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: The analysis suggests that in GEO SAR imaging, the azimuth ISLR severely deteriorates, whereas degradations of theAzimuth resolution and PSLR are negligible.
Abstract: An L-band geosynchronous synthetic aperture radar (GEO SAR) will be inevitably affected by ionosphere scintillation because of its low carrier frequency. Meanwhile, compared with the low Earth orbit (LEO) SAR, a higher orbit of GEO SAR makes it have a longer integration time and a longer operation time within the susceptible regions of ionospheric scintillation. Thus, its imaging is more sensitive to ionospheric scintillation, and the corresponding degradation will have a different pattern. However, few works are focused on the quantitative analysis of the ionospheric scintillation impacts on L-band SAR. Moreover, the parameters of ionospheric irregularities utilized in the analyses are hard to be determined. In this paper, we first deduced the azimuth point-spread function with the consideration of both the amplitude and phase scintillation. Then, based on the measurable statistical parameters of ionospheric scintillation, performance specifications, including azimuth resolution, azimuth peak-to-sidelobe ratio (PSLR), and azimuth integrated sidelobe ratio (ISLR) are obtained to fully evaluate the impacts. The analysis suggests that in GEO SAR imaging, the azimuth ISLR severely deteriorates, whereas degradations of the azimuth resolution and PSLR are negligible. Finally, the simulations and a real ionospheric scintillation monitoring experiment by employing Global Positioning System satellites receivers were conducted, verifying the conclusions that the serious degraded contrast and focus quality of the images are brought by the raised azimuth ISLR.
53 citations
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53 citations
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TL;DR: In this article, an empirical approach to modeling the electron-density irregularities in the F layer that are primarily responsible for amplitude scintillation of VHF/UHF signals has been devised and tested.
Abstract: An empirical approach to modeling the electron-density irregularities in the F layer that are primarily responsible for amplitude scintillation of VHF/UHF signals has been devised and tested. An irregularity model was postulated as a function of geomagnetic latitude, local time of day, season, and sunspot number. The primary parameters of the irregularities that were postulated were their strength and transverse scale-size. The irregularities were assumed to be aligned along the geomagnetic field, and their axial ratio was taken as constant, as were the height and thickness of the irregular layer. The model is offered as a tool for VHF/UHF communication-systems planning, to the extent that the average value of scintillation in a specified circumstance is of engineering value.
53 citations
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TL;DR: This paper proposes to use artificial neural networks to simultaneously estimate the plane coordinate and DOI coordinate of incident γ photons with detected scintillation light and shows that the artificial neural network for DOI estimation is as effective as for plane estimation.
Abstract: Continuous crystal based PET detectors have features of simple design, low cost, good energy resolution and high detection efficiency. Through single-end readout of scintillation light, direct three-dimensional (3D) position estimation could be another advantage that the continuous crystal detector would have. In this paper, we propose to use artificial neural networks to simultaneously estimate the plane coordinate and DOI coordinate of incident γ photons with detected scintillation light. Using our experimental setup with an '8 + 8' simplified signal readout scheme, the training data of perpendicular irradiation on the front surface and one side surface are obtained, and the plane (x, y) networks and DOI networks are trained and evaluated. The test results show that the artificial neural network for DOI estimation is as effective as for plane estimation. The performance of both estimators is presented by resolution and bias. Without bias correction, the resolution of the plane estimator is on average better than 2 mm and that of the DOI estimator is about 2 mm over the whole area of the detector. With bias correction, the resolution at the edge area for plane estimation or at the end of the block away from the readout PMT for DOI estimation becomes worse, as we expect. The comprehensive performance of the 3D positioning by a neural network is accessed by the experimental test data of oblique irradiations. To show the combined effect of the 3D positioning over the whole area of the detector, the 2D flood images of oblique irradiation are presented with and without bias correction.
53 citations
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TL;DR: In this article, the authors investigated the scintillation properties of LuI3:Ce3+ and reported an extremely high light output of 98?000±10?000?photons/MeV.
Abstract: In this paper, we investigated the scintillation properties of LuI3:Ce3+. Radioluminescence, light output, energy resolution, and ?-scintillation decay are reported. We find an extremely high light output of 98?000±10?000?photons/MeV. LuI3:Ce3+ also gives a very high electron-hole (e-h) pair response when it is coupled with an avalanche photodiode (APD) (92?000±9000?e?h?pairs?MeV). With an APD, a best energy resolution (full width at half maximum over the peak position) of 3.3%±0.3% for 662?keV ? quanta is observed. A combination of an extremely high light output and a good energy resolution makes LuI3:Ce3+ an ideal scintillator for radiation sensor applications. Some drawbacks due to the hygroscopicity and the difficult growth of LuI3:Ce3+ crystals are also discussed.
53 citations