Advances in X-Ray/EUV Optics and Components XIX

Steeply curved free-form X-ray mirrors, represented by monolithic ellipsoidal or Wolter mirrors, are required for sub-micron focusing without chromatic aberration in the soft X-ray region. Such mirrors require a different approach to surface machining and measurement than conventional shallow sag mirrors such as 1D elliptical or plane mirrors. A few fabrication examples of Wolter mirrors have been reported, where surface measurement using a surface profiler with a contact probe was used for figure correction. However, due to differences in measurement methods and fabrication difficulties, the fabrication performance has not been evaluated on a comparative basis. In this study, a high-precision plane mirror is fabricated by the same process of steeply curved free-form mirrors. The figure measurement accuracy was comparatively evaluated and the performance of the process is discussed.

The surface figure of x-ray mirrors can be improved by differential deposition of thin films. To achieve the required corrections, WSi2 layers of variable thickness were deposited through beam-defining apertures of different openings. The substrates were moved in front of the particle source with specific velocity profiles that were calculated with a deconvolution algorithm. Two different DC magnetron sputter systems were used to investigate the correction process. Height errors were evaluated before and after each iteration using off-line visible light surface metrology. Several Si mirrors were used to study the impact of the initial shape errors on the performance of the correction approach. On 300 mm long flat mirrors the shape errors were routinely reduced by a factor of 10-20 down to levels below 0.5 nm RMS.

Large Wolter mirrors fabricated by high-precision Ni electroforming process have been used for X-ray telescopes. We have been developing the surface figure correction method based on measuring film thickness distributions. The thickness of Si film can be measured with an accuracy in 10 nm level by a laser interferometer. In this study, we developed the inner surface measurement system and the abrasive slurry jet machining system for this method. In this presentation, we will introduce the performance of the measurement system and the machining system.

We have been developing a transmission soft X-ray microscope utilizing Wolter mirrors at a soft X-ray beamline of SACLA. We upgraded the soft X-ray microscope to enable simultaneous visible light imaging and soft X-ray imaging. To achieve this, we divided the annular apertures of the condenser and objective Wolter mirrors into two sections, allowing for soft X-ray imaging with one part and visible light imaging with the other. Our microscopy allows imaging cells with fluorescent labels by visible light while observing them with water window soft X-rays, which is useful for studying living cells.

Nanometer-thin multilayers are crucial in various optical applications, from lithography to X-ray instruments. The interface sharpness between layers determines reflectivity losses. Metrology is vital for understanding the interface forming mechanisms at an atomic level. Single techniques like TEM and XRR provide atomic or electronic density resolution, while XPS data about the compound formation. We extended our metrology portfolio with two in-house customized techniques: XSW and LEIS. The XSW technique is used for the analysis of thin film atomic profiles. The specific analysis of the background in LEIS spectra was used to analyze the interface with sub-nm resolution. A hybrid metrology approach combining these techniques is essential for efficient multilayer characterization. The metrology-driven multilayer growth optimization will be illustrated as an example of W/Si multilayers. By analyzing X-ray reflectivity and XSW data with a single model, we revealed the formation of WSix at W/Si interfaces, leading to poor performance. The introduction of 0.1 nm B4C diffusion barriers improved reflectivity, showing their direct contribution to enhanced performance.

Polarized neutrons are crucial for various research fields, but existing multilayer optics have limitations. By incorporating 11B4C into Fe/Si layers during deposition, we address these challenges. This method enhances reflectivity and polarization by creating smoother interfaces and optimizing scattering length density. Adding 15 at.% of 11B4C to Fe/Si multilayers improves reflectivity by 125% and polarization by 20%. It also reduces diffuse scattering and eliminates magnetic coercivity, making the layers magnetically soft. This enables saturation at low external fields. Our findings, supported by X-ray and neutron reflectivity measurements, suggest that integrating 11B4C into Fe/Si multilayers improves neutron optics, promising better performance in scattering facilities.

Short- and ultra-short-period multilayer (ML) structures play a crucial role in wavelength dispersive X-ray fluorescence (WD-XRF). In WD-XRF a ML serves as an analyzer crystal to disperse emission lines of light elements in the O-Kα – Al-Kα range (λ=2.36 – 0.834 nm). For these reasons, MLs with periods ranging from 1.0 to 2.5 nm are very interesting. Due to the short period, the reflectance of such MLs is extremely sensitive to interface imperfections. Our research focuses on synthesis and characterization of MLs with d-spacing between 2.5 nm and 1.0 nm, combining tungsten (W) absorber with B4C, Si and Al spacers. These combinations show high theoretical reflectance in the full range from C-Kα (4.48nm) all the way down to S-Kα (0.54nm). By optimizing the ion polishing process: ion species, energy, and polishing frequency, we show that a major improvement in reflectivity can be achieved: with the most optimal ion polishing process, a factor 2x in reflectivity was achieved for 1.0 and 1.1 nm MLs, with a record reflectivity of almost 10% at lambda=0.84nm for 1.1nm W/Si.

A fully automated, high resolution method to measure the variable line density of a spherical grating is presented. This process combines the advantages of a high resolution detector (long trace profiler, LTP) with the use of two motorized stages that overcome the limited dynamic range of the same sensor. The principle: the grating position is scanned with the linear stage while a feedback loop between the LTP detector and the round table maintains the Littrow condition. The angle of the round table is recorded as function of grating position. The accuracy of the angle measurement is then improved by subtracting the recorded residual angle measured by the LTP. The line density is then calculated from this angle. This method can be also easily applied to shape measurements of long steeply curved mirrors, whose accurate curvature evaluation is limited by the dynamic range of the typical LTP.

We present a prototype of the optical level deflection sensor capable of measuring deflection angle in the range of 0 – 0.15 rad with repeatability of 20 nrad, and spot size of the order of 1 mm. The sensor employs a single, cooled, commercial CMOS array detector. We compare the performance of the system with the earlier described design, analytical formulas, and numerical simulations [1]. Reference 1. Walecki, Wojtek J. "The multiple array detector optical lever deflection angle metrology for x-ray mirrors, and semiconductor applications." In Advances in Metrology for X-Ray and EUV Optics X, vol. 12695, pp. 72-93. SPIE, 2023.

Fast and non-destructive dimensional reconstruction of periodic nanostructures is crucial to the characterization of test structures in the semiconductor industry. While conventional scatterometry techniques may yield multiple adjacent solutions for the structure’s shape, combining soft X-ray scattering and fluorescence in a single measurement using a dedicated chamber reduces uncertainties. This hybrid approach narrows solution space by including additional mass distribution information about the periodic nanostructure and provides reconstruction accuracy in the sub-nanometer range.

We report the results of the performance characterization of a Fizeau interferometer in the spatial and spatial frequency domains performed with tilted plane test samples with different surface topographies, including the Uniformly Redundant Array and Highly Randomized Binary Pseudo-random patterns. We discuss the possible origins of the observed irregularities and systematic errors based on a simplified optical model of the tool. The ultimate goal is development of the test artifacts and procedures for thorough calibration of Fizeau interferometers. This work was supported by the U. S. Department of Energy under contract number DE-AC02-05CH11231 and award number DE-SC0022373.

UMARI - Universal Metrology Apparatus for Reflectometry and Interferometry – provides a stack of linear and rotation stages for alignment and stitching of optics up to 1 m length with the Fizeau interferometer and the micro interferometer. It permits the measurement of optics in side-bounce or bounce-up orientation. Degree of freedom, range, resolution, and repeatability of each stage axis is specified based on the analysis of the stitched data, internal optical limitations of the Fizeau interferometer and the alignment process. Tests have revealed limitations with available stages. For example, a tip-tilt stage with a resolution of 0.5 µrad is needed. This work presents the tests and results leading to the final specification of UMARI and the mechanical design.

We explore technological, metrological, and analytical aspects of the application of a technique for calibrating the instrument transfer function (ITF) of 3D optical surface profilers used for metrology with significantly curved x-ray optics. The test standards with elementary sizes between 80 nm and 2.5 µm have been fabricated onto curved optics and used for thorough characterization of 3D optical profilers for metrology with significantly curved x-ray optics. The progress on the fabrication technology, retrace error analysis, and data acquisition and analysis procedures are discussed. This work was supported by the U.S. Department of Energy under contract number DE-AC02-05CH11231 and by the NASA STTR/SBIR program under award number 80NSSC20C0505.

UA3P is a contact-type 3D Profilometer that is widely used for measuring optical components such as aspheric lenses and free-form mirrors. This time, we would like to introduce our efforts to measure objects with higher precision. Through this effort, we will be able to measure nanometer-level measurements on aspheric surfaces and free-form mirrors.

The human brain contains 86 billion cells, but so far they could not be visualized in their entirety. The task corresponds to a dataset of petabyte size – analogous to plotting every star in the Milky Way. Quite recently, we demonstrated feasibility of cellular-resolution full-brain imaging for ethanol-immersed and paraffin-embedded human brain using the tomography setup at the beamline P07 (Petra III, DESY, Hamburg, Germany). The next challenge involves acquiring and disseminating a human brain atlas that will create a paradigm for investigating other human organs, high-performance engineering devices, and unique cultural heritage objects related to big data.

COSI is a NASA Small Explorer (SMEX) satellite mission for launch in 2027. COSI is a wide-field gamma-ray telescope designed to survey the entire sky at 0.2-5 MeV. It provides imaging, spectroscopy, and polarimetry of astrophysical sources, and its germanium detectors provide excellent energy resolution for emission line measurements. I will overview the COSI mission including the science, technical design, and status. The heart of the COSI instrument is an array of high-resolution cross strip germanium sensors. I will focus deeper on germanium detector developments in support of the COSI mission and ongoing work to optimize the in-flight detector performance.

Synchrotron Thailand is planning to build a new ring shortly. One of the main components of the beamline is the optic. The high-precision multilayer coating system for X-ray optics was created to develop knowledge, skills, and creativity. In 2021-2024, we received a fundamental fund from the government to build a coating system for X-ray optics. We started from the conceptual design until the fabrication machinery in-house. I will talk about design, progress, and collaboration in this topic.

The Brazilian 4th-generation synchrotron, Sirius, has one of the beamlines that will operate on a range of 8 to 70 eV, known as the SAPE beamline (Angle-resolved PhotoEmission). It is aiming to study topological and 2D materials. The thermal management of the optic systems on these beamlines is particularly challenging due to the high heat load, which has the potential to deform optical surfaces. This work describes the precisely constrained design of SAPE’s mirrors, outlines their heat load management strategies, analyzes the impact of O2 on the entire system, introduces the magnetic damper, and presents the results of test validations.

We report on progress towards controlling the shape of Si flat mirrors that can be used to steer or focus X-rays used in synchrotron beamline experiments. Our method for realizing this control is through coated Si wafers with a magnetostrictive material and overcoat of a magnetic hard layer of NiCo. We show results of comparing shape changes with an array of mini voice-coils applied to a Si wafer and to a commercial product using the same array. We describe the adjustment in graze angles that are possible and preliminary design based on the voice-coil array.

X-ray fluorescence imaging (XFI) provides the non-invasive tracking of entities like immune cells using dedicated markers in objects of different sizes. XFI typically uses synchrotron pencil beams to reach a high spatial resolution. To minimize the applied dose and scan time, a coarse scan can precede a finer one. A unique approach utilizing Bragg reflection at a cylinder optic with mosaic graphite-based material significantly enlarges the fine X-ray beam. Experiments at the P21.1 beamline at PETRA III synchrotron reveal a remarkable beam enlargement of 10 to 20 times, showcasing a 68% dose reduction and 62% scanning time reduction. This innovative technique holds promise for efficient and low-dose XFI applications.

We consider the specification of hard x-ray monochromator crystals for both high-efficiency and diffraction-limited optical performance in the new era ultra-high-brightness fourth-generation x-ray light sources. Within a double-crystal monochromator, the power absorbed by the first crystal can significantly affect both the surface profile, which affects the transmitted wavefront, and the spatial distribution of the reflected light’s photon energy, due to non-uniform thermal expansion. Based on the properties of silicon double-crystal monochromators used on several protein crystallography beamlines at the Advanced Light Source, we derive the dependencies that set the performance specifications necessary to achieve the ultimate performance. We study water-cooled room-temperature crystals, and cryogenically cooled crystals across a variety of operating conditions.

Ion-beam figuring (IBF) is one of the most powerful techniques for ultra-precise x-ray optics fabrication. IBF is capable of providing sub-nanometer accuracy for an optical surface of x-ray mirrors as well as substrates for x-ray gratings for most demanding applications. The ultra-precise grating blanks undergo subsequent multi-step processing to form grooves on the substrate surface, using a variety of methods such as diamond ruling, plasma etch, ion beam milling, wet etching etc. The groove shaping process should preserve initial precision of the optical surface, which might be challenging due to complexity of the process. Hence, some post-ruling IBF is necessary to recover the ultra-precise optical surface, provided the grating grooves survive the ion-beam treatment. We demonstrated successful IBF correction of a low blaze angle grating earlier [Voronov et al., Opt. Express 31 (21) 2023]. In this work we investigate a possibility of post-production IBF correction for lamellar x-ray gratings. We report on impact of the IBF process on groove profile, surface roughness, and diffraction efficiency of the grating.

Pump-probe spectroscopy is a well-established technique used to monitor the dynamics occurring in any state of matter, in timescales ranging from attoseconds to seconds and beyond. When performed at synchrotrons the technique offers probe with high repetition rate, wide scanning capabilities in terms of energy, spatial resolution at the nanometre scale, and elemental specificity. Recently, recognizing the impact and importance of such experiments across its science spectrum, Diamond with the strong support from the UK academic community, invested and deployed a novel laser source, PORTO, which can be used in various beamlines for pump-probe experiments. PORTO is a portable femtosecond laser system which has been used so far, for optical-pump and X-ray-probe absorption (XAS) and diffraction (XRD) experiments, as well as for macromolecular crystal shaping. Here we demonstrate, results from the fields of photocatalysis, structural biology, (photocage release studied using fixed-target serial crystallography) and photoredox reactivity in metal-oxo clusters

While there are many variations of an Inelastic X-ray Scattering (IXS) spectrometer, the figure of merit is often the energy resolution and the throughput. As part of the LCLS-II-HE project, the DXS team is developing a hard X-ray IXS spectrometer with a resolution of 5 meV at 11.215 keV. The spectrometer relies on a so-called post-sample-collimation scheme, and this high degree of resolution comes with stringent precision and stability requirements. SHADOWOui is used to simulate the setup and analyze the tolerance of 4 optics’ axis (translation, pitch, yaw, roll) and the miscut angle of the channel-cut crystal of the design. The simulation indicates that a 5 meV resolution is achievable by ensuring stringent pitch and vertical translation tolerances. Furthermore, the simulation suggests that a miscut angle of 79 degrees, which necessitates high-quality crystal manufacturing, is optimal.

Resonant inelastic X-ray scattering (RIXS) is a widely used spectroscopic technique for analyzing elementary excitations. However, this process is inefficient and thus difficult to apply to imaging. We propose to stimulate the RIXS (SRIXS) process using a soft X-ray free-electron laser (SXFEL), increasing the photon yield by up to 6 orders of magnitude [Higley, Commun. Phys. 5 83 (2022)]. By designing a new achromatic full-field twin Wolter mirror microscope and multi-aperture grating, it should become possible to measure SRIXS by imaging the full X-ray spectrum at many spatial points simultaneously. To test the feasibility of SRIXS imaging, we simulate the SRIXS signal strength with a three-level Maxwell-Bloch model. Using the parameters of the SACLA BL1 SXFEL, we show that SRIXS imaging is feasible, requiring a peak intensity of 1016 W/cm2 and sub-micron focus size, readily achievable with the proposed microscope.

We propose a system independent of the electron beam focal spot and stability. Through simulation, this has been demonstrated with a point-like transmission X-ray target and an unfocused electron beam. These simulations demonstrated improved spatial resolution and reduced imaging artifacts. However, simple metal evaporation methods have not yielded adequate X-ray photons for practical CT acquisition. In this work we leverage advanced electroplating fabrication techniques to create embedded copper targets in silicon. These advanced techniques, commonly used to fabricate Through Substrate Via (TSV) interconnects for complimentary metal-oxide semiconductor (CMOS) circuitry, are leveraged in this work to create high-aspect-ratio features for X-ray transmission targets. We demonstrate micro targets with a volume increase of more than 50x what we were able to achieve with evaporated surface targets. Additionally, through simulations we compare various target volumes, materials, and substrates against commercial bulk transmission targets for signal optimization.

X-ray Magnetic Circular Dichroism (XMCD) is a crucial method for selectively probing magnetic properties in complex materials. Operating at the EMA beamline in Sirius, it utilizes quarter-wave plates for polarization control, enabling X-ray helicity changes at 10 Hz. To optimize photon flux, we propose a redesigned instrument with enhanced capabilities. Engineered to oscillate crystals up to 1 kHz, operate within an energy range of 2.8 to 20 keV, and follow High-Dynamic Double Crystal Monochromator flyscan at 1 keV/s, the system accommodates eight crystal configurations while maintaining a vacuum below 1e-8 mbar. This advancement expands XMCD capabilities, enabling measurements on samples with minimal magnetization and promising significant progress in synchrotron-based magnetic property research across diverse materials.