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New Developments in Lead-Paint Film Analysis with Field Portable X-Ray Fluorescence Analyzer
Published in Joseph J. Breen, Cindy R. Stroup, Lead Poisoning, 2020
S. Piorek, J. R. Pasmore, B. D. Lass, J. Koskinen, H. Sipila
Since the resolution of either proportional or scintillation counters does not allow for direct extraction of the net lead peak intensity from an X-ray spectrum, indirect methods are employed. These methods require two consecutive measurements of the sample, without and with a special X-ray filter between the sample and detector. The difference between the two measurements is used as a measure of the net lead signal. This approach is limited, as it does not correct for variances in the energy distribution of the Compton scattered radiation, which, in turn, changes the transmission characteristics of the filter used. This phenomenon is the main reason why all conventional lead analyzers are substrate sensitive.
Semiconductor Sensors for XRD Imaging
Published in Joel Greenberg, Krzysztof Iniewski, X-Ray Diffraction Imaging, 2018
Krzysztof Iniewski, Adam Grosser
Most detection systems take linear projections through the luggage travelling on a conveyor belt in a so-called line scan mode. The detectors used are efficiently collimated linear arrays. For dual-energy capabilities, two solutions have been used. In the first technique, the linear scan is performed twice, once without, and then repeated with an additional X-ray filter in front of the beam. In this way, an elementary technique of low- and high-energy photon separation can be obtained. Similarly, the first scan can be performed at 1 kVp tube voltage (e.g., 140 kVp) and the second at another (e.g., at 80 keVp).
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Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
X-ray has a short wavelength and the refraction factor is nearly 1 for every substance; therefore, optical elements that are used under ordinary visible light cannot be used. Normally, spectral elements using Bragg reflection by a single crystal are used. Suppose that the grid interval of the crystal is represented by d, the oblique incidence angle to x-ray crystal (angle from crystal plane) by θ, wavelength by λ, and when nλ = 2d sin θ (n is integer) is satisfied, a diffraction light can obtain a reinforcing reflection. Further, an x-ray filter is available, which is made of a thin film for selecting character x-ray from x-rays generated in x-ray tubes. Of elements that have been attracting attention currently, an optical element that is able to reflect x-ray or to form an image in the wavelength region referred to as soft x-ray (wavelength several 1/10 ~ several tens nm) is mentioned. Since the refraction factor of substances in the soft x-ray region is slightly smaller than 1, contrary to visible light, total reflection is caused when soft x-ray is incident to substances. However, since there is absorption, 100% reflectance is not obtained as observed with visible light. Figure 4.2a shows a representative Wolter-type optical system. This system consists of a hyperboloid of revolution in which one focal point is shared and an ellipsoid of revolution (or paraboloid of revolution). Since incidence to a mirror surface should be made with an extremely small oblique incidence angle, an imaging system with a large numerical aperture is not produced, but chromatic aberration is less and this optical system can be used in a broader wavelength region. Furthermore, the light from an x-ray light source of continuous wavelength can be used effectively.
Euler characteristic during drying of porous media
Published in Drying Technology, 2022
Yi-Hsuan Shih, Shao-Yiu Hsu, Qun-Zhan Huang, Krzysztof Lamorski, Ming-Che Hu, Chia-Wen Tsao, Cezary Sławiński, Nima Shokri
X-ray CT scans were conducted with a Phoenix Nanotom 180 S device (GE, USA). Two types of scans were performed: a detailed, high-quality scan for the dry specimen to be used as a reference for image analysis and fast scans for the wetted sample in subsequent stages of the drying experiment. For the CT scans of the wetted sample at different stages of the experiment, the priority was to minimize the scanning time (keeping reasonable image quality) to reduce possible phase distribution changes during scanning. In such cases, the duration of each scan was one hour. The other X-ray CT scan parameters were the same for both types of scans: X-ray source voltage of 100 kV; X-ray source current of 130 µA; and voxel size of 5 µm. A tungsten exit window was used in the X-ray lamp together with a 0.2 mm copper X-ray filter.