Showing papers on "Scintillation published in 1979"
TL;DR: In this article, the weak scatter scintillation theory is reformulated to show explicitly the ramifications of an arbitrarily large ionospheric outer scale, which is applied to representative data sets from the Wideband satellite.
Abstract: In this paper the weak scatter scintillation theory is reformulated to show explicitly the ramifications of an arbitrarily large ionospheric outer scale. The measured temporal phase spectrum, for example, is effectively truncated at a fixed frequency corresponding to the detrend time or the length of the data interval over which it is measured (whichever is smaller). As a consequence, the rms phase exhibits a complicated dependence on the relative irregularity drift velocity and the propagation geometry. This effect has not been included in previous analyses. By comparison, intensity scintillation data are intrinsically high-pass filtered by the diffraction process. By taking advantage of this fact a simple closed form expression for the S4 intensity scintillation index has been derived. The theory is applied to representative data sets from the Wideband satellite. The interpretation of the ionospheric parameters deduced from the analysis is also discussed.
443 citations
TL;DR: The development of organic scintillators is reviewed with emphasis on work that has been reported since 1964 as mentioned in this paper, and the scintillation process is discussed, including response energy dependence, energy resolution, timing characteristics, pulse shape discrimination and anisotropy.
317 citations
TL;DR: In this paper, a review of the timing properties of scintillators and photomultipliers as well as theoretical and experimental studies of time resolution is presented, where the influence of the light collection process and the self-absorption process on the light pulse shape are discussed.
131 citations
TL;DR: The mechanism of photon emission in the rare-gas proportional scintillation counter was ascribed to the radiative de-excitation of excited molecules, R 2 ∗ →R+R+hv, by determining emission spectra experimentally as mentioned in this paper.
128 citations
TL;DR: In the aggregate, acoustic gravity waves in the F-region constitute a spectrum of geophysical noise extending from the frequencies involved in diurnal variations up to the Brunt-Vaisala buoyancy frequency.
83 citations
TL;DR: In this paper, radio-wave phase scintillation was observed using the Viking spacecraft having an earth-spacecraft link very similar to that which will be used in very low-frequency (VLF) gravitational-wave searches.
Abstract: Observations of radio-wave phase scintillation are reported which used the Viking spacecraft having an earth-spacecraft link very similar to that which will be used in very low-frequency (VLF) gravitational-wave searches. The phase power-spectrum level varies by seven orders of magnitude as the sun-earth-spacecraft (elongation) angle changes from 1 to 175 deg. It is noteworthy that a broad minimum in the S-band (2.3 GHz) phase fluctuation occurs in the antisolar direction; the corresponding fractional frequency stability (square root Allan variance) is about 3 x 10 to the -14th for 1000-s integration times. A simultaneous two-frequency two-station observation indicates that the contribution to the phase fluctuation from the ionosphere is significant but dominated by the contribution from the interplanetary medium. Nondispersive tropospheric scintillation was not detected (upper limit to fractional frequency stability about 5 x 10 to the -14th). Evidently, even observations in the antisolar direction will require higher radio frequencies, phase scintillation calibration, and correlation techniques in the data processing, for detection of gravitational bursts at the anticipated strain amplitude levels of no more than 10 to the -15th.
82 citations
TL;DR: The characteristics of scintillation detectors for neutron physics such as efficiency, timing resolution, size, pulse height resolution, backgrounds, and characteristics of 6Li glass detectors are reviewed in this paper.
69 citations
TL;DR: In this paper, an improved gas scintillation proportional counter with a measured overall energy resolution of 9.3% at 5.9 keV has been built, which is sufficiently well defined to allow the use of pulse-shape discrimination to reject 86% of the non-X-ray events in a space environment.
54 citations
TL;DR: In this paper, the characteristics of a liquid xenon proportional scintillation counter have been studied by using conversion electrons from 207 Bi and the best resolution was about 18% fwhm for 1 MeV electrons, which was almost the same as that of the charge.
54 citations
TL;DR: The antenna and beam geometry of lidar systems employing heterodyne reception of incoherent backscatter signals are discussed, with particular emphasis on systems where the target extends uniformly across the transmitted beam using topographic targets or atmosphericBackscatter.
Abstract: The antenna and beam geometry of lidar systems employing heterodyne reception of incoherent backscatter signals are discussed. Particular emphasis is placed on systems where the target extends uniformly across the transmitted beam using topographic targets or atmospheric backscatter. The geometry is assumed to be circularly symmetrical, but otherwise arbitrary obscurations are permitted. The effects of atmospheric scintillation are neglected. Parameters are defined which characterize the system efficiency, and the conditions under which these parameters may be maximized are considered.
46 citations
Patent•
22 Jun 1979TL;DR: In this paper, a method and apparatus for correcting for the spatial distortions of scintillation cameras or similar image forming apparatus is presented, which accurately and precisely determines distortion correction factors in an off-line test measurement and analysis phase prior to actual on-line diagnostic use.
Abstract: A method and apparatus for correcting for the spatial distortions of scintillation cameras or similar image forming apparatus. The spatial distortion correction method accurately and precisely determines distortion correction factors in an off-line test measurement and analysis phase prior to actual on-line diagnostic use. The distortion correction factors are initially determined from image event data that is obtained during the test measurement phase by orthogonal line pattern images. Data from a uniform field flood image is also utilized during the test measurement phase to refine and modify the distortion correction factors utilizing the gradient of a function of the field flood image data. Scintillation camera image repositioning apparatus is provided and includes a memory having the correction factors stored therein in a predetermined array. During the on-line use of the scintillation camera and associated image display system, the image repositioning apparatus transforms the data from the scintillation camera in accordance with the stored distortion correction factors. In a preferred arrangement, the image event data is repositioned or corrected event by event.
TL;DR: In this article, an accurate energy calibration of organic scintillation counters by means of γ-rays is described, where the position of the Compton edge has been precisely determined comparing measured with calculated spectra.
Abstract: An accurate energy calibration of organic scintillation counters by means of γ-rays is described. The position of the Compton edge has been precisely determined comparing measured with calculated spectra. The calculation includes wall and light pipe effects and the influence of channel dependent pulse height resolution. Relations are given for the position of the maximum and the half maximum of a Compton spectrum as a function of the incident photon energy and the resolution of the detector. Results are given with uncertainties smaller than 1 %.
TL;DR: In this paper, the decay time constants for solid, liquid and also gaseous argon are given for the two components of the scintillation decay, and changes in the relative intensity values of two components are discussed in terms of track effects.
Patent•
03 Apr 1979
TL;DR: A dual scintillation radiation detector has been proposed in this paper to detect and determine the quantity of the two different radiations such as beta and gamma present within an unknown sample.
Abstract: A dual scintillation radiation detector having two different scintillation detector materials arranged and shaped in order to detect and determine the quantity of the two different radiations such as beta and gamma present within an unknown sample. The detector can be used in apparatus for laboratory use, manual portable probe applications, or in elongated probes for simultaneously reading radiation present as the probe is lowered into an earth bore. The scintillation radiation detector material for the high energy radiation is positioned on the opposite side of the first detector material from the radiation source so that the high energy radiation must penetrate through the first material before entering the second. This provision allows discrimination and filtering of the low energy radiation from the second detector material. The first detector material is provided in the shape of a thin, flat plate or in the shape of a hollow cup with the second material mounted on one side of the plate or within the cup. Suitable photomultiplier sensing tubes are connected to a surface of the scintillation material to convert the light energy pulses caused by the radiation into electrical output pulses which are processed and digitally displayed. Suitable radiation shielding is provided in conjunction with the scintillation detector materials to filter and discriminate against unwanted low energy radiation. The detector is suitable for use in the beta-gamma method of analysis for determining uranium oxide ore grade within an unknown sample.
TL;DR: In this article, first-order statistics and temporal correlations of intensity fluctuations in stellar images and in the pupil plane are reported, and it is shown that measurements in the image plane are strongly dependent on the zenith angle.
Abstract: We report measurements of first-order statistics and temporal correlations of intensity fluctuations in stellar images and in the pupil plane. Measurements in the pupil plane are strongly dependent on zenith angle, whereas simultaneous measurements in the image plane show no such dependence.
TL;DR: In this article, a new technique is presented to improve the count rate capability of a scintillation spectrometer or a position sensitive detector with minimum loss of resolution, which is based on the combination of pulse shortening and selective integration in which the integration period is not fixed but shortened by the arrival of the following pulse.
TL;DR: In this paper, the long-wave cutoff in the spectrum of amplitude fluctuations was shown to be capable of explaining strong SHF scintillation in the troposphere, which is also applicable to strong VHF and EHF Scintillation.
Abstract: Ionization structure perpendicular to the line of sight can cause total internal reflection at glancing incidence, leading to refractive scattering that can dominate diffractive scattering The long-wave cutoff in the spectrum of amplitude fluctuations then occurs, not at the Fresnel scale but at a larger scale that increases as the percentage fluctuation of ionization density increases The additional amplitude fluctuation arising from the band of scales extending from the usual diffractive cutoff scale up to the refractive cutoff scale is capable of explaining strong SHF scintillation It also lowers the estimates of the fluctuation of ionization density needed to explain strong VHF scintillation The concept of refractive scattering is also likely to be applicable to SHF-EHF scintillation phenomena in the troposphere
TL;DR: In this article, a liquid xenon drift chamber with an electron drift space of 13 mm in length has been constructed and the spatial resolution of the drift chamber was investigated by using alpha particles.
Journal Article•
TL;DR: In this paper, the authors presented new data on the scintillation properties of bismuth germanate as a function of temperature from -196/sup 0/C to +30/sup 1/C. The implications of this work to the design of imaging devices for high-energy radiation in health physics and nuclear medicine are discussed.
Abstract: Bismuth germanate is a scintillation material with very high z, and high density (7.13 g/cm/sup 3/). Is is a rugged, nonhygroscopic, crystalline material with room-temperature scintillation properties described by previous investigator as having a light yield approx. 8% of that of NaI(Tl), emission peak at approx. 480 nm, decay constant of 0.3 ..mu..sec, and energy resolution approx. = 15% (FWHM) for Cs-137 gamma radiations. These properties make it an excellent candidate for applications involving the detection of high-energy gamma photons and positron annihilation radiation, particularly when good spatial resolution is desired. At room temperature, however, the application of this material is somewhat limited by low light output and poor energy resolution. This paper presents new data on the scintillation properties of bismuth germanate as a function of temperature from -196/sup 0/C to +30/sup 0/C. Low-temperature use of the material is shown to greatly improve its light yield and energy resolution. The implications of this work to the design of imaging devices for high-energy radiation in health physics and nuclear medicine are discussed.
Patent•
19 Jun 1979
TL;DR: In this paper, a two-stage system for enhancing imaging uniformity of a nuclear scintillation camera is proposed, where a first stage locates and stores a representation of the respective peaks of the detected energy pulse height distribution for each of a plurality of regions in a camera's field of view.
Abstract: Scintillation Camera Uniformity Correction Abstract A two-stage system (u) for enhancing imaging uniformity of a nuclear scintillation camera. The system compensates for imprecision in the camera's indication of both radiation event regional image count density and event energy level. A first stage (30, 32) locates and stores a representation of the respective peaks of the detected energy pulse height distribution for each of a plurality of regions in a camera's field of view. This repre-sentation is used to successively realign for each count the pulse height energy window, to align the window over the respective energy peak for each count as a function of the count's location in the field. A second flood correction stage (40, 42, 44) produces and stores a profile of regional variation in image count density indicated by the camera in response to a uniform radiation flood field. The stored information is used for calculating regional count density correction factors for different regions of the camera field. The correction factors are applied for controlling the ratio of radiation counts corresponding to each region which are actually imaged.
TL;DR: The influence of geometrical and optical parameters on the light collection within scintillator assemblies has been investigated and Monte-Carlo calculations predicted a strong dependence on the design of the light guide and the effective reflectivity of its covering.
Abstract: The influence of geometrical and optical parameters on the light collection within scintillator assemblies has been investigated. Monte-Carlo calculations predicted a strong dependence on the design of the light guide and the effective reflectivity of its covering. Excellent agreement of experimental and theoretical data is shown for a small " standard"-scintillator (5.08 cm x 5.08 cm in diameter) as well as for largearea systems (5.08 cm x 25.4 cm in diameter). In both cases partially coated light guides should be used to restrict the local dependence of the light transmission to less than 2 % or 4 % resp. over the total volume. The averaged absolute transmission is calculated to be approximately 80 % or 45 % resp. for these optimized setups.
Patent•
12 Jun 1979
TL;DR: In this article, a method and apparatus for automatically stabilizing drift in radiation measurements which employ a detector whose pulse amplitude corresponds to the energy absorbed by the detector, involves the use of a peak produced in the pulse amplitude spectrum by individual electrons.
Abstract: A method and apparatus for automatically stabilizing drift in radiation measurements which employ a detector whose pulse amplitude corresponds to the energy absorbed by the detector, involves the use of a peak produced in the pulse amplitude spectrum by individual electrons. The peak is at the low energy end of the spectrum and is drift stable. It can be produced by for example a direct or indirect light source such as a light emitting diode, by the phosphorescence of e.g. a sodium iodide crystal used as a scintillation crystal in nuclear radiation measurement, or by spontaneous surface emission within the detector, which is suitably a photomultiplier. The apparatus includes a determination device to determine the position of the drift stable peak and a control device to control the detector in response to the output of the determination device.
Patent•
30 Jul 1979TL;DR: In this article, a high resolution detector having a scintillation crystal for receiving incident X-rays at a front face and interacting with the radiation to generate corresponding visible light radiation was presented.
Abstract: A high resolution detector having a scintillation crystal for receiving incident X-rays at a front face and interacting with the radiation to generate corresponding visible light radiation. Silicon photodiode arrays are positioned on top and bottom lateral faces of the scintillation crystal to receive the visible light that is radiated laterally with respect to the direction of propagation of the incident X-rays. Photodiode elements in each photodiode array extend from the forward face of the scintillation crystal in the direction of propagation of the incident X-rays. The length of the photodiode elements determines the radiation stopping power of the high resolution detector and the height of the front face of the scintillation crystal determines the resolution of the detector. The height of the forward face of the crystal may be made small with respect to the length of the photodiode elements to provide a detector having high resolution and high radiation stopping power.
Patent•
20 Nov 1979TL;DR: In this paper, a method and apparatus for the dynamic modification of the spatial distortion correction capabilities of a scintillation camera having spatial distortion corrections was proposed, which can automatically and dynamically correct for spatial distortion effects for image events of different energy levels.
Abstract: A method and apparatus for the dynamic modification of the spatial distortion correction capabilities of a scintillation camera having spatial distortion correction apparatus. The spatial distortion correction apparatus includes a memory having stored therein spatial distortion correction factors in a predetermined addressable format. During the on-line use of the scintillation camera, the spatial distortion correction apparatus transforms the image event coordinate position data from the scintillation camera in accordance with the stored distortion correction factors to provide corrected image event coordinate repositioning data. The spatial distortion correction modification apparatus and method provides modification of the corrected image event coordinate data in accordance with the respective energy levels of the image events to provide accurate spatial distortion correction characteristics for the actual energy levels of the image events. The scintillation camera is thus automatically and dynamically capable of correcting for spatial distortion effects for image events of different energy levels. Different energy levels of image events occur when the scintillation camera is utilized with energy sources having multiple energy levels or a different energy level than the energy level at which the stored spatial distortion correction factors were calculated. The spatial distortion correction modification apparatus provides operation without the alteration of the scintillation camera apparatus and without any change in the stored correction factors. In a preferred embodiment, a coordinate correction factor of the spatial distortion correction apparatus is modified in accordance with the energy level of each image event, the coordinate correction factor of the spatial distortion correction apparatus being combined with the image event coordinate position data to provide corrected image event coordinate data.
TL;DR: In this paper, a lead-scintillator shower counter using a flourescent radiation converter for collecting scintillation light is described, and the uniformity of energy response and the spatial resolution have been measured.
Journal Article•
TL;DR: This one-step method for the preparation of polyacrylamide gels containing tritium and carbon-14 for liquid scintillation counting is shown to require fewer manipulations but also to eliminate the need for a heating oven and to reduce the reagent costs.
TL;DR: In this paper, the photopeak intensities of 81 γ-rays from 21 elements have been measured using a Ge(Li) detector and 238 Pu-Be source.
TL;DR: The collimator function is developed into a Fourier series and the intensity distribution in the detector plane for a point source is given by a mathematical expression that depends on the object position and on the collimators parameters.
Abstract: A new technique for evaluating the point spread function of parallel hole collimators in scintillation cameras is studied. The collimator function is developed into a Fourier series and the intensity distribution in the detector plane for a point source is given by a mathematical expression that depends on the object position and on the collimator parameters. The septal penetration effect is considered. The technique is applied to obtain the general formulae for collimators with hexagonal holes and the PSF is evaluated.
TL;DR: In this article, a nearly homogeneous assembly of irregularities can produce scintillation which is speciously random, and for such an assembly a peak in scintillation depth is also produced just below the mean fT, where fT marks the boundary between geometric and physical optics.
Abstract: Diffraction patterns produced by isolated irregularities have a maximum fading depth at radio frequencies near 0.6 ƒT where ƒT, the transition frequency, is a property of the electron density irregularity and marks the boundary between geometric and physical optics. A nearly homogeneous assembly of irregularities can produce scintillation which is speciously random. For such an assembly a peak in scintillation depth is also produced just below the mean fT. At radio frequencies below the scintillation is fast and frequency independent; above ƒ¯T the amplitude pattern is directly related to the ionospheric structure.