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Articoli di riviste sul tema "Bent-Laue optics"

Autore: Grafiati

Pubblicato: 14 marzo 2023

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1

Qi, Peng, Xianbo Shi, Nazanin Samadi e Dean Chapman. "Bent Laue crystal anatomy: new insights into focusing and energy-dispersion properties". Journal of Applied Crystallography 54, n. 2 (14 febbraio 2021): 409–26. http://dx.doi.org/10.1107/s1600576720016428.

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Abstract (sommario):

X-ray Laue-type monochromators are common and essential optical components at many high-power X-ray facilities, e.g. synchrotron facilities. The X-ray optics of bent Laue crystals is a well developed area. An incident X-ray beam penetrating a bent Laue crystal will result in a diffracted beam with different angles and energies. There is a need for a way of organizing the rays that allows one to sort out the energy and spatial properties of the diffracted beam. The present work introduces a new approach for describing the general behaviour of bent Laue crystals from a ray-tracing point of view. This quasi-monochromatic beam approach provides an intuitive view of bent-crystal diffraction and leads to deeper understanding. It explains the energy and spatial properties of common and special cases of bent Laue optics, predicts phenomena that can improve energy-dispersion-related X-ray imaging techniques and provides a theoretical framework that makes ray-tracing simulation easier to realize.

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2

Lienert, U., C. Schulze, V. Honkimäki, Th Tschentscher, S. Garbe, O. Hignette, A. Horsewell et al. "Focusing Optics for High-Energy X-ray Diffraction". Journal of Synchrotron Radiation 5, n. 3 (1 maggio 1998): 226–31. http://dx.doi.org/10.1107/s0909049598001393.

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Novel focusing optical devices have been developed for synchrotron radiation in the energy range 40–100 keV. Firstly, a narrow-band-pass focusing energy-tuneable fixed-exit monochromator was constructed by combining meridionally bent Laue and Bragg crystals. Dispersion compensation was applied to retain the high momentum resolution despite the beam divergence caused by the focusing. Next, microfocusing was achieved by a bent multilayer arranged behind the crystal monochromator and alternatively by a bent Laue crystal. A 1.2 µm-high line focus was obtained at 90 keV. The properties of the different set-ups are described and potential applications are discussed. First experiments were performed, investigating with high spatial resolution the residual strain gradients in layered polycrystalline materials. The results underline that focused high-energy synchrotron radiation can provide unique information on the mesoscopic scale to the materials scientist, complementary to existing techniques based on conventional X-ray sources, neutron scattering or electron microscopy.

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3

Nesterets, Ya I., e S. W. Wilkins. "Evaluation of the focusing performance of bent Laue crystals using wave-optical theory". Journal of Applied Crystallography 41, n. 2 (8 marzo 2008): 237–48. http://dx.doi.org/10.1107/s0021889808000617.

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Quantitative analysis of the focusing performance of bent Laue crystals is carried out using the rigorous wave-optical formalism.Vianumerical solution of the Takagi equations and the Fresnel integral, the influence of diffraction on the formation of the image of an X-ray source is analysed. The results are compared with those obtained using a formalism based on the geometrical optics approximation and significant differences are found. A formula for the geometrical aberration of a cylindrically bent crystal is derived. The effect of the aberration on image formation is analysed.

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4

Mazzolari, Andrea, Riccardo Camattari, Valerio Bellucci, Gianfranco Paternò, Carlo Scian, Giovanni Mattei e Vincenzo Guidi. "Manufacturing of advanced bent crystals for Laue Optics for Gamma ObservationS (LOGOS)". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 355 (luglio 2015): 297–300. http://dx.doi.org/10.1016/j.nimb.2015.03.048.

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5

Schulze, C., P. Suortti e D. Chapman. "Test of a bent laue double crystal fixed exit monochromator". Synchrotron Radiation News 7, n. 3 (maggio 1994): 8–11. http://dx.doi.org/10.1080/08940889408261269.

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6

Wu Yufen, 毋玉芬, 肖沙里 Xiao Shali, 鲁建 Lu Jian, 钱家渝 Qian Jiayu, 刘利锋 Liu Lifeng e 黄显宾 Huang Xianbin. "Logarithmic Spiral Bent Laue Crystals for X-Ray Monochromatic Imaging Applications". Chinese Journal of Lasers 40, n. 6 (2013): 0615001. http://dx.doi.org/10.3788/cjl201340.0615001.

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7

Ferrari, Claudio, Elisa Buffagni, Elisa Bonnini e Andrea Zappettini. "X-ray diffraction efficiency of bent GaAs mosaic crystals for the Laue project". Optical Engineering 53, n. 4 (10 aprile 2014): 047104. http://dx.doi.org/10.1117/1.oe.53.4.047104.

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8

Qi, Peng, Nazanin Samadi e Dean Chapman. "X-ray Spectral Imaging Program: XSIP". Journal of Synchrotron Radiation 27, n. 6 (14 settembre 2020): 1734–40. http://dx.doi.org/10.1107/s1600577520010838.

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Abstract (sommario):

Spectral K-edge subtraction imaging and wide-field energy-dispersive X-ray absorption spectroscopy imaging are novel, related, synchrotron imaging techniques for element absorption contrast imaging and element speciation imaging, respectively. These two techniques serve different goals but share the same X-ray optics principles with a bent Laue type monochromator and the same data processing algorithms. As there is a growing interest to implement these novel techniques in synchrotron facilities, Python-based software has been developed to automate the data processing procedures for both techniques. In this paper, the concept of the essential data processing algorithms are explained, the workflow of the software is described, and the main features and some related utilities are introduced.

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9

Bonnini, Elisa, Elisa Buffagni, Andrea Zappettini, Stephen Doyle e Claudio Ferrari. "Surface-treated self-standing curved crystals as high-efficiency elements for X- and γ-ray optics: theory and experiment". Journal of Applied Crystallography 48, n. 3 (25 aprile 2015): 666–71. http://dx.doi.org/10.1107/s1600576715006809.

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The efficiency of a Laue lens for X- and γ-ray focusing in the energy range 60–600 keV is closely linked to the diffraction efficiency of the single crystals composing the lens. A powerful focusing system is crucial for applications like medical imaging and X-ray astronomy where wide beams must be focused. Mosaic crystals with a high density, such as Cu or Au, and bent crystals with curved diffracting planes (CDPs) are considered for the realization of a focusing system for γ-rays, owing to their high diffraction efficiency in a predetermined angular range. In this work, a comparison of the efficiency of CDP crystals and Cu and Au mosaic crystals was performed on the basis of the theory of X-ray diffraction. Si, GaAs and Ge CDP crystals with optimized thicknesses and moderate radii of curvature of several tens of metres demonstrate comparable or superior performance with respect to the higher atomic number mosaic crystals generally used. In order to increase the efficiency of the lens further, a stack of several CDP crystals is proposed as an optical element. CDP crystals were obtained by a surface-damage method, and a stack of two surface-damaged bent Si crystals was prepared and tested. Rocking curves of the stack were performed with synchrotron radiation at 19 keV to check the lattice alignment: they exhibited only one diffraction peak.

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10

Yan, Hanfei, Özgür Kalenci e I. C. Noyan. "Diffraction profiles of elastically bent single crystals with constant strain gradients". Journal of Applied Crystallography 40, n. 2 (12 marzo 2007): 322–31. http://dx.doi.org/10.1107/s0021889807003160.

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This work presents a set of equations that can be used to predict the dynamical diffraction profile from a non-transparent single crystal with a constant strain gradient examined in Bragg reflection geometry with a spherical incident X-ray beam. In agreement with previous work, the present analysis predicts two peaks: a primary diffraction peak, which would have still been observed in the absence of the strain gradient and which exits the specimen surface at the intersection point of the incident beam with the sample surface, and a secondary (mirage) peak, caused by the deflection of the wavefield within the material, which exits the specimen surface further from this intersection point. The integrated intensity of the mirage peak increases with increasing strain gradient, while its separation from the primary reflection peak decreases. The directions of the rays forming the mirage peak are parallel to those forming the primary diffraction peak. However, their spatial displacement might cause (fictitious) angular shifts in diffractometers equipped with area detectors or slit optics. The analysis results are compared with experimental data from an Si single-crystal strip bent in cantilever configuration, and the implications of the mirage peak for Laue analysis and high-precision diffraction measurements are discussed.

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11

Camattari, Riccardo, Gianfranco Paternò, Alessandro Battelli, Valerio Bellucci, Pierre Bastie e Vincenzo Guidi. "High-efficiency focusing of hard X-rays exploiting the quasi-mosaic effect in a bent germanium crystal". Journal of Applied Crystallography 47, n. 2 (28 marzo 2014): 799–802. http://dx.doi.org/10.1107/s1600576714005056.

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A germanium crystal was bent through a grid of superficial grooves, manufactured on the sample surface. The resulting diffraction planes were bent thanks to quasi-mosaicity, which is an effect of mechanical anisotropy in crystals. High integrated diffraction efficiency was achieved in symmetric Laue geometry with a monochromatic X-ray beam set at 150 and 300 keV. It is demonstrated that the sample is capable of efficiently focusing X-rays. Such crystals can be used as optical components to focalize X- and γ-rays in a high-resolution Laue lens.

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12

Shi, Xianbo, Sanjit Ghose, Zhong Zhong, Margareta L. Rehak, Konstantine Kaznatcheev, Peter Z. Takacs e Eric Dooryhee. "Surface curvatures and diffraction profiles of sagittally bent Laue crystals". Journal of Applied Crystallography 44, n. 4 (8 giugno 2011): 665–71. http://dx.doi.org/10.1107/s0021889811018711.

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The performance of a bent Laue crystal monochromator crucially depends on the sagittal and meridional bending curvatures of the crystal. To optimize the design of monochromator crystals, the surface curvatures and diffraction profiles of a set of sagittally bent Laue crystals with different aspect ratios have been studied experimentally by optical metrology and X-ray measurements. The results were confirmed with finite-element analysis using large-deformation theory. The nonlinear relationship between the curvatures necessitates an experimentally determined parameter in the theoretical modeling of the diffraction profiles. By taking into account the local stress and the aspect ratio of the sagittally bent Laue crystal, the modified analytical approach successfully predicts the rocking-curve width and the integrated reflecting power. The effect of extreme sagittal bending on the rocking curve is also discussed. To retain high reflectivity, the bending curvature should not exceed its critical value for the specified crystal geometry. Furthermore, the uniformity of the bending curvatures across the crystal surface has been examined, which suggests that the minimum crystal dimension should be approximately twice the size of the beam footprint.

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13

Mocella, V., C. Ferrero, J. Hrdý, J. Wright, S. Pascarelli e J. Hoszowska. "Experimental verification of dynamical diffraction focusing by a bent crystal wedge in Laue geometry". Journal of Applied Crystallography 41, n. 4 (1 luglio 2008): 695–700. http://dx.doi.org/10.1107/s0021889808017883.

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Recent X-ray optical experiments have validated previous theoretical work on focusing by bent crystals in Laue geometry. It was shown that a suitable choice of the crystal thickness significantly improves the focusing performance of the crystal by combining the dynamical focusing of the Borrmann triangle with the geometrical focusing obtained by the crystal bending. The best focus size achieved during the experiments was less than 5 µm and is in practice limited by the source demagnification for the considered setup.

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14

Chen Can, 陈灿, 佟亚军 Tong Yajun, 任玉琦 Ren Yuqi, 周光照 Zhou Guangzhao, 谢红兰 Xie Honglan e 肖体乔 Xiao Tiqiao. "Study on the Optical Properties of Laue Bent Crystal by Ray-Tracing". Acta Optica Sinica 31, n. 10 (2011): 1034002. http://dx.doi.org/10.3788/aos201131.1034002.

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15

Schulze, Clemens, e Ulf Kleuker. "A bent Laue analyser crystal for Rayleigh-to-Compton computed tomography". Journal of Synchrotron Radiation 5, n. 3 (1 maggio 1998): 1085–87. http://dx.doi.org/10.1107/s0909049597017251.

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A new optical system to perform tomography based on the Rayleigh-to-Compton (RC) method with high spatial and spectral resolution is presented. The RC technique allows the effective atomic number of a sample to be measured and finds application in bone mineral densitometry in medicine. It is particularly useful for the characterization of the distribution of biological materials which do not exhibit distinctive diffraction peaks. The system is based on the separation of the elastic line from the spectrum that is scattered by the sample by means of a bent Laue analyser crystal, and the subsequent independent detection of the elastic and inelastic parts of the spectrum with two large-area scintillation counters. The high energy resolution permits operation at low momentum transfer, where the RC method has its best contrast-to-noise ratio for low-Z materials. The geometrical and spectral requirements in terms of the incident beam and the conical analyser crystal are discussed. A first-generation tomographic imaging system (pencil beam, scanned sample) as implemented at the ESRF Compton-Scattering Station ID15B is described. A high-resolution tomographic reconstruction of a bone sample is presented.

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16

Ferrari, Claudio, Elisa Buffagni, Elisa Bonnini e Dusan Korytar. "High diffraction efficiency in crystals curved by surface damage". Journal of Applied Crystallography 46, n. 6 (26 ottobre 2013): 1576–81. http://dx.doi.org/10.1107/s0021889813022954.

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Diffraction profiles of curved Si and GaAs crystals obtained by a controlled damage process on one side of planar crystals have been investigated at X-ray energiesE= 17, 59 and 120 keV. AtE= 17 and 59 keV in the condition of slight curvature, that is when the diffracting plane bending over the extinction length is lower than the Darwin width, the Laue diffraction profiles with lattice planes parallel or inclined with respect to the curvature radiusRshow an enhancement of integrated intensity proportional to 1/R, much larger than in the corresponding perfect bent crystals. AtE= 120 keV, in the condition of strong curvature, the crystals behave as bent perfect crystals with integrated intensity corresponding to that of a mosaic crystal. These crystals are proposed as optical elements for focusing hard X-ray beams.

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17

Dong, Weiwei, Quan Cai, Fugui Yang, Xu Liu, Jiaowang Yang, Qianshun Diao, Peng Liu, Xiaowei Zhang e Lingfei Hu. "Characterization and on-line adjustment of the sagittal-bent Laue crystal profile". Journal of Synchrotron Radiation 25, n. 5 (2 agosto 2018): 1346–53. http://dx.doi.org/10.1107/s1600577518008056.

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The sagittal-bent Laue monochromator can provide an ideal way to focus high-energy X-ray beams. However, the anticlastic curvature induced by sagittal bending has a great influence on the crystal performance. Thus, characterizing the bent-crystal shape is very important for predicting the performance of the bent-crystal monochromator. In this paper the crystal profile is measured by off-line optical metrology and on-line X-ray experiments. The off-line results showed that the bent-crystal surface could be well fitted to a saddle surface apart from a redundant cubic term which was related to the different couples applied on the crystal. On-line characterization of the meridional and the sagittal radius of the bent crystal includes double-crystal topography and ray-tracing measurement. In addition, the double-crystal topography experiment could be used as a quick diagnostic method for the bending condition adjustment. The sagittal radius of the bent crystal was characterized through a ray-tracing experiment by using a particularly designed tungsten mask. Moreover, rocking curves under different bending conditions were measured as well. The results were highly consistent with analytical results derived from the elastic theory. Furthermore, radii along different vertical positions under various bending conditions were measured and showed a quadratic relationship between the vertical positions and the meridional radii.

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18

Virgilli, Enrico, Vineeth Valsan, Filippo Frontera, Ezio Caroli, Vincenzo Liccardo e John Buchan Stephen. "Expected performances of a Laue lens made with bent crystals". Journal of Astronomical Telescopes, Instruments, and Systems 3, n. 04 (2 ottobre 2017): 1. http://dx.doi.org/10.1117/1.jatis.3.4.044001.

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19

Plancher, E., V. Favier, C. Maurice, E. Bosso, N. Rupin, J. Stodolna, D. Loisnard et al. "Direct measurement of local constitutive relations, at the micrometre scale, in bulk metallic alloys". Journal of Applied Crystallography 50, n. 3 (1 giugno 2017): 940–48. http://dx.doi.org/10.1107/s1600576717006185.

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Multiscale models involving crystal plasticity are essential to predict the elastoplastic behavior of structural materials with respect to their microstructure. However, those models are often limited by a poor knowledge of the local constitutive behavior. This article reports a method to measure the mechanical behavior directly, at the micrometre scale, in bulk crystalline materials. Local strain and stress states were evaluated at the surface of a bent stainless steel crystal by combining total strain measurements – performed with the digital image correlation technique on optical images – with elastic strain measurements obtained by Laue microdiffraction. A local constitutive relation was measured, in an efficient nondestructive way, without the need for full-field simulations. The method was validated by a comparison between the measured local behavior and the macroscopic behavior of the single crystal.

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20

Camattari, Riccardo, Marco Romagnoni, Andrea Mazzolari, Gianfranco Paternò, Vincenzo Guidi e Thomas Buslaps. "Thick self-standing bent crystals as optical elements for a Laue lens for applications in astrophysics". Experimental Astronomy 46, n. 2 (11 settembre 2018): 309–21. http://dx.doi.org/10.1007/s10686-018-9603-4.

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21

Camattari, Riccardo, Gianfranco Paternò, Marco Romagnoni, Valerio Bellucci, Andrea Mazzolari e Vincenzo Guidi. "Homogeneous self-standing curved monocrystals, obtained using sandblasting, to be used as manipulators of hard X-rays and charged particle beams". Journal of Applied Crystallography 50, n. 1 (1 febbraio 2017): 145–51. http://dx.doi.org/10.1107/s1600576716018768.

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A technique to obtain self-standing curved crystals has been developed. The method is based on a sandblasting process capable of producing an amorphized layer on the substrate. It is demonstrated that the amorphized layer behaves as a thin compressive film, causing the curvature of the substrate. This procedure permits the fabrication of homogeneously curved crystals in a fast and economical way. It is shown that a sandblasted crystal can be used as an X-ray optical element for astrophysical or medical applications. A sandblasted bent crystal can also be used as an optical element for steering charged particles in accelerator beamlines. Several samples were manufactured and bent using the sandblasting method at the Sensor and Semiconductor Laboratory of Ferrara, Italy. Their curvature was verified using interferometric profilometry, showing a deformation in agreement with the Stoney formalism. The curvature of the machined samples was also tested using γ-ray diffraction at the Institut Laue–Langevin (ILL), Grenoble, France. A good agreement with the dynamical theory of diffraction was observed. In particular, the experiment showed that the crystalline quality of the bulk was preserved. Moreover, the method allowed curved samples to be obtained free of any additional material. Finally, a crystalline undulator was produced using sandblasting and tested using γ-ray diffraction at the ILL. The crystal showed a precise undulating pattern, so it will be suitable for hard X-ray production.

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22

Kropf, A. J., J. A. Fortner, R. J. Finch, J. C. Cunnane e C. Karanfil. "A Bent Silicon Crystal in the Laue Geometry to Resolve Actinide XRay Fluorescence for XRay Absorption Spectroscopy". Physica Scripta, 2005, 998. http://dx.doi.org/10.1238/physica.topical.115a00998.

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