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X-ray Detectors (x-ray + detector)
Selected AbstractsWorkshop on X-ray Detectors for Synchrotron RadiationJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2004DOI: 10.1107/S090904950400926 First page of article [source] CCD-based X-ray area detector for time-resolved diffraction experimentsJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2004Naoto Yagi A fast X-ray area detector for diffraction, scattering and imaging experiments at microsecond to millisecond time resolution has been developed. The key element of the detector is a fast (291,frames,s,1) framing camera with three CCDs. A prism forms identical images on the CCDs and the frame rate is increased three times by reading them alternately. In order to convert X-rays into visible light that is detectable with the CCDs, an X-ray image intensifier is used. The camera can also be used with a high-resolution X-ray detector. In both cases it was found to be important to use a phosphor with a short decay time to fully make use of the high-speed framing capability of the camera. Preliminary results of a fibre diffraction experiment on a skeletal muscle and coronary angiography are presented. [source] THE TECHNOLOGY OF PRODUCTION OF SASANIAN GLAZED POTTERY FROM VEH ARDA,?R (CENTRAL IRAQ)ARCHAEOMETRY, Issue 4 2008M. PACE Scanning electron microscopy coupled with an energy dispersive X-ray detector (SEM-EDS) has been used to study samples of Sasanian glazed pottery. Analysis of ceramic bodies revealed a general homogeneity in composition among the studied samples and the use of calcareous clay for their manufacture. Glazes are typically alkaline in composition, with sodium and potassium oxide contents between 8 and 13%, and between 3 and 5%, respectively; calcium and magnesium oxide contents are between 7 and 10%, and between 3 and 5%, respectively. These data suggest the use of plant ash together with a silica source for glaze production. Coating thickness is highly variable among different samples, from some 400 up to 1200 µm, but it is generally uniform when a single sample is concerned. Glazes are mostly coloured blue or blue-green; copper and iron are the colouring agents detected; abundance of bubbles, silicate crystals and relics of unmelted material are responsible for their generally opaque appearance, together with the presence of weathering products. The characteristics of the body to glaze contact zone, together with the widespread presence of bubbles, would not rule out production by a single firing process. A few samples feature a peculiar gritty coating on one side of their surface; SEM images show that they are actually partially vitrified, and EDS data denote a rather heterogeneous composition. It seems possible that they result from mixing clay together with the frit used for glaze development. [source] Accuracy of Linear Measurement Provided by Cone Beam Computed Tomography to Assess Bone Quantity in the Posterior Maxilla: A Human Cadaver StudyCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 4 2008Sophie Veyre-Goulet DDS ABSTRACT Purpose: The aim of this study was to assess, for implant placement in the posterior maxilla, the accuracy of linear measurements provided by cone beam computed tomography (CBCT) using an image intensifier tube and television (TV) chain as an X-ray detector despite a loss of contrast resolution. The NewTom® 9000 (Quantitative Radiology, Verona, Italy) was used to explore the posterior maxilla. Materials and Methods: Fourteen measurements were taken in three dry maxillaries. On every anatomical site, three fiducial markers were placed on the bony crest to define a plane. Dry maxillaries were submitted to CBCT imaging examination. The maxillaries were then sawn according to the previously defined planes, and bone height and width were assessed using a caliper. The same measurements were taken on images. Results: Clinical analysis demonstrated no difference between real measurements and image measurements. Conclusions: Although cadaver bone density may not correspond to the density of vital bone, this in vitro study indicates that CBCT images provided by technique using image intensifier tube and TV chain as an X-ray detector are reliable to define the bone volume of the posterior maxilla for the purpose of planning the implant axis. [source] Origin of Radiation-Induced Degradation in Polymer Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Ankit Kumar Abstract Polymer solar cells have been shown to degrade under X-rays. Here, in situ polymer photovoltaic performance and recombination lifetimes are measured and it is found that charge accumulation is the primary reason for degradation of solar cells. This is affected by the mixing ratio of donor and acceptor in the bulk heterojunction. Both a quantitative understanding and the physical model of the degradation mechanism are presented. Understanding of the degradation mechanism is extended in polymer donor,acceptor bulk heterojunction systems to propose a material combination for making radiation hard diodes that can find important application in fields ranging from memory arrays to organic X-ray detectors for medical imaging. [source] Zr and Ba edge phenomena in the scintillation intensity of fluorozirconate-based glass-ceramic X-ray detectorsJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2007Bastian Henke The energy-dependent scintillation intensity of Eu-doped fluorozirconate glass-ceramic X-ray detectors has been investigated in the energy range from 10 to 40,keV. The experiments were performed at the Advanced Photon Source, Argonne National Laboratory, USA. The glass ceramics are based on Eu-doped fluorozirconate glasses, which were additionally doped with chlorine to initiate the nucleation of BaCl2 nanocrystals therein. The X-ray excited scintillation is mainly due to the 5d,4f transition of Eu2+ embedded in the BaCl2 nanocrystals; Eu2+ in the glass does not luminesce. Upon appropriate annealing the nanocrystals grow and undergo a phase transition from a hexagonal to an orthorhombic phase of BaCl2. The scintillation intensity is investigated as a function of the X-ray energy, particle size and structure of the embedded nanocrystals. The scintillation intensity versus X-ray energy dependence shows that the intensity is inversely proportional to the photoelectric absorption of the material, i.e. the more photoelectric absorption the less scintillation. At 18 and 37.4,keV a significant decrease in the scintillation intensity can be observed; this energy corresponds to the K -edge of Zr and Ba, respectively. The glass matrix as well as the structure and size of the embedded nanocrystals have an influence on the scintillation properties of the glass ceramics. [source] Counting statistics of X-ray detectors at high counting ratesJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2003David Laundy Modern synchrotron radiation sources with insertion devices and focusing optics produce high fluxes of X-rays at the sample, which leads to a requirement for photon-counting detectors to operate at high counting rates. With high counting rates there can be significant non-linearity in the response of the detector to incident X-ray flux, where this non-linearity is caused by the overlap of the electronic pulses that are produced by each X-ray. A model that describes the overlap of detector pulses is developed in this paper. This model predicts that the correction to the counting rate for pulse overlap is the same as a conventional dead-time correction. The model is also used to calculate the statistical uncertainty of a measurement and predicts that the error associated with a measurement can be increased significantly over that predicted by Poisson () statistics. The error differs from that predicted by a conventional dead-time treatment. [source] Delayed X-ray emission from fallback in compact-object mergersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2009Elena M. Rossi ABSTRACT When double neutron star or neutron star,black hole binaries merge, the final remnant may comprise a central solar-mass black hole surrounded by a ,0.01,0.1 M, torus. The subsequent evolution of this disc may be responsible for short ,-ray bursts (SGRBs). A comparable amount of mass is ejected into eccentric orbits and will eventually fallback to the merger site after ,0.01 s. In this paper, we investigate analytically the fate of the fallback matter, which may provide a luminous signal long after the disc is exhausted. We find that matter in the eccentric tail returns at a super-Eddington rate and eventually (,0.1 s) is unable to cool via neutrino emission and accrete all the way to the black hole. Therefore, contrary to previous claims, our analysis suggests that fallback matter is not an efficient source of late-time accretion power and unlikely to cause the late-flaring activity observed in SGRB afterglows. The fallback matter rather forms a radiation-driven wind or a bound atmosphere. In both the cases, the emitting plasma is very opaque and photons are released with a degraded energy in the X-ray band. We therefore suggest that compact binary mergers could be followed by an ,X-ray renaissance', as late as several days to weeks after the merger. This might be observed by the next generation of X-ray detectors. [source] 2D mapping of the response of CVD diamond X-ray detectors: defects and device dynamicsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2004M. J. Guerrero Abstract To investigate the influence of intrinsic defects in polycrystalline CVD diamond, we have used a micro-focused X-ray beam to induce local photo-currents in solid state ionisation chambers. The device behaviour was studied as a function of the defect level populations. This microscopic study of the X-ray sensitivity was then performed using varying initial states of the devices as well as varying device temperatures. These measurements, coupled with the study of the temporal evolution of the photocurrent as a function of the temperature, seemed to demonstrate the existence of highly localised regions that may detrimentally affect the overall device response. This may demonstrate that the imperfections CVD diamond devices exhibit may be caused by extremely localised point defects. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Extension of a tuned log spiral of revolution fluorescence XAFS detector, designed for optimal detection of a particular element Z, to XAFS of elements other than ZJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001D. M. Pease Recently, it has been demonstrated that an x-ray detector in the form of a log spiral of revolution, covered with highly oriented pyrolytic graphite, is an excellent device for obtaining the fluorescence XAFS of an element of interest in the presence of competing fluorescence from other elements. In the present work we investigate the capabilities of a log spiral of revolution (LSR) detector, with a geometry optimized for one element (in this case Cr), if used for XAFS of other elements. [source] | ||||||||||