A Geiger counter, named after Hans Geiger, a German scientist in the early 20th century who worked on radiation detection, is an instrument that can detect radiation. Personal Radiation Detectors (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 (SPRDs) and can measure the energy spectrum of emitted radiation to identify its specific radionuclide. See also the section below on Radiation Isotope Identification Devices (RIIDs).A recent market study covering these devices is available from the Department of Homeland Security. This light is called Cerenkov radiation and can be detected with photomultiplier tubes, as in the case of scintillation detectors (Figure).
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. A particular meter, known as a teletector, is specifically designed to detect gamma and x-ray radiation. Radiation detectors can be characterized by the type of radiation they are designed to detect or by their underlying operating principles. 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. Because film detectors are good at determining radiation levels, they are commonly used for radiation safety. Gas-filled radiation detectors work based on the ionization effect that occurs when radiation passes through air or a specific gas.
The second major type of detectors used in radiation detection instruments are scintillation detectors. 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. Because of the risks of exposure to ionizing radiation, most radiation detectors are concerned with detecting and measuring this specific form of radiation. Another term used to characterize radiation is to identify it as ionizing or non-ionizing 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. 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.
