When talking about radiation detection instruments, there are three types of detectors that are most often used, depending on the specific needs of the device. There are three different main types of radiation detectors:. These are gas ionization based detectors, scintillation detectors and semiconductor detectors. Gas-filled radiation detectors work based on the ionization effect that occurs when radiation passes through air or a specific gas.
If a high-voltage potential difference is applied to a chamber containing air or a specialized gas, ionizing radiation causes the generation of positively charged ions and free electrons that were released from gas atoms during the ionization process. The electrical potential difference in the chamber will cause positive ions to accumulate at the cathode and free electrons to accumulate at the anode of the detector. “This accumulation of charged particles results in a small flowing current, which the detector can detect and display as an output signal or a “" count "”.”. The current level depends on the level of radiation incident on the detector.
Note that gas-filled radiation detectors do not detect all particles, as some of the radiation may pass through and not produce enough ionization in the chamber to be detected. In addition, these detectors generally do not report on the load, energy level, or type of incident radiation. The most common type of gas-filled radiation detector is the Geiger-Muller or GM detector. For more information on these types of radiation detectors, see our related guide About Gas-Filled Radiation Detectors.
Scintillation radiation detectors use the level of light energy that occurs when radiation interacts with a material to ultimately establish the level of radiation. Flashes of twinkling light can be brief in duration, allowing the device to detect large quantities of particles in a short period of time. Scintillating materials can be solid or liquid, and when incoming radiation hits the material, the photons are released in a device called a photomultiplier tube. The photomultiplier tube consists of a series of plates, called dynodes, each with a more positive electrical potential than the previous plate in the tube.
As the radiation releases a photon in the tube, it hits the initial dynode and releases an electron through the photoelectric effect. The released electron is attracted to the higher positive potential of the next plate in the photomultiplier, which causes the release of more electrons to pass further through the tube to the successive dynodes. This process is repeated with the amplification in the number of electrons released at each successive dynode. The result of this action is that the photomultiplier tube generates an output pulse that is proportional to the amount of light energy entering the tube, which in turn is directly proportional to the amount of radiation energy that entered the scintillation radiation detector.
Scintillation radiation detectors have the ability to provide a wealth of data on incident radiation, including energy, charge, particles, and source direction. Solid-state radiation detectors operate using an ionization principle within a semiconductor device that contains two types of semiconductor material and an n-type and a p-type. These materials consist of atoms that have charge carriers that can be considered electrons or holes, which are the absence of electrons. N-type material has more electrons than holes, whereas p-type material has more holes than electrons.
When these type semiconductor materials are united within a solid-state radiation detector, a depletion zone is created by the migration of electrons from the n region to the p region. Incident radiation hitting the semiconductor material produces free electrons and holes, and the number of electron-hole pairs is proportional to the level of radiation. As these charge carriers travel within the detector, they form a current pulse that can be used to establish the level of radiation present. Solid-state radiation detectors can be created using silicon, germanium, cadmium telluride, and cadmium-zinc telluride.
Germanium-based detectors must be cooled to cryogenic temperatures, while detectors based on cadmium telluride and cadmium and zinc telluride can operate at room temperature. The interactions of alpha, beta and gamma radiation with matter produce positively charged ions and electrons. Radiation detectors are devices that measure this ionization and produce an observable output. Early detectors used photographic plates to detect traces left by nuclear interactions.
Fog cameras, used to discover subnuclear particles, needed photographic recording and tedious measurement of fingerprints from photographs. Advances in electronics, particularly the invention of the transistor, allowed the development of electronic detectors. Scintillator-type detectors use vacuum tubes to perform the initial conversion of light into electrical pulses. The amplification and storage of this data follows advances in transistor electronics.
Miniaturization in electronics has revitalized the types of gas-filled detectors. These detectors were developed as single-element detectors and have now been converted into multi-element detectors with more than a thousand elements. Advances in materials, in particular ultra-pure materials, and manufacturing methods have been fundamental to the creation of new and better detectors. Scintillation detectors are also known as sodium iodide detectors.
They consist of a salt crystal (usually sodium iodide), also known as a scintillator, attached to a photomultiplier tube. When a particle of radiation hits the crystal, it causes excitation and release of photons, which produces a small flash of visible light. The flash reflects through a lens and makes contact with a photocathode, a specialized device that produces electrons when it comes into contact with light. The electrons are drawn through a photomultiplier and are picked up by an anode to form an electromagnetic pulse; this pulse is detected and displayed by a meter.
Scintillation detectors represent the best means of detecting gamma or X radiation and are the second most common type of detector after G-M tubes. They have the ability to distinguish between alpha, beta and gamma radiation, and can be configured to produce correspondingly different sounds through a meter. Beta detectors often use a liquid scintillation medium and can achieve reasonably high efficiencies even with lower energy emission levels. Solid-state detectors are modern semiconductor instruments that use a reverse-biased p-n junction diode.
As a particle passes through the junction, the resulting excitation of electrons causes voids to form in the valence band. Electrons are attracted to material n, while holes move towards material p. This creates a current pulse that can be measured with a meter or meter. Other standards include IEEE 309, which is specific to Geiger-Müller tubes, and ASTM D7283 for liquid scintillation counters.
Experimental results using alpha particle radiation indicate that the soft error is linearly related to the irradiation time, as well as to the intensity of the radiation source. From a functionality perspective, radiation detectors include meters, spectrometers and radiation dosimeters. A gamma-ray radiation source is mounted on one side of the pipe and a radiation detector is mounted on the opposite side. More energetic radiation ionizes more of the gas than less energetic radiation; the proportional detector can detect the.
However, one can learn quite a bit about the radiation source by inserting various amounts of shielding between the source and the counter to see how the radiation is attenuated. In the first case (gamma ray recording), natural radiation from the rock is used, while in the second case (neutron recording), a neutron source is used to excite the release of radiation from the rock. An RIID is a form of radiation detector that has the ability to display the energy spectrum of radiation, allowing identification of the specific radionuclide emitting the radiation. Radiation detectors can be characterized by the type of radiation for which they are designed to detect or by their underlying operating principles.
Current mode devices are commonly used in many applications, including radiation survey meters used for personnel protection or in monitoring devices used in intense radiation fields. A particular meter, known as a teletector, is specifically designed to detect gamma and X-ray radiation. Another term used to characterize radiation is to identify it as ionizing or non-ionizing radiation. Most neutron radiation occurs in nuclear reactors, which are protected with concrete walls or barriers that have many feet of water to effectively block radiation emissions.
Ultimately, the detector responded to solid sources that were placed next to the detectors, but the radiation dissolved in the water proved difficult to detect. A second part of this study was conducted at the EPA's National Air and Radiation Environmental Laboratory (NAREL) to determine if a commercially available radiation detector designed for water systems can show a response to radionuclide injections. . .