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 ?
The beneficiary institution is deeply involved in the ACTAR development and the supervisor is managing an ERC project that aims at coupling ACTAR with gamma-ray detectors.
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.
Unlike visible-light cameras and X-ray and gamma-ray detectors, which probe at or just beneath the surface, a magnetometer senses activity several kilometers below.
The orbiting observatory carries gamma-ray detectors to identify the various elements that make up Mars' redtinted soil.
Filtering and analyzing the signals received by an array of gamma-ray detectors reveals a characteristic spectrum, or band, consisting of as many as 20 equally spaced lines.
But a novel device that combines the precision of gamma-ray detectors and the learning ability of neural networks may offer the next best alternative.
The blocks of this mock-up represent gamma-ray detectors.
Using instruments ranging from radar sensors to gamma-ray detectors, Orbiter will explore the Martian atmosphere and surface and search for underground deposits of water.
About the NSS/NIC/RTSD The 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference, and Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors workshop is in Seoul, Korea, from October 27th - November 2nd, 2013 at the COEX convention center.
He worked briefly for Canberra Industries in the early 1990s, investigating high-purity germanium gamma-ray detectors and high resolution, low noise silicon X-ray detectors.
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.
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.