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.
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