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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 (0.1−150 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.

The BEaTriX (Beam Expander Testing X-ray) facility, now operational at INAF-Brera Astronomical Observatory, will represent a cornerstone in the acceptance roadmap of Silicon Pore Optics (SPO) mirror modules, and will so contribute to the final angular resolution of the ATHENA X-ray telescope. By expansion and collimation of a microfocus X-ray source via a paraboloidal mirror, a monochromation stage, and an asymmetric crystal, BEaTriX enables the full-aperture illumination of an SPO mirror module with a parallel, monochromatic, and broad (140 mm ´ 60 mm) X-ray beam. The beam then propagates in a 12 m vacuum range to image the point spread function of the mirror module, directly on a focal plane camera. Currently the 4.51 keV beamline, based on silicon crystals, is operational in BEaTriX. A second beamline at 1.49 keV, which requires a separate paraboloidal mirror and organic crystals (ADP) for beam expansion, is being realized. As for monochromators, the current design is based on asymmetric quartz crystals. In this paper, we show the current optical design of the 1.49 keV beamline and the optical simulations carried out to predict the achievable performances in terms of beam collimation, intensity, and uniformity. In the next future, the simulation activity will allow us to determine manufacturing and alignment tolerances for the optical components. Additional presentation content can be accessed on the supplemental content page.

BEaTriX (Beam Expander Testing X-ray facility) is the new facility available at the INAF-Osservatorio Astronomico Brera (Merate, Italy) for the calibration of X-ray optics. Specifically designed to measure the point spread function (PSF) and the effective area (EA) of the mirror modules (MM) of the ATHENA X-ray telescope at their production rate, BEaTriX gives the unique possibility to test the optics with a source that approximate an astronomical source, i.e. with a large, parallel X-ray beam (170 × 60 mm2) that fully covers the entrance pupil of the MM. For a fast and precise testing, BEaTriX is a compact facility (9 × 18 m2) with fast vacuum pump-down (to 10-6 mbar), and an optical setup able to create the X-ray beam with a residual divergence of about 2-3 arcsec, HEW, and with a flux of 60 photons/s/cm2. The first beam line at the energy of 4.51 keV is now operative, and a second beam line, working at the energy of 1.49 keV, will be implemented in the coming future. The unique characteristics of the BEaTriX X-ray beam are obtained with an X-ray microfocus source placed in the focus of a paraboloidal mirror, a monochromation stage with 4 symmetrically cut crystals, and an expansion stage where the beam is diffracted and expanded by an asymmetrically-cut crystal. The beam, reflected by the MMs, is then imaged at 12 m distance, where a directly-illuminated CCD camera is placed. This paper presents the facility, the calibration of the beam and the latest results with the ATHENA MMs.

BEaTriX (Beam Expander Testing X-ray) is the compact (18m × 9m) X-ray facility being implemented at INAF for the acceptance tests of the ATHENA Silicon Pore Optics Mirror Modules (MM) working at the two energies of 1.49 and 4.51 keV. It adopts an innovative design based on a collimating mirror and Bragg crystals in proper configuration to provide a large and parallel beam. The 4.51 keV line provides a parallel beam with 170 mm x 60 mm size and it has been calibrated and characterized in term of intensity, uniformity, divergence and stability. This paper traces the path taken for the best-achieved alignment of the different optical components, from the preliminary phases to the final step where the function of merit was obtained directly from the parallel beam itself. The alignment method used a combination of optical and mechanical tools: laser tracker, micro-alignment telescope (MAT), 3D measuring machine (CMM) and self-designed holed plates. The final characterization of the X-ray beam is presented.

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 BEaTriX (Beam Expander Testing X-ray) facility is now operative at the INAF-Osservatorio Astronomico Brera (Merate, Italy). This facility has been specifically designed and built for the X-ray acceptance tests (PSF and Effective Area) of the ATHENA Silicon Pore Optics (SPO) Mirror Modules (MM). The unique setup creates a parallel, monochromatic, large X-ray beam, that fully illuminates the aperture of the MMs, generating an image at the ATHENA focal length of 12 m. This is made possible by a microfocus X-ray source followed by a chain of optical components (a paraboloidal mirror, 2 channel cut monochromators, and an asymmetric silicon crystal) able to expand the X-ray beam to a 6 cm × 17 cm size with a residual divergence of 1.5 arcsec (vertical) × 2.5 arcsec (horizontal). This paper reports the commissioning of the 4.5 keV beam line, and the first light obtained with a Mirror Module.

ESA’s Athena mission will use silicon pore optics, in which the optics assembly consists of pairs of mirror plates stacked into mirror modules. This paper presents a study of the angular resolution of Athena, using several candidate variants of mirror curvature and wedging. Results were achieved by ray-tracing these variants of Athena’s optics with the ray-tracing software SPORT. The study shows that all polynomial variants yield a PSF below 1” on-axis, at all energies between 0.1 and 12 keV. The secondary-only polynomial variants perform best, for both on- and off-axis point sources. Of these variants, the wedging 0/2 variant is shown to generally yield superior angular resolution at higher energies, the -1/1 variant at lower energies. A ray-tracing analysis using the Crab Nebula as an observation target was also performed. A 2D Fourier analysis was applied to the resulting focal plane responses to determine their angular resolution. This analysis indicates the angular resolution of all polynomial variants to be below 1”, at all but the highest energies. It also shows, though to a lesser extent, that the secondary-only polynomial variants perform best in most circumstances. Nevertheless, this second analysis requires further investigation for a more conclusive outcome.

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.

The thin film coating technology for the European Space Agency mission, Advanced Telescope for High-Energy Astrophysics (Athena) has been established. The X-ray optics of the Athena telescope is based on Silicon Pore Optics (SPO) technology which is enhanced by the thin film coatings deposited on the reflective surface of the SPO plates. In this work, we present a literature study of the coating process parameter space and provide an overview of the thin film properties with a focus on micro roughness, chemical composition and wear resistance when deposited under various process conditions. We determined, that the thin film density depends strongly on the mobility of the adatoms on the substrate surface. Some coating process parameters, which have a significant impact on the adatom mobility are the discharge voltage, the working gas pressure and the substrate temperature.

The development of high-quality thin film coatings for the Athena X-ray optics is progressing, following the commissioning of an industrial scale coating facility. The assembly of silicon pore optics into mirror modules for the Athena telescope requires wet-chemical exposure of coated mirror plates to prepare bonding areas for stacking, as well as an annealing step to improve bond strength. It is therefore critical to evaluate how these post-coating processes could affect the mirror coating performance and stability. We present X-ray reflectometry characterization of iridium thin films deposited on photoresist patterned Silicon Pore Optics plates to investigate the compatibility with the stacking process steps for the manufacturing of the Athena optics.

BEaTriX (Beam Expander Testing X-ray) is the X-ray facility under construction at the INAF-Osservatorio Astronomico Brera (Merate, Italy) to prove that it is possible to perform the X-ray acceptance tests (PSF and Aeff) of the ATHENA mirror modules at the required rate and with the required accuracy. The unique optical setup makes use of a micro-focus X-ray source with anode in Titanium, a paraboloidal mirror with small radius of curvature, and a set of crystals to monochromate and expand the beam to fully illuminate the entrance pupil of the ATHENA MMs. The quality of the optical components, and their precise alignment, guarantees the production of a parallel beam at 4.51 keV, to be extended in a second phase to 1.49 keV in order to complete the acceptance requirements for the ATHENA MMs. The completion of the facility is expected to occur in July this year, while the commissioning will start in September. In this paper, we present the current status.

We present a teaching concept which combines theory, experimental work, project management and organization. As part of the Earth and Space Physics and Engineering education at DTU Space, a group of first year undergraduate students were given the task to design, build and test a DC magnetron sputtering system within a very limited budget and time frame. The teaching concept is designed to promote the students' autonomous learning, and a major part of the project was to teach the students how to develop group dynamics successfully. The students successfully managed to build a direct current magnetron sputtering system wherein a plasma glow was produced. The system can be used for depositing thin film coatings, an enabling technology for numerous applications.

As part of the manufacturing process of mirror modules for the Athena X-ray telescope, Silicon Pore Optics plates are assembled into mirror module stacks. The plates that form each stack are held together by direct bonding, relying on van der Waals forces and covalent bonds for adhesion. One way to increase the strength of the covalent bonds is through annealing of the mirror stacks. It is of critical importance to the mission to ensure compatibility between the reflective coating and any post-coating processing of the plates. We present our findings of the impact of annealing on the X-ray re ectance of coated mirrors relevant for the Athena mission. These are Ir single layers, as well as Ir/B4C, Ir/SiC, and Ir/C bilayers. We investigate the effect on the performance of the coatings after annealing at atmospheric pressure and at a low vacuum using X-ray reflectometry. B4C is found to suffer degradation from annealing under atmospheric conditions but not when annealed in vacuum. All other materials investigated are robust to atmospheric annealing.

The BEaTriX (Beam Expander Testing X-ray) facility under construction at INAF-Brera Astronomical Observatory aims at performing the acceptance tests of the Silicon Pore Optics mirror modules of the ATHENA (Advanced Telescope for High-ENergy Astrophysics) X-ray observatory. The facility implements a grazing-incidence collimating mirror that, together with a monochromator and a beam expander stages based on crystals, enables the full X-ray illumination of the mirror modules under test. We present the development and test of the collimating mirror, a paraboloid sector having an optical surface of 400 mm -60 mm and sagittal radii of about 155 mm. The ground and lapped optics made of HOQ 310 fused quartz was corrected by bonnet polishing. In this paper, we report on the smoothing of mid-to-high spatial frequency error by pitch-tool polishing process, and on the correction of residual surface shape errors by ion-beam figuring process, both performed at INAF-Brera Astronomical Observatory. We present the X-ray test campaigns carried out on the mirror at PANTER facility, before and after coating it with a Pt layer via magnetron sputtering at DTU Space. The results provide an overview of the mirror performance in terms of angular resolution pre- and post-coating deposition.

The Advanced Telescope for High ENergy Astrophysics (Athena) is a Cosmic Vision L-class mission of the European Space Agency selected for launch in the early 2030s1. The observatory features a single X-ray telescope with a 12 m focal length. The focusing Wolter-I optics is based on Silicon Pore Optics (SPO) technology2. The Athena science objectives require a high performance in the 0.3-12 keV range which is obtained with X-ray reflective thin films.

We present an experimental examination of iridium and boron carbide thin-film coatings for the purpose of fabricating x-ray optics. We use a combination of x-ray reflectometry and x-ray photoelectron spectroscopy to model the structure, composition, density, thickness, and micro-roughness of the thin films. We demonstrate in our analyses how the two characterization techniques are complementary, and from this we derive that an overlayer originating from atmospheric contamination with a thickness between 1.0–1.6 nm is present on the surface. The magnetron sputtered iridium films are measured to have a density of 22.4g/cm3. The boron carbide film exhibits a change in chemical composition in the top ∼2nm of the film surface when exposed to the ambient atmosphere. The chemical reaction occurring on the surface is due to an incorporation of oxygen and hydrogen present in the ambient atmosphere. Lastly, we present a correlation between the absorption edges and the emission lines exhibited by the thin films in an energy range from 50–800 eV and the impact on the reflectivity performance due to contamination in thin films.

As part of the thin film development for the Athena X-ray telescope and X-ray optics in general, we investigated the residual stress in iridium and chromium thin films deposited using direct current magnetron sputtering. Residual stresses in thin films can affect the performance and adhesion properties of the fabricated thin film coated X-ray optics. We characterized the thin films using X-ray reflectometry to determine the thin film thicknesses and stylus profilometry to determine the residual film stresses. To counterbalance the compressive stress identified in the iridium thin films, we introduced a chromium thin film layer for which the residual stress is tensile beneath the iridium film. However, chromium thin films are known to exhibit a grainy growth resulting in a high surface roughness which was also observed in this work. In this paper, we evaluated the effect on the iridium surface roughness when introducing a chromium underlayer and discussed the effect on the X-ray optics performance.

The demand for X-ray optics increases and so do their performance requirements. Iridium (Ir) thin film coatings have proven to be very robust and exhibit excellent reflective properties within the X-ray regime. However, the residual stress in Ir thin films is high and studies show that thin film Ir coatings with a thickness of 10–30 nm exhibit residual compressive stress1 as illustrated in Figure 1.

With a number of upcoming spaceborne and ground-based observatories equipped with X-ray telescopes that rely on high throughput at low energies, it is crucial to characterize these optics at the relevant energies to obtain a detailed understanding of their behavior and performance. DTU Space has commissioned a state-of-the-art Low-Energy X-ray Reflectometer (LEXR) with the purpose of studying thin-film performance of especially low-Z X-ray coatings.

A state-of-the-art Low-Energy X-ray Reflectometer (LEXR) is in operation at DTU Space with the main purpose of characterizing coatings for the Advanced Telescope for High-ENergy Astrophysics (ATHENA), a selected Lclass ESA mission. In particular, soft materials are difficult to characterize at higher energies so the 1.487 keV beamline compliments our existing 8.048 keV reflectometer, allowing for a more complete understanding of thinfilm X-ray characteristics. Documenting and qualifying the as-deposited coatings for X-ray telescope optics is of crucial importance, both to ensure that the effective area requirements are met, but also to quantify any temporal evolution in coating characteristics as well as the impact of manufacturing process parameters on mirror performance. It is notably relevant in the case of ATHENA, as there is a desire to enhance the low-energy performance by using a low-Z material overcoating on top of the Ir coating. We report on the commissioning and qualify the performance of the as-built 1.487 keV reflectometer as well as discuss measurement repeatability and system limitations

Ischemia-reperfusion (I/R) is a condition leading to serious complications due to death of cardiac myocytes. We used the cardiomyocyte-like cell line H9c2 to study the mechanism underlying cell damage. Exposure of the cells to simulated I/R lead to their apoptosis. Over-expression of Bcl-2 and Bcl-xL protected the cells from apoptosis while over-expression of Bax sensitized them to programmed cell death induction. Mitochondria-targeted coenzyme Q (mitoQ) and superoxide dismutase both inhibited accumulation of reactive oxygen species (ROS) and apoptosis induction. Notably, mtDNA-deficient cells responded to I/R by decreased ROS generation and apoptosis. Using both in situ and in vivo approaches, it was found that apoptosis occurred during reperfusion following ischemia, and recovery was enhanced when hearts from mice were supplemented with mitoQ. In conclusion, I/R results in apoptosis in cultured cardiac myocytes and heart tissue largely via generation of mitochondria-derived superoxide, with ensuing apoptosis during the reperfusion phase. © W. S. Maney & Son Ltd.

a-Tocopheryl succinate (a-TOS) is a semisynthetic vitamin E analogue with high pro-apoptotic and anti-neoplastic activity [Weber, T et al. (2002) Clin. Cancer Res. 8, 863-869]. Previous studies suggested that it acts through destabilization of subcellular organelles, including mitochondria, but compelling evidence is missing. Cells treated with a-TOS showed altered mitochondrial structure, generation of free radicals, activation of the sphingomyelin cycle, relocalization of cytochrome c and Smac/Diablo, and activation of multiple caspases. A pan-caspase inhibitor suppressed caspase-3 and -6 activation and phosphatidyl serine externalization, but not decrease of mitochondrial membrane potential or generation of radicals. For a-TOS, but not Fas or TRAIL, apoptosis was suppressed by caspase-9 inhibition, while TRAIL- and Fas-resistant cells overexpressing cFLIP or CrmA were susceptible to a-TOS. The central role of mitochondria was confirmed by resistance of mtDNA-deficient cells to a-TOS, by regulation of a-TOS apoptosis by Bcl-2 family members, and by anti-apoptotic activity of mitochondrially targeted radical scavengers. Co-treatment with a-TOS and anti-Fas IgM showed their cooperative effect, probably by signaling via different, convergent pathways. These data provide an insight into the molecular mechanism, by which a-TOS kills malignant cells, and advocate its testing as a potential anticancer agent or adjuvant.

Modified low-density lipoprotein (LDL) has been implicated as an initiating or amplifying factor in atherogenesis. Some of its biological activities, such as apoptosis induction and upregulation of the scavenger receptor CD36, appear to share common signaling pathways in cells of the cardiovascular system. Exposure of low-differentiated monocytic cells to LDL modified with 15-lipoxygenase and secretory phospholipase A(2) induced apoptosis and upregulated CD36. Cell treatment with constituents of modified LDL, such as 13-hydroxyoctadecadienoic acid (13-HODE), 25-hydroxycholesterol, and lysophosphatidyl choline, and with an unrelated apoptogen (TNF-related apoptosis-inducing ligand) induced apoptosis. In contrast, only 13-HODE caused upregulation of CD36 expression. Cotreatment with the pan-caspase inhibitor z.VAD-fmk resulted in suppression of apoptosis, but was without any effect on CD36 expression. These data indicate that in monocytic cells enzymatically modified LDL is capable of inducing both apoptosis and upregulation of CD36 expression. However, in our cellular model, the two induction processes appear to be causally unrelated. (C) 2002 Elsevier Science (USA).

Generation of free radicals is often associated with the induction and progression of apoptosis. Therefore, antioxidants can prove anti-apoptotic, and can help to elucidate specific apoptotic pathways. Here we studied whether coenzyme Q, present in membranes in reduced (ubiquinol) or oxidised (ubiquinone) forms, can affect apoptosis induced by various stimuli. Exposure of Jurkat cells to a-tocopheryl succinate (a-TOS), hydrogen peroxide, anti-Fas IgM or TRAIL led to induction of apoptosis. Cell death due to the chemical agents was suppressed in cells enriched with the reduced form of coenzyme Q. However, coenzyme Q did not block cell death induced by the immunological agents. Ubiquinol-10 inhibited reactive oxygen species (ROS) generation in cells exposed to a-TOS, and a mitochondrially targeted coenzyme Q analogue also blocked apoptosis triggered by a-TOS or hydrogen peroxide. Therefore, it is plausible that ubiquinol-10 protects cells from chemically-induced apoptosis by acting as an antioxidant in mitochondria. Our results also indicate that generation of free radicals may not be a critical step in induction of apoptosis by immunological agents. © 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

The vitamin E analog a-tocopheryl succinate (a-TOS) can induce apoptosis. We show that the proapoptotic activity of a-TOS in hematopoietic and cancer cell lines involves inhibition of protein kinase C (PKC), since phorbol myristyl acetate prevented a-TOS-triggered apoptosis. More selective effectors indicated that a-TOS reduced PKCa isotype activity by increasing protein phosphatase 2A (PP2A) activity. The role of PKCa inhibition in a-TOS-induced apoptosis was confirmed using antisense oligonucleotides or PKCa overexpression. Gain- or loss-of-function bcl-2 mutants implied modulation of bcl-2 activity by PKC/PP2A as a mitochondrial target of a-TOS-induced proapoptotic signals. Structural analogs revealed that a-tocopheryl and succinyl moieties are both required for maximizing these effects. In mice with colon cancer xenografts, a-TOS suppressed tumor growth by 80%. This epitomizes cancer cell killing by a pharmacologically relevant compound without known side effects.