1,721,067 research outputs found
Metal sheets thickness determined by energy-dispersive X-ray fluorescence analysis
No full textA portable EDXRF equipment was employed to analyze pre-Columbian metals (gold, silver and copper objects) and to determine the thickness of gold in the case of gildings. To this aim, the EDXRF equipment was optimized to detect Cu, Au and Ag, and various methods were developed to determine from X-ray spectra (K-lines ratio) the thickness of the gildings. These methods were first tested to measure gilding compositions and thicknesses of pens and decorative objects. Then pre-Columbian metals were analyzed, such as gold, silver, copper, gilded copper and gilded silver objects from the Royal Tomb of Sipán and from the Museum of Sicán, in the north of Peru
X – Ray Fluorescence - Analysis Of XIX Century Stamps
No full textLatin-American stamps of the period 1850-1900 were analyzed and scanned with a portable x-ray fluorescence equipment composed of a small size x-ray tube and a Si-PIN detector with a capillary collimator, with the aim of identifying their characteristic pigments, establishing in which period of time pigments containing inorganic components have been employed and their evolution vs time
Non-destructive analysis of ancient metal alloys by in situ EDXRF transportable equipment
No full textThe availability of transportable equipment for in situ non-destructive analysis of works of art is considered to be very important. In situ non- destructive study is typically diagnostic, therefore requiring only qualitative or semiquantitative results. In the case of alloys, quantitative results can also be obtained. In Energy Dispersive X-Ray Fluorescence (EDXRF) analysis, portable instruments can now be assembled. For instance, miniaturised X-ray tubes with air cooling and high resolution semiconductor detectors thermoelectrically cooled are now available, allowing the construction of completely transportable apparatus for EDXRF analysis. In this work, aspects regarding methodology of analysis and discussion of the precision obtainable in analysis of ancient metals are presented.The availability of transportable equipment for in situ non-destructive analysis of works of art is considered to be very important. In situ non-destructive study is typically diagnostic, therefore requiring only qualitative or semiquantitative results. In the case of alloys, quantitative results can also be obtained. In Energy Dispersive X-Ray Fluorescence (EDXRF) analysis, portable instruments can now be assembled. For instance, miniaturised X-ray tubes with air cooling and high resolution semiconductor detectors thermoelectrically cooled are now available, allowing the construction of completely transportable apparatus for EDXRF analysis. In this work, aspects regarding methodology of analysis and discussion of the precision obtainable in analysis of ancient metals are presented
The use of a European coinage alloy to compare the detection limits of mobile XRF systems. A feasibility study
No full textThe investigation of archaeological and historical materials makes use of techniques that, though borrowed from other fields of research and industrial production, frequently have to be 're-invented' because of peculiar characteristics of the analysed objects. Artistic relevance, limited movability, compositional and structural heterogeneity radically change the experimental approach and often require ad hoc designed equipment. These considerations also apply to x-ray fluorescence, especially regarding mobile systems. The extensive development and use of mobile spectrometers has produced an extremely diversified context and created the need for common criteria to evaluate their performances as; well as the advisability of a survey on the existing equipment. This paper shows the feasibility of such an idea through a demonstrative survey that was carried out among users of different mobile x-ray fluorescence spectrometry (XRF) systems in the areas of Rome, Italy and Valencia, Spain. The experimental protocol was based on measuring spectrometer detection limits with the single standard method. The standard was the 50 eurocent coin, whose alloy is made of 89% Cu, 5% Al, 5% Zn, 1% Sn; the large spread of the European currency guarantees maximum availability. The experimental data show that the use of different x-ray tubes and detectors results in detection limits that may differ from each other by a factor of 6 for Zn and almost 100 for Sn; despite the large number of variables that in principle affect the performance, it was observed that the high voltage of the x-ray tube is the most important paramete
Energy Dispersive X-Ray Fluorescence Analysis of Thin and Intermediate Environmental Samples
No full textPigment layers and precious metal sheets by energy-dispersive x-ray fluorescence analysis
No full textA portable energy-dispersive x-ray fluorescence (EDXRF) equipment was used to measure pigments and precious metal composition. From the x-ray spectra it was also possible to assign each pigment to the correct pigment layer, and in the case of metal sheets (e.g. gildings) to identify the correct layer distribution. Several methods have also been developed to determine the thickness of pigment layers and metal sheets. They were specifically applied to measure gold thickness in Giotto's halos in the Chapel of the Scrovegni in Padua, and in gilded copper objects from the Royal Tombs of Sipán and from the Museum of Sicán
Computed tomography with image intensifier : Potential use for Non-Destructive testing and imaging of small objects
No full textAn image intensifier based computed tomography scanner and a tube source of X-rays are used for nondestructive evaluation, imaging of objects for archaeological studies and conservation of works of art and micro analysis of soft materials. It consists of a charge coupled device (CCD) camera and an acquisition board. The CCD camera and the acquisition board allow image processing, filtration and restoration. The object is irradiated by an X-ray tube with a conical collimator and rotated on 180°. Projections are obtained at various angles as cross sectional image slices. A reconstruction program written in PASCAL is able to give the reconstruction matrix of the linear attenuation coefficients, simulates the matrix and related tomography. The flux emitted by the tube is filtered using the appropriate filters at the chosen optimum energy and reasonable monochromacy is achieved for all the images. Although X-ray imaging is a potential tool for strongly attenuating materials, the images of weakly attenuating materials provide new information to know about their structure and also the foreign body for the image reconstruction at an optimum value. The image of the plastic material which contains the internal defect is studied thoroughly at the optimum value in order to image the small objects for nondestructive testing, archaeological studies and conversation of works of art. The images are analyzed using the profile data showing the internal defect of the object to obtain information at the optimum value. At the optimum value and with the aid of the tomographic image, the size and location of the defect could be ascertained
90° Compton and Rayleigh measurements and imaging
No full textA simple apparatus for measurement and imaging of objects using scattered X-rays was designed and constructed. This is composed of a well-collimated photon beam from an X-ray tube, a CZT thermoelectrically cooled semiconductor detector and an (x, y, θ) translation-rotation table containing the object to be studied. First, the output beam was monochromatized; studies on Compton and Rayleigh scattered radiation were then carried out, including the Compton profile. Then direct bremsstrahlung radiation of proper energy was employed, and energy intervals are selected where Rayleigh or Compton effects largely prevail. Compton images were finally obtained
Volume of intersection of two cones
No full textRadiation measurements utilising collimated source and detector systems invariably result in a target volume described by the overlap of their fields of view. When these collimators are cylindrical, this is derived from the volume of intersection of two cones. In general, analysis of this volume does not lend itself to a direct analytical process. Here, numerical methods of estimating the common volume of two intersecting right cones are presented. These include methods which employ, (a) a sequential scanning of an elemental volume with a predetermined size across a defined space containing the volume of interest and (b) a Monte Carlo technique. The accuracy obtainable and the execution time in the first type of algorithm depend on the size of the elemental volume (bin-size). On the other hand, these two parameters are independent of the bin-size but dependent on the number of histories sampled, for the Monte Carlo technique. At 0°angle of inclination, where an analytical estimation is easily obtained, the three algorithms considered here resulted in values with a precision better than 0.1% when compared to the analytically calculated one
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