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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01 Jan 2004
TL;DR: In this paper, the complete system of plasma density disturbances described by the theory of the magnetic zenith effect has been studied for the first time, and a good agreement between the theory and experimental data has been obtained.
Abstract: Observations of the ionospheric electron density modified by a powerful wave of the Sura HF heating facility were carried out in Russia at middle latitudes in August 2002. Amplitude scintillations and variations of the phase of VHF signals from Russian orbiting satellites passing over the heated region along the chain of three satellite receivers have been recorded. The experimental data were converted to electron density maps using a stochastic inversion. Tomographic measurements conducted during a low magnetic activity revealed that HF powerful waves can produce significant electron density disturbances up to heights significantly exceeding altitudes of the F layer peak. Both large-scale plasma enhancements and small-scale density irregularities can be generated by the HF radiation. Wavy density structures were also observed within a sector which is much wider than the area covered by the main lobe of the heating antenna. Small-scale density irregularities are mostly field-aligned although large-scale structures can be detected within a much larger area. A distinctive peculiarity of electron density changes occurred during heating is producing a zone of low density inside the area illuminated by the antenna beam. The results indicate that satellite radio tomography and scintillation measurements are effective diagnostic techniques giving a valuable information to studies of effects induced by HF modification. The complete system of plasma density disturbances describing by the theory of “the magnetic zenith effect” has been for the first time studied in this Letter. A good agreement between the theory and experimental data has been obtained.
50 citations
TL;DR: A gamma-ray spectrometer has been flown on the Apollo 15 and 16 spacecraft to determine the lunar-surface composition and measure the cosmic gamma-rays flux as discussed by the authors, and the data were transmitted on an event-by-event basis.
49 citations
Journal Article•
TL;DR: In this paper, the interplanetary scintillation (IPS) spaced receiver technique with the radio source being a spacecraft signal was used to estimate random velocity components and identify the region where the random velocity is a significant fraction of the mean velocity.
Abstract: New remote-sensing observations are reported of the solar wind motion within about 30 earth radii. Use is made of the interplanetary scintillation (IPS) spaced receiver technique with the radio source being a spacecraft signal (rather than a natural radio source as in previous spaced receiver studies). The spacecraft used are Helios A and B and the Viking orbiters. The purposes of the study are (1) to augment the scarce estimates of solar wind bulk flow speed near the sun and in the ecliptic with measurements made using spacecraft signals, and (2) to estimate random velocity components and identify the region where the random velocity is a significant fraction of the mean velocity. In addition, the radial evolution of speed and random velocity is compared with that of the plasma density fluctuation spectrum. Also reported are the first accurately normalized IPS scintillation index measurements using a monochromatic point source.
49 citations
TL;DR: Results are much better than those of the most widely used commercial products such as NaI(Tl) and demonstrates that this 0D all-inorganic material can be employed as a scintillator for ionization radiation applications such as X-ray imaging and spectroscopy applications.
Abstract: Low dimensional scintillators have been successfully and widely applied in the radiation-detection community for home security, scientific research, and imaging. We have grown zero-dimensional Cs4PbBr6 materials with CsPbBr3 nanocrystals embedded by using a solution-growth method at low temperature. We have demonstrated the scintillation properties of these 0D nanoscintillators with high luminescence quantum efficiency for green light. In addition, we have successfully achieved pulse height spectra with this 0D perovskite material, which has been demonstrated with fast decay time (<10 ns), high energy resolution (3.0 ± 0.1%, 59.5 keV from 241Am), high light yield (64 000 photons per MeV) and long term stability under various atmospheres (moisture, radiation). These results are much better than those of the most widely used commercial products such as NaI(Tl). It also demonstrates that this 0D all-inorganic material can be employed as a scintillator for ionization radiation applications such as X-ray imaging and spectroscopy applications.
49 citations
TL;DR: In this article, the authors use computer simulations to examine several aspects of beam wander phenomena on a propagating convergent beam in the weak-fluctuation regime over a horizontal path at high altitude for which the refractive index structure parameter is on the order of C=1.39×10−16 m−2/3.
Abstract: Failure of the first-order Rytov approximation to properly predict the scintillation index of a large-aperture focused beam, or an uplink collimated (or focused) beam, has been discussed in several recent publications, which cite beam wander effects as the main reason for this failure. We use computer simulations to examine several aspects of beam wander phenomena on a propagating convergent beam in the weak-fluctuation regime over a horizontal path at high altitude for which the refractive index structure parameter is on the order of C=1.39×10−16 m−2/3. Simulation results are presented at various ranges up to 10 km for (1) the beam wander centroid displacement, (2) the kurtosis excess of the irradiance profile, (3) the irradiance profile, (4) the mean-square hot spot displacement from the boresight and from the centroid, and (5) the scintillation index at the optical axis of the beam. In addition, simulation results are compared with theoretical models.
49 citations