K1, K2 and KZ are designed to generate a directed gamma radiation flow, as well as to protect personnel from gamma radiation flows acting in other directions.
The operation of the devices is based on the sensor converting the gamma radiation flow coming from the source unit into an electrical signal transmitted via a cable to the electronic relay unit to activate the relay. The intensity of the gamma radiation flux hitting the sensor depends on the density of the medium through which it penetrates.
The principle of operation of a gamma relay is that the intensity of the gamma radiation flux incident on the sensor depends on the density of the medium through which it penetrates. The sensor converts the gamma radiation flow into an electrical signal, amplifies it and transmits it via a cable to the electronic relay unit, where it is further converted into a showing result.
Gamma radiation is one of the short-wave types of electromagnetic radiation. Due to the extremely short wavelength, gamma-ray radiation has pronounced corpuscular properties, while wave properties are practically absent.
Gamma has a powerful traumatic effect on living organisms, and at the same time it is completely impossible to recognize by the senses.
It belongs to the group of ionizing radiation, that is, it contributes to the transformation of stable atoms of various substances into ions with a positive or negative charge. The speed of gamma radiation is comparable to the speed of light. The discovery of previously unknown radiation flows was made in 1900 by the French scientist Villard.
Letters from the Greek alphabet were used for the names. Radiation, located on the scale of electromagnetic radiation after X-rays, is called gamma - the third letter of the alphabet.
It should be understood that the boundaries between different types of radiation are very arbitrary.
What is gamma radiation
Let's try, avoiding specific terminology, to understand what gamma-ionizing radiation is. Any substance consists of atoms, which in turn include a nucleus and electrons. The atom, and especially its nucleus, are highly stable, so their splitting requires special conditions.
If these conditions somehow arise or are obtained artificially, a process of nuclear decay occurs, which is accompanied by the release of a large amount of energy and elementary particles.
Depending on what exactly is released in this process, radiation is divided into several types. Alpha, beta and neutron radiation are distinguished by the release of elementary particles, and x-ray and gamma active ray are a flow of energy.
Although, in fact, any radiation, including radiation in the gamma range, is similar to a stream of particles. In the case of this radiation, the flux particles are photons or quarks.
According to the laws of quantum physics, the shorter the wavelength, the higher the energy of the radiation quanta.
Since the wavelength of gamma rays is very short, it can be argued that the energy of gamma radiation is extremely high.
The emergence of gamma radiation
Sources of radiation in the gamma range are various processes. There are objects in the universe in which reactions occur. The result of these reactions is cosmic gamma radiation.
Main sources of gamma rays These are quasars and pulsars. Nuclear reactions with massive release of energy and gamma radiation also occur during the process of a star transforming into a supernova.
Gamma electromagnetic radiation occurs during various transitions in the region of the atomic electron shell, as well as during the decay of the nuclei of some elements. Among the sources of gamma rays, one can also name a certain environment with a strong magnetic field, where elementary particles are inhibited by the resistance of this environment.
The dangers of gamma rays
Due to its properties, gamma spectrum radiation has a very high penetrating ability. To stop her, you need a lead wall at least five centimeters thick.
The skin and other protective mechanisms of a living creature are not an obstacle to gamma radiation. It penetrates directly into cells, having a destructive effect on all structures. Irradiated molecules and atoms of a substance themselves become a source of radiation and provoke the ionization of other particles.
As a result of this process, some substances are transformed into others. From them new cells with a different genome are made. Remnants of old structures that are unnecessary during the construction of new cells become toxins for the body.
The greatest danger of radiation rays for living organisms that have received a dose of radiation is that they are not able to sense the presence of this deadly wave in space. And also that living cells do not have any specific protection against the destructive energy carried by gamma-ionizing radiation. This type of radiation has the greatest impact on the state of germ cells carrying DNA molecules.
Different cells of the body behave differently in gamma rays and have varying degrees of resistance to the effects of this type of energy. However, another property of gamma radiation is its cumulative ability.
A single irradiation with a small dose does not cause irreparable destructive effects on a living cell. That is why radiation has been used in science, medicine, industry and other areas of human activity.
Applications of gamma rays
The inquisitive minds of scientists have found areas of application even for deadly rays. Currently, gamma radiation is used in various industries, for the benefit of science, and is also successfully used in various medical devices.
The ability to change the structure of atoms and molecules has proven to be beneficial in the treatment of serious diseases that destroy the body at the cellular level.
For the treatment of oncological tumors, gamma rays are indispensable, as they can destroy abnormal cells and stop their rapid division. Sometimes it is impossible to stop the abnormal growth of cancer cells, then gamma radiation comes to the rescue, where the cells are completely destroyed.
Gamma-ionizing radiation is used to destroy pathogenic microflora and various potentially dangerous contaminants. Medical instruments and devices are sterilized in radioactive rays. This type of radiation is also used to disinfect certain products.
Gamma rays are used to illuminate various all-metal products for space and other industries in order to detect hidden defects. In those areas of production where extreme control over the quality of products is necessary, this type of testing is simply irreplaceable.
Using gamma rays, scientists measure the depth of drilling and obtain data on the possibility of occurrence of various rocks. Gamma rays can also be used in selection. Certain selected plants are irradiated with a strictly dosed flow in order to obtain the desired mutations in their genome. In this way, breeders obtain new plant breeds with the properties they need.
Using the gamma flux, the speeds of spacecraft and artificial satellites are determined. By sending beams into outer space, scientists can determine the distance and simulate the path of the spacecraft.
Methods of protection
The Earth has a natural defense mechanism against cosmic radiation: the ozone layer and the upper atmosphere.
Those rays that, having enormous speeds, penetrate into the protected space of the earth do not cause much harm to living beings. The greatest danger comes from sources and gamma radiation received in terrestrial conditions.
The most important source of danger from radiation contamination remains enterprises where controlled nuclear reactions are carried out under human control. These are nuclear power plants where energy is produced to provide the population and industry with light and heat.
The most serious measures are being taken to provide for the workers of these facilities. The tragedies that occurred in different parts of the world, due to the loss of human control over the nuclear reaction, taught people to be careful with the invisible enemy.
Protection of power plant workers
At nuclear power plants and industries involving the use of gamma radiation, the time of contact with a source of radiation hazard is strictly limited.
All employees who have a business need to contact or be near a source of gamma radiation use special protective suits and undergo several stages of cleaning before returning to the “clean” area.
For effective protection against gamma rays, materials with high strength are used. These include lead, high-strength concrete, lead glass, and certain types of steel. These materials are used in the construction of protective circuits of power plants.
Elements from these materials are used to create anti-radiation suits for power plant employees who have access to radiation sources.
In the so-called “hot” zone, lead cannot withstand the load, since its melting point is not high enough. In the area where thermonuclear reactions occur, releasing high temperatures, expensive rare earth metals such as tungsten and tantalum are used.
All people dealing with gamma radiation are provided with individual measuring instruments.
Due to the lack of natural sensitivity to radiation, a person can use a dosimeter to determine how much radiation dose he received over a certain period.
A dose not exceeding 18-20 microroentgens per hour is considered normal. Nothing particularly terrible will happen when exposed to a dose of up to 100 microroentgens. If a person receives such a dose, the effects may appear after two weeks.
When receiving a dose of 600 roentgens, a person faces death in 95% of cases within two weeks. A dose of 700 roentgens is lethal in 100% of cases.
Of all types of radiation, gamma rays pose the greatest danger to humans. Unfortunately, the possibility of radiation poisoning exists for everyone. Even if you are away from industrial plants that produce energy through nuclear fission, you can be exposed to radiation.
History knows examples of such tragedies.
Penetrating radiation is a stream of gamma rays and neutrons emitted from the area of a nuclear explosion.
The sources of penetrating radiation are nuclear reactions and radioactive decay of the products of a nuclear explosion.
The duration of action of penetrating radiation does not exceed 10-15 sec since the explosion. During this time, the decay of short-lived fission fragments formed as a result of a nuclear reaction ends. In addition, the radioactive cloud rises to a great height and radioactive radiation is absorbed by the air without reaching the earth's surface.
Penetrating radiation is characterized radiation dose , i.e., the amount of radioactive radiation energy absorbed per unit volume of the irradiated environment. The radiation dose quantitatively characterizes the ionization that fluxes of gamma rays and neutrons can produce in an air volume.
The ionization process consists of “knocking out” electrons from the electron shell of atoms. As a result, electrically neutral atoms turn into differently charged particles - ions.
Penetrating radiation is the sum of gamma radiation and neutron doses.
Gamma radiation , constituting the bulk of penetrating radiation, it occurs both directly at the moment of explosion in the process of an explosive nuclear reaction, and after the explosion as a result of radioactive capture of neutrons by the nuclei of atoms of various elements. The effect of gamma radiation lasts 10-15 sec.
The unit for measuring the dose of gamma ray radiation is the X-ray special international physical unit of dose (amount of energy).
X-ray - This is the amount of gamma radiation that at a temperature of 0° and a pressure of 760 mm creates 2 billion ion pairs in 1 cm 3 of dry air (more precisely, 2.08-10 9). Denoted by the letter X-ray R. A thousandth of a roentgen is called a milliroentgen and is designated Mr.
Neutron flux , occurring during a nuclear explosion, contains fast and slow neutrons, which have different effects on living organisms. The share of neutrons in the total dose of penetrating radiation is less than the share of gamma rays. It increases slightly with decreasing power of a nuclear explosion.
The main source of neutrons in a nuclear explosion is a nuclear chain reaction. The neutron stream is emitted within a fraction of a second after the explosion and can cause artificial induced radiation in metal objects and soil. Induced radioactivity is observed only in the area immediately adjacent to the explosion site.
The radiation dose of a neutron flux is measured by a special unit - the biological equivalent of an x-ray.
Biological equivalent of an x-ray(BER) is a dose of neutrons, the biological effect of which is equivalent to the effect of 1 R gamma radiation.
The damaging effect of penetrating radiation on people is caused by irradiation , which has a harmful biological effect on living cells of the body. The essence of the damaging effect of penetrating radiation on living organisms is that gamma rays and neutrons ionize the molecules of living cells. This ionization disrupts the normal functioning of cells and, in large doses, leads to their death. Cells lose their ability to divide, resulting in a person becoming ill with the so-called radiation sickness.
The damage to people by penetrating radiation depends on the magnitude of the radiation dose and the time during which this dose is received.
Single dose of radiation over four days up to 50 R, as well as the dose of systematic radiation - up to 100 R within ten days, does not cause external signs of disease and is considered safe. Radiation doses over 100 R cause radiation sickness.
Depending on the radiation dose, there are three degrees of radiation sickness: first (mild), second (moderate) and third (severe).
Radiation sickness first degree occurs at a total radiation dose of 100 - 200 R The latent period lasts two to three weeks, after which malaise, general weakness, nausea, dizziness, and periodic fever appear. The content of white blood cells in the blood decreases. First degree radiation sickness is curable.
Second degree radiation sickness occurs at a total exposure dose of 200 - 300 R. The latent period lasts about a week, after which the same signs of the disease appear as with radiation sickness of the first degree, but in a more pronounced form. With active treatment, recovery occurs within 1.5-2 months.
Radiation sickness of the third degree occurs at a total radiation dose of 300-500 R. The latent period is reduced to several hours. The disease progresses more intensely. With active treatment, recovery occurs within a few months.
Radiation dose over 500 R for humans it is usually considered fatal.
Doses of penetrating radiation depend on the type, power of the explosion and the distance from the center of the explosion. The values of the radii at which different doses of penetrating radiation are possible during explosions of various powers are given in Table 8.
Ionizing radiation (hereinafter referred to as IR) is radiation whose interaction with matter leads to the ionization of atoms and molecules, i.e. this interaction leads to the excitation of the atom and the separation of individual electrons (negatively charged particles) from atomic shells. As a result, deprived of one or more electrons, the atom turns into a positively charged ion - primary ionization occurs. II includes electromagnetic radiation (gamma radiation) and flows of charged and neutral particles - corpuscular radiation (alpha radiation, beta radiation, and neutron radiation).
Alpha radiation refers to corpuscular radiation. This is a stream of heavy positively charged alpha particles (nuclei of helium atoms) resulting from the decay of atoms of heavy elements such as uranium, radium and thorium. Since the particles are heavy, the range of alpha particles in a substance (that is, the path along which they produce ionization) turns out to be very short: hundredths of a millimeter in biological media, 2.5-8 cm in air. Thus, a regular sheet of paper or the outer dead layer of skin can trap these particles.
However, substances that emit alpha particles are long-lived. As a result of such substances entering the body with food, air or through wounds, they are carried throughout the body by the bloodstream, deposited in organs responsible for metabolism and protection of the body (for example, the spleen or lymph nodes), thus causing internal irradiation of the body . The danger of such internal irradiation of the body is high, because these alpha particles create a very large number of ions (up to several thousand pairs of ions per 1 micron of path in tissues). Ionization, in turn, determines a number of features of those chemical reactions that occur in matter, in particular in living tissue (the formation of strong oxidizing agents, free hydrogen and oxygen, etc.).
Beta radiation(beta rays, or stream of beta particles) also refers to the corpuscular type of radiation. This is a stream of electrons (β- radiation, or, most often, just β-radiation) or positrons (β+ radiation) emitted during the radioactive beta decay of the nuclei of certain atoms. Electrons or positrons are produced in the nucleus when a neutron converts to a proton or a proton to a neutron, respectively.
Electrons are significantly smaller than alpha particles and can penetrate 10-15 centimeters deep into a substance (body) (cf. hundredths of a millimeter for alpha particles). When passing through matter, beta radiation interacts with the electrons and nuclei of its atoms, expending its energy on this and slowing down the movement until it stops completely. Due to these properties, to protect against beta radiation, it is enough to have an organic glass screen of appropriate thickness. The use of beta radiation in medicine for superficial, interstitial and intracavitary radiation therapy is based on these same properties.
Neutron radiation- another type of corpuscular type of radiation. Neutron radiation is a flow of neutrons (elementary particles that have no electrical charge). Neutrons do not have an ionizing effect, but a very significant ionizing effect occurs due to elastic and inelastic scattering on the nuclei of matter.
Substances irradiated by neutrons can acquire radioactive properties, that is, receive so-called induced radioactivity. Neutron radiation is generated during the operation of particle accelerators, in nuclear reactors, industrial and laboratory installations, during nuclear explosions, etc. Neutron radiation has the greatest penetrating ability. The best materials for protection against neutron radiation are hydrogen-containing materials.
Gamma rays and x-rays belong to electromagnetic radiation.
The fundamental difference between these two types of radiation lies in the mechanism of their occurrence. X-ray radiation is of extranuclear origin, gamma radiation is a product of nuclear decay.
X-ray radiation was discovered in 1895 by the physicist Roentgen. This is invisible radiation that can penetrate, although to varying degrees, all substances. It is electromagnetic radiation with a wavelength of the order of - from 10 -12 to 10 -7. The source of X-rays is an X-ray tube, some radionuclides (for example, beta emitters), accelerators and electron storage devices (synchrotron radiation).
The X-ray tube has two electrodes - the cathode and the anode (negative and positive electrodes, respectively). When the cathode is heated, electron emission occurs (the phenomenon of the emission of electrons by the surface of a solid or liquid). Electrons escaping from the cathode are accelerated by the electric field and strike the surface of the anode, where they are sharply decelerated, resulting in X-ray radiation. Like visible light, X-rays cause photographic film to turn black. This is one of its properties, fundamental for medicine - that it is penetrating radiation and, accordingly, the patient can be illuminated with its help, and because Tissues of different density absorb X-rays differently - we can diagnose many types of diseases of internal organs at a very early stage.
Gamma radiation is of intranuclear origin. It occurs during the decay of radioactive nuclei, the transition of nuclei from an excited state to the ground state, during the interaction of fast charged particles with matter, the annihilation of electron-positron pairs, etc.
The high penetrating power of gamma radiation is explained by its short wavelength. To weaken the flow of gamma radiation, substances with a significant mass number (lead, tungsten, uranium, etc.) and all kinds of high-density compositions (various concretes with metal fillers) are used.
Wherever there are electrical discharges, radiation of one spectrum or another is encountered. Gamma radiation is one of the types of electromagnetic radiation, which has a very short wavelength and consists of streams of gamma quanta (photons). It has been established that this is not an independent type of radioactivity, but accompanies the decays of alpha and beta radiation. Gamma radiation can also occur during a nuclear reaction, when the deceleration of charged particles, their decay and other nuclear processes occur.
The concept of gamma radiation
Radioactive radiation is ionizing radiation that is generated during the unstable behavior of particles of a different spectrum, when they simply disintegrate into their constituent parts of an atom– protons, neutrons, electrons and photons. Gamma radiation, including X-rays, is the same process. Radiation has different biological effects on the human body - its harm depends on the ability of particles to penetrate through various obstacles.
In this regard, gamma radiation has the most pronounced penetrating ability, which allows it to penetrate even a five-centimeter lead wall. Therefore, gamma radiation, or gamma rays, is radioactive radiation that has a high degree of radioactive effect on a living organism. During radiation, their speed is equal to the speed of light.
The frequency of gamma radiation is > 3 10 18, which is the shortest wave and in the classification of electromagnetic waves it is at the very bottom, just before X-ray radiation, whose radiation is slightly longer and is 10 17 - 3 10 18
Alpha, beta and gamma rays are extremely dangerous to humans and their intense exposure leads to radiation sickness, which manifests itself with characteristic symptoms:
- acute leukocytosis;
- slowing of the pulse, decreased muscle tone, slowdown of all vital processes;
- hair loss;
- sequential failure of all organs - first the liver, kidneys, spinal cord, and then the heart.
Entering the body, radiation rays destroy and mutate cells in such a way that, once infected, they infect others. And those that were able to survive are reborn, no longer capable of division and other vital functions. Alpha and beta rays are the most dangerous, but the gamma particle is insidious in that it travels 300,000 kilometers in 1 second and is capable of striking significant distances. With a small dose of radiation, a person does not feel its effects, and it does not immediately detect its destructive effect. It may take several years or several generations - depending on the dose and type of rays - before damage appears. However, with a large dose of radiation, the disease manifests itself within several hours and has pronounced symptoms with abdominal pain, uncontrollable vomiting, and headaches.
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The dangers of gamma radiation
Gamma rays can penetrate from space; sources of gamma radiation can also be the decay of certain radioactive rocks - uranium, granite, radon and others.
The most famous case of gamma ray poisoning is that of Alexander Litvinenko., who had polonium added to his tea. Polonium is a radioactive element, a derivative of uranium, which is highly radioactive.
The quantum energy of gamma radiation has enormous power, which increases its penetration into living cells and its destructive effect. Causing death and transformation of cells, gamma quanta accumulate in the body over time, and damaged cells simultaneously poison the body with their toxins, which appear during their decomposition.
A gamma quantum is nuclear radiation, a particle without mass or charge, which is emitted during a nuclear reaction when the nucleus passes from one energy state to another. When a gamma-ray quantum passes through a certain substance and interacts with it, the energy of the gamma quantum is completely absorbed by this substance and its electron is released.
The danger of such radiation is most destructive for humans, since its penetrating ability leaves virtually no chance - a 5-centimeter lead wall can absorb only half of the gamma radiation. In this regard, alpha and beta rays are less dangerous - alpha radiation can be stopped by an ordinary sheet of paper, beta radiation cannot penetrate a wooden wall, and there is practically no barrier to gamma radiation. Therefore, it is extremely important that there is no prolonged exposure to these rays on the human body.
How to protect yourself from gamma radiation
Entering the body at an increased gamma background, radiation begins to imperceptibly poison the body, and if ultra-high doses have not been consumed in a short time, then the first signs may not appear soon. First of all, the hematopoietic system suffers, which takes the first blow. The number of leukocytes in it sharply decreases, as a result of which the spinal cord is very quickly affected and fails. Along with the spinal cord, the lymph nodes suffer, which later also fail. A person loses his hair, his DNA is damaged. A genome mutation occurs, which leads to disorders in heredity. With severe damage, death occurs from cancer or failure of one or more organs.
It is necessary to measure the gamma background on land plots before purchasing. Under the influence of some underground rocks, including in underground rivers, during tectonic processes of the earth's crust, it is quite possible for the surface of the earth to be infected with gamma radiation.
Protection from gamma radiation may only be partial. If such a catastrophe is allowed to happen, then within the next 300 years the affected area will be completely poisoned, down to several tens of meters of soil. There is no complete protection, but you can use the basements of residential buildings, underground trenches and other shelters, although it should be remembered that this type of protection is only partially effective.
Thus, methods of protection against gamma radiation consist mainly in measuring the gamma background with special equipment and not visiting places with high levels of radiation - for example, Chernobyl or the environs of Fukushima.
The largest release of nuclear radiation into water in human history occurred in 2011 in Fukushima, when a tsunami wave led to the failure of three nuclear reactors. Radioactive waste has been washed into the sea in the amount of 300 tons every day for the seventh year now. The scale of this catastrophe is terrifying. Since this leak cannot be repaired due to the high temperature in the affected area, it is unknown how long this process will continue to occur. Meanwhile, the radiation had already spread through the underwater current to a significant part of the Pacific Ocean.
Field of application of gamma radiation
If a stream of gamma particles is purposefully applied, then it is possible to selectively destroy those cells of the body that are currently actively reproducing. This effect from the use of gamma rays is used in medicine in the fight against cancer. As a last resort and only when other means stop working, radiation is used specifically to target the malignant tumor. The most effective use of external gamma radiation therapy. This method is designed to better control the process while minimizing risks and damage to healthy tissue.
Gamma quanta are also used in other areas: 
- These rays are used to change energy. The device for this, which is used in experimental physics, is called a gamma spectrometer. It can be magnetic, scintillation, semiconductor and crystal diffraction.
- Studying the spectrum of nuclear gamma radiation provides information about nuclear structure. The external environment, influencing gamma radiation, produces various effects that are of great importance for understanding the processes occurring in this case. Therefore, all these processes are being actively studied.
- The technique also uses gamma rays to detect defects in metals. Since gamma radiation has different levels of absorption in different environments, but at the same propagation distance, it is possible to calculate defects using radiation of varying intensity.
- Radiation chemistry also uses this radiation to initiate chemical transformations in various processes using natural or artificial radioactive isotopes and electron accelerators - sources of this type of radiation.
- The food industry uses sterilization of food products using gamma radiation for its purposes..
- In plant growing, gamma rays are used to ensure that the plant acquires better characteristics through mutation.
- Gamma rays are used to grow and process certain microorganisms and make medicines, including some antibiotics. They treat seeds to rid them of small pests.
Until about 100 years ago, the properties of gamma radiation were not sufficiently studied, and this led to the unprotected use of radioactive elements as medical or measuring equipment. Gamma radiation has also been used to coat various jewelry, ceramics, and stained glass. Therefore, you should be careful when storing and purchasing antiques - a seemingly harmless thing can be fraught with a radioactive threat.