We will present the design for the In-Situ Nanoprobe (ISN) beamline that is being developed as part of the Upgrade of the APS storage ring with an MBA magnetic lattice. The ISN will provide large working distance of 60 mm for in-situ and operando environments, and a small spot of 20 nm (25 keV) for imaging materials with small defects and functional components. To achieve both long working distance and small spot size, Kirkpatrick-Baez mirrors will be used as nanofocusing optics. The major contrast mechanisms will be XRF imaging for chemical characterization ptychography for transmission imaging with sub-10 nm resolution. Auxiliary diffraction capabilities will allow monitoring of phase change during in-situ studies. To achieve the demagnification required to achieve small spot sizes, the ISN instrument will be placed at a distance of 220 m from the x-ray source, in a satellite building outside the APS storage ring. The ISN will provide hard x-rays with photon energy between 4.8 keV and 30 keV, enabling access to the absorption edges of to most elements in the periodic system. The MBA lattice and insertion devices, coupled with the high reflectivity of the K-B mirror system, provide a very high coherent flux of above 4*1012 Ph/s at 5 keV, and 6*1012 Ph/s at 30 keV. This allows hierarchical imaging of large samples with very small spot size, as well as multidimensional imaging, such as 3D imaging and temperature change, or 2D imaging with change of several environmental parameters. The ISN will provide flow of fluids, gases, and variable temperature.
The Transmission X-ray Microscope (TXM) at beamline 32-ID-C of the Advanced Photon Source (APS) is a high throughput instrument with high spatial resolution for operando nano-tomography experiments [1]. Recently, a flexural nanopositioning stage system has been designed, and constructed at the APS for a set of JTECTM Kirkpatrick-Baez (KB) mirrors to be installed at the beamline 32-ID-C station. It will focus X-ray down to a 15-20 nm focal spot that will serve as a point source for projection microscopy. Many flexural stages in the stage system are using the same designs developed by APS for the beamline 34-ID-E [2]. However, the new stage system configuration is optimized for the operation conditions at the APS 32-ID-C to accommodate large nano-tomography sample stages. The experiences gained from this new flexural nanopositioning stage system design will benefit designs of K-B mirror nanofocusing stages for other x-ray nanoprobe beamline instruments at the APS-Upgrade project, especially for the In-Situ Nanoprobe instrument design. The mechanical design of the flexural stages, as well as its preliminary mechanical test results with laser interferometer are described in this paper.
The Advanced Photon Source Upgrade (APS-U) project will construct several new, best-in-class beamlines and enhancements to existing beamlines to exploit the massive increase in coherent flux enabled by the new storage ring lattice. APS-U will also enhance several existing beamlines to boost their performance. X-ray tomography is a common imaging mode for several of these beamlines, so there is demand for the highest-precision rotation of the sample. For example, the In Situ Nanoprobe (ISN, 19-ID), a next-generation hard x-ray nanoprobe, will use x-ray fluorescence tomography and ptychographic 3D imaging as key imaging modes with a spot size of 20 nm. It will require <100 nm runout and single-micro-radian wobble errors of the rotation stage to achieve full 3D resolution. Such precise requirements for a rotation stage can be achieved with air bearing rotation stages. However, this approach puts constraints on sample positioning design in terms of the sample environment (air bearing stages are generally not vacuum compatible) and the large mass of air bearing rotation stages. Mechanical bearing stages do not equal the precision runout/wobble specifications of air bearings. In order to use mechanical stages and approach air bearing level precision, the errors of the mechanical stage have to be measured precisely. We have then designed a metrology system using interferometer or capacitive sensors for the nanopositioning support lab as a diagnostic tool and to be portable for quality assurance testing of stages at the beamline.
Ptychography was used to determine the focus of a Multilayer-Laue-Lens (MLL) at beamline 1-BM at the Advanced Photon Source (APS). The MLL had a record aperture of 102 microns with 15170 layers. The measurements were made at 12 keV. The focal length was 9.6 mm, and the outer-most zone was 4 nm thick. MLLs with ever larger apertures are under continuous development since ever longer focal lengths, ever larger working distances, and ever increased flux in the focus are desired. A focus size of 25 nm was determined by ptychographic phase retrieval from a gold grating sample with 1 micron lines and spaces over 3.0 microns horizontal distance. The MLL was set to focus in the horizontal plane of the bending magnet beamline. A CCD with 13.0 micron pixel size positioned 1.13 m downstream of the sample was used to collect the transmitted intensity distribution. The beam incident on the MLL covered the whole 102 micron aperture in the horizontal focusing direction and 20 microns in the vertical direction. 160 iterations of the difference map algorithm were sufficient to obtain a reconstructed image of the sample. The present work highlights the utility of a bending magnet source at the APS for performing coherence-based experiments. Use of ptychography at 1-BM on MLL optics opens the way to study diffraction-limited imaging of other hard x-ray optics.
The ever-increasing spatial resolution of nanofocusing hard x-ray optics, coupled with the need for long working distances and spectroscopic imaging, requires stages that translate optics and samples over millimeters with trajectory errors of under 10 nm. To overcome the performance limitations of precision ball-bearing-based or roller-bearing-based linear stage systems, compact vertical and horizontal linear nanopositioning flexure stages, with centimeter-level travel range, have been designed and tested at the Advanced Photon Source (APS) for x-ray instrumentation applications. The mechanical design and finite element analyses of the flexural stages, as well as its preliminary test results with laser interferometers are described in this paper.
Stress in multilayer Laue lenses can be reduced by choosing unequal thicknesses for the two layers comprising a bilayer
in the zone plate structure. We demonstrate this with the wafer curvature measured in-operando for sputter deposition of
WSi2/Si bilayers. The curvature measurements showed that the compressive stress built in the multilayers during the
deposition process bent the substrate wafers where these multilayers were coated onto it. Within equal thickness WSi2/Si
bilayers, the Si layers contribute more compressive stress than the WSi2 layers at a 4 mTorr Argon environment.
Reducing the ratio of Si’s thickness in the WSi2/Si bilayer decreased the total stress.
The Advanced Photon Source is currently developing a suite of new hard x-ray beamlines, aimed primarily at the study
of materials and devices under real conditions. One of the flagship beamlines of the APS Upgrade is the In-Situ
Nanoprobe beamline (ISN beamline), which will provide in-situ and operando characterization of advanced energy
materials and devices under change of temperature and gases, under applied fields, in 3D.
The ISN beamline is designed to deliver spatially coherent x-rays with photon energies between 4 keV and 30 keV to the
ISN instrument. As an x-ray source, a revolver-type undulator with two interchangeable magnetic structures,
optimized to provide high brilliance throughout the range of photon energies of 4 keV – 30 keV, will be used. The
ISN instrument will provide a smallest hard x-ray spot of 20 nm using diffractive optics, with sensitivity to sub-10
nm sample structures using coherent diffraction. Using nanofocusing mirrors in Kirkpatrick-Baez geometry, the ISN
will also provide a focus of 50 nm with a flux of 8·1011 Photons/s at a photon energy of 10 keV, several orders of
magnitude larger than what is currently available. This will allow imaging of trace amounts of most elements in the
periodic table, with a sensitivity to well below 100 atoms for most metals in thin samples. It will also enable nanospectroscopic
studies of the chemical state of most materials relevant to energy science. The ISN beamline will be
primarily used to study inorganic and organic photovoltaic systems, advanced batteries and fuel cells, nanoelectronics devices, and materials and systems diesigned to reduce the environmental impact of combustion.
Hard X-ray fluorescence microscopy is one of the most sensitive techniques to perform trace elemental analysis of
unsectioned biological samples, such as cells and tissues. As the spatial resolution increases beyond sub-micron
scale, conventional sample preparation method, which involves dehydration, may not be sufficient for preserving
subcellular structures in the context of radiation-induced artifacts. Imaging of frozen-hydrated samples under
cryogenic conditions is the only reliable way to fully preserve the three dimensional structures of the samples while
minimizing the loss of diffusible ions. To allow imaging under this hydrated “natural-state” condition, we have
developed the Bionanoprobe (BNP), a hard X-ray fluorescence nanoprobe with cryogenic capabilities, dedicated to
studying trace elements in frozen-hydrated biological systems. The BNP is installed at an undulator beamline at Life
Sciences Collaboration Access Team at the Advanced Photon Source. It provides a spatial resolution of 30 nm for
fluorescence imaging by using Fresnel zone plates as nanofocusing optics. Differential phase contrast imaging is
carried out in parallel to fluorescence imaging by using a quadrant photodiode mounted downstream of the sample.
By employing a liquid-nitrogen-cooled sample stage and cryo specimen transfer mechanism, the samples are well
maintained below 110 K during both transfer and X-ray imaging. The BNP is capable for automated tomographic
dataset collection, which enables visualization of internal structures and composition of samples in a nondestructive
manner. In this presentation, we will describe the instrument design principles, quantify instrument performance,
and report the early results that were obtained from frozen-hydrated whole cells.
Kirkpatrick-Baez (K-B) mirrors [1] are sophisticated x-ray micro- and nano-focusing tools for synchrotron radiation applications. A prototype of a modular x-ray K-B mirror mount system has been designed and tested at an optics testing beamline, 1-BM at the Advanced Photon Source (APS), Argonne National Laboratory (ANL). This compact, costeffective modular mirror mount system is designed to meet challenging mechanical and optical specifications for producing high positioning resolution and stability for various scientific applications with focused hard x-ray beams down to the 100-nanometer scale. The optomechanical design of the modular x-ray K-B mirror mount system as well as the preliminary test results of its precision positioning performance are presented in this paper.
A 2-D linear flexure stage system is designed with high structure stiffness using the laminar over-constrained weak-link
mechanism presented in this paper. This design is a new development in the application of redundantly constrained
laminar structures as weak-link mechanisms. The novelty of this new mechanical design is its fishbone-shaped multiple-parallelogram
structure, which performs the function of a high-stiffness, high-precision linear motion guider with subcentimeter
travel range and sub-nanometer positioning resolution.
Potential applications of this new stage system include advanced development of ultra-precision positioning stages for
the scanning x-ray nanoprobes, long-range scanning atomic force microscopes, and equipment for nanotechnology and
semiconductor industries.
Hard x-ray point focusing by two crossed multilayer Laue lenses is studied using a full-wave modeling approach. This study shows that for a small numerical aperture, the two consecutive diffraction processes can be decoupled into two independent ones in respective directions. Using this theoretical tool, we investigate adverse effects of various misalignments on the 2D focus profile and discuss the tolerance to them. We also derive simple expressions that describe
the required alignment accuracy.
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.
We introduce a new design of tilted linear zone plates, which are named tapered tilted linear (TTL) zone plates. The purpose of the design is to increase efficiency while at the same time keeping the focal plane perpendicular to the optical path. In order to accomplish this, the zone radius and number of zones must become a function of position along the structure. Simulation work described in this paper shows improved optical performance over regular tilted linear zone plates.
Using Fresnel zone plates, a spatial resolution between 20 nm for soft x-rays and 70 nm for hard x-rays has been achieved. Improvement of the spatial resolution without loss of efficiency is difficult and incremental due to the fabrication challenges posed by the combination of small outermost zone width and high aspect ratios. We describe a novel approach for high-resolution x-ray focusing, a multilayer Laue lens (MLL). The MLL concept is a system of two crossed linear zone plates, manufactured by deposition techniques. The approach involves deposition of a multilayer with a graded period, sectioning it to the appropriate thickness, assembling the sections at the optimum angle, and using it in Laue geometry for focusing. The approach is particularly well suited for high-resolution focusing optics for use at high photon energy. We present a theory of the MLL using dynamic diffraction theory and Fourier optics.
Zone plates with depth to zone-width ratios as large as 100 are needed for focusing of hard x-rays. Such high aspect ratios are challenging to produce by lithography. We are investigating the fabrication of high-aspect-ratio linear zone plates by multilayer deposition followed by sectioning. As an initial step in this work, we present a synchrotron x-ray study of constant-period multilayers diffracting in Laue (transmission) geometry. Data are presented from two samples: a 200 period W/Si multilayer with d-spacing of 29 nm, and a 2020 period Mo/Si multilayer with d-spacing of 7 nm. By cutting and polishing we have successfully produced thin cross sections with section depths ranging from 2 to 12 μm. Transverse scattering profiles (rocking curves) across the Bragg reflection exhibit well-defined interference fringes originating from the depth of the sample, in agreement with dynamical diffraction theory for a multilayer in Laue geometry.
The design of a contact-cooled horizontally reflecting high-heat-load mirror for use as the first optical element on an Advanced Photon Source (APS) beamline is described. The radiation source consists of a set of two collinear undulators producing an x-ray beam with up to 340 W/mm2 peak normal heat flux at the mirror located 30 m from the source. The beam incident angle is 2.6 mrad (0.15°). The mirror is 500 mm long and 75 mm wide. Specifications for this mirror are an rms tangential slope error ≤ 2 μrad and an rms roughness ≤ 2 Å. The mirror substrate is single crystal silicon. To selectively reflect photons with cut-off energies in the 7 to 33
keV range, the central part of the mirror may be coated with strips of Rh, Pt, and Be. Thermal and structural analyses of the mirror (steady state and transient) are reported. Two contact-cooling options considered are back and side cooling. The slope error of side cooling is smaller than that for back cooling. The influence of
the mirror thickness and the cooling zone are analyzed. Other options to reduce the slope error are discussed.
We use Fresnel zone plates as focusing optics in hard x-ray microprobes at energies typically between 6 and 30 keV. While a spatial resolution close to 0.1 μm can currently be achieved, highest spatial resolution is obtained only at reduced diffraction efficiency due to manufacturing limitations with respect to the aspect ratios of zone plates. To increase the effective thickness of zone plates, we are stacking several identical zone plates on-axis in close proximity. If the zone plates are aligned laterally to within better than an outermost zone width and longitudinally within the optical near-field, they form a single optical element of larger effective thickness and improved efficiency and reduced background from undiffracted radiation. This allows us both to use zone plates of moderate outermost zone width at energies of 30 keV and above, as well as to increase the efficiency of zone plates with small outermost zone widths particularly for the energy range of 6 - 15 keV.
Images of magnetic structures in a SmCo/Fe bilayer have been obtained using a circularly polarized hard x-ray microprobe. This probe combines circularly polarizing and microfocusing optics (either Fresnel zone plate or Kirkpatrick-Baez mirrors) to provide a highly polarized, small cross-section x-ray beam in the energy range between 5 and 12 keV. By using x-rays in this energy range, we can penetrate the top layers of the sample and therefore are able to measure the magnetic domains of buried magnetic structures with a resolution of ~5 micrometers . Contrast between magnetic domains is obtained by measuring the x-ray magnetic circular dichroism signal for different points as the beam is scanned across the sample. Images of the magnetic domain structure in a 1600-A-thick buried SmCo layer of a SmCo/Fe bilayer were taken as a function of the externally applied magnetic field. These images show the nucleation of large domains ( > 100 micrometers ) whose domain walls are oriented perpendicular to the applied field direction. Upon increasing the applied field, the images show the growth of the local reversed domains as the domain walls propagate across the sample, leading to a complete reorientation of the hard magnetic layer.
Fresnel zone plates (ZP) have gained popularity as the optics of choice for advanced microfocusing applications. The main virtues of ZP are high resolution, high efficieny, low background, coherence preservation, and ample working distance. Zone plates are also unique because they are a normal incidence x-ray optics, which are much easier to align and use compared to other grazing incidence optics. We will report here recent progress that has drastically enhanced the performance of ZPs in 1) higher spatial resolution, 2) higher focusing efficiency, and 3) extension to higher energies. With the new developments, zone plates have proven to be one of the best microfocusing optics for monochromatic x-ray beams.
Jorg Maser, Henry Chapman, Chris Jacobsen, Alex Kalinovsky, Janos Kirz, Angelika Osanna, Steve Spector, Steve Wang, Barry Winn, Sue Wirick, Xiaodong Zhang
The Stony Brook scanning transmission x-ray microscope (STXM) has been operating at the X1A beamline at the NSLS since 1989. A large number of users have used it to study biological and material science samples. We report on changes that have been performed in the past year, and present recent results. To stabilize the position of the micro probe when doing spectral scans at high spatial resolution, we have constructed a piezo-driven flexure stage which carries out the focusing motion of the zone plate needed when changing the wavelength. To overcome our detector limitation set by saturation of our gas-flow counter at count rates around 1 MHz, we are installing an avalanche photo diode with an active quenching circuit which we expect to respond linearly to count rates in excess of 10 MHz. We have improved the enclosure for STXM to improve the stability of the Helium atmosphere while taking data. This reduces fluctuations of beam absorption and, therefore, noise in the image. A fast shutter has been installed in the beam line. We are also developing a cryo- STXM which is designed for imaging frozen hydrated samples at temperatures below 120 K. At low temperatures, radiation sensitive samples can tolerate a considerably higher radiation dose than at room temperature. This should improve the resolution obtainable from biological samples and should make recording of multiple images of the same sample area possible while minimizing the effects of radiation damage. This should enable us to perform elemental and chemical mapping at high resolution, and to record the large number of views needed for 3D reconstruction of the object.
An x-ray microscopy resource center for biological x-ray imaging will be built at the Advanced Light Source (ALS) in Berkeley, California. The unique high brightness of the ALS allows short exposure times and high image quality. Two microscopes, an x-ray microscope (XM) and a scanning x-ray microscope (SXM) are planned. These microscopes serve complementary needs. The XM gives images in parallel at comparable short exposure times, and the SXM is optimized for low radiation doses applied to the sample. The microscopes extend visible light microcopy toward significantly higher resolution and permit images of objects in an aqueous medium. High resolution is accomplished by the use of Fresnel zone plates. Design considerations to serve the needs of biological x-ray microscopy are given. Also the preliminary design of the microscopes is presented. Multiple wavelength and multiple view images will provide elemental contrast and some degree of 3-D information.
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