Scintillation radiation detectors use the level of light energy that is produced when radiation interacts with a material to measure the amount of radiation present. This light is known as luminescence and is created when certain materials absorb a quantum of radiation. The intensity of the flash is proportional to the energy of the radiation, and this can be amplified with a photoelectron multiplier. This type of detector was first used by Ernest Rutherford in his classic experiment, in which he discovered the nucleus of the atom by scattering alpha particles of heavy atoms such as gold.
To detect these events and obtain information about radiation, some means must be used to detect light. One of the first scintillation detectors was a glass screen coated with zinc sulfide. This type of detector was used by the British New Zealand physicist Ernest Rutherford (1871-193) in the first versions of his classic experiment, in which he discovered the nucleus of the atom by dispersing alpha particles of heavy atoms such as gold. Scattered alpha particles hit the twinkling screen and the small flashes produced were observed by the experimenters in a dark room using only the human eye.
A more useful optical radiation detector for experiments is a scintillation detector. All of these devices are based on materials called scintillators, which emit bursts of light when bombarded by radiation. In principle, an observer can sit and watch a twinkler until it blinks. However, in practice, bursts of light come in small packages called photons, and the human eye has difficulty detecting them individually.
Most scintillation detectors use a photomultiplier, which converts visible light (i.e., photons) into electrical pulses that can be recorded by a computer. If the incoming radiation has a lot of energy, then the scintillator releases more light and a larger signal is recorded. Therefore, scintillation detectors can record both the energy of the radiation and the time it arrived. Materials used in scintillation detectors include certain liquids, plastics, organic crystals (such as anthracene), and inorganic crystals.
Most scintillating materials show a preference for the type of radiation they will encounter. Sodium iodide is a commonly used inorganic crystal that is especially good at finding X-rays and gamma rays. In recent years, sodium iodide has received increasing competition from barium fluoride, which is much better at determining the exact time of an event. 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.
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. 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. From the earliest days of radiation testing conducted by Roentgen and Becquerel, scientists have been looking for ways to measure and observe radiation. Experimental results using alpha particle radiation indicate that soft errors are linearly related to both irradiation time and intensity of radiation source. A particular meter known as a teletector is specifically designed to detect gamma and X-ray radiation.
These ubiquitous sources of radiation are called background radiation, and all radiation detectors have to deal with it, which they often do by shielding it. This light is called Cerenkov radiation and can be detected with photomultiplier tubes, as in the case of scintillation detectors (Figure). As its name implies, a topographic meter is a portable radiation detector that typically measures amount of radiation present and provides this information on a numerical display in units such as counts per minute or microroentgen (µR) or microrem (µrem) per hour. More energetic radiation ionizes more gas than less energetic radiation; proportional detectors can detect this difference. When talking about radiation detection, there are three types of instruments that are most often used depending on specific needs: particle detectors (also called radiation detectors), photographic plates for detecting traces left by nuclear interactions, and fog cameras for discovering subnuclear particles. Radiation safety personnel, first responders or groups such as customs border inspectors & need different sets of requirements for their screening purposes. One can learn quite a bit about a radiation source by inserting various amounts of shielding between it and counter to measure how much energy is absorbed.
