This PDF file contains the front matter associated with SPIE Proceedings Volume 12694, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

A high-energy white synchrotron x-ray beam enables penetration of relatively thick and highly absorbing samples. At the P61A White Beam Engineering Materials Science Beamline, operated by Helmholtz-Zentrum Hereon at the PETRA III ring of the Deutsches Elektronen-Synchrotron (DESY), a tailored x-ray radiography system has been developed to perform in-situ x-ray imaging experiments at high temporal resolution, taking advantage of the unprecedented x-ray beam flux delivered by ten successive damping wigglers. The imaging system is equipped with an ultrahigh-speed camera (Phantom v2640) enabling acquisition rates up to 25 kHz at maximal resolution and binned mode. The camera is coupled with optical magnification (5x, 10x) and focusing lenses to enable imaging with a pixel size of 1,35 micrometre. The scintillator screens are housed in a special nitrogen gas cooling environment to withstand the heat load induced by the beam, allowing spatial resolution to be optimized down to few micrometres. We present the current state of the system development, implementation and first results of in situ investigations, especially of the electron beam powder bed fusion (PBF-EB) process, where the details of the mechanism of crack and pore formation during processing of different powder materials, e.g. steels and Ni-based alloys, is not yet known.

Tabletop extreme ultraviolet (EUV) sources based on high harmonic generation (HHG) have been used as a powerful tool for probing magnetism. Obtaining magnetic information via magneto-optical contrast often requires the energy of the light to be tuned to magnetic resonance energies of the magnetic element present in the material; therefore, it is essential to calibrate the HHG spectrum to well defined absorption energies of materials. We have designed and assembled a HHG based EUV source for studying transition metal magnetic materials at their resonant M-absorption edges (35-75 eV of photon energy). One material of interest is iron, for which the iron M_2,3 edge is 52.7 eV (23.5 nm wavelength) according to CXRO. We prepared and characterized a thin sample of iron for absorption spectroscopy and calibration of the absorption edge with beamline 6.3.2 at the Advance Light Source (ALS) in Lawrence Berkeley National Laboratory. This well characterized sample was capped with gold to prevent oxidation. From these measurements we extracted the absorption part of the index of refraction β spectrally and confirmed that the absorption edge of iron is 52.7 eV. With this information, we can better calibrate the HHG spectrum of our tabletop EUV source. Calibration of the HHG spectrum was achieved using model fitting the HHG spectrum using the grating equation and law of cosines while taking account into the results of the ALS data. We have determined that driving wavelength of the HHG process to be 773 nm. We also conclude that the chirp of the driving laser pulse can cause an energy shift to a HHG spectrum.

The surface figure of an x-ray mirror was improved by differential deposition of WSi₂ layers. DC magnetron sputtering through beam-defining apertures was applied on moving substrates to generate thin films with arbitrary longitudinal thickness variations. The required velocity profiles were calculated using a deconvolution algorithm. Height errors were evaluated after each correction iteration using off-line visible light surface metrology. WSi₂ was selected as a promising material since it conserves the initial substrate surface roughness and limits the film stress to acceptable levels. On a 300 mm long flat Si mirror the shape error was reduced to less than 0.2 nm RMS.

We developed a single-reflective-layer deposition system for the in-house production of x-ray mirrors. The system is based on magnetron sputtering and the linear motion of the substrate. Substrates with lengths up to 500 mm and widths up to 50 mm are processable. In this study, the deposition conditions of Au as a single reflective layer were investigated, assuming an application to a soft x-ray focusing mirror. Under various operating conditions, a 5-nm-thick Cr binder layer was deposited on a (100) Si wafer, followed by a 50-nm-thick Au film, and the surface roughness was evaluated by an atomic force microscope. The surface roughness of the Au film deposited using this system was in the range of 0.5–0.6 nm with no clear dependence on power (50–150 W), base pressure (3.4–5.0 × 10⁻⁵ Pa), and Ar flow rate (40–200 sccm).

Large Wolter mirrors fabricated by high-precision Ni electroforming process have been used for x-ray telescopes. Since the replication accuracy of these mirrors is on the order of 100 nm, the surface figure correction is necessary for improving the figure accuracy. Recently, we have proposed a new figure correction scheme utilizing a Si layer on the mirror surface. The thickness of Si film can be measured with accuracy at a 1 nm level by a thickness measurement gauge, and Si removal process will be applied so that the figure error is reduced. In this study, we developed the DC magnetron sputtering system especially for depositing a Si on the inner surface of the Wolter mirror. By optimizing the parameters such as Ar gas pressure and the sputter power, we demonstrated a coating of uniform Si layer on the Wolter mirror. The uniform Si layer with a thickness of 90 nm was successfully produced with an accuracy of ±10 nm in PV(Peak-to-Valley). The uniformity of the deposition using this method was 10 nm of PV(Peak-to-Valley).

High-precision monolithic mirrors are used in the soft x-ray beamlines of synchrotron radiation facilities. A figure measurement technique is essential for the fabrication of high-precision mirrors. In recent years, mirrors of various shapes have been proposed, and a versatile figure measurement technique is required. Tactile measurements are one of the most suitable methods for evaluating the figure errors of x-ray mirrors with steep and complex geometries. Because a tactile measurement probe has a wide range of measurable depths and angles and can eliminate measurement errors depending on the sample curvature, tactile measurements have been applied to the fabrication of monolithic mirrors for soft x-ray focusing. In this study, a soft x-ray focusing mirror with concave and convex freeform surfaces on its monolithic substrate was fabricated based on tactile measurements for figure correction. The high- and mid-spatial-frequency roughness were 0.14-0.17 nm and 0.8 nm in RMS, respectively. Furthermore, the figure error evaluated using the tactile measurement was 2.64 nm in RMS.

Diffracting crystals are extensively used at synchrotron beamlines as x-ray monochromators and phase retarders. Imperfect growth processes, surface damage occurring during fabrication, and strain caused by poor clamping methods can all degrade the quality of these crystals and the x-ray beams diffracted by them. Because x-ray topography of these crystals can reveal both the location and the magnitude of these defects, it is now regularly used as an acceptance test for diffracting crystal optics at the Diamond Light Source synchrotron. Before installation on beamlines, crystal optics are inspected at the versatile bending-magnet B16 Test Beamline, where a variety of topographic techniques have been implemented with both white and monochromatic x-ray beams. A set of digital detectors permits rocking curve imaging with a choice of fields of view and spatial resolution down to 2 μm. Test crystals may be mounted in a variety of geometries according to need. For inspecting monochromator crystals fabricated for imaging applications, both on-the-fly scans and stitching techniques have been used to compose maps of surface defects. First crystals of multi-crystal monochromators have been tested under realistic cryocooled conditions, and their design has been improved to minimize strain. The Diamond Light Source’s x-ray topography program serves not only its own beamlines, but also industrial users and other x-ray synchrotron facilities.

We demonstrate high-energy x-ray (HEX-ray) generation using 3-mJ, 850fs pulses on a liquid metal target in a laser plasma x-ray Source (LPXS). The measured HEX-ray spectra reach into the MeV spectral range. The spectrum follows approximately a Boltzmann energy distribution with a maximum HEX-ray “temperature” of 350 to 440 keV. The low laser intensity requirement, orders of magnitude less than previously reported, enables operation with widely available picosecond, millijoule laser systems with hundreds of Watt average laser power. Based on lasers with Yb-doped active media, compact HEX-ray sources driven with kilowatt average laser power are achievable very soon.

A well-known bottleneck to achieving synchrotron-like results in an laboratory x-ray system is the performance of laboratory x-ray sources, which have orders of magnitude lower brightness than synchrotrons and do not produce monochromatic x-rays. Performance is particularly limited in the soft/tender x-ray regime. We have developed a x-ray microfocus source called FAAST™ (Fine Array Anode Source Technology), which narrows the performance gap between laboratory-based and synchrotron-based systems. Sigray’s patented FAAST x-ray source has an anode with several user-selectable materials on it, each material producing a different characteristic spectrum, thus enabling energy optimization of the output beam. Selection of the appropriate x-ray energies results in increases of x-ray fluorescence cross-sections by as much as three orders of magnitude and has benefits for all major lab-based analyses (XRF, XRD, imaging, etc.). Sigray has made breakthroughs in the target manufacturing process that expands the selection of target materials from the standard metals to include exotic materials that emit x-rays in the soft and tender x-ray regime.

There is demand for optics for EUV applications including microscopy and diagnostic devices for EUV lithography exposure masks. Au and W are common materials for such applications, but they have relatively low theoretical diffraction efficiency. Ru is a good candidate for 13.5 nm wavelength applications as it has greater theoretical efficiency than Au or W. It also has the benefit of oxidizing less during plasma etching or on exposure to air. Oxidation can be a concern for materials with higher theoretical zone plate efficiency such as molybdenum because it can lead to a significant decrease in theoretical efficiency. Additionally, molybdenum also presents more etching challenges than Ru, particularly concerning sidewall verticality. Our work involves the fabrication and characterization of diffraction gratings and zone plates for 13.5 nm EUV applications. The fabrication of W and Ru phase zone plates with 80 nm outer zone width through electron beam lithography and plasma etching is presented. Characterization of the zone plate through SEM and STEM imaging, as well as EDX analysis, was performed. A comparison between the W and Ru zone plates is given.

A cavity-based x-ray free-electron laser (CBXFEL) is a possible future direction in the development of fully coherent x-ray sources. One of the challenges of a CBXFEL is the requirement of the three-dimensional overlapping of the μm-sized electron beam with the circulating μm-sized x-ray beam in an x-ray cavity of tens or hundreds of meters long. In the framework of the CBXFEL R&D collaborative project of Argonne National Laboratory, SLAC National Accelerator Laboratory, and Spring-8, we present here the development of an x-ray diagnostics system for an accurate alignment of x-ray beams in the CBXFEL cavity. All the designed diagnostics components have been fully characterized at the Advanced Photon Source to demonstrate a sub-μrad-angular and μm-spatial alignment accuracy for the CBXFEL cavity.

To provide excellent conditions for the scientific user experiments at European XFEL, a good beam stability is essential. But to accomplish this task, it is needed to overcome some difficulties and challenges. Especially, the very long beamlines – up to about 1 km of photon distribution tunnels – of the hard x-ray beamlines are amplifying the effect of vibrations. Each small displacement of an optical component might result in a beam motion in the experimental end station of a non-neglectable order of magnitude and therefore disturbing or even making impossible the execution of the experiments. With increasing number and continuously improving beam quality since the start of user operation at EuXFEL, experiments are becoming more demanding and therefore vibration issues are more and more relevant. Different vibrations were reported from the scientific instruments, like occasionally occurring large horizontal beam motions of several hundred microns or shift of the beam position from week to week. These disturbances may require extra tuning time and lead to a loss of usable beamtime. Because they are not always present, it is very challenging to analyse the root causes. Different studies have been undertaken to determine the vibration at different beamline components and to identify possible sources. At the hard x-ray beamlines, SASE 1 and SASE 2, Laser Doppler Interferometers have been installed to observe the vibrations present at the x-ray mirrors and other optical components. With external excitation, sensitive resonance frequencies of the mirror chambers were studied in detail. Continuous monitoring with seismometers and microphones gives information about the basic background sound spectra and local noise sources.