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Compton scattering and diffuse scattering degenerate the contrast in radiographic images. To avoid such scattering effects, a grid, between the patient and the film is currently used to improve the image quality. Teaching this topic to medical physics students requires demonstration experiments. In this paper, an optical analog to an x-ray radiographic imaging system is described. The setup is inexpensive and is easy to be mounted. A He-Ne laser and a set of lenses (objective lens from a microscope + glass magnifier) were employed to direct a huge parallel beam at the sample. A washer glued onto pinhead-frosted glass was used as a sample. The ceramic part of a catalytic converter was used as a grid. The images, acquired by using a photographic digital camera, show the effect of a grid in cleaning the image (higher contrast): the washer, not seen in the image without the grid, is clearly seen in the image with the grid. (Contains 4 figures.)

An analyzer-based x-ray phase-contrast microscopy (ABM) setup combining a standard analyzer-based x-ray phase-contrast imaging (ABI) setup [nondispersive 4-crystal setup (Bonse-Hart setup)] and diffraction by asymmetrically cut crystals is presented here. An attenuation-contrast microscopy setup with conventional x-ray source and asymmetrically cut crystals is first analyzed. Edge-enhanced effects attributed to phase jumps or refraction/total external reflection on the fiber borders were detected. However, the long exposure times and the possibility to achieve high contrast microscopies by using extremely low attenuation-contrast samples motivated us to assemble the ABM setup using a synchrotron source. This setup was found to be useful for low contrast attenuation samples due to the low exposure time, high contrast, and spatial resolution found. Moreover, thanks to the combination with the nondispersive ABI setup, the diffraction-enhanced x-ray imaging algorithm could be applied. [ABSTRACT FROM AUTHOR]

An analyzer-based x-ray phase contrast imaging (PCI) setup based on channel-cut crystals at the Laboratorio Nacional de Luz Sincrotron (LNLS—Brazilian Synchrotron) is presented. The contrast, visibility, signal-to-noise ratio and spatial resolution of the acquired images were characterized. The potential of PCI for enhancing details of different features with the same x-ray attenuation coefficient is exploited together with cross section simulations of the PCIs acquired at different angular positions on the rocking curve (RC). The present results show that this setup can be used as a standard PCI setup at the LNLS. [ABSTRACT FROM AUTHOR]

This work shows a method to characterize nearly flat reflective surfaces. Slope error on the mirror surface under the total reflection condition of x rays is measured by perfect crystal rocking curve profile widening. The experiment was performed using a conventional x-ray tube and a simple optical setup. The sensitivity was sufficient to detect at least a slope error of 7 μrad, typical quality for synchrotron mirrors. It is shown that this technique can also be used to characterize roughness and curvature. The method proposed here is an alternative to the traditional techniques for surface characterization and has the advantages of simplicity, versatility and sensitivity, and the synchrotron mirror quality can be evaluated under similar conditions as those for the designed operation. [ABSTRACT FROM AUTHOR]

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(lll) double-crystal monochromator in non-dispersive setting. The spectrometer operates in Rowland circle geometry and is based on a focusing Si(333) analyses in near-backdiffraction geometry for energy analysis of inelastically scattered photons. The analyses 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 ∼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. [ABSTRACT FROM AUTHOR]

Examines the efficiency of time modulation of synchrotron radiation by a double-crystal monochromator curved by pulsed surface acoustic waves. Consideration of experimental and theoretical aspect of the study; Confirmation of the efficiency of pulsed modulation of surface acoustic wave; Modifications on a synchrotron radiation double crystal diffractive modulator.

Examines diffraction-enhanced images using two silicon crystals in a non-dispersive set-up at the X-ray diffraction beamline at the Brazilian Synchrotron Light Laboratory. Phase-contrast imaging; Images of biological sample; Use of direct-conversion detector.

The degree of vertical alignment of InAs quantum dots in InAs/GaAs(001) multilayers was studied using grazing incidence x-ray scattering. We show that it is necessary to access one of the weak (200) x-ray reflections to observe the modulation of the GaAs lattice periodicity produced by the stacking of the InAs dots. The degree of alignment of the dots was assessed by fitting the x-ray diffuse scattering profiles near a GaAs (200) reciprocal lattice point. By using a model of gaussian lateral displacement of the dots, we show that we can determine the average value of the mistake in stacking positions of the islands from one bilayer to the next. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the measurement of transmitted diffraction profiles of a germanium crystal at Bragg angles around and including pi/2. Description of a grooved crystal monochromator operating at Bragg angles; Detection of an intensity enhancement at the normal incidence position; Verification of properties of the backscattered regime.

Describes two- and four-crystal reflection x-ray monochromators developed at the Laboratorio Nacional de Luz Sincrotron in Campinas, Brazil. Principle of operation of the two-crystal monochromator; Design of the high-resolution four-reflection monochromator; Performance.

Several recent papers have shown the implementation of analyzer based X-ray phase contrast imaging (ABI) with conventional X-ray sources. The high flux is always a requirement to make the technique useful for bio-medical applications. Here, we present and discuss three important parameters, which need to be taken into account, when searching for the high flux ABI: anisotropic magnification, double image, and source size spread due to intrinsic dispersive diffraction by asymmetrically cut crystals. These parameters, if not well optimized, may cause important features in the acquired images which can mislead the interpretation. A few ways to minimize these effects are implemented and discussed, including some experimental results. [ABSTRACT FROM AUTHOR]

Cataract is a disease that degrades the transparency of crystalline lenses. The crystalline lens is a cellular structure that has a unique shape and protein composition. Cataract is associated with changes in the structure and composition of the lenses. Analyser-based x-ray phase contrast imaging (PCI) is a non-destructive technique that presents images with more contrast and details than the images acquired with conventional synchrotron radiography. Here, an analyser-based x-ray PCI set-up was optimized in the XRD2 beamline at Brazilian Synchrotron Light Laboratory for comparative studies on PCI and conventional synchrotron radiography, for non-cataractous (healthy tissue) and cataractous crystalline (diseased tissue) lenses. Refraction angle and apparent absorption contrast images (diffraction enhanced imaging—DEI) were also obtained. The present PCI and DEI images indicate that the healthy tissue shows enhanced shell structures, while in the diseased tissue these are almost absent. This is associated with the clinical case of total opacity of the cataractous crystalline lenses when it is exposed to visible light. [ABSTRACT FROM AUTHOR]

Self-detection of x-ray diffraction has been accomplished by measuring the electrical behaviour of a semiconductor single-crystal of a commercial detector when it is in and out of the x-ray diffraction condition. A decrease in the photocurrent or in the photocounting is measured when the detector is set in the diffraction condition. The self-detection of x-ray diffraction was imaged using a CCD detector diffracting the Si(400) in a non-dispersive set-up with an external monochromator. The depletion layer of the CCD is about 30 µm thick, which makes it a finite crystal for the energies used in terms of the dynamical theory of x-ray diffraction. The profile, referred to here as the anti-h peak, was obtained from images taken at different diffraction angular positions of the CCD. These profiles are in agreement with those calculated for finite crystals. An application of this effect, where the CCD is used as a detector and an analyser crystal in an analyser-based x-ray phase contrast imaging set-up, is realized here. It could be useful for Multiple Imaging Radiography and related mathematical image processing with the Schlieren method. [ABSTRACT FROM AUTHOR]

Abstract: The LHPG technique has been successfully applied to the growth of single crystals in fiber shape with a controlled composition and lattice parameter gradient along the fiber axis. The GdTaO4–ErTaO4 system was chosen for having a full solubility range. The obtained fibers had a constant gradient of lattice parameters along the axis with a value of 1.24%/cm for the (44¯4) reflection, hence of concentration gradient. Structural characterization results showed that the fibers had a good crystalline quality essential for the optimization of others physical properties. Luminescent characterization showed the behavior of the intensity of green and red luminescence (by 488nm pumping) as a function of concentration of Er3+ and three processes populating the levels (2H11/2, 4S3/2) and 4F9/2 by cross-relaxation energy transfer has been proposed. The results presented show that the compositional gradient and the LHPG technique can be used not only for the growth of crystals with controlled lattice parameter gradients, for potential X-ray diffraction applications, but also as a combinatorial method for the rapid study of material properties as a function of concentration using in situ measurements. [Copyright &y& Elsevier]

Abstract: Gradient single crystal fibers of GdTaO4–YbTaO4 have been grown by laser-heated pedestal growth (LHPG). The crystals of the compounds have differences in the lattice parameters of , and . The crystals obtained exhibit an optimum linear distribution of the compounds along the fiber axis and a lattice spacing gradient value of 2.91%/cm for reflection, the largest value of lattice spacing gradient reported up to this moment. The compositional and structural analysis shows that the LHPG technique and the GdTaO4–YbTaO4 system are very promising for obtaining good quality gradient crystals with large lattice parameters gradient. [Copyright &y& Elsevier]

Abstract: The laser heated pedestal growth technique was used to obtain single crystal fiber of M-type GdTaO4. The fibers were around 3cm long, ∅0.8mm, transparent, colorless and did not exhibit any inclusions. The structural quality of the fibers was evaluated by X-ray rocking curve profiles and X-ray topography. Better quality crystals were grown perpendicular to (010) direction presenting rocking curve FWHM typically around 52arcsec for the reflection. The results confirm that good structural fibers can be successfully obtained by the procedure presented here. [Copyright &y& Elsevier]

High optical and structural quality columbite CaNb2O6 single crystal was grown by laser-heated pedestal growth (LHPG) technique directly from starting reagents. The structural quality of the fibers was evaluated by X-ray rocking curve profile, X-ray phase contrast radiography and X-ray topography measurements whereas optical quality was characterized by optical microscopy and infrared to visible transmission measurements. Raman shifting and structural refinement of X-ray powder diffraction were used to check the formation of single phase CaNb2O6. All results indicate that single phase, crack-free, colorless and transparent CaNb2O6 single crystal fiber was successfully obtained. [Copyright &y& Elsevier]

Despite a considerable effort expended in studying elastic scattering of photons by water, inconsistencies and gaps can still be observed in the literature. One aspect that is not well understood is the effect of temperature on the scattering amplitudes. In order to study this effect, measurements of scattering of photons of 8.05keV on water were performed at scattering angles of 15.9, 28.5, 34.0, 40.5, 57.0 and 66.3° for temperatures from 11°C, 20°C, 25°C, 50°C, 75°C and 90°C maintaining the scattering angle and varying the temperature. The results are consistent with former experiments but no systematic trend was found. [ABSTRACT FROM AUTHOR]

Spherical analyzers are well known instruments for inelastic X-ray scattering (IXS) experiments. High-resolution IXS experiments almost always use Si single crystals as monochromators and spherical analyzers. At higher energies (>20 keV) Si shows a high energy resolution (<10 meV), at an exact symmetric back-diffraction condition, since the energy resolution is given by the real part of the susceptibility or polarizability. However, at low energies (<10 keV), high energy resolution is difficult to achieve with Si. α-SiO 2 (quartz) can be an option, since it offers high energy resolution at low energies. In this work, the characterization of high-quality α-SiO 2 is presented. Such characterization is made by high-resolution rocking curve, topography and lattice parameter mapping in different samples from a single block. X-ray optics with α-SiO 2 for IXS at lower energies (from 2.5 to 12.6 keV) with medium to high energy resolution (from 90 to 11 meV) are proposed and theoretically exploited.

A long x-ray pathway based on an x-ray back-diffraction cavity for coherent x-ray beam experiments is presented. In the present work, such a setup was tested and used for propagation-based x-ray phase contrast imaging (PBI). This setup showed to be useful for PBI purposes, with the advantage of being compact (3 m long) when compared with long x-ray synchrotron beamlines with dimensions from tens to hundreds of meters.

An analyzer-based X-ray phase contrast imaging (ABI) system with an asymmetrical crystal set-up was mounted at Elettra's SYRMEP beamline. It was the first time that this set-up was implemented at Elettra. Advantages and disadvantages of such a set-up were exploited with quantitative and qualitative studies. For quantitative studies a simple hollow tube and strands were used as samples. Qualitative studies were developed using this technique with ox brain tissue, which has never been previously examined in this manner. Minute details were found in the ABIs and in the diffraction enhanced images. This could indicate the possibility of using these techniques with computerized tomography in the future as an auxiliary method in diagnosing brain illnesses such as Alzheimer and Creutzfeldt-Jacob disease. Propagation-based X-ray phase contrast imaging was also qualitatively exploited and compared with ABI using a Loxosceles gaucho spider as a sample.

The linear thermal expansion coefficient of diamond has been measured using forward-diffracted profiles in X-ray backscattering. This experimental technique is presented as an alternative way of measuring thermal expansion coefficients of solids in the high-resolution Bragg backscattering geometry without the intrinsic difficulty of detecting the reflected beam. The temperature dependence of the lattice parameter is obtained from the high sensitivity of the transmitted profiles to the Bragg angle variation with temperature. The large angular width of the backscattering profiles allows the application of this technique to mosaic crystals with high resolution. As an application of this technique the thermal expansion coefficient of a synthetic type-Ib diamond (110) single crystal was measured from 10 to 300 K. Extremely low values (of the order of 1 x 10(-7) +/- 5 x 10(-7)) for the linear thermal expansion coefficient in the temperature range from 30 to 90 K are in good agreement with other reported measurements.

An unusual case of three diffracted beams from a single incoming monochromatic X-ray beam and from the same Bragg plane is reported. Extremely asymmetric diffraction in a thin Si perfect crystal with a cleaved lateral face was experimentally studied. Two of the beams emerge grazing the front and back faces and the third beam emerges from the lateral face.

Versatility was a major consideration in the project to provide an X-ray diffraction station at LNLS. At least two techniques are possible at the station: powder diffraction and multiple single-crystal diffraction. A two-crystal monochromator based on monolithic elastic translators, developed at LNLS, with sagittal focusing by the second crystal, allows 10 mrad of a >/=2 keV monochromatic beam to be used on the diffractometer. The station is equipped with a fast scintillation detector, imaging plates, a high-energy-resolution pin-diode detector, an ionization chamber and a high-angular-resolution soller slit. The data collection and control hardware and software were also developed at LNLS. The theta-2theta goniometry for powder diffraction on this 1 m-diameter diffractometer is based on commercial rotation tables. The multiple single-crystal goniometry is realized by an independent elastic axis driven by differential micrometers for both high- and low-resolution angular movements. At least four independent axes can be positioned as necessary on the diffractometer table. Powder diffractograms and double-crystal rocking curves collected with the synchrotron beam show the expected quality.