Gamma-ray detectors

Gamma-ray detectors

Instruments that register the presence of gamma (γ) radiation. Such detectors convert some or all of the energy of gamma radiation into an electrical signal. Most instruments are capable of detecting individual gamma-ray photons (or quanta), each of which produces a short (0.1– 5-microsecond) current pulse at the detector output. The output pulses may be made visible on an oscilloscope, made audible through a speaker (such as the familiar Geiger counter), or be electronically processed further, depending on the application. See Gamma rays, Oscilloscope

In common with most radiation detectors, gamma-ray detectors respond not to the radiation but to its secondary effects, in this case energetic electrons. Photons have neither mass nor charge and pass through matter rather easily. In so doing, they lose energy by (1) elastic scattering of electrons (Compton effect), (2) electron-positron (β+β-) pair production, and (3) at lower energies by photoabsorption. In these processes the energy of the photon is converted to the kinetic energy of the few electrons with which it interacts. Since electrons are much less penetrating than gamma-ray photons, their energy is largely trapped within the detector, where their ionizing effect creates a response convertible to an electrical output. In a gas-ionization device, such as a Geiger counter, this occurs by the production of ion-electron pairs and in a solid-state device, such as a germanium detector, by production of electron-hole pairs. In a scintillation device, for example, a sodium iodide (NaI) detector, the response is caused by the emission of optical photons from atoms excited by the passage of energetic electrons. See Compton effect, Electron-positron pair production, Ionization chamber, Scintillation counter

In accurate instruments the magnitude of the current pulse created by a single gamma-ray photon is closely proportional to the energy within the detector volume. However, gamma radiation is so penetrating that any particular event may involve only partial absorption of the photon. For example, a single Compton scattering may be followed by the escape of the scattered photon (now reduced in energy) from the detector, leaving behind only the energy of the scattered electron.

Gamma-ray detectors range from hand-held devices capable of giving some indication of the intensity of a radiation field to devices that accurately measure the energy and event time of individual photons reaching detectors assembled into a single complex instrument. These diverse detectors are widely used in industry, medicine, and research.

References in periodicals archive ?
RMD president Kanai Shah added, "From the development of imaging devices designed to 'see' through the walls of nuclear power plant concrete structures to gamma-ray detectors that enable the next generation of dark matter studies, the Phase II research projects we are embarking on through these SBIR/STTR programmes embody some of the world's most pressing high-energy physics and energy production research needs.
president of Dynasil's RMD subsidiary, said, 'From the development of imaging devices designed to 'see' through the walls of nuclear power plant concrete structures to gamma-ray detectors that enable the next generation of dark matter studies, the Phase II research projects we are embarking on through these SBIR/STTR Programs embody some of the world's most pressing high energy physics and energy production research needs.
Prior to this discovery, noble metals, such as gold or platinum, were exclusively used as contacts to CZT for the fabrication of commercial x-ray and gamma-ray detectors.
We can tailor the properties of these ternary compounds by tailoring the bandgaps and hence bulging these compounds as significant materials for future progressions within the field of device fabrication like solar cells, X-Ray and gamma-ray detectors, electro-Optical modulators, LEDs, nuclear radiation detectors etc [1-3].
14 June 2012 - Princeton Security Technologies Inc (OTCBB:PSGY), the US supplier of X-ray and gamma-ray detectors, portable radioisotope identifiers and portable chemical analysers, said it had signed a definitive agreement to be acquired by Thermo Fisher Scientific Inc (NYSE:TMO).
Efforts to confirm those observations helped spur the development of improved gamma-ray detectors, a legacy culminating in the Large Area Telescope (LAT) aboard Fermi.
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Participant David Thompson (NASA/Goddard) emphasizes that the mission required the know-how of both branches of science: "The particle physicists bring tremendous expertise in building sophisticated gamma-ray detectors, while the astrophysicists offer strong experience in operating telescopes in a space environment to address well-defined questions about the universe.
It has 16 tower-shaped gamma-ray detectors, each consisting of thin tungsten foils interleaved with silicon strips, giving a total collecting area of about 35 square meters.
Determined to check the Russians weren't secretly exploding nuclear weapons on the far side of the Moon, the Americans ordered a brilliant Los Alamos engineer, Ray Klebasadel, to design a network of orbiting gamma-ray detectors to alert them to clandestine Soviet explosions in space.
In their place, gamma-ray detectors, developed at Sandia National Laboratories in Livermore, Calif.
Though they don't check for foreign objects, gamma-ray detectors made by Industrial Dynamics, Torrance, Calif.