Synchrotron Beamlines Research Articles

Multi-pitch nano-accuracy surface profiler for strongly curved X-ray mirror metrology

We present our recent research and development effort on the Multi-Pitch Nano-accuracy Surface Profiler (MPNSP). This metrology instrument is developed to characterize strongly curved X-ray mirrors proposed to achieve diffraction-limited soft X-ray focusing for scientific applications at the synchrotron beamlines. The measurement process consists of forward-and-backward scans on the test mirror surface along its tangential direction at multiple pitch angles. Our research and development in this work aim to take the challenge of measuring strongly curved X-ray mirrors with a typical total slope range ≳10 mrad, while maintaining the Root Mean Square (RMS) value of measurement repeatability and self-consistency at 50 nrad RMS level. We first introduce the mechanical design, followed by a brief review of the mathematical model and the optimization algorithm for the MPNSP technique. By detecting the rotation axis of the mirror pitch with a machine vision approach, we can determine and then reduce the vertical distance between the pitch rotation axis and the test mirror surface to a sub-mm level. In addition, we describe a practical data acquisition procedure for strongly curved X-ray mirrors with a total slope range larger than the slope measuring range of the autocollimator used in the instrument. As a result, the proposed MPNSP measurements with different mirror orientations achieve remarkable self-consistency and reproducibility of <50 nrad RMS in slope and <0.5 nm RMS in height.

BEM-Based Magnetic Field Reconstruction by Ensemble Kálmán Filtering

Abstract Magnetic fields generated by normal or superconducting electromagnets are used to guide and focus particle beams in storage rings, synchrotron light sources, mass spectrometers, and beamlines for radiotherapy. The accurate determination of the magnetic field by measurement is critical for the prediction of the particle beam trajectory and hence the design of the accelerator complex. In this context, state-of-the-art numerical field computation makes use of boundary-element methods (BEM) to express the magnetic field. This enables the accurate computation of higher-order partial derivatives and local expansions of magnetic potentials used in efficient numerical codes for particle tracking. In this paper, we present an approach to infer the boundary data of an indirect BEM formulation from magnetic field measurements by ensemble Kálmán filtering. In this way, measurement uncertainties can be propagated to the boundary data, magnetic field and potentials, and to the beam related quantities derived from particle tracking. We provide results obtained from real measurement data of a curved dipole magnet using a Hall probe mapper system.

Bimorph mirrors at synchrotron beamlines: from walking to flying

With brighter synchrotron sources, automated sample changers, and faster detectors, there is a strong scientific need for rapid and precise variation of the X-ray beam profile, rather than the “set and forget” operation of years past. Piezoelectric bimorph deformable mirrors already allow quick beam profile changes without the heat generation and wear of mechanical devices. Now, their early technological limitations – excessively constraining holders, progressive “junction effect” distortion, and communication bottlenecks with power supplies – are being overcome by a collaboration of scientists and engineers both in industry and at Diamond Light Source. A new generation of bimorph mirrors maintains a stable figure over extended periods of operation. Improved holders and flexible electrical connectors are greatly reducing the mechanical strain imparted to bimorphs, thereby improving their speed, accuracy, and stability. A more sophisticated high voltage power supply has on-board signal processing capacity, allowing large focusing changes within seconds and providing programmable time-varying voltage profiles to counteract piezoelectric creep. The communication between beamline systems and power supplies is being freed of bottlenecks and now runs stably up to 1 Hz. Early tests have already shown that bimorph mirrors can repeatedly switch the size of an X-ray beam in well under 10 seconds. Bimorph mirrors at synchrotron beamlines are now growing beyond the largely static operation of the past and gaining a new dynamism through development projects that are now well advanced. We report on how these endeavours will make it easier for beamlines to utilise the full potential of bimorph mirrors.

Optimization of Solid Angle and Count Rate Capability of an X-ray Detector with Backscattering Geometry

We study here an optimized geometry for an X-ray detector with hole in the center, as key component for ASCANIO: an innovative 16-channels SDD based spectrometer specifically designed for X-ray fluorescence microscopy (XFM) imaging in synchrotron beamlines. The detector will feature a backscattering geometry with a tilted SDD layout achieving 1 sr solid angle at 8 mm sample distance and a potential Output Count Rate higher than 20 Mcps. The 1 mm thick SDD provides 65 % absorption efficiency at 20 keV while preserving a good energy resolution better than 150 eV thanks to a dedicated cooling system and a low noise front-end electronics. In this paper, the optimization of the detector geometry, in terms of solid angle vs sample distance and maximization of the Output Count Rate introducing a tilting of the SDD units, is discussed.

X-Ray Photoabsorption of Density-sensitive Metastable States in Ne vii, Fe xxii, and Fe xxiii

Metastable states of ions can be sufficiently populated in absorbing and emitting astrophysical media, enabling spectroscopic plasma-density diagnostics. Long-lived states appear in many isoelectronic sequences with an even number of electrons, and can be fed at large rates by various photonic and electronic mechanisms. Here, we experimentally investigate beryllium-like and carbon-like ions of neon and iron that have been predicted to exhibit detectable features in astrophysical soft X-ray absorption spectra. An ion population generated and excited by electron impact is subjected to highly monochromatic X-rays from a synchrotron beamline, allowing us to identify Kα transitions from metastable states. We compare their energies and natural line widths with state-of-the-art theory and benchmark level population calculations at electron densities of 1010.5 cm−3.

Advanced optical simulation tools in the OASYS suite and their applications to the design of last generation synchrotron radiation beamlines

Since 2013, OASYS (OrAnge SYnchrotron Suite) has been developed as a versatile, user-friendly and open-source graphical environment for modeling X-ray sources, optical systems, and experiments. Its concept stems from the need for modern software tools to satisfy the demand for performing more complex analyses and designing optical systems for 4th generation synchrotron radiation and FEL facilities. The ultimate purpose of OASYS is to integrate in a synergetic way the most powerful calculation engines available to perform virtual experiments in a synchrotron beamline. For X-ray Optics, OASYS integrates different simulation strategies by implementing adequate simulation tools, which communicate by sending and receiving encapsulated data. The OASYS suite has been extensively used in the optical design process for the upgrade projects of several synchrotron radiation facilities worldwide. Several new tools have been created to perform advanced calculations needed for the design of the beamlines and provide accurate specifications for the procurement of the optics.

Low line density blazed gratings with low blaze angles

Gratings installed in synchrotron beamlines and instruments have standard line densities ranging from ~300 L/mm up to 2400 L/mm with blaze angles from 0.3° to 2°. For FEL beamlines lower line densities and lower angles are required. To manufacture these in the required high quality poses some challenges with regard to the ruling process and the ion etching process. Our investigation and process results will be described here. Additionally, first results of the process on a grating substrate are demonstrated.

Simultaneous in-situ x-ray beam profile and intensity measurements with a minimally invasive pixelated diamond monitor

Measuring x-ray beam position, profile, and intensity at synchrotron beamlines provides valuable information for all experiments. Sydor’s transparent x-ray camera (TXC), based on technology originally developed at Brookhaven National Laboratory[1], enables these measurements in-line with experiments for live feedback. The TXC has a low beam profile that fits within a standard vacuum flange width and is composed of diamond material for > 90% transmission of > 5 keV x-rays, minimizing disruption of beamline space and the x-ray beam itself. Standard device parameters include 32 x 32, 60 µm pitch pixels, linearity over a 107 – 1016 photons/s dynamic imaging range, < 40 pA noise floor, and total flux measurement mode. Device performance has been evaluated using a pinhole mask with a benchtop silver x-ray tube and during beam focusing tests at the XFP beamline at NSLS-II and flux characterization at the FAST beamline at CHESS. This work will highlight the features of this commercial beam diagnostic, test results, and future directions and applications of the technology.

A tensile stage for high resolution synchrotron-based infrared microspectroscopy at MIRAS

For the study of thin films and fibres under load, a uniaxial tensile stage has been developed for synchrotron-based polarized Fourier-transform infrared (FTIR) microspectroscopy. One of the advantages compared to commercial available stages is its compact design at the sample position (<20 mm thickness) and the large field of view on the sample for transmission and reflection geometry. In addition, the stage is mounted on a base plate, which can be rotated between -15° and +193° in the sample plane, in order to rotate the sample relative to the inherent polarization of the incoming infrared light from the synchrotron light source. Preliminary in situ tensile load experiments conducted at MIRAS beamline of the ALBA synchrotron were done on 3D printed thermoplastic polyurethane (TPU) polymer thin films. The samples could be mapped in transmission geometry under tensile load achieving high spatial resolution up to 10 micros using the intense IR source of the synchrotron light. Making use of polarized synchrotron-based infrared light, it was possible to show the alignment of different vibrational bands parallel and orthogonal to the stretching direction. The v(C=O) absorbance bands decrease upon stretching using parallel polarized infrared light, while the v(C=C) bands are increasing in intensity, revealing the orientation of v(C=O) bonds orthogonal to the stretching direction during stretching. The experiments highlight the unique instrumentation capabilities of the tensile stage for in situ measurement of molecular distributions and chemical bond orientations as a function of sample displacement and applied load.

Recent developments at the COMET instrument of the SEXTANTS beamline at SOLEIL

The COMET experimental station at SEXTANTS beamline of the SOLEIL synchrotron is dedicated to the coherent imaging of magnetic domains, using holography and ptychography, in a sample environment including magnetic fields up to 0.9 T, temperature range from 30 to 400 K and RF pumping. The 2D-detector capabilities of COMET were recently upgraded by adding to the standard CCD camera two new detectors: a high repetition rate 2D CMOS and a double delay line MCP for time resolved experiments. The three detectors can be interchanged within minutes without breaking the vacuum. The distance between an individual detector and the sample can be varied over a wide range, allowing for a trade-off between pixel size and field of view in the image reconstruction. A reconstructed pixel size of the order of 10 nm has been achieved with the new COMET setup. We report also a comparison between holographic images of magnetic domains obtained for the same sample by using the CMOS and the CCD detectors

Synchrotron‐based FTIR microspectroscopy of human primary retinal pigmented epithelial cells as a model for age‐related macular degeneration

AbstractPurpose: To investigate the characteristics of untreated and treated human retinal pigmented epithelial cells (hRPEs) as an ex vivo model for age‐related macular degeneration (AMD) using high resolution synchrotron radiation‐based Fourier Transform Infrared (FTIR) microspectroscopy and multivariate analysis.Methods: hRPEs obtained from cadavers were treated by autophagy ‐inducer rapamycin (Rap), and ‐inhibitor bafilomycin A1 (Baf), as well as hydrogen peroxide (H2O2) to induce oxidative stress, in an ex vivo model for studying AMD. FTIR measurements were performed at the MIRAS beamline of the ALBA Synchrotron, Barcelona, Spain.Results: The FTIR spectra consisted of several bands arising from the vibration of different groups belonging to proteins, lipids and nucleic acids, indicating the rich biochemical composition of the hRPEs. In the protein region, the amide I band of the treated groups (Rap, Baf, H2O2) was different from the control untreated group, indicating an overall protein disordering under such treatments. In the DNA region, two spectral areas appeared to be modified upon treatment, indicating different modifications of the DNA conformational changes or rearrangements attributed to the distortions of the DNA double helix in the presence of Rap, Baf or H2O2. The same treatments could also induce several modifications in the lipid spectral region, which can affect a wide range of biological processes. The H2O2 treated group showed higher prevalence for the lipid peroxidation, a process generated by the effect of several reactive oxygen species.Conclusions: The present study shows that high resolution FTIR can be used to evaluate the complete bio−/macro‐molecular spectra of hRPEs such as proteins, lipids and nucleic acids, which can be used as an ex vivo model for AMD, thus giving possibilities for developing and testing new treatment modalities.

Detection limit of next-generation of multi-element germanium detectors in the context of Environmental science

One of the main challenges in Environmental sciences is the identification and chemical evolution of polluting traces (e.g, cadmium or antimony) in soil, which requires long acquistion times for accurate measurements at synchrotron facilities. In this context, the potential of a new generation multi-element germanium detectors to identify traces at 0.1-1 ppm in a reasonable time has been studied using Allpix Squared framework [1]. This code has been customized to include the three dimensional electric and weighting field maps generated by COMSOL Multiphysics software, and several features to model the sample environment at SOLEIL synchrotron and the signal response of a germanium detector equipped with a Digital Pulse Processor (DPP). The full simulation chain has been validated by experimental data from SAMBA beamline of SOLEIL synchrotron. This work presents a first estimation of the detection limit to cadmium traces in a soil sample for a future multi-element germanium detector, using this simulation chain.

Synchrotron radiation‐based infrared micro‐spectroscopy characterization of different types of epiretinal proliferations

AbstractPurpose: To assess epiretinal proliferations bio‐macromolecules and to provide their molecular fingerprint for better understanding of epiretinal proliferations, we used synchrotron radiation‐based Fourier transform infrared (SR‐FTIR) micro‐spectroscopy.Methods: The membranes were collected from routine pars plana vitrectomy. The biochemical differences between idiopathic nonvascular epiretinal membranes (ERMi), membranes in proliferative vitreoretinopathy (PVRm) and neovascular membranes in proliferative diabetic retinopathy (PDRm) were evaluated and compared by using SR‐FTIR micro‐spectroscopy at the MIRAS beamline of the ALBA Synchrotron, Barcelona, Spain and multivariate analysis.Results: PVRm differs the most from ERMi and PDRm in all spectral regions. We demonstrated the presence of silicone oil (SO) or polydimethylsiloxane (PDMS) in the structure of PVRm membrane after SO endotamponade suggesting that SO, in addition to many benefits as an important tool in vitreoretinal surgery, can also contribute in PVRm formation. We also showed the differences between PVRm, PDRm and ERMi in protein and lipid structure, collagen content and maturity.Conclusions: Our results obtained by SR‐FTIR increase the knowledge about the total proteins, lipids and nucleic acids in different epiretinal proliferations while offering also the evidence that SR‐FTIR is sensitive to the pathologic processes of epiretinal proliferations. We emphasize the different macro‐molecular composition of three different types of epiretinal proliferation stemming from different components and metabolic processes taking place as well as the caution needed when using SO in vitreoretinal surgery.

Beamline-implemented stretching devices for in situ X-ray scattering experiments

Two recently developed experimental devices for investigating soft matter deformation are presented. Both devices exploit the capabilities of a modern synchrotron beamline to enable advanced and highly precise materials-science experiments in which X-ray scattering is registered. The devices can be operated both in monotonic as well as cyclic mode and are implemented into a beamline at DESY, Hamburg (Germany). Hence, relevant experimental parameters, such as displacement, force and temperature, are recorded synchronously with the individual X-ray scattering patterns. In addition, spatial variation of materials deformation can be monitored and recorded with optical microscopy. This unique sample environment enables in situ X-ray experiments in transmission, i.e. small- or wide-angle X-ray scattering (SAXS or WAXS), and in grazing-incidence geometry, i.e. grazing-incidence (GI-) SAXS or WAXS. One device with stepper motors is designed for studies of slow, (quasi-) static deformation and the other one with pneumatic actuators can be used for fast, impact deformation. Both devices are available to external beamline users, too.

An analytical approach to designing a future Nano-ARPES beamline for Diamond-II

Angle-resolved photoemission spectroscopy (ARPES) is a powerful method for measuring the electronic band structure of solids. Diamond Light Source is planning to build a multibend-achromat (MBA) synchrotron – Diamond-II - which will provide an almost diffraction-limited photon source in the vacuum-ultraviolet photon energy range. The improved emittance and higher coherence of MBA synchrotrons means that samples with features smaller than 1 µm can be readily studied using ARPES, provided the beamline is designed to take full advantage of the new photon source. We have developed an analytical method for optimising the optical design of a future Nano-ARPES beamline for Diamond-II. Our method enables one to explore large regions of parameter space for a beamline design in an unbiased and systematic way, with minimal requirements on computing power. We believe that the analytical method presented here will be a useful tool for synchrotron beamline designers, as it allows many beamline characteristics to be simulated quickly while working within any practical limitations.

Development of monochromators for HEPS

Monochromator plays a key role in the performance of a synchrotron beamline, it determines a beamline’s energy range, bandwidth, flux, focal sizes, coherence, etc., and it has been the limiting optic in a beamline for a long time. Many efforts have been made in order to improve the performance of the monochromators around the world. The HEPS project will need a batch of monochromators and some of them are built in house, many technical problems needed to be solved. A double crystal monochromator prototype has been developed, tested, then modified by improving the mechanical stability, switching to mechanism based on flexures to drive the second crystal. A quick EXAFS Channel-Cut crystal monochromator was designed for the HEPS XAFS beamline, driven by torque motor and closed loop controller. The design aspects and some test results of both monochromators will be introduced. Results show that the design is feasible and meet the requirements of both beamlines.

Measurement and Calculation of X-Ray Production Efficiencies for Copper, Zirconium, and Tungsten.

Electron probe microanalysis (EPMA) is based on physical relations between measured X-ray intensities of characteristic lines and their X-ray production efficiency, which depends on the specimen composition. The quality of the analysis results relies on how realistically the physical relations describe the generation and emission of X-rays. Special experiments are necessary to measure X-ray production efficiencies. A challenge in these experiments is the determination of the detection efficiency of the spectrometer as a function of the photon energy. An energy-dispersive spectrometer was used in this work, for which the efficiency was determined at metrological synchrotron beamlines with an accuracy of ±2%. X-ray production efficiencies for the L series and the Kα series of copper and zirconium and for the M and L series of tungsten were determined at energies up to 30 keV in a scanning electron microscope. These experimental values were compared with calculated X-ray production efficiencies using physical relations and material constants applied in EPMA. The objective of the comparison is the further improvement of EPMA algorithms as well as extending the available database for X-ray production efficiencies. Experimental data for the X-ray production efficiency are also useful for the assessment of spectrum simulation software.

Primary calibration of photodiodes with monochromatic X‐ray beams using an electrical‐substitution radiometer

AbstractThe electrical‐substitution cryogenic detector BOLometer for Use in the range of X‐rays (BOLUX), which was developed some years ago at CEA/DAM, has been set up and restarted now at LNHB. It has been used for the primary measurement of the intensity (total energy per unit time) of monochromatic synchrotron beams in the energy range from 3 to 30 keV. These well‐determined photon beams have been employed for the efficiency calibration of two photodiodes in terms of current induced per unit optical power at different photon energies. In a final step, we explored the possibility to use these primary‐calibrated photodiodes to determine the efficiency curve of an energy‐dispersive spectrometer based on a semiconductor detector (Silicon Drift Detector) using less intense monochromatic photon fluxes. The characteristics of the radiometer BOLUX and its principle of operation are described, and the measurements carried out at the synchrotron beamline are presented, including the determination of the beams' intensities, the direct calibration of photodiodes with respect to BOLUX and the use of one of those photodiodes as a standard transfer for the calibration of the SDD.

Single Shot Lensless Interferenceless Phase Imaging of Biochemical Samples Using Synchrotron near Infrared Beam

Phase imaging of biochemical samples has been demonstrated for the first time at the Infrared Microspectroscopy (IRM) beamline of the Australian Synchrotron using the usually discarded near-IR (NIR) region of the synchrotron-IR beam. The synchrotron-IR beam at the Australian Synchrotron IRM beamline has a unique fork shaped intensity distribution as a result of the gold coated extraction mirror shape, which includes a central slit for rejection of the intense X-ray beam. The resulting beam configuration makes any imaging task challenging. For intensity imaging, the fork shaped beam is usually tightly focused to a point on the sample plane followed by a pixel-by-pixel scanning approach to record the image. In this study, a pinhole was aligned with one of the lobes of the fork shaped beam and the Airy diffraction pattern was used to illuminate biochemical samples. The diffracted light from the samples was captured using a NIR sensitive lensless camera. A rapid phase-retrieval algorithm was applied to the recorded intensity distributions to reconstruct the phase information. The preliminary results are promising to develop multimodal imaging capabilities at the IRM beamline of the Australian Synchrotron.

Inline small-angle X-ray scattering-coupled chromatography under extreme hydrostatic pressure.

As continuing discoveries highlight the surprising abundance and resilience of deep ocean and subsurface microbial life, the effects of extreme hydrostatic pressure on biological structure and function have attracted renewed interest. Biological small-angle X-ray scattering (BioSAXS) is a widely used method of obtaining structural information from biomolecules in solution under a wide range of solution conditions. Due to its ability to reduce radiation damage, remove aggregates, and separate monodisperse components from complex mixtures, size-exclusion chromatography-coupled SAXS (SEC-SAXS) is now the dominant form of BioSAXS at many synchrotron beamlines. While BioSAXS can currently be performed with some difficulty under pressure with non-flowing samples, it has not been clear how, or even if, continuously flowing SEC-SAXS, with its fragile media-packed columns, might work in an extreme high-pressure environment. Here we show, for the first time, that reproducible chromatographic separations coupled directly to high-pressure BioSAXS can be achieved at pressures up to at least 100 MPa and that pressure-induced changes in folding and oligomeric state and other properties can be observed. The apparatus described here functions at a range of temperatures (0°C-50°C), expanding opportunities for understanding biomolecular rules of life in deep ocean and subsurface environments.