This PDF file contains the front matter associated with SPIE Proceedings Volume 11112, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists

Scanning hard x-ray microscopy is a versatile imaging tool that offers a suite of analytic x-ray techniques for studying spatially-resolved elemental, structural and chemical variations. Recent advances in nano-focusing optics and instrumentation have pushed the frontier of the field into multi-modal imaging in 3D and with nanoscale resolution. Here we present current imaging capabilities provided by the hard x-ray nanoprobe of the National Synchrotron Light Source II at Brookhaven National Laboratory. A variety of imaging modalities (absorption, phase, fluorescence and diffraction) will be discussed, as well as the data analysis challenges associated with them. We show that x-ray imaging at about 10 nm resolution has become routine measurements at the beamline, and has been used for a wide spectrum of scientific applications.

We propose a novel confocal x-ray fluorescence (XRF) imaging capability at the X-ray Fluorescence Microprobe (XFM) and Submicron Resolution X-ray Spectroscopy (SRX) beamlines of the National Synchrotron Light Source II (NSLS-II). Comparing to the conventional XRF tomography, this method can image a local region of interest within tens of minutes instead of hours. We will also present the optimized design of the confocal optic and estimated imaging resolution and throughput, based on the real parameters of the beamline photon delivery systems and the proposed confocal setup.

CARNAÚBA (Coherent X-Ray Nanoprobe Beamline) is an X-ray beamline under construction for the SIRIUS light source at LNLS (Brazilian Synchrotron Light Laboratory). The aim of the beamline is to provide multi-analytical and coherent X-ray imaging techniques based on achromatic optics in the energy range between 2 and 15 keV. Computed tomography will extend these techniques into three dimensions. Two end-stations are under development: an all-invacuum nanoprobe (SAPOTI) and a sub-microprobe (TARUMÃ), with a more flexible sample environment and much larger working distance. TARUMÃ will cover a large variety of scientific areas, from environmental, geophysical, agricultural and biological research to energy and more condensed matter related areas. Its design characteristics, with its mechanical design heavily based on precision engineering concepts and predictive modeling, are presented here, as well as some prospects on in situ, in operando and cryogenic sample environment experiments.

Spatial resolution of full-field X-ray microscopes based on total-reflection mirrors was limited by grazing-incidence angle of the mirrors. At practical conditions, achievable spatial resolution is approximately 30 nm. To overcome the limitation, multilayer advanced Kirkpatrick-Baez mirrors and full-field X-ray microscopes with this objective mirrors have been developed in Osaka University and RIGAKU Corp. One of the remarkable points in this design is an achievable spatial resolution of less than 20 nm owing to large grazing-incidence angle and multilayer (Pt/C) with narrow period. Also, the advanced Kirkpatrick-Baez mirrors comprise two mirror pairs based on the Wolter type I and type III optics, respectively, to have sufficiently large magnification even at a compact setup with the whole length of 2 m (between a sample and a camera). The compactness makes it possible to apply the optics to laboratory-based X-ray microscopes, which is another ongoing project. A performance test using a Siemens star chart at an X-ray energy of 8 keV was performed in SPring-8 BL29XUL. The results showed lines with approximately 30-nm width could be resolved. Also, tests of stability and energy dependence confirmed usability of this system.

To date, compound refractive X-ray lenses made out of Beryllium (Be CRLs) have been seldom applied for full-field microscopy with high spatial resolution, which was probably due to residual aberrations of these optics. However, in combination with the recent development of made-to-measure phase plates, the typical spherical aberration of beryllium compound refractive lenses (Be CRLs) can now be completely removed. In this way, distortion-free images of a sample are obtained, which is especially important for tomographic applications. First full-field imaging experiments with aberration-corrected Be CRLs were carried out at beamline P06 at the synchrotron radiation X-ray source PETRA III (DESY Hamburg, Germany). In order to maximize the magnification of the X-ray microscope for full-field microscopy, the full length of the beamline combining the micro- and nanohutch was utilized, enabling a large sample-to-detector distance. In this contribution, we present first imaging results, demonstrating the potential of Be CRLs for direct high-resolution X-ray tomography.

The project of transmission x-ray microscope (TXM) with tender x-ray is undergoing as an extension project of the soft x-ray tomography (SXT) endstation at Taiwan Photon Source (TPS). This TXM is aimed for energy from 1.5 keV to 2.4 keV and with phase contrast with the x-ray energy of 2.4 keV. As the extension of current SXT project, the beamline will be equipped with a variable line spacing (VLS) grating with the multi-layer coating which will be optimized for 2.4 keV. This TXM will be zoneplate based with a phase ring and capillary condenser. In order to match the field of view and numerical aperture (NA) of zoneplate with the emittance of the source in vertical direction, some compromise should be made. To match the low emittance of vertical direction, the NA of zoneplate should be lower and vertical of the secondary source should be larger. This will lower spatial resolution and energy resolution. The targeting resolution of this TXM for phase contrast will be 50nm and FOV is 20 μm. For the detector, which is currently design with a scintillator with a CCD detector. For the future, the direct detector for small pixel and high signal to noise ratio can be obtained. The other components of TXM, such as stages, cryo system, which can be shared with current SXT system which works under the energy of the water window region. This endstation for tender X-ray will be commission in 2020. The detailed design and current progress will be discussed in this presentation.

The PXM (Projection X-ray Microscope) end station was used to complete a preliminary test at the SPring-8 12B2 beamline. The x-ray through scintillator and knife-edge become visible-light image can get from the sensor. The knifeedge image has an edge shape, which can create the edge response line. The edge response line can be differentiated from the point response line. The point response line can then be transferred by Fourier transformation, and achieve MTF (Modulation Transfer Function). Here we apply Chebyshev polynomials to fit the edge response line and calculate the MTF. We used 20× and 50× objective lenses to generate the knife-edge images and calculate the MTF value. We found that the scintillator design resolution is 1 μm, and following the MTF calculation, the image resolutions are about 3 μm and 1.4 μm in the 20× and 50× objective lens, respectively.

Recent plans for x-ray synchrotrons to upgrade to new high brightness lattices have created great excitement about the potential for coherent x-ray imaging to provide a view of nano-materials with high spatial and temporal resolution. However, with increased x-ray brightness comes the inherent risk of radiation damage and the limited speed of current experimental systems. The Advanced Light Source has an extensive program in coherent scanning transmission x-ray microscopy (STXM) and ptychographic imaging with four beamlines covering an energy range of 200 to 2500 eV. Current instrument development efforts are focused on high-dynamic scanning for increased speed and the use of fast x-ray pixel detectors for high resolution ptychographic imaging. Our new microscope, called Nanosurveyor2, can scan at rates of up to 1 mm per second and has achieved a resolution of 3 times the x-ray wavelength. Using this system, we are developing novel scan trajectories and low dose imaging methods which combine high speed conventional STXM imaging with high resolution ptychography. Principal component analysis is used to extract high statistics spectra from noisy and low-resolution STXM data which are then used to _t a small number of ptychographic images for high spatial resolution chemical mapping with relatively low dose. We consider applications in the energy sciences where x-ray exposure has been observed to reduce the oxidation state of relevant compounds.

The X-ray scanning microscope PtyNAMi at beamline P06 of PETRA III at DESY in Hamburg, Germany, is designed for high-spatial-resolution 3D imaging with high sensitivity. Besides optimizing the coherent ux density on the sample and the precision mechanics of the scanner, special care has been taken to reduce background signals on the detector. The optical path behind the sample is evacuated up until the sensor of a four-megapixel detector that is placed into the vacuum. In this way, parasitic scattering from air and windows close to the detector is avoided. The instrument has been commissioned and is in user operation. The main commissioning results of the low-background detector system are presented. A signal-to-noise model for small object details is derived that includes incoherent background scattering.

Among different techniques based on x-ray nanoimaging, ptychography has become a popular tool to study specimens at nanometer-scale resolution without the need of using high-resolution optics that requires very stringent manufacturing processes. This high-resolution imaging method is compatible with other imaging modalities acquired in scanning microscopy. At the Advance Photon Source (APS), we have developed two fluorescence microscopes for simultaneous ptychography and fluorescence imaging which together provide a powerful technique to study samples in biology, environmental science, and materials science. Combined with different tilted sample projections, such correlative methods can yield high-resolution 3D structural and chemical images. More recent work has been focused on the development of a fast ptychography instrument called the Velociprobe which is built to take advantage of the over 100 times higher coherent flux provided by the coming APS upgrade source. The Velociprobe uses high-bandwidth accurate interferometry and advanced motion controls with fast continuous scanning schemes which are optimized for large-scale samples and 3D high-resolution imaging. This instrument has been demonstrated to obtain sub-10 nm resolution with different high-photon-efficient scanning schemes using fast data acquisition rate up to 3 kHz (currently limited by detector's full continuous frame rate). A ptychographic imaging rate of 100 _m2/second with a sub-20 nm spatial resolution was shown in this paper.

X-ray ptychography has become a standard technique for imaging materials at <10 nanometer spatial resolution. Recent developments have shown its potential in obtaining quantitative images of the 2D/3D structure of large objects at millimeter and centimeter-scale, which requires not only new instrumentation and experiment design, but high-throughput workflow for data processing. At Argonne’s Advanced Photon Source, we imaged an integrated chip with over 600 × 600 µm^2 field of view at sub-20 nm spatial resolution and achieved 3000 Hz data acquisition rate with advanced motion control. Here, we discuss challenges in achieving large-area reconstruction and explore strategies for streamlining data processing. We demonstrate a novel data acquisition scheme that combines the merits of both step scan and (continuous) fly scan. Inaccurate scan position and large beam variation also degrade image quality and need to be corrected during reconstruction.

As a scanning version of coherent diffraction imaging (CDI), X-ray ptychography has become a popular and very successful method for high-resolution quantitative imaging of extended specimens. The requirements of mostly coherent illumination and the scanning mechanism limit the throughput of ptychographic imaging. In this paper, we will introduce the methods we use at the Advanced Photon Source (APS) to achieve highthroughput ptychography by optimizing the parameters of the illumination beam. One work we have done is increasing the illumination flux by using a double-multilayer monochromator (DMM) optics with about 0.8% bandwidth. Compared with our double-crystal monochromator (DCM) optics with 0.01% bandwidth, this DMM optics provides around 20 times more flux. A multi-wavelength reconstruction method has been implemented to deal with the consequential degraded temporal coherence from such an illumination to ensure high-quality reconstruction. In the other work, we adopt a novel use of at-top focusing optics to generate a at-top beam with the diameter of about 1.5 μm on the focal plane. The better uniformity of the probe and the large beam size allow one to significantly increase the step size in ptychography scans and thereby the imaging efficiency.

Imaging magnetic materials and structures as a function of external parameters, including magnetic and electric fields, and temperature will provide detailed insight into their dynamics and behavior. Coherent soft x-ray scattering (CSX) beamline at NSLS-II provide researchers a world leading coherent high photon flux with full polarization control. Coherent diffraction imaging, such as resonant soft x-ray ptychography and holography, are under commissioning at CSX and welcome new users. Very recently, we monitored thermal motions of magnetic domain wall with high magnetic contrast and 10nm spatial resolution using holography imaging. Moreover, a new holography chamber has been developed and installed at CSX beamline and it provided holography imaging capability to study magnetic materials as a function of temperature under in-situ condition (current injection and in-vacuum magnetic field). Here, we highlight current achievements and discusses the future potential of magnetic soft X-ray imaging with a spatial resolution of sub-10nm at CSX beamline, NSLS-II.

Transmission microscopes have become a valuable tool for hard X-ray imaging. They allow even complex in situ and operando setups to be realized. However, the objective lens, typically a Fresnel zone plate with a high numerical aperture, is commonly a limiting factor. The small working distance as well as the low efficiency of Fresnel zone plates with high numerical apertures restrict setups either to accommodate specific sample environments or to provide high resolution. Lensless imaging techniques, e.g. ptychography, do not suffer from such adverse effects of Fresnel zone plates. Consequently, they are frequently used for high-resolution X-ray imaging. A recently developed method, X-ray Fourier ptychography aims to combine the benefits of both techniques. It has been shown to provide quantitative high-resolution imaging whilst keeping large working distances for in situ and operando setups. This is achieved by acquiring multiple images with a full-field transmission microscope, each at a different lateral position of the Fresnel zone plate. Moving the objective off the optical axis varies the frequency content for the acquisitions. The resulting dataset is numerically combined using well-established phase retrieval algorithms to recover a complex-valued representation of the sample. Here, we demonstrate how Fourier ptychographic phase retrieval can further be used to mitigate artifacts caused by samples that were placed out of focus, as well as misaligned optical elements. Employing a similar approach to increase the contrast in case of weakly absorbing specimens is also envisioned.

The Diamond Beamline I13L is dedicated to micro- and nano- imaging, with two independently operating branchlines. The imaging branch preforms imaging in real space, with In-line phase contrast imaging and grating interferometry at micrometre resolution and full-field transmission microscopy up to 50nm spatial resolution. Highest spatial resolution is achieved on the coherence branchline, where diffraction imaging methods such as Ptychography and Bragg-CDI are performed. The article provides an update about the experimental capabilities at the beamline with an emphasis on the rapidly evolving ptychography capabilities. The latter has evolved to an user-friendly method with non-expert users able to explore their science without any specific a-priory knowledge.

X-ray microscopy is a mature characterization tool routinely used to answer various questions of science, technology and engineering. The high penetration power of X-rays allows to utilize different characterization methods and reveal elemental composition, crystalline phases, strain distribution, oxidation states etc. in macroscopic and microscopic samples. To obtain comprehensive chemical and structural information at the nanometer scale an X-ray microscope must be equipped with adequate capabilities and allow acquisition of multiple datasets simultaneously. Full-field or scanning X-ray microscopes usually serve this purpose and complement each other. In the recent years, a number of X-ray microscopes have been designed, constructed and commissioned at NSLS-II. In this work we provide an overview of the microscopy instrumentation developments at NSLS-II. It includes the multilayer Laue Lens based nanoprobe optimized for 10 nm spatial resolution imaging, it’s current status and future upgrades; the zone plate based full-field imaging system capable of nano-tomography measurements in less than 1 minute; a laser scanning system optimized for ptychography measurements along with algorithms development, and a new Kirkpatrick-Baez based scanning microscope designed for sub-100 nm spatial resolution experiments.

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 JTEC^TM 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.

Hard X-ray microscopy is a powerful scientific tool capable of providing sub-10 nm spatial resolution imaging of material’s chemical composition and internal structure. Multilayer Laue Lenses (MLLs) have been developed and used for hard x-ray nanofocusing. MLLs are one dimensional X-ray diffractive optics fabricated through multilayer deposition and sectioning. An orthogonal alignment of two MLLs yields a point focus; 10 milli-degree orthogonality and sub-10 µm positioning accuracy along the beam direction is required to avoid astigmatism and achieve 10 nm focal spot size at 12 keV photon energy. Up-to-date, developed x-ray microscopy systems were equipped with eight degrees of nano-scale motion to perform full alignment of individual MLL optics. Bonding of two individual lenses together in pre-determined configuration significantly simplifies alignment process and makes them compatible with a more conventional Zone Plate – based microscopes. In this work, we give an overview of the existing bonding effort and present our approach to fabricate a monolithic 2D MLL optic.

Diffractive optics for nanoscale X-ray imaging, particularly for high energy X-rays, require nanoscale width features with high-aspect ratio thick metal rings (zones) for efficient focusing of X-rays. Electron beam lithography (EBL) has many benefits for producing such structures, allowing patterning of high-resolution and accurately placed structures with placement precisions within a few nanometers over several hundred micrometers. Despite the benefits of EBL, efforts to achieving very high (> 20) aspect ratio structures requires non-standard techniques to overcome issues such as collapse or distortion of the zones and maintaining vertical sidewalls. Methods to increase the effective height of the zones, such as multi-layered lithography and stacking of zone plates present several challenges, such as cost, low yield, and difficult alignment. In this work, we present a new fabrication method, using a single-step-exposure, to pattern both sides of a thin 100 nm membrane to increase the overall effective thickness of a zone plate. By overcoming some of the effects of beam broadening during the electron beam exposure, this process is able maintain provide high-resolution lithography, despite the interfacial membrane layer separating the two resist films. This technique has several advantages, including perfect alignment of the two layers, reduced lithography and fabrication steps, increased mechanical strength and lifetime, producing high-efficiency and resolution zone plates. In this work, double-layer zone plates have been fabricated with outer zone widths down to 25 nm. Results will be presented comparing double-layered zone plates with single-layer zone plates for efficiency and resolution.

The liquid-metal-jet technology has developed from prototypes into fully operational and stable X-ray tubes running in many labs over the world. Key applications include X-ray diffraction and scattering, but recently several publications have also shown very impressive X-ray computed tomography results using the liquid-metal-jet anode technology. Based on these developments of advanced electron optics, a new nanofocus x-ray tube is developed. The foundation of the new nanofocus x-ray tube is the advanced electron optics, combined with a tungsten coated diamond transmission target. The new nanofocus x-ray tube is designed to reach line-spacing resolution of 150 nm. The new nanofocus x-ray tube furthermore has the unique feature that it internally measures and reports the current spot size before each scan is stared – which is of course of great importance to understand the best achievable resolution. The presentation will include unique work done by various users using Excillum's Nanotube for nano CT and imaging of variety of organic and inorganic materials. The applications include imaging of computer chips for counterfeit, nanoCT of worms to study their locomotive mechanisms and nano CT of first Diatom and study of its shell and core.

Recently, progress has been achieved in implementing phase contrast tomography of soft biological tissues at laboratory sources.^1-4 This opens up novel opportunities for three-dimensional (3d) histology based on x-ray computed tomography (μ- and nanoCT) in direct vicinity of hospitals and biomedical research institutions. Combining novel x-ray generation and detection techniques with suitable phase reconstruction algorithms, 3d histology can be obtained even of unstained tissue of the central nervous system, as shown for example for biopsies and autopsies of human cerebellum.^{5, 6} Depending on the setups, in particular source, detector, and geometric parameters, laboratory-based tomography can be implemented at very different sizes and length scales. In the present work, we investigate to which extent 3d histology of neuronal tissue can take advantage of cone-beam geometry at high magnification M using a nanofocus x-ray source (Excillum AB) with a minimum spot size of 300 nm, in combination with a single-photon counting camera. Tightly approaching the source spot with the biopsy punch, we achieve high M of ≈ 10¹-10², high flux density and can exploit the superior efficiency of this detector technology. Results are compared with those obtained at a microfocus rotating-anode x-ray tomography setup equipped with a high resolution detector, i.e. an low-M geometry.

Ancient remains from humans, animals and plants hold valuable information about our history. X-ray imaging methods are often, because of their non-destructive nature, used in the analysis of such samples. The classical x-ray imaging methods, radiography and computed tomography (CT), are based on absorption, which works well for radiodense structures like bone, but gives limited contrast for textiles and soft tissues, which exhibit high x-ray transmission. Destructive methods, such as classical histology, have historically been used for analysing ancient soft tissue but the extent to which it is used today is limited because of the fragility and value of many ancient samples. For detailed, non-destructive analysis of ancient biological samples, we instead propose x-ray phase-contrast CT, which like conventional CT gives volume data but with the possibility of better resolution through the detection of phase shift. Using laboratory x-ray sources, we here demonstrate the capabilities of phase-contrast tomography of dried biological samples. Virtual histological analysis of a mummified human hand from ancient Egypt is performed, revealing remains of adipose cells in situ, which would not be possible with classical histology. For higher resolution, a lab-based nano-CT arrangement based on a nanofocus transmission x-ray source is presented. With an x-ray emission spot of 300 nm the system shows potential for sub-micronresolution 3D imaging. For characterisation of the performance of phase-contrast imaging of dried samples a piece of wood is imaged. Finally, we present the first phase-contrast CT data from our nano-CT system, acquired of the dried head of a bee.

Zone-plate-based soft x-ray microscopes operating in the water window allow high-resolution and high-contrast imaging of intact cells in their near-native state. Laboratory-source-based x-ray microscopes are an important complement to the accelerator-based instruments, providing high accessibility and allowing close integration with other cell-biological techniques. Here we present recent biological applications using the Stockholm laboratory water-window x-ray microscope, which is based on a liquid-nitrogen-jet laser-plasma source. Technical improvements to the microscope in the last few years have resulted in increased x-ray flux at the sample and significantly improved stability and reliability. In addition to this, vibrations in key components have been measured, analyzed and reduced to improve the resolution to 25 nm half-period. The biological applications include monitoring the development of carbon-dense vesicles in starving human embryonic kidney cells (HEK293T), imaging the interaction between natural killer (NK) cells and HEK293T target cells, and most recently studying a newly discovered giant DNA virus and the process of viral replication inside a host amoeba. All biological imaging was done on cryo-frozen hydrated samples in 2D and in some cases 3D.

Optical coherence tomography (OCT) is an established method for non-invasive cross-sectional imaging of biological samples using visible and near infrared light. The axial resolution of OCT only depends on the coherence length l_c∝λ_0^2/Δλ_FWHM, with the central wavelength λ_0 and the spectral width Δλ_FWHM of the light source. For OCT, the axial resolution is in the range of a few micrometers. XUV coherence tomography (XCT) extends OCT into the extreme ultraviolet range. The significant reduction of the coherence length of a broadband XUV source allows nanoscale axial resolution. The usable spectral bandwidth in XCT is mainly limited by absorption edges of the sample under investigation. For example, the so-called silicon transmission window allows cross-sectional imaging of silicon-based samples like semiconductors. A laboratory-based XCT setup has been implemented by using XUV radiation from a laser-driven high-harmonic source. By averaging harmonic combs generated by different fundamental wavelengths, a quasi-supercontinuous spectrum, which is well-suited for XCT, is generated. The radiation is focused onto the sample and the reflected radiation is recorded. Interferences due to reflections at structures in different depths result in a modulated spectra that can be used to reconstruct the axial structure of the sample. Experimentally, we achieve an axial resolution of 24 nm. In the XUV range, focusing with high numerical aperture (NA) is extremely expensive. Therefore, XCT uses low-NA optics, which limits the lateral resolution to the micrometer range. A combination of XCT with coherent diffraction imaging would provide improved lateral resolution. We present first results a proof-of-concept experiment at a synchrotron source.

New instruments and methods for nanoimaging with the use of a compact laser plasma soft X-ray source are presented. The source is based on a double-stream gas puff target irradiated with nanosecond laser pulses from a Nd:YAG laser. Three imaging instruments, operating in the soft X-ray ‘water window’ range, namely two soft X-ray transmission microscopes and a soft X-ray contact microscope, have been developed. The transmission microscopes are based on grazing incidence Wolter type or diffractive Fresnel type optics. Application of these instruments for nanoimaging of hydrated and dry biological samples is presented. A new method for X-ray nanoimaging based on optical coherence tomography (OCT) technique using broad-band soft X-ray emission from the laser plasma source is also demonstrated.