Focusing high-energy photons above 80 keV remains a significant challenge due to the absorption edges of conventional high-Z thin film materials such as W, Ir, Pt, and Au, which lead to substantial reflectance losses above this energy. In this work, we introduce a novel approach, to our knowledge, for fabrication of Ni-based thin film multilayers, deposited by DC magnetron sputtering, offering efficient reflection of photon energies beyond 80 keV. These coatings were characterized using XRR at 8.048 keV with a laboratory X-ray source and at synchrotron beamlines. Structural and morphological characterization of the layers was carried out by STEM and XPS. Furthermore, we produced depth-graded multilayers of Ni and W and successfully integrated them into hybrid structures, advancing a concept originally proposed for focusing light up to the sub-MeV range. These promising results have applications not only in astronomical telescope optics but also in synchrotron beamline instrumentation.

With the endorsement of the NewAthena (New Advanced Telescope for High ENergy Astrophysics) mission by ESA's Science Programme Committee in November 2023, the preparations for this next generation X-ray observatory have shifted to a higher gear. Competitive system studies and technology preparation activities are being implemented, aiming to demonstrate readiness for the mission adoption early 2027 and the subsequent mission implementation. The Silicon Pore Optics (SPO) enables the NewAthena mission, delivering an unprecedented combination of good angular resolution, large effective area and low mass. The SPO technology builds significantly on spin-in from the semiconductor industry and is designed to allow a cost-effective flight optics implementation, compliant with the programmatic requirements of the mission. The NewAthena X-ray optics is highly modular, consisting of hundreds of compact mirror modules arranged in concentric circles and mounted on a metallic optical bench. All aspects of the optics are being developed in parallel, from the industrial production of the mirror plates, over the highly efficient assembly into mirror modules, to the alignment of the mirror modules and their fixation on the optical bench. Dedicated facilities are being built to measure the performance of the NewAthena X-ray telescope optics, demonstrating their compatibility with the environmental and scientific requirements. An overview is provided of the activities preparing the implementation of the NewATHENA optics.

Grazing-incidence X-ray optics have revolutionized X-ray astrophysics. The ability to concentrate flux to a tiny detection region provides a dramatic reduction in background and a consequent very large improvement in sensitivity. The X-ray optics also permit use of small-format, high-performance focal plane detectors and, of course, especially for high-angular-resolution optics, provide a wealth of imaging data from extended sources. This review, follows the use of X-ray optics from the first rocket-borne instruments in the 1960s through to the Observatories flying today and being developed for future use. It also includes a brief overview of the challenges of fabricating X-ray optics and the various technologies that have been used to date

This work investigates the importance of substrate quality and contamination of thin film coatings, essential for high-energy reflective mirrors used in astronomical missions and other applications, focusing on the manufacturing process from substrate selection to final assembly of the optics. Characterization of thin film coatings is crucial for evaluating the performance of X-ray mirrors. Multifaceted and synergized methodologies utilizing Xray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS) and optical microscopy (OM) are presented. Herein, we discuss coating performance, encompassing substrate preparation, coating deposition, and storage conditions. XRR scans provide detailed insights into thin film properties, however, the dependence on accurate a priori knowledge necessitates a robust model for solving the inverse problem. Addressing this limitation, XPS proves invaluable in revealing the chemical composition of thin films, improving the accuracy of the XRR model. Combined characterization through OM and XRR is very useful to find visual insights into surface contamination-induced changes when mirrors are stored for long periods in a clean room environment, as might be the case for some astronomical missions. The synergy among these techniques is pivotal for evaluating coating quality for high-energy astronomical telescopes, with a specific focus on NewAthena and upcoming missions. This research not only advances methodologies in this field but also highlights the collaborative power of XRR, XPS, and OM in providing a comprehensive understanding of thin film coatings, emphasizing the importance of pre-coating mirror quality and mitigating contamination effects throughout the optics production process to ensure optimal performance.

The European Space Agency (ESA), cosine and its partners have been developing for 20 years the Silicon Pore Optics (SPO) technology. SPO enables the next generation of space x-ray telescopes, with increased sensitivity and resolution. NewAthena, the New Advanced Telescope for High Energy Astrophysics, has just been endorsed by ESA as one of its L-class mission, to launch around 2037. NewAthena's optic is modular and consists of up to 600 mirror modules that form together a similar to 2.5 m diameter X-ray mirror with a focal length of 12 m and an angular resolution of 9 arc-seconds half-energy width. The total polished mirror surface is similar to 300 m(2), which will focus X-rays with an energy of about 0.3 - 10 keV onto two detectors, a wild-field imager (WFI) and an imaging spectrometer ( XIFU). Building hundreds of such SPO mirror modules in a cost-efficient and timely manner is a formidable task and subject of a dedicated ESA technology development program. 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.

New Athena (New Advanced Telescope for High-Energy Astrophysics) has been endorsed by the European Space Agency in November 2023 and the mission is entering a pre-industrialization phase prior to the foreseen adoption early 2027. A key aspect of the thin film coating development for the NewATHENA X-ray optics, is to determine the adhesion efficiency and the residual stress limitation of the coatings on silicon substrates. To do so, we magnetron sputtered different layer thicknesses of chromium layers underneath iridium/carbon bilayer and linear graded multilayer coatings. The samples were characterized using X-ray Reflectometry (XRR) to derive the thickness and micro-roughness. The residual stress was assessed by profilometry using a Dektak 150 stylus profilometer. The curvature of the samples before and after coating, along with the total film thickness derived from XRR, was used to evaluate the residual stress.

High-energy astrophysics missions demand cutting-edge technologies to assure their maximum observational capabilities. This study explores multilayer coatings for X-ray mirrors, specifically assessing their potential applications for the NewAthena mission and other possible future high-energy missions. Our work emphasizes the design parameters crucial for enhancing mirror performance and investigates the experimental challenges related to the fabrication and performance evaluation of multilayer coatings. We present various concept designs for both soft and hard X-ray focusing telescopes, incorporating simple single-layer and bilayer coatings, with a particular focus on linear and depth-graded multilayer coatings. Leveraging state-of-the-art understanding and modeling of relevant effects influencing telescope performance enables a realistic extension of coating designs to higher energies. The implications of our findings not only endorse the use of multilayer coatings for the NewAthena mission but also offer insights into the broader landscape of future high-energy astrophysics missions.

Development and qualification of X-ray reflective mirror coatings for the NewAthena mission is progressing with a focus on enabling scientific capabilities of the telescope, given the updated requirements of the redefined mission. In this work, we consider both design and development of Ir/C multilayer coatings optimised to ensure the required performance across the spectral range, facilitating the mission science objectives. We present demonstration of manufacturing capability for the optimised Ir/C multilayer coatings, and compatibility with the Silicon Pore Optics (SPO) technology. Characterisation of X-ray mirror coatings is performed using X-ray reflectometry with a focus on mirror design qualification and long-term stability.

The ATHENA (Advanced Telescope for High ENergy Astrophysics) mission is the current 2nd 'Large' mission (L2) in the ESA Cosmic Vision programme currently.It is currently at Phase B1 but the mission concept will now enter a reformulation phase that will follow a design-to-cost approach.This paper describes the main technologies behind its reference X-ray telescope based on the modular Silicon Pore Optics (SPO) technology.The large X-ray mirror is the mission enabler being specifically developed for ATHENA, in a joint effort by industry, research institutions and ESA.All aspects of the optics are being addressed, from the mirror plates and their coatings to the mirror modules and their assembly into the ATHENA telescope, as well as the facilities required to build and test the flight optics, demonstrating performance, robustness, and programmatic compliance.An overview of the status of the design and demonstration of the telescope is given.The risks that have successfully been mitigated are made explicit and the remaining risks are identified.

The future Athena observatory will feature optics with unprecedented collecting area enabled by Silicon Pore Optics technology. In order to achieve the telescope effective area requirements at 1 keV and 7 keV, thin film coatings of iridium with a low-density overcoat are deposited onto the mirror substrates. Assembling the coated silicon pore optics plates into mirror modules for the Athena optics requires wet chemical processing and thermal annealing. While iridium appears to be compatible with the post-coating processes, previous studies have shown degradation of the low-density material. The overcoat layer is particularly critical for the low-energy telescope performance, so several candidate materials (boron carbide, silicon carbide and carbon) have been studied to identify a compatible thin film design. We present the characterisation of X-ray mirror performance using X-ray reflectometry, as well as the measurements of residual film stress with stylus profilometry. Furthermore, we evaluate the effects of post-coating treatment in order to recommend the most suitable overcoat material for the telescope.

The next generation x-ray observatory ATHENA (advanced telescope for high energy astrophysics) requires an optics with unprecedented performance. It is the combination of low mass, large effective area and good angular resolution that is the challenge of the x-ray optics of such a mission. ATHENA is the second large class mission in the science programme of ESA, and is currently in a reformulation process, following a design-to-cost approach to meet the cost limit of an ESA L-class mission. The silicon pore optics (SPO) is the mission enabler being specifically developed for ATHENA, in a joint effort by industry, research institutions and ESA. All aspects of the optics are being addressed, from the mirror plates and their coatings, over the mirror modules and their assembly into the ATHENA telescope, to the facilities required to build and test the flight optics, demonstrating performance, robustness, and programmatic compliance. The SPO technology is currently being matured to the level required for the adoption of the ATHENA mission, i.e., the start of the mission implementation phase. The monocrystalline silicon material and pore structure of the SPO provide these optics with excellent thermal and mechanical properties. Benefiting from technology spin-in from the semiconductor industry, the equipment, processes, and materials used to produce the SPO are highly sophisticated and optimised.

Nanometer-thin multilayer coatings can enable high performance of focusing X-ray telescopes to energies up to 200 keV and beyond. In this paper we discuss the multilayer parameters and their limitations necessary for the reflection of hard X-ray photons. We present several multilayer coating designs that are optimized with a Differential Evolution algorithm to perform a stochastic global search of the multi-parametric model space. The coating designs are based on the new specifications of the HEX-P mission geometry, optimizing within the energy range 60 keV - 200 keV. We compare the simulated reflectivity spectra of Si/Ni, Si/Pt and Si/W, at different incident angles. We find the effective upper limit of bilayers in the multilayer stack, beyond which reflectivity will not be increased. We discuss a hybrid multilayer coating design, consisting of either a Si/Pt or Si/W multilayer with a top Si/Ni multilayer.

The thin film deposition technology for fabrication of the mirror optics for the Advanced Telescope for HighEnergy Astrophysics (ATHENA) has been established. Numerous coating process parameters impact the quality of the thin films. Defining a margin within the coating process parameter space, where the deposited thin film performs similar in X-ray reflectivity is key to avoid unforeseen risks within the coating process for the ATHENA flight optics production. In this work, we investigate the coating process parameter influence on the thin film properties with a focus on micro roughness, deposition rate and residual film stress when deposited under various process conditions. The thin films were produced by varying the following three coating process parameters: discharge power, discharge voltage and working gas pressure. The thin films were characterized using X–ray reflectometry at 3.4–10.0 keV. A main result of this work is that the residual stress of single layer iridium and boron carbide films can be reduced by a factor of approximately two, by increasing the working gas pressure while maintaining a high film quality.

Athena is the European Space Agency's next flagship telescope, scheduled for launch in the 2030s.Its 2.5 m diameter mirror will be segmented and comprise more than 600 individual Silicon Pore Optics (SPO) mirror modules.Arranged in concentric annuli and following a Wolter-Schwartzschild design, the mirror modules are made of several tens of grazing incidence primary-secondary mirror pairs, each mirror made of silicon, coated to increase the effective area of the system, and shaped to bring the incoming photons to a common focus 12 m away.The mission aims to deliver a half-energy width of 5" and an effective area of about 1.4 m 2 at 1 keV.We present the status of the optics technology, and illustrate recent X-ray results and the progress made on the environmental testing, manufacturing and assembly aspects of the optics.

Abstract. We measured the reflectivity of an Athena silicon pore optics sample coated with 10-nm thick iridium near the iridium L-edges (L3  ,  L2, and L1) in a step of 1.5 eV. The derived atomic scattering factor f2 was similar to a shape of the absorption coefficient μ near L3 and L2 obtained by previous x-ray absorption spectroscopy (XAS) measurements. The fine structures of f2 of L3 and L2 can be represented by a strong sharp line referred to as a white line (WL) and two weak lines at center energies of ∼17 and ∼31  eV from each edge energy. The branching ratio (L3  /  L2) of the WL is >2, which reflects the initial core-electron states available for the L2 (2p1/2) and L3 (2p3/2) processes, and the ratio remains high to the energy of +7  .  5  eV from WL. The fine structure seen in L1 also has two weak lines, which were seen in XAS at L1-edge. Our measurements near L3, L2, and L1 edges demonstrated a different technique to provide atomic structural information as XAS. The ground calibration to measure fine structures near the edges may potentially be simplified using f2 estimated based on μ.

Athena, the largest space-based x-ray telescope to be flown by the European Space Agency, uses a revolutionary new modular technology to assemble its 2.6 m diameter lens. The lens will consist of several hundreds of smaller x-ray lenslets, called mirror modules, which each consist of about 70 mirror pairs. Those mirror modules are arranged in circles in a large optics structure and will focus x-ray photons with an energy of 0.5 to 10 keV at a distance of 12 m onto the detectors of Athena. The point-spread function (PSF) of the optic shall achieve a half-energy width (HEW) of 5” at an energy of 1 keV, with an effective area of about 1.4 m2, corresponding to several hundred m2 of super-polished mirrors with a roughness of about 0.3 nm and a thickness of only 150 µm. Silicon Pore Optics (SPO), using the highest grade double-side polished 300 mm wafers commercially available, have been invented to enable such telescopes. SPO allows the cost-effective production of high-resolution, large area, x-ray optics, by using all the advantages that mono-crystalline silicon and the mass production processes of the semi-conductor industry provide. SPO has also shown to be a versatile technology that can be further developed for gamma-ray optics, medical applications and for material research. This paper will present the status of the technology and of the mass production capabilities, show latest performance results and discuss the next steps in the development.

The mirror coatings for the Athena X-ray telescope assumes Ir/SiC bilayer thin films as a baseline design. Adding the soft overcoat to the Ir X-ray mirror coatings for the Athena optics is used to improve the low energy performance necessary to achieve the telescope effective area requirements. The Athena mirror is based on silicon pore optics technology, for which the manufacturing process involves a sequence of wet chemical and thermal post-coating treatments of the mirror plates. Establishing compatibility of the thin film material candidates following exposure to these processes is critical for the Athena mission since the specific coating quality will influence the performance of the X-ray telescope. We present an investigation of Ir and Ir/SiC thin films exposed to post-coating treatments based on coatings produced at DTU Space. The current status of the chemical procedures is presented with representative coatings from the Athena-dedicated coating facility.