This PDF file contains the front matter associated with SPIE Proceedings Volume 12240 including the Title Page, Copywrite information, and Table of Contents.

The ESRF X-ray Optics Group is in the process of commissioning of a new Compact Multilayer Coating System (CMCS). With the arrival of the new ESRF Extremely Brilliant Source (EBS), many beamlines operate with smaller beams that require shorter but more precise optical elements. The existing Large Multilayer Coating System (LMCS) can coat multilayer (ML) optics up to 1 m long but is not optimized to deal with very short optics. Consequently, a new machine was designed and built that provides better accuracy to cope with smaller mirrors and tighter tolerances. The CMCS will also be employed to correct figure errors using differential deposition techniques. Similar to the LMCS, the CMCS is based on non-reactive magnetron sputtering. The machine is equipped with 4 circular cathodes. A linear substrate motion will enable coatings up to 300 mm long and 80 mm wide. This work will describe the basic concept of the machine and will provide an overview of the operation conditions. It will be complemented by initial results obtained during the commissioning period.

The fine alignment of X-ray nano-focusing optics, such as Kirkpatrick-Baez (KB) mirrors, depends strongly on the ability to diagnose the X-ray beam at the focus position. Despite conventional diagnostics techniques (e.g. knife-edge) allowing the measurement of the beam profile with sub-micrometer resolution, they may yield poor accuracy for beams with sizes under 100 nm. With nanometer-resolution phase-recovering techniques like ptychography, information about optical aberrations can be obtained experimentally in the complex-valued wavefront. In this work, we use wave-propagation simulations with Synchrotron Radiation Workshop (SRW) to model the CARNAÚBA beamline at Sirius. The beam phase at the KB mirrors exit pupil is decomposed in terms of Zernike rectangular polynomials. The relevant degrees of freedom (DOF) of the mirrors are scanned, allowing the correlation of the Zernike coefficients with the beam profile at focus. Therefore, the aberrations are classified and quantified for each mirror’s DOF, and alignment tolerances are obtained. We find that each DOF can be described by a unique combination of only three Zernike terms. Additionally, a database with the first 15 Zernike coefficients is created by simulating random alignment states and used to train a simple fully-connected neural network. The neural network was able to determine the alignment states of unknown samples with errors below 3%. The combination of Zernike polynomials and neural networks could potentially lead to single-iteration alignment of KB mirrors using wavefront sensing techniques as a diagnostic tool.

A Kirkpatrick-Baez (KB) mirror is a reflective focusing device that sequentially positions a pair of crossed mirrors in a grazing-incidence setup. Typically, this type of device offers a relatively long working distance of 20 mm or longer, which allows specimens to be installed in various configurations. However, there is a tradeoff between the long working distance and both the numerical aperture and demagnification factor, resulting in drawbacks for KB mirrors for a sub-micron focus size in a soft-X-ray region. This research explores an ultrashort KB mirror composed of 2- and 8-mm-long mirrors with focal lengths of 2 and 8 mm, respectively. Its demagnification is designed to be up to 10000 and its focus size can theoretically be below 50 nm at a photon energy of 1 keV. To demonstrate an X-ray nanoprobe based on this focusing device for X-ray microscopy, the low energy X-ray fluorescence (LEXRF) technique is incorporated into the focusing system. The aim of this LEXRF system is to observe light elements in biological specimens. After X-ray fluorescence yields were estimated, the experimental setup was examined for a forward- and side-scattering configuration. Preliminary studies examined the fluorescence detector performance and the fluorescence detection of biological and pharmaceutical specimens in the traditional backscattering configuration. Compared with diffractive focusing devices, which condense approximately 10% of the incident X-rays, the reflective ultrashort KB mirror can benefit LEXRF by more efficiently collecting X-rays to its nanoprobe, thus enhancing the fluorescence signals from specimens.

Imaging of x-rays with energies >15 keV is a necessity for several applications in high-energy density physics experiments. Multilayer-coated, Wolter-type glancing-incidence optics offer higher collection efficiency than pinhole cameras or Kirkpatrick-Baez style mirrors, and can achieve spatial resolution of 10-100um over 1-8 mm fields of view with throughput ~ 1-10%. Designing the multilayer coating is a complex optimization problem, involving multiple tradeoffs. A narrow energy bandwidth (~1keV) is desirable to exclude background, but a broad angular acceptance is desirable for the optic to image a large field (~1-8 mm). A Wolter optic’s net reflectivity is two-bounce R² = R₁*R₂ for a wide range of pairs of incidence angles θ₁, θ ₂. In addition, the multilayer coating can be modified in several ways, such as varying the period thickness through the stack, and along the length of the optic. Parallelized searches using ordinary gradient-descent and Markov-Chain Monte Carlo (MCMC) have been applied to design an optic to image Z-pinch plasmas on the Z Machine at Sandia National Laboratories. Methods are tested to design an appropriate cost function for this search, and to reduce computational cost to search the parameter space efficiently.

Applications such as counterfeit identification, quality control, and non-destructive material identification benefit from improved spatial and compositional analysis. X-ray Computed Tomography is used in these applications but is limited by the X-ray focal spot size and the lack of energy-resolved data. Recently developed hyperspectral X-ray detectors estimate photon energy, which enables composition analysis but lacks spatial resolution. Moving beyond bulk homogeneous transmission anodes toward multi-metal patterned anodes enables improvements in spatial resolution and signal-to-noise ratios in these hyperspectral X-ray imaging systems. We aim to design and fabricate transmission anodes that facilitate confirmation of previous simulation results. These anodes are fabricated on diamond substrates with conventional photolithography and metal deposition processes. The final transmission anode design consists of a cluster of three disjoint metal bumps selected from molybdenum, silver, samarium, tungsten, and gold. These metals are chosen for their k-lines, which are positioned within distinct energy intervals of interest and are readily available in standard clean rooms. The diamond substrate is chosen for its high thermal conductivity and high transmittance of X-rays. The feature size of the metal bumps is chosen such that the cluster is smaller than the 100 µm diameter of the impinging electron beam in the X-ray tube. This effectively shrinks the X-ray focal spot in the selected energy bands. Once fabricated, our transmission anode is packaged in a stainless-steel holder that can be retrofitted into our existing X-ray tube. Innovations in anode design enable an inexpensive and simple method to improve existing X-ray imaging systems.

The spontaneous polarization of pyroelectric crystal is utilized to X-ray emission in low pressure gas of ~1 Pa, which has a potential as a future in-situ X-ray source with small size, light weight, and low electric power consumption. The pyroelectric X-ray production still has problems as its intensity and reproducibility because the mechanism of electron production is still an open question. We have experimentally and numerically evaluated pyroelectric X-ray generation relevant to electric discharges around the pyroelectric crystal with various sizes of target support and target with/without a needle. Three kinds of electric discharge, between crystal top and metallic target (CT-MT discharge), between crystal top and crystal bottom (CT-CB discharge), and along with crystal surface (CS discharge), were observed. The CT-MT discharge was measured by the 1 cm × 5 cm target support or target with a needle, which induced irregular X-ray increases. X-ray intensity became reproducible, but not so large when the CT-MT discharges were measured. The CTCB and CS discharges were active for the large target plates. These two discharges occur irregularly, resulting low reproducibility. While reduction of crystal potential by the CS discharge was not large, the CT-CB discharge stopped Xray emission. When the CT-CB was not measured, the X-ray intensity became large. Calculation results of electric fields at around the crystal supported the experimental results, which implied that selection of appropriate target support is one of important factors to obtain large and reproducible X-ray intensity by the pyroelectric X-ray generation.

We suggest a new method of making ultra-low blaze angle gratings for synchrotron application. The method is based on reduction of the blaze angle of a master grating by replication followed by a plasma etch. A master blazed grating with a relatively large blaze angle is fabricated by anisotropic wet etching of a Si single crystal substrate. The surface of the master grating is replicated by a polymer material on top of a quartz substrate by nanoimprinting and then transferred into quartz by a plasma etch. Then a 2 ^nd nanoimprint step is applied to transfer the saw-tooth surface into a resist layer on top of a Si grating substrate. The plasma etch through the patterned resist layer provides transfer of the grooves into the Si substrate and results in reduction of the blaze angle due to the difference in etch rates of the resist and Si. We investigated the impact of the replication process on the groove shape, facet surface roughness, and diffraction efficiency of the fabricated 200 lines/mm low blaze angle grating.

Oscillating microelectromechanical systems (MEMS) devices can manipulate synchrotron x-ray beams at ultrafast rates. By selectively diffracting x-rays, these devices can “pick” or even “slice” x-ray pulses from a beam; diffractive time windows less than 1 ns have been demonstrated. Here we demonstrate the use of MEMS devices to produce modulated x-ray beams with a high x-ray throughput that modify the timing structure of a synchrotron beam, which can be applied to perform time-resolved x-ray diffraction experiments.

We present fabrication and characterization of ultra-thin with ∼15-25 µm thick (300 µm in diameter) diamond single-crystal membranes for various applications in synchrotron radiation sources, x-ray free-electron lasers (XFELs), and XFEL oscillators. Ultra-thin diamond single-crystal membranes are fabricated using laser ablation techniques with ultra-short (femtosecond) laser pulses. Here, we report optimizing the laser ablation parameters such as fluence, power, repetition rate, pulse length, and wavelengths. The crystal quality of the ultra-thin diamond membranes has been characterized by x-ray rocking curve imaging (RCI) of the crystal before and after laser ablation and subsequent high-temperature annealing.

Magnetic smart materials (MSMs) offer an alternative to the typical piezo-electric actuators that are currently being used to control X-ray optics on beam lines. MSMs combined with an overcoating of a magnetic hard material means a deformable mirror whose non-reflecting side is coated with a MSM plus magnetic hard overcoat can work in a power-off mode. The process works by using an electromagnet (EM) to impose a magnetic field in the bilayer of MSM and magnetic hard overcoat. Once the EM is turned off, the mirror settles to a new shape within minutes. The new shape can then remain intact for days. Since the EM is not fixed to the mirror, the exact placement of the magnetic field can be adjusted by relocating the EM. This feature allows for fine-scale adjustments and avoids the “dead pixel” replacement problem common with piezo patches that are attached to the mirror. We will give an overview and a progress report.

We describe details of a recent deep upgrade of the MicroMap-570 interferometric microscope available at the Advanced Light Source X-Ray Optics Laboratory. The upgrade has included an improvement of the microscope optical sensor and data acquisition software, design and implementation of automated optic alignment and microscope translation systems, and development of a specialized software for data processing in the spatial frequency domain. With the upgraded microscope, we are now capable for automated (remoted) measurements with large x-ray optics and optical systems. The results of experimental evaluation of the upgraded microscope performance and calibration of its instrument transfer function are also discussed. Because the same already obsolete MicroMap-570 microscopes have been used for years at other metrology laboratories at the x-ray facilities around the globe, we believe that our experience on upgrade of the microscope describe in detail in the present paper is broadly interesting and useful.

The reliability of the instrument transfer function (ITF) calibration technique based on binary pseudo-random array (BPRA) standards is investigated and demonstrated in application to interferometric microscopes. We demonstrate the linearity of the calibration (that is, independence of the ITF calibration on the standards root-mean-square roughness) via comparison of the ITF measurements with a number of artifacts with the etched depth varying from 30 nm to 120 nm. We also show that the calibration does not depend on the surface reflectivity, at least in the range between ~36% and ~80%. The criteria for selection of the geometrical parameters of the BPRA standard design appropriate for a particular interferometric microscope arrangement (including optical magnification), as well as the data acquisition and analysis procedures for different applications are also discussed.

We report on recent work towards improving interference microscopy metrology of variable-line-spacing (VLS) x-ray diffraction gratings through a combination of techniques: image reconstruction to correct for distortion and blurring, multi-image super-resolution data acquisition to increase resolution beyond the single-image limit, and image stitching to increase the measurement area. Here, we concentrate on precision characterization and correction for lens distortion (aka geometrical distortion) and provide precise measurements of the effective image pixel distribution. We present and analyze the results of geometrical distortion measurements performed with test samples, including traditional checkerboard test artifacts and binary pseudo-random array (BPRA) standards patterned with two-dimensional uniformly redundant arrays (URA). The URA BPRA standards are also useful for measurement of the instrument transfer function (ITF), a measure of the optical aberrations and limited lateral resolution of the instrument. We also outline other essential elements and the next steps of the project on development of so-called super-resolution interference microscopy, enabling more precise measurements of VLS groove density than previously possible. The global aim of this project is to integrate our metrology technique into the manufacture of high-resolution x-ray gratings.

At 4th-generation synchrotron nanoprobes with optimized photon density, focusing optics systems often require mirrors arrangements with high demagnification factors to achieve diffraction-limited beam sizes (∠ 100 nm) and still high photon flux. All the components’ contributions to the surface error must be at the same level (a few nanometers) and angular stability (lower than 10 nrad RMS) becomes a bottleneck issue. Therefore, the design of ultra-stable mirror mechanics has to follow a systems perspective, where precision engineering, metrology and alignment strategies are considered simultaneously. For the latest design at Sirius/LNLS, an exactly-constrained KB set with minimum number of adjustment degrees for increased stiffness and stability was also bounded by an alignment error budget in the order of tens of microns by construction, pushing metrology limits during alignment and validation phases. This work presents a two-phase strategy for metrology-assisted assembly and figure validation of elliptical mirror sets, starting at a Fizeau Interferometer system (FZI) and finishing at a Coordinate Measuring Machine (CMM). The first phase validates surface quality by scanning mirror position and automatically realigning interferometry fringe patterns, while pixel-level stitching techniques are employed to characterize the surface error over the mirror’s length. The stitching algorithm includes self-calibration of lens errors and uses multiple CPU cores for expedite processing. The second phase consists of fiducializing the elliptical figures of each mirror into their own substrates and assembling both mirrors with regard to each other by using a least-squares fit of the center and rotation angle of each fixed ellipse, obtained from the manufacturer’s documentation, and confirmed at the first phase. This workflow was applied and demonstrated at an ultra-stable exactly-constrained KB system, reaching sufficient alignment accuracy.

For application in the soft X-ray region, focusing mirrors having a steep shape with small radii of curvature of several tens to hundreds of millimeters and a deep sag of a few millimeters have recently been designed. These mirrors are difficult to fabricate with high accuracy owing to the challenges in figure measurement. In this study, we demonstrate the surface measurement of a flat substrate and soft X-ray Wolter mirror using a tactile profiler. The comparison with a stitching interferometry image of the flat substrate showed an agreement of mid- to high-spatial-frequency errors. The tactile measurement of the Wolter mirror exhibited a root-mean-square figure error of 2.49 nm.

A coded-mask-based X-ray wavefront sensing technique was recently developed at the Advanced Photon Source, aiming for the ultimate phase sensitivity, spatial resolution and high speed using deep-learning-based analysis. It is a versatile tool capable of single-shot reference-free measurements and scanning mode for the best resolution and noise robustness. This work extends its application in at-wavelength metrology to achieve variable-resolution analysis when combined with a short-focal-length focusing optic. We showcase the complete characterization of beryllium refractive lenses using the coded-mask-based method in a collimated-beam setup and a divergent-beam setup with large geometric magnifications. The collimated-beam measurement provides the lens thickness error over the entire optical aperture down to a micron spatial resolution. On the other hand, wavefront sensing with the divergent beam can provide detailed local information of the sample with a few tens of nanometer spatial resolution, ideal for investigating lens defects.

The X-ray beam expander for advanced synchrotron sources based on Si planar compound parabolic refractive lenses (CRLs) with aperture of 10 micron was considered. The lenses were fabricated by using MEMS technologies including a lithography and a deep silicon etching for CRLs pattern generation in the hard mask and the pattern transfer into silicon wafer down to 40 μm, respectively. To minimize an influence of the manufacturing errors on the CRLs optical properties special control and metrology of the geometrical parameters of the lenses were proposed and applied. The errors influence on the X-ray beam expander parameters was considered theoretically and the related computer simulations were performed.

While modern x-ray microscopes at synchrotron radiation sources and free-electron lasers require x-ray optics of highest quality, these optics often show aberrations due to limitations in fabrication technology. Based on ptychography, we determine these aberrations and fabricate tailor made refractive phase plates to compensate for them. Starting from the aberrated optics, diffraction-limited beams can be generated by introducing the phase plate behind these optics. In addition, the wavefront can be modified to generate custom beams for special needs, such as donut-shaped beams with orbital angular momentum or for structured-illumination microscopy. The nanofocused beam can be engineered in shape and phase by introducing specially designed phase plates. We introduce a general scheme for wavefront engineering and illustrate it with a numerical example.

The Linac Coherent Light Source (LCLS) is being upgraded to the high repetition rate (up to 1 MHz) mode using cryogenic modules. As the key optical element at the X-ray Pump-probe (XPP) beamline, the goal of the large offset double-crystal monochromator (LODCM) for the High Energy (HE) upgrade is to maintain its x-ray beam multiplexing capability at higher average beam power (up to 200W) for the whole hard x-ray operating range of 6-25 keV. The upgraded LODCM system will use an upstream diamond transmission grating to achieve high power beam multiplexing. It will enable the 0^th order 'transmission’ from the grating to pass through the XPP hutch. The +1^st order beam, which contains about 20% power of the incident beam of the grating, will be monochromatized at the 1^st crystal position, then directed to XPP experiments at the 2^nd crystal position. Both crystal positions will provide 111 and 220 Si crystals. The 1 ^st crystals need to be cooled by Liquide Nitrogen to minimize their thermal deformation under heat load. The second crystals will be controlled close to ambient temperature. The temperature difference between the two crystals leads to a lattice constant mismatch. The corresponding difference in Bragg angles is utilized to compensate the angle between the 1 ^st order beam and 0^th order beam (initial beam propagation axis) from the grating splitter, making it possible to maintain the propagation direction of the monochromatized beam exiting the LODCM parallel to the 0^th order incoming beam.