X-ray Astrophysics (7)

X-ray reverberation in Active Galactic Nuclei, believed to be the result of the reprocessing of coronal photons by the underlying accretion disc, has allowed us to probe the properties of the inner-most regions of the accretion flow and the central black hole. Our current model (KYNXILREV) computes the time-dependent reflection spectra of the disc as a response to a flash of primary power-law radiation from a point source corona located on the axis of the black hole accretion disc (lamp-post geometry). Full relativistic effects are taken into account. The ionization of the disc is set for each radius according to the amount of the incident primary flux and the density of the accretion disc. In this work we apply the latest version of the code for reverberation to the most (continuously) observed Seyfert-1 AGN with XMM-Newton, that is IRAS 13224-3809. This is probably the best source for tackling the use of reverberation codes but it is also an extremely variable one. The latter makes the analysis of separate datasets necessary, because of its important spectral state evolution.

We further study the mechanism of efficient acceleration of particles near a rotating black hole. We show the onset of chaos and the enhanced Lorentz factors that are achieved by particles escaping in the non-axisymmetric geometry of the magnetic field inclined with respect to the rotation axis. Besides the strong gravity of the massive source, which is represented by Kerr metric, we consider the presence of a weak, ordered, large-scale magnetic field. An axially-symmetric model consisting of a rotating black hole embedded in an aligned magnetic field is generalized by allowing an oblique direction of the field having a general inclination, with respect to the rotation axis of the system. The inclination of the field acts as an additional important aspect that influences the motion of charged particles as it breaks the axial symmetry of the system and cancels the related integral of motion.

Studying charged fluids circling in strong gravitational and magnetic fields, we can find them forming various interesting equilibrium structures. As simple toroidal structures (tori) settled in the equatorial plane, they mimic standard equatorial thick accretion discs with negligible loss of mass. However, thanks to the proper combination of gravitational and electromagnetic interactions, it turns out that the structures can also hover about the equatorial plane, forming the so-called levitating tori, or the levitating polar clouds. We present the basic physical model allowing for the theoretical construction of these unique structures, which could exist in the Universe under particular astrophysical conditions. In more details, we assume a charged perfect fluid encircling rotating black hole immersed in an asymptotically uniform magnetic field, or the one being accompanied by the dipole-type magnetic field.

The Galactic diffuse X-ray emission (GDXE) is an unresolved X-ray emission that fills the Galactic center and extends over 100 degrees along the Galactic plane. The nature of the GDXE has been under scientific debate since its discovery more than 30 years ago. The main question was: is GDXE truly diffuse or is it composed from a large number of unresolved point sources? Thanks to many dedicated studies carried out on orbital telescopes over the last decade, GDXE is believed to arise from unresolved populations of X-ray binary systems. However, the identity of the dominant class of accreting objects in the Galactic center, bulge, and ridge remains unclear. Using NuSTAR ’s large aperture for unfocused photons and its wide X-ray energy range, we probe the diffuse broad-band continuum of the inner 1-3 degrees of the Galactic bulge (Perez et al., 2019), and compare with previous measurements of the inner 10 pc and inner 100 pc of the Galactic center using the same instrument. In my talk, I will present the results of this study, along with a brief overview of GDXE.

We show the possibilities of monitoring the long-term X-ray activity (especially of transients) on the example Aql X-1. Monitors of X-ray emission are important instruments for observing the activity on the long timescales (even of years). We show that the X-ray spectrum (especially its hardness) largely varies during some phases of the outbursts. Each outburst is a unique phenomenon as regards the time evolution of X-ry flux and the transitions between the states. The X-ray light curve of the outburst thus largely varies for the range of the observed energies and also for the individual monitors if they use narrow observing bands. To obtain the activity of the source in a very broad X-ray band, we use simultaneous monitoring with the monitors ISS/MAXI (2-15 keV) and Swift/BAT (15-50 keV). We show that observing in the 2-50 keV band enables us to resolve the complex spectral changes which occur during the outbursts. This also has the big perspectives for the planned X-ray instrument XGIS (2 keV-20MeV) and SXI (0.3-6 keV) onboard the satellite THESEUS for analyses of various emission mechanisms which operate during the activity of the sources like Aquila X-1.

We will focus on the phenomenon of short phases of the higher activity of the Galactic center, so-called flares. Recently, the occurrence of flares was directly observationally connected with the orbits of bright spots around the compact radio source Sgr A* (Gravity collaboration, 2018). These so-called hot-spots move close to the innermost stable circular orbit and therefore are unique probes of the strong-gravity regime. In particular, we study the effect of the electromagnetic interaction on the motion of flares and how this can be used to constrain the mutual black hole spin-magnetic field orientation. Our results indicate that the Galactic centre black hole as well as the surrounding magnetosphere possess opposite charges of the similar order of magnitude (see Zajacek+2018, Tursunov+2019, submitted).

All iridium atoms in the universe are initially born via the r-process in extreme cosmic events. On Earth iridium is quite rare. However, there is a remarkable iridium anomaly found in the Cretaceous-Tertiary boundary layer, where the amount of iridium increases by a few orders of magnitude. This effect is explained by the impact of a heavy meteoroid about 65 million years ago. At Aschaffenburg University iridium coatings are developed as reflection layers for space based X-ray telescopes. Iridium is also used as cover material for the thermonuclear batteries of the Voyager space probes - which are just leaving our solar system. So the cosmic journey of iridium is really a fascinating round trip from stars to Earth and back into space again.

X-ray Optics (19)

In this work investigations of EUV-induced, low temperature plasmas with relatively high electron density were performed. Experiments were performed using laser-produced plasma (LPP) EUV sources. The sources were based on a 10 Hz NdYAG laser system delivering pulses of energy up to 10 J with a pulse duration of 1 ÷ 10 ns. The EUV ionizing radiation was focused using grazing incidence collectors based on multifoil or ellipsoidal mirrors optimized for specific wavelength ranges. Additionally, an EUV focusing system based on a set of two paraboloidal mirrors was also used for a detection system deployed for measurements of weak EUV signals from the low temperature plasmas. In our experiments various gases were injected into the interaction region, perpendicularly to an optical axis of the irradiation system, using an auxilary gas puff valve. Irradiation of the gases resulted in ionization and excitation of atoms and molecules forming the EUV induced plasmas. Spectra in EUV and VUV ranges were measured using grazing incidence, flat-field spectrographs (McPherson, H+P Spectroscopy respectively). Spectra in UV/Vis range were measured using an Echelle Spectra Analyzer ESA 4000. The spectra were composed of spectral lines corresponding to radiative transitions in atoms, molecules, atomic or molecular ions. The ionic and atomic spectral lines were identified based on NIST database. The molecular spectra were identified based on literature data. For computer simulations of the molecular spectra measured in the VUV/UV/VIS range various codes like LIFBASE, Specair or PGOPHER were deployed. Apart from that, the electron temperatures of plasmas created in different gases were estimated employing a Boltzmann plot method. Temporal measurements in the EUV range were performed using the detection system based on the paraboloidal mirrors, dedicated filters and AXUV detectors.

The Advanced Telescope for High ENergy Astrophysics mission (ATHENA) is the second large class mission on the ESA Science Programme. It is the next generation X-ray observatory, and will embark ambitious and complex high performance detector instruments and the largest X-ray optics ever flown in space. The X-ray optics technology was specifically developed for ATHENA, in order to fulfill the demanding requirements of ATHENA. The Silicon Pore Optics (SPO) combines low mass with high performance, taking benefit from the superb qualities of mono-crystalline Silicon and investments done in the semiconductor industry. The talk will report on the development of the ATHENA optics, providing an overview of the technology development activities being implemented together with industrial and institutional partners.

Metallic coatings made of high-density noble metals (e.g. Ir, Pt or Au) are usually employed in grazing incidence reflecting optics for X-rays. Due to the large value of critical angle for total reflection, these materials offer a range of reflection extended to higher energies, but also present a series of M absorption edges at 2-4 keV which limit the reflectivity in this range and below. This is why the search for alternative coatings, able to improve the reflection in the soft energy range, is particularly relevant to the development of future telescopes, Athena (ESA), Lynx (NASA) and eXTP (CAS). It is well known that a low density coating (e.g. carbon or B4C) can enhance the reflectivity in the softer band (below 2 keV), even if commonly employed technologies are difficult to apply to all mirror fabrication technologies (notably, silicon pore optics). It was also recently proposed that the use of a thin chromium layer on top of the reflecting layer can greatly enhance the reflectivity in the 2-4 keV band. We discuss how, in future telescopes, the combination of these coatings can be used to enhance the reflectivity below 4 keV, and present novel solutions (carbon-like coatings realized by dip or vapour phase deposition) for the deposition of low-density coatings.

The project of 2D X-ray Lobster Eye telescope development to fit CubeSat form factor will be presented. The aim of the Cubesat telescope is to observe known an unknow X-ray sources such as supernovae, active galactic nuclei or X-ray afterglows of GRBs. The technologies for the X-ray telescope CubeSat demonstrator were selected suitable for CubeSat carrying the requirement of low power, low dimension, low mass and also low cost. The entrance aperture of 2D optics module is planned to be at least 69 x 69 mm, which represents 47 cm2. The field of view of this system is at least of 6 x 6 arcdegrees. As a focal detector the low power consumption no cooled Timepix3 pixel detector, operating in the energy range between 3-60 keV was selected. The new features of detector carrying the option of fast stream data reading with low dead time are very suitable for x-ray telescope mission.

Optical coherence tomography (OCT) is a well-established interferometric imaging technique providing high resolution cross-sectional views of objects (tomograms). The axial resolution of OCT is limited to about 1 µm when using infrared and optical wavelengths. The obvious way to improve resolution is to shorten the wavelength of the probing light. Optical coherence tomography using broad bandwidth radiation in the nanometer spectral range (extreme ultraviolet and soft X-rays) has been recently proposed [1]. This OCT variant, referred to as XCT, allows the reduction of axial resolution from micrometers to a few nanometers. The XCT imaging with axial resolution better than 8 nm was demonstrated using extreme ultraviolet and soft X-rays from a synchrotron [2]. Tomographic imaging with an axial resolution of about 22 nm has been recently demonstrated using extreme ultraviolet from a laser-driven light source based on high-order harmonic generation (HHG) [3]. In this paper we present preliminary studies on XCT using broadband soft X-ray radiation from a compact laser plasma light source based on a gas puff target [4]. The laser plasma source was optimized for efficient soft X-ray emission in the spectral range from 1.5 nm to 5 nm. The XCT measurements of a multilayer structure with 10 nm period and 40 % bottom layer thickness to period ratio, with an axial resolution of about 2 nm and detect multilayer interfaces up to a depth of about 100 nm. The experimental data are in agreement with OCT simulations. The new imaging technique can be useful for testing X-ray optics based on multilayer structures. Project is supported under the Polish-German scientific collaboration programme Beethoven by NCN (UMO 2016/23/G/ST2/04319) oraz DFG (PA 730/5). [1] G. Paulus, Ch. Rödel, Short-wavelength coherence tomography, Patent No.: US 7,656,538 [2] S. Fuchs, Ch. Rödel, A. Blinne, U. Zastrau, M. Wünsche, V. Hilbert, L. Glaser, J. Viefhaus, E. Frumker, P. Corkum, E. Förster, G. Paulus, Nanometer resolution optical coherence tomography using broad bandwidth XUV and soft x-ray radiation, Scientific Reports 6 (2016) 20658 [3] S. Fuchs, M. Wünsche, J. Nathanael, J. Abel, Ch. Rödel, J. Biedermann, J. Reinhard, U. Hübner, G. Paulus, Optical coherence tomography with nanoscale axial resolution using a laser-driven high-harmonic source, Optica 4 (2017) 903 [4] P. Wachulak, A. Bartnik, H. Fiedorowicz, Optical coherence tomography (OCT) with 2 nm axial resolution using a compact laser plasma soft X-ray source, Scientific Reports 8 (2018) 8494

Several types of micropore optics have been proposed and developed for light-weight and high-resolution X-ray telescopes. We have been developing silicon micropore X-ray optics using micro-electro mechanical systems (MEMS) technologies (Ezoe et al. 2010 MST). Sidewalls of 20 μm-width micropores etched through a 300 μm-thick silicon wafer are utilized for X-ray reflection mirrors. Since silicon is not suitable for X-ray reflection, noble-metal coatings on high-aspect micropores are necessary. To enhance X-ray reflectivity for our MEMS X-ray optics, we investigate atomic layer deposition (ALD) as coating techniques. It is characterized by good-conformality on three-dimentional structures with high-aspect ratios. To date, we demonstrated X-ray reflection with Ir- and Pt-coated silicon micropore optics using thermal ALD (Ogawa et al. 2013 Appl. Opt.; Takeuchi et al. 2018 Appl. Opt.). However, the surface roughness after metallic coatings needed to be further improved. Recently, we tested another process, i.e., plasma ALD, and achieved better surface roughness on Pt-coated ones. Furthermore, we have begun coating of Co and Ni for soft X-rays below 2 keV. In this talk, we report on characterization of metal-coated MEMS X-ray optics and future works such as light-element coatings on heavy metals, e.g., SiC on Pt.

Future X-ray observatories such as Athena (ESA) and Arcus (NASA candidate mission) require optics with a large effective area and a relatively low mass. Silicon Pore Optics (SPO) are being developed to meet these requirements in a cost-effective manner. Silicon wafers from the semiconductor industry are cut into mirror plates. Custom robotics are employed to bend the plates into the design shape of the mirrors and to stack them, creating the building blocks of modular optics. We discuss the ongoing development efforts to improve the stacking process, which focuses on two aspects. First, the improvement of the optical quality of stacks. Secondly, streamlining the production process to meet the speed and quality requirements of mass production for the production of a full optic for Athena.

We describe our ongoing effort to build a normal-incidence X-ray mirror for soft X-rays. Our science goal is the OVII emission line at E=574 eV (rest frame), which is expected to be the dominant signal from the theoretically predicted extended warm gas halos around massive galaxies -- a major component of the Universe\'s missing baryons. The mirror would employ a multilayer coating with hundreds of layers with a period 11-12A. Such a small period requires new coating techniques. We are trying Atomic Layer Deposition that, at least theoretically, can produce layers of the requisite sharpness and flatness. A thick glass normal-incidence mirror would act simultaneously as a narrow-band (1-3 eV) energy filter, picking up the redshifted OVII line from the much brighter (and non-redshifted) Milky Way foreground, and as an imager with angular resolution possibly approaching that of the optical reflectors. We will show first experimental results from our coating trials, as well as a mission concept that fits in the SmallSat envelope.

For future X-ray missions, higher angular resolution X-ray optics keeping its lightness are essential to achieve better observation sensitivity and finally more exiting scientific goals. For X-ray optics on board previous missions, it has long been known that there is an anticorrelation due to engineering issues between their angular resolution and lightness. Thus, in order to break the relationship, we have been developing X-ray optics based on our original electroforming techniques which have been established for ground-based applications. Electroforming is a technology that can transfer to a substrate with high accuracy by plating the nano-level structure of a super-precision master and makes it easier to fabricate Wolter type-I shaped two-stage full-shell mirrors. As the first trial, we fabricated a cylindrical electroformed-nickel sample with length, diameter, and thickness of 60, 60, and 1 mm. We measured axial and circumferential profiles of the inner surface and achieved ~0.07 / 0.3 µm in rms / PV for the best 30 mm axial direction and ~1 / 3 µm in rms / PV for the circumferential directions. We will show the details of our recent status and future plans.

Penn State University launched a Water Recovery X-ray Rocket (WRXR) on the 4th of April 2018. In the WRXR there were two payloads: the first being an X-ray spectroscope from Penn State University and the second being the Rocket EXperiment (REX), which successfully tested a wide-field X-ray optical system, based on 1D and 2D X-ray Multi-Foil Lobster-Eye (LE) optics (LE MFO), for the first time in a rocket setup and the second time in space. This paper details the 2nd generation of LE MFO optics which will optimize all of the optical parameters for rocket experiments and prepares the LE optics for instrument manufacturing. This new optical design will be based on ray-tracing and the knowledge gained from the previous experiment. The optical system will be optimized for the monitoring of nebula and/or X-ray source, which can be imaged with X-rays energies between 0.5 – 30 keV.

Recently, the European X-Ray Free Electron Laser (XFEL) has successfully produced its first X-ray photon pulse trains. This unique photon source will provide up to 27 000 photon pulses per second for experiments in different fields of science. In order to accomplish this, ultra-precise mirrors of dedicated shape are used to guide and focus these photons along beamlines of up to 930 m in length from the source in the undulator section to the desired focal point at an experimental station. We will report on a Kirkpatrick-Baez-mirror pair designed to focus hard-X-rays in the energy range from 3 to 16 keV to a 100 nm scale at the SPB/SFX instrument of the European XFEL. Both mirrors are elliptical cylinder-like shaped. The figure error of these 1 m long mirrors was specified to be better than 2 nm pv in terms of the height domain; this corresponds to a slope error of about 50 nrad rms (at least a best effort finishing is requested). This is essential to provide optimal experimental conditions including preservation of brilliance and wavefront. Such large and precise optics represents a challenge for the required deterministic surface polishing technology, elastic emission machining in this case, as well as for the metrology mandatory to enable a precise characterization of the topography on the mirror aperture. Besides the slope errors, the ellipse parameters are also of particular interest. The mirrors were under inspection by means of slope measuring deflectometry at the BESSY-NOM slope measuring profiler at the Helmholtz Zentrum Berlin. The NOM measurements have shown a slope error of 100 nrad rms on a aperture length of 950 mm corresponding to a residual figure deviation 20 nm pv for both mirrors. Additionally we found a strong impact of the mirror support conditions on the mirror shape finally measured. We will report on the measurement concept to characterize such mirrors as well as to discuss the achieved results.

While for soft and hard X-rays focusing X-ray telescopes based on Wolter I grazing incidence optics provide high flux sensitivity observation of the sky with imaging capabilities, hard X-/ soft gamma-ray astronomical observations above 80 keV are still at present performed by means of collimated/modulated apertures on large size cameras. By the way this kind of direct view detection suffers both of a moderate flux sensitivity (due to the physical impossibility to operate large size systems together with the high background flux due to the lack of focalization) and of an angular resolution not better that a few arcmin and in any case unable to resolve details of diffuse sources. Focusing optics through diffractive crystals in transmission configuration (Laue lenses) have been proposed to study the 80 keV – 1 MeV energy pass-band since a few decades ago. However their use have been so far limited to laboratory prototypes or short balloon experiments mainly due to the high alignment accuracy required for the realization of a Laue optics that consists of thousands of crystals. Such limitations are nowadays surpassed thanks to the technological progresses on both material science and metrology. Furthermore, strong aberrations for off-axis sources are expected with single diffraction optics. Recently, simulations and experimental tests suggested the possibility to exploit two successive diffractions from bent crystals in order to achieve two-dimensional focusing. In this paper we will present the results of simulations that motivate the exploration of the double diffraction geometry and we report on the on going design activities and experimental results achieved so far related to the development of this innovative application for high energy astrophysics that can find possible uses also in other technological and scientific fiels.

The large diameter, the long focal length, the high angular resolution, and the assembly complexity of the ATHENA X-ray telescope make the test procedures and the calibration campaign more challenging than ever. In order to tackle these tasks, ESA recently sponsored two X-ray facilities in Italy. BEaTriX (the Beam Expander Testing X-ray facility) is an X-ray beamline, being assembled at OAB and expected to start operation in late 2020, which will be a prototype to perform the functional tests of SPO mirror modules for ATHENA. BEaTriX will generate a uniform, 17 cm x 6 cm wide beam at the fixed energies of 4.51 keV and at 1.49 keV, making it possible to characterize the angular resolution and the effective area of SPO modules, at a rate able to sustain the SPO production and return a fast feedback on their optical performances. The other X-ray facility, VERT-X, will enable the X-ray calibration of the completed mirror assembly (MA) of ATHENA. VERT-X will scan an X-ray beam, collimated by a highly-precise Wolter-I mirror, in front of the complete MA of ATHENA, covering it uniformly with a polychromatic spectrum (0.1-12 keV). The MA will be placed horizontally in order to minimize optical distortions due to gravity, and the focused beam will be collected at the top of the vertical vacuum system by a sensitive pixel detector, therefore enabling the direct calibration in PSF and EA of the complete MA. In this presentation, the current status and the design of the two facilities will be presented.

The X-ray imaging telescope has been developed at Institute of Precision Optical Engineering (IPOE) of Tongji University since 2007. We have made a great progress on mirror fabrication, coating deposition, optical assembly and telescope’s characterization. This presentation will provide an overview of our progress. By now we can routinely produce cylindrical thin glass mirror substrates with angular resolution of about 30\". To improve the effective area, coatings with two or three material layers were designed and obtained a high reflectivity at 0.5-10 keV. During the optical assembly, an in-situ measurement system and 3-dimentional ray-tracing program have been developed to guide the assembly process in real time. Several prototypes have been fabricated and two of them were calibrated at PANTER X-ray test facility. The angular resolution and effective area were given.

eXTP employes 13 Wolter I golden nickel telescopes. During the passing year, eXTP Phase B study has been permitted, We have established a joint optical design team for optical design, within Institute of High Energy Physics, Xi’an Institute of Optics and Precision Mechanics of CAS and Osservatorio Astronomico di Brera. As the Phase B starts, we have 2 sets of the optics design, and will decide which one to use finally. Further, The smallest mandrel of OAB design has been tried to be polished, coated, and demolded, in Harbin Institute of Technology, and some optical and mechanical test are planned.

Two auto-collimators are used to detect the posture of each focusing mirror, and then the focusing mirror will be glued to the hub. First, the two self-collimators are placed perpendicular to each other on a horizontal experiment platform, and the pentaprism is used to refract the emergent light which comes from the self-collimator to mirror on the focal plane, adjust the element in the optical path to make the light return to the self-collimator, another mirror is on the other side of the platform. Secondly, the focusing mirror is installed in the optical path, move the pentaprism and the mirror on the platform to lead the light which come form the collimators incident onto the focusing mirror, adjust the focusing mirror to make the incident light come back to the collimators by passing though the mirror on the focal plane and the mirror on the platform. In this way, the purpose of the focusing mirror can be detected by the two self-collimators to manufacture X-ray telescopes. （This is not the final version）

High temperature plasmas produced by interaction of pulsed power lasers with matter, emit radiation in a wide wavelength range from soft X-rays (SXR) to visible light. All these plasmas, emit spectral lines in extreme ultraviolet (EUV) range. In case of ions with Z ≥ 6 lines from the SXR range can be detected. For measurements of the SXR spectra a spectrograph based on 2x3 mm transmission grating 5000 l/mm having 450 nm grooves with a 50 nm Si 3 N 4 residual substrate, manufactured by ZonePlates Ltd. The spectrograph is equipped with an entrance slit, mounted close to the plasma and the second one, in front of the grating. The spectral range is limited mainly by transmission of the residual layer and the resolution by the spectrograph geometry and widths of the slits. Spectra are recorded deploying a CCD detector. Initial tests were performed using the laser plasma produced SXR source, based on a double stream gas puff target, developed in Institute of Optoelectronics, Military University of Technology, Warsaw, Poland.

Lobster eye X-ray optics in the one dimensional (1D) arrangement has advantages in higher reflectivity, especially for higher energies, compared to classical two dimensional (2D) Schmidt\'s arrangement. One dimensional optics can determine only one direction of the incoming beam. There is placed a strip in front of the optics for determining of the second direction. This strip is made of X-ray proof material which blocks the incoming beam and thus causes a gap in the line. Based on these facts, it is possible to determine the position of each point source which has enough signal to gap ratio. Unfortunately, the intensity of sources is not possible to assess by this method.

During last two years, established cooperation between Czech Technical University in Prague and University of Applied Sciences in Aschaffenburg focused on studying potential of multiple reflective layers for space-born X-ray telescopes. To understand the sputtering process, which is used for creating homogenous layers with low microroughness of the surface, and the behaviour and quality of the layers themselfs, the work was divided into smaller steps. After tests of adhesivity and stability of layers followed the prove of reflectivity and comparison of real situation with the theoretical expectations. As addition, also microroughness test based on dispersion was performed. This poster presents a part of results from Panter facility and their comparison with theoretical simulations. Because we are not going to stop our development at this moment, it also shows the direction where we would like to proceed next time - using other kinds of substrates for the mirrors, like silicone, and study the behaviour of other multimaterial compositions, which could be benefitial for space usage, like mangan or tungsten.

X-ray Missions (16)

THESEUS is a mission concept proposed in response to the ESA call for medium-size mission (M5) within the Cosmic Vision Programme and selected by ESA on 2018 May 7 to enter an assessment phase study. The mission is designed to vastly increase the discovery space of the high energy transient phenomena over the entirety of cosmic history. Its primary scientific goals will address the Early Universe ESA Cosmic Vision themes “How did the Universe originate and what is made of?” (4.1, 4.2 and 4.3) and will also impact on “The gravitational wave Universe” (3.2) and “The hot and energetic Universe” themes. This is achieved via a unique payload providing an unprecedented combination of: 1) wide and deep sky monitoring in a broad energy band (0.3keV - 20 MeV); 2) focusing capabilities in the soft X-ray band providing large grasp and high angular resolution; and 3) on board near-IR capabilities for immediate transient identification and redshift determination. In this talk we will review the status of the mission current assessment phase being carried out in collaboration with ESA as part of the M5 competition.

The Einstein Probe (EP) mission is a advanced mission of China for all-sky monitoring to discover and study high-energy transients and variability in the soft X-ray band. It will finish the Phase-B study by the end of this year. In this year, the design of the Follow-up X ray Telescope (FXT) has been again optimized, from one mirror and 2 cameras with a switch facility, to 2 mirrors and 2 cameras. The Structural Thermal Model of FXT has been assembled in IHEP, transported to IAMC in Shanghai, and join in the mechanical test of the satellite. And the readout electronincs for camex of pnCCD has also been tested successfully. After the mechanical and thermal tests, EP mission will enter the Phase C (qualification model phase).

I will present the status and plan of the following projects: 1) Insight-HXMT X-ray mission (launched on June 15th, 2017, mostly on X-ray binaries and GRBs); 2) GECAM (to be launched by the end of 2020, two small satellites covering full sky simultaneously on GRBs and other transients from several keV to MeV); 3) SVOM (to be launched by the end of 2021, carrying optical and X-ray telescopes, a wide FoV hard X-ray imager and three gamma-ray monitors, mostly on GRBs and other transients); 4) EP (to be launched by the end of 2022, carrying many wide FoV lobster-eye X-ray telescopes and two narrow FoV X-ray follow-up telescopes, mostly on tidal disruption events, GRBs and many other transients); 5) eXTP (a large X-ray observatory developed by a large Sino-European consortium for launch around 2025 or slightly later, carrying large arrays of X-ray timing, spectroscopy and polarimetry telescopes, as well as a wide field monitor); 6) HERD (a large cosmic-ray experiment onboard China’s space station for operation around 2025, with unprecedented acceptance and energy range for direct measurements of cosmic-rays, electrons and gamma-rays in space). The latter two missions (eXTP and HERD) are also the key missions for the Exploring the eXtreme Universe (EXU) program, an international mega-science project proposed to the Ministry of Science and Technology (MOST).

AstroSat is India’s first multi-wavelength space astronomy mission that was launched on 28 September 2015. AstroSat carries five payloads that perform observations in the optical, ultraviolet, soft and hard X-rays. The five scientific payloads are (i) a Soft X-ray Telescope (SXT), (ii) three Large Area X-ray Proportional Counters (LAXPCs), (iii) a Cadmium-Zinc-Telluride Imager (CZTI), (iv) two Ultra-Violet Imaging Telescopes (UVITs) one for visible and near-UV channels and another for far-UV, and (v) three Scanning Sky Monitors (SSMs). AstroSat is a proposal-driven observatory with observing opportunities available to national and international scientists. This talk will present the current status of the instruments onboard Astrosat and the main results obtained including multiwavelength UV/X-ray observations.

Toward an era of x-ray astronomy, next-generation x-ray optics are indispensable. There is a well-known trade-off relation between the angular resolution and the mass normalized by the effective area among these three methods. In order to break this relation, new mirror fabrication methods are demanded. To meet the demand for telescopes lighter than, we are developing what we call MEMS x-ray optics based on micromaching technologies. The technologies include dry etching of thin silicon wafers, high temperature annealing for smoothing, hot plastic deformation of silicon wafers and atomic layer deposition of noble metals. Two small satellite missions GEO-X and ORBIS use this type of optics. In this talk, we show these missions together with recent development of the MEMS X-ray optics.

The SVOM MXT will use a narrow-field-optimised Lobster Eye optic comprised of a set of micro-pore optic plates (MPOs) for gamma ray burst (GRB) location and measurement. The 1 m focal length qualification model (QM) MXT optic is the first fully populated Lobster Eye optic to be X-ray tested. We present the test results obtained at the University of Leicester and at Panter, MPE, giving the point spread function, energy response and effective areas, as well as results from the thermal tests and focal length determination. We also present our modelling, which incorporates the aberrations seen from the individual MPOs to determine the PSF of the assembled optic, and predicts the performance of the QM optic with incredible accuracy.

The University of Leicester (UoL) is involved in several missions using the novel micro-channel pore optics (MPOs) in a Lobster Eye optic configuration, including SVOM, SMILE, Einstein Probe and Theseus. SMILE is an ESA-Chinese, Earth Magnetosphere mission due for launch in November 2023, where UoL is the PI institute of the Soft X-ray Instrument (SXI). Theseus is an ESA M5 concept mission currently in a Phase A study and projected to launch in 2032. UoL is also the PI institute for the Theseus SXI, including optics and detector development. Presented are details of each mission including the current status of the overall mission and the UoL activities.

We present an update on our work advancing soft X-ray polarimetry in support of the sounding Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX) mission, as well as the status of a possible orbital version. REDSoX will utilize focusing optics, critical-angle transmission (CAT) gratings, laterally graded multilayer mirrors and CCDs to measure polarized soft X-rays below 1 keV. Much of the development for the proposed polarimetry and spectroscopy missions is performed in the MIT polarimetry beamline. Operating as a monochromator, the beamline has been used to measure the absolute efficiencies of the REDSoX prototype gratings as well as the Arcus Phase A gratings. The beamline is also capable of producing and measuring polarized soft X-rays in support of the development of REDSoX and other polarimetry missions. In preparation for future missions, we have begun tests to align the REDSoX prototype CAT gratings using internal MIT Kavli funds. Support for this work was provided in part by the National Aeronautics and Space Administration grant NNX15AL14G as well as a grant from the MIT Kavli Institute Research Investment Fund.

The recent progress in cubesatellites technologies, based on platform instrumentation miniaturization as well as on advances in control engineering allows astrophysical payloads for these minisatellites to be considered including tandem flights as well as fleets of satellites. The BRITE constellation minisatellites for precise star brightness measurements in visible light represent an excellent example. Especially the satellite bus parts were recently substantially miniaturized, raising the question, namely, does the scientific payloads can be miniaturized as well? The cubesat standard size is 1-liter volume i.e. 10 x 10 x 10 cm and its weight is typically about 1.3 kg. Multiple modules are possible, i.e. 3U = 3 modules/units i.e. 10 x 10 x 30 cm, typically up to 12U. The recent technological progress allows use in astronomy and astrophysics, as well as in other sciences and applications, for the first time. In addition to the numerous commercial missions, the mini-satellites are in the development at many Universities, mostly with the involvement of students, so the educational aspects play a role there as well. I will present some ideas for miniature X-ray imaging instrumentation for cube satellites, including tandem flights and fleets. The first such X-ray monitor with Lobster Eye X-ray optics is already in space onboard the 1st Czech 2U/3U cubesatellite VZLUSAT. The tandem flight of two cubesatellites could be advantageous e.g. for small astronomical X-ray telescope with Kirkpatrik-Baez optics but there are interesting possibilities for fleets of minisatellites with X-ray optics as well.

The Einstein Probe (EP) is a small satellite dedicated to time-domain astronomy to monitor the sky in the soft X-ray band. It is a mission led by the Chinese Academy of Sciences and developed in its space science programme with international collaboration. Its wide-field imaging capability is achieved by using established technology of the micro-pore lobster-eye X-ray focusing optics. Complementary to this is deep X-ray follow-up capability enabled by a Wolter-I type X-ray telescope. EP is also capable of fast transient alerts triggering and downlink, aiming at multi-wavelength follow-up observations by the world-wide community.  In this talk, we will briefly present the developments of Wide-Field Telescope, a Lobster-eye telescope, covering a FOV larger than 3600 square degrees, including the optics assembly, the focal plane detectors as well as the expected performances. 

From its inception Swift was designed to be highly flexible and responsive. At launch this meant that Swift could dynamically respond to new Gamma-Ray Bursts with all three instruments on a near immediate timescale based on a fully autonomous response onboard the spacecraft. This autonomy allowed a very rapid and flexible response to ground control via highly compact and efficient commanding in response to Target of Opportunity (ToO) requests. Unlike many other missions Swift can routinely respond to ToO within an hour or two, and record responses have been less than ten minutes. A major limitation for these ToO responses was the need to either utilize ground passes over Earth based tracking stations (typically ~10 opportunities per day), or by using the forward link to the Tracking Data Relay Satellite System (TDRSS). TDRSS links require a manual intervention to be scheduled, and the creation of a pass plan to create the commanding required also required human intervention. After consultation with NASA\'s TDRSS scheduling, we have developed new ground software which can both schedule TDRSS links, and create the commanding necessary, based only on the scientific decision making of deciding whether a ToO is approved. We expect that in the near future we will grant blanket approval for certain rigously defined opportunties. Follow-ups to high quality LIGO-Virgo neutron star merger candidates are examples of cases where we expect Swift will be able to routinely carry out follow-ups in less than 30 minutes. This capability is unprecedented and we expect to apply it to a wide range of Swift Transient Astronomy targets.

On July 13,2019 at 14:41 CEST the X-ay space observatory Spectrum-Roentgen-Gamma (SRG) was successfully launched from the Baikonur cosmodrome. It carries two X-ray telescopes, ART-XC, which was developed under the lead of the space research institute IKI, Moscow and eROSITA, which was developed and built by a consortium of German institutes under the direction of the Max-Planck-Institute for Extraterrestrial Physics (MPE) and with support from the German Space Agency at DLR. Meanwhile (November 2019) SRG has reached the halo orbit around L2, 1,5 million kilometers from Earth. eROSITA is in its calibration and performance verification phase, and this early data confirm the excellent performance of the instrument. Starting in December, eROSITA will carry out eight complete X-ray surveys over the next four years, creating the first complete sky map in the medium X-ray range. At lower energies it will approximately 25 times more sensitive than the previous ROSAT mission. In addition it has much better spectroscopic capabilities. The main scientific goal of eROSITA is to map the large scale structure of the universe and to find out how these structures grow in the course of cosmic time. Clusters of Galaxies which track this structure are filled with millions of degrees of hot plasma and can be detected directly by an X-ray telescope. eROSITA is designed to detect 100.000 clusters of galaxies to reconstruct also the history of their growth. This, in turn, will tell us about the amount and perhaps the nature of the enigmatic dark energy and dark matter.

THESEUS (Transient High Energy Sky and Early Universe Surveyor) is a space mission concept selected by ESA for a Phase 0/A study as one of the three candidates M5 missions in the framework of the Cosmic Vision programme. It is designed to vastly increase the discovery space of high energy transient phenomena over the entirety of cosmic history, with particular emphasis on the use of GRBs for exploring the early Universe and providing a substantial contribution to multi-messenger astrophysics. To achieve this scientific objectives, the THESEUS payload combines a transient trigger system based on two instruments, the XGIS, that is a wide field deep sky monitor in a broad energy band (2 keV-10 MeV), and the SXI (0.3-5 keV), that thanks to its focusing capabilities in the soft X-ray band provides a large field of view and high angular resolution, with an on board near-IR telescope for immediate transient identification and redshift determination. The X-Gamma ray Imaging Spectrometer (XGIS) instrument comprises 2 cameras pointed at offset directions in such a way that their FOV partially overlap. Each camera has imaging capabilities in the energy band (3 -150 keV) thanks to the combination of an opaque mask superimposed to a position sensitive detector. Furthermore the detector plane energy range is extended up to 10 MeV without imaging capabilities. Key of the design of XGIS are Silicon drift detectors (SDD)taht can operate both as direct low energy X-ray detector and as readout device of the scintillation light of a scintillator. We breafly describe the THESEUS payload and show the structure of XGIS instrument and its expected parameters.

The proposed joint German-Czech project CATEX (Catastrophic events in the Universe: the X-ray view) is a feasibility study for a novel space experiment focussed on monitoring and investigation of catastrophic events in the Universe. It uses the innovative combination of an uncooled pixel detector (Timepix) and a Lobster-eye optic with optimised X-ray mirror coatings. The advantages of this kind of telescope are a wide field of view and low power consumption, together with an improvement of the detection range. The projects aim is a complex feasibility study of an advanced wide field X-ray telescope for monitoring and research of the catastrophic events - as well as of other variable and transient sources - in the Universe. The theoretical and experimental study will include all important parts of the future system from an optimization of the mirror coatings, the design the optical module, the analysis of potential observation targets, the design of the detection system under variable vacuum conditions, the development of algorithms for processing the X-ray images of Lobster eye optics, and methods of their visualization. The results of these studies and experiments will provide new knowledge about the behaviour of individual components and can be used for the development of advanced scientific satellite payloads for an X-ray monitoring of astronomical objects. The CATEX project proposal is currently under evaluation at the funding agencies DFG and GAČR.

Today’s space applications are pushed forward by new technologies that enable smaller dimensions, less complexity and lower cost of satellites. This conference contribution discusses an innovative approach for the radiation protection of satellite components against cosmic particles. Traditionally, solid tungsten foils or lead foils are used to protect the radiation-sensitive electronics in this field. In a miniature satellite, however, these high-density materials can contribute significantly to the critical overall mass. Our inspiration for lowering the mass-density of radiation-protective materials comes from X-ray protection in medical applications whereby composites, such as metal foams or polymer matrices loaded with particles of high-Z elements, have been investigated. An analogous approach for space applications introduces the additional requirement of structural and mechanical stability under thermal cycling. Accordingly, we design and study temperature-cycling-resistant polymer-based (mainly polyurethane- and silane-based) composites containing particles of high-Z elements (such as W, Bi, or Mo). The presence of the metallic particles contributes to radiation shielding, while the polymeric matrix provides the desired mechanical properties: flexibility under thermal cycling and low density. In parallel, solid films of high-Z elements and having thickness comparable to the size of the particles used in the nanocomposites are deposited by magnetron sputtering. The properties of the radiation protective films obtained by these two different techniques will be compared and the X-ray protective properties and temperature cycling resistance will be discussed. Nanocomposite-based radiation-protective coatings will be tested in a corresponding payload experiment onboard of the upcoming Portuguese satellite INFANTE. This abstract is a result of the project “BAPORECO – Bavarian-Portuguese research collaboration”, (BAYFOR grant no. BayIntAn_HSAB_2019_122), and of the project “INFANTE: Satellite for maritime applications and communications from constellations” (POCI-01-0247-FEDER-024534), supported by the Operational Thematic Program for Competitiveness and Internationalization (POCI), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF).

We present results of the thermal vacuum testing of Timepix family-based detector with respect to the effects on its properties and behaviour under non-standard conditions. Readout ASIC chip bump-bonded with semiconductor detector was thermally coupled to a small aluminium block. This block was thermally stabilised using a PID controller and a~three-stage Peltier element. This arrangement, located in the vacuum chamber, allows the detector to be tested under defined temperature settings ranging from -30 °C (resp. -40 °C) to +80 °C. Results of this testing help to strengthen the knowledge regarding the~behaviour of the base part of the detector under extreme conditions where temperature stabilisation of the detector is very difficult or energy-consuming. The experiments were performed on a detector chip equipped with a 300 µm thick Si sensor.

Others (3)

I will present an introduction to the 12th AXRO International workshop on X-ray optics as well as historical background presenting the history of these workshops and also general history as well as the recent status of development of X-ray optics in the Czech Republic. There is a long tradition of X-ray optics development dated back to 1970 with numerous X-ray optical technologies and techniques designed developed and tested. In recent years these efforts focussed on alternative and cost-effective solutions based on innovative substrates such as thin glass sheets and/or silicon wafers. Novel X-ray optical designs included also wide-field optical systems of Lobster Eye type in Schmidt arrangement as well as Kirkpatrick-Baez modules.

I will present an conclusion to the 12th AXRO International workshop on X-ray optics.

I will present a concluding address to the 12th AXRO International workshop on X-ray optics.