Scintillation

About: Scintillation is a research topic. Over the lifetime, 14022 publications have been published within this topic receiving 187694 citations.

Study of the turbulence and inner waves in the stratosphere based on the observations of stellar scintillations from space: A model of scintillation spectra

Abstract: Stellar scintillations observed from space through the atmosphere show that density inhomogeneities in the stratosphere are stretched along the Earth's surface. This is true for vertical scales above dozens of metres. The observations reveal the existence of locally isotropic small-scale structure with fluctuation sizes up to fractions of a metre. The subject of this paper is to find out how the rotation of inhomogeneities with respect to the passing ray affects scintillations. Another subject of this study is chromatic aberration in the atmosphere which distorts the scintillation spectra. Numerical modelling within the weak-fluctuation approximation showed that the characteristic value of the anisotropy parameter is equal to the square root of the Earth's radius divided by the atmospheric scale. After the anisotropy exceeds this value, the growth of scintillation variance quickly becomes saturated. Chromatic aberration suppresses the high-frequency branch of the scintillation spectrum. However, ...

Ultra precise timing with SiPM-based TOF PET scintillation detectors

Abstract: The combination of SiPMs with fast and bright scintillators, such as LaBr 3 :Ce, seems very promising for application in time-of-flight (TOF) PET We therefore conducted a series of experiments with the goal of obtaining the best possible timing resolution with SiPM-based scintillation detectors in order to establish a bench mark for future experiments with different detector designs The detectors employed in our measurements consisted of two SiPMs (Hamamatsu MPPC-S10362-33-050C), which were directly coupled to small scintillation crystals, viz LaBr 3 :Ce and LYSO An excellent coincidence resolving time (CRT) for 22Na 511 annihilation photons of 995 ps ± 06 ps FWHM could be achieved at the optimized electronics and digitizer settings with two LaBr 3 :5%Ce crystals A CRT of 1715 ps ± 08 ps FWHM was obtained with L(Y)SO crystals These results compare well to the predictions of a statistical model which was developed to describe the timing performance of SiPM based scintillation detectors

Estimation of the Cumulative Amplitude Probability Distribution Function of Ionospheric Scintillations

Abstract: The fading characteristics of ionospheric amplitude scintillations can be described by a cumulative amplitude probability distribution function (cdf). The cdf expresses the probability (percentage of time) that the signal amplitude will equal or exceed a given amplitude. Distributions of amplitude variations are made with the use of ionospheric scintillations observed on beacon signals from synchronous satellites transmitting at 136 MHz. The resulting distributions are divided into six groups corresponding to ranges of the scintillation index, the predominant measure in scintillation studies. The model distributions are then combined with the occurrence of scintillations in various index ranges to produce cumulative amplitude probability distributions. These have been done for long-term observations made at Hamilton, Massachusetts, Narssarssuaq, Greenland, and Huancayo, Peru. The results allow engineers to determine margins necessary for communication and navigation systems. Individual 15-min distributions have been compared to the theoretical distributions obtained by Nakagami [1960] in his m-distribution method of characterizing amplitude scintillation and were found to be in good agreement. The m parameter is shown to be a measure of the frequency dependence of scintillations and can be used to determine a spectral index for interpolating the amplitude distributions to other frequencies of interest.