Development Of X-ray Optics Research Articles

Automatic marker-based alignment method for a nano-resolution full-field transmission X-ray microscope

Driven by the development of X-ray optics, the spatial resolution of the full-field transmission X-ray microscope (TXM) has reached tens of nanometers and plays an important role in promoting the development of biomedicine and materials science. However, due to the thermal drift and the radial/axial motion error of the rotation stage, TXM computed tomography (CT) data are often associated with random image jitter errors along the horizontal and vertical directions during CT measurement. A nano-resolution 3D structure information reconstruction is almost impossible without a prior appropriate alignment process. To solve this problem, a fully automatic gold particle marker-based alignment approach without human intervention was proposed in this study. It can automatically detect, isolate, and register gold particles for projection image alignment with high efficiency and accuracy, facilitating a high-quality tomographic reconstruction. Simulated and experimental results confirmed the reliability and robustness of this method.

Femtosecond-Terawatt Hard X-Ray Pulse Generation with Chirped Pulse Amplification on a Free Electron Laser.

Advances of high intensity lasers have opened up the field of strong field physics and led to a broad range of technological applications. Recent x-ray laser sources and optics development makes it possible to obtain extremely high intensity and brightness at x-ray wavelengths. In this Letter, we present a system design that implements chirped pulse amplification for hard x-ray free electron lasers. Numerical modeling with realistic experimental parameters shows that near-transform-limit single-femtosecond hard x-ray laser pulses with peak power exceeding 1TW and brightness exceeding 4×10^{35} s^{-1} mm^{-2} mrad^{-2}0.1% bandwdith^{-1} can be consistently generated. Realization of such beam qualities is essential for establishing systematic and quantitative understanding of strong field x-ray physics and nonlinear x-ray optics phenomena.

Generation of highly mutually coherent hard-x-ray pulse pairs with an amplitude-splitting delay line

Beam splitters and delay lines are among the key building blocks of modern-day optical laser technologies. Progress in x-ray free electron laser source development and applications over the past decade is calling for their counter part operating in the Angstrom wavelength regime. Recent efforts in x-ray optics development have demonstrated relatively stable delay lines that most often adopted the division of wavefront approach for the beam splitting and recombination configuration. However, the two recombined beams have yet to achieve sufficient mutual coherence to enable applications such as interferometry, correlation spectroscopy, and nonlinear spectroscopy. We present the first experimental realization of the generation of highly mutually coherent pulse pairs using an amplitude-split delay line design based on transmission grating beam splitters and channel-cut crystal optic delay lines. The performance of the prototype system was analyzed in the context of x-ray coherent scattering and correlation spectroscopy, where we obtained nearly identical high-contrast speckle patterns from both branches. We show in addition the high level of dynamical stability during continuous delay scans, a capability essential for high sensitivity ultra-fast measurements.

DarpanX: A python package for modeling X-ray reflectivity of multilayer mirrors

Multilayer X-ray mirrors consist of a coating of a large number of alternate layers of high Z and low Z materials with a typical thickness of 10-100 Angstrom, on a suitable substrate. Such coatings play an important role in enhancing the reflectivity of X-ray mirrors by allowing reflections at angles much larger than the critical angle of X-ray reflection for the given materials. Coating with an equal thickness of each bilayer enhances the reflectivity at discrete energies, satisfying Bragg condition. However, by systematically varying the bilayer thickness in the multilayer stack, it is possible to design X-ray mirrors having enhanced reflectivity over a broad energy range. One of the most important applications of such a depth graded multilayer mirror is to realize hard X-ray telescopes for astronomical purposes. Design of such multilayer X-ray mirrors and their characterization with X-ray reflectivity measurements require appropriate software tools. We have initiated the development of hard X-ray optics for future Indian X-ray astronomical missions, and in this context, we have developed a program, DarpanX, to calculate X-ray reflectivity for single and multilayer mirrors. It can be used as a stand-alone tool for designing multilayer mirrors with required characteristics. But more importantly, it has been implemented as a local model for the popular X-ray spectral fitting program, XSPEC, and thus can be used for accurate fitting of the experimentally measured X-ray reflectivity data. DarpanX is implemented as a Python 3 module, and an API is provided to access the underlying algorithms. Here we present details of DarpanX implementation and its validation for different type multilayer structures. We also demonstrate the model fitting capability of DarpanX for experimental X-ray reflectivity measurements of single and multilayer samples.

In-situ observation of structural and chemical transitions in B4C based layered systems

In the context of multilayer based X-ray optics developments, thin layered systems of C/[Pt/B4C] multilayers and C/Pt/B4C/Cr stacks with variable cap layer thicknesses were deposited on Si wafers using DC magnetron sputtering. The samples were studied with in-situ X-ray reflectivity techniques during annealing in air up to temperatures of 300 °C. Simulated X-ray spectra of B4C/Cr reveal a considerable thickness loss of the B4C layer at elevated temperatures. The effect is amplified and accelerated when a thin Pt top layer is added but attenuated and slowed down by an additional C cap layer. Energy dispersive X-ray spectroscopy data indicate the overall depletion of B in samples after the annealing process. In-depth studies using X-ray photoelectron spectroscopy techniques show clear evidence of chemical modifications in the original B4C layer and confirm the structural modifications derived from the X-ray reflectivity data. This study demonstrates the catalyzing role of Pt in the degradation of B4C based layered structures in air and the potential protective function of C cap layers.

Development of channel-cut X-ray optics for laboratory small-angle X-ray scattering setups

Development of channel-cut X-ray optics for laboratory small-angle X-ray scattering setups

Full-shell x-ray optics development at NASA Marshall Space Flight Center.

NASA's Marshall Space Flight Center (MSFC) maintains an active research program toward the development of high-resolution, lightweight, grazing-incidence x-ray optics to serve the needs of future x-ray astronomy missions such as Lynx. MSFC development efforts include both direct fabrication (diamond turning and deterministic computer-controlled polishing) of mirror shells and replication of mirror shells (from figured, polished mandrels). Both techniques produce full-circumference monolithic (primary + secondary) shells that share the advantages of inherent stability, ease of assembly, and low production cost. However, to achieve high-angular resolution, MSFC is exploring significant technology advances needed to control sources of figure error including fabrication- and coating-induced stresses and mounting-induced distortions.

Automatic projection image registration for nanoscale X-ray tomographic reconstruction.

Novel developments in X-ray sources, optics and detectors have significantly advanced the capability of X-ray microscopy at the nanoscale. Depending on the imaging modality and the photon energy, state-of-the-art X-ray microscopes are routinely operated at a spatial resolution of tens of nanometres for hard X-rays or ∼10 nm for soft X-rays. The improvement in spatial resolution, however, has led to challenges in the tomographic reconstruction due to the fact that the imperfections of the mechanical system become clearly detectable in the projection images. Without proper registration of the projection images, a severe point spread function will be introduced into the tomographic reconstructions, causing the reduction of the three-dimensional (3D) spatial resolution as well as the enhancement of image artifacts. Here the development of a method that iteratively performs registration of the experimentally measured projection images to those that are numerically calculated by reprojecting the 3D matrix in the corresponding viewing angles is shown. Multiple algorithms are implemented to conduct the registration, which corrects the translational and/or the rotational errors. A sequence that offers a superior performance is presented and discussed. Going beyond the visual assessment of the reconstruction results, the morphological quantification of a battery electrode particle that has gone through substantial cycling is investigated. The results show that the presented method has led to a better quality tomographic reconstruction, which, subsequently, promotes the fidelity in the quantification of the sample morphology.

Simulated sample heating from a nanofocused X-ray beam.

Recent developments in synchrotron brilliance and X-ray optics are pushing the flux density in nanofocusing experiments to unprecedented levels, which increases the risk of different types of radiation damage. The effect of X-ray induced sample heating has been investigated using time-resolved and steady-state three-dimensional finite-element modelling of representative nanostructures. Simulations of a semiconductor nanowire indicate that the heat generated by X-ray absorption is efficiently transported within the nanowire, and that the temperature becomes homogeneous after about 5 ns. The most important channel for heat loss is conduction to the substrate, where the heat transfer coefficient and the interfacial area are limiting the heat transport. While convective heat transfer to air is significant, the thermal radiation is negligible. The steady-state average temperature in the nanowire is 8 K above room temperature at the reference parameters. In the absence of heat transfer to the substrate, the temperature increase at the same flux reaches 55 K in air and far beyond the melting temperature in vacuum. Reducing the size of the X-ray focus at constant flux only increases the maximum temperature marginally. These results suggest that the key strategy for reducing the X-ray induced heating is to improve the heat transfer to the surrounding.

Application of benchtop micro-XRF to geological materials

AbstractRecent developments in X-ray optics have allowed the development of a range of commercially available benchtop micro-XRF (μ-XRF) instruments that can produce X-ray spot sizes of 20–30 μm on the sample, allowing major- and trace-element analysis on a range of sample types and sizes with minimal sample preparation. Such instruments offer quantitative analysis using fundamental parameter based 'standardless' quantification algorithms. The accuracy and precision of this quantitative analysis on geological materials, and application of micro-XRF to wider geological problems is assessed using a single benchtop micro-XRF instrument. Quantitative analysis of internal reference materials and international standards shows that such instruments can provide highly reproducible data but that, for many silicate materials, standardless quantification is not accurate.Accuracy can be improved, however, by using a simple type-calibration against a reference material of similar matrix and composition. Qualitative analysis with micro-XRF can simplify and streamline sample characterization and processing for subsequent geochemical and isotopic analysis.

High-resolution non-destructive three-dimensional imaging of integrated circuits.

Modern nanoelectronics has advanced to a point at which it is impossible to image entire devices and their interconnections non-destructively because of their small feature sizes and the complex three-dimensional structures resulting from their integration on a chip. This metrology gap implies a lack of direct feedback between design and manufacturing processes, and hampers quality control during production, shipment and use. Here we demonstrate that X-ray ptychography-a high-resolution coherent diffractive imaging technique-can create three-dimensional images of integrated circuits of known and unknown designs with a lateral resolution in all directions down to 14.6 nanometres. We obtained detailed device geometries and corresponding elemental maps, and show how the devices are integrated with each other to form the chip. Our experiments represent a major advance in chip inspection and reverse engineering over the traditional destructive electron microscopy and ion milling techniques. Foreseeable developments in X-ray sources, optics and detectors, as well as adoption of an instrument geometry optimized for planar rather than cylindrical samples, could lead to a thousand-fold increase in efficiency, with concomitant reductions in scan times and voxel sizes.

3D X-ray ultra-microscopy of bone tissue.

We review the current X-ray techniques with 3D imaging capability at the nano-scale: transmission X-ray microscopy, ptychography and in-line phase nano-tomography. We further review the different ultra-structural features that have so far been resolved: the lacuno-canalicular network, collagen orientation, nano-scale mineralization and their use as basis for mechanical simulations. X-ray computed tomography at the micro-metric scale is increasingly considered as the reference technique in imaging of bone micro-structure. The trend has been to push towards increasingly higher resolution. Due to the difficulty of realizing optics in the hard X-ray regime, the magnification has mainly been due to the use of visible light optics and indirect detection of the X-rays, which limits the attainable resolution with respect to the wavelength of the visible light used in detection. Recent developments in X-ray optics and instrumentation have allowed to implement several types of methods that achieve imaging that is limited in resolution by the X-ray wavelength, thus enabling computed tomography at the nano-scale. We review here the X-ray techniques with 3D imaging capability at the nano-scale: transmission X-ray microscopy, ptychography and in-line phase nano-tomography. Further, we review the different ultra-structural features that have so far been resolved and the applications that have been reported: imaging of the lacuno-canalicular network, direct analysis of collagen orientation, analysis of mineralization on the nano-scale and use of 3D images at the nano-scale to drive mechanical simulations. Finally, we discuss the issue of going beyond qualitative description to quantification of ultra-structural features.

Picosecond-resolved X-ray absorption spectroscopy at low signal contrast using a hard X-ray streak camera.

A picosecond-resolving hard-X-ray streak camera has been in operation for several years at Sector 7 of the Advanced Photon Source (APS). Several upgrades have been implemented over the past few years to optimize integration into the beamline, reduce the timing jitter, and improve the signal-to-noise ratio. These include the development of X-ray optics for focusing the X-rays into the sample and the entrance slit of the streak camera, and measures to minimize the amount of laser light needed to generate the deflection-voltage ramp. For the latter, the photoconductive switch generating the deflection ramp was replaced with microwave power electronics. With these, the streak camera operates routinely at 88 MHz repetition rate, thus making it compatible with all of the APS fill patterns including use of all the X-rays in the 324-bunch mode. Sample data are shown to demonstrate the performance.

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 aperture's 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.

Bendable Kirkpatrick-Baez mirrors for the ALS micro-diffraction beamline 12.3.2: optimal tuning and alignment for multiple focusing geometries

Using an example of Kirkpatrick-Baez mirrors for the micro-diffraction beamline 12.3.2, we present the recent development of bendable x-ray optics and experimental techniques used for focusing of beams of soft and hard x-rays at the Advanced Light Source (ALS). We briefly review the nature of the bending and analyze a generalized solution of the bending equation for a side-profiled elliptically bent mirror substrate. A scaling rule is derived to understand a range of reliable tunability of the bendable optics for different applications (e.g., different focal distances and grazing incidence angles). Original design approaches are developed for assembly of bendable mirrors with minimal spurious stress and misalignment and for final precision compensation of the residual stress, substrate twist, and roll-off misalignment of the mirrors. Procedures used for optimal shaping and alignment of bendable optics at the ALS optical metrology laboratory are also briefly reviewed.

A Unique Rheology / SAXS Combination at DESY / Petra III

Progress in the development of synchrotron radiation sources, x-ray optics and detectors brings new possibilities in x-ray instrumentation. At the P10 beamline of PETRA III, a unique rheology / SAXS setup was successfully integrated and commissioned to gain new insight in the molecular arrangement of complex fluids and soft matter under shear conditions. The setup is based on an inverted Thermo Fisher Haake Mars II rheometer with a horizontal plate/plate or cone/plate geometry, specifically designed to be probed by a vertically deflected synchrotron X-ray beam. The main advantage of this kind of configuration is the unique possibility to scan the molecular arrangement of fluid matter along the shear gradient under a variety of shear conditions. In this way, very well defined experimental conditions can be provided and molecular arrangements that are otherwise inaccessible in plate / plate geometries can be directly examined.

Atomic spectrometry update-X-ray fluorescence spectrometry

This review offers the reader a wealth of information published between April 2010 and March 2011 concerning analytical endeavours using the range of conventional and hyphenated XRF techniques that encourage the user to ensure the potential for high spectral sensitivity and, where appropriate, spatial resolution is achieved. The development of advanced micro-beam set ups and new X-ray optics driven by third generation synchrotron based XRF techniques provide nano-imaging and the detection of nano-particles on single cells whilst TXRF coupled with GIXRF and GEXRF offer great potential for non-destructive investigations of thin layers on reflecting surfaces as well as depth profiling of implants. A new portable XRF system is described as an alternative for the traditionally applied K-X-ray fluorescence technology for in vivo measurements of lead in bone. Cryogenic cooling of heat sensitive biological samples is offered as a method to mitigate possible damage by the use of the more powerful μ-XRF technique. Other new preparation methods are also reviewed for the presentation and analysis of industrial, environmental and archaeological samples. One of the more unusual contributions available this year in the characterisation and use of industrial minerals showed that a semi-precious stone, amethyst, is more effective at shielding radiation than concrete.

Geometric phase kicks x rays down a new path

A small crystal distortion can dramatically translate the path of an x-ray beam, an effect that could be useful in the development of x-ray optics. The first impression one gets walking into an optics lab is of the endless maze of mirrors, lenses, etc., that can bend and guide the light along practically any desired path. Controlling x rays in the same manner, however, is much harder. In a paper appearing in Physical Review Letters, Yoshiki Kohmura, Kei Sawada, and Tetsuya Ishikawa at the SPring-8 synchrotron in Hyogo, Japan, show they can displace an x-ray beam propagating inside a crystal by a drastic amount - of order a millimeter - by deforming a single crystal less than 100 nanometers. They argue that the displacement arises from a geometric, or Berry, phase picked up by the waves constituting the x ray, an effect predicted several years ago. Experimentally, much remains to be done towards a full demonstration of the geometric-phase effect on the beam propagation. This statement is not meant to be derogatory - the experiments are challenging - but rather to stimulate further work in precision x-ray optics and, at the same time, investigate further what could be a toymore » model for many other fields of physics. Berry phases appear in many contexts of physics, including quantum systems, classical oscillators, and classical wave-propagating media. In the 1980s, Michael Berry observed that a quantum system, which is described by multiple parameters, picks up a phase beyond that of its dynamical evolution if the parameters are changed slowly along a closed loop in the parameter space (where each axis represents one parameter). This additional phase depends only on the geometrical properties of the loop. In particular, the Berry phase does not depend on the time it takes to traverse the loop, as long as it is done sufficiently slowly (adiabatically). The classic example is the polarization of a light beam as it is transmitted through a twisted optical fiber. Geometric phases are closely related to another ubiquitous concept - that of avoided crossings. The term 'avoided crossings' refers to energy levels in spectroscopy that rise or fall under the influence of an external field, but the concept applies generally to interacting parameter-dependent oscillatory modes, or wave modes in a parameter-dependent medium. As parameters are varied, and two modes become similar (say, they approach the same frequency), oscillatory averaging of the interaction no longer applies. Because the modes are coupled, they can no longer be degenerate and they repel each other by splitting into two coupled-wave modes with oppositely phased contributions from the original modes.« less

A compact soft X-ray microscope using an electrode-less Z-pinch source

Soft X-rays (< 1Kev) are of medical interest both for imaging and microdosimetry applications. X-ray sources at this low energy present a technological challenge. Synchrotrons, while very powerful and flexible, are enormously expensive national research facilities. Conventional X-ray sources based on electron bombardment can be compact and inexpensive, but low x-ray production efficiencies at low electron energies restrict this approach to very low power applications. Laser-based sources tend to be expensive and unreliable. Energetiq Technology, Inc. (Woburn, MA, USA) markets a 92 eV, 10W(2pi sr) electrode-less Z-pinch source developed for advanced semiconductor lithography. A modified version of this commercial product has produced 400 mW at 430 eV (2pi sr), appropriate for water window soft X-ray microscopy. The US NIH has funded Energetiq to design and construct a demonstration microscope using this source, coupled to a condenser optic, as the illumination system. The design of the condenser optic matches the unique characteristics of the source to the illumination requirements of the microscope, which is otherwise a conventional design. A separate program is underway to develop a microbeam system, in conjunction with the RARAF facility at Columbia University, NY, USA. The objective is to develop a focused, sub-micron beam capable of delivering > 1 Gy/second to the nucleus of a living cell. While most facilities of this type are coupled to a large and expensive particle accelerator, the Z-pinch X-ray source enables a compact, stand-alone design suitable to a small laboratory. The major technical issues in this system involve development of suitable focusing X-ray optics. Current status of these programs will be reported. (Supported by NIH grants 5R44RR022488-03 and 5R44RR023753-03)

High energy X-ray micro-optics

A tremendous progress in X-ray optics development was made in the past decade. Progress has been driven by the unique properties of X-ray beams produced by third generation synchrotron sources. The very low emittance coupled with high brilliance allows one to develop efficient focusing devices for new X-ray microscopy techniques. This article provides an overview of the state-of-the-art in micro-focusing optics and methods for hard X-rays. The main emphasis is put on those methods which aim to produce submicron and nanometer resolution. These methods fall into three broad categories: reflective, refractive and diffractive optics. The basic principles and recent achievements are discussed for all optical devices. To cite this article: A. Snigirev, I. Snigireva, C. R. Physique 9 (2008).