Radiation detectors are devices used to detect and measure ionizing radiation. Radiation dosimeters are a subset of radiation detectors and are designed to measure the absorbed dose, or the amount of energy deposited by radiation in matter and especially in living tissues. Many people, when thinking about radiation detection, tend to group them all under the term “Geiger counters”, a misconception that is often encouraged by popular TV shows and movies. While one of the most common types of radiation detectors is called a “Geiger Mueller (G-M)” tube, the general phrase “Geiger counter” is not always the most appropriate.
It applies to a very specific type of detector and, in general, to a specific application of that detector. Radiation detection devices are typically classified by the type of detector element employed or by the application involved. People will refer to the instruments as an ion chamber, a probing meter, a pollution meter, or a Frisker probe. Popular culture has so profoundly subverted the correct use of “Geiger Counter” that the use of the phrase generally does not provide enough information about the device in question. 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. Personal radiation detectors or PRDs are portable devices used to detect gamma rays or neutron emissions. These types of devices include dosimeters that can be in the form of radiation plates, dosimeter plates, or other forms of electronic dosimeters.
These devices are used by law enforcement personnel or customs inspectors to detect illegal transportation of radioactive materials. Medical personnel, scientific researchers, nuclear power plant personnel, and hazardous materials equipment also use similar devices. Dosimeter types include single-use film badges and direct-read electronic pagers. A subset of PRDs are spectroscopic personal radiation detectors, or SPRDs, and can measure the energy spectrum of emitted radiation to identify its specific radionuclide. See also the next section on Radiation Isotope Identification Devices (RIIDs).
A recent market study covering these devices is available from the Department of Homeland Security. One of the important types of detectors used in radiation detection instruments are scintillation detectors. Twinkle is the act of emitting light. For radiation detection, some materials can flicker when exposed to radiation, making them useful as detectors. Each of the photon radiation interacting with the scintillator material will result in a different flash of light, which means that, in addition to being highly sensitive, scintillation detectors capture some specific spectroscopic profiles for the radioactive materials measured. 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.
The radiation detector is an instrument used to detect high-energy particles, such as those produced by nuclear decay, cosmic radiation, or reactions in a particle accelerator. 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. Radiation detectors can be characterized by the type of radiation for which they are designed to detect or by their underlying operating principles. Gas-filled radiation detectors work based on the ionization effect that occurs when radiation passes through air or a specific gas. The second important type of detectors used in radiation detection instruments are scintillation detectors. 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.
Radiation dosimetry is the most common example of this, with radiation badges used by medical personnel, workers in the nuclear industry, and many other workers exposed for work reasons around the world. One type of lift meter called a teletector features a telescopic rod that can be used to measure high radiation dose levels from approximately 4 meters away, providing an additional level of separation between the operator and the radiation source. 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. A radiation detector or particle detector is a device that measures this ionization of many types of radiation, such as beta radiation, gamma radiation and alpha radiation with matter.
