How does a personal dosimeter work? Radiation dosimeter, household or professional

Today, the word “radiation” sounds scary to residents around the globe. And back in the 20s of the last century, “Young Chemist” sets with uranium samples were sold in American children’s toy stores. And in 1929, Borjomi advertising posters emphasized the radioactivity of mineral water as its undoubted health benefit.

Radiation is the ability of physical bodies to distribute light or thermal energy around themselves. Radiation is a general concept that may imply different types radiation. Some of them are natural: from the earth’s crust, the Sun, space; the rest are humanity’s retribution for technological progress.

The level of natural influences is safe for human health. It is not felt by the body and does not entail harmful consequences. But high doses of artificial radiation cause irreversible changes in the body, including the development of such serious diseases as radiation sickness, leukemia, tumors, and reproductive system disorders.

Unfortunately, accidents involving the release of radiation are not that uncommon. At the end of November, there was information that a month ago a strong excess of background radiation was discovered in the Southern Urals.

Of course, it is almost impossible to receive a dose in everyday life that can lead to death, but slow and systematic exposure leads to an exacerbation of chronic diseases. Under the influence of radiation, a person’s blood composition deteriorates, the skin, nails, and hair suffer.

Scientists no longer doubt that it is radiation that causes the most unexpected mutations at the gene level. And the worst thing is that radiation has a particularly strong effect on children, whose bodies cannot yet fully resist the threat.

Where radiation can occur and how to detect it

The main man-made sources of radiation are nuclear weapons, nuclear power plants, industrial waste, items from emergency exclusion zones, and some types of medical equipment. The list of particularly dangerous objects includes scanners at airports, X-ray machines and even cigarettes and bananas, which contain naturally occurring radioactive isotopes.

Since radiation is an invisible, inaudible and intangible enemy, the only way to detect it is to purchase a dosimeter.

A dosimeter is a device that allows you to measure the level of radiation around or in individual objects. Its main element is a radioactivity sensor, the type and characteristics of which determine the accuracy and speed of data acquisition.

East Ural radiation trace after the Kyshtym accident

Dosimeters allow you to solve several problems at once:

choose a safe place to rest, work, live;
purchase a car and equipment that will not harm the health of household members;
test an office, manufacturing plant, warehouse;
check building materials, furniture, other interior and household items;
check the safety of children's products and toys;
control the environmental friendliness of food products;
find out the dose of radiation accumulated in the body.

What types of radiation dosimeters are there?

Detector. The best ones are gas-discharge meters. The most common of them is Geiger-Muller. Semiconductor detectors are less accurate.
Type of radiation . Modern multifunctional models can measure several types of radiation at once.
Error . Any measuring device has its own accuracy.
measurement range . If the maximum threshold is high enough, it can be ignored, but the minimum recorded value of a particular device cannot be ignored.
Convenience . The dimensions and shape of the model, the interface, the presence of various indicators - all these are indicators that affect the ease of use of the device.

But the most important thing to pay attention to is whether the device belongs to professional or household dosimeters. Their main difference is that professional instruments are registered in the unified State Register of Measuring Instruments. Besides:

household appliances undergo one-time lightweight tests. Professional – systematic and strict, with the issuance of a Certificate of Compliance with state standards;
for household dosimeters the average error is from 30%, professional dosimeters do not go beyond 15-30%;
verification of household dosimeters is optional, but professional dosimeters are controlled by accredited state laboratories;
readings from household dosimeters do not have formal legal force and are not considered objectively reliable, unlike professional ones.

How to take measurements?

It is not enough to purchase a suitable dosimeter. To obtain objective readings, you must also adhere to all the rules for taking measurements. And if everything is in order with determining the general radiation background of the room, then it is more difficult to assess how safe this or that object is. The procedure for carrying out measurements in in this case is:

Measure the background a few meters from the object to be tested. Measurement time – up to 1 minute.
Bring the indicator as close as possible to the object being measured. Take measurements literally a few centimeters from the object.
Subtract the first from the second result to obtain the radiation indicators of the object, without taking into account the background.

As for background radiation, it is quite natural for a large city to be 8-12 µR/h outdoors and 15-20 µR/h indoors. In this case, the permissible rate is a maximum of 30 μR/h.

Depending on the dosimeter model, the nuances of the measurement process may differ slightly. Therefore, each device comes with detailed instructions, which is a must-follow!

But in any case, the user needs to ensure that the sensors are always clean. They should be free of dust and other particles that could affect the accuracy of the readings.

At the everyday level, three types of radiation are important: alpha, beta and gamma. All of them are dangerous for living organisms:

alpha radiation is the spread of heavy particles. Even an ordinary sheet of paper can protect against them, so during external irradiation, for example, from objects, alpha particles do not pose a serious danger. But if you consume contaminated water or food, the damage to your health will be enormous;
beta radiation represents a flow of low penetrating electrons. Such irradiation is dangerous precisely when exposed to external influences, for example, through contact. An aluminum sheet can protect against beta rays;
gamma radiation - This electromagnetic radiation, which pierces the human body right through. You can only protect yourself from it with a thick layer of lead or concrete.

Only some of the dosimeters allow you to check a room for 3 types of radiation at once. Most often, manufacturers focus on gamma rays as the most dangerous, but also the easiest to detect.

Brief overview of radiation measuring instruments

Today, several models of dosimeters are in particular demand:

One of the best household dosimeters Radiascan 701

RadiaScan . Household appliance. Measures all three types of radiation. Made on the basis of a highly sensitive professional counter. Equipped with a high contrast display powerful processor, sound and light indication. Connects to a computer and allows you to keep an event log.
SOEKS Quantum – a professional dosimeter, equipped with two Geiger counters for accuracy and speed. Included in the State Register, tested in an accredited laboratory. Highly accurate and multifunctional, but at the same time quite affordable, understandable and easy to use.
Radex . A classic portable individual dosimeter based on a gas-discharge Geiger-Muller counter. Fast, compact and intuitive. Works in a wide temperature and humidity range.

and this is a professional dosimeter Soex Quantum

Each of these devices can help protect your family from harmful radiation exposure. And finally, a couple of tips: powerful radiation is most likely to be detected near household and medical equipment; granite and other natural building materials, precious stones, pottery and antiques are highly emitted.

Dosimeter

Outdated household dosimeter-radiometer "Sosna" (USSR, 1992). The battery compartment is slightly open. Shows 16 microroentgen/hour.

Dosimeter- a device for measuring the effective dose or power of ionizing radiation over a certain period of time. The measurement itself is called dosimetry.

Sometimes a “dosimeter” is not quite accurately called radiometer- a device for measuring the activity of a radionuclide in a source or sample (in a volume of liquid, gas, aerosol, on contaminated surfaces) or the flux density of ionizing radiation to check for radioactivity of suspicious objects and assess the radiation situation in a given place in this moment.
The measurement of the above quantities is called radiometry.

Household appliances, as a rule, are combined, have both operating modes with switching between “dosimeter” and “radiometer”, light and (or) sound alarms and a display for reading measurements. The weight of household appliances ranges from 400 to several tens of grams, the size allows you to put them in your pocket. Some modern models Can be worn on your wrist like a watch. Time continuous operation from one battery from several days to several months.

The measurement range of household radiometers is usually from 10 to 10 thousand microroentgen per hour (0,1 - 100 microsievert per hour), measurement error ±30%.

In the USSR, household dosimeters became most widespread after the Chernobyl accident in 1986. Until this time, dosimeters were used only for scientific or military purposes.

Counters for whole body dosimetry

BOMAB

Bomab (The BOttle MAnikin Absober) is a phantom developed in 1949 and has since been adopted in North America, if not throughout the world, as the industry standard (ANSI 1995) for calibrating dosimeters used for whole body counting. .

The phantom consists of 10 plastic bottles, either cylinders or elliptical balloons, which are its head, neck, chest, abdomen, thighs, legs and arms. Each section is filled with a radioactive solution in water, the radioactivity of which is proportional to the volume of each section. This simulates a uniform distribution of material throughout the body.

Examples of radioactive isotopes used to calibrate calibration efficiency: edit] Pulmonary counter

Lung Counter - a system designed to measure and count radiation from radioactive gases and aerosols inhaled by a person and insoluble enough in body tissue to leave the lungs over several weeks, months or years. Consists of a radiation detector or detectors and associated electronics. The detectors imitate the shape, density and chemical composition of the tissue of the lungs and surrounding organs. The cavities in the detectors are filled with the radioactive gas or aerosol being studied. Often such a system is located in the lower floors of premises (to protect against the hadronic component of the cosmic background) and is surrounded by protection from background gamma radiation (thick walls made of steel, lead and other heavy materials) and neutron radiation (cadmium, boron, polyethylene).

Since the pulmonary counter is primarily used to measure radioactive substances that emit low-energy gamma or x-rays, the phantom used to calibrate the system must be anthropometric. Such a phantom of a human torso was developed, for example, at the Lawrence Livermore National Laboratory. E. Lawrence (Torso Phantom).

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Synonyms:

See what “Dosimeter” is in other dictionaries:

Dosimeter… Spelling dictionary-reference book

dosimeter- A device or installation for measuring ionizing radiation, designed to obtain measurement information about the exposure dose and exposure dose rate of photon radiation and (or) about the energy transferred by ionizing radiation... ... Technical Translator's Guide

dosimeter- a, m. dosimètre m., German. Dosimeter. A device for measuring the dose of radioactive radiation. Photoelectric dosimeter. Personal dosimeter. ALS 2. Today we are frightened by everything in the world, But it is quite possible to survive these days. And I live: I wear a bulletproof vest,... ... Historical Dictionary of Gallicisms of the Russian Language

DOSIMETER- (D.) a device for monitoring radiation exposure. There are two fundamentally different types D.: D., measuring the dose accumulated over a certain time of stay in conditions of increased radiation loads, and D., showing the excess of the permissible ... Ecological dictionary

dosimeter- and an outdated dosimeter... Dictionary of difficulties of pronunciation and stress in modern Russian language

DOSIMETER, a device for measuring radiation dose or related quantities. There are dosimeters for one type of radiation (for example, neutron dosimeters, g dosimeters) and for mixed radiation. The main parts of the dosimeter are the particle detector and... ... Modern encyclopedia

DOSIMETER, a device for measuring the dose of RADIATION, usually a pocket ELECTROSCOPE. The quartz fiber is charged and then viewed against a scale. The measure of its deviation during irradiation corresponds to the level of radiation it... ... Scientific and technical encyclopedic dictionary

Exist., number of synonyms: 5 biodosimeter (1) gamma dosimeter (1) microdosimeter ... Synonym dictionary

Ionizing radiation dosimeters are instruments designed to measure the dose value or dose rate of ionizing radiation. Instruments that measure the dose rate of ionizing radiation are also called X-ray meters. Ionizing radiation dosimeters operate by taking into account the ionizing or luminescent properties of radiation (see Dosimetry). Basic integral part Ionization radiation dosimeters are an ionization chamber or a gas-discharge tube with a limited volume of gas or air. Electrodes are located in the wall of the chamber or tube, as well as in its center. In the normal state, molecules and gases are electrically neutral, so when a potential difference is applied to the electrodes, no electric current passes through the chamber.

Set for individual dosimetric monitoring: 1 - charging and measuring panel; 2 - individual ionization chambers; 3 - storage box.

If such a chamber is placed in the zone of action of ionizing radiation, then gas ionization occurs in it with the formation of positively and negatively charged ions, which, after applying a potential difference, will move directionally to the electrodes of the opposite sign. The current resulting from the directional movement of ions in the chamber is called ionization and can be measured with a special device - a galvanometer or microammeter. Under certain conditions, the ionization current is proportional to the number of ions and depends on the amount of radiation dose absorbed in the chamber. In gas-discharge tubes, unlike ionization chambers, electrons generated by exposure to radiation acquire greater energy and, in turn, cause the ionization of other gas molecules and atoms. In this regard, the primary ionization of gas due to exposure to radiation is significantly enhanced and, therefore, it is possible to register very small doses of ionizing radiation.

Dosimeters based on the principle of recording the glow that occurs during the transition of an atom from an excited to a non-excited state upon irradiation of certain substances (luminophores) are called luminescent or scintillation. Light flashes in phosphors can be recorded by special photomultipliers (PMTs). Light flashes in them are converted into electrical impulses, which are recorded by counting devices. Dosimeters of ionizing radiation of all types have, in addition to the sensor (ionization chamber, gas-discharge tube or phosphor), power supply, conversion and recording devices. The sensor can be mounted in one block with converting and recording devices. Some sensors are small and designed to be inserted into body cavities, such as the mouth or bladder. Such sensors are subjected to or enclosed in rubber balloons before insertion.

The power supply device is designed to apply a potential difference to the electrodes. Portable ionizing radiation dosimeters have power sources direct current in the form of dry elements. Clinical dosimeters of ionizing radiation are connected to the electrical network. Before measurements, it is necessary to warm up the instruments well for 20-30 minutes in order to obtain stable measurement values. To measure the X-ray radiation dose rate, it is necessary to install a sensor in the center of the working radiation beam.

The converting device converts the primary radiation effect into electrical impulses. The recording device is a pointer device, graduated either in dose units or in dose rate units, i.e., in roentgens, milliroentgens, microroentgens (r/hour, r/min, mr/hour, microroentgen/sec). Ionizing radiation dosimeters have several measurement ranges, which are set immediately before the study. Measurements begin with the maximum range and gradually select the range that corresponds to this particular case.

Based on their intended purpose, ionizing radiation dosimeters used in medical practice can be divided into four groups.
1. X-ray meters. Designed for measuring therapeutic doses of X-ray and (condenser dosimeter KD and KDM, X-ray meters RM-1 and integral medical dosimeter DIM).

2. Micro-radiometers for measuring radiation dose rate at personnel workplaces (MRM-2) and in adjacent rooms (“Sputnik”, “Crystal”).

3. Dosimeters for determining the dose of individual exposure to personnel (KID-2 and ID-2). In Fig. the most common ionizing radiation dosimeter for individual dosimetric monitoring is presented.

4. Radiometers for determining the level of radioactive contamination of premises and equipment (TISS and LUCH). These devices are not dosimeters themselves, but their readings make it possible to determine the dose value by calculation.

When working with ionizing radiation dosimeters, the following rules must be observed.
1. Protect from shock, transport only in packing boxes, store in a dry place.

2. Start working with ionizing radiation dosimeters only after first studying the operating instructions for the device.

3. Be sure to turn off the device after use.

4. Periodically calibrate ionizing radiation dosimeters according to standard standards in special testing laboratories and record the calibration results in the instrument passport.

5. Use ionizing radiation dosimeters only for their intended purpose - to measure a certain quality of radiation when certain values dose value or radiation dose rate.

Classic dosimeters belong to a group of devices through which it is possible to measure the so-called “equivalent” radiation dose over a certain time interval. In this case, the process of taking such readings is usually called dosimetry.

Sometimes a dosimeter is mistakenly understood as devices of a similar class, called radiometers. The latter are intended to determine the activity of radioactive elements in specific samples or sources of penetrating radiation. The process of measuring these indicators is called radiometry. Before choosing a radiation dosimeter, you need to familiarize yourself with the design of these products, as well as the main areas of their application.

Composition of the device and its purpose

The main functional element of a dosimeter is a detector, or a sensitive radiation sensor, designed to convert the flow of ionizing radiation into one form or another accessible for visual representation and observation.

The function of such a detector can be performed by the following sensitive elements or devices:

Ionization chamber used to determine the intensity of hazardous radiation;
A scintillator designed to record radioactive background in the area;
Geiger counter used to monitor the level of exposure to individual particles.

As a rule, individual dosimeters are equipped with an ionization chamber, which in appearance resemble a fountain pen with a window located at the end.

Note! Dosimeters equipped with such a sensitive element are sold under the designations “DDGN” or “DDG”.

The second type of sensor is a scintillator, most often found in specialized instruments that measure radiation. They are produced under the designation "SRP-88" and are usually used in geological exploration. And finally, Geiger counters are installed in military models of radiometers of the “DP-12” type, as well as in household devices of the combined class (“Pripyat”, “Bella”, “Expert”, “Sosna”).

In our country, individual household radiation meters have been widely used since the accident at the Chernobyl nuclear power plant, when thousands of people were exposed to dangerous radiation. Before the events of 1986, they were used only for purely scientific or military purposes.

Types of dosimeters

In order to get a complete understanding of what a dosimeter is, first of all, you should familiarize yourself with the existing types of these recording devices. According to their purpose, all well-known brands of dosimetric devices are divided into professional and household samples. Let's look at each of these categories in more detail.

Professional devices

This class of dosimeters, in addition to its main purpose, can be used as a radiometer that is capable of monitoring the presence and measuring the quantitative content of radionuclides in liquids, gases, as well as in any other material media.

Universal dosimetric instruments can be used for the following purposes:

Determination of the intensity of the flow of ionizing radiation;
Checks for the degree of radioactive contamination of various substances and objects;
Assessment of the current radiation situation in specific areas.

When using these modern devices Based on the type and energy spectrum of the detected radiation, it is possible to draw a conclusion about the class of the isotope. In addition, most devices for measuring background radiation have a separate detector that allows you to record alpha particle radiation.

Household dosimeters

An ordinary household appliance most often has a combined design, suggesting the presence of two operating modes at once (as a radiometer and as a dosimeter) with the ability to switch between them. In addition, such products are equipped with a built-in alarm system, and the measurement results are displayed on a special digital display.

The weight of household models usually does not exceed 400 grams, and their dimensions allow them to be carried in the pockets of work clothes.

Additional Information. Some of the more advanced examples of such devices can be worn on the wrist like a regular watch. Their continuous operation time from a conventional battery without recharging can range from several hours to a month (depending on the frequency of switching on).

The measurement range of the controlled parameter is for most samples of home dosimeters from 10 to 10,000 microroentgen per hour, and the permissible error in determining radiation does not exceed ±30%. The high relative error does not prevent these devices from successfully testing building materials and food imported from unknown sources for contamination. In addition, with their help it is possible to control the radiation situation in a suburban area and around the house with relative accuracy.

Other types of recording devices

In addition to the classification considered, dosimeters differ in the specifics of their application, according to which they can be presented:

Individual-type devices (they record the dose accumulated by one person);
Industrial models used directly at a hazardous facility (at a nuclear power plant, for example). These products are intended for continuous dosimetric assessment of the air environment and its constant monitoring;
Samples of products for military needs, designed for operation in critical conditions (including damage to the area by a nuclear explosion).

Interesting. All these types dosimetric instruments For obvious reasons, they are not put on free sale.

Features of the device and choice of household dosimeters

A radiation measuring device, or dosimeter, is designed to register the following types of hazardous radiation:

Beta and alpha particles;
Gamma rays;
Modifications of alpha and beta particles called “hard” or “soft” radiation.

In the cheapest models used to detect these particles, the sensor function is performed by a special isotope-sensitive diode. And in more “advanced” middle-class dosimeters, a set of several gas-discharge counters is used to detect radiation. The most expensive and prestigious examples of this technology can install scintillators made in the form of a crystalline element.

In order to correctly select a dosimeter model suitable for specific conditions, you should know that the number of recording elements can vary from one to 4 pieces. The configuration features of modern meters and dosimeters should be carefully studied before purchasing them.

Important! Particular attention is usually paid to the presence of a color display, as well as the ability to connect to personal computer via USB input connector.

Attention is also drawn to the presence and quality of the sound indicator, the design options of which can be very diverse. This can be a simple speaker, also called a “squeaker,” or a built-in voice simulator that announces measurement results in the selected language.

How to use the dosimeter

To properly handle devices such as dosimeters and radiometers, it is enough to read the instructions for their use, in which in more detail describes the procedure for working with specific model. Let us briefly consider the main points of these recommendations, which general case can be reduced to the following points:

Regardless of the model you have to work with, first of all, new batteries should be installed in its power compartment;
After turning on the device, use the “Menu” button to select the required operating mode: “Dosimeter” or “Radiometer”;
Following this, in this mode, you need to switch the device to the range corresponding to the measurements being taken.

Additional Information. If even the approximate level of radioactive radiation is not known, it is recommended to set the maximum measurement limit.

Upon completion of all these preparatory operations, you should bring the device to the intended source of dangerous radiation and press the “Start” or “Start” button on the control panel. Immediately after this, the device will record the level of detected infection on the display and echo this information with an audio signal.

In the final part of the article, we note that when choosing a dosimeter or radiometer for home needs, it is not recommended to try to choose the cheapest of all models offered on the market. To solve such an important issue as the health of a person and the people around him, it is preferable to spend significant sums on purchasing a reliable and practice-tested dosimetric device.

Video

What is a dosimeter, radiometer?

Dosimeter- this is a device for measuring the dose or dose rate of ionizing radiation received by the device (and by those who use it) over a certain period of time, for example, during a period of stay in a certain area or during a work shift. The measurement of the quantities described above is called dosimetry.

Sometimes they are not quite accurately called radiometer- a device for measuring the activity of a radionuclide in a source or sample (in a volume of liquid, gas, aerosol, on contaminated surfaces) or the flux density of ionizing radiation to test suspicious objects for radioactivity and assess the radiation situation in a given place at a given moment. The measurement of the quantities described above is called radiometry. X-ray meter is a type of radiometer for measuring the power of gamma radiation.

Household appliances, as a rule, are combined, have both modes of operation with switching between “dosimeter” and “radiometer”, light and (or) sound alarms and a display for reading measurements. The weight of household ones is from 400 to several tens of grams, the size allows you to put them in your pocket. Some modern models can be worn on your wrist like a watch. Continuous operation time from one battery ranges from several days to several months.

The measurement range of household radiometers is usually from 10 microroentgen per hour to 9.999 milliroentgen per hour (0.1-99.99 microsievert per hour), measurement error up to ±30%

Detector(a sensitive element of a dosimeter or radiometer that serves to convert phenomena caused by ionizing radiation into an electrical or other signal that is easily accessible for measurement) can be an ionization chamber, a Geiger counter, a scintillator, a semiconductor diode, etc.

IONIZATION CHAMBER

An ionization chamber is a gas-filled sensor designed to measure the level of ionizing radiation.

The radiation level is measured by measuring the level of gas ionization in the working volume of the chamber, which is located between two electrodes. A potential difference is created between the electrodes. When there are ions in the gas, an ion current arises between the electrodes, which can be measured. The current, other things being equal, is proportional to the rate of ion formation and, accordingly, to the radiation dose rate.

In a broad sense, ionization chambers also include proportional counters and Geiger-Muller counters. These devices use the phenomenon of so-called gas amplification due to secondary ionization - in a strong electric field, electrons generated during the passage of an ionizing particle are accelerated to an energy sufficient to, in turn, ionize gas molecules. In a narrow sense, an ionization chamber is a gas-filled ionization detector operating outside the gas amplification mode.

The gas that fills the ionization chamber is usually an inert gas (or a mixture of both) with the addition of an easily ionizable compound (usually a hydrocarbon such as methane or acetylene). Open ionization chambers (such as ionization smoke detectors) are filled with air.

Ionization chambers are current (integrating) and pulse. In the latter case, fast moving electrons are collected at the anode of the chamber (in a time of about 1 μs), while slowly drifting heavy positive ions do not have time to reach the cathode during this time. This makes it possible to record individual pulses from each particle. A third electrode is introduced into such chambers - a grid located near the anode and shielding it from positive ions.

GEIGER-MUELLER COUNTER

Geiger counter, Geiger-Muller counter is a gas-discharge device for counting the number of ionizing particles that enter it. It is a gas-filled capacitor that breaks through when an ionizing particle passes through a volume of gas. Additional electronic circuit provides the meter with power (usually at least 300V), provides, if necessary, discharge suppression and counts the number of discharges through the counter.

Geiger counters are divided into non-self-quenching and self-quenching (not requiring an external discharge termination circuit). The sensitivity of the meter is determined by the composition of the gas, its volume and the material (and thickness) of its walls.

Radiometers produced in the USSR and Russia usually use 400-volt meters:
- “SBM-20” (slightly thicker in size than a pencil), SBM-21 (like a cigarette filter, both with a steel body, suitable for hard gamma and beta radiation);
- “SI-8B” (with a mica window in the body, suitable for measuring soft beta radiation).

The widespread use of the Geiger-Muller counter is explained by its high sensitivity, the ability to detect various types of radiation, and the comparative simplicity and low cost of installation. The counter was invented in 1908 by Geiger and improved by Müller.

A cylindrical Geiger-Muller counter consists of a metal tube or a glass tube metallized from the inside and a thin metal thread stretched along the axis of the cylinder. The thread serves as the anode, the tube as the cathode. The tube is filled with rarefied gas; in most cases, the noble gases argon and neon are used. A voltage of about 1500 V is created between the cathode and anode.

The counter operates based on impact ionization. Gamma quanta emitted by a radioactive isotope, hitting the walls of the counter, knock electrons out of it. Electrons moving through the gas and colliding with gas atoms knock electrons out of the atoms and create positive ions and free electrons. The electric field between the cathode and anode accelerates the electrons to energies at which impact ionization begins. An avalanche of ions occurs, and the current through the counter increases sharply. In this case, a voltage pulse is formed at resistance R, which is fed to the recording device. In order for the counter to register the next particle that hits it, the avalanche charge must be extinguished. This happens automatically. At the moment the current pulse appears, a large voltage drop occurs across resistance R, so the voltage between the anode and cathode decreases sharply, so much so that the discharge stops and the meter is ready for use again.

An important characteristic of the meter is its efficiency. Not all gamma photons that hit the counter will give secondary electrons and will be registered, since acts of interaction of gamma rays with matter are relatively rare, and some of the secondary electrons are absorbed in the walls of the device without reaching the gas volume.

The efficiency of the counter depends on the thickness of the counter walls, their material and the energy of gamma radiation. The most efficient are counters whose walls are made of a material with a high atomic number Z, since this increases the formation of secondary electrons. In addition, the walls of the counter must be thick enough. The thickness of the counter wall is selected from the condition that it is equal to the mean free path of secondary electrons in the wall material. If the wall thickness is large, secondary electrons will not pass into the working volume of the counter and a current pulse will not occur. Since gamma radiation interacts weakly with matter, usually the efficiency of gamma counters is also low and amounts to only 1-2%. Another disadvantage of the Geiger-Muller counter is that it does not provide the ability to identify particles and determine their energy. These disadvantages are absent in scintillation counters.

SCINTILLATORS

Scintillators are substances that have the ability to emit light when absorbing ionizing radiation (gamma rays, electrons, alpha particles, etc.). Typically, the number of photons emitted for of this type radiation is approximately proportional to the absorbed energy, which makes it possible to obtain energy spectra of radiation. Scintillation nuclear radiation detectors are the main application of scintillators. In a scintillation detector, the light emitted during scintillation is collected on a photodetector (as a rule, this is the photocathode of a photomultiplier tube - PMT; photodiodes and other photodetectors are used much less frequently), converted into a current pulse, amplified and recorded by one or another recording system.

You can buy a dosimeter from the Brom company with delivery, consulting support and service.