This PDF file contains the front matter associated with SPIE Proceedings Volume 11108, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists

Focusing X-ray free-electron lasers (XFELs) is very important for producing ultra-intense X-ray nanoprobes. We have developed a system based on multilayer Kirkpatrick–Baez (KB) mirrors to focus XFELs to 10 nm or less at the SPring-8 Angstrom Compact free-electron LAser (SACLA) facility. The mirror optics in the system are designed with a large NA of greater than 0.01 to produce a diffraction-limited size of 6 nm at 9 keV. We constructed a precise X-ray grating interferometer based on the Talbot effect, and succeeded in fabricating near-perfect focusing mirrors with wavefront aberrations of λ/4. However, strict error tolerances for mirror alignment can prevent sub-10 nm focusing. Errors of perpendicularity, incident angle, and astigmatism cause aberration on the focusing wavefront and characteristically change the beam shape. In particular, the required accuracy of the incident angle is 500 nrad. Due to shot-by-shot variations in the XFEL beam position and vibration of the optics, a single-shot diagnosis of beam shape is essential to align the mirrors quickly and accurately. By improving the method proposed by Sikorski et al. at the Stanford Linear Accelerator Center (SLAC), National Accelerator Laboratory, we propose a nanobeam diagnosis method based on the speckle pattern observed under coherent scattering. Computer simulation revealed that speckle size and beam size are inversely proportional. Platinum particles with a diameter of 2 nm were prepared and irradiated with X-rays to obtain a speckle pattern. Our experimental results demonstrate the successful estimation of beam shape and the alignment of all mirrors with the required accuracies.

Ellipsoidal mirrors are promising focusing devices for soft x-rays. Ellipsoidal mirrors were fabricated by our group using nickel electroforming, for which a precise master mandrel is required because the surface accuracy of the reflective surface is limited by the mandrel. The aim of this study was to develop a processing method for correcting the surface figure error of the mandrel with high spatial resolution. This method is based on loose abrasive machining with organic abrasive slurry and a small rotating tool. We call this method “Organic Abrasive Machining” (OAM). The organic particle materials are acrylic resin or urethane resin, which have excellent characteristics that include such as high dispersion, low hardness, and high washability. In the presentation, we will report the basic performance of the newly developed OAM system, including such as a stationary spot profile, surface roughness, and long-term stability of the removal rate during figure corrections. Spatial wavelength of 100 m on a rod lens was achieved, which means that the OAM could be applied for deterministic figure correction of the surface waviness of ellipsoidal mirrors.

This paper presents the designs and simulations of twin Wolter mirrors for focusing and imaging experiments with soft Xray free electron lasers. Wave-optical simulations at a photon energy of 100 eV indicate that the designed focusing Wolter mirror focuses soft X-ray beams to a 300 nm × 200 nm spot with an acceptable rotational error of 1.7 mrad × 1.4 mrad and that the objective Wolter mirror, which receives the beam that passes through the focusing Wolter mirror and a sample, forms bright-field images with a spatial resolution of 140 nm × 140 nm. The focusing Wolter mirror enables long-term experiments with high stability, and the objective Wolter mirror is applicable to imaging-before-destruction.

In synchrotron radiation facilities and X-ray free electron laser facilities, beam size adjustment depending on the experimental condition and the sample size is necessary. Various types of X-ray focusing optical systems are used for beam conditioning. However, they are specially designed for specific purposes and optical parameters such as numerical aperture (NA) and focal length are fixed. This lack of adaptability has limited application targets. In this research, we are developing X-ray adaptive focusing optical system which can control the beam size without moving the position of the focus. The optical system consists of two deformable mirrors in one dimension. In order to control the focused beam size, the NA can be controlled by deforming the mirror shapes from concave to convex. When we want to achieve large NA, deform the upstream mirror into convex shape and spread the beam. The downstream mirror receives X-ray with full aperture and X-ray is focused at focal point. When we want to achieve small NA, deform the upstream mirror into a concave shape and narrow down the reflection area of downstream mirror. NA becomes small because reflection area of downstream mirror becomes narrow. One dimensional focusing experiment of large NA adaptive optical system was performed at SPring-8 as a demonstration. A focused beam with an intensity profile having a full width at half maximum of 134 nm was achieved at 10 keV. This is close to ideal beam size. In my presentation, I will explain details of adaptive focusing optics and deformable mirrors.

Ellipsoidal mirrors are ideal focusing optics for soft x-rays because of advantages that include high numerical aperture, high efficiency, and no chromatic aberrations. Shape accuracy of nanometer order is required on the internal surface of a mirror with a diameter of around 10 mm. Because of the difficulty of processing the internal surface, ellipsoidal mirrors are fabricated by replication of the shapes of master mandrels. In previous studies, a fabrication process was developed for x-ray ellipsoidal mirrors involving mandrel fabrication and nickel electroforming. 40-mm-long ellipsoidal mirrors were fabricated and a focused beam with full width at half maximum (FWHM) of 240 nm was obtained. For better focusing performance and expansion of the applicable energy range, we designed and fabricated a 120-mm-long ellipsoidal mirror from the master mandrel with a shape accuracy of 3.8 nm (root mean square). A focusing experiment was also performed at the synchrotron radiation facility, SPring-8 (BL25SU). A focused beam with FWHM of 1 μm was obtained.

Differential deposition techniques were applied to reduce the figure error of x-ray mirrors. Cr layers were sputtered on flat substrates that were moved with variable speed in front of a beam defining aperture. The required velocity profile was calculated using a deconvolution algorithm. The Cr thickness profiles were derived in two ways: directly, using x-ray reflectivity and indirectly, by measuring the surface figure before and after the deposition. After two iterations the mirror surface figure could be improved by almost one order of magnitude. This work will describe the experimental techniques and discuss the achieved accuracy. It will also address open questions such as layer stress, roughness evolution, and limitations of the available instrumentation.

We have used microelectromechanical systems (MEMS) to dynamically modulate synchrotron x-ray beams. By oscillating a small silicon crystal at 10s to 100s of kHz, we have demonstrated that the “time window” in which the Bragg condition is satisfied, and thus the time in which an x-ray pulse can be deflected by diffraction, can be significantly less than 1 ns. Here we discuss the optimization of x-ray optics to further improve device performance. We show that the time window can be reduced by matching the dispersion of a monochromator crystal to that of the MEMS crystal. We consider the case of an ideally perfect crystal and also treat the effects of strain and curvature, either of which broadens the crystal rocking curve and thus degrades the time window. A careful understanding of the effects of dispersion and x-ray wavelength produces time windows approaching the typical synchrotron pulse duration.

Continued advances of modern synchrotron light sources are pushing crystal-based X-ray optics, mainly monochromators and analyzers, to have unprecedented high resolution, with resolution towards sub-meV for inelastic X-ray scattering (IXS) and sub-10-meV for resonant IXS (RIXS) as examples, for spectroscopy and other applications. The Advanced Photon Source (APS) has been the center in the USA for designing, fabrication, and implementation of state-of-the-art crystal optics. In this presentation, we will introduce our recent pioneering work on: (1) Design and development of new non-dispersive nested channel-cut monochromators that are completely in-line monochromators with resolution from sub-meV to ~10 meV based on silicon, quartz and sapphire crystals in the medium-energy range, (2) development and deployment of novel flat quartz-based RIXS analyzers (combined with Motel mirrors) to achieve unprecedented resolution of ~3.9 meV at the Ir-L3 absorption edge (11.215 keV) with the unique capability of efficient polarization analyses, and (3) successful dicing and assembling of spherical quartz analyzers that also achieved sub-10-meV resolution for RIXS. We will particularly emphasize the applications of “unconventional” quartz and sapphire crystals in developing these optics. Compared with silicon or germanium that has only a few tens of Bragg reflections in the medium energy range (<16 keV), quartz and sapphire can provide hundreds to thousands of different Bragg reflections for making near-back-reflection analyzers with energies virtually at any atomic absorption edges or emission lines. The guidelines for dynamical-theory modeling, orienting, fabrication and characterization of quartz and sapphire will also be presented.

Elastically bent single crystal Laue case diffraction crystals provide interesting new opportunities for imaging and spectroscopy applications. The diffraction properties are well understood, however, the ability to easily model the diffracted beams hinders assessment of the focal, phase and energy dispersive properties needed for many applications. This work begins to collect the elements needed to ray trace diffracted beams within bent Laue crystals for the purpose of incorporation into other powerful ray tracing applications such as SHADOW. Specifically, we address the condition in a bent Laue crystal where a cylindrically bent Laue crystal will focus all the polychromatic diffracted beams at a single location when a specific asymmetry angle condition is met for a target x-ray energy – the so-called ‘magic condition’. The focal size of the beam can be minimized, but this condition also results in excellent energy dispersive properties. The conceptual and mathematical aspects of this interesting focusing and energy dispersive phenomenon is discussed.

The planning and construction of new and upgraded x-ray synchrotron light sources and free-electron lasers [1], in the last decade, has urged the need for advanced x-ray optics and promoted a rapid development of advanced software tools and packages for X-ray optics simulation and design. The focus of this development has evolved from individual optical components to start-to-end simulation packages (such as SRW [2]) integrating the computation of the source, optical elements, samples and the detection system. To take full advantage of the new sources, modern x-ray optical systems become more complex including e.g., adaptive optics whose performance heavily relies on the level of perfection of their mechanical, thermal and control systems. This successively demands the development of new simulation framework and software (such as OASYS [3]) to allow interoperability between different tools and physical models. A successful approach to the modern optical design requires not only the ability to integrate multiple optical components, but also the integration of different levels of simulation [4] including analytical formulas, numerical ray-tracing or wavefront propagation, and mutual coherence propagation. These simulations need to take into account the integration of the optical, mechanical and thermal properties of the system, as well as the prediction of the instrumental response at the experimental station to evaluate the overall quality of the optical layout or setup. Simulations could also be used to drive real control systems, by reverse processing of real-time data to interpolate the feedback signals. In this presentation, we will review the status of x-ray optics simulation with examples, and highlight future directions. [1] Eriksson, M., Van Der Veen, J. F., & Quitmann, C. J. Synchrotron Rad., 21, 837 (2014). [2] Chubar, O., Rakitin, M. S., Chen-Wiegart, Y.-C., Fluerasu, A., & Wiegart, L. Proc. SPIE, 10388, 1038811 (2017). [3] Rebuffi, L., & Sanchez del Rio, M. Proc. SPIE, 10388, 103880S (2017). [4] Shi, X., Reininger, R., Harder, R., & Haeffner, D. Proc. SPIE, 10388, 103880C (2017).

The design of beamlines for diffraction-limited storage rings light source (DLSR) requires the ability to simulate and optimize the performances of the photon transport schemes, as the brightness and coherence of the beam can rapidly be altered by optical, mechanical and thermal effects. Open source tools based on raytracing such as ShadowOUI/OASYS [1] have gained popularity in the community because of their time-tested reliability, their user-friendly interface and their flexibility, allowing to easily share designs and implement new capabilities (widgets) for analysis. While these tools offer fast and efficient computation for incoherent systems, only few extensions exist [2] to account for the coherent nature of the light produced by fourth generation light sources, or to quickly iterate the designs using other simulation frameworks [3] and discuss the performance trade-offs with the beamline scientists [4]. We have developed new tools to analyze wavefront based on optical path length, simulate the effect of misalignments [5] and thermal deformations, optimize adaptive optics shapes [6,7] to compensate them and devise optimal mirror profiles [8]. We have integrated these extensions as widgets for OASYS [9] and validated simulations results using experimental data based on wavefront sensor measurements, allowing us to refined tolerance specifications on mirror specifications, alignment and mechanical stability. These tools are now available to the x-ray community at large. References: [1] L. Rebuffi, M. Sanchez del Rio, "OASYS (OrAnge SYnchrotron Suite): an open-source graphical environment for x-ray virtual xperiments”, Proc. SPIE 10388, 103880S (2017) [2] X. Shi, R. Reininger, M. Sanchez del Rio, L. Assoufid, “A hybrid method for X-ray optics simulation: combining geometric ray-tracing and wavefront propagation”, J. Synchrotron Rad. 21, 669 (2014). DOI:10.1107/S160057751400650X [3] Wiegart, L., Rakitin, M., Zhang, Y., & Fluerasu, A. (2019). Towards the Simulation of Partially Coherent X-ray Scattering Experiments. In AIP Conference Proceedings (Vol. 2054, p. 060079). http://doi.org/10.1063/1.5084710 [4] Shi, X., Reininger, R., Harder, R., & Haeffner, D. (2017). X-ray optics simulation and beamline design for the APS upgrade. Advances in Computational Methods for X-Ray Optics IV, 10388, 12. http://doi.org/10.1117/12.2274571 [5] Wojdyla A., Bryant D., Cocco D., Dovillaire G., Warwick T., Rebuffi L., Idir M., Assoufid L., Goldberg K. A. (2018). Fine alignment of x-ray optics using wavefront sensor measurements. International Workshop on X-Ray Metrology. http://antoine.wojdyla.fr/assets/posters/iwxm2018.pdf [6] Alcock, S. G., Nistea, I.-T., Signorato, R., & Sawhney, K. (2019). Dynamic adaptive X-ray optics. Part I. Time-resolved optical metrology investigation of the bending behaviour of piezoelectric bimorph deformable X-ray mirrors. Journal of Synchrotron Radiation, 26(1), 36–44. http://doi.org/10.1107/S1600577518015953 [7] Ichii, Y., Okada, H., Nakamori, H., Ueda, A., Yamaguchi, H., Matsuyama, S., & Yamauchi, K. (2019). Development of a glue-free bimorph mirror for use in vacuum chambers. Review of Scientific Instruments, 90, 021702. http://doi.org/10.1063/1.5066105 [8] McKinney, W. R., Glossinger, J. M., Padmore, H. a., & Howells, M. R. (2009). Optical path function calculation for an incoming cylindrical wave. In Proc. of SPIE (Vol. 7448, pp. 744809-744809–8). http://doi.org/10.1117/12.828490 [9] https://github.com/oasys-als-kit/OASYS1-ALS-ShadowOui

Micro-focusing protein crystallography beamline BL45XU was remodeled using focusing mirrors and a slit as a secondary source. In the horizontal direction, two stage focusing was adopted and beam size was controlled by the slit and defocusing of 2nd mirror by changing the glancing angle. In the vertical direction, beam size was enlarged by defocusing by changing the glancing angle. Beam profile and photon flux through slit and mirror were estimated using a wave calculation, and compared with the measurements. We verified that beam size can be controlled using a slit and mirror defocusing from 5×5 to 50×50 μm², and measured photon flux agreed with estimation.

The interest in ultrafast time resolved spectrometry with soft x-rays considerably increased during the last decade mainly because of the development of new ultra-short pulse sources at large scale facilities, X-ray free electron lasers (XFELs) as well as laboratory scale facilities such as laser-produced plasma (LPP), high harmonics generators (HHG), gas jet isolated atto-second X-ray pulse generators (IPP), relativistic oscillating mirror HHG (RHHG) and time-resolved electron-beam micro-analyzers. Fast progress in all areas demonstrated the ability of modern instrumentation even in laboratories, to reach energy ranges of the so-called “water window” and beyond up to 1000 eV with a pulse duration down to several femto-seconds. In opposite to XFEL giants, emitting presently at photon energies up to 20 keV – 30 keV with tremendous power of several GWatt, laboratory sources emit several order of magnitude lower photon flux and need therefore extremely efficient optics for flux and temporal characteristics preservation. Unfortunately, solutions available in UV, such as conical gratings, are no longer applicable in the photon energy range above 200 eV.

Reflection zone plates (RZP) and 2-dimensional variable line spacing (VLS) gratings are serving as a combination of three functions in one optical element (reflection, energy dispersion and focusing). They were used for the development of different types of spectrometers and monochromators with femtosecond time resolution in the soft x-ray energy range. In this paper, we also suggest to combine two identical RZPs placed in opposite orders of diffraction (+1 and -1) for compensation of time elongation of fs soft X-ray pulses down to several fs.

Soft X-ray monochromator designers know very well the program, which M. Neviere developed in order to predict the diffraction efficiencies of reflection gratings by use of the rigorous differential method. Infact it is used frequently for the grating parameter optimisation.

Here a simple analytical equation is presented, which predicts for perfect grating profiles diffraction efficiencies, which correspond within 10% to the results with the more rigorous Neviere approach. This empirical equation, which is based on plausible assumptions, facilitates very much systematic studies, which can then easily be presented in the form of isoefficiency maps, which are valid rather generally and which can be further evaluated in simple image analysis programs. Infact such maps will allow one to identify the optimum grating parameters for a given application in a glimpse.

Large angular dispersion rate of the diffraction gratings is essential for the high spectral resolution of the grating spectrometers. The greatest challenge is achieving the desired performance of the diffraction gratings at short wavelengths. Here we show that crystals can function as high-reflectance soft x-ray diffraction gratings with dispersion rates at least two orders of magnitude larger than what is presently possible with state-of-the-art man-made gratings. This may open up new opportunities in designing and implementing soft x-ray resonant inelastic scattering (RIXS) spectrometers with spectral resolution improved by up to two orders of magnitude, which may further advance a very dynamic filed of the RIXS spectroscopy.

High diffraction efficiency of a grating can be achieved by use of inclined facets. This type of grating, normally referred to as a blazed grating, has facets that are arranged so that there is an equal angle on the incident and diffracted sides, and thus can be thought of as reflecting light into a particular order. Conventionally blazed gratings are made by diamond mechanical ruling, or more recently by anisotropic etching of silicon. However it is difficult with these processes to achieve a very low blaze angle as well as to precisely control it. This has become particularly important for applications involving Free Electron Lasers, where a very grazing incidence angle has to be used to avoid damage, and for extension of the working range up to high energies on synchrotrons. In each case, the very small angular size of the source results in a low line density, which in turn results in a low blaze angle. In high groove density multilayer blazed gratings, high precision for the blaze angle is required to match the groove depth to the multilayer d-spacing. We have developed a process which gives the possibility for alteration of the groove profile of a fabricated grating and tune the blaze angle with high precision. The method is based on planarization of the grating grooves by deposition of a SiO₂ sacrificial layer followed by smoothing the surface with Ar plasma etch. Finally, a reactive plasma etching is used to etch off the sacrificial layer together with the surface layer of the Si grating. The optimized plasma etching provides a certain ratio of etch rates of the sacrificial layer and Si and results in reduction of the blaze angle down to a desired value.

Compact and lightweight X-ray micropore optics with high quality stability have been developed utilizing our microfabrication technology. We have fabricated Schmidt type Lobster Eye Optics named Pre Bread Board Model (PreBBM). This optics has a plurality of oblique grooves having a width of 10 um formed by laser modification and wet etching in flat glass substrate. Both smoothing by annealing and Pt coating were applied on the groove surface to complete Pre-BBM. And we conducted the first X-ray irradiation test. In order to obtain high X-ray reflectivity, next challenge is to reduce surface roughness of the micropore side wall to nanometers or less. We adopted magnetic fluid polishing and glass annealing technology as a method to reduce surface roughness of the glass. We are trying to optimize the condition to achieve side wall surface roughness of 1 nm.

A new kind of hard X-ray / gamma-ray optic is proposed. This optics may be useful for collecting primary X-rays or gammarays from a point source and direct secondary hard X-rays into a given direction. The main element of the proposed optic is a multichannel collimator, which is a glass poly-capillary tube. Incident gamma-rays or hard X-rays with energy E from a point source cross the channel walls of the collimator at a given angle to channel axis and produce secondary Comptonscattered hard X-rays with energy E₁ < E. A small portion of the secondary, Compton-scattered hard X-rays, which are emitted in parallel to the center axis of each channel, transmit through the collimator without absorption, forming a hard Xray beam.

The next generation light sources such as diffraction-limited storage rings and high repetition rate free electron lasers (FELs) will generate x-ray beams with significantly increased peak and average brilliance. These future facilities will require x-ray optical components capable of handling large instantaneous and average power densities while tailoring the properties of the x-ray beams for a variety of scientific experiments. We have been developing diamond x-ray refractive lens for 3 years. Standard deviation of lens residual gradually was decreased to sub-micron values. Post-ablation polishing procedure yields 10-20nm surface roughness, Ra. In this paper we report on recent developments towards beam-line ready optic.

X-ray focusing optics, irrespective of the technology employed, require extremely high precision of both manufacturing and metrology, and also require in-use operational stability. As the x-ray beam is being transported to the experimental area, distortions due to misalignments, the imperfection of optics, and other effects will accumulate and result in beam quality degradation—spatial broadening, and the appearance of beam tails and aberrations. Recently, it became possible, using ptychography methods, to quantify cumulative beam phase distortion. Based on these measurements, a single element of refractive optics, a phase correction plate, can be designed to correct for this cumulative beam degradation. Following successful experiment at LCLS [Seiboth, F. et al. Perfect X-ray focusing via fitting corrective glasses to aberrated optics. Nat. Commun. 8, 14623 doi: 10.1038/ncomms14623 (2017)], where phase plate was etched out of silica, Euclid Techlabs LLC uses femtosecond laser ablation to produce similar phase correctors out of diamond. In this paper we will present several examples along with measurements done at the Advanced Photon Source of Argonne. This approach is plug and play, and can be employed in a large number of x-ray beamlines around the world. The ability to synthesize and rapidly produce a phase-correcting plate is a paradigm shift in the design of x-ray optics systems. Rather than require unprecedented fabrication tolerance, for example, for x-ray mirrors, while simultaneously managing thermal effects like non-uniform expansion due to the x-ray flux, one can focus on thermal stability while employing a simpler geometry, and use a complimentary phase plate that will correct the imperfections of the mirror. This technology will increase the quality of the x-ray beam and simplify beam delivery and alignment.

A wavefront propagation analysis of a soft X-ray beamline using the HYBRID method is reported. All elements of the beamline: the energy dependence of the insertion device emission, the beamline mirrors and their measured figure errors, the variable-line-spacing grating and its measured figure error, and several exit slit settings, are included in the simulations. The analysis of the propagated undulator radiation through the beamline at two slightly different deflection parameter values demonstrates that, within the beamline angular acceptance and when the monochromator is tuned to the same energy, the flux is higher when the undulator is tuned to slightly higher energy than that of the monochromator. The energy resolution determined from the FWHM of the energy bandwidth transmitted through the exit slit is narrower when the undulator is tuned to higher energy than the monochromator. This is not the case when the resolution is based on the standard deviation of the transmitted energy band. The diffraction effects due to the exit slit size and their consequence on the spot size at the sample position are investigated for a few photon energies.

We have been developing a compact and lightweight X-ray micropore optics for small satellite mounting. We achieved three-dimensional machining into a single flat glass substrate by femtosecond laser irradiation and wet etching. In addition to the three-dimensional machining, we applied annealing and magnetic fluid polishing to reduce surface roughness of inner walls, and coated the surface with Pt layer by ALD to improve the reflectance. In this paper, we introduce our achievement on micromachining into a single flat glass substrate. As principle verification, we achieved extremely small hole with 2μm diameter and 100μm depth, slit with 10μm width, 2500(50×50) multiple through holes in 26μm pitch and hole angle control within 0.15 degree. We will further develop manufacturing techniques and explore other applications of our micropore optics, such as fundamental research, security inspection and infrastructure inspection.

Lobster eye X-ray optics in the one dimensional (1D) arrangement has advantages in higher reflectivity, especially for higher energies, compared to classical two dimensional (2D) Schmidt’s arrangement. One dimensional optics can determine only one direction of the incoming beam. There is placed a strip in front of the optics for determining of the second direction. This strip is made of X-ray proof material which blocks the incoming beam and thus causes a gap in the line. Based on these facts, it is possible to determine the position of each point source which has enough signal to gap ratio. Unfortunately, the intensity of sources is not possible to assess by this method.

The paper presents the X-ray Multi-Foil Optical (MFO) system proposed for the CubeSat demonstrator. The Lobster Eye (LE) design represents wide field of view (FOV) X-ray optics. This feature is unique in comparison with classical Wolter types of X-ray optics that reaches a field of view of typically 1 degree or less. LE optics can theoretically achieve an unlimited field of view, but for practical reasons, modules with, for example, 6 deg x 6 deg large FOV can be designed, developed, and constructed. Presented theoretical study of the Multi-Foil wide-field X-ray “Lobster eye” based optics shows effects of focal length, foil spacing and reflective surface (Au versus Ir). The main parameters that have been compared are effective area, gain, FWHM and/or transmission. The system can be used as an all‐sky monitor in future projects.