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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23 Jan 1998
TL;DR: In this paper, the authors present measurements of received intensity fluctuations at different ranges through 4 inch and 8 inch receive apertures, with its implications for use of lasercom equipment in various weather conditions.
Abstract: AstroTerra's TerraLinkTM 8-155 laser communications equipment is designed for a clear weather range of 8 km and a data rate of 230 Mb/s, and TerraLink 4-155 is designed for a 2 km range. The TerraLink equipment achieves a reduction in scintillation-induced intensity fluctuations by using large receive apertures and multiple transmit apertures. We present measurements of received intensity fluctuations at different ranges through 4 inch and 8 inch receive apertures. We also present link margin data, with its implications for use of lasercom equipment in various weather conditions. Scintillation measurements were made while a communications link was operating by placing a second receive telescope with a PIN photodiode next to one of the lasercom transceivers. By plotting the probability of intensity vs. intensity, the necessary link margin to achieve a desired burst error rate can be calculated. At the longest ranges, the TerraLink equipment requires a scintillation fade margin of about 10 dB to achieve a 10-9 bit error rate. The equipment is designed with an additional margin of 4 - 5 dB for atmospheric attenuation.
51 citations
TL;DR: In this paper, the authors compare velocities measured by earth-orbiting spacecraft and interplanetary scintillation (IPS) observations for 1973, a period when high-velocity streams were prevalent.
Abstract: Solar wind velocities measured by earth-orbiting spacecraft are compared with velocities determined from interplanetary scintillation (IPS) observations for 1973, a period when high-velocity streams were prevalent. The spacecraft and IPS velocities agree well in the mean and are highly correlated. No simple model for the distribution of enhanced turbulence within streams is sufficient to explain the velocity comparison results for the entire year. Although a simple proportionality between density fluctuation level and bulk density is consistent with IPS velocities for some periods, some streams appear to have enhanced turbulence in the high-velocity region, where the density is low.
51 citations
TL;DR: A scintillator based energetic ion loss detector has been built and installed on the National Spherical Torus Experiment (NSTX) to measure the loss of neutral beam ions.
Abstract: A scintillator based energetic ion loss detector has been built and installed on the National Spherical Torus Experiment (NSTX) to measure the loss of neutral beam ions. The detector is able to resolve the pitch angle and gyroradius of the lost energetic ions. It has a wide acceptance range in pitch angle and energy, and is able to resolve the full, one-half, and one-third energy components of the 80 keV D neutral beams up to the maximum toroidal magnetic field of NSTX. Multiple Faraday cups have been embedded behind the scintillator to allow easy absolute calibration of the diagnostic and to measure the energetic ion loss to several ranges of pitch angle with good time resolution. Several small, vacuum compatible lamps allow simple calibration of the scintillator position within the field of view of the diagnostic's video camera.
51 citations
01 Jan 2012
TL;DR: A comprehensive treatment of quench effects and quench correction in liquid scintillation counting, including the internal standard method, sample spectrum, and external standard quench-indicating parameters is provided in this paper.
Abstract: The chapter begins with a treatment of the basic theory of liquid scintillation and the interactions of alpha, beta, and gamma rays in liquid scintillator. A description of the basic design and concepts of operation of a liquid scintillation counter is provided. This is followed by a comprehensive treatment of quench effects and the methods of quench correction in liquid scintillation counting, including the internal standard method, sample spectrum, and external standard quench-indicating parameters. A detailed treatment of the preparation and use of quenched standards and quench-correction curves is provided. A discussion of direct DPM methods is also included. This is followed with a treatment on the analysis of X-ray, gamma ray, Auger electron, and positron emitters by liquid scintillation counting (LSC). A detailed discussion of the interferences encountered in liquid scintillation analysis (LSA) including background, quench, radionuclide mixtures, luminescence, and static and wall effects are described, and methods for their correction are discussed. The chapter continues with a treatment on the LSA of multiple radionuclides including dual- and triple-radionuclide analysis techniques and the analysis of more complex mixtures by spectral fitting, unfolding, and interpolation techniques. A detailed discussion of radionuclide standardization by the CIEMAT/NIST efficiency tracing and the triple-to-double coincidence ratio (TDCR) methods is provided. Neutron/gamma-ray measurement and discrimination by LSC are discussed. The use of LSC for the detection and measurement of double beta ( ββ ) decay is provided. A treatment of liquid scintillation schemes for the detection and measurement of neutrinos includes inverse beta decay and charged current interactions. Other liquid scintillation methods that are discussed include microplate scintillation and luminescence counting, PERALS and liquid scintillation alpha-spectrometry with large-area avalanche photodiodes (LAAPD), and simultaneous α / β analysis. Other methods described are the use of plastic scintillators in LSC, scintillation counting in noble liquids, radionuclide identification by LSC, and air luminescence counting. The chapter concludes with a treatment of the methods of assessment of liquid scintillation counter performance and optimization.
51 citations
TL;DR: In this paper, the seasonal pattern of the polar cap ionospheric irregularities has been monitored for several years from Thule Air Base, Greenland using 250 MHz satellite beacon scintillation measurements.
Abstract: Polar cap ionospheric irregularities have been monitored for several years from Thule Air Base, Greenland using 250 MHz satellite beacon scintillation measurements. The seasonal pattern of the polar cap irregularities shows very high intensity levels during the winter and lower levels during the summer (sunlit) months. This behavior is similar to in-situ polar cap electric field measurements which show larger fluctuations in the winter than in the summer, an effect which may be related to E layer conductivity changes. A striking contrast was noted between high scintillation levels observed during 1979/80, a year of high solar flux, and much lower levels observed during 1975, a year of low solar flux. This variation may be related to a corresponding solar cycle variation in polar cap F layer electron density. The data reveal little difference between periods of high and low Kp, and only a weak diurnal variation in any season. Direct optical and ionosonde measurements indicate that these scintillations are produced by ionospheric irregularities in the polar cap F-region. Results of spaced receiver drift measurements indicate that the small scale of irregularity drift was antisunward. Intense irregularities are associated with discrete sun aligned F layer auroras. A weak background level of scintillation persisted in the high solar flux years.
51 citations