To test whether food is contaminated by nuclear weapons, you need to use professional equipment - a nuclear pollution detector, or send it to a professional testing center for testing or regular monitoring.

Principles and methods of nuclear radiation monitoring

Materials or devices that can indicate, record and measure nuclear radiation. The interaction of matter in radiation and nuclear radiation detectors produces certain information (such as electrical, light pulses or changes in material structure), which is amplified and recorded and analyzed to determine the number, position, energy, momentum, and flight of the particles. Physical quantities such as time, speed, and mass. Nuclear radiation detectors are indispensable tools and means in nuclear physics, particle physics research and radiation applications. According to the recording method, nuclear radiation detectors are generally divided into two categories: counters and track chambers.

Counter? Record and analyze certain information generated by radiation in the form of electrical pulses. Counter types include gas ionization detectors, multifilament chambers and drift chambers, semiconductor detectors, scintillation counters and Cherenkov counters.

Professional nuclear radiation detection equipment

Gas ionization detector?

Measure nuclear radiation by collecting the ionization charges generated by rays in the gas. The main types are ionization chambers, proportional counters and Geiger counters. Their structures are similar. They are generally cylindrical containers with two electrodes, filled with some kind of gas, and a voltage is applied between the electrodes. The difference is that the operating voltage range is different. The ionization chamber operates at a low voltage and directly collects the ion pairs originally generated by the rays in the gas. Its output pulse amplitude is small and the rise time is fast, so it can be used for radiation dose measurement and energy spectrum measurement. The working voltage of the proportional counter is high, which can cause the original ions moving at high speed in the electric field to generate more ion pairs, and collect much more ion pairs than the original ion pairs on the electrode (i.e., gas amplification), thus obtaining higher output pulse. The pulse amplitude is proportional to the energy lost by the incident particle and is suitable for energy spectrum measurements. The Geiger counter is also called the Geiger-Miller counter or the G-M counter. Its working voltage is higher and multiple ionization processes occur. Therefore, the amplitude of the output pulse is very high and is no longer proportional to the number of ion pairs in the original ionization. It can be used without Amplification is recorded directly. It can only measure the number of particles but not the energy, and it takes a long time to complete a pulse count.

Semiconductor detector?

The carriers (electrons and holes) generated by radiation in the semiconductor are collected under a reverse bias electric field and generated by the electrical pulse signal to measure nuclear radiation. Silicon and germanium are commonly used as semiconductor materials. There are three main types: ① surface barrier type where a layer of gold film is sprayed on the n-type single crystal; ② a layer of gold film is diffused on the p-type silicon wafer with higher resistivity that can provide electrons. Diffusion junction type of impurities; ③ Lithium drift type where a thin layer of metallic lithium is sprayed on the surface of p-type germanium (or silicon) and drifted. High-purity germanium detectors have high energy resolution, high gamma radiation detection efficiency, can be stored at room temperature, and are widely used. Materials such as gallium arsenide, cadmium telluride, and mercury iodide are also used.

Scintillation counter?

By hitting the scintillator with charged particles, the atoms (molecules) are ionized and excited, and emit light during the de-excitation process. After passing through the optoelectronic device (such as photomultiplier tube) ) to measure nuclear radiation by converting optical signals into measurable electrical signals. The scintillation counter has short resolution time and high efficiency, and can also measure the energy of particles based on the size of the electrical signal. Scintillator can be divided into three major categories: ① Inorganic scintillator, commonly used thallium (Tl)-activated sodium iodide NaI (Tl) and cesium iodide CsI (Tl) crystals, which are sensitive to electrons and gamma radiation and have high luminous efficiency , has better energy resolution, but the light decay time is longer; the bismuth germanate crystal has high density and high luminous efficiency, so it is very effective in detecting high-energy electrons and gamma radiation. Others, such as zinc sulfide ZnS (Ag) activated with silver (Ag), are mainly used to detect alpha particles; glass scintillator can measure alpha particles, low-energy X radiation, and can measure neutrons after adding a carrier; barium fluoride (BaF2) has a high density , has a fluorescent component and is suitable for both energy measurement and time measurement. ② Organic scintillator, including plastic, liquid and crystal (such as anthracene, stilbene, etc.), the first two are commonly used. Because of their short light decay time (2 to 3 nanoseconds, fast plastic scintillator can be less than 1 nanosecond), they are often used in time measurement. Their detection efficiency for charged particles is nearly 100 percent. ③ Gas scintillators, including inert gases such as xenon and helium, have low luminous efficiency but short light decay time (<10 nanoseconds).

Cherenkov counter?

When the speed of high-speed charged particles in a transparent medium exceeds the speed of light in the medium, Cherenkov radiation will be generated. Its radiation angle is related to the particle velocity, thus providing a detector for measuring the velocity of charged particles. This type of detector is often used in conjunction with a photomultiplier tube; it can be divided into two types: threshold type (only records particles greater than a certain speed) and differential type (only selects particles with a certain speed). ? In addition to the commonly used counters mentioned above, there are also gas proportional scintillation chambers and self-quenching streamer counters, which are gas detectors that have appeared recently, with large output pulse amplitude and good time characteristics. Electromagnetic calorimeters (or shower counters) and hadron calorimeters can measure the energy of high-energy electrons, gamma radiation or hadrons (see elementary particles) respectively. Transition radiation counters provide a way to identify extremely high-energy charged particles.

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