Double Crystal Monochromator Research Articles

X-ray imaging of a small electron beam in a low-emittance synchrotron light source

We have developed the X-ray beam imager (XBI) at the SPring-8 storage ring to observe transverse profiles of a small electron beam in a low-emittance synchrotron light source. The XBI is based on a single Fresnel zone plate (FZP) and an X-ray zooming tube (XZT). The X-ray image of the electron beam moving in a bending magnet is obtained by the FZP, and it is enlarged by the XZT. Monochromatic X-rays are selected by a double crystal monochromator to avoid the effect of chromatic aberration of the FZP. The XBI has achieved a 1 σ spatial resolution of approximately 4 μm, and a time resolution of 1 ms. Its field of view, which is free from vignetting, is larger than 1.5 mm in diameter on the coordinates of the electron beam. With the XBI, we have successfully measured the profiles of the electron beam of the SPring-8 and have found a vertical emittance lower than 10 pm rad at 10 mA circulating current. By utilizing the fast time resolution, we were able to study the transient behaviors of the effective beam profiles after beam injections in top-up operation at the SPring-8. In order to demonstrate the full two-dimensional imaging capability of the XBI, we also observed the dependence of the electron beam profile on the horizontal and the vertical betatron tunes.

Design of beamline BL15 at the Saga Light Source

The Saga Light Source (SAGA-LS) is the world’s first synchrotron light facility constructed by a local government, and has been under construction since 2001. Four newly designed beamlines will be finished and available for use in one year’s time. Among them, beamline BL15 is intended for structural studies of materials developed mainly for industrial purposes.We present the preliminary design of structural study beamline. White X-rays are generated by a bending magnet and then monochromatized and focused by a double-crystal monochromator and a rhodium-coated bent-cylindrical mirror. The FWHM beam size at the focal point is sub-millimeter. The photon flux and energy resolution are expected to be better than 1×1010photons/s and 8×10−4, respectively, in the energy range between 2.2 and 10keV. X-rays are supplied for several measurement systems in the experimental station.

A high-throughput structural biology/proteomics beamline at the SRS on a new multipole wiggler

The North West Structural Genomics Centre's beamline, MAD10, at the SRS receives the central part of the radiation fan (0.5 mrad vertically, 4 mrad horizontally) produced by a new 2.46 T ten-pole wiggler. The optical arrangement of the beamline consists of a Rh-coated collimating Si mirror, a fixed-exit-beam double-crystal monochromator with sagittal bending for horizontal focusing and a second Rh-coated Si mirror for vertical focusing. The double-crystal Si (111) monochromator allows data collection in the 5-13.5 keV photon energy range with rapid (subsecond) tunability and high energy resolution. The monochromatic beam is optimized through a 200 microm collimator. The beamline end station has been designed around a Mar desktop beamline with high-throughput cryogenic sample changer, Mar225 CCD detector, liquid-N(2) autofill system and an ORTEC C-TRAIN-04 energy-resolving high-count-rate X-ray fluorescence detector. The instrument is optimized for MAD/SAD applications in protein crystallography with the additional mode of operation of online single-crystal EXAFS studies on the same crystals. Thus, screening of metals/Se in the crystal can be performed quickly prior to MAD/SAD data collection by exciting the crystal with X-rays of appropriate energy and recording an energy-dispersive fluorescence spectrum. In addition, this experimental set-up allows for parallel XAFS measurements on the same crystal to monitor 'radiation-induced' changes, if any, in e.g. the redox state of metal centres to be detected for a 'metallic' functional group during crystallographic data collection. Moreover, careful minimization of the thickness of the Be window maximizes the intensity performance for the 2.0-2.5 A softer wavelength range. This range also covers the K-edges of a number of important 3d transition metals as well as the L-edges of xenon and iodine and enhanced sulfur f ''.

Measurement of the parallelism error of a double crystal monochromator by the pencil beam interferometer

For the precise measurement of the parallelism error between the two crystals in a double crystal monochromator, we suggest a new method that utilizes the pencil beam interferometer. The wave front-splitting pencil beam interferometer was modified, and applied to the measurement. The method overcomes the limitations of the precedent methods that using an autocollimator. Moreover, we can measure the parallelism error continuously through the full scan range with a simple setup. Especially, it should be noted that the angular sensitivity of this method is about 0.07arcsec rms.

Beamline Performance Simulations for the Fundamental Neutron Physics Beamline at the Spallation Neutron Source.

Monte Carlo simulations are being performed to design and characterize the neutron optics components for the two fundamental neutron physics beamlines at the Spallation Neutron Source. Optimization of the cold beamline includes characterization of the guides and benders, the neutron transmission through the 0.89 nm monochromator, and the expected performance of the four time-of-flight choppers. The locations and opening angles of the choppers have been studied using a simple spreadsheet-based analysis that was developed for other SNS chopper instruments. The spreadsheet parameters are then optimized using Monte Carlo techniques to obtain the results presented in this paper. Optimization of the 0.89 nm beamline includes characterizing the double crystal monochromator and the downstream guides. The simulations continue to be refined as components are ordered and their exact size and performance specifications are determined.

A fine adjustment mechanism of the second crystal in a double-crystal monochromator with a 3-PS parallel manipulator

A novel fine adjustment mechanism of the second crystal in a double-crystal monochromator is put forward, which is based on a 3-PS parallel manipulator and the magnetic force. Not only is the principle of fine adjusting the pitch angle and the roll angle analyzed, but also optimization of the structure parameters of the permanent magnet, a key part of the fine adjustment mechanism. The fine adjustment mechanism with the 3-PS parallel manipulator has been applied successfully in the double-crystal monochromator of 4W1B beam line in the Beijing Synchrotron Radiation Facility (BSRF).

A Five-coordinate Metal Center in Co(II)-substituted VanX

In an effort to structurally probe the metal binding site in VanX, electronic absorption, EPR, and extended x-ray absorption fine structure (EXAFS) spectroscopic studies were conducted on Co(II)-substituted VanX. Electronic spectroscopy revealed the presence of Co(II) ligand field transitions that had molar absorptivities of approximately 100 m(-1) cm(-1), which suggests that Co(II) is five-coordinate in Co(II)-substituted VanX. Low temperature EPR spectra of Co(II)-substituted VanX were simulated using spin Hamiltonian parameters of M(S) = |+/-1/2), E/D = 0.14, g(real(x,y)) = 2.37, and g(real(z)) = 2.03. These parameters lead to the prediction that Co(II) in the enzyme is five-coordinate and that there may be at least one solvent-derived ligand. Single scattering fits of EXAFS data indicate that the metal ions in both native Zn(II)-containing and Co(II)-substituted VanX have the same coordination number and that the metal ions are coordinated by 5 nitrogen/oxygen ligands at approximately 2.0 angstroms. These data demonstrate that Co(II) (and Zn(II) from EXAFS studies) is five-coordinate in VanX in contrast to previous crystallographic studies (Bussiere, D. E., Pratt, S. D., Katz, L., Severin, J. M., Holzman, T., and Park, C. H. (1998) Mol. Cell 2, 75-84). These spectroscopic studies also demonstrate that the metal ion in Co(II)-substituted VanX when complexed with a phosphinate analog of substrate D-Ala-D-Ala is also five-coordinate.

Fixed exit DC-monochromator of general position for side (or top) beam line

We develop an idea of a fixed exit double-crystal monochromator of general position (or skew DC-mono), in which the lines of entering and exit beams (both being fixed) do not lie in one plane, i.e., are in general position. Both cases of identical and not identical crystals are considered, and exact solutions are obtained describing valid positions and orientations of both crystals. Special attention is paid to the case of small lattice mismatch between the first and the second crystal (e.g., due to temperature difference) and small angle of “skewness” (that is to say, an angle between skew lines of entrance and exit beams is much less than unity). We also derive some useful formulations describing beam profile change after two reflections (whose reflection planes are nonparallel).

The INE-beamline for actinide research at ANKA

The Institut für Nukleare Entsorgung (INE) at the Forschungszentrum Karlsruhe is presently constructing and will commission and operate an x-ray spectroscopy beamline dedicated to actinide research at the new synchrotron source ANKA. One great advantage of the INE-Beamline is that on-site, in situ actinide research is possible for studying, e.g., solid-water interface chemical reactions, which are not possible at other facilities. The design is for a multi-purpose beamline, i.e., a number of methods (XAFS, surface sensitive and spatial resolved techniques) are possible on one and the same sample. Planned is a safe and flexible containment concept for activities up to 106 times the limit of exemption. The design will allow spectroscopic investigations using photon energies from the K edge of S (2477 eV) to the Rh K-edge (23 220 eV). The optics include collimating and focusing mirrors for a sub-mm beam dimension at the sample position. A later upgrade is planned to install auxiliary μ-focusing optics (e.g., a single bounce elliptical monocapillary or planar compound refractive lenses). The monochromator at the INE-Beamline is a Lemonnier type double-crystal x-ray monochromator (DCM), built at the Universität Bonn, Physikalisches Institut. The pressure inside the small diameter (380 mm) vacuum housing is ∼106 mbar, allowing fast changes of crystals, avoiding long pumping times. Multi-layer mirrors can be used in the DCM for wide band-pass experiments, e.g., for x-ray fluorescence analysis measurements. Installation of beamline components has been completed in October 2003. Operation begin is targeted for 2004.

XAFS at Ritsumeikan SR center

We have constructed an ultra soft x-ray absorption spectroscopy beamline at BL-2 and an XAFS spectrometer at BL-4 using a compact superconducting radiation source of the Ritsumeikan University. BL-2 is composed from an Au coated pre-focusing mirror and a concave diffraction grating with 1200 grooves/mm and provides VUV absorption spectra by total electron yield method in the energy range 50–250 eV. BL-2 covers the K-edge absorption energies of elements from lithium to boron in the periodic table. BL-4 is composed of a double crystal monochromator with a working range from 15 to 75 deg and Si(220), Ge(220) and InSb(111) crystals. It covers the energy range of 1700–10 500 eV, which corresponds to the K-edge absorption energies of elements from silicon to zinc.

こんなことができる放射光（３）放射光利用におけるＸ線光学素子

Total reflection mirror and crystal monochromator are presented as two major optical elements in synchrotron radiation beamline. Reflectivity, typical X-ray mirrors used at SPring-8 beamlines, and sagittal and tangential focusing are shown for total reflection mirror. Energy range and energy resolution using crystal monochromator, geometry and mechanism for double-crystal monochromator, and cooling of first crystal from high heat load are shown briefly with the examples of SPring-8 standard beamlines. Photon flux through the beamline optics is also estimated with the effective band-width of monochromator.

Ray tracing study for a detuned nondispersed double crystal monochromator

The properties of a detuned nondispersive Si(111) double crystal monochromator were studied by using the ray tracing method. The program used was the PC version of shadow V2.3.3 with gui V1.2. This article concentrates on detuning of the second crystal since detuning of the first crystal causes a larger shift of the energy center of the transmitted beam than detuning of the second one does. The results indicate that for a large detuning angle of the second crystal, the transmitted spectrum splits into two bands with equal bandwidth, which is delayed at a large vertical divergence of the incident beam. With increasing detuning angle of the second crystal, both the fundamental bandwidth (for a well collimated beam) and the harmonic contamination decrease until they reach the minimum at a detuning angle of roughly half the full width at half maximum of the rocking curve, where the left fundamental flux is about 50%. The capability of harmonic suppression by detuning the second crystal is limited, with the harmonic contamination reduced by about two orders of magnitude at most, which implies that other methods, such as double mirror system, must be adopted when smaller harmonic contamination is required.

Time-Resolved Study of the Oxidation of Ethanol by Cerium(IV) Using Combined Quick-XANES, UV−Vis, and Raman Spectroscopies

Time-resolved X-ray absorption spectroscopy (Quick-XANES) has been combined with UV-vis and Raman spectroscopies to study the in situ reduction of Ce4+ to Ce3+ in ethanolic solution with a time resolution of ca. 4-5 s. For this purpose, a cam-driven oscillating double-crystal monochromator with a channel-cut crystal was combined with two spectrometers for UV-vis and Raman spectroscopies in a specialized cell which allows one to fit the optical pathways for all three spectroscopies individually. The results show that high-quality results can be obtained simultaneously, thus giving a detailed insight into the mechanisms of the investigated chemical reaction. The continuous release of nitrate and ethanol ligands from the initial Ce4+ into the solution finally leads to a trivalent cerium species which is only coordinated with water molecules after about 1800 s of reaction time.

Suite of three protein crystallography beamlines with single superconducting bend magnet as the source

At the Advanced Light Source, three protein crystallography beamlines have been built that use as a source one of the three 6 T single-pole superconducting bending magnets (superbends) that were recently installed in the ring. The use of such single-pole superconducting bend magnets enables the development of a hard X-ray program on a relatively low-energy 1.9 GeV ring without taking up insertion-device straight sections. The source is of relatively low power but, owing to the small electron beam emittance, it has high brightness. X-ray optics are required to preserve the brightness and to match the illumination requirements for protein crystallography. This was achieved by means of a collimating premirror bent to a plane parabola, a double-crystal monochromator followed by a toroidal mirror that focuses in the horizontal direction with a 2:1 demagnification. This optical arrangement partially balances aberrations from the collimating and toroidal mirrors such that a tight focused spot size is achieved. The optical properties of the beamline are an excellent match to those required by the small protein crystals that are typically measured. The design and performance of these new beamlines are described.

Synchrotron radiation refraction topography for characterization of lightweight materials

AbstractThe employment of synchrotron radiation for refraction topography of materials has considerable advantages over standard x‐ray sources. The much higher beam intensity and the parallel and monochromatic radiation provide faster measurements and better angular and spatial resolution. X‐ray refraction techniques image the inner surface and interface concentration of micro‐structured materials. This effect of x‐ray optics is additional to small‐angle scattering by diffraction, when the scattering objects reach micrometre dimensions. We have developed x‐ray refraction techniques within the last decade in order to meet the growing demands for improved non‐destructive characterization of high‐performance composites, ceramics and other low‐density materials. Sub‐micron particle dimensions, the pore size of ceramics, the crack density distribution and single fibre debonding within damaged composites can be measured and visualized by computer‐generated interface topographs. For this purpose investigations are now being performed at the new hard x‐ray beamline of the Federal Institute for Materials Research and Testing (BAM) at BESSY, Berlin. This BAMline provides monochromatic radiation of photon energies from 5 to 60 keV from a double multilayer and/or a double‐crystal monochromator. A separate instrument is dedicated to the further development and application of synchrotron radiation refraction (SRR) topography. Different from conventional small‐angle scattering cameras with collimating slits and pinholes, scattering angles down to a few seconds of arc are selected by a single‐crystal analyser, similar to a Bonse–Hart diffractometer. A 20 µm spatial resolution of the scattering micro‐structures is achieved by a CCD camera with a fluorescent converter. First SRR topographs of aircraft composites [carbon fibre‐reinforced plastics (CFRP), carbon fibre‐reinforced ceramics (C/C), metal matrix ceramics (MMC)] will be reported. Copyright © 2004 John Wiley & Sons, Ltd.

An inelastic X-ray scattering spectrometer at LNLS.

A high-resolution spectrometer aimed at performing experiments of inelastic X-ray scattering by electronic excitations is described. The spectrometer has been installed at the D12A-XRD1 beamline of the National Synchrotron Light Laboratory (LNLS), in Campinas, Brazil. Synchrotron radiation is monochromated to about 6 keV and focused horizontally onto the sample by a sagittally focusing Si(111) double-crystal monochromator in non-dispersive setting. The spectrometer operates in Rowland circle geometry and is based on a focusing Si(333) analyser in near-backdiffraction geometry for energy analysis of inelastically scattered photons. The analyser works at a fixed Bragg angle, so energy transfers are obtained by varying the incident photon energy. A relative energy resolution of the whole spectrometer of approximately 1.5 x 10(-4) at 5.93 keV has been achieved. As an example of application, inelastic X-ray scattering by plasmon excitation in polycrystalline Be was measured. Test results demonstrate that inelastic X-ray scattering experiments with eV energy resolution and an acceptable counting rate are feasible at the LNLS when focused on plasmon and particle-hole excitations.

Analysis of the mutual coherence function of X-rays using dynamical diffraction

X-ray rocking-curve profiles for a perfect crystal are calculated using the mutual coherence function of the incident wave. The derived result is that the rocking curve to be measured should be a convolution of the intrinsic profile of the crystal reflection with the Fourier transform of the complex degree of coherence of the incident wave. This allows experimental evaluation of the complex degree of coherence from measured rocking-curve profiles with the help of the calculated intrinsic profile. The mutual coherence function of synchrotron X-rays prepared with a conventional Si double-crystal monochromator was mapped as a function of both spatial separation and time delay.

X-ray absorption fine structure spectrometer using a compact superconducting synchrotron radiation source

We have constructed an x-ray absorption fine structure (XAFS) spectrometer at BL-4 using the compact superconducting synchrotron radiation (SR) source at Ritsumeikan University. BL-4 is simply designed and consists of a slit, a double-crystal monochromator, and two detectors. The mechanical movement of the monochromator is in the range from 15° to 75°. By using Si(220), Ge(220), and InSb(111) crystals, the XAFS spectrometer covers the K-edge absorption energies of elements from silicon to zinc under atmospheric pressure. The incident x-ray intensity is measured by an ionization chamber with a path length of 4.5 cm. The transmitted x-ray intensity after passing through a sample is monitored by either an ionization chamber with a path length of 31 cm or a scintillation counter. The steep decrease of x-ray intensities above 5 keV is characteristic of the spectrum of photons emitted from the compact SR source and the photon flux at 10 keV is two to three orders of magnitude smaller than that at 5 keV. Hence, the contamination of higher-order harmonics is negligible above 5 keV. The double-crystal monochromator should be detuned only in measuring K-edge XAFS spectra of K, Ca, and Sc by using Si(220) or Ge(220). Suitable gases for two ionization chambers are easily selected only based on the detection efficiency of He(100%), N2(100%), N2(85%)+Ar(15%), N2(50%)+Ar(50%), and Ar(100%) gases. The photon flux passing through a 2 mm×9 mm aperture is estimated from the ion current of the ionization chamber. Though the values normalized to 1 mm2 are a few orders of magnitude smaller than those of BL7C at the Photon Factory, it turned out that measurements of XAFS spectra of good quality are very easy to obtain from 1.7 to 10.5 keV by using the spectrometer at BL-4.

X–ray facility for the ground calibration of the X–ray monitor JEM-X on board INTEGRAL

We describe the X-ray facility developed for the calibration of the X-ray monitor JEM-X on board the INTEGRAL satellite. The apparatus allowed the scanning of the detector geometric area with a pencil beam of desired energy over the major part of the passband of the instrument. The monochromatic radiation is obtained with the use of a double crystal monochromator at fixed exit. We discuss the facility performance.

Non-existence of positive glitches in spectra using the YB(66) double-crystal monochromator of BL15XU at Spring-8.

YB(66) is suitable for dispersing synchrotron radiation in the 1-2 keV energy range with a 2d lattice spacing of 1.17 nm. When used with an undulator there are no positive glitches at 1385.6 and 1438 eV in spectra dispersed by a YB(66) 400 double-crystal monochromator as observed using bending-magnet or wiggler beamlines. The transmission function of a YB(66) double-crystal monochromator has been measured by means of a Si PIN photodetector, and X-ray absorption near-edge structure (XANES) of Mg, Al and Si were measured at high resolution. From all of these experiments it has been clarified that a YB(66) double-crystal monochromator is well suited for soft X-ray beamlines on third-generation light sources.