Crystal Monochromator Research Articles

The high-energy x-ray diffraction and scattering beamline at the Canadian Light Source.

The optical design for the high-energy x-ray diffraction and scattering beamline of the Brockhouse sector at the Canadian Light Source is described. The design is based on a single side-bounce silicon focusing monochromator that steers the central part of a high-field permanent magnet wiggler beam into the experimental station. Two different configurations are proposed: a higher energy resolution with vertical focusing and a lower energy resolution with horizontal and vertical focusing. The monochromator will have the possibility of mounting three crystals: one crystal optimized for 35 keV that focuses in the horizontal and vertical directions using reflection (1,1,1) and two other crystals both covering the energies above 40 keV: one with only vertical focusing and another one with horizontal and vertical focusing. The geometry of the last two monochromator crystals was optimized to use reflections (4,2,2) and (5,3,3) to cover the broad energy range from 40 to 95 keV.

Conceptual design of a new high-resolution powder diffractometer at Jordan Research and Training Reactor

The Jordan Research and Training Reactor (JRTR) has started its full power operation of 5 MW, upgradable to 10 MW, since December 7, 2016. Currently, the JRTR is planning to install a new high-resolution powder diffractometer (HRPD) at the ST1 beam tube in the near future. This study aims to design an optimum HRPD based on the specifications and characteristics of the JRTR. This investigation is based on the manipulation of the components of HRPD such as monochromator crystals, collimators, detectors, and samples by using McStas software. This study shows that the Jordanian HRPD can achieve a neutron flux up to ∼106 n/cm2·s at a sample position with a good resolution of Δd/d = 2.0 × 10−3. The detection system can cover a large range of scattering angles [5°, 165°] by using an array of 64 He-3 position-sensitive detectors provided with 10 arc min of a Soller collimator in front of each detector.

Trace element analysis by EPMA in geosciences: detection limit, precision and accuracy

Use of the electron probe microanalyser (EPMA) for trace element analysis has increased over the last decade, mainly because of improved stability of spectrometers and the electron column when operated at high probe current; development of new large-area crystal monochromators and ultra-high count rate spectrometers; full integration of energy-dispersive / wavelength-dispersive X-ray spectrometry (EDS/WDS) signals; and the development of powerful software packages. For phases that are stable under a dense electron beam, the detection limit and precision can be decreased to the ppm level by using high acceleration voltage and beam current combined with long counting time. Data on 10 elements (Na, Al, P, Ca, Ti, Cr, Mn, Co, Ni, Zn) in olivine obtained on a JEOL JXA-8230 microprobe with tungsten filament show that the detection limit decreases proportionally to the square root of counting time and probe current. For all elements equal or heavier than phosphorus (Z = 15), the detection limit decreases with increasing accelerating voltage. The analytical precision for minor and trace elements analysed in olivine at 25 kV accelerating voltage and 900 nA beam current is 4 - 18 ppm (2 standard deviations of repeated measurements of the olivine reference sample) and is similar to the detection limit of corresponding elements. To analyse trace elements accurately requires careful estimation of background, and consideration of sample damage under the beam and secondary fluorescence from phase boundaries. The development and use of matrix reference samples with well-characterised trace elements of interest is important for monitoring and improving of the accuracy. An evaluation of the accuracy of trace element analyses in olivine has been made by comparing EPMA data for new reference samples with data obtained by different in-situ and bulk analytical methods in six different laboratories worldwide. For all elements, the measured concentrations in the olivine reference sample were found to be identical (within internal precision) to reference values, suggesting that achieved precision and accuracy are similar. The spatial resolution of EPMA in a silicate matrix, even at very extreme conditions (accelerating voltage 25 kV), does not exceed 7 - 8 μm and thus is still better than laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) or secondary ion mass spectrometry (SIMS) of similar precision. These make the electron microprobe an indispensable method with applications in experimental petrology, geochemistry and cosmochemistry.

The application of interference fits for overcoming limitations in clamping methodologies for cryo-cooling first crystal configurations in x-ray monochromators

The work detailed here describes how a novel approach has been applied to overcome the challenging task of cryo-cooling the first monochromator crystals of many of the world’s synchrotrons’ more challenging beam lines. The beam line configuration investigated in this work requires the crystal to diffract 15 Watts of 4-34 keV X-ray wavelength and dissipate the additional 485 watts of redundant X-ray power without significant deformation of the crystal surface. In this case the beam foot print is 25 mm by 25 mm on a crystal surface measuring 38 mm by 25 mm and maintain a radius of curvature of more than 50 km. Currently the crystal is clamped between two copper heat exchangers which have LN2 flowing through them. There are two conditions that must be met simultaneously in this scenario: the crystal needs to be clamped strongly enough to prevent the thermal deformation developing whilst being loose enough not to mechanically deform the diffracting surface. An additional source of error also occurs as the configuration is assembled by hand, leading to human error in the assembly procedure. This new approach explores making the first crystal cylindrical with a sleeve heat exchanger. By manufacturing the copper sleeve to be slightly larger than the silicon crystal at room temperature the sleeve can be slid over the silicon and when cooled will form an interference fit. This has the additional advantage that the crystal and its heat exchanger become a single entity and will always perform the same way each time it is used, eliminating error due to assembly. Various fits have been explored to investigate the associated crystal surface deformations under such a regime

Note: Measurement of synchrotron radiation phase-space beam properties to verify astigmatism compensation in Fresnel zone plate focusing optics.

The intensity distribution in phase space of an X-ray synchrotron radiation beamline was measured using a pinhole camera method, in order to verify astigmatism compensation by a Fresnel zone plate focusing optical system. The beamline is equipped with a silicon double crystal monochromator. The beam size and divergence at an arbitrary distance were estimated. It was found that the virtual source point was largely different between the vertical and horizontal directions, which is probably caused by thermal distortion of the monochromator crystal. The result is consistent with our astigmatism compensation by inclining a Fresnel zone plate.

Simulation and optimization of a new focusing polarizing bender for the diffuse neutrons scattering spectrometer DNS at MLZ

We present the concept and the results of the simulations of a new polarizer for the diffuse neutron scattering spectrometer DNS at MLZ. The concept of the polarizer is based on the idea of a bender made from the stack of the silicon wafers with a double-side supermirror polarizing coating and absorbing spacers in between. Owing to its compact design, such a system provides more free space for the arrangement of other instrument components. To reduce activation of the polarizer in the high intensity neutron beam of the DNS spectrometer we plan to use the Fe/Si supermirrors instead of currently used FeCoV/Ti:N ones. Using the VITESS simulation package we have performed simulations for horizontally focusing polarizing benders with different geometries in the combination with the double-focusing crystal monochromator of DNS. Neutron transmission and polarization efficiency as well as the effects of the focusing for convergent conventional C-benders and S-benders have been analyzed both for wedge-like and plane-parallel convergent geometries of the channels. The results of these simulations and the advantages/disadvantages of the various configurations are discussed.

Geomorfología y sedimentología del sistema de cárcavas en el borde costero al suroeste del Castillo de Araya, Estado Sucre, Venezuela

The study area is located in the south-west coast of Araya in Sucre State, between 10° 33’30” N, 10°33’59” N y 64°15’32” W, 64°15’36” W, which it is affected by erosion processes impacting the population center that sits there. Hence the research is to analyze the geomorphological processes developed, based on a model no-experimental and design field, in descriptive and explanatory levels, operationalized in three phases: a) field, to collect 21 samples of surface sediment (0-20 cm) distributed in 12 samples in the first badlands and 9 samples in the second and lift the morphometry of these landforms erosion; (b) image analysis, three stages such as the development of thematic maps from the Topographical maps of Cumana, Geological Araya Peninsula and The Cadastral Charter covered: Punta Caracare; followed by drawing sketches of gullies, from the data collected in the field, refer to height, length and width of the land. Corresponding to the last two variables data were corrected by the equation suggested by Wolf and Ghilani (2008), for data collected on slopes using measuring tape; and finally drawing the sketch of the apical cliff line drawn from the interpretation of the captured images of Google Earth for the years 2003, 2006, 2009 and 2011, based on the proposal of Soriano (2009) and (c) laboratory, to analyze the comportamientode physical properties such as: hygroscopic water content, determined by gravimetric method, based on the arguments presented by Rivera, et al. (2006) and Toledo (2009); size distribution of the particles (Method Bouyoucos) following the protocol reported by Lara (1985); Percentage of dispersion and soil (double hydrometer method) based on the specifications referred by porters and Alva (1999). As for the chemical-mineralogical properties, it was determined from 10 samples analysis of total rocks and clay mineralogy, for both analyzes samples were prepared, processed and analyzed in the laboratory Diffraction x-ray (xrd), assigned to the Departmental Management Exploration pdvsa-intevep. Being used for analysis brand panalytical diffractometer X’Pert model equipped with a curved crystal monochromator graphite (Cu Ka radiation) and operated by the X-Pert Data collector ltupw3240 / 92 (version 2.2b) software, applying a range scanning of 5 ° θ 45 ° θ. For all rock and 0 2 ° to 35 ° θ clay minerals for less than 2 microns (<2μ) fraction. As to biochemical properties, the organic carbon were analyzed on the floor (COs) using in method Wlakley and Black, reported by Arrieche and Pacheco (sf) and Toledo (2008), and content of organic matter (mo) by the conventional factor Vammelen, referred to by Navarro (2007) and Toledo (2008) and checked against the proposal by palmaven (1992) qualitative scale In general, you have to cliff erosion affected by the retrograde type badlands, It consists of a material silt loam, total analysis rocks which shows an abundance of clay (52%), silicon oxide (28%), calcium carbonate (18%), plagioclase (5%), iron sulfide (5%) and iron carbonate (2%), meanwhile, clays analysis lesser fraction two microns shows as predominant: Kaolinite (47%), Illite (39%), Chlorite (14%), and Smectic (1%). This is a dispersive and expansive regolith, with very low organic matter content, which favors the occurrence of current washout, soil and collapse of rock, possibly detonated from the slight increase in rainfall recorded between July and November, as well as the steep terrain, which has generated a decrease of apical contour, estimated at 1.31 m * year-1.

Bent Crystal Laue Monochromatorによる表面敏感XAFSの測定と燃料電池触媒への応用

Bent Crystal Laue Monochromatorによる表面敏感XAFSの測定と燃料電池触媒への応用

The crystal monochromator beamline KMC-1 at BESSY II

The KMC-1 is a soft x-ray double crystal monochromator beamline for the energy range between 2 and 12 keV. The bending magnet beamline as well as the experiment are under UHV-condition. It incorporates high indexed Si-crystals for high resolution and it is primarily used for HAXPES experiments employing the HIKE (High Kinetic Energy Photoelectron Spectroscopy) chamber.

Multi-dimensional optimization of a terawatt seeded tapered Free Electron Laser with a Multi-Objective Genetic Algorithm

There is a great interest in generating high-power hard X-ray Free Electron Laser (FEL) in the terawatt (TW) level that can enable coherent diffraction imaging of complex molecules like proteins and probe fundamental high-field physics. A feasibility study of producing such X-ray pulses was carried out employing a configuration beginning with a Self-Amplified Spontaneous Emission FEL, followed by a “self-seeding” crystal monochromator generating a fully coherent seed, and finishing with a long tapered undulator where the coherent seed recombines with the electron bunch and is amplified to high power. The undulator tapering profile, the phase advance in the undulator break sections, the quadrupole focusing strength, etc. are parameters to be optimized. A Genetic Algorithm (GA) is adopted for this multi-dimensional optimization. Concrete examples are given for LINAC Coherent Light Source (LCLS) and LCLS-II-type systems. Analytical estimate is also developed to cross check the simulation and optimization results as a quick and complimentary tool.

Multiple energy synchrotron biomedical imaging system

A multiple energy imaging system that can extract multiple endogenous or induced contrast materials as well as water and bone images would be ideal for imaging of biological subjects. The continuous spectrum available from synchrotron light facilities provides a nearly perfect source for multiple energy x-ray imaging. A novel multiple energy x-ray imaging system, which prepares a horizontally focused polychromatic x-ray beam, has been developed at the BioMedical Imaging and Therapy bend magnet beamline at the Canadian Light Source. The imaging system is made up of a cylindrically bent Laue single silicon (5,1,1) crystal monochromator, scanning and positioning stages for the subjects, flat panel (area) detector, and a data acquisition and control system. Depending on the crystal’s bent radius, reflection type, and the horizontal beam width of the filtered synchrotron radiation (20–50 keV) used, the size and spectral energy range of the focused beam prepared varied. For example, with a bent radius of 95 cm, a (1,1,1) type reflection and a 50 mm wide beam, a 0.5 mm wide focused beam of spectral energy range 27 keV–43 keV was obtained. This spectral energy range covers the K-edges of iodine (33.17 keV), xenon (34.56 keV), cesium (35.99 keV), and barium (37.44 keV); some of these elements are used as biomedical and clinical contrast agents. Using the developed imaging system, a test subject composed of iodine, xenon, cesium, and barium along with water and bone were imaged and their projected concentrations successfully extracted. The estimated dose rate to test subjects imaged at a ring current of 200 mA is 8.7 mGy s−1, corresponding to a cumulative dose of 1.3 Gy and a dose of 26.1 mGy per image. Potential biomedical applications of the imaging system will include projection imaging that requires any of the extracted elements as a contrast agent and multi-contrast K-edge imaging.

A monochromatic x-ray irradiation system for in vitro studies at synchrotron beamlines

The use of synchrotron light in radiobiological keV x-ray in vitro studies has been accompanied by compromises in culture conditions and sample handling procedures. The presented monochromatic x-ray system bridges the gap between synchrotron science and cell biology by facilitating the irradiation of adherent cells uninterruptedly maintained under cell type-specific conditions throughout the entire experiment. The system for horizontal irradiations consists of a single crystal Laue monochromator, a beam monitor, and a scanning sample stage. As implemented at the BMIT-BM beamline, the system enables homogeneous cell culture irradiations with intense and purely monochromatic x-ray beams (10–30 keV). The first MCF-7 dose-response study demonstrates how the establishment of a stress-minimized experimental procedure leads to accurate and precise in vitro irradiation results. The cell survival as a function of the surface dose is well described by a first-order exponential decay, indicating that the cellular damage induced by 11.9 keV x-rays is comparable to the lethal effects caused by high linear energy transfer particles. The system design opens up the pathway for combined live-cell imaging and monochromatic keV x-ray applications, while the implementation of the system at insertion device beamlines can help to establish novel investigations on the fundamental role of photonactivation agents in an energy regime up to 100 keV.

Development of the neutron diffraction method for stress measurements in thick steel samples.

The results of development of neutron method for stress measurements in bulk steel components are considered. Enhancement of the maximum available path length (∼⃒85mm) was achieved by using optimized bent perfect silicon crystal monochromators, position sensitive detectors and neutron wavelengths, corresponding to the minimums of neutron total cross section near Bragg edges.

Slow neutron total cross-section, transmission and reflection calculation for poly- and mono-NaCl and PbF2 crystals

A detailed study about the calculation of total neutron cross-section, transmission and reflection from crystalline materials was performed. The developed computer code is approved to be sufficient for the required calculations, also an excellent agreement has been shown when comparing the code results with the other calculated and measured values. The optimal monochromator and filter parameters were discussed in terms of crystal orientation, mosaic spread, and thickness. Calculations show that 30cm thick of PbF2 poly-crystal is an excellent cold neutron filter producing neutron wavelengths longer than 0.66nm needed for the investigation of magnetic structure experiments. While mono-crystal filter PbF2 cut along its (111), having mosaic spread (η=0.5°) and thickness 10cm can only transmit thermal neutrons of the desired wavelengths and suppress epithermal and γ-rays forming unwanted background, when it is cooled to liquid nitrogen temperature. NaCl (200) and PbF2 (111) monochromator crystals having mosaic spread (η=0.5°) and thickness 10mm shows high neutron reflectivity for neutron wavelengths (λ=0.114nm and λ=0.43nm) when they used as a thermal and cold neutron monochromators respectively with very low contamination from higher order reflections.

The new NCPSS BL19U2 beamline at the SSRF for small-angle X-ray scattering from biological macromolecules in solution.

The beamline BL19U2 is located in the Shanghai Synchrotron Radiation Facility (SSRF) and is its first beamline dedicated to biological material small-angle X-ray scattering (BioSAXS). The electrons come from an undulator which can provide high brilliance for the BL19U2 end stations. A double flat silicon crystal (111) monochromator is used in BL19U2, with a tunable monochromatic photon energy ranging from 7 to 15 keV. To meet the rapidly growing demands of crystallographers, biochemists and structural biologists, the BioSAXS beamline allows manual and automatic sample loading/unloading. A Pilatus 1M detector (Dectris) is employed for data collection, characterized by a high dynamic range and a short readout time. The highly automated data processing pipeline SASFLOW was integrated into BL19U2, with help from the BioSAXS group of the European Molecular Biology Laboratory (EMBL, Hamburg), which provides a user-friendly interface for data processing. The BL19U2 beamline was officially opened to users in March 2015. To date, feedback from users has been positive and the number of experimental proposals at BL19U2 is increasing. A description of the new BioSAXS beamline and the setup characteristics is given, together with examples of data obtained.

Rotation of X-ray polarization in the glitches of a silicon crystal monochromator.

EXAFS studies on dilute samples are usually carried out by collecting the fluorescence yield using a large-area multi-element detector. This method is susceptible to the 'glitches' produced by all single-crystal monochromators. Glitches are sharp dips or spikes in the diffracted intensity at specific crystal orientations. If incorrectly compensated, they degrade the spectroscopic data. Normalization of the fluorescence signal by the incident flux alone is sometimes insufficient to compensate for the glitches. Measurements performed at the state-of-the-art wiggler beamline I20-scanning at Diamond Light Source have shown that the glitches alter the spatial distribution of the sample's quasi-elastic X-ray scattering. Because glitches result from additional Bragg reflections, multiple-beam dynamical diffraction theory is necessary to understand their effects. Here, the glitches of the Si(111) four-bounce monochromator of I20-scanning just above the Ni K edge are associated with their Bragg reflections. A fitting procedure that treats coherent and Compton scattering is developed and applied to a sample of an extremely dilute (100 micromolal) aqueous solution of Ni(NO3)2. The depolarization of the wiggler X-ray beam out of the electron orbit is modeled. The fits achieve good agreement with the sample's quasi-elastic scattering with just a few parameters. The X-ray polarization is rotated up to ±4.3° within the glitches, as predicted by dynamical diffraction. These results will help users normalize EXAFS data at glitches.

On the influence of monochromator thermal deformations on X-ray focusing

A cooled double crystal monochromator system is used on many high heat load X-ray synchrotron radiation beamlines in order to select, by diffraction, a narrow spectrum of the beam. Thermal deformation of the first crystal monochromator – and the potential loss of beam brightness – is often a concern. However, if downstream beam focusing is planned, the lensing effect of the monochromator must be considered even if thermal deformations are small. In this paper we report on recent experiments at an Advanced Photon Source (APS) beamline that focuses the X-ray beam using compound refractive lenses downstream of an X-ray monochromator system. Increasing the X-ray beam power by increasing the storage ring current from 100mA to 130mA resulted in an effective doubling of the focal distance. We show quantitatively that this is due to a lensing effect of the distorted monochromator that results in the creation of a virtual source downstream of the actual source. An analysis of the defocusing and options to mitigate this effect are explored.

Dynamics of iodine anions in KI and LiI aqueous solutions studied by 127I nuclear resonant quasi-elastic scattering

The dynamics of iodine ions in potassium iodide (KI) and lithium iodide (LiI) aqueous solutions have been studied through 127I nuclear resonant quasi-elastic scattering (NRQES). A newly developed Si (12 2 2) double crystal monochromator for 127I 57.6 keV excitation is used. Broadening due to a diffusive motion is measured in the energy spectra of the NRQES from the solutions.

Contrast formation by a laboratory microtomograph in the scheme with analyzer crystal in the asymmetric bragg geometry

A method of numerical simulation of X-ray optical systems is presented. This method has been used to analyze the operation of a unit of a laboratory microtomograph in which monochromator crystals in asymmetric Bragg geometry are applied as optical elements. Based on the analysis, it is concluded that this scheme provides in principle submicron resolution.

Influence of higher harmonics of the undulator in X-ray polarimetry and crystal monochromator design.

The spectrum of the undulator radiation of beamline P01 at Petra III has been measured after passing a multiple reflection channel-cut polarimeter. Odd and even harmonics up to the 15th order, as well as Compton peaks which were produced by the high harmonics in the spectrum, could been measured. These additional contributions can have a tremendous influence on the performance of the polarimeter and have to be taken into account for further polarimeter designs.