Kurt Goetze

A rotational and axial motion system load frame insert for in situ high energy x-ray studies

High energy x-ray characterization methods hold great potential for gaining insight into the behavior of materials and providing comparison datasets for the validation and development of mesoscale modeling tools. A suite of techniques have been developed by the x-ray community for characterizing the 3D structure and micromechanical state of polycrystalline materials; however, combining these techniques with in situ mechanical testing under well characterized and controlled boundary conditions has been challenging due to experimental design requirements, which demand new high-precision hardware as well as access to high-energy x-ray beamlines. We describe the design and performance of a load frame insert with a rotational and axial motion system that has been developed to meet these requirements. An example dataset from a deforming titanium alloy demonstrates the new capability.

Diffraction properties of multilayer Laue lenses with an aperture of 102 µm and WSi₂/Al bilayers.

We report on the characterization of a multilayer Laue lens (MLL) with large acceptance, made of a novel WSi2/Al bilayer system. Fabrication of multilayers with large deposition thickness is required to obtain MLL structures with sufficient apertures capable of accepting the full lateral coherence length of x-rays at typical nanofocusing beamlines. To date, the total deposition thickness has been limited by stress-buildup in the multilayer. We were able to grow WSi2/Al with low grown-in stress, and asses the degree of stress reduction. X-ray diffraction experiments were conducted at beamline 1-BM at the Advanced Photon Source. We used monochromatic x-rays with a photon energy of 12 keV and a bandwidth of ΔE/E=5.4·10(-4). The MLL was grown with parallel layer interfaces, and was designed to have a large focal length of 9.6 mm. The mounted lens was 2.7 mm in width. We found and quantified kinks and bending of sections of the MLL. Sections with bending were found to partly have a systematic progression in the interface angles. We observed kinking in some, but not all, areas. The measurements are compared with dynamic diffraction calculations made with Coupled Wave Theory. Data are plotted showing the diffraction efficiency as a function of the external tilting angle of the entire mounted lens. This way of plotting the data was found to provide an overview into the diffraction properties of the whole lens, and enabled the following layer tilt analyses.

X-ray optics testing beamline 1-BM at the advanced photon source

Beamline 1-BM at the APS has been reconfigured in part for testing of synchrotron optics with both monochromatic and white beams. Operational since 2013, it was reconfigured to accommodate users of the APS as well as users from other DOE facilities. Energies between 6 and 28 keV are available. The beamline was reconfigured to remove two large mirrors and to provide a 100 mm wide monochromatic beam at 54 m from the source. In addition a custom white beam shutter was implemented for topography exposures as short as 65 millisec over the full available horizontal width. Primary agendas include both white beam and monochromatic beam topography, Talbot grating interferometry, and tests of focusing optics. K-B mirrors, MLLs, and FZPs have been characterized. Measurements of the spatial coherence lengths on the beamline were obtained with Talbot interferometry. Topography data has been reported.

Precision mechanical design of an ultrahigh-resolution inelastic x-ray scattering spectrometer system with CDFDW optics at the APS

There are many scientific applications, especially involving topics related to the equilibrium atomic-scale dynamics of condensed matter, that require both a narrower and a steeper resolution function and access to a broader dynamic range than are currently available. To meet these important scientific needs, a prototype of a novel ultrahigh-resolution inelastic x-ray scattering spectrometer system has been designed and constructed at undulator-based beamline 30-ID at the Advanced Photon Source, Argonne National Laboratory. This prototype is designed to meet challenging mechanical and optical specifications for performing so-called CDFDW angular-dispersive x-ray crystal optics, which include a central ultra-thin CFW crystal and a pair of dispersing elements. The abbreviation CDFDW stands for: C – collimating crystal, D – dispersing-element crystal (two D-crystals are used in each CDFDW), F – anomalous transmission filter, and W – wavelength-selector crystal [1]. The mechanical design of the ultrahigh-resolution inelastic x-ray scattering spectrometer, as well as the preliminary test results of its precision positioning performance are presented in this paper.

EPICS and its role in data acquisition and beamline control

Beamline-control and data-acquisition software based on EPICS (a tool kit for building distributed control systems) has been running on many Advanced Photon Source beamlines for several years. EPICS itself, the collaborative software-development effort surrounding it, and EPICS-based beamline software have been described previously in general terms. This talk will review and update that material, focusing on the role EPICS core software plays in beamline applications and on the effects of a few defining characteristics of EPICS on the beamline software we have developed with it.

Adaptive angular control of high-resolution x-ray optics

Adaptive angular control of reflecting crystals is crucial for reliable operation of high-resolution x-ray optics at synchrotron radiation facilities. An anglular compensation with nanoradian tolerance is required for some advanced applications. We present a working solution, a null-detection feedback system which was successfully applied for stabilization of an x-ray monochromator with energy resolution of ΔE/E ≈ 10−8(E = 23.7 keV). Another possible application of the feedback system, stabilization of optical cavity for x-ray free electron laser oscillator (XFELO) is discussed.

Beamline control and data acquisition software (invited)

An international collaboration of software developers has been working for several years to advance the state of the art of control systems and has produced software and development methods that are directly applicable to synchrotron radiation (SR) instrumentation. The software is collectively entitled EPICS and is essentially an extensible tool kit for implementing distributed control systems. The EPICS collaboration now includes developers representing many of the Advanced Photon Source (APS) beamlines, as well as developers from the Stanford Synchrotron Radiation Laboratory, the Advanced Light Source, and the Gemini and Keck telescopes. As part of this collaboration, we have developed software tools for controlling and acquiring data from SR beamlines and combined them with tools developed by others to support laboratories and experiments at the APS and other SR facilities. Applications of EPICS‐based software in SR instrumentation will be described, some consequences of collaborative development will ...

Projection x-ray topography system at 1-BM x-ray optics test beamline at the advanced photon source

Projection X-ray topography of single crystals is a classic technique for the evaluation of intrinsic crystal quality of large crystals. In this technique a crystal sample and an area detector (e.g., X-ray film) collecting intensity of a chosen crystallographic reflection are translated simultaneously across an X-ray beam collimated in the diffraction scattering plane (e.g., [1, 2]). A bending magnet beamline of a third-generation synchrotron source delivering x-ray beam with a large horizontal divergence, and therefore, a large horizontal beam size at a crystal sample position offers an opportunity to obtain X-ray topographs of large crystalline samples (e.g., 6-inch wafers) in just a few exposures. Here we report projection X-ray topography system implemented recently at 1-BM beamline of the Advanced Photon Source. A selected X-ray topograph of a 6-inch wafer of 4H-SiC illustrates capabilities and limitations of the technique.

Ultra‐stable sub‐meV monochromator for hard X‐rays

A 0.27 meV-bandwidth monochromator for 21.5 keV synchrotron radiation demonstrates exceptional stability using cryogenic stabilization and active feedback control.

A fast white-beam shutter for hard x-ray topography at beamline 1-BM of the Advanced Photon Source

Beamline 1-BM at the Advanced Photon Source (APS) delivers a white beam from a bending magnet with very intense x-ray photon flux. One important application of this beamline is white-beam x-ray topography imaging for crystal-based x-ray optics development and for industrial characterization of single crystals and epitaxial materials. Due to the intense photon flux from the third-generation synchrotron source of the APS, the exposure time of the imaging process should be accurately controlled down to the millisecond level. For this purpose we have designed and implemented a fast shutter that is vacuum compatible to 10−8 torr. The aperture is a copper block with a 70 mm horizontal and 5 mm vertical opening and is water cooled. The aperture is moved vertically up and down by means of a linear voice-coil actuator. The apertures position is controlled using encoder feedback in a servo loop running on an industrial motion controller. A shutter opening response time of 32 milliseconds was measured. In this paper, we describe the shutter mechanics and its associated electronics installed at the 1-BM, and we report example white-beam topographs of diamond type IIa crystals.