Operating principle of the dosimeter

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To measure the level of radioactive radiation, special instruments are used -dosimeters. These are precise meters that detect invisible photon rays and give readings in the form of numerical values. The higher it is, the higher the share of radiation. Purpose – to determine the radiation dose in the risk or damage zone.

Table of contents:

• types of radiation;
• classification;
• working parts of the device;
• measure of measurement;
• dosimeter action;
• appointment;
• instructions.

Types of radiation

Ionizing radiation is a type of energy in the form of electromagnetic waves of varying sizes. This includes gamma, alpha, beta rays. When atoms of ionizing rays decay, radioactivity is formed, the basis of which is radionuclides.

They are dangerous to humans and are considered an invisible killer, since it is impossible to see or detect them with the naked eye or the senses. They spread in the air, settle on surfaces, gradually destroying the body from the inside. The higher the radioactivity, the faster the cells are destroyed.

Radioactive radiation can be of five types:

• neutrons;
• alpha rays;
• beta particles;
• gamma particles;
• X-ray.

Each type has its own destructive power, penetrating ability, and other characteristics that determine the impact on health.

Classification

All devices operate on the same principle - they use an ionizing detector, the only difference is in the sensors that capture radioactive rays:

• pin diodes - household ones, have low sensitivity, operate only at a critical level of radiation;
• scintillation - professional, captures all types of radiation, with the exception of alpha particles;
• ionization dosimeters - for compact, pocket-sized devices, they capture critical values ​​of gamma and beta rays;
• Geiger counter - used in household dosimeters, they capture alpha and beta particles;
• thermoluminescent dosimeter - for household appliances, measure the accumulated radiation dosage.

The type of installed sensor does not affect the tasks and essence of the operation of the device, which converts a quantum radiation pulse and transmits it to the sensor in the form of an electrical signal. The sensor records the signal and then converts it into a radiation dose unit.

In terms of functionality and tasks performed, ionizing radiation dosimeters can:

• measure dose rate, detect changes, assess radioactivity in the area;
• measure the radiation dose, absorbed dosage;
• combine both functions.

Depending on the complexity of use, purpose, and functionality, devices can be household or professional. Household ones are needed to determine the power of radioactivity; there may be minor errors in measurements, and the analysis itself takes more time. Professionals combine two functions at once, they react quickly and produce results with maximum accuracy. This includesneutron dosimeters.

 

 

There are a lot of models and brands of dosimeters. Each manufacturer finds a way to complement the device, make it more interesting and functional. Models differ in technical characteristics, material, size, and the number of measured types of radioactive rays. The more options, the higher the price. Universal devices belong to the professional category, which also affects the cost.

Working elements of the device

Structurally, ionizing dosimeters are quite similar. What does a standard device consist of:

• ionization chamber (detector);
• registrar;
• converter;
• batteries.

The first three elements are in a common block. The device operates in one or two modes, registers the dosage and radiation equivalent for a given period of time.

The power supply device measures the difference in electrode potentials and supplies all other parts with electricity.

The converter changes the form of radiation into electrical pulses, which are then transmitted to the recorder.

The main part of a dosimeter is a detector or ionization chamber. The speed and accuracy of measurements depend on the characteristics.

Unit of measurement

Household and professional electromagnetic radiation dosimeters measure the radiation dose, as well as the power over a certain time period. For measurement, a single standard value is used - sieverts. The time unit of measurement is the hour. When measuring radiation, a numerical value is given in sievert hours, the short designation is zv/h.

New instruments often display radiation in microsieverts or microroentgens, the time unit remains the same - hour. Normal background radiation levels are about 0.2 μSv/h or 100 μR.

How does the dosimeter work?

Main elementdosimeter– detector or ionization chamber. It is filled with argon and operates under voltage. When beta particles enter the device, argon is ionized, resulting in increased conductive properties. A new electrical impulse is formed, which reduces the voltage at the electrodes to zero. The data is transferred to the recording device.

 

 

After converting beta particles into electrical impulses, the detector quickly recovers, accepts new particles, changes them and outputs values. The microprocessor, which controls the converter, is responsible for recording jumps and changes. This is where the pulses turn into numerical values.

This principle of dosimeter operation is relevant for all types, including those that recognize X-ray radiation and gamma particles. The only difference is in the way the electric charge is formed.

В dosimeters that detect gamma and x-rays, an electrical discharge is formed by displacing electrons by incoming photons. They fall on a special film, the number and frequency of pulses are recorded on the film, then the data is converted into numerical values.

 

 

Many people often confuse the two devices -dosimeter и radiometer. Their functionality is similar, however, there are significant differences that are worth paying attention to when choosing equipment.

A dosimeter is used to detect and calculate radiation dose. The radiometer determines the level of activity of radionuclides, the magnitude or density of the flux. The unit of measurement of a radiometer is roentgens or rads.

Areas of application

Dosimeters are used in any places where radiation leakage is possible - in enterprises, in closed satellite cities, in sensitive facilities, in everyday life, especially by residents of cities near which there are uranium processing plants, nuclear reactors or other industries.

Individual household appliances take up little space, but their sensitivity is lower than that of professional ones. They are not intended to increase the accuracy of measurements in the event of a slight radiation leak; they only show the excess of a critical level. Individual devices show the degree of radioactive radiation, and some models also capture power. Household appliances only detect gamma and x-ray radiation. If there is a risk of radioactive emissions in the region, it is worth purchasing such a device for personal use and taking measurements periodically.

Dosimeters are used in any conditions. The device is capable of taking samples for analysis from solid objects, gaseous substances, liquids, and aerosols.Dosimeters are used in everyday life to check:

• antiques;
• banknotes, coins;
• building materials;
• structures;
• soil;
• food;
• industrial goods;
• cargo;
• postal forwarding;
• precious things, jewelry;
• fertilizers;
• transport.

Operating instructions

Before taking measurements, you need to read the instructions that come with the kit. If it is not nearby, you can use general recommendations that are suitable for different device models.

In order for the device to show correct measurements, you need to act sequentially and step by step:

• turn on the device;
• adjust settings or use automatic mode;
• measure background radiation at a distance of 2-3 meters from the object for a minute;
• bring the device to the object with its back side (detector location);
• make repeated measurements at a distance of 1-2 cm from the object if the background radiation level when measuring at a distance is not exceeded;
• Calculate the difference between the second and first results using the subtraction method.

The normal background radiation level is 10-20 μR/h. Please note that indoor radiation will be higher than outdoors. To protect the device from radiation, put on a protective plastic cover. The device should not be brought closer than 3-6 cm to the contaminated surface.

When carrying out the test, you must take care of your equipment so as not to receive a radiation dose. If radiation leakage is suspected, protect the skin by covering it tightly with clothing, leaving no bare areas. The respiratory organs need protection. There should be no open areas on the face and body.

Using a dosimeter makes it possible to avoid the threat of radiation exposure. The invisible enemy slowly affects the body, but the consequences of such influence are very serious. The longer you are exposed to radioactive radiation, the more severe the consequences will be.