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Coded Aperture X-Ray Diffraction Tomography
Published in Joel Greenberg, Krzysztof Iniewski, X-Ray Diffraction Imaging, 2018
Given the rich information present in the XRD signal, the next question becomes how to design a measurement system to determine f(q). To address this issue, we first consider the case of a single, thin sample material placed at a known location. Equation (1.2) shows that there are two different (although not mutually exclusive) methods for experimentally measuring f(q), which are referred to as angle-dispersive XRD (ADXRD) and energy-dispersive XRD (EDXRD). In ADXRD, one measures the scatter intensity over a range of deflection angles at a single X-ray energy so that each angle uniquely corresponds to the scatter intensity at a particular q value (see Figure 1.4a). This can be accomplished in practice by using a well-collimated incident beam with either a monoenergetic (or narrowband) spectrum or by using a single energy channel from an energy-resolving detector. Alternatively, EDXRD involves measuring the XRD signal intensity over a range of energies for a fixed deflection angle (see Figure 1.4b).2 One can implement an EDXRD scheme by illuminating the sample with a well-collimated, broadband X-ray beam and detecting the scatter using a range of energy channels from a collimated, energy-sensitive detector. Here, each energy corresponds to the scatter intensity at a particular value of momentum transfer. While the majority of commercial diffractometers make use of an ADXRD configuration for prepared sample analysis because of the excellent achievable momentum transfer resolution, EDXRD has the advantage that it can be more compact and operate without moving parts.
CdTe and CdZnTe Small Pixel Imaging Detectors
Published in Salah Awadalla, Krzysztof Iniewski, Solid-State Radiation Detectors, 2017
Traditionally, x-ray diffraction measurements have been made in either energy-dispersive (EDXRD) or angular-dispersive (ADXRD) modes. In the EDXRD technique, the scattering angle is fixed and a polychromatic beam illuminates the sample, while in ADXRD a monochromatic x-ray beam illuminates the sample, and the diffracted intensity is measured while the angle of the beam is changed. Each of these techniques has its own advantages and disadvantages. ADXRD measurements are fast and produce data with very good Bragg peak resolution, but the technique requires mechanical movement of the sample. In EDXRD, the sample remains stationary, but the measured signal is blurred due to the angular range covered by the detector and requires accurate collimation to define the scattering geometry. The use of a spectroscopic imaging detector, such as HEXITEC, allows the EDXRD and ADXRD techniques to be combined into one single technique. Each pixel of the HEXITEC detector subtends a fixed angle in the range 0.6°–15.5° that can be accurately calibrated using known samples. If the angular data are combined with the energy-dispersive spectra collected by each pixel, the diffraction signature of different materials can be accurately determined.
Research on the fine identification of coal types and gangue based on X-ray diffraction principle
Published in International Journal of Coal Preparation and Utilization, 2022
Yanqiu Zhao, Shuang Wang, Yongcun Guo, Gang Cheng, Lei He, Wenshan Wang
Coal is not crystalline, but a fraction of ordered carbon exists within it which formed by stacking several aromatic structural units in coal at different degrees of parallelism, called microcrystals (Xiang, Zeng, and Liang et al. 2016). X-ray diffraction analysis is the main method to study the phase and crystal structure of a substance, which is divided into two implementations: Angular dispersive X-ray diffraction (ADXRD) and Energy dispersive X-ray diffraction (EDXRD). ADXRD is widely used in coal quality analysis (Li et al. 2009). Luo et al. (Luo and Li 2004) calculated the XRD structural parameters of lignite, non-caking coal, weakly sticky coal, gas coal, and rich coal, and obtained the transformation law of aromatic structural units of the samples. Everson et al. (Everson et al. 2013) studied the change process of microcrystalline structure in coal during gasification and combustion by X-ray diffraction. These studies lay a solid theoretical foundation for the application of XRD theory in the fine identification of coal types and gangue. Compared with ADXRD, the EDXRD is widely used in the real-time detection of items due to the advantages of simple system structure and high efficiency (Luggar, Farquharson, and Horrocks et al. 1998). Tongji University also proposed the application of “X-ray diffraction” in the security inspection to achieve the accurate detection of luggage and express boxes (Chen et al. 2019). However, few applications of EDXRD in coal and gangue recognition have been reported, so this paper explores the X-ray diffraction principle combined with machine learning for the recognition of coal types and gangue.