Topic
Scintillation
About: Scintillation is a research topic. Over the lifetime, 14022 publications have been published within this topic receiving 187694 citations.
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TL;DR: An experimental investigation has been carried out on turbulence-induced noise in a long-path laser absorption spectrometer which measures sequentially the atmospheric transmission at two preselected wavelengths over the same path, showing that performance degradation can be significantly reduced by exploiting the coherence between fluctuations in received signal at the two wavelengths.
Abstract: An experimental investigation has been carried out on turbulence-induced noise in a long-path laser absorption spectrometer which measures sequentially the atmospheric transmission at two preselected wavelengths over the same path A simple analysis shows that performance degradation due to scintillation can be significantly reduced by exploiting the coherence between fluctuations in received signal at the two wavelengths Auto-correlation and cross-correlation properties for signals at the two wavelengths, recorded experimentally, are compared with results derived from turbulence theory, and implications for choice of spectrometer wavelengths and sampling speed are discussed
46 citations
TL;DR: In this article, a Rayleigh distribution appears to describe the worst-case scintillations in the 225-400 MHz band for the auroral and equatorial regions of the Earth.
Abstract: Periods of intense ionospheric scintillations were analyzed in order to provide information for the design and evaluation of the performance of satellite communication links. Scintillation data were available for the auroral and equatorial regions. The amplitude fluctuations are described by cumulative amplitude distributions and show good agreement with the Nakagami m-distribution. A Rayleigh distribution appears to describe the ‘worst’ case scintillations in the 225–400 MHz band. The rate of scintillations is described by level crossing techniques, power spectra, and correlation functions. The effectiveness of diversity techniques is indicated. The spectral index was measured as approximately f−0.2 indicating that intense scintillations can become almost frequency-independent in the strong scattering limit.
46 citations
TL;DR: In this article, the absorption, luminescence and scintillation characteristics of Y2SiO5:Ce (YSO-Ce) scintillator were investigated and compared to those of Lu1.95Y0.05SiO1.05Ce,Ca (LYSO:Ced,Ca) and Lu 1.95Ced.
46 citations
TL;DR: Plastic scintillation detectors show many desirable qualities when exposed to megavoltage photon and electron beams, including water equivalence, energy independence, reproducibility, dose linearity, resistance to radiation damage and near temperature independence.
Abstract: A review of the dosimetric characteristics and properties of plastic scintillation detectors for use in radiation therapy is presented. The detectors show many desirable qualities when exposed to megavoltage photon and electron beams, including water equivalence, energy independence, reproducibility, dose linearity, resistance to radiation damage and near temperature independence. These detectors do not require the usual conversion and/or correction factors used to convert the readings from common dosemeters to absorbed dose. Due to their small detecting volume, plastic scintillation detectors exhibit excellent spatial resolution. Detector performance, in certain specific cases, can be affected by radiation-induced light arising in the optical fibres that carry the scintillator signal to a photodetector. While this effect is negligible for photon beams, it may not be ignored for electron beams and needs to be accounted for.
46 citations
TL;DR: Studies for a low-earth orbiting polarimetric synthetic aperture radar called BIOMASS to provide global measurements of forest biomass and tree height find that impacts of scintillation over forest regions are negligible under all conditions except at high latitudes in the North American sector under high sunspot activity.
Abstract: The European Space Agency is conducting studies for a low-earth orbiting polarimetric synthetic aperture radar called BIOMASS to provide global measurements of forest biomass and tree height. Phase scintillation across the synthetic aperture caused by ionospheric irregularities can degrade the impulse response function (IRF) and cause squinting, and its temporal variation can cause decorrelation in repeat-pass interferometry. These effects are simulated for a range of conditions for the baseline BIOMASS system configuration using the Wideband model of scintillation, which predicts that for a dawn-dusk orbit, impacts of scintillation over forest regions are negligible under all conditions except at high latitudes in the North American sector under high sunspot activity. In this sector, single-look IRFs have mean integrated sidelobe ratios (ISLRs) and peak sidelobe ratios (PSLRs) better than 0 and -5 dB, respectively, at 90% confidence interval under median solar activity up to the northern tree line ( ~ 70° geomagnetic). Degradation in the mean 3-dB resolution of up to 10% is predicted, with mean absolute azimuth shifts of the IRF peak of up to 2 m, which increases to 5 m at high sunspot number. Similar values are found for the dawn and dusk sides, and seasonal variations are negligible for latitudes below the tree line. Repeat-pass interferometric image pairs maintain coherence up to 50 ° N under median sunspot conditions. Four-look processing improves the ISLR and PSLR by several decibels, but causes significant degradation of the 3-dB resolution due to incoherent averaging of images with different random azimuth shifts.
46 citations