Curt Preissner

A twelve-analyzer detector system for high-resolution powder diffraction.

A dedicated high-resolution high-throughput X-ray powder diffraction beamline has been constructed at the Advanced Photon Source (APS). In order to achieve the goals of both high resolution and high throughput in a powder instrument, a multi-analyzer detector system is required. The design and performance of the 12-analyzer detector system installed on the powder diffractometer at the 11-BM beamline of APS are presented.

Combining scanning tunneling microscopy and synchrotron radiation for high-resolution imaging and spectroscopy with chemical, electronic, and magnetic contrast

The combination of high-brilliance synchrotron radiation with scanning tunneling microscopy opens the path to high-resolution imaging with chemical, electronic, and magnetic contrast. Here, the design and experimental results of an in-situ synchrotron enhanced x-ray scanning tunneling microscope (SXSTM) system are presented. The system is designed to allow monochromatic synchrotron radiation to enter the chamber, illuminating the sample with x-ray radiation, while an insulator-coated tip (metallic tip apex open for tunneling, electron collection) is scanned over the surface. A unique feature of the SXSTM is the STM mount assembly, designed with a two free-flex pivot, providing an angular degree of freedom for the alignment of the tip and sample with respect to the incoming x-ray beam. The system designed successfully demonstrates the ability to resolve atomic-scale corrugations. In addition, experiments with synchrotron x-ray radiation validate the SXSTM system as an accurate analysis technique for the study of local magnetic and chemical properties on sample surfaces. The SXSTM systems capabilities have the potential to broaden and deepen the general understanding of surface phenomena by adding elemental contrast to the high-resolution of STM.

A high-fidelity harmonic drive model.

In this paper, a new model of the harmonic drive transmission is presented. The purpose of this work is to better understand the transmission hysteresis behavior while constructing a new type of comprehensive harmonic drive model. The four dominant aspects of harmonic drive behavior - nonlinear viscous friction, nonlinear stiffness, hysteresis, and kinematic error - are all included in the model. The harmonic drive is taken to be a black box, and a dynamometer is used to observe the input/output relations of the transmission. This phenomenological approach does not require any specific knowledge of the internal kinematics. In a novel application, the Maxwell resistive-capacitor hysteresis model is applied to the harmonic drive. In this model, sets of linear stiffness elements in series with Coulomb friction elements are arranged in parallel to capture the hysteresis behavior of the transmission. The causal hysteresis model is combined with nonlinear viscous friction and spectral kinematic error models to accurately represent the harmonic drive behavior. Empirical measurements are presented to quantify all four aspects of the transmission behavior. These measurements motivate the formulation of the complete model. Simulation results are then compared to additional measurements of the harmonic drive performance.

Optomechanical Design of a Hard X-ray Nanoprobe Instrument with Nanometer-Scale Active Vibration Control

We are developing a new hard x‐ray nanoprobe instrument that is one of the centerpieces of the characterization facilities of the Center for Nanoscale Materials being constructed at Argonne National Laboratory. This new probe will cover an energy range of 3–30 keV with 30‐nm spacial resolution. The system is designed to accommodate x‐ray optics with a resolution limit of 10 nm, therefore, it requires staging of x‐ray optics and specimens with a mechanical repeatability of better than 5 nm. Fast feedback for differential vibration control between the zone‐plate x‐ray optics and the sample holder has been implemented in the design using a digital‐signal‐processor‐based real‐time closed‐loop feedback technique. A specially designed, custom‐built laser Doppler displacement meter system provides two‐dimensional differential displacement measurements with subnanometer resolution between the zone‐plate x‐ray optics and the sample holder. The optomechanical design of the instrument positioning stage system with n...

Management of metadata and automation for mail‐in measurements with the APS 11‐BM high‐throughput, high‐resolution synchrotron powder diffractometer

A high-resolution and high-throughput synchrotron powder diffractometer has been automated for use with samples that are mailed in by Advanced Photon Source users. Implementation of a relational database with web interfaces for both outside users and beamline staff, which is integrated into the facility-wide proposal and safety system, allows all aspects of beamline management to be integrated. This system permits users to request kits for mounting samples, to provide sample safety information, to obtain their collected data and to provide usage information upon project completion in a quick and simple manner. Beamline staff use a separate interface to note receipt of samples, schedule and collect diffraction data, post-process and quality-check data, and dispose of samples. The design of the software and database are discussed in detail.

Design and performance of an ultra-high-vacuum-compatible artificial channel-cut monochromator.

The design and performance of a novel ultra-high-vacuum-compatible artificial channel-cut monochromator that has been commissioned at undulator beamline 8-ID-I at the Advanced Photon Source are presented. Details of the mechanical and optical design, control system implementation and performance of the new device are given. The monochromator was designed to meet the challenging stability and optical requirements of the X-ray photon correlation spectroscopy program hosted at this beamline. In particular, the device incorporates a novel in-vacuum sine-bar drive mechanism for the combined pitch motion of the two crystals and a flexure-based high-stiffness weak-link mechanism for fine-tuning the pitch and roll of the second crystal relative to the first crystal. The monochromator delivers an exceptionally uniform and stable beam and thereby improved brilliance preservation.

Design of a precision flexural linear stage system with sub- nanometer resolution and 12-mm travel range

Precision ball-bearing-based or roller-bearing-based positioning stage systems are capable of providing a large travel range. However, it is not possible to meet requirements in sub-nanometer positioning resolution, high tilting stiffness, and microradian-level straightness of trajectory repeatability with a simple rolling element guiding system. To meet those requirements and still allow for large travel range, we have designed a novel precision flexural linear stage. It is capable of sub-nanometer positioning resolution and 12-mm travel range for synchrotron radiation instrumentation applications. The design and preliminary test results for a prototype stage system are discussed in this paper.

Experimental investigation and model development for a harmonic drive transmission

Harmonic drive transmissions (HDTs) are compact, low-backlash, high-ratio, high-resolution rotary motion transmissions. One application to benefit from these attributes is the revolute joint robot. Engineers at the Advanced Photon Source (APS) are investigating the use of this type of robot for the positioning of an x-ray detector; understanding the properties of the robot components is crucial to modeling positioner behavior. The robot bearing elements had been investigated previously, leaving the transmission as the missing component. While the benefits of HDTs are well known, the disadvantages, including fluctuating dissipation characteristics and nonlinear stiffness, are not understood as well. These characteristics can contribute uncontrolled dynamics to the overall robot performance. A dynamometer has been constructed at the APS to experimentally measure the HDTs response. Empirical torque and position data were recorded for multiple transmission load cases and input conditions. In turn, a computer model of the dynamometer HDT system was constructed to approximate the observed response.

Initial Characterization and Design of an UHV‐Compatible Artificial Channel‐Cut Monochromator

We present initial characterization results of a novel ultra‐high‐vacuum‐compatible artificial channel‐cut monochromator that has been installed as part of undulator beamline 8‐ID‐I at the Advanced Photon Source. We present details of the mechanical design and control‐system implementation of the new device. The monochromator has been designed to meet the challenging stability and optical requirements of the x‐ray photon correlation spectroscopy program hosted at this beamline. In particular, the device incorporates a novel in‐vacuum sine‐bar drive mechanism for the combined pitch motion of the two crystals and a flexure‐based high‐stiffness weak‐link mechanism for fine tuning the pitch and roll of the second crystal relative to the first crystal.

Design and test of a differential scanning stage system for an x-ray nanoprobe instrument

We have developed a prototype instrument with a novel interferometrically controlled differential scanning stage system. The system consists of 9 DC-motor-driven stages, 4 picomotor-driven stages, and 2 PZT-driven stages. A custom-built laser Doppler displacement meter system provides two-dimensional (2D) differential displacement measurement with subnanometer resolution between the zone-plate x-ray optics and the sample holder. The entire scanning system was designed with high stiffness, high repeatability, low drift, flexible scanning schemes, and possibility of fast feedback for differential motion. Designs of the scanning stage system, as well as preliminary mechanical test results, are presented in this paper.