This PDF file contains the front matter associated with SPIE Proceedings Volume 10385, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Single-grating Talbot imaging relies on high-spatial-resolution detectors to perform accurate measurements of X-ray beam wavefronts. The wavefront can be retrieved with a single image, and a typical measurement and data analysis can be performed in few seconds. These qualities make it an ideal tool for synchrotron beamline diagnostics and in-situ metrology. The wavefront measurement can be used both to obtain a phase contrast image of an object and to characterize an X-ray beam. In this work, we explore the concept in two cases: at-wavelength metrology of 2D parabolic beryllium lenses and a wavefront sensor using a diamond crystal beam splitter.

For modern synchrotron light sources, the push toward diffraction-limited and coherence-preserved beams demands accurate metrology on X-ray optics. Moreover, it is important to perform in-situ characterization and optimization of X-ray mirrors since their ultimate performance is critically dependent on the working conditions. Therefore, it is highly desirable to develop a portable metrology device, which can be easily implemented on a range of beamlines for in-situ metrology. An X-ray speckle-based portable device for in-situ metrology of synchrotron X-ray mirrors has been developed at Diamond Light Source. Ultra-high angular sensitivity is achieved by scanning the speckle generator in the X-ray beam. In addition to the compact setup and ease of implementation, a user-friendly graphical user interface has been developed to ensure that characterization and alignment of X-ray mirrors is simple and fast. The functionality and feasibility of this device is presented with representative examples.

The contamination of optical elements (mirrors and gratings) with carbon still is an issue when using soft x-ray synchrotron radiation. With an in-house developed HF-plasma treatment we are able to decontaminate our optics in-situ from carbon very efficiently. The cleaning device, a simple Al-antenna, is mounted in situ inside the mirror- and grating vacuum chambers. A systematic study of the HF-plasma cleaning efficiency was performed acquired with in-situ and exsitu methods for monitoring: An atomic force microscope (AFM) and a scanning tunneling microscope (STM) were used before and after the cleaning process to determine the surface morphology and roughness. Reflectivity angular scans using the reflectometer at the BESSY-II Metrology Station [1-3] allowed to estimate the thickness of the remaining Clayer after different cleaning steps and thereby helped us to determine the etching rate. Reflection spectra measurements in the range of 200 eV – 900 eV show the complete removal of Carbon from the optics without contaminating it with any other elements due to the plasma treatment. The data show that the plasma process improves the reflectivity and reduces the roughness of the surface. In addition to that, the region of the optical surface where the carbon has been removed becomes passivated.

We introduce a method for using Fizeau interferometry to measure the intrinsic resolving power of a diffraction grating. This method is more accurate than traditional techniques based on a long-trace profiler (LTP), since it is sensitive to long-distance phase errors not revealed by a d-spacing map. We demonstrate 50,400 resolving power for a mechanically ruled XUV grating from Inprentus, Inc.

The European XFEL is a large facility under construction in Hamburg, Germany [1]. It will provide a transversally fully coherent X-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 milliseconds long pulse train at 10Hz), short wavelength (down to 0.05 nm), short pulse (in the femtoseconds scale) and high average brilliance (1.6x10²⁵ photons / s / mm² / mrad² / 0.1% bandwidth). It will have initially three main beamlines, named SASE1, SASE2 and SASE3. The last one is considered a "soft X-ray" beamline, with energies that will span from 0.25 to 3 keV, delivering photon pulses to SQS (Small Quantum System) and SCS (Spectroscopy and Coherent Scattering) experiments. The optical transport of the almost diffraction- limited beam is done using 950 mm long mirrors, cooled with InGa eutectic bath and super-polished (50 nrad RMS slope error and less than 3 nm PV residual height error). A VLS-PG (Variable Line Spacing - Plane Grating) monochromator is installed to enhance the spectral coherence of the beam. The basic characteristics for the grating substrates are: 530 mm length, InGa eutectic bath cooled and ion-beam polished with gravity sag compensation. For the initial commissioning of the beamline, a shorter grating (150 mm long) will be prepared and installed. We recently received the 150 mm long grating and we present here its characterization performed using Fizeau Interferometry. The VLS parameters are especially investigated and characterized. This grating's study can give an interesting insight in the present status of European XFEL metrology, but also additional information for the future development and characterization of the final 530 mm long grating.

As resolving power targets have increased with each generation of beamlines commissioned in synchrotron radiation facilities worldwide, diffraction gratings are quickly becoming crucial optical components for meeting performance targets. However, the metrology of variable-line-spacing (VLS) gratings for high resolution beamlines is not widespread; in particular, no metrology facility at any US DOE facility is currently equipped to fully characterize such gratings. To begin to address this issue, the Optics Group at the Advanced Photon Source at Argonne, in collaboration with SOLEIL and with support from Brookhaven National Laboratory (BNL), has developed an alternative beam path addition to the Long Trace Profiler (LTP) at Argonne’s Advanced Photon Source. This significantly expands the functionality of the LTP not only to measure mirrors surface slope profile at normal incidence, but also to characterize the groove density of VLS diffraction gratings in the Littrow incidence up to 79°, which covers virtually all diffraction gratings used at synchrotrons in the first order. The LTP light source is a 20mW HeNe laser, which yields enough signal for diffraction measurements to be performed on low angle blazed gratings optimized for soft X-ray wavelengths. We will present the design of the beam path, technical requirements for the optomechanics, and our data analysis procedure. Finally, we discuss challenges still to be overcome and potential limitations with use of the LTP to perform metrology on diffraction gratings.

An angle metrology project (SIB58 Angles) addressing the challenging issues related to performance of autocollimators in slope measuring profilers run for three years and was completed recently with cooperation of a wide range of partners. Outcomes of the project which are for interest to the X-ray optics community are presented; new aperture centring device (ACenD) for the accurate centring of a beam-limiting aperture in front of an autocollimator (with a positional accuracy of ±0.1 mm), performance of autocollimators with varying distances to reflector at small apertures, developed guides for calibration of autocollimators and reference angle encoders, first 2D calibration of autocollimators, new devices and novel methods for traceable generation and measurement of angles at nanoradian precision.

Lack of an extreme high-accuracy angular positioning device available in the United States has left a gap in industrial and scientific efforts conducted there, requiring certain user groups to undertake time-consuming work with overseas laboratories. Specifically, in x-ray mirror metrology the global research community is advancing the state-of-the-art to unprecedented levels. We aim to fill this U.S. gap by developing a versatile high-accuracy angle generator as a part of the national metrology tool set for x-ray mirror metrology and other important industries. Using an established calibration technique to measure the errors of the encoder scale graduations for full-rotation rotary encoders, we implemented an optimized arrangement of sensors positioned to minimize propagation of calibration errors. Our initial feasibility research shows that upon scaling to a full prototype and including additional calibration techniques we can expect to achieve uncertainties at the level of 0.01 arcsec (50 nrad) or better and offer the immense advantage of a highly automatable and customizable product to the commercial market.

A portable device has been developed in TUBITAK UME to calibrate high precision autocollimators with nanoradian precision. The device can operate in the range of ±4500" which is far enough for the calibration of the available autocollimators and can generate ultra-small angles in measurement steps of 0.0005" (2.5 nrad). Description of the device with the performance tests using the calibrated precise autocollimators and novel methods will be reported. The test results indicate that the device is a good candidate for application to on-site/in-situ calibration of autocollimators with expanded uncertainties of 0.01" (50 nrad) particularly those used in slope measuring profilers.

A new metrology and assembly facility was constructed at CNPEM and turned recently into operation. The facility includes an assembly area of 100 m², a high-precision mechanical metrology laboratory and an optical metrology laboratory (OML), both of 50 m², and provide improved environmental and instrumental conditions. All three laboratories sit on inertial blocks with special foundations originally developed and tested as prototype for the SIRIUS tunnel floor. The inertial blocks perform very well in attenuation of external vibrations. The OML is cleanroom ISO7 and has temperature stability better than ±0.1 K. Measurements of the surface under test (SUT) using NOM, Fizeau- Interferometer (FI), Micro-Interferometer (MI) and AFM as the four instruments inside the OML cover the full required range of spatial frequencies. We report on the performance of the NOM and FI, the first instruments installed in the OML.

The R&D work on the ALS upgrade to a diffraction limited electron ring, ALS-U, has brought to focus the need for near-perfect x-ray optics, capable of delivering light to experiments without significant degradation of brightness and coherence. The desired quality of the optics is illustrated by the residual surface slope and height errors of <50−100 nrad (rms) and <1−2 nm (rms), respectively. This catalyzes the development at the ALS new ultra-high accuracy metrology methods. Fundamental to the optimization of beamline performance of such x-ray optics, metrology must be capable of characterizing the optics with accuracy even better than the specification. The major limiting factors of the current absolute accuracy are systematic errors inherent to the metrology instruments. Here, we discuss details of work at the Advanced Light Source (ALS) X-Ray Optics Laboratory (XROL) on the development of advanced experimental methods and techniques to suppress, measure, and eliminate the instrumental systematic errors. With examples, we show how the implementation of these methods allows us to significantly improve the capabilities and performance of the existing lab equipment used for characterization and optimal tuning of high quality x-ray optics. We will also review the ALS XROL plans for instrumentation upgrades and development of sophisticated methods for metrology data processing and usage. The discussion will be illustrated with the results of a broad spectrum of measurements of x-ray optics and optical systems performed at the lab. Supported by the U.S. Department of Energy under contract number DE- AC02-05CH11231.

Along with the demanding requirements for the extreme limit pushing LCLS II project, comes the challenge in metrology work for qualifying the optical and mechanical components. Besides qualifying the components against specifications, it is also crucial to study performance, repeatability and stability of the mirror systems designed for meeting the LCLS II conditions. Therefore a dedicated metrology laboratory has been jointly funded by LCLS II project and LCLS facility. The laboratory, located close to the experimental hall of LCLS, is currently equipped with a 6” Fizaeau interferometer (Zygo DynaFiz) and a Zygo NewView 8300 white light interferometer. A profilometer, hosting a Long Trace Profiler optic head, an autocollimator (Moller Wedel) and a Shack Hartman head (SHArPer, Imagine Optics), is under assembling. The combination of these instruments will enable us to measure spatial periods from the µm scale up to 1.5 m. Further implementation in progress are the implementation of a stitching method for the 6” interferometer and reduction of environmental noise. The results obtained from measuring 1-m long flat mirrors, with sub-nm shape errors, produced by Jtec, show a very high sensitivity of the interferometer. These results, as well as the results obtained in testing the bender prototype and some diffraction gratings, will be presented.

The research and development work on the Advanced Light Source (ALS) upgrade to a diffraction limited storage ring light source, ALS-U, has brought to focus the need for near-perfect x-ray optics, capable of delivering light to experiments without significant degradation of brightness and coherence. The desired surface quality is characterized with residual (after subtraction of an ideal shape) surface slope and height errors of <50-100 nrad (rms) and <1-2 nm (rms), respectively. The ex-situ metrology that supports the optimal usage of the optics at the beamlines has to offer even higher measurement accuracy. At the ALS X-Ray Optics Laboratory, we are developing a new surface slope profiler, the Optical Surface Measuring System (OSMS), capable of two-dimensional (2D) surface-slope metrology at an absolute accuracy below the above optical specification. In this article we provide the results of comprehensive characterization of the key elements of the OSMS, a NOM-like high-precision granite gantry system with air-bearing translation and a custom-made precision air-bearing stage for tilting and flipping the surface under test. We show that the high performance of the gantry system allows implementing an original scanning mode for 2D mapping. We demonstrate the efficiency of the developed 2D mapping via comparison with 1D slope measurements performed with the same hyperbolic test mirror using the ALS developmental long trace profiler. The details of the OSMS design and the developed measuring techniques are also provided.

The development of deterministic polishing techniques has given rise to vendors that manufacture high quality threedimensional x-ray optics. The surface metrology on these optics remains a difficult task. For the fabrication, vendors usually use unique surface metrology tools, generally developed on site, that are not available in the optical metrology labs at x-ray facilities. At the Advanced Light Source X-Ray Optics Laboratory, we have developed a rather straightforward interferometric-microscopy-based procedure capable of sub microradian characterization of sagittal slope variation of x-ray optics for two-dimensionally focusing and collimating (such as ellipsoids, paraboloids, etc.). In the paper, we provide the mathematical foundation of the procedure and describe the related instrument calibration. We also present analytical expression describing the ideal surface shape in the sagittal direction of a spheroid specified by the conjugate parameters of the optic’s beamline application. The expression is useful when analyzing data obtained with such optics. The high efficiency of the developed measurement and data analysis procedures is demonstrated in results of measurements with a number of x-ray optics with sagittal radius of curvature between 56 mm and 480 mm. We also discuss potential areas of further improvement.

The advents of fully coherent free electron lasers and diffraction limited synchrotron storage ring sources of x-rays are catalyzing the development of new, ultra-high accuracy metrology methods. To fully exploit the potential of these sources, metrology needs to be capable of determining the figure of an optical element with sub-nanometer height accuracy. Currently, the two most prevalent slope measuring instruments used for characterization of x-ray optics are the auto-collimator based nanometer optical measuring device (NOM) and the long trace profiler (LTP) using pencil beam interferometry (PBI). These devices have been consistently improved upon by the x-ray optics metrology community, but appear to be approaching their metrological limits. Here, we revise the traditional optical schematic of the LTP. We experimentally show that, for the level of accuracy desired for metrology with state-of-the-art x-ray optics, the Dove prism in the LTP reference channel appears to be one of the major sources of instrumental error. Therefore, we suggest returning back to the original PBI LTP schematics with no Dove prism in the reference channel. In this case, the optimal scanning strategies [Yashchuk, Rev. Sci. Instrum. 80, 115101 (2009)] used to suppress the instrumental drift error have to be used to suppress a possible drift error associated with laser beam pointing instability. We experimentally and by numerical simulation demonstrate the usefulness of the suggested approach for measurements with x-ray optics with both face up and face down orientations.

X-ray focusing mirrors with elliptical shape are widely used in synchrotron facilities for micro-, nano-scale focusing experiments. Surface interferometry plays an important role in the x-ray mirrors figuring with subnanometer accuracy. To avoid the second order error in stitching interferometry, relative angle determinable stitching interferometry (RADSI) is under development. This method was first developed by Yamauchi et al from Osaka University, which uses a planar mirror to correct the relative stitching angle between the neighboring subapertures. Here, we use RADSI to measure the x-ray spherical and elliptical mirrors with 300mm aperture Fizeau interferometer. The interferometer is combined with 4 accurate rotation and tilt stages for the stitching measurement. To ensure the stitching accuracy, we first studied the measurement accuracy within every single subaperture. Multiple measurement is used to decease the random error of single subaperture. The subaperture positioning is also carefully corrected to ensure the pixels of the adjacent subapertures in overlapping areas can be matched well. A first stitching measurement result of a spherical mirror with 30 meters radius is shown.

X-ray mirror figure errors are commonly measured in the synchrotron community using Long Trace Profiler (LTP) or Nanometer Optical measuring Machine (NOM) instruments, both providing 2D slope measurement. 3D reconstruction is possible but time consuming, and requires a high stability of environmental conditions over long periods which is not easy to achieve. Characterisation of the complete topography of the mirror surface is essential for the application of deterministic figure correction techniques and also to reveal undesired stresses or deformations, such as twist, introduced by optomechanical mounting. At the ESRF metrology laboratory Fizeau stitching methods are under development. A full automated mechanical setup dedicated to stitching measurement of long flat mirrors is now operational. We have previously demonstrated accurate reconstruction by stitching 2D profiles acquired from Fizeau subaperture measurements. This work is focused on 3D reconstruction of flat mirror surfaces up to one meter long. Repeatability, accuracy and in particular the influence of the transmission element will be discussed.

An X-ray ellipsoidal mirror requires nanometer-level shape accuracy for its internal surface. Owing to the difficulty in processing the surface, electroforming using a high precision master mandrel has been applied to mirror fabrication. In order to investigate the replication accuracy of electroforming, a measurement method for the entire internal surface of the mirror must be developed. The purpose of this study is to evaluate the shape replication accuracy of electroforming. In this study, a three-dimensional shape measurement apparatus for an X-ray ellipsoidal mirror is developed. The apparatus is composed of laser probes, a contact probe, reference flats, a z-axis stage, and a rotation table. First, longitudinal profiles of a mandrel or mirror placed vertically on the rotation table are measured at several angular positions. Subsequently, without realignment of the measured sample, circularity at every height is measured at regular intervals of 0.1 mm. During each measurement, the effect of motion errors is calculated and subtracted from each profile by referring to the distances between the probes and reference flats. Combining the circularity data with the longitudinal profiles, a three-dimensional error distribution of the entire surface is obtained. Using a mandrel with nanometer-level shape accuracy and a replicated mirror, the performance of the measurement apparatus and the replication accuracy are evaluated. Measurement repeatability of single-nanometer order and replication accuracy of sub-100-nm order are confirmed.

Determination of multilayer structure was developed so much, but most of studies focused on the relationship between structural imperfections and reflectivity. These imperfections, whether interfacial roughness and interdiffusion or surface feature, measured by grazing X-ray scattering, atomic force microscopy or electric microscopy, reflect relatively high-frequency characteristics. The mid-frequency figure errors were regarded as the main factor to produce large satellite peaks near the focusing spot in the multilayer K-B mirror and were found to produce stripes in the far-field imaging. We report novel method to study mid-frequency interface and layer growth characterizations of multilayer structure using at-wavelength speckle scanning technique. This work is beneficial for matching multilayer manufacture technology to the optimization of beam performances.