scintillation


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scintillation

(sin-tă-lay -shŏn) (twinkling) Rapid irregular variations in the brightness of light received from celestial objects, noticeably stars, produced as the light passes through the Earth's atmosphere: irregularities in the atmosphere's refractive index occur in small mobile regions and can cause the direction of the light to change very slightly during its passage. In a telescope a star image will consequently wander rapidly about its mean position, producing an overall blurred enlarged image. With extended light sources, such as the planets, scintillation produces a hazy outline in a telescopic image. For stars near the horizon, where refraction effects including dispersion are much greater, changes in color can also be observed. See also scattering; speckle interferometry.

Scintillation

 

a brief (~10–4–10–9 sec) flash of light that occurs in a scintillator under the action of ionizing radiation. Scintillations were first visually observed by W. Crookes in 1903, when he irradiated a zinc sulfide screen with alpha particles.

The energy of the charged particles that is absorbed by the scintillator causes the atoms or molecules of the scintillator to undergo a transition to an excited state. The subsequent transition from the excited state back to the normal state is accompanied by the emission of light—that is, by a scintillation. The scintillation mechanism, the spectrum of the scintillation radiation, and the emission time depend on the nature of the luminescent substance. The brightness of the scintillation depends on the nature of the charged particles and on the energy given up by the particle during its passage through the substance. For example, scintillations produced by alpha particles and protons are considerably brighter than scintillations produced by beta particles. Each scintillation is produced by a single particle. This fact is made use of in scintillation counters for the detection of elementary particles.

scintillation

[‚sint·əl′ā·shən]
(electromagnetism)
A rapid apparent displacement of a target indication from its mean position on a radar display; one cause is shifting of the effective reflection point on the target. Also known as target glint; target scintillation; wander.
Random fluctuation, in radio propagation, of the received field about its mean value, the deviations usually being relatively small.
(lapidary)
The flashing, twinkling, or sparkling of light, or the alternating display of reflections, from the polished facets of a gemstone.
(nucleonics)
A flash of light produced in a phosphor by an ionizing particle or photon.
(optics)
Rapid changes of brightness of stars or other distant, celestial objects caused by variations in the density of the air through which the light passes.
Rapid changes in the values of irradiance over the cross section of a laser beam.
References in periodicals archive ?
Gbur, "Scintillation reduction in multi-Gaussian Schell-model beams propagating in atmospheric turbulence," Proc.
Adequate knowledge of the temporal properties and fading time scales of amplitude scintillation can be very useful in the development of appropriated mitigation tools of current positioning/navigation applications based on GNSS signals.
In order to study how to keep enough X-ray energy deposition in CsI(Tl), Nal(Tl), and CdW[O.sub.4] scintillation crystals and transform more X-ray photons into visible light photons to obtain high spatial resolution of CT images in industrial X-CT system, it is a reasonable scheme to simulate the photonic properties of CsI(Tl), Nal(Tl), and CdW[O.sub.4] scintillation crystals using Monte Carlo (MC) method [1726].
Beran and Whitman [20] calculated the scintillation index of a plane wave using the two-scale theory and assuming a Kolmogorov structure function with an altitude-dependent structure constant.
The solar wind speeds are derived from a cross-correlation analysis of multi-station IPS data, and the scintillation levels are calculated from the power spectra of IPS data at a given station.
Taking into account energy conservation, the scintillation and storage luminescence should be complementarily related to each other.
For disruptive effects on DSNs, solar scintillation is a major problem which should be considered in a DSN scenario.
These parameters, and their corresponding constant values along the FSO can be identified using the moments of small and large scale irradiance fluctuations and are directly tied to the atmospheric parameters (the ratio of Fresnel zone, Rytov variance, [[sigma].sup.2][R.sub.ytov], proportional to the scintillation index, and function of wavenumber, k = 2[pi]/[lambda], the refractive index structure constant, and the propagation distance) as shown in (9a), (9b) and (10) from [13], Parameters [[OMEGA].sub.1] and [[OMEGA].sub.2] depend on and directly are tied to the atmospheric conditions.
Beddar and Beaulieu provide a comprehensive introduction to plastic scintillation dosimetry from basic radiation dosimetry concepts to plastic scintillating fiber optics.
A sampling of topics includes small instruments like gas-filled, scintillation, and semiconductor detectors; the gamma camera; single-photon emission computed tomography (SPECT); and positron emission tomography (PET).
Samples are dried in 20-mL scintillation or other common vials and there is no need for a vacuum pump or a large supply of blow-down gas.
The legal action concerns Zecotek's US patent number 7,132,060, which covers the substances and chemical formulations used to grow lutetium fine silicate (LFS) scintillation crystals which are characterised by their combined high light yield and ultra-fast decay times and are typically used in medical scanning devices.