This PDF file contains the front matter associated with SPIE Proceedings Volume 12679, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

The re-formulation phase of the next generation x-ray observatory ATHENA (Advanced Telescope for High ENergy Astrophysics) – now NewATHENA - is being utilized for further improvements of the optics technology. The Silicon Pore Optics (SPO) remains the technology of choice, since it uniquely combines a low mass, large effective area, and good angular resolution, addressing the challenge of the NewATHENA X-ray optics. The performance and preparation for the cost-effective implementation of the flight optics is being further evolved in a joint effort by industry, research institutions and ESA. The SPO technology greatly benefits from investments in the semiconductor industry and maximizes technology spin-in. Dedicated facilities have been and are being created to produce the required mirror plates, assemble them into stacks and mirror modules, integrate them into the complete telescope and measure the performance and compatibility with the NewATHENA technical and programmatic requirements. An overview of the activities preparing the implementation of the NewATHENA optics is provided.

Silicon Pore Optics (SPO) have been invented and developed to enable x-ray optics for space applications that require a combination of high angular resolution while being light-weight to allow achieving a large mirror surface area. In 2005, the SPO technology development was initiated by the European Space Agency (ESA) for a flagship x-ray telescope mission and is currently being planned as a baseline for the NewATHENA mission scheduled for launch in the 2030s. Its more than 2m diameter mirror will be segmented and comprises of 492 individual Silicon Pore Optics (SPO) grazing-angle imagers, called mirror modules. Arranged in concentric annuli and following a Wolter-Schwartzschild design, the mirror modules are made of several tens of primary-secondary mirror pairs, each mirror made of silicon, coated to increase the collective area of the system, and shaped to bring the incoming photons to a common focus in 12 m distance. The mission aims to deliver an angular resolution of better than nine arc-seconds (Half-energy width) and effective area of about 1.1 m² at an energy of 1 keV. We present in this paper the status of the optics production and illustrate not only recent x-ray results but also the progress made on the environmental testing, manufacturing and assembly aspects of SPO based optics.

Silicon Pore Optics (SPO) is a technology that makes it possible to build light-weight x-ray optics modules from silicon mirror plates using semiconductor industry technology and custom robots. By combining a large number of modules, the technology solves the problem of aperture segmentation and achieves a large collecting area with consistently high optical quality. Additionally, SPO is a highly adaptable technology that can be optimized for new applications beyond the Athena mission. Several applications have already been proposed for SPO, including Arcus Probe, a candidate probe-class mission that uses SPO modules in combination with transmission gratings to perform high-resolution spectroscopy. The Off-plane Grating Rocket Experiment (OGRE) uses SPO’s direct bonding techniques to align its reflection gratings to high accuracy. SPO has also been investigated in different optical designs, including x-ray interferometry. Furthermore, SPO technology can be used in Silicon Laue Components (SiLC) to focus hard x-rays and soft gamma rays in the energy range of 80 keV to about 500 keV. In conclusion, SPO technology is mature and can be mass-produced, enabling efficient adaptation to different needs. Its versatility and adaptability make it an excellent candidate for future x-ray astronomy missions and beyond.

The traditional solution foreseen for the realization of very large x-ray mirror modules (diameters above 1 m) is the partition of the optics in azimuth and radial modules (like Silicon Pore Optics in Athena). Even if this approach solves the initial problem of the procurement and the handling of very large substrates, it moves the difficulties in the second phase, when thousands of segments have to be assembled without degrading their optical performances. On the contrary, a simpler large mirror module design could correspond to less than a few hundred thin (2 mm to 4 mm for mirror shells between 0.4 m and 3 m diameter) monolithic shells. This configuration keeps both the advantage of the design simplicity and of the high-resolution capability, achievable through the direct polishing approach. Moreover, it guarantees an impressive gain in the polishing time. A technology development road map for this approach is funded in Italy by ASI and led by INAF-OAB. In this paper, we present the advancements obtained in the development of the different phases of the process and in the procurement of new substrates.

Many modern x-ray missions call for the manufacture of a large quantity of optics. This large manufacturing problem typically requires the establishment of a manufacturing process, we can call a factory. Depending on the initial capability of this factory, it will take time to reach full manufacturing rate. This submaximal rate in turn impacts the total time to manufacture the needed amount of hardware. This paper presents a method to determine the time to complete the manufacturing process, including factory build up. We will show that initial production rate is a highly influential variable in time to complete the manufacturing task and the process to calculate this time is well behaved. This allows future mission planner to make high fidelity schedule estimates of these large manufacturing tasks, which is the challenge facing modern x-ray missions.

The MUlti-slit Solar Explorer (MUSE) is a NASA medium-class explorer mission that is currently in phase B and scheduled for launch no earlier than 2027. The MUSE science investigation aims to use high-resolution and high-cadence spectroscopic and imaging EUV observations of the solar atmosphere to understand the multi-scale physical processes that heat the multi-million-degree solar corona, drive the source of the solar wind, and cause solar activity (flares and coronal mass ejections) that lead to space weather that impacts Earth. MUSE will consist of an EUV context imager and an EUV spectrograph, both requiring normal incidence mirrors with a very high level of polishing and figuring, in order to allow high-resolution imaging and spectroscopy. The mission is led by Lockheed Martin Solar and Astrophysics Laboratory (LMSAL). The payload is being developed by LMSAL and the Center for Astrophysics (CfA) at the Harvard Smithsonian Astrophysical Observatory, while INAF-OAB will produce the focusing mirrors with the financial support of the Italian Space Agency (ASI). In this paper, we describe the first steps that are being taken in the procurement of the focusing mirrors in Zerodur, the work plan with the ion beam figuring and the pitch tool aimed at bringing the surface defects within the specification. Additionally, we describe the metrology system that we are setting up to detect the residual deviation to the final shape.

This conference presentation was prepared for SPIE Optical Engineering + Applications, 2023.

In a previous paper, we presented the concept of using shape memory alloy sheets as the substrate for normal incidence multi-layer coated mirrors. A shape set sheet has been shown to deploy a figure good to 1 micron. This shape is good enough for a “light bucket.” However, if imaging is desired, then post-deployment corrections can be applied. We provide an update on the improvements we have made to our study. These improvements include ray tracing, polishing, adhesion, and fine (nm) surface adjustments.

Electroforming replication technology at Marshall Space Flight Center has a long heritage of producing high-quality full-shell x-ray mirrors for various applications. Nickel alloys are electroformed onto a super-polished mandrel in the electroforming process, then separated to form the replicated full-shell optic. Various parameters in the electroplating configuration could result in the nonuniformity of the shell’s thickness. Thickness non-uniformities primarily occur due to non-uniform electric field distributions in the electroforming tank during the deposition. Using COMSOL Multiphysics simulations, we have studied the electric field distributions during the deposition process. Using these studies, we have optimized the electric fields inside the tank using customized shields and insulating gaskets on the mandrel. These efforts reduced thickness non-uniformity from over 20% to under 5% percent. Improving the thickness uniformity of the shell aids in better mounting and alignment of shells in the optics module. Optimization of the electroforming process, in some cases, improved the optical performance of the shells. COMSOL optimizing of the electroforming process and the experimental results validating these simulations are presented in this article.

NASA / MSFC has made new full-shell NiCo replicated hard X-ray optics for the fourth flight of the Focusing Optics X-ray Solar Imager sounding rocket set to observe the sun in March 2023. The new FOXSI-4 high resolution optics were made using enhanced mandrel polishing techniques incorporating a Zeeko CNC deterministic polishing machine and an improved module assembly station with in-situ metrology. FOXSI-4 will fly three new 2-meter focal length high resolution mirror modules with two shells each. The previous FOXSI-3 optics achieved an angular resolution of 20 arcsec HPD (5 arcsec FWHM) for ten-shell modules. Initial X-ray measurements of FOXSI-4 shells before module integration show a performance of 8 arcsec HPD and 3 arcsec FWHM, a substantial improvement over the FOXSI-3 optics. We present the advances made in the polishing, replication, and assembly processes, and measurements of the performance of the completed modules taken in the Marshall 100 meter X-ray beam line.

The Focusing Optics X-ray Solar Imager 4 (FOXSI-4) is a heliophysics sounding rocket experiment that is currently in its fourth launch campaign. The payload is comprised of seven x-ray telescopes, which each consist of a 2 m focal length grazing incidence mirror module that focuses x-rays onto an imaging detector. For this fourth flight, Marshall Space Flight Center (MSFC) designed, built, and tested three new high-angular-resolution mirror module assemblies (MMAs). This paper describes the design and assembly of the FOXSI-4 MMAs.

We are developing Wolter X-ray optics compatible with the short focal length and small size suitable for SmallSat missions. These X-ray Optics are compact lightweight Wolter-I X-ray optics which are affordable for low cost future missions. We are leveraging the recent and on-going development to build lightweight Wolter-I X-ray optics based on the electroformed nickel replication (ENR) technique. Recent results will be presented.

This paper is an overview of the Next Generation X-ray Optics effort at NASA’s Goddard Space Flight Center. The objective of the NGXO team is to develop and mature an X-ray mirror technology that is capable of building a mirror assembly for flagship missions like Lynx and Probe missions like AXIS, LEM, and HEX-P, as well as Explorer missions like STAR-X. These missions require X-ray mirror assemblies that have comparable or better angular resolution than Chandra’s 0.5 arc-seconds, but have ten to twenty times more effective area under similar mass constraints. The NGXO team combines the stress-free nature of single crystal silicon with advanced polishing techniques to make mirror segments that are of higher figure quality than the Chandra mirror shells, but are at least ten times thinner and therefore lighter. The NGXO work encompasses all elements that make a complete process to design, build, test, and deliver a complete mirror assembly, including optical design, mirror segment fabrication, coating, alignment and bonding to make mirror modules, integration of mirror modules into meta-shells, and integration of meta-shells into a mirror assembly. In addition, the NGXO team also adopts the latest mass-production techniques to ensure that building such a mirror assembly can also meet programmatic, such as schedule and cost, requirements of future missions.

Numerous scientific questions at the forefront of our modern physical understanding require enhanced x-ray astronomical observations beyond the capabilities of existing x-ray telescopes. These observations demand spaceborne x-ray telescopes of unprecedented imaging power. x-ray focusing optics which are simultaneously light weight and of sufficient quality are presently impossible to realize, given real-world constraints and current manufacturing technology. Our group at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) investigates the development of an x-ray mirror manufacturing process capable of meeting the stringent quality, production time, and cost requirements of the next generation of x-ray telescopes. This process employs monocrystalline silicon: a lightweight, stiff, thermally conductive, and readily available material which is free of internal stress. These properties combined make silicon a nearly ideal material for thin mirror substrates. Presently, our process is capable of fabricating sub-arcsecond Half-Power-Diameter (HPD) resolution mirror pairs (primary and secondary) at a sub-millimeter mirror thicknesses and of virtually any x-ray optical design (e.g. Wolter-I, Wolter-Schwarzschild, etc.). Further, the substrates include three-dimensional structures on their backsides to aid their alignment and bonding. The mirror substrate surface quality is generally superior to that of the mirrors on the Chandra X-ray Observatory. This paper describes the various manufacturing steps involved in the production of x-ray mirror substrates and a present status report.

The cold shaping (or cold slumping) replication of thin glass foils is an attractive solution for making future high throughput x-ray telescopes. A similar approach is being successfully used for making the normal-incidence mirrors of Cherenkov telescopes like Magic I and II and CTA. The process starts with a thin flat glass sheet that is curved by means of an imposed force on a precision mandrel with the desired nominal shape. After this forming, the shape of the sheet is blocked using a light and stiff structure usually fixed with a glue layer. At INAF - Osservatorio Astronomico di Brera we started to study this process in the past few years for grazing incidence x-ray mirrors with Wolter I (parabola + hyperbola) shape. The availability of flexible glass foils with thicknesses of a few tens of microns now allows for the fabrication of mirrors with very small curvature radii. To implement a mirror assembly, the foils are stacked together using stiffening ribs in order to connect a shell to the next one and form in this way a monolithic stack of curved foil. The accumulated stress during the bending is kept below affordable limits and the associated spring-back after the replication does not strongly affect the angular resolution. Moreover, other major advantages are the cost/time reduction w.r.t. to other approaches and the preservation of the intrinsic good roughness of the float glass sheets. Good targets for the application of this technology are x-ray missions for hard x-rays with angular resolution in the range of 15-60 arcsec, or IAXO (and demonstrator baby-IAXO) ground-based helioscopes for the detection of solar axions. The recent progress in the cold slumping is described in this paper with optical and mechanical design, presenting the measured results on a stack with three layers.

The case of a Laue lens providing effective area in the energy band 60 keV to 150 keV is investigated. The goal is to establish whether this type of optics could be used to extend polarimetric study of celestial sources beyond the energy range enabled by current-generation grazing incidence mirrors, with a focal length compatible with sub-orbital missions. The Laue lens considered is based on Silicon Laue components (SiLC), which makes use of Silicon Pore Optics technology heritage. A SiLC is a stack of thin crystalline silicon wedged plates that are curved in two directions to provide both radial and azimuthal focusing. SiLC technology is presented and the potential performance of a SiLC lens designed for 8 m focal length is investigated.

The next generation of reflection gratings for future high-energy space observatories need a high degree of customization. Making such gratings will require the use of increasingly complex nanofabrication techniques. One of the current challenges we are investigating is the precise patterning of grooves onto curved substrates. We report on our use of electron-beam lithography to fabricate gratings on cylindrical substrates, specifically designed to be tested for spectral resolution. We will discuss the steps involved and their hurdles, from the alignment of the substrate to the actual writing strategy.

In response to Astro2020 recommendations, NASA has issued an announcement of opportunity for an astrophysics probe explorer. Arcus-Probe is a mission concept featuring two co-aligned high-resolution spectrometers, one for the soft x-ray band, and one for the far ultraviolet. This combination of instruments will provide unprecedented performance for the exploration of feedback that shapes the structure and influences the dynamics of our universe across many scales, ranging from galaxy clusters down to individual stars. In the soft x-ray band the x-ray spectrometer features four parallel channels, comprised of arrays of Silicon Pore Optics (SPO) and Critical-Angle Transmission (CAT) gratings. The channels will provide a combined effective area ⪆350 cm² near O VII (approximately 470 cm² expected), and resolving power R = λ/Δλ ⪆2500 (approximately 3500 expected) across the approximately 12 − 50 Å wavelength range. Light-weight, high-efficiency, blazed and alignment-insensitive CAT gratings have been shown to meet or exceed Arcus requirements for diffraction efficiency, open area, and effective resolving power. A total of 864 to approximately 32 × 32.5 mm² CAT grating facets must be fabricated for Arcus, implying efficient volume production. We describe the x-ray testing and performance of the most recent flight-like grating facets, made from 200 mm Silicon-on-Insulator (SOI) wafers using tools compatible with volume production. Newly acquired SOI wafers with 100 nm device layer thickness control are expected to increase fabrication yields, and ongoing post-fabrication thinning of freestanding CAT grating bars promises increases in diffraction efficiency.

High performance reflection gratings on freeform surfaces and/or with customized groove patterns are highly desirable from an instrument design perspective. Such dispersive elements would have the potential to unlock innovative optical designs, achieve high performance in limited volumes, or enable aberration-correction. We report on an effort to make customized gratings using electron-beam lithography (EBL) and to characterize their performance using interferometric measurements. We describe the design, manufacture, and measurement of two moderate-format (10 mm x 30 mm) gratings fabricated on cylindrical substrates and we quantify the limiting spectral resolution of these gratings.

NiC multilayers have been identified as a promising coating design for hard x-ray astrophysical imaging applications enabling bandpass extension beyond the Pt K-edge of approximately 78 keV. However, these coatings are difficult to deposit with low interfacial roughness below a bilayer thickness of about 35 Å. Utilizing a DC magnetron sputtering system, NiC multilayer of varying d-spacings are deposited on flat Si wafers and characterized using 8.048 keV x-ray reflectometry measurements. The residual coating stress is also measured using interferometry. We investigate how deposition parameters affect both the coating quality (i.e. surface/interfacial roughness, density, etc.) and the residual coating stress. From these experimental results conducted on flat substrates, we employ FEM and ray trace simulations to determine how NiC multilayer stress could impact the figure, and therefore performance, of full shell x-ray optics.

Reflection gratings, are critical components to successful X-ray spectroscopes and represent important priorities for future NASA observatories. As such, significant research efforts have been invested to improve mirror and grating fabrication, resulting in increased collecting area and improved mirror performance. However, residual stresses induced by reflective coatings continue to present challenges, causing mirror deformation, degradation of spectral resolution, and decreased scientific performance. Additionally, stress distributions and the stress response of nanoscale layers (5-30nm) are not well understood and can be difficult to measure. This study demonstrates XRD methods to better characterize and minimize the stress of single and bi-layered reflective thin films at nanoscale thicknesses (5-30 nm) and to more fully understand the stress response of these coatings to deposition conditions. High-Z materials (Pt, Au) have been chosen for this study due to their favorable reflectivity over X-ray wavelengths of interest in the soft X-ray regime.

A novel device that uses the membrane resonance method of measuring stress in thin films to track the stress stability of candidate x-ray reflective coatings is presented. The device is capable of tracking stress changes below 0.1 N/m, which is the threshold where stress-based mirror deformations and resulting degradation of angular resolution can become problematic for next-generation x-ray observatories. The device can be used to determine optimal coatings by evaluating the stress stability of different metals and heat treatments.

The next generation of x-ray telescopes will require mirror segments to be characterized to a surface uncertainty of 5 nm RMS or better. We present axial shift mapping, a Fizeau interferometry method to characterized near-cylindrical null correctors and surfaces. We extend our previously tested technique to cylindrical optics of similar dimensions to x-ray telescope mirrors. We report on progress towards full surface extraction of a cylindrical optic using axial shift mapping.

We present an overview of the development of the X-ray reflective coatings for the NewAthena mission based on the latest mission concept reported by the Science Re-definition Team (SRDT). The reflection of X-rays depends strongly on the material adopted as mirror coating, in this study we re-visit the material options as overcoat for Ir and trade-offs. Along with optimised expected performance based on single layer, bi-layer, tri-layer and multilayer coating designs, we also report on the latest experimental results on X-ray performance of the coatings deposited onto SPO plates by magnetron sputtering. X-ray reflectometry are presented and allow for characterisation of the X-ray mirrors and provide results on performance and stability.

The solar corona is a complex and dynamic region primarily controlled by the magnetic fields. Hence the routine measurement of these fields is crucial. Magnetic field information remains embedded in the polarization profiles of the spectral lines, which can be quantified through spectropolarimetry. Differential Hanle effect is a promising diagnostic tool to probe weak coronal magnetic fields and their vector properties. In a recent study we have found several combinations of spectral lines located in the wavelength range 100 to 1210 Å suitable for the above purpose whose critical Hanle field lies in the range of 0.01-200 Gauss. Since the background emission from the Sun’s underlying layers, such as the photosphere and the chromosphere, is almost negligible at these short wavelengths, the coronagraphic technique is not required to study the solar corona, thereby enabling both on-disk and off-limb measurements. Yet there is no EUV polarimeter built for solar observations. In this context we explored a few polarimeter concepts based on the configurations of two and three reflecting mirrors. The performances of these configurations are studied in terms of their throughput and polarizing power using Zemax software in the wavelength range 740-780 Å. They are also compared with different coating materials namely, BaF₂, MgF₂ and LiF. It is found that BaF₂ has significantly higher throughput and polarizing power in the above stated wavelength range.

The Marshall 100-Meter x-ray Beamline is a user facility for x-ray and EUV optics and instrumentation calibration, located at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Also known as the Stray Light Test Facility, the Marshall-100 provides a range of focal plane detectors, x-ray sources, translation stages, cleanrooms, and high-vacuum level capability to the high-energy astrophysics community. Facility time is made available to Astronomy and Physics Research and Analysis (APRA) funded projects and is also available to the broader community upon request made to beamline management. The beamline has successfully been employed in the calibration of larger scope projects such as the Spectrum-Roentgen-Gamma Astronomical Röentgen Telescope X-ray Concentrator (ART-XC) telescope and the Small Explorer (SMEX) class Imaging X-ray Polarimetry Explorer (IXPE) Space Telescope. Additionally, the Marshall-100 is instrumental in supporting testing related to MSFC’s high-angular resolution optics development program.

At the PANTER x-ray test facility of the Max-Planck-Institute for extraterrestrial Physics, x-ray optics for future missions are developed, tested, and calibrated. For the ESA mission NewATHENA many campaigns to test individual Silicon Pore Optic (SPO) mirror modules have been performed to monitor the different aspects of the performance improvement in terms of Half Energy Width (HEW) of the image Point Spread Function (PSF) and the effective area of the optic. Support is also provided for new x-ray optic test facilities such as the recently commissioned BEaTriX facility for characterizing individual SPO mirror modules and the future VERT-X facility designed to test and calibrate the complete NewATHENA mirror by scanning it with a small parallel x-ray beam. The optics (such as parabolas, Wolter-1) needed for the facilities are calibrated at PANTER using a parallel beam generated with a Fresnel Zone-Plate optimized for 1.5 keV. The results of the recent remeasuring of the SPO “measurement standard” optic is presented here. The objective of this test aimed to confirm the sustained stability of the optical component itself, along with variations between BESSY II in Berlin, PANTER in Neuried, both located in Germany, and the newly finished Minerva beamline at ALBA in Barcelona, Spain. The outcomes from PANTER validate the constancy of the "measurement standard" optic, affirming that crucial parameters, notably the Half-Energy Width (HEW) of the Point Spread Function (PSF), remain unaltered.

The BEaTriX (Beam Expander Testing X-ray) facility has completed the commissioning phase. This unique compact facility – that occupies an area of 8 x 14 m² - provides a large (170 mm × 60 mm) collimated (⪅ 2.5 arcsec) monochromatic beam at the energy of 4.51 keV. Its concept is based on the combination of a microfocus x-ray source, a parabolic mirror, and a set of silicon crystals, one of which is asymmetrically cut with respect to the lattice planes. The tests have proven the BEaTriX capability to perform the acceptance tests for Point Spread Function and Effective Area of the NewAthena Silicon Pore Optics Mirror Modules (MM) with a 3 MM/day throughput. The second BEaTriX beamline at the x-ray of 1.49 keV is currently being developed. The optomechanical design, and simulation of alignment tolerances have been completed. The parabolic mirror is being polished at INAF-OAB, on the basis of the experience matured with producing the parabolic mirror for the 4.51 keV beam line. The crystals for the monochromator (Quartz 10-10) and the beam expander (ADP 101) are being procured. Differently from the 4.51 keV beam line, all three crystals for the 1.49 keV are asymmetrically cut, as a special design has been adopted to guarantee the specifications. Owing to the good results obtained by BEaTriX at the INAF labs in Italy, a feasibility study is also ongoing to replicate the facility with a similar design at cosine B.V. in The Netherlands (where the MMs will be produced) for measuring the MMs SPO at 1.49 and 6.4 keV before and after the vibrational tests.

The mirror assembly of the ESA New - Advanced Telescope for High-ENergy Astrophysics (New-ATHENA) will be the largest x-ray optics ever built. Indeed, its unprecedented size, mass and focal length create great difficulties for the ground calibration. The VERT-X project aims at developing an innovative calibration facility which will be able to accomplish to this extremely challenging task. The design is based on a 2.5 cm² parallel beam produced by an x-ray source positioned in the focus of a highly performing collimator. In order to cover the whole mirror, the beam will be accurately moved by a raster-scan with the capability to tilt up to three degrees in order to test the off-axis performance and the out of field stray-light. The whole system is enclosed in a cylindrical vacuum chamber about 20 m high and with a diameter ranging from 7 to 4 m. By design, VERT-X will be able to measure the New-ATHENA mirror half energy width (HEW) with a precision of 0.1”, all over the field of view, with the source size, the collimator error and the raster scan tracking accuracy being the most important terms of the error budget. The VERT-X project, started in 2018, is financed by ESA and conducted by a consortium that includes INAF together with EIE, Media Lario, BCV Progetti and Apogeo Space. This paper presents the current state of the development and manufacturing of the most critical systems of the facility, namely the raster-scan mechanism and the source-collimator vertical assembly.

The X-Ray and Cryogenic Facility (XRCF) at Marshall Space Flight Center is the world’s largest x-ray optic calibration facility and NASA’s premier cryogenic optical test facility. Built specifically to calibrate the Chandra telescope, the facility contributed to several other x-ray missions until 2005 when it became dedicated to normal incidence optical testing at cryogenic temperatures. Recently the facility’s x-ray test capability has been returned to service and updated. New beam monitors, focal plane detectors, and test article and instrument positioning systems have been added. The x-ray data acquisition system has been updated. A real-time position monitoring metrology system is being developed that will enable calibration of large diameter optics via partial illumination in a diverging beam. The newly expanded x-ray test capabilities of the facility will be discussed.

NASA / MSFC has been preparing for X-ray calibration of the large optic for the future ESA Athena mission at the 500 meter XRCF beamline. Improvements include new facility X-ray detectors (Six Amptek C2 window SDDs and a PI-MTE3 4k CCD camera), stages, and verification of the facility's operation to the level reached for the ground calibration of the Chandra X-ray telescope. The XRCF 1.5 meter beam size requires that a flight Athena optic be calibrated by combining measurements from the six individual sub-sectors of the full optic. New XRCF capabilities for the Athena measurement include the ability to measure 12 meter focal length optics with the focal point not co-linear with the facility optical axis. As part of these preparations, in January 2023 we tested an SPO module at the XRCF, aligning the optic in the facility and measuring the point spread function and effective area at two separate energies. Our results agree well with previous measurements of this module taken at the MPE PANTER X-ray beamline. We present a synopsis of the XRCF facility and its X-ray testing equipment, results from the XRT#4 testing campaign in January 2023, and show that the XRCF is currently capable of testing and calibrating large optics for the next generation of flagship and probe class X-ray observatories.

The Einstein Probe Wide-field X-ray Telescope (WXT), planned to launch in late 2023, is dedicated to the study of time-domain high-energy astrophysics to monitor variable objects in the range of 0.5 to 4.0 keV. The full wide-field telescope is made up of 12 Lobster-eye modules. Each module consists of an optics assembly of 36 Micro Pore Optic (MPO) chips divided into four sectors and four CMOS detectors positioned in the respective focal plane of each sector. At the PANTER x-ray test facility, we characterize the performance of one of the 12 flight mirror modules. The full flight model calibration includes measurements for detailed focus searches, extended mosaic scans of the on-axis Point Spread Function (PSF), and Focal Plane Mappings (FPM) covering various off-axis, and one on-axis exposure, performed for each individual mirror sector and at various energies. The best focus positions were determined at the energies C-K, O-K, Cu-L, and Ti-K. The optic was characterized in terms of Half Energy Width (HEW) and effective area on-axis and off-axis at the energies C-K (only FPM), Ti-L, O-K, Cu-L, Al-K, W-M, and Ti-K, and two broad energy ranges, very low Energy band continuum (vlEbc 0.2 to 2.0 keV), and low Energy band continuum (lEbc 0.8 to 4.0 keV). The measurements were made using the TRoPIC detector (pnCCD), a prototype of the eROSITA cameras, and a high spatial resolution detector (PIXI). The focal plane mapping results show symmetrically distributed Point Spread Functions (PSFs) over the large field of view of ±4.7 degrees of each sector. The effective area results of the energy band continua match well with the theoretical model. We will discuss the test setup, measurements, and results of the full performance of the WXT Flight Mirror module (FM5) tested at PANTER.

In the framework of NewATHENA x-ray space telescope, BEaTriX (Beam Expander Testing X-ray) is the novel ground support equipment designed to perform the Silicon Pore Optics Mirror Modules (SPO MMs) acceptance tests in terms of point spread function and effective area. As of today, the facility built at INAF-Brera Astronomical Observatory in Merate has a first operative beamline at the energy of 4.51 keV. The 170 mm × 60 mm x-ray beam, created by an innovative optical setup, is able to fully illuminate a complete SPO MM in a single exposure with a parallel and monochromatic X-ray beam. The optical chain includes a paraboloidal mirror, with an x-ray source in its focus, that collimates and expands vertically the beam, a monochromatic stage composed by a set of symmetrically cut silicon crystals (the Channel Cut Crystals), and an asymmetrically cut silicon crystal (the Beam Expander) that expands the beam horizontally. To achieve the expected x-ray beam quality in terms of collimation, number of photons and uniformity, the BEaTriX optical components need to be properly aligned. The result of several measurements confirms the theoretical predictions on the behavior of each optical element. This paper describes the work performed to quantify the x-ray beam properties with the adoption of different types of detectors, and alignment sequence, providing the outlook for further optimizations.

Multilayer coatings (MLs) are widely employed for the development of EUV and SXR space-based instrumentation for solar plasma diagnostics since they are the only viable solution for the realization of high-efficiency normal incidence mirrors in this spectral range. Almost all the current missions adopt standard periodic MLs whose reflectance is usually characterized by a high but narrow spectral band. However, future challenges in solar plasma diagnostics require instrumentation with increasingly effective areas and capable of simultaneously observing multiple spectral lines. Fortunately, recent advancement in MLs technology has made the development of new solutions which improve the standard performance achieved so far. For Instance, the possibility to deposit non-periodic stacks with high repeatability and reliability enables the manufacturing of mirrors with either multi-band or broad-band high efficiency. In this work, a study of non-periodic multilayer coatings for the EUV/SXR range is presented, discussing some future perspectives for the next-generation missions.

The NewATHENA mission has been chosen by ESA to cover the topic of “The hot and energetic Universe”. This will be carried out by studying the x-ray Universe with a space-based telescope to be launched in the second half of 2030s. Several materials have been considered as overcoating candidates for the Silicon-Pore Optics (SPO) mirror plates developed for NewATHENA. Previously, carbon did not qualify as an overcoating material since it was not compatible with the manufacturing processes. However, new coatings made in the dedicated chamber for NewATHENA located at cosine Research BV, together with an improvement on the selected cleaning procedure, have shown that carbon is now compatible with the process. This work covers the characterization of the mirror coatings for NewATHENA following a complete and representative wet chemistry process. The primary focus is on the overcoating carbon layer and the hybridisation of the atomic orbitals within its constituent atoms. For the characterization we used X-Ray Reflectometry (XRR) and X-ray Photoelectron Spectroscopy (XPS) techniques. We performed θ−2θ reflectivity measurements at fixed energies of 1.487 keV and 8.048 keV, and at a fixed incident angle of 0.6° from 3.4 to 10.0 keV. We performed Angle Resolved XPS (ARXPS) measurements with an energy of 1.487 keV. We found that both techniques are in agreement showing an sp³ -content on the samples around 20%, indicating a certain level of diamond-likeness. Although it remains unclear if this is the reason for the compatibility of carbon with the manufacturing process, our work shows that the species of carbon grown in the film are able to ensure a good stability of the mirror.

Many current outstanding questions in x-ray astronomy were addressed by Lynx, an observatory concept that concluded its study phase in 2019. High-effective area, high angular resolution x-ray missions like Lynx require thin (≤ 0.5 mm thick) mirrors with precise surface figures to maintain high angular resolution (≤ 0.5 arcsec). To study methods of meeting these requirements, adjustable x-ray optics have been fabricated with thin-film piezoelectric actuators to perform figure correction. These adjustable x-ray optics serve to correct low spatial frequency figure errors (⪆ 0.1 mm⁻¹ ). The fabrication and actuator performance for an adjustable x-ray mirror that forms a conical approximation to a Wolter-I telescope are reported. This mirror has a BCB insulating layer with a top level of Ti traces to address its 288 actuator cells. The individual responses of cells are measured and on average they induce a figure change of 0.87 μm Peak-to-Valley (PV) with an associated Root Mean Square (RMS) of 0.10 μm. These measured cell responses are compared to predicted responses generated using a Finite-Element (FEA) analysis algorithm. On average the measured and predicted cell responses agree to within 0.06 μm RMS. The disagreement between predicted and measured cell responses is posited as being due to differences in radial constraints points between the FEA model and the as-built mirror mount.

Breast imaging using monochromatic x-rays promises lower dose and better image quality relative to conventional approaches. It has been proposed that the use of coated mirrors capable of mono-chromatic x-ray hard spectra have the capability of reducing ionizing radiation exposure while also improving image quality during x-ray medical screening procedures. This research study is centered around screening for breast cancer using Digital Mammography (DM) technique. In this work we present a simplified prototype system developed at DTU Space and implemented to validate the proposed Wolter type I design. The experimental setup consists of a source up to 40 keV, a high-resolution roto-translation mechanical support and an advanced high resolution (55 micron), energy-sensitive Si detector with quantum efficiency (20% @22 keV). For testing, phantom objects will be used as samples, allowing for a real-world realistic assessment of the use of space technology for breast screening. In this work, experimental measurements of absorbed dose reduction and contrast-to-noise ratio are reported.

Current lobster eye telescopes show that it’s possible to produce lightweight, large field of view instruments for observing x-rays for both planetary science and astronomy. Jupiter is the most powerful particle accelerator in the solar system and the other outer planets have intricate and complicated magnetospheres which the moons pass in and out of. Particle bombardment of the surfaces of their moons induces the emission of characteristic x-rays which enables their composition to be studied. An orbiting x-ray instrument would transform our understanding of the moons’ composition, aurorae, atmosphere, radiation belts and plasma tori. Lobster eye telescopes are perfect for this application due to their light weight and wide field of view, which would enable direct imaging of the entire radiation belt. This paper begins to identify a lobster eye telescope design to fulfil these science goals.

The PANTER x-ray test facility of Max Planck Institute for Extraterrestrial Physics is used for calibrating x-ray optics, detectors, and telescopes from Europe and around the world. The 130m x-ray beamline is composed of a long vacuum tube (Ø 1 meter) with a point-like x-ray source on one end and a large vacuum test chamber (12-meter-long, Ø 3.5 meter) on the other end. This work describes the characterization of the x-ray source's stability, including the beam's spectral, temporal, and spatial characteristics during long extensive campaigns, such as a flight module calibration. The beam’s energy spectrum and intensity are monitored continuously with a commercial Amptek Silicon-Drift-Detector (SDD) installed inside the vacuum tube at a distance of 35 meters from the x-ray source. The x-ray optic characterization is conducted by measurements with the TRoPIC pnCCD camera, a prototype of MPE’s eROSITA cameras which is located inside the large chamber. We compare the beam measured by the TRoPIC camera and SDD throughout a long observing time and discuss the correlation of the results and the method of how to derive the beam intensity at any given point in time as measured by TRoPIC. The beam characterization in terms of x-ray source stability and spectral characteristics is performed at relevant energies in the 0.1 to 11 keV range.

High-resolution and large-effective-area x-ray telescopes are critical tools for observing the high-energy universe, but the existing quasi-kinematic and over-constrained mounts for aligning mirrors trade off accuracy and strength. We propose a method to fabricate spacers and bond them between thin mirrors, then adjust mirror alignment by focusing ultrafast laser pulses into these spacers. We built a simple mirror stack assembly composed of two flat mirrors bonded to two spacers and wrote laser-induced modifications into these spacers. We interferometrically measured the air gap between the two mirrors after each set of laser-induced modifications. The resulting deformation in the spacers and measured tilt between flat mirrors shows that realignment can be controlled using the ultrafast laser, however there is uncertainty introduced by imperfect mirror stack assemblies. Future work will aim to achieve predictable laser-induced strain. The presented assembly procedure and laser-strain generation process serves as a potential solution to the optomechanically-limited design of current-generation x-ray telescopes.

X-ray polarization measurements can provide unique information that is complementary to that obtained through spectroscopic or imaging observations. However, there have been few cases where significant x-ray polarization has been observed. XL-Calibur, conducted in collaboration between Japan, the United States of America, and Sweden, is a balloon-borne mission that aims to conduct high-sensitivity polarimetric observations in the hard x-ray band from 15 to 80 keV. The Japanese group is in charge of developing the Hard X-ray Telescope (HXT) with high light-gathering power. Optical adjustments were completed in 2020, and the performance of the HXT was measured in June 2021 at the SPring-8 (synchrotron radiation facility in Hyogo, Japan). Subsequently, in July 2022, the first observation was conducted from Sweden to Canada. After the flight, the HXT was recovered, and we measured its performance again. By comparing the HXT performances before and after the flight, we found no significant changes that can affect the second flight scheduled in 2024.

The Imaging X-ray Polarimetry Explorer (IXPE) is the unprecedented satellite capable of obtaining the x-ray polarization map. To obtain the accurate polarization map for extended sources, the measurements of the Encircled Energy Function (EEF) in flight is necessary. Though it has been often carried out using point-like source, the background may affect the accurate measurements. So, we have investigated the EEF using the data of the Crab pulsar with the nebula, because the background can be accurately removed by subtracting the off-pulse component from the on-pulse component. With the method, we succeeded in obtaining the energy dependence of the EEF.

Technology for a large-area, high-angular resolution mirror module for a future Great Observatory x-ray mission is progressing along different paths. To date, none of these are fully developed. Work at the Marshall Space Flight Center (MSFC) seeks to leverage the benefits of full shell optics while exploring the limits of using shell replication technology for optics production. Here, we provide an updated accounting of spatial-resolution-constraining error terms to give context to recent improvements in MSFC replicated optics, as well as guidance and justification for current and future directions of research and development. Content includes straw-man error allocations for an optical system that is parametrically Lynx-like, where the replicated-optics technology stands relative to these allocations, and methodology for mapping development plans to efficiently identify the limiting factors, and approaches to overcoming these.

The High Energy X-ray Probe (HEX-P) is a probe-class mission concept that combines high spatial resolution x-ray imaging and broad spectral coverage to enable revolutionary new insights into the important astrophysical questions of the next decade. HEX-P will fly a complement of two Hard Energy Mirror Assemblies (HEMA) and one Low Energy Mirror Assembly (LEMA), all of which will have a focal length of 20 meter. Ir/C has been chosen as the baseline coating for the LEMA, and a combination of Pt/C and W/Si multilayers for the HEMA. We present here the mirror design, optimization of coating recipes, and estimated performance.

The High Energy X-ray Probe (HEX-P) is a NASA probe-class mission concept that will combine high spatial resolution x-ray imaging (⪅10 arcsec FWHM) and broad spectral coverage (0.1 to 150 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. Optimized nanometer-thin Ni-based multilayer coatings enable high performance of focusing X-ray telescopes to energies up to 150 keV and beyond, though current fabricated Ni-based coatings contain high interfacial roughness which will affect the predicted performance of the telescope. As part of the thin film coating development for the High Energy X-ray Probe, we report on the current development of reducing the coating roughness in periodic NiV/Si multilayer coatings. The multilayers are fabricated using the direct current magnetron sputtering coating facility at DTU Space, using different types of sputtering collimators and different reactive sputtering gas concentrations, optimized for the production of low interfacial roughness. The multilayers are characterized using x-ray reflectometry and x-ray photoelectron spectroscopy. More information on HEX-P, including the full team list, is available at hexp.org.