25 results on '"Dean R. Haeffner"'
Search Results
2. Effect of ceramic preform geometry on load partitioning in Al2O3–Al composites with three-dimensional periodic architecture
- Author
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Jonathan Almer, R. Rao, David C. Dunand, Dean R. Haeffner, Jennifer A. Lewis, and Marcus L. Young
- Subjects
Diffraction ,Materials science ,Mechanical Engineering ,Metal matrix composite ,Composite number ,Synchrotron radiation ,Condensed Matter Physics ,Synchrotron ,law.invention ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,law ,visual_art ,X-ray crystallography ,visual_art.visual_art_medium ,Aluminium oxide ,General Materials Science ,Ceramic ,Composite material - Abstract
Interpenetrating Al 2 O 3 /Al composites were created by liquid-metal infiltration of 3D periodic ceramic preforms with face-centered-tetragonal symmetry produced by direct-write assembly. Volume-averaged lattice strains in the ceramic phase of the composite were measured by synchrotron X-ray diffraction for various levels of uniaxial compression stresses. Load transfer is found to occur from the metal phase to the ceramic phase, and the magnitude of the effect is in general agreement with simple rule-of-mixtures models. Spatially resolved diffraction measurements show variations in load transfer at two different positions within the composite for the elastic- and damage-deformation regimes, the latter being observed using phase-enhanced synchrotron imaging. The mechanical behavior of these interpenetrating Al 2 O 3 /Al composites with face-centered-tetragonal symmetry are compared with previous interpenetrating Al 2 O 3 /Al composites with simple-tetragonal symmetry.
- Published
- 2009
3. Synchrotron X-ray diffraction and imaging of ancient Chinese bronzes
- Author
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Dean R. Haeffner, David C. Dunand, Francesca Casadio, Marcus L. Young, Jonathan Almer, and S. Schnepp
- Subjects
Diffraction ,Materials science ,business.industry ,Synchrotron radiation ,Advanced Photon Source ,General Chemistry ,Western Zhou ,engineering.material ,Microstructure ,Synchrotron ,law.invention ,Optics ,law ,X-ray crystallography ,engineering ,General Materials Science ,Bronze ,business - Abstract
High-energy synchrotron X-ray diffraction and imaging experiments were performed at the Advanced Photon Source on two ancient Chinese bronzes from the Art Institute of Chicago with the goal to nondestructively study their microstructure. The first object, a bronze fragment from an early Western Zhou dynasty vessel (Hu, 11th/10th century B.C.), was investigated with spatially-resolved diffraction to reveal the depth and composition of the surface corrosion layer as well as the composition and grain size of the underlying bronze core. The second object, a bronze dagger-axe (Ge, 3rd/2nd century B.C.) with a silver-inlaid sheath, was studied under both diffraction and imaging conditions. It was found to have been cast as a single object, answering longstanding scholars’ questions on whether the ceremonial object concealed an interior blade.
- Published
- 2006
4. Synchrotron applications in archaeometallurgy: Analysis of high zinc brass astrolabes
- Author
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G. Brian Stephenson, Brian D. Newbury, Michael R. Notis, Jon Almer, Dean R. Haeffner, G. S. Cargill, and Bruce Stephenson
- Subjects
Diffraction ,Radiation ,Materials science ,Annealing (metallurgy) ,Archaeometallurgy ,Metallurgy ,chemistry.chemical_element ,Zinc ,Condensed Matter Physics ,Microstructure ,Synchrotron ,law.invention ,Brass ,chemistry ,Cementation process ,law ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,Instrumentation - Abstract
Synchrotron X rays were used to perform nondestructive transmission diffraction and fluorescence experiments on a group of 24 European and Islamic astrolabes dated between 1350–1720 A.D. in order to determine their compositions. A group of six astrolabes produced in Lahore between 1601–1662 A.D. were found to contain a mixed α+β brass microstructure, proving that the brass was produced by a comelting technique rather than the traditional cementation process. The results also show evidence of dezincification, attributed to heavy annealing of the brass during astrolabe manufacture. This effect was so severe that an accurate analysis of the bulk Zn composition could not be determined from the fluorescence results alone; transmission X-ray diffraction gives a more accurate measurement of the bulk Zn composition.
- Published
- 2004
5. Separating the recrystallization and deformation texture components by high-energy X-rays
- Author
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Alexandru D. Stoica, Jonathan Almer, Ulrich Lienert, Y.D. Wang, Dean R. Haeffner, and Xun-Li Wang
- Subjects
Diffraction ,Materials science ,business.industry ,Recrystallization (metallurgy) ,General Biochemistry, Genetics and Molecular Biology ,Synchrotron ,Physics::Geophysics ,law.invention ,Optics ,law ,High-energy X-rays ,Synchrotron diffraction ,Monochromatic color ,Composite material ,business - Abstract
High-energy synchrotron diffraction offers great potential for experimental study of recrystallization kinetics. Measurements on partially recrystallized samples using a monochromatic high-energy synchrotron beam show that recrystallized grains generate sharp diffraction spots, whereas the intensity from the deformed matrix varies smoothly along the Debye–Scherrer rings. Based on these observations, a method has been developed to separate the recrystallization texture components from those originating from the deformation matrix. The validity of this method is demonstrated with partially recrystallized interstitial-free steel.
- Published
- 2002
6. Characterization and application of a GE amorphous silicon flat panel detector in a synchrotron light source
- Author
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Karena W. Chapman, C. Aydιner, John H. Lee, Joel V. Bernier, Antonino Miceli, Jonathan Almer, Peter J. Chupas, Dean R. Haeffner, G. Vera, Peter L. Lee, K. Kump, and Ulrich Lienert
- Subjects
Physics ,Nuclear and High Energy Physics ,business.industry ,Detector ,Pair distribution function ,Synchrotron radiation ,Advanced Photon Source ,Synchrotron ,Flat panel detector ,law.invention ,Distribution function ,Optics ,law ,Optical transfer function ,business ,Instrumentation - Abstract
Characterization, in the language of synchrotron radiation, was performed on a GE Revolution 41RT flat panel detector using the X-ray light source at the Advanced Photon Source (APS). The detector has an active area of 41 x 41 cm{sup 2} with 200 x 200 {micro}m{sup 2} pixel size. The nominal working photon energy is around 80 keV. Modulation transfer function (MTF) was measured in terms of line spread function (LSF) using a 25 {micro}m x 1 cm tungsten slit. Memory effects of the detector elements, called lag, were also measured. The large area and fast data capturing rate - 8 fps in unbinned mode, 30 fps in binned or region of interest (ROI) mode - make the GE flat panel detector a unique and very versatile detector for synchrotron experiments. In particular, we present data from pair distribution function (PDF) measurements to demonstrate the special features of this detector.
- Published
- 2007
7. A high energy phase retarder for the simultaneous production of right- and left-handed circularly polarized x rays
- Author
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C. T. Venkataraman, Sarvjit Shastri, Dean R. Haeffner, C. S. Nelson, George Srajer, and J. C. Lang
- Subjects
Physics ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Compton scattering ,Particle accelerator ,Advanced Photon Source ,Undulator ,Polarization (waves) ,Retarder ,Light scattering ,law.invention ,Optics ,law ,business ,Instrumentation ,Circular polarization - Abstract
We have fabricated and characterized the performance of a monolithic Ge Bragg–Laue phase retarder capable of simultaneously producing both right- and left-handed circularly polarized x rays. The energy range of operation of the phase retarder is between 50 and 100 keV making it well suited to the measurement of spin-dependent Compton profiles within the impulse approximation, primarily because of the increased momentum resolution and larger Compton scattering cross section available at these higher incident energies. Although the phase retarder was optimized for operation at 86 keV, it can produce highly circularly polarized x rays over a substantial energy range. The performance of the phase retarder was tested via magnetic Compton scattering measurements on an Fe sample at the undulator A of the Advanced Photon Source. It was found to perform well in terms of flux and degree of circular polarization thereby greatly reducing the data collection times required for this inherently weak scattering process.
- Published
- 1998
8. Mapping the chemical states of an element inside a sample using tomographic x-ray absorption spectroscopy
- Author
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Alfons Baiker, A. Mashayekhi, Marion Kuhlmann, Bruno Lengeler, Dirk Lützenkirchen-Hecht, Ronald Frahm, Jan-Dierk Grunwaldt, Christian G. Schroer, B. Griesebock, Dean R. Haeffner, Esther Ziegler, Til Florian Gunzler, and M. Richwin
- Subjects
Microprobe ,X-ray spectroscopy ,X-ray absorption spectroscopy ,Physics and Astronomy (miscellaneous) ,Absorption spectroscopy ,Chemistry ,business.industry ,XANES ,law.invention ,Chemical state ,Optics ,law ,Density of states ,Atomic physics ,business ,Monochromator - Abstract
Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near-edge spectra of an elemental species at each location on an arbitrary virtual section through a sample. These spectra reveal the local concentrations of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state, the local atomic structure, and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses.
- Published
- 2003
9. Germanium X-ray phase plates for the production of circularly polarized X-rays
- Author
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George Srajer, Dennis M. Mills, Dean R. Haeffner, C. J. Yahnke, and Lahsen Assoufid
- Subjects
Physics ,Nuclear and High Energy Physics ,Silicon ,Physics::Instrumentation and Detectors ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,X-ray ,chemistry.chemical_element ,Particle accelerator ,Germanium ,Radiation ,Polarization (waves) ,Synchrotron ,law.invention ,Optics ,chemistry ,law ,Atomic physics ,business ,Instrumentation ,Circular polarization - Abstract
We have constructed an X-ray phase plate to produce linearly and circularly polarized X-rays at discrete energies between 20 keV and 88 keV. The plate is a monolithic two-crystal design, constructed from germanium. We have measured the degree of circular polarization at 65 keV to be 90%±4%, which is significantly better than that produced by silicon phase plates. This radiation was used to measure the magnetic Compton profile for Fe, which was found to be in good agreement with theory and previous work. The underlying X-ray optics and the characterization of the device between 62 keV and 93 keV at the Cornell High Energy Synchrotron Source are presented.
- Published
- 1994
10. Recent design upgrades of the APS beamline standard components
- Author
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Dean R. Haeffner, Mohan Ramanathan, and Deming Shu
- Subjects
Physics ,business.industry ,Electrical engineering ,Synchrotron radiation ,X-ray optics ,Particle accelerator ,Advanced Photon Source ,law.invention ,Optics ,Reliability (semiconductor) ,Beamline ,law ,Component (UML) ,business ,Instrumentation - Abstract
Over the last five years, based on the operating experiences, many upgrades have been made to the beamline standard components to continue improving beamline performance and reliability at the Advanced Photon Source (APS). In this article, the particular design upgrades, as well as the new component design specifications of APS beamline standard components, are summarized.
- Published
- 2002
11. Nanophase evolution at semiconductor/electrolyte interface in situ probed by time-resolved high-energy synchrotron X-ray diffraction
- Author
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Dean R. Haeffner, Tu T. Truong, Yugang Sun, Jonathan Almer, Lin Wang, Yang Ren, and Wenge Yang
- Subjects
Materials science ,business.industry ,Mechanical Engineering ,Nucleation ,Nanoparticle ,Synchrotron radiation ,Bioengineering ,General Chemistry ,Electrolyte ,Condensed Matter Physics ,Synchrotron ,law.invention ,Crystallography ,Semiconductor ,law ,X-ray crystallography ,Optoelectronics ,General Materials Science ,Wafer ,business - Abstract
Real-time evolution of nanoparticles grown at the semiconductor/electrolyte interface formed between a single crystalline n-type GaAs wafer and an aqueous solution of AgNO(3) has been studied by using high-energy synchrotron X-ray diffraction. The results reveal the distinct nucleation and growth steps involved in the growth of anisotropic Ag nanoplates on the surface of the GaAs wafer. For the first time, a quick transit stage is observed to be responsible for the structural transformation of the nuclei to form structurally stable seeds that are critical for guiding their anisotropic growth into nanoplates. Reaction between a GaAs wafer and AgNO(3) solution at room temperature primarily produces Ag nanoplates on the surface of the GaAs wafer in the dark and at room temperature. In contrast, X-ray irradiation can induce charge separation in the GaAs wafer to drive the growth of nanoparticles made of silver oxy salt (Ag(7)NO(11)) and silver arsenate (Ag(3)AsO(4)) at the semiconductor/electrolyte interface if the GaAs wafer is illuminated by the X-ray and reaction time is long enough.
- Published
- 2010
12. Experimental characterization of APS undulator A at high photon energies (50-200 keV)
- Author
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Roger J. Dejus, Dean R. Haeffner, and Sarvjit Shastri
- Subjects
Physics ,Nuclear and High Energy Physics ,Radiation ,Photon ,Wiggler ,Particle accelerator ,Advanced Photon Source ,Undulator ,law.invention ,Computational physics ,Nuclear physics ,law ,Physics::Accelerator Physics ,Thermal emittance ,Instrumentation ,Beam (structure) ,Beam divergence - Abstract
The considerable intensity of Advanced Photon Source (APS) undulator A as a source of high-energy X-rays permits the performance of numerous types of experiments that require such photon energies. Measured and calculated properties, in the 50-200 keV range, of the X-ray beam from undulator A, installed in sector 1 of the APS, are presented. The flux spectra observed at various gaps agree well with calculations that incorporate the actual magnetic field within the device and the emittance and energy spread of the stored positrons. The field errors and energy spread cause the X-ray beam to lose undulator radiation properties at high energies, as seen in the smeared-out spectral harmonics and increased beam divergence, giving resemblance to a low-K wiggler source. Owing to the wiggler-like behavior in this photon-energy range, the optimal operating condition for undulator A is in the vicinity of the closed-gap setting, corresponding to a maximum critical energy.
- Published
- 2006
13. Tomographic x-ray absorption spectroscopy
- Author
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Alfons Baiker, Marion Kuhlmann, B. Griesebock, M. Richwin, A. Mashayekhi, Bruno Lengeler, Christian G. Schroer, Jan-Dierk Grunwaldt, Eric Ziegler, Dirk Lützenkirchen-Hecht, Ronald Frahm, Dean R. Haeffner, and Til Florian Gunzler
- Subjects
Microprobe ,X-ray absorption spectroscopy ,Materials science ,Absorption spectroscopy ,business.industry ,Analytical chemistry ,XANES ,Spectral line ,law.invention ,Optics ,law ,Density of states ,Tomography ,business ,Monochromator - Abstract
Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near edge spectra of an elemental species at each location on an arbitrary virtual section through a sample. These spectra reveal the local concentrations of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state, the local atomic structure, and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses. The full XANES spectra reconstructed at each point of the tomographic slice allow to detect slight variations in concentrations of chemical compounds, such as metallic and monovalent copper. The method is applied to the analysis of a heterogeneous catalyst.
- Published
- 2004
14. Internal Strain Measurements and X-ray Imaging in Interpenetrating-Phase Al2O3/Al Composites
- Author
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Dean R. Haeffner, Jon Almer, Wah-Keat Lee, David C. Dunand, Marcus L. Young, Ulrich Lienert, and Kamel Fezzaa
- Subjects
Diffraction ,Materials science ,Spatially resolved ,Composite number ,Analytical chemistry ,X-ray ,chemistry.chemical_element ,Synchrotron ,law.invention ,chemistry ,law ,Aluminium ,Lattice (order) ,Composite material ,Rule of mixtures - Abstract
Interpenetrating Al2O3/Al composites were created by liquid-metal infiltration of alumina preforms with three-dimensional periodicity produced by a robotic deposition method. Volume-averaged lattice strains in the alumina phase were measured by synchrotron x-ray diffraction at various uniaxial compression stresses up to 350 MPa. Load transfer, which is experimentally found to occur between the aluminum and the alumina phase, is in agreement with simple rule of mixtures models. Spatially resolved measurements showed variations in load transfer at different positions within the composite for the elastic-, plastic-, and damage-deformation regimes. Using phase-enhanced imaging, the extent of damage within the composites was observed.
- Published
- 2004
15. Precision white‐beam slit design for high power‐density x‐ray undulator beamlines at the Advanced Photon Source
- Author
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Deming Shu, Christa Brite, J. Collins, T. Nian, D. Ryding, W. Yun, Tuncer M. Kuzay, E. E. Alp, Dean R. Haeffner, and Y. Li
- Subjects
Physics ,Electromagnet ,business.industry ,Advanced Photon Source ,Particle accelerator ,Undulator ,Electromagnetic radiation ,Slit ,law.invention ,Optics ,law ,Electrical equipment ,business ,Instrumentation ,Beam (structure) - Abstract
A set of precision horizontal and vertical white‐beam slits has been designed for the Advanced Photon Source x‐ray undulator beamlines at Argonne National Laboratory. There are several new design concepts applied in this slit set, including a grazing‐incidence knife‐edge configuration to minimize the scattering of x rays downstream, enhanced heat transfer tubing to provide water cooling, and a secondary slit to eliminate the thermal distortion on the slit knife edge. The novel aspect of this design is the use of two L‐shaped knife‐edge assemblies, which are manipulated by two precision X‐Z stepping linear actuators. The principal and structural details of the design for this slit set are presented in this paper.
- Published
- 1995
16. In situSynchrotron Study of Phase Transformation Behaviors in Bulk Metallic Glass by Simultaneous Diffraction and Small Angle Scattering
- Author
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Xun-Li Wang, Jonathan Almer, Alexandru D. Stoica, C.T. Liu, Yangyang Wang, Weihua Wang, Jinkui Zhao, and Dean R. Haeffner
- Subjects
Diffraction ,Amorphous metal ,Materials science ,Chemical physics ,law ,Scattering ,Phase (matter) ,Nucleation ,General Physics and Astronomy ,Crystallization ,Small-angle scattering ,Supercooling ,law.invention - Abstract
We have used a new approach involving simultaneous diffraction and small angle scattering to study the amorphous-to-crystalline phase transformation in Zr-based bulk metallic glass. In situ, time-resolved data provided the first direct demonstration of a phase separation prior to crystallization. There is evidence that nucleation and growth of the crystalline phase occur in separate stages, with different kinetics. Our data support the view that crystalline nucleation is achieved via short-range diffusion of small atoms (e.g., Ni), whereas the growth is dictated by long-range diffusion.
- Published
- 2003
17. High-energy diffuse scattering on the 1-ID beamline at the advanced photon source
- Author
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Jonathan Almer, Thomas Welberry, Dean R. Haeffner, Darren Goossens, and Peter T Lee
- Subjects
Diffraction ,Nuclear and High Energy Physics ,Radiation ,Materials science ,Photon ,business.industry ,Resolution (electron density) ,Synchrotron radiation ,Particle accelerator ,Advanced Photon Source ,law.invention ,Optics ,Beamline ,law ,X-ray crystallography ,business ,Instrumentation - Abstract
This paper reports on experiments in which high-energy (65.35 keV) X-rays were used to record the detailed diffuse diffraction patterns of a number of ceramic materials. The methodology has enabled a greater q-range to be explored (up to sintheta/lambda approximately 0.97) than is possible with laboratory-based experiments, with better q-space resolution and increased sensitivity, thus allowing previously unseen detail in diffraction patterns to be recorded. In all, 11 sections of data have been collected for Ca-CSZ, eight for Y-CSZ and six for wuestite.
- Published
- 2002
18. High Temperature X-Ray Diffraction in Transmission Under Controlled Environment
- Author
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Dean R. Haeffner, Matthew J. Kramer, Jonathan Lang, E. M. Deters, R. W. McCallum, J. J. Williams, L. Margulies, Stefan Kycia, and Alan I. Goldman
- Subjects
Diffraction ,Temperature gradient ,Materials science ,law ,Wiggler ,Analytical chemistry ,Synchrotron radiation ,Particle accelerator ,Advanced Photon Source ,Tube furnace ,Undulator ,law.invention - Abstract
A compact tube furnace has been developed for high temperature X-ray diffraction studies using high energy synchrotron radiation. The furnace design has a low absorption path in transmission yet allows for a high degree of control of the sample atmosphere and a minimal temperature gradient across the sample. The design allows for a maximum temperature of 1500°C with a variety of atmospheres including inert, reducing, and oxidizing. Preliminary results obtained at the SRI-CAT I-ID undulator line (60keV) at the APS facility and the A2 24 pole wiggler line (45keV) at CHESS on the Ti5Si3Z5 (Z = C, N, O) system will be presented to demonstrate the feasibility of this approach.
- Published
- 1998
19. Smart X-ray beam position monitor system using artificial-intelligence methods for the Advanced Photon Source insertion-device beamlines
- Author
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Tuncer M. Kuzay, Deming Shu, Juan Barraza, Hai Ding, Dean R. Haeffner, and Mohan Ramanathan
- Subjects
Nuclear and High Energy Physics ,Engineering ,Digital signal processor ,Radiation ,business.industry ,Electrical engineering ,Advanced Photon Source ,Particle accelerator ,Signal ,Insertion device ,law.invention ,Front and back ends ,Software ,Beamline ,law ,business ,Instrumentation - Abstract
At the Advanced Photon Source (APS), each insertion-device (ID) beamline front end has two X-ray beam position monitors (XBPMs) to monitor the X-ray beam position for both vertical and horizontal directions. Performance challenges for a conventional photoemission-type XBPM during operations are contamination of the signal from the neighbouring bending-magnet sources and the sensitivity of the XBPM to the insertion-device gap variations. Problems are exacerbated because users change the ID gap during their operations, and hence the percentage level of the contamination in the front-end XBPM signals varies. A smart XBPM system with a high-speed digital signal processor has been built at the Advanced Photon Source for the ID beamline front ends. The new version of the software, which uses an artificial-intelligence method, provides a self-learning and self-calibration capability to the smart XBPM system. The structure of and recent test results with the system are presented in this paper.
- Published
- 1997
20. Emittance, brilliance, and bandpass issues related to an inclined crystal monochromator
- Author
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Albert T. Macrander, Dean R. Haeffner, and Paul L. Cowan
- Subjects
Diffraction ,Physics ,business.industry ,Physics::Optics ,Undulator ,law.invention ,Full width at half maximum ,Optics ,Reflection (mathematics) ,law ,Crystal monochromator ,X-ray crystallography ,Diffraction topography ,business ,Monochromator - Abstract
The inclined double crystal monochromator arrangement is very effective in handling high heat loads and holds considerable promise as a monochromator for undulator beams at third generation synchrotrons. Results for the ideal inclined crystal case have been obtained by dynamical diffraction calculations, and diffraction results for the (111) reflection of silicon are presented for an inclination angle of 85{degree}0 and energies of 5 key and 13.84 key. The diffraction characteristics resemble closely diffraction from-asymmetric (111) plane of silicon. However, the inclined and noninclined cases are not identical. Diffraction in the inclined case is slightly different due to refraction. The full width at half maximum of the Darwin-Prins reflectivity curve is slightly increased ({approximately}l%), and the angles of the outgoing beam after one reflection are slightly altered. That is, except for a wave incident at the Laue point in reciprocal space, the diffraction is always slightly asymmetric. The effect can be exactly reversed by an identical second crystal in the (+,{minus}) arrangement.
- Published
- 1993
21. Emittance, brilliance, and bandpass issues related to an inclined crystal monochromator
- Author
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Albert T. Macrander, Dean R. Haeffner, and Paul L. Cowan
- Subjects
Physics ,Diffraction ,business.industry ,Physics::Optics ,Undulator ,law.invention ,Full width at half maximum ,Optics ,Reflection (mathematics) ,law ,Crystal monochromator ,X-ray crystallography ,Diffraction topography ,business ,Monochromator - Abstract
The inclined double crystal monochromator arrangement is very effective in handling high heat loads and holds considerable promise as a monochromator for undulator beams at third generation synchrotrons. Results for the ideal inclined crystal case have been obtained by dynamical diffraction calculations, and diffraction results for the (111) reflection of silicon are presented for an inclination angle of 85{degrees} and energies of 5 keV and 13.84 keV. The diffraction characteristics resemble closely diffraction from a symmetric (111) plane of silicon. However, the inclined and noninclined cases are not identical. Diffraction in the inclined case is slightly different due to refraction. The full width at half maximum of the Darwin-Prins reflectivity curve is slightly increased ({approximately} 1%), and the angles of the outgoing beam after one reflection are slightly altered. That is, except for a wave incident at the Laue point in reciprocal space, the diffraction is always slightly asymmetric. The effect can be exactly reversed by an identical second crystal in the (+,-) arrangement.
- Published
- 1992
22. Tomographic XRay Absorption Spectroscopy
- Author
-
Christian G. Schroer, Marion Kuhlmann, Bruno Lengeler, Alfons Baiker, Ronald Frahm, Dean R. Haeffner, T. F. Gnzler, Esther Ziegler, Jan-Dierk Grunwaldt, D. LtzenkirchenHecht, M. Richwin, B. Griesebock, and A. Mashayekhi
- Subjects
X-ray spectroscopy ,X-ray absorption spectroscopy ,Microprobe ,Materials science ,Absorption spectroscopy ,business.industry ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,XANES ,law.invention ,Optics ,law ,Density of states ,Tomography ,business ,Mathematical Physics ,Monochromator - Abstract
Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near edge spectra of an elemental species at each point on an arbitrary virtual section through a sample. These spectra reveal the local concentration of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses. The full XANES spectra reconstructed at each point of the tomographic slice allow one to detect slight variations in concentration of the chemical compounds, such as Cu and Cu(I)2O.
- Published
- 2005
23. Performance of Advanced Photon Source insertion devices at high photon energies (50–300 keV)
- Author
-
Sarvjit Shastri, Dean R. Haeffner, Jonathan Lang, and Roger J. Dejus
- Subjects
Physics ,Photon ,Scattering ,business.industry ,Wiggler ,Synchrotron radiation ,Particle accelerator ,Advanced Photon Source ,Undulator ,law.invention ,Optics ,law ,Harmonics ,Physics::Accelerator Physics ,Atomic physics ,business ,Instrumentation - Abstract
Since high‐energy photons (≳50 keV) are well suited for certain types of x‐ray scattering experiments, we present calculated results for the Advanced Photon Source (APS) Undulator A and APS Wiggler A at high energies. The undulator calculations include the effect of magnetic field errors, which is to smear the high‐order spectral harmonics. At their anticipated initial minimum gap settings, Undulator A should perform better than Wiggler A from the point of view of most high energy experiments up to at least ∼280 keV. A comparison of APS insertion devices to high energy insertion devices in other synchrotron radiation laboratories is also provided.
- Published
- 1996
24. High-energy x-ray optics developments at Advanced Photon Source beamline 1-ID (abstract)
- Author
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Dean R. Haeffner, Sarvjit Shastri, Barry P. Lai, J. M. Maser, Wah-Keat Lee, and Kamel Fezzaa
- Subjects
Physics ,Fresnel zone ,Physics::Instrumentation and Detectors ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Compton scattering ,X-ray optics ,Advanced Photon Source ,Undulator ,law.invention ,Optics ,Beamline ,law ,Crystal monochromator ,Physics::Accelerator Physics ,business ,Instrumentation ,Monochromator - Abstract
Three high-energy optics accomplishments are presented. The first is a cryogenically cooled, bent, double-Laue monochromator for 50–200 keV x rays, which delivers over ten times more flux than that from a flat crystal monochromator, but without an increase in energy width. Second, the microfocusing of 50 keV undulator radiation using two stacked Fresnel zone plates is described. Third, a high-resolution inverse-Cauchois scanning analyzer, consisting of a bent Laue crystal, is presented for Compton and fluorescence spectroscopy applications.
- Published
- 2002
25. APS undulator radiation—first results
- Author
-
Elizabeth Moog, Isaac Vasserman, Emil Trakhtenberg, Barry Lai, P. Ilinski, Y. Feng, Wenbing Yun, Efim Gluskin, Zhonghou Cai, Roger J. Dejus, Dean R. Haeffner, D. Legnini, P.K. Den Hartog, and Sarvjit Shastri
- Subjects
Physics ,Photon ,business.industry ,Particle accelerator ,Advanced Photon Source ,Radiation ,Undulator ,law.invention ,Optics ,law ,Physics::Accelerator Physics ,Thermal emittance ,Beam emittance ,business ,Particle beam ,Instrumentation - Abstract
The first undulator radiation has been extracted from the Advanced Photon Source (APS). The results from the characterization of this radiation are very satisfactory. With the undulator set at a gap of 15.8 mm (K=1.61), harmonics as high as the 17th were observed using a crystal spectrometer. The angular distribution of the third-harmonic radiation was measured, and the source was imaged using a zone plate to determine the particle beam emittance. The horizontal beam emittance was found to be 6.9 {plus_minus} 1.0 nm-rad, and the vertical emittance coupling was found to be less than 3%. The absolute spectral flux was measured over a wide range of photon energies, and it agrees remarkably well with the theoretical calculations based on the measured undulator magnetic field profile and the measured beam emittance. These results indicate that both the emittance of the electron beam and the undulator magnetic field quality exceed the original specifications.
- Published
- 1996
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