Design of an ultrahigh‐energy‐resolution and wide‐energy‐range soft X‐ray beamline

A new ultrahigh‐energy‐resolution and wide‐energy‐range soft X‐ray beamline has been designed and is under construction at the Shanghai Synchrotron Radiation Facility. The beamline has two branches: one dedicated to angle‐resolved photoemission spectroscopy (ARPES) and the other to photoelectron emission microscopy (PEEM). The two branches share the same plane‐grating monochromator, which is equipped with four variable‐line‐spacing gratings and covers the 20–2000 eV energy range. Two elliptically polarized undulators are employed to provide photons with variable polarization, linear in every inclination and circular. The expected energy resolution is approximately 10 meV at 1000 eV with a flux of more than 3 × 10¹⁰ photons s^?1 at the ARPES sample positions. The refocusing of both branches is based on Kirkpatrick–Baez pairs. The expected spot sizes when using a 10 µm exit slit are 15 µm × 5 µm (horizontal × vertical FWHM) at the ARPES station and 10 µm × 5 µm (horizontal × vertical FWHM) at the PEEM station. The use of plane optical elements upstream of the exit slit, a variable‐line‐spacing grating and a pre‐mirror in the monochromator that allows the influence of the thermal deformation to be eliminated are essential for achieving the ultrahigh‐energy resolution.     

Focusing,collimation and flux throughput at the IMCA‐CAT bending‐magnet beamline at the Advanced Photon Source

The IMCA‐CAT bending‐magnet beamline was upgraded with a collimating mirror in order to achieve the energy resolution required to conduct high‐quality multi‐ and single‐wavelength anomalous diffraction (MAD/SAD) experiments without sacrificing beamline flux throughput. Following the upgrade, the bending‐magnet beamline achieves a flux of 8 × 10¹¹ photons s^?1 at 1 Å wavelength, at a beamline aperture of 1.5 mrad (horizontal) × 86 µrad (vertical), with energy resolution (limited mostly by the intrinsic resolution of the monochromator optics) δE/E = 1.5 × 10^?4 (at 10 kV). The beamline operates in a dynamic range of 7.5–17.5 keV and delivers to the sample focused beam of size (FWHM) 240 µm (horizontally) × 160 µm (vertically). The performance of the 17‐BM beamline optics and its deviation from ideally shaped optics is evaluated in the context of the requirements imposed by the needs of protein crystallography experiments. An assessment of flux losses is given in relation to the (geometric) properties of major beamline components.     

A new small‐angle X‐ray scattering set‐up on the crystallography beamline I711 at MAX‐lab

A small‐angle X‐ray scattering (SAXS) set‐up has recently been developed at beamline I711 at the MAX II storage ring in Lund (Sweden). An overview of the required modifications is presented here together with a number of application examples. The accessible q range in a SAXS experiment is 0.009–0.3 Å^?1 for the standard set‐up but depends on the sample‐to‐detector distance, detector offset, beamstop size and wavelength. The SAXS camera has been designed to have a low background and has three collinear slit sets for collimating the incident beam. The standard beam size is about 0.37 mm × 0.37 mm (full width at half‐maximum) at the sample position, with a flux of 4 × 10¹⁰ photons s^?1 and λ = 1.1 Å. The vacuum is of the order of 0.05 mbar in the unbroken beam path from the first slits until the exit window in front of the detector. A large sample chamber with a number of lead‐throughs allows different sample environments to be mounted. This station is used for measurements on weakly scattering proteins in solutions and also for colloids, polymers and other nanoscale structures. A special application supported by the beamline is the effort to establish a micro‐fluidic sample environment for structural analysis of samples that are only available in limited quantities. Overall, this work demonstrates how a cost‐effective SAXS station can be constructed on a multipurpose beamline.     

X‐Treme beamline at SLS: X‐ray magnetic circular and linear dichroism at high field and low temperature

X‐Treme is a soft X‐ray beamline recently built in the Swiss Light Source at the Paul Scherrer Institut in collaboration with École Polytechnique Fédérale de Lausanne. The beamline is dedicated to polarization‐dependent X‐ray absorption spectroscopy at high magnetic fields and low temperature. The source is an elliptically polarizing undulator. The end‐station has a superconducting 7 T–2 T vector magnet, with sample temperature down to 2 K and is equipped with an in situ sample preparation system for surface science. The beamline commissioning measurements, which show a resolving power of 8000 and a maximum flux at the sample of 4.7 × 10¹² photons s^?1, are presented. Scientific examples showing X‐ray magnetic circular and X‐ray magnetic linear dichroism measurements are also presented.     

SUT‐NANOTEC‐SLRI beamline for X‐ray absorption spectroscopy

The SUT‐NANOTEC‐SLRI beamline was constructed in 2012 as the flagship of the SUT‐NANOTEC‐SLRI Joint Research Facility for Synchrotron Utilization, co‐established by Suranaree University of Technology (SUT), National Nanotechnology Center (NANOTEC) and Synchrotron Light Research Institute (SLRI). It is an intermediate‐energy X‐ray absorption spectroscopy (XAS) beamline at SLRI. The beamline delivers an unfocused monochromatic X‐ray beam of tunable photon energy (1.25–10 keV). The maximum normal incident beam size is 13 mm (width) × 1 mm (height) with a photon flux of 3 × 10⁸ to 2 × 10¹⁰ photons s^?1 (100 mA)^?1 varying across photon energies. Details of the beamline and XAS instrumentation are described. To demonstrate the beamline performance, K‐edge XANES spectra of MgO, Al₂O₃, S₈, FeS, FeSO₄, Cu, Cu₂O and CuO, and EXAFS spectra of Cu and CuO are presented.     

High‐flux hard X‐ray microbeam using a single‐bounce capillary with doubly focused undulator beam

A pre‐focused X‐ray beam at 12 keV and 9 keV has been used to illuminate a single‐bounce capillary in order to generate a high‐flux X‐ray microbeam. The BioCAT undulator X‐ray beamline 18ID at the Advanced Photon Source was used to generate the pre‐focused beam containing 1.2 × 10¹³ photons s^?1 using a sagittal‐focusing double‐crystal monochromator and a bimorph mirror. The capillary entrance was aligned with the focal point of the pre‐focused beam in order to accept the full flux of the undulator beam. Two alignment configurations were tested: (i) where the center of the capillary was aligned with the pre‐focused beam (`in‐line') and (ii) where one side of the capillary was aligned with the beam (`off‐line'). The latter arrangement delivered more flux (3.3 × 10¹² photons s^?1) and smaller spot sizes (≤10 µm FWHM in both directions) for a photon flux density of 4.2 × 10¹⁰ photons s^?1µm^?2. The combination of the beamline main optics with a large‐working‐distance (approximately 24 mm) capillary used in this experiment makes it suitable for many microprobe fluorescence applications that require a micrometer‐size X‐ray beam and high flux density. These features are advantageous for biological samples, where typical metal concentrations are in the range of a few ng cm^?2. Micro‐XANES experiments are also feasible using this combined optical arrangement.     

DISCO synchrotron‐radiation circular‐dichroism endstation at SOLEIL

The new synchrotron‐radiation circular‐dichroism (SRCD) endstation on the UV‐visible synchrotron beamline DISCO has been commissioned at the SOLEIL synchrotron. The design has been focused on preservation of a high degree of linear polarization at high flux and moderate resolving power covering the vacuum ultraviolet to visible spectral range (125–600 nm). The beam dimensions have been set to 4 mm × 4 mm at 1 nm bandwidth for lower sample degradation. The nitrogen‐purged sample chamber fits three types of sample holders accommodating conventional round cell mounting, automated rotation of the samples, as well as a microfluidic set‐up. Automated temperature‐controlled data collection on microvolumes is now available to the biology and chemistry communities. Macromolecules including membrane proteins, soluble proteins, bio‐nanotubes, sugars, DNA and RNAs are now routinely investigated.     

The first microbeam synchrotron X‐ray fluorescence beamline at the Siam Photon Laboratory

The first microbeam synchrotron X‐ray fluorescence (µ‐SXRF) beamline using continuous synchrotron radiation from Siam Photon Source has been constructed and commissioned as of August 2011. Utilizing an X‐ray capillary half‐lens allows synchrotron radiation from a 1.4 T bending magnet of the 1.2 GeV electron storage ring to be focused from a few millimeters‐sized beam to a micrometer‐sized beam. This beamline was originally designed for deep X‐ray lithography (DXL) and was one of the first two operational beamlines at this facility. A modification has been carried out to the beamline in order to additionally enable µ‐SXRF and synchrotron X‐ray powder diffraction (SXPD). Modifications included the installation of a new chamber housing a Si(111) crystal to extract 8 keV synchrotron radiation from the white X‐ray beam (for SXPD), a fixed aperture and three gate valves. Two end‐stations incorporating optics and detectors for µ‐SXRF and SXPD have then been installed immediately upstream of the DXL station, with the three techniques sharing available beam time. The µ‐SXRF station utilizes a polycapillary half‐lens for X‐ray focusing. This optic focuses X‐ray white beam from 5 mm × 2 mm (H × V) at the entrance of the lens down to a diameter of 100 µm FWHM measured at a sample position 22 mm (lens focal point) downstream of the lens exit. The end‐station also incorporates an XYZ motorized sample holder with 25 mm travel per axis, a 5× ZEISS microscope objective with 5 mm × 5 mm field of view coupled to a CCD camera looking to the sample, and an AMPTEK single‐element Si (PIN) solid‐state detector for fluorescence detection. A graphic user interface data acquisition program using the LabVIEW platform has also been developed in‐house to generate a series of single‐column data which are compatible with available XRF data‐processing software. Finally, to test the performance of the µ‐SXRF beamline, an elemental surface profile has been obtained for a piece of ancient pottery from the Ban Chiang archaeological site, a UNESCO heritage site. It was found that the newly constructed µ‐SXRF technique was able to clearly distinguish the distribution of different elements on the specimen.     

X‐ray powder diffraction at the XRD1 beamline at LNLS

Various upgrades have been completed at the XRD1 beamline at the Brazilian synchrotron light source (LNLS). The upgrades are comprehensive, with changes to both hardware and software, now allowing users of the beamline to conduct X‐ray powder diffraction experiments with faster data acquisition times and improved quality. The main beamline parameters and the results obtained for different standards are presented, showing the beamline ability of performing high‐quality experiments in transmission geometry. XRD1 operates in the 5.5–14 keV range and has a photon flux of 7.8 × 10⁹ photons s^?1 (with 100 mA) at 12 keV, which is one of the typical working energies. At 8 keV (the other typical working energy) the photon flux at the sample position is 3.4 × 10¹⁰ photons s^?1 and the energy resolution ΔE/E = 3 × 10^?4.     

Toxic effects of copper (II) ions on bovine hemoglobin

In this paper, the toxic influence of copper ions (II) on bovine hemoglobin was investigated by the combination of ultraviolet-visible absorption, fluorescence, time-resolved fluorescence, synchronous fluorescence, and circular dichroism spectra. Driven by hydrophobic and electrostatic forces, copper ions (II) could interact with bovine hemoglobin to form bovine hemoglobin-copper ions (II) complex with one binding site. The binding constant (K) was 1.57?×?10⁴, 1.89?×?10⁴ and 2.11?×?10⁴?L/mol at 298, 304, and 310?K, respectively. The binding distance (r) was 4.24?nm. Fluorescence and time-resolved fluorescence spectra showed that bovine hemoglobin quenched by copper ions (II) was a static quenching process. Results of synchronous fluorescence spectra revealed that the microenvironment and the conformation of bovine hemoglobin were changed during the binding reaction. Data of circular dichroism spectra suggested that with the increasing concentration of copper ions (II), the secondary structure of bovine hemoglobin underwent a decrease in α-helix and alteration in backbone microenvironment. Copper ions (II) was thus evidenced to have a certain toxic effect on physical bodies.     

A dedicated small‐angle X‐ray scattering beamline with a superconducting wiggler source at the NSRRC

At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5 GeV storage ring, a dedicated small‐angle X‐ray scattering (SAXS) beamline has been installed with an in‐achromat superconducting wiggler insertion device of peak magnetic field 3.1 T. The vertical beam divergence from the X‐ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (ΔE/E? 2 × 10^?4) in the energy range 5–23 keV, or by a double Mo/B₄C multilayer monochromator for 10–30 times higher flux (～10¹¹ photons s^?1) in the 6–15 keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of ～0.9 mm × 0.3 mm (horizontal × vertical) at the focus point located 26.5 m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing‐incidence SAXS (GISAXS) from liquid surfaces. Two online beam‐position monitors separated by 8 m provide an efficient feedback control for an overall beam‐position stability in the 10 µm range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray‐tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core‐shell quantum dots) and GISAXS from liquid surfaces.     

Fast‐scanning high‐flux microprobe for biological X‐ray fluorescence microscopy and microXAS

There is a growing interest in the biomedical community in obtaining information concerning the distribution and local chemical environment of metals in tissues and cells. Recently, biological X‐ray fluorescence microscopy (XFM) has emerged as the tool of choice to address these questions. A fast‐scanning high‐flux X‐ray microprobe, built around a recently commissioned pair of 200 mm‐long Rh‐coated silicon Kirkpatrick–Baez mirrors, has been constructed at BioCAT beamline 18ID at the Advanced Photon Source. The new optical system delivers a flux of 1.3 × 10¹² photons s^?1 into a minimum focal spot size of ～3–5 µm FWHM. A set of Si drift detectors and bent Laue crystal analyzers may be used in combination with standard ionization chambers for X‐ray fluorescence measurements. BioCAT's scanning software allows fast continuous scans to be performed while acquiring and storing full multichannel analyzer spectra per pixel on‐the‐fly with minimal overhead time (<20 ms per pixel). Together, the high‐flux X‐ray microbeam and the rapid‐scanning capabilities of the BioCAT beamline allow the collection of XFM and micro X‐ray absorption spectroscopy (microXAS) measurements from as many as 48 tissue sections per day. This paper reports the commissioning results of the new instrument with representative XFM and microXAS results from tissue samples.     

DESIRS: a state‐of‐the‐art VUV beamline featuring high resolution and variable polarization for spectroscopy and dichroism at SOLEIL

DESIRS is a new undulator‐based VUV beamline on the 2.75 GeV storage ring SOLEIL (France) optimized for gas‐phase studies of molecular and electronic structures, reactivity and polarization‐dependent photodynamics on model or actual systems encountered in the universe, atmosphere and biosphere. It is equipped with two dedicated endstations: a VUV Fourier‐transform spectrometer (FTS) for ultra‐high‐resolution absorption spectroscopy (resolving power up to 10⁶) and an electron/ion imaging coincidence spectrometer. The photon characteristics necessary to fulfill its scientific mission are: high flux in the 5–40 eV range, high spectral purity, high resolution, and variable and well calibrated polarizations. The photon source is a 10 m‐long pure electromagnetic variable‐polarization undulator producing light from the very near UV up to 40 eV on the fundamental emission with tailored elliptical polarization allowing fully calibrated quasi‐perfect horizontal, vertical and circular polarizations, as measured with an in situ VUV polarimeter with absolute polarization rates close to unity, to be obtained at the sample location. The optical design includes a beam waist allowing the implementation of a gas filter to suppress the undulator high harmonics. This harmonic‐free radiation can be steered toward the FTS for absorption experiments, or go through a highly efficient pre‐focusing optical system, based on a toroidal mirror and a reflective corrector plate similar to a Schmidt plate. The synchrotron radiation then enters a 6.65 m Eagle off‐plane normal‐incidence monochromator equipped with four gratings with different groove densities, from 200 to 4300 lines mm^?1, allowing the flux‐to‐resolution trade‐off to be smoothly adjusted. The measured ultimate instrumental resolving powers are 124000 (174 µeV) around 21 eV and 250000 (54 µeV) around 13 eV, while the typical measured flux is in the 10¹⁰–10¹¹ photons s^?1 range in a 1/50000 bandwidth, and 10¹²–10¹³ photons s^?1 in a 1/1000 bandwidth, which is very satisfactory although slightly below optical simulations. All of these features make DESIRS a state‐of‐the‐art VUV beamline for spectroscopy and dichroism open to a broad scientific community.     

A miniature X‐ray tube approach to measuring lead in bone using L‐XRF

Using a miniature X‐ray tube and silicon PiN diode detector, an approach to measuring lead (Pb) in bone phantoms was tested. The X‐ray tube was used to excite L‐line X‐ray fluorescence (L‐XRF) of lead in bone phantoms. The bone phantoms were made from plaster of Paris and dosed with varying quantities of lead. Phantoms were made in two sets with different shapes to model different bone surfaces. One set of bone phantoms was circular in cross‐section (2.5‐cm diameter), the other square in cross‐section (2.2 cm × 2.2 cm). Using an irradiation time of 180 s (real time), five trials were run for each bone phantom. Analysis was performed for both Lα and Lβ lead X‐rays. Based on these calibration trials, (3σ₀/slope) minimum detection limits of 7.4 ± 0.3 µg Pb g^?1 (circular cross‐section) and 8.6 ± 0.6 µg Pb g^?1 (square cross‐section) were determined for the bare bone phantoms. To simulate a more realistic in vivo scenario with soft tissue overlying bone, further trials were performed with a resin material placed between the experimental system and the bone phantom. For the square cross‐section bone phantoms, a layer of resin with a thickness of 1.2 mm was used, and a minimum detection limit of 17 ± 3 µg Pb g^?1 determined. For the circular cross‐section phantoms, a layer of resin with an average thickness of 2.7 mm was used. From these, a more realistic minimum detection limit for in vivo applications (43 ± 7 µg Pb g^?1) was determined. Copyright © 2011 John Wiley & Sons, Ltd.     

硬X射线磁圆二色实验方法的建立

在北京同步辐射装置(BSRF)1W1B光束线和XAFS实验站上国内首次建立了硬X射线波段的磁圆二色实验(XMCD)方法. 以单晶金刚石作为相位延迟片, 在透射劳埃(Laue)模式下, 利用衍射双折射效应, 将入射的单色线偏振光转变为相应的左旋和右旋圆偏振光, 测量磁化样品对左旋和右旋圆偏振光吸收的差异, 获得了XMCD信号. 本实验使用透射方法测量了Pt-Fe合金Pt L_2,3边的XMCD, 获得了XMCD信号. XMCD实验方法的建立, 为研究磁性材料尤其是磁性薄膜材料的电子结构和磁结构提供了实验基础.     

Silicon negative ion implantation induced vacancy defects in thermally grown SiO2 thin films

ABSTRACT

Thermally grown SiO₂ thin films on a silicon substrate implanted with 100?keV silicon negative ions with fluences varying from 1?×?10¹⁵ to 2?×?10¹⁷ ions cm^?2 have been investigated using Electron spin resonance, Fourier transforms infrared and Photoluminescence techniques. ESR studies revealed the presence of non-bridging oxygen hole centers, E′-centers and P_b-centers at g-values 2.0087, 2.0052 and 2.0010, respectively. These vacancy defects were found to increase with respect to ion fluence. FTIR spectra showed rocking vibration mode, stretching mode, bending vibration mode, and asymmetrical stretching absorption bands at 460, 614, 800 and 1080?cm^?1, respectively. The concentrations of Si–O and Si–Si bonds estimated from the absorption spectra were found to vary between 11.95?×?10²¹ cm^?3 and 5.20?×?10²¹ cm^?3 and between 5.90?×?10²¹ cm^?3 and 3.90?×?10²¹ cm^?3, respectively with an increase in the ion fluence. PL studies revealed the presence of vacancies related to non-bridging oxygen hole centers, which caused the light emission at a wavelength of 720?nm.     

Determination of Protoporphyrin IX Disodium Salt Based on Fluorescence Quenching of Glutathione-Capped Cadmium/Tellurium Quantum Dots

ABSTRACT

Aqueous glutathione-capped cadmium/tellurium quantum dots with a diameter of about 3 nm were synthesized. The fluorescence was quenched in the presence of protoporphyrin IX disodium salt, with the excitation wavelength at 320 nm. Under the optimal conditions, the quenched fluorescence intensity was linear in the range of 0.096–16 µg · mL^?1 with a concentration of protoporphyrin IX disodium salt, and the detection limit (3σ) was 2.8 × 10^?2 µg · mL^?1. The proposed method has been applied to the determination of protoporphyrin in serum samples with satisfactory results. The interaction mechanism was investigated.     

The vacuum ultraviolet beamline/endstations at NSRL dedicated to combustion research

An undulator‐based vacuum ultraviolet (VUV) beamline (BL03U), intended for combustion chemistry studies, has been constructed at the National Synchrotron Radiation Laboratory (NSRL) in Hefei, China. The beamline is connected to the newly upgraded Hefei Light Source (HLS II), and could deliver photons in the 5–21 eV range, with a photon flux of 10¹³ photons s^?1 at 10 eV when the beam current is 300 mA. The monochromator of the beamline is equipped with two gratings (200 lines mm^?1 and 400 lines mm^?1) and its resolving power is 3900 at 7.3 eV for the 200 lines mm^?1 grating and 4200 at 14.6 eV for the 400 lines mm^?1 grating. The beamline serves three endstations which are designed for respective studies of premixed flame, fuel pyrolysis in flow reactor, and oxidation in jet‐stirred reactor. Each endstation contains a reactor chamber, an ionization chamber where the molecular beam intersects with the VUV light, and a home‐made reflectron time‐of‐flight mass spectrometer. The performance of the beamline and endstations with some preliminary results is presented here. The ability to detect reactive intermediates (e.g. H, O, OH and hydroperoxides) is advantageous in combustion chemistry research.     

Fast X‐ray microfluorescence imaging with submicrometer‐resolution integrating a Maia detector at beamline P06 at PETRA III

The high brilliance of third‐generation synchrotron sources increases the demand for faster detectors to utilize the available flux. The Maia detector is an advanced imaging scheme for energy‐dispersive detection realising dwell times per image‐pixel as low as 50 µs and count rates higher than 10 × 10⁶ s^?1. In this article the integration of such a Maia detector in the Microprobe setup of beamline P06 at the storage ring PETRA III at the Deutsches Elektronen‐Synchrotron (DESY) in Hamburg, Germany, is described. The analytical performance of the complete system in terms of rate‐dependent energy resolution, scanning‐speed‐dependent spatial resolution and lower limits of detection is characterized. The potential of the Maia‐based setup is demonstrated by key applications from materials science and chemistry, as well as environmental science with geological applications and biological questions that have been investigated at the P06 beamline.