The radiation detector is an instrument used to detect or identify high-energy particles, such as those produced by nuclear decay, cosmic radiation, or reactions in a particle accelerator. 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. 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. An RIID is a radiation detector with the ability to analyze the energy spectrum of radiation, in order to identify the specific radioactive material (radionuclide) emitting radiation.
A particular meter, known as a teletector, is specifically designed to detect gamma and X-ray radiation. As the name implies, the topographic meter is a portable radiation detector, which typically measures the amount of radiation present and provides this information on a numerical display in units of counts per minute, counts per second, or microroentgen (µR) or microrem (µrem) per hour. There are many types of gas-filled detectors, but the two most common are the ion chamber used to measure large amounts of radiation and the Geiger-Muller or GM detector used to measure very small amounts of radiation. From a functionality perspective, radiation detectors include meters, spectrometers and radiation dosimeters.
Another term used to characterize radiation is to identify it as ionizing or non-ionizing radiation. The primary purpose of radiation safety personnel, first responders or groups such as customs border inspectors %26, radiation screening has a different set of requirements to reflect the significantly different circumstances under which it is carried out. 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. 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.
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. Because of the risks of exposure to ionizing radiation, most radiation detectors are concerned with detecting and measuring this specific form of 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. The second important type of detectors used in radiation detection instruments are scintillation detectors.