The device with a Muller Geiger meter registers radiation. Geiger meter: device and household variations

Registration of ionizing radiation to devices is based on the radiation transform by the detector and the measuring circuit in the electrical signals adopted in the measurement practice.

Instruments for measuring ionizing radiation can register various physical quantities. The most interesting are the following: absorbed, exposure and equivalent doses and their power, particle flux density, particle fluuens, bulk, mass, surface, efficient activity.

Any device measuring ionizing radiation contains a detector, measuring scheme (recorder or analyzer) and auxiliary elements.

Detector Converts information about the emission parameters to the energy of the electrical signal. By conversion of radiation energy to other types of energy, detectors can be divided into the following groups:

ionization (gas meters, ionization chambers, semiconductor counters);
scintillation;
photographic;
Chemical.

The measuring circuit allocates, converts, accumulates, stores and issues information in the form of electrical signals, convenient for observation, record, calculation or control of other devices. Auxiliary elements Provide specified modes of operation of the detector and measuring circuit. These include power supplies, operational programming blocks, help control and calibration, registering devices (digital-printing devices, recorders, oscilloscopes, pulse counters, etc.).

Functional diagrams of devices are largely defined by the form of signals coming from radiation detectors and from the output of the measuring circuit (in the form of pulses - a discrete form of information or in the form of a slowly changing current (voltage) - analog form of information).

Devices with a discrete form of input and output information may include amplifiers, standardizers and pulse discriminators, countable and analyzing schemes with summation and memory binary, decimal and other methods.

Pulses carrying information on radiation parameters may differ in amplitude, form and time of appearance. The separation of these pulses, but their parameters using the analyzing devices, it is possible to measure not only the density of the radiation flux through the average pulse speed, but also energy, the form and spatial distribution of radiation.

Analyzing devices usually operate in two information processing modes. In the first case, the analyzer is selected pulses with specified parameters, in the second - signals are selected by groups depending on the specified selection parameters.

Electrometric and output amplifiers are used in the appliances with analogue type of input and output information. direct current. In diagrams with a pre-conversion of direct current to the variable, converters and alternating amplifiers are used.

To overlap the required range of measurements with a given accuracy in devices with an analogue view of the output information, showing and self-sash devices with linear and nonlinear scales (logarithmic, linear logarithmic, etc.) are used, as well as digital voltmeters with digital-printing devices.

Information at the output of the appliances can be both discrete and analogue, regardless of the input information form.

Analog information coming from current radiation detectors (ionization chambers), in a number of devices is converted into a discrete dispensing - charge quantization.

A significant number of devices with discrete information at the input have analog output information; These include radiometers, radiometers, intensimetras with the meaning rate of pulses.

The measurement results may be in the form of signals observed visually (the readings of the arrowheads, on the oscilloscope or computer screen, etc.); fixed by the recording device (member counter, self-examination, digital-taking device, etc.). Signals can be audible, generated by phones, calls, sirens, etc., feed to control other devices.

Any type of radiation when reacting with a substance leads to the appearance of ionization and excitation. The charged particles cause these processes directly, when absorbing G-quanta, ionization create fast electrons resulting from a photoelectric effect, the effect of componton or at the birth of steam, and in the case of neutrons, ionization is created by fart-point cores. In this case, one primary particle can lead to the appearance of hundreds of thousands of ions, due to which the secondary effects accompanying the ionization (electric current, a flash of light, the darkening of the photoflax, etc.) can be seen by a person directly with its senses; Sometimes these effects remain only to strengthen the number of times. Thus, ionization is, as it were, a kind of amplifier of the phenomena of the interaction of ionizing radiation with a substance. Therefore, the operation of all recording devices is one way or another due to the use of ionization and excitation of the atoms of the substance.

Electrons formed when different types Interactions, inhibit in the medium, spending its energy to the ionization and excitation of atoms. Formed ions and free electrons quickly recombine, so the charge after a very short time (10-5 s for gases) disappears. This does not happen if in the environment to create an electric field. In this case, the charge carriers will drift along the field, positive in one direction, negative - to another. The movement of charges is electric shock, measuring which, you can determine the amount of charge.

It is so acting ionization chamber. It is a sealed volume filled with gas, in which two metal electrodes are located (Fig. 7.1). The electrodes are attached electrical voltage. During the passage of an electron formed by the interaction of a γ-quantum with a substance, free charges - ions and electrons - drifting to the electrodes, and a current pulse arises proportional to the charge formed by the electron.

Fig. 7.1.

Unfortunately, current pulses from electrons formed by small energies and γ-quanta particles are very small. It is difficult to accurately measure, therefore ionization chambers are used to register heavy particles, for example, α-particles that are formed by passing through the ionization chamber significantly large current pulses.

If you increase the voltage at the electrodes of the ionization chamber, then the phenomenon arises called gas amplification. Free electrons, moving in an electric field, acquire energy sufficient to ionize the gas atoms filling the chamber. When ionization, the electron forms another pair of ion is an electron, so that the total charges are multiplied by two, as shown in Fig. 7.2. In turn, the new-forming electrons are also capable of ionization, and thus the charge is multiplied yet. With a special form of electrodes, the gas amplification coefficient can reach 105. The fact that the final charge remains proportional to the primary, and therefore the electron energies formed by a particle or γ-quantum. It is for this reason that such devices are called proportional counters.

Usually, the proportional counter is made in the form of a cylinder, along the axis of which stretch the fine metal wire - thread. A negative connection is connected to the meter housing, and the thread is a positive pole of the current source. With such a device, the electric field focuses mainly near the thread and the maximum value of the field strength turns out to be the higher the lower the radius of the thread. Therefore, the large field strengths necessary for gas gain can be obtained with relatively small differences between the potentials between the meter housing and the thread.

Fig. 7.2.

Proportional counters were widespread due to their simplicity and high current pulses during the passage of charged particles. Now proportional counters are mainly used to register β-radiation, soft γ-radiation, α-particles and neutrons. In fig. 7.3 The main types of proportional counters are presented.

Fig. 7.3.

In the electrical circuit, the proportional counter turns on the same way as the ionization chamber. And the electrical impulses from it are obtained are the same as from the camera, only more than the magnitude. It would seem, it is worth only to apply enough high voltageSo that gas gain was more, and the proportional counter will give so large impulses that it will be possible to work with them without further strengthening. However, in fact it is not. The fact is that with large gas gains, the counter begins to work unstable and the proportionality between the particle energy and the amplitude of the pulse is broken.

To avoid the appearance of breakdowns and level the electric field, the counter has to be done very carefully, testing and polishing its electrodes. Polish the thread, the diameter of which is measured by hundredths of the millimeter, is very difficult. If the electric field in the counter is inhomogeneous along the thread, the pulse will depend not only on the particle energy, but also from the place of its hit in the counter, which is naturally undesirable.

Therefore, the design of the proportional meter often has to complicate, introducing additional electrodes to it to align the field. As a result of all these complications, it is possible to make meters with gas strengthens in tens, hundreds, and sometimes even thousands of times, but it often turns out to be too little so that with the pulses obtained from them it was possible to work without subsequent gain.

Consider what happens if you even more increase the voltage between the counter electrodes. In this case, when the charged particle is hit in the counter, an extremely powerful avalanche of electrons is formed, which at high speed fell on a positive electrode and knocks out several photons from it - ultraviolet radiation quanta.

These photons falling on a negative electrode can snatch new electrons, the latter will again rush to the positive electrode, etc. As a result, a so-called independent discharge occurs in the meter, which will burn with constant force regardless of whether new particles fall into the meter or not. (Exactly the discharge in neon tubes of light advertising is burning.)

The meter should react to each particle that falls into it, so such a work mode is not needed. However, applying special inclusion schemes or adding some heavy gases to the atmosphere of the counter, you can create conditions under which the independent discharge occurred in the particle counter in itself will go through a very short time. Thus, the hit in the counter of each new particle will cause the appearance of a short-term, but rather strong current.

The most common detector (sensor) of ionizing radiation operating in the mode described above is steeker meter - Muller. The principle of its work is based on the occurrence of a discharge in gas with the span of ionizing particles. In a well-vacuumed sealed cylinder with two electrodes, which is under voltage, introduced gas mix, consisting mainly of easily ionized neon and argon (the device should register β- and γ-radiation). The balloon can be glass, metallic, etc. Usually the meters perceive radiation with its entire surface, but there are also those that have a special "window" in the balloon.

High voltage applied to electrodes U. (Fig. 7.4), which in itself does not cause any discharge phenomena. In this state, the meter will remain until the ionization center appears in its gas environment - a trace of ions and electrons generated by the ionizing particle from the outside. Primary electrons, accelerating in the electric field, ionize "on the way" other gas media molecules, generating all new and new electrons and ions. Developing avalanche-like, this process is completed by the formation of an electron-ion cloud in the interelectrode space, sharply increasing its conductivity. In the meter's gas environment, there is a discharge, visible (if a transparent balloon) is even a simple eye.

Fig. 7.4.

The reverse process is the return of the gas environment into its initial state in the so-called halogen counters - is due to itself. Halogens are taken into effect (usually chlorine or bromine), in a small amounts contained in a gas environment that contribute to intensive recombination of charges. But this process is much slower. The length of the time required to restore the radiation sensitivity of the gameger meter and actually determining its speed - the "dead" time is an important passport characteristic. For example, for a gas-discharge meter of Geiger - Muller, such as SBM-20-1 "Dead" time U. \u003d 400 V is 190 p / μs.

Geiger counters are able to respond to the most different types Ionizing radiation - alpha, beta, gamma, ultraviolet, x-ray, neutron. But the real spectral sensitivity of the meter largely depends on its design.

The amplitude of the impulse from the meter of Geiger - Muller can reach several dozen or even cell volts. With such pulses, you can work without any strengthening. But this victory was conquered by an expensive price. The fact is that the amplitude of the pulse in the Geiger - Muller counter is determined only by the properties of the meter itself and the parameters of the electrical circuit and does not depend on the type or on the energy of the primary particle.

The pulses from the slow electron, which created only a few pairs of ions, and from the α particle, which created several thousand ions, turn out to be the same. Therefore, Geiger - Muller counters can only be used to calculate the number of flights flying particles in homogeneous radiation fields, but not to determine their type and energy.

Radiation safety and degree of pollution ambient It was not disturbed by many citizens of the countries of the world until there were no catastrophic events that took the lives and health of hundreds and thousands of people. The most tragic in terms of radiation pollution was Fukushima, Nagasaki and the Chernobyl catastrophe. These territories and related history are stored in the memory of each person so far and are a lesson that, regardless of the foreign policy and level financial well-being About radiation safety is always worried. It is necessary to know, to register which particles the gamer counter is applied, what kind of prevention measures should be applied if a disaster happens.

What is the gamer counter? Due to multiple technogenic catastrophes and a critical increase in the level of radiation in the air over the past few decades, humanity has invented and invented unique and most convenient instruments for registering particles using a gameger meter and industrial use. These devices make it possible to measure the level of radiation pollution, as well as static controlling the situation of pollution on the territory or locality, given the weather conditions, geographical location and climatic differences.

What is the principle of action of the gameger meter? Today, to purchase a dosimeter of household type and the device of the Geiger meter can have anyone who wishes. It should be noted that in the conditions of the fact that radiation can be both natural and artificial typeThe person is obliged to constantly follow the radiation background in his house, as well as to know exactly what particles register the gamer counter, about methods and methods of preventive protection against ionizing substances and. Due to the fact that radiation cannot be seen or felt by a person without special equipment, many people can be in the state of infection for a long time, without suspecting it.

What radiation do you need a gamer counter?

It is important to recall that radiation can be different, it depends on which charged particles it consists and how far has spread from its source. Why do you need a gamer counter? For example, alpha-particles of radiation are not considered hazardous and aggressive in relation to the human body, however, with prolonged exposure, they can lead to some forms of diseases, benign tumors and inflammation. Beta radiation is considered as dangerous and destructive for human health. It is to measure such particles in the air that the principle of operation of the Geiger meter is directed.

Beta charges can be produced both artificially as a result of the operation of nuclear power plants or chemical laboratories and natural, due to volcanic rocks and other underground sources. In certain cases, the high concentration in the air of the ionizing elements of beta-like can lead to cancerous agers, benign tumors, infections, discontinuities of mucous membranes, disorders of the thyroid gland and bone marrow.

What is a gamer meter and how does the gamer counter work? This is called a special device that are equipped with dosimeters and radioometers of household and professional type. The Geiger counter is a sensitive element of the dosimeter, which, under the conditions of configuring a certain level of sensitivity, helps reveal the concentration in the air of ionizing substances for the allotted period of time.

The meter of Geiger, whose photo was shown above, was first invented and tested in practice at the beginning of the twentieth century by scientist Walter Muller. The advantages and disadvantages of the gamer counter can also evaluate the current generation. This device Widely applied in everyday life for and industrial sphere to the present. Some craftsmen even make the gamer counter with their own hands.

Improved radiation dosimeters

It should be said that since the invention of the meter of Geiger and Dosimetra to the present days these universal devices There were many stages of improvement and modernization. Today, such devices can be used not only to check low radiation background indicators in domestic conditions or production, but also use more optimized and improved models that help measure the level of radiation at nuclear power plants, as well as in the process of hosting hostilities.

Modern methods Applications of the Geiger meter make it possible to capture not only the total number of ionizing substances in the air for a certain period of time, but also react to their density, degree of charge, the type of radiation and the nature of the effect on the surface.

For example, the purpose of the gamer counters for household needs or personal use does not provide for the need for upgraded capabilities, since they are usually applied to household use And serve to test the radiation background in the house, food, clothing or building materials that can potentially contain a certain level of charge. However, industrial and professional dosimeters are necessary in order to check more serious and complex radiation radiation and serve as a permanent method of controlling the radiation field at nuclear power plants, chemical laboratories or nuclear stations.

Order a free consultation of the environmentalist

Given the fact that many modern countries today have a potent nuclear weapon today, have professional dosimeters and Geiger counters every person on the planet so that in the event of an emergency and disaster to be able to check the radiation field and save their lives and the lives of their loved ones. It is also useful to study the pros and cons of the Geiger counter.

It is worth saying that the principle of operation of the Geiger counters provides a reaction not only to the intensity of the radiation charge and the number of ionizing particles in the air, but also allows you to separate alpha radiation from beta radiation. Since beta-radiation is considered as aggressive and potent with its charge and the concentration of ions, the Geiger counters for its check are covered with special lead clamps or steel to cut off extra elements and not damage equipment when checking.

The ability to cut off and separate various streams of radiation type allowed many people today qualitatively use dosimeters, to maximally calculate the danger and the level of pollution of one or another territory with radiation elements of various nature.

What is the gamer counter?

Where does the gamer counter apply? As mentioned above, the gamer counter is not separate element, but serves to be the leading and main element in the dosimeter design. It is necessary for the highest possible and accurate check of the radiation background in one area or another.

It should be said that the Geiger Counter has a relatively simple device scheme. In general, its design has the following features.

The Geiger Counter is a small container inside which contains inert gas. As a gas, various manufacturers use different elements and substances. Maximum often, Geiger meters are produced with cylinders filled with argon, neon or mixtures of these two substances. It is worth saying that the gas that fills the meter's balloon is under minimal pressure. It is necessary so that there is no voltage between the cathode and the anode and the electrical impulse has occurred.

The cathode is the design of the entire meter. Anode is a wire or metal connection between the cylinder and the main design of the dosimeter, which is connected to the sensor. It should be noted that in some cases an anode that directly reacts to radiation elements can be manufactured with a special protective coating that allows you to control ions penetrating the anode and affecting the final measurement indicators.

How does the gamer counter work?

After we found out the main points of the geiger counter design, it is worth describing a brief principle of action of the Geiger meter. Given the easiability of its arrangement, its work and functioning is also extremely easy to explain. The Geiger Counter works for this principle:

When the dosimeter turns on between the cathode and the anode there arises an increased electrical voltage using a resistor. However, the voltage cannot subscribe during work due to the fact that the meter cylinder is filled with inert gas.
When the charged ion falls on the anode - it begins to mix with inert gas to ionize. Thus, the radiation element is fixed using the sensor and can influence the indicators of the radiation background in the area being checked. The end of the check usually signals the characteristic sound of the Geiger counter.

As mentioned above, some anodes for gamer counters are produced from special coating. Such measures are necessary in order for the counter to capture as much as possible only beta radiation and reacted to the most dangerous human organism Charged particles.

With the help of a modern heiger counter, you can measure the level of radiation building materials, land plot or apartments as well as food. It demonstrates the almost one hundred percent probability of a charged particle, because for its fixing is enough only one pair of electron-ion.

The technology based on which a modern dosimeter was created on the basis of the Geiger Muller counter, allows to obtain high accuracy results in a very short period of time. No more than 60 seconds are required for measurement, and all information is displayed in graphical and numeric form on the dosimeter screen.

Setting the device

The device has the ability to configure the threshold when it is exceeded, a beep, warning you about danger. Select one of the specified threshold values \u200b\u200bin the appropriate section of the settings. A beep can also be turned off. Before measuring, it is recommended to hold individual setting instrument, select the brightness of the display, the parameters of the audio signal and batteries.

The procedure for performing measurements

Select the "Measurement" mode, while the device starts an assessment of the radioactive situation. After about 60 seconds, the measurement result appears on its display, after which the following analysis cycle begins. In order to obtain an accurate result, at least 5 measurement cycles are recommended. An increase in the number of observations gives more reliable readings.

To measure the radiation background of objects, such as building materials or food products, you need to turn on the "Measurement" mode at a distance of several meters from the object, then bring the device to the subject and measure the background as close as possible to it. Compare the readings of the instrument with the data obtained at a distance of several meters from the subject. The difference between these indications is an additional radiation background of the object under study.

If the measurement results exceed the natural background, characteristic of the terrain in which you are, this indicates the radiation pollution of the object under study. To assess the pollution of the fluid, it is recommended to measure over its open surface. To protect the device from moisture, it needs to be wrapped polyethylene filmbut not more than one layer. If dosimeter for a long time was at temperatures below 0 ° C, before measuring it must be kept with room temperature For 2 hours.

The heiger counter is a prototype of modern dosimeters or, as they are also called radiometers. Using a small-sized and simple device, you can find out the level of radiation even before it affects human health.

What measures the gamer counter?

Using the device, the level of radiation radiation of objects and objects is determined:

Construction Materials
Land plot
Room
Resting-place
Food
Vehicles
Houseware
clothing
Cosmetics
Kids toys

How to use a dosimeter?

Average radioactivity indicators recognized by Safe: 20-30mk / hour. Normal radiation background - 0.22 μSV / hour. To measure the radiation level, you must first turn on the device and reset the display readings. The study itself takes no more than 60 seconds. During the examination, it is necessary to carefully monitor the cleanliness of the device itself, since the smallest dust or moisture may affect the accuracy of the testimony. Therefore, the device is recommended to use in a protective case.

Determine the level of radiation in products

Fruits and vegetables brought from the market, forest mushrooms And berries may not be safe to health. Dosimeter dispels all doubts - for this you need to bring the included instrument to products (without packaging and weighing up to 1 kg) at a distance of 1-5 cm. You can also find out the level of radiation in drinking water, milk, other liquid products. Measurement is carried out above an open container with liquid. The instrument readings may be slightly higher when measuring radiation in tea or dried mushrooms, since they are concentrated composition of trace elements.

Measurement of radiation in the dwelling

To check the level of radiation in the room, you need to walk with the device along the walls and as close as possible to the floor. For residential premises, 25MKR \\ h is considered to be a normal level of radiation. The figure of 30mkr / hour is an extremely permissible rate for homes, during the construction of concrete, granite, crushed stone. It is important to measure in different places At home, as the hidden source of hazardous radiation can be furniture, vintage things, rare technique. It is worth considering that bricks can testify radioactivity 2 times more permissible norm. Therefore, the fireplace or oven is measured at a distance of 40-50cm.

Measuring the level of radiation in the open space

The source of radiation can be precipitation, wind from enterprises, plants, stones or ordinary sand at the playground. Dosimeter allows S. high accuracy Determine the source of radiation. This is especially important when choosing a place to build a house, relaxation or just walking through a megalopolis. An estimate of the level of radiation is carried out at a distance of 1m from the soil and 0.5 m from the buildings.

Due to the fact that after the Chernobyl NPP disaster, the dosimeters became very popular in our country, there were a lot of fakes and not high-quality devices in the markets. The most reliable seller for health care is a specialized "honey shop".

Seven reasons why the dosimeter must be purchased in a honeycoming:

The 1st company cooperates with official representatives of famous brands

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The 5th purchase is issued on the Med-Shop website, without leaving home.

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The 7th online technical support service.

The Geiger Counter (Geiger Muller) is a gas-discharge device for an automatic count of the number of ionizing particles in it. It is a gas-filled capacitor, which breaks through when the ionizing particle is span through the gas volume. The meter was invented in 1908 by Hans Heiger and improved by Muller. It is the most common detector (sensor) ionizing radiation. Until now, it was invented at the very beginning of the last century for the needs of the emerging nuclear physics, no, oddly enough, any full-fledged replacement.

Additional electronic circuit Provides a meter meter (as a rule, at least 300 V), it provides, if necessary, quenching the discharge and counts the number of discharges through the counter.

Geeger counters are divided into unauthorized and self-sustainable (do not require external discharge termination schemes).

The sensitivity of the counter is determined by the composition of the gas, its volume, as well as the material and the thickness of its walls.

Most often in devices apply the counter with a working voltage of about 400 V, such as:

1. "SBM-20" (in size ї slightly thicker pencil).

2. "SBM-21" (both with steel corps suitable for measuring beta and gamma radiation).

3. "Si-8B" (with a mica window in the case, suitable for measuring beta radiation).

The Geiger Muller Cylindrical Counter consists of a metal tube or metallized from the inside glass tube, and fine metal threads stretched along the axis of the cylinder. The thread serves as an anode, a tube - cathode. The tube is filled with sparse gas, in most cases noble gases are used - argon and neon. Between the cathode and anode creates a voltage of order 400 V. For most counters, there is a so-called plateau, which lies from about 360 to 460 V, in this range, small voltage fluctuations do not affect the account speed.

The counter of the counter is based on shock ionization. Gamma quanta emitted by the radioactive isotope, falling on the walls of the counter, knocked out of it electrons. Electrons moving in gas and facing gas atoms are knocked out from atoms electrons and create positive ions and free electrons. Electric field Between the cathode and the anode accelerates electrons to the energies at which the impact ionization begins. An avalanche of ions arises, and the current across the counter sharply increases. At the same time, the voltage pulse is formed on the resistance, which is fed to the registering device. So that the counter can register the next particle that fell into it, the avalanche discharge must be repayed. This happens automatically. At the time of the current pulse, a large voltage drop occurs on the resistance, so the voltage between the anode and the cathode decreases sharply - so much that the discharge stops, and the counter is ready to work again.

An important characteristic of the counter is its effectiveness. Not all gama-photons that have fallen on the counter will give secondary electrons and will be recorded, since the acts of interaction of gamma rays with substance are relatively rare, and some of the secondary electrons are absorbed in the walls of the device without reaching the gas volume.

The effectiveness of the counter depends on the thickness of the walls of the meter, their material and the energy of gamma radiation. Counters, the walls of which are made of material with a large atomic number z, as the formation of secondary electrons increases with the greatest efficiency.

Note. Atomic number, Z ї This is the sequence number chemical element In the periodic system of elements D. I. Mendeleev. Atomic number equal to the number Protons B. atomic nucleuswhich, in turn, is equal to the number of electrons in the electron shell of the corresponding neutral atom. The nucleus charge is ze, where e is a positive elementary electrical charge equal to an absolute value of the electron charge.

In addition, the walls of the meter must be quite thick. The thickness of the meter wall is selected from the condition of its equality of the length of the free mileage of secondary electrons in the wall material. With a large wall thickness, secondary electrons will not pass into the working volume of the meter and the current pulse occurs. The SG has its own minuses ї for the reaction of such a device. It is impossible to judge the root cause of its excitement. The output pulses generated by the SG under the action of alpha particles, electrons, the gamma quanta do not differ.

We give some passport data, on the example of the SBM 20 counter.

· Nominal working voltage ї 400 V.

· The length of the plateau of the counting characteristics of at least 100 V.

· Changing the sensitivity of the meter during the entire resource does not exceed.

· Own background ї no more than 1 pulp.

· Impulse amplitude of at least 50 V.

· Range of registered capacities ї (0.001 ... 10) MKP / s.

· Sensitivity to radiation ї 460 imp / s.

Fig. 1.1 Ї Dependence of the speed of the account of supply voltage

Fig. 1.2. Ї Dependence of the rate of account of radiation