X-ray Mirrors Research Articles

A High Efficiency and Precision Smoothing Polishing Method for NiP Coating of Metal Mirror.

The NiP coating has excellent wear and corrosion resistance, and electroless nickel-phosphorus coating is one of the best measures for surface modification of metal optical devices. The NiP layer could be processed by single-point diamond turning (SPDT). However, the periodic marks on the surface of the NiP coating processed by SPDT will lead to diffraction and stray light, which will reduce the reflectivity and image quality of the mirror. This paper studied smoothing polishing based on chemical mechanical polishing to remove turning periodic marks efficiently. Firstly, we studied the chemical corrosion and mechanical removal mechanism of smoothing polishing of the NiP coating through theoretical analysis. Then, the influencing factors of processing the quality of smoothing polishing are analyzed, and the optimal machining parameters and polishing slurry formula are formulated. Finally, through the developed process, the surface roughness of Root Mean Square (RMS) 0.223 nm is realized on the NiP coating, and an ultra-smooth surface that can meet the service accuracy of a hard X-ray mirror is obtained. Our research simplifies the high-precision machining process of the NiP coating and improves the machining efficiency. Therefore, it can be used as a new high-precision manufacturing NiP coating method.

Performance of the X-Calibur hard X-ray polarimetry mission during its 2018/19 long-duration balloon flight

X-Calibur is a balloon-borne telescope that measures the polarization of high-energy X-rays in the 15–50 keV energy range. The instrument makes use of the fact that X-rays scatter preferentially perpendicular to the polarization direction. A beryllium scattering element surrounded by pixellated CZT detectors is located at the focal point of the InFOCµS hard X-ray mirror. The instrument was launched for a long-duration balloon (LDB) flight from McMurdo (Antarctica) on December 29, 2018, and obtained the first constraints of the hard X-ray polarization of an accretion-powered pulsar. Here, we describe the characterization and calibration of the instrument on the ground and its performance during the flight, as well as simulations of particle backgrounds and a comparison to measured rates. The pointing system and polarimeter achieved the excellent projected performance. The energy detection threshold for the anticoincidence system was found to be higher than expected and it exhibited unanticipated dead time. Both issues will be remedied for future flights. Overall, the mission performance was nominal, and results will inform the design of the follow-up mission XL-Calibur, which is scheduled to be launched in summer 2022.

Combined processing strategy based on magnetorheological finishing for monocrystalline silicon x-ray mirrors.

Higher requirements for monocrystalline silicon x-ray mirrors have been put forward with the development of synchrotron radiation optics. The existing processing technologies limit their efficiency while achieving high-precision manufacturing of x-ray mirrors. Hence, this paper formulates a processing strategy of employing magnetorheological finishing (MRF) to make the precision of x-ray mirrors fully meet the standard. The combination of fine polishing and super-smooth processing can effectively improve the surface quality of mirrors. The residual error, wavefront gradient, and surface roughness of the mirror can reach 7.2 nm, 0.42 µrad, and 0.28 nm, respectively, after several iterations. The research not only indicates that MRF can replace the existing manufacturing method and greatly improve processing efficiency, but also provides technical support for optimizing the processing route of x-ray mirrors.

Derivation of closed-form ellipsoidal X-ray mirror shapes from Fermat's principle.

Ellipsoidal and plane-elliptical surfaces are widely used as reflective, point-to-point focusing elements in many optical systems, including X-ray optics. Here the classical optical path function approach of Fermat is applied to derive a closed-form expression for these surfaces that are uniquely described by the object and image distances and the angle of incidence at a point on a mirror surface. A compact description facilitates design, modeling, fabrication, and testing to arbitrary accuracy. Congruent surfaces in two useful coordinate systems - a system centered on the ellipsoid's axes of symmetry and a mirror-centered or `vertex' system with the surface tangent to the xy plane at the mirror's center - are presented. Expressions for the local slope and radii of curvature are derived from the result, and the first several terms of the Maclauren series expansion are provided about the mirror center.

Stress-balancing in piezoelectric adjustable x-ray optics

Next-generation x-ray observatories require lightweight, high throughput optics that maintain a <0.5 arcsec resolution to probe the physics of black holes and gain understanding of the early universe. One potential type of x-ray mirror consists of a 400-μm thick curved Corning EAGLE XG® glass substrate with a Cr/Ir x-ray mirror coating deposited on the front (concave) side and an array of radio frequency sputtered Pb0.995 ( Zr0.52Ti0.48)0.99Nb0.01O3 piezoelectric thin film actuators on the back (convex) side to enable correction of figure errors. A stress-balancing process was developed to correct the figure distortion arising from thin film stresses in the actuator layers. Compressively stressed SiO2 films were deposited on the convex side of the mirror to balance the tensile integrated stress of the actuator array while also matching the film thickness distribution. Finite-element methods were used to assess the impact of film thickness distributions on the convex and concave substrate surfaces. The resulting models show peak-to-valley figure errors of 105 nm, well within the 1-μm peak-to-valley dynamic range of the piezoelectric adjusters. In contrast, when stress compensation was done with an iridium mirror film deposited on the front side, the mismatched thickness distribution results in peak-to-valley figure errors over 3 μm.

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS)

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket instrument that flew on July 30, 2021 from the White Sands Missile Range, NM. The instrument was designed to address specific science questions that require differential emission measures of the solar soft X-ray spectrum from 6 – 25[Formula: see text]Å(0.5 – 2.1[Formula: see text]keV). MaGIXS comprises a Wolter-I telescope, a slit-jaw imaging system, an identical pair of grazing incidence paraboloid mirrors, a planar grating and a CCD camera. While implementing this design, some limitations were encountered in the production of the X-ray mirrors, which ended up as a catalyst for the development of a deterministic polishing approach and an improved meteorological technique that utilizes a computer-generated hologram (CGH). The opto-mechanical design approach addressed the need to have adjustable and highly repeatable interfaces to allow for the complex alignment between the optical sub-assemblies. The alignment techniques employed when mounting the mirrors and throughout instrument integration and end-to-end testing are discussed. Also presented are spatial resolution measurements of the end-to-end point-spread-function that were obtained during testing in the X-ray Cryogenic Facility (XRCF) at NASA Marshall Space Flight Center. Lastly, unresolved issues and off-nominal performance are discussed.

Analytic descriptions of parabolic X-ray mirrors.

On X-ray beamlines and telescopes, glancing-incidence mirrors with parabolic profiles are used to collimate, focus, and collect light. Here, analytic descriptions for paraboloidal, plane-parabolic, and parabolic cylindrical mirrors in several congruent geometries that are commonly used in fabrication, metrology, and modeling are provided. The exact expressions are derived directly from Fermat's principle, without coordinate transformations, in several mirror-centered coordinate systems, including one with the surface tangent to the central point of intersection. Coefficients for a sixth-order polynomial series approximation are calculated for that coordinate system.

Measurement Uncertainty of Highly Asymmetrically Curved Elliptical Mirrors Using Multi-Pitch Slope Stitching Technique

Soft X-ray off-axis elliptical mirrors bring new challenges for X-ray mirror metrology. These highly asymmetrically curved elliptical cylindrical mirrors with a total slope range &amp;gt;10 mrad are extremely challenging to measure. Their total slope range exceeds the measuring range of most angular sensors used for X-ray mirror inspection. To overcome this problem, it is possible to stitch partial slope data by measuring the mirror at different pitch angles (multi-pitch angles). By revisiting the theory of the multi-pitch Nano-accuracy Surface Profiler (NSP), we derive the sampling position error on the mirror surface as a function of the mirror height profile and the measurement error of the pitch rotation center. When measuring “extreme”, highly asymmetrically curved, elliptical mirrors, the calculation of the mirror height profile with iterative reconstruction outperforms the classical “flat assumption” (i.e., assuming that the mirror sag is negligible). As demonstrated by our simulations, a proper tolerance evaluation on the measurement of pitch rotation center is needed to assess the measurement accuracy (systematic error) for these strongly aspherical mirrors using the multi-pitch NSP technique. Taking a real design of an “extreme” elliptical mirror as a case study, we conduct a Monte Carlo simulation to mimic the measurement and characterization process to analyze the impact of several error sources. With the measurement uncertainty of the pitch rotation center, the multi-pitch NSP measurement can estimate the grazing angle θ and the chief ray location xo with their uncertainties, as well as the slope residuals.

Erratum: "Optimal deformation procedure for hybrid adaptive x-ray mirror based on mechanical and piezo-driven bending system" [Rev. Sci. Instrum. 92, 123706 (2021)

Erratum: "Optimal deformation procedure for hybrid adaptive x-ray mirror based on mechanical and piezo-driven bending system" [Rev. Sci. Instrum. 92, 123706 (2021)

Application of Flow Field Analysis in Ion Beam Figuring for Ultra-Smooth Machining of Monocrystalline Silicon Mirror.

X-ray free-electron lasers are large modern scientific devices that play an important role in fields such as frontier physics and biomedicine. In this study, a light source is connected to an experimental station through beam lines, which requires numerous ultra-smooth and high-precision X-ray mirrors. Monocrystalline silicon is an ideal substrate material where ion-beam figuring is required. However, the ultra-smooth surface is damaged after the ion-beam figuring. Through an analysis of the machined surface, it is found that in the process of vacuum pumping, the impurities in the cavity adhere to the machined surface and increase the roughness after processing. Therefore, an optimized vacuum-pumping scheme is proposed. The experiment demonstrates that the original value of the processed surface roughness remains unchanged.

XRISM: X-ray imaging and spectroscopy mission

The X-Ray Imaging and Spectroscopy Mission (XRISM) is a JAXA/NASA X-ray observatory with collaboration from ESA and several institutes and academic institutions worldwide. It is proposed to fulfill the promise of high-resolution X-ray spectroscopy with imaging once realized but unexpectedly terminated by a mishap of ASTRO-H/Hitomi. XRISM carries two sets of X-ray mirror assemblies and is equipped on the focal plane with a [Formula: see text] pixelized X-ray micro-calorimeter array and an aligned X-ray CCD camera. With the combination of high-resolution spectroscopy imaging and the broader field of view, XIRSM is expected to pioneer a new horizon of the Universe in X-ray astrophysics. Aiming to launch the satellite in the Japanese Fiscal Year 2022, we fabricate the instruments and test for the satellite integration starting at the beginning of 2022. This paper reports the development status, reviewing the science objectives and the operation plan.

Diamond-carbide-silicon composite &amp;quot;skeleton&amp;quot; as a promising material for X-ray optical substrates

The paper proposes the use of diamond-carbide-silicon composite &amp;quot;Skeleton&amp;quot;oledR coated with amorphous silicon as substrates for multilayer X-ray mirrors for powerful synchrotron radiation sources (3+ and 4th generation). The surfaces with the following parameters were obtained using standard deep polishing methods: flatness at the level of RMS90%=54.2 nm; effective roughness sigmaeff~1.0 nm; high-frequency roughness sigma2x2~0.1 nm. Keywords: x-ray optics, x-ray mirrors, substrates for x-ray mirrors, roughness.

Research and creation of broadband X-ray mirrors with a spectral transmission band coinciding with emission lines and the possibility of filtering

The article considers broadband multilayer X-ray mirrors based on Mo/Be and Mo/Si structures with a transmission band coinciding with the Si Lα (13.5 nm) and Sn (13.5 nm) emission lines. The described structures are of great interest for the currently developed liquid source of EUV radiation, since they make it possible to increase the efficiency of the source-X-ray optical system due to the &amp;quot;complete&amp;quot; capture of emission lines. Keywords: extreme ultraviolet radiation, emission spectrum, laser spark, multilayer X-ray mirror.

Перспективные длины волн для проекционной литографии с использованием синхротронного излучения

Promising wavelengths for next-generation lithography with a wavelength shorter than 13.5 nm based on a synchrotron X-ray source are discussed. Theoretical and experimental values of the reflection coefficients of multilayer X-ray mirrors providing the maximum reflectivity in the range of 11.4-3.1 nm are presented. The theoretical efficiency of multilayer optics is compared for different wavelengths.

Development of Lightweight High Resolution X-ray Mirror with CFRP

Development of Lightweight High Resolution X-ray Mirror with CFRP

Prospective wavelengths for projection lithography uing synchrotron radiation

Promising wavelengths for next-generation lithography with a wavelength shorter than 13.5 nm based on a synchrotron X-ray source are discussed. Theoretical and experimental values of the reflection coefficients of multilayer X-ray mirrors providing the maximum reflectivity in the range of 11.4-3.1 nm are presented. The theoretical efficiency of multilayer optics is compared for different wavelengths. Keywords: X-ray lithography, multilayer X-ray optics, multilayer X-ray mirrors.

Алмаз-карбид-кремниевый композит "скелетон" как перспективный материал для подложек рентгенооптических элементов

The paper proposes the use of diamond-carbide-silicon composite "Skeleton"® coated with amorphous silicon as substrates for multilayer X-ray mirrors for powerful synchrotron radiation sources (3rd+ and 4th generation). The surfaces with the following parameters were obtained using standard deep polishing methods: flatness at the level of RMS90%=54.2 nm; effective roughness sigmaeff~1.0 nm; high-frequency roughness sigma2х2~0.1 nm.

Исследование и создание широкополосных рентгеновских зеркал со спектральной полосой пропускания, совпадающей с эмиссионными линиями и возможностью фильтрации

The article considers broadband multilayer X-ray mirrors based on Mo/Be and Mo/Si structures with a transmission band coinciding with the Si Lα (13.5 nm) and Sn (13.5 nm) emission lines. The described structures are of great interest for the currently developed liquid source of EUV radiation, since they make it possible to increase the efficiency of the source-X-ray optical system due to the “complete” capture of emission lines.

Система визуализации плазменного факела бетатронного источника рентгеновского излучения

The paper describes the design of a microscope for studying a betatron radiation source based on the PEARL femtosecond laser complex in the SXR and EUV wavelength range. The main optical element of the microscope is a spherical Schwarzschild objective a x5 magnification. The device allows to study the size and spatial structure of the interaction area of laser radiation with matter, at a selected wavelength in the EUV or SXR range with a resolution of δx = 2.75 microns. The operation wavelength (=13.5 nm) is set by multilayer X-ray mirrors. Thin-film absorption filters are used to suppress the background component of the signal.

Ru/Sr multilayer mirrors for the spectral range 9-12 nm

The results of studies of Ru/Sr multilayer mirrors optimized for the working wavelength range of 9-12 nm are presented in the paper. Within the framework of the presented article the strontium based multilayer structures with stable over time reflective characteristics were obtained for the first time. It is shown that Ru/Sr mirrors have the highest reflectance of all known reflective coatings, with the exception of beryllium-containing, in the spectral range of 9-12 nm. Keywords: multilayer X-ray mirrors, X-ray lithography, X-ray radiation.