KEYWORDS: Chromium, Film thickness, Coating stress, Thin films, Thin film coatings, Design, Data modeling, Surface roughness, Reflectivity, Data acquisition
NewAthena (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.
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.
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.
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 Lclass mission, to launch around 2037. NewAthena’s optic is modular and consists of up to 600 mirror modules that form together a ~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 ~300 m2, 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.
The ALBA Synchrotron (Barcelona, Spain) has built MINERVA a new X-ray facility designed to support the development of the NewATHENA mission (Advanced Telescope for High Energy Astrophysics), whose objective is to observe and study energetic objects in space (accretion disk around black holes, large-scale structure, etc...). MINERVA is dedicated to assemble stacks manufactured by cosine into mirror modules (MM), building blocks of the NewATHENA optics. This new beamline is originally based on the X-ray parallel beam facility XPBF 2.0 at the Physikalisch-Technische Bundesanstalt (PTB at BESSY II) but also includes additional features on the scanning scheme to improve the characterization time of each MM produced. Interoperability between MINERVA and XPBF 2.0 is nonetheless preserved to boost the mass production of the MMs and characterize their performance. MINERVA is now in operation and has been funded by the European Space Agency (ESA) and the Spanish Ministry of Science and Innovation.
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.
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.
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. Additional presentation content can be accessed on the supplemental content page.
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 m2 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.
It has been known for some time that sputtered low-density coatings deposited under vacuum (e.g. carbon or B4C), applied on top of high-density metallic coatings, can enhance the reflectivity in the soft x-ray band (below ~5 keV). In the last years, we experimented with novel carbonated coatings obtained by dip-liquid deposition, in which a thin film is formed on the surface of a mirror by immersion in a suitable precursor solution. After several attempts with different chemical compounds, we found an optimal candidate both for the reflectivity performance and for the convenience of the deposition process, which is much simpler and inexpensive compared to conventional processes. In particular, such coatings can enhance the soft x-ray response at the reflection angles employed in future telescopes, like ATHENA (ESA), Lynx (NASA) and eXTP (CAS). In this paper we consider the application of dip-liquid overcoatings on conventional coatings (Au, Ir) or in combination with recently proposed chromium overcoatings and their possible uses to enhance the reflectivity of x-ray mirrors at low, medium or higher energies, presenting the first experimental results of x-ray tests on these coatings.
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.
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