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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: Hardware-in-the-loop tests show how the model can be used to test the scintillation robustness of any compatible GPS receiver and the model validated, by comparison with phase-screen-generated and empirical scintillation data in realistic tracking loop tests.
Abstract: A simple model is proposed for simulating equatorial transionospheric radio wave scintillation. The model can be used to test Global Positioning System phase tracking loops for scintillation robustness because it captures the scintillation properties that affect such loops. In the model, scintillation amplitude is assumed to follow a Rice distribution, and the spectrum of the rapidly-varying component of complex scintillation is assumed to follow that of a low-pass second-order Butterworth filter. These assumptions are justified, and the model validated, by comparison with phase-screen-generated and empirical scintillation data in realistic tracking loop tests. The model can be mechanized as a scintillation simulator that expects only two input parameters: the scintillation index S 4 and the decorrelation time tau0. Hardware-in-the-loop tests show how the model can be used to test the scintillation robustness of any compatible GPS receiver.
122 citations
TL;DR: Results show that as in the atmosphere, also in underwater media the plane wave is more affected by turbulence as compared to the spherical wave, and Salinity-induced turbulence strongly dominates the scintillations compared to temperature- induced turbulence.
Abstract: The scintillation indices of optical plane and spherical waves propagating in underwater turbulent media are evaluated by using the Rytov method, and the variations in the scintillation indices are investigated when the rate of dissipation of mean squared temperature, the temperature and salinity fluctuations, the propagation distance, the wavelength, the Kolmogorov microscale length, and the rate of dissipation of the turbulent kinetic energy are varied. Results show that as in the atmosphere, also in underwater media the plane wave is more affected by turbulence as compared to the spherical wave. The underwater turbulence effect becomes significant at 5-10 m for a plane wave and at 20-25 m for a spherical wave. The turbulence effect is relatively small in deep water and is large at the surface of the water. Salinity-induced turbulence strongly dominates the scintillations compared to temperature-induced turbulence.
122 citations
01 Feb 1993-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
Abstract: The gamma-ray excited, temperature dependent scintillation characteristics of CsI(Tl) are reported over the temperature range of −100 to + 50°C. The modified Bollinger-Thomas and shaped square wave methods were used to measure the rise and decay times. Emission spectra were measured using a monochromator and corrected for monochromator and photocathode spectral efficiencies. The shaped square wave method was also used to determine the scintillation yield as was a current mode method. The thermoluminescence emissions of CsI(Tl) were measured using the same current mode method. At room temperature, CsI(Tl) was found to have two primary decay components with decay time constants of τ1 = 679±10 ns (63.7%) and τ2 = 3.34±0.14 μs (36.1%), and to have emission bands at about 400 and 560 nm. The τ1 luminescent state was observed to be populated by an exponential process with a resulting rise time constant of 19.6±1.9 ns at room temperature. An ultra-fast decay component with a
122 citations
11 Jul 2004-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The physical mechanisms active in in inorganic scintillators used for medical imaging are reviewed briefly as mentioned in this paper, including relaxation of electronic excitation following initial absorption of high-energy radiation, thermalization of electrons and holes, formation of excitons, charge carrier trapping on defects and self-trapping, transfer of excitation to luminescence centers, and emission of detectable light.
Abstract: The physical mechanisms active in inorganic scintillators used for medical imaging are reviewed briefly. These include relaxation of electronic excitation following initial absorption of high-energy radiation, thermalization of electrons and holes, formation of excitons, charge carrier trapping on defects and self-trapping, transfer of excitation to luminescence centers, and emission of detectable light. Materials include intrinsic and activated insulating crystals and semiconductors involving several different luminescent centers and radiative processes. Fundamental limitations of scintillator performance and nonradiative processes arising from native defects and impurities that can limit scintillation light output are discussed. The properties of several recently reported scintillating crystals are also presented.
122 citations
TL;DR: In this article, a scintillation model was extended to the case of a propagating Gaussian-beam wave and the effect of a finite outer scale in addition to the inner scale was considered.
Abstract: A scintillation model previously developed by the authors is extended in this paper to the case of a propagating Gaussian-beam wave. As in the previous model, we account for the loss of spatial coherence as the optical wave propagates through atmospheric turbulence by eliminating effects of certain turbulent scale sizes that exist between the scale size of the spatial coherence radius of the beam and that of the scattering disc. These mid-range scale-size effects are eliminated through the formal introduction of spatial frequency filters that continually adjust spatial cut-off frequencies as the optical wave propagates. Unlike the previous model, in this paper we include the effect of a finite outer scale in addition to the inner scale. With a finite outer scale, the scintillation index can be substantially lower in strong turbulence than that predicted by a model with an infinite outer scale. This particular behaviour of scintillation in strong turbulence, mostly associated with horizontal paths...
122 citations