Devices whose task is to measure the level of radiation, in our time can be attributed almost to the category of consumer electronics. How does this technique work and why has it become so popular?
How it works?
The most famous and popular device for measuring radioactivity is a geiger counter. He owes his name and birth to the German physicist Hans Geiger, who constructed this device in 1908 together with another famous scientist, Ernst Rutherford. 20 years later, Geiger returned to his invention and finalized it together with physicist W. Muller. Despite the fact that this device is more than a hundred years old, it has been successfully used today. Most household dosimeters have a similar operating principle.
How does a geiger counter work? Its main element is a sealed glass or metal container filled with a mixture of inert gases - neon and argon. Two electrodes are placed here in the container. As you know, radiation propagates in the form of wave particles. When at least one of these particles gets inside the counter, the gas mixture is ionized: the atoms of the gas receive a charge of energy at which they can glow. This process is fixed by the counter. To record the exact amount of radioactive particles, the ionization process is artificially quenched. This happens within a split second. When radioactive particles are detected, the geiger counter emits a characteristic clicking sound.
The radiation level is measured in other ways. Along with geiger counters, scintillation crystals are often used. The effect of these devices is based on the fact that some substances (for example, sodium iodide or zinc sulphide) glow when radioactive radiation is detected. The number of flashes depends on the dose of radiation and is fixed by a special device - a photomultiplier.
Another option is a chemical method for detecting radioactivity. It uses chemical reactions that occur in some substances under the influence of radioactive radiation. For example, chloroform in this case decomposes and forms hydrochloric acid, which enters into a color reaction with a dye added to chloroform.
Where is radiation measured in everyday life?
Why is this technique needed for people who have nothing to do with a peaceful atom? Most often, a radioactivity dosimeter is used to measure the level of radiation in food or building materials. Also, radioactivity can check the land on which the house is built or planned to be built. It so happened that for a long time mankind neglected radiation, arranging nuclear burial grounds in the most unexpected places - on the seabed or in some abandoned mine. The Chernobyl disaster forced many to look at radiation with different eyes. Yes, and the recent accident at Fukushima made the geiger counter and other dosimeters popular.
Typically, household dosimeters are small. They are equipped with displays on which you can see the level of radiation. Dosimeters can be threshold and non-threshold. Devices of the first type are triggered when exceeding the permissible radiation level, which is pre-set by the manufacturer. A sound signal is emitted. Such dosimeters are cheaper and easier to use. Devices of the second type show a specific radiation level, the threshold level on them can be set manually. Such a device is more convenient for professionals when a person knows exactly what level of radiation in this case is dangerous.
As you can see, it is quite possible to detect radiation in a domestic environment. But the presence of a dosimeter in the house does not make you a professional. Therefore, when detecting infected objects or places, you still have to use the help of specialists.