What Is a Scintillation Detector?
A scintillation detector is a device that uses a photodetector to visualize the scintillation light occurring when charged particles, known as scintillators, pass through it.
It is a radiation measuring instrument used to visualize radiation, which is invisible to the naked eye.
There are different types of scintillators used in scintillation detectors: inorganic, organic, solid, and liquid.
In addition to scintillation detectors, there are other instruments used to measure radiation, such as GM counter tube survey meters and ionization chambers.
Uses of Scintillation Detectors
Scintillation detectors are devices used in a wide range of fields:
1. Survey of mineral resources including petroleum
Radioactive isotope-bearing layers often exist around oil reservoirs, helping to determine the location of oil drilling.
2. Airport baggage screening
In the security field, this is an airport baggage screening machine. The principle is the same as X-ray imaging. When baggage is irradiated with radiation, the radiation is weaker in the area where the baggage is located and stronger in the area where there is no baggage.
3. PET
PET (Positron Emission Tomography) used in hospitals is a device used to detect cancer cells. Since cancer cells consume more glucose than normal cells, cancer cells can be detected by administering glucose mixed with a small amount of radiation to the patient.
4. Other
Scintillation detectors are also used in food inspection equipment, high-energy physics fields such as nuclear fusion reactors, non-destructive inspection equipment for electronic components and cultural heritage, and landmine detection equipment.
Principle of Scintillation Detectors
A scintillation detector is a device consisting of two main components: a scintillator and a photodetector. The scintillator absorbs incident X-rays and emits visible and ultraviolet light in proportion to the X-ray energy.
The photodetector, also called a photomultiplier tube, is the site where electrons are converted to light and doubled. It consists of a photocathode, which converts light generated by the scintillator into electrons, and an electron multiplier, which amplifies the converted electrons.
The photocathode is mainly composed of alkali metals and receives scintillation light through a glass window. The electrons converted by the photocathode are amplified by the electric field created in the electron multiplier, to which a high voltage is applied. These amplified electrons become an electrical signal that indicates the presence of X-rays.
Types of Scintillation Detectors
Scintillation detectors are classified according to the type of scintillator, which is selected according to the type of radiation to be detected and the purpose of use.
1. Inorganic Scintillators
Inorganic scintillation detectors are used to detect gamma rays, alpha rays, and neutrons. Inorganic crystals such as Nal (Tl), cesium iodide crystals (Csl), gadolinium oxysulfide (GOS), and gadolinium silicate crystals (GSO) are the most common types. Inorganic scintillators are characterized by high luminescence and high energy resolution, and are used in X-ray imaging equipment, food inspection equipment, luggage inspection equipment, medical PET, vehicle body inspection equipment, X-ray satellites, etc.
2. Organic Scintillators
Organic scintillators, which use organic crystals, are characterized by better response than inorganic scintillators. Typical materials include anthracene and stilbene.
3. Organic Liquid Scintillators
Organic Liquid Scintillators are characterized by their resistance to damage even when exposed to strong radiation. Organic Scintillators such as PPO (diphenyloxazole) are dissolved in organic solvents such as naphthalene, toluene, or xylene.
4. Plastic Scintillators
Plastic scintillators are made by dissolving several types of organic luminescent substances in plastic. They are suitable for detection of alpha and beta rays.
5. Gas Scintillators
High purity xenon, helium, etc., are used for gas scintillators.