EUV and X-ray Optics: Synergy between Laboratory and Space VIII

Conventional mining might not be sufficient to support the growth of humankind heavily dependent upon rare materials in technical applications. Asteroid mining might be an answer, with Near-Earth objects (NEOs) being the first targets. However, the first step in the asteroid mining cascade is to probe reachable asteroids. Moreover, to identify the best candidates for further activities hundreds to thousands of asteroids must be screened. Fast progressing development of CubeSats might allow the space community to do the initial in-situ screening in a minimalist and economical manner. Additionally, formation flying might enable the miniaturization of optical payloads for asteroid composition analysis in CubeSats. The recent developments in formation flying are summarised in this study and the possibility of utilizing formation flying CubeSats for asteroid surveillance explored.

Photonic quantum technologies are a promising platform for a large variety of applications ranging from secure long-distance communications to the simulation of complex phenomena. Among the material platforms under study, semiconductors offer a wide range of functionalities opening several opportunities for the development of integrated quantum photonic circuits. AlGaAs is particularly attractive to monolithically integrate active and passive components since it combines high second order nonlinearity, electro-optic effect and direct bandgap. In this talk, I will present the work of our team on the generation of quantum states of light in the telecom range with nonlinear AlGaAs chips working at room temperature. The talk will review recent developments on monolithic and hybrid integrated devices, describe the versatility of these systems for the generation and manipulation of quantum frequency states and show their potential for the implementation of flexible entanglement-distribution networks for secure communications.

Photonic crystal fibres (PCFs)—thin strands of glass with an intricate array of hollow channels running along their length—offer both hollow and solid glass cores, and allow unprecedented control over dispersion and birefringence, ushering in a new era of linear and nonlinear fibre optics, for example: chiral PCF is circularly and topologically birefringent, supporting optical vortices and in some cases strong circular dichroism; through pressure-adjustable dispersion, gas-filled hollow-core PCF provides an elegant means of compressing pulses to single-cycle durations, as well as underpinning a range of unique sources of tunable deep and vacuum ultraviolet light; microparticles optically trapped inside hollow core PCF van be used to sense physical quantities with high spatial resolution; and strong optomechanical effects in solid-core PCF permit stable timing-modulated high harmonic mode-locking at few-GHz repetition rates.

This presentation focuses on the use of arrays of Micro Pore Optics (MPOs) to create large field of view lobster eye telescopes. The University of Leicester has been at the forefront of this technology since 1991 when Fraser et al. presented the idea at SPIE. I will discuss the history of using Microchannel Plates (MCPs) as optics from the initial lab experiments which demonstrated their performance, up to the new laboratory experiments we are running to further develop and improve the technology. The missions which have employed these optics, from the already launched BepiColombo to upcoming missions such as SVOM, SMILE and Einstein Probe, will be presented. Recent results and discoveries from the LEIA mission, launched July 2022, will also be shown. Ideas for future missions and further research areas will also be considered.

I will give a short overview of astronomical X-ray optics covering the past, recent, and future developments with an emphasis on grazing incidence optics and on developments in the Czech Republic. There is a long history in the X-ray optics development in the Czech Republic – the first X-ray mirror was produced in 1969. The first Czech X-ray mirror (50 mm Wolter for solar imaging) was flown to space onboard the Vertikal 8 rocket in 1979 as part of a photographic solar X-ray telescope in collaboration with Polish institutes. The recent developments focus on new technologies based on novel lightweight materials such as slumped glass foils and Silicon wafers and also on novel designs and arrangements such as wide-field Lobster Eye X-ray optics.

We have been developing an ultra-lightweight Wolter type-I X-ray telescope fabricated with micro electro mechanical systems (MEMS) technologies for GEO-X (GEOspace X-ray Imager) mission. GEO-X will aim global imaging of the Earth's magnetosphere using X-rays. The telescope is our original micropore optics which is light in weight (~5 g), compact with a short focal length (~250 mm), and has a wide field-of-view (~5 deg x 5 deg). In this talk we show developed assembly processes to meet the requirements of the GEO-X mission and the telescope's X-ray imaging performance as an engineering model with this method.

A new detection system based on Silicon Drift Detectors (SDD) coupled with scintillator bars has been developed for X-/gamma-ray detectors in astrophysics, and allows compact broad energy passband detectors (2 - 10/20 MeV) to be built. The WFM-IS on board ASTENA will be based on this technology. A coded mask provides imaging capabilities up to 150 keV, while above this limit Compton kinematics and the flux on different cameras can be exploited to obtain crude imaging above the 150 keV limit. We present simulations aimed at evaluating the instrument imaging performances.

We have been developing silicon foil X-ray optics using a hot plastic deformation process for future astronomical observations. Our foil mirror is made of a 0.3-mm thick silicon wafer and is plastically deformed into a high-accurate conical shape with a curvature radius of ~100 mm. The angular resolution we evaluated using a test sample mirror was ~32 arcseconds in the best region. We have also successfully coated a platinum film on the foil mirror using the atomic layer deposition process. In this talk, we report on the fabrication method and the X-ray imaging capability of our silicon foil X-ray optics.

We present the design, assembly, and tests of new Lobster Eye (LE) and Kirkpatrick Baez (KB) modules based on Multi Foil Optics technology (MFO). The LE X-ray optics is a wide field of view (FOV) optics type Lobster Eye (LE) with a short (400 mm) focal length (suitable for CubeSat application) based on Schmidt design. The 2D LE optics consists of two orthogonal sub-modules of flat smooth reflective foils and each sub-modules focuses in one direction. The key parameters (the FWHM, the FOV (Field of view), and angular resolution, effective area) of the 2D LE optic were measured with different detectors. The advantage of MFO LE is that for off-axis points the angular resolution is preserved throughout the FOV, as demonstrated by measuring. There is a combined detector system that includes two detectors - Timepix3 Quad and spectroscope. The benefit of the combined detector system was demonstrated in the real measurement. Moreover, a new generation multiple arrays module of 2D X-ray KB optics with long f (nearly 6 meters) based on multi-foil silicon assembling technology was designed, manufactured, and tested in optical light and in X-rays at the Panter facility and the preliminary results will be also presented and discussed.

The presentation describes the CubeSat microsatellite spacecraft with X-ray optical payload for prompt observation of transient astrophysical objects in X-ray energy range. By combining telescope concepts and miniaturized detectors, the small spacecraft will be able to probe the X-ray temporal emissions of bright events and also short and long term observations of other types of variable X-ray sources. The spacecraft is based on the CubeSat nanosatellite platform with a volume of 8U. The spacecraft carries two X-ray telescopes combined in one demonstrator. The first is intended for X-ray transient monitoring and localization, and the second for detailed spectroscopic observation. The design, assembly and testing of demonstrator will be presented.

Reflective coatings for astronomical X-ray optics were developed at the “Aschaffenburg Competence Center for Astronomical and Space Instrumentation” (ACCASI) since several years. As part of a Bavarian-Czech cooperation between the Technical University of Aschaffenburg and the Czech Technical University of Prague, now two mechanically identical telescopes were built. One telescope optic was equipped with conventional gold-coated mirrors, manufactured by the Czech project partners. The 34 X-ray mirrors of the second telescope use an innovative coating system made of chromium and iridium, which was applied at the Aschaffenburg coating laboratory. Both telescopes are designed according to the bionic principle of a reflecting lobster eye. The optics works with two consecutive reflections on mutually perpendicular mirror surfaces. This enables a large field of view with many square degrees in diameter, which, however, comes at the price of a reduced angular resolution. An extensive X-ray characterization of these telescopes was carried out at the PANTER test facility of MPE, which simulates parallel starlight incident on the telescopes. The telescopes have an angular resolution of about 4 arc minutes in X-rays and a focal length of about 2 meters. Furthermore, the used X-ray mirrors reflect and focus visible light as well and this functionality in the optical regime was checked in laboratory tests. Now another test campaign was done to examine the telescope resolution for real objects of the visible sky and the imaging properties for star constellations. Such functional tests by observing astronomical objects of the visible sky may simplify and accelerate the development of X-ray telescopes for satellite applications.

The process of differential deposition is currently applied at the ESRF in order to correct figure errors of x-ray optics substrates, prior to multilayer deposition. The substrate is moved at a controlled speed in front of a sputtering source to precisely control the deposition profile. This work will describe the concept of differential deposition at the ESRF as well as recent results of its implementation to correct a real mirror substrate surface. Finally, initial studies using a synchrotron beamline characterization technique based on x-ray total reflection are presented.

Multilayer interference coatings are useful to obtain efficient diffraction gratings in the soft x-ray and the extreme ultraviolet (EUV) spectral domains. By matching multilayer Bragg interferences and grating diffraction conditions, one can achieve high spectral resolution (λ/∆λ > 1000) with efficiencies close to the reflectance of the multilayer mirror. Such multilayer gratings are of particular interest for high-efficiency and high-resolution EUV spectro-imager instruments. We present here experimental results and modeling of multilayer gratings developed for the EUV spectro-imager abroad Solar-C mission. Periodic and aperiodic Al/Mo/SiC multilayers were optimized and deposited by magnetron sputtering on high groove density lamellar gratings with various depths. The measured EUV diffraction efficiencies of the multilayer gratings are in good agreement with the model simulated by rigorous coupled-wave analysis and exceed previous results obtained for the Solar-B mission. We also demonstrate for the first time experimental broadband diffraction efficiency by using grating with optimized aperiodic multilayer coatings.

A software called LOPSIMUL is presented. The main advantage of LOPSIMUL is very high computational rate. LOPSIMUL is intended for simulation of multi-foil optical systems, particularly Schmidt or Anglel lobster eye. Various systems derivated of lobster eye can be simulated by LOPSIMUL, too. Kirkpatrick-Baez system can be simulated with limitations. LOPSIMUL contains few reflectivity models. Any reflectivity model can be imported to LOPSIMUL in a form of look-up table. Lopsimul draws focal image and x and y profiles. LOPSIMUL calculates FWHM, effective collecting area and other principal results.

In 1895, Professor Wilhelm Conrad Röntgen detected a new type of radiation that was able to penetrate solid materials, which he called X-rays. In 1901 Röntgen received the first Nobel Prize in physics in honour of this ground breaking discovery. The Deutsches Röntgen-Museum (DRM) in Remscheid (Germany) is the institution that uniquely and comprehensively explores and documents the life and work of W. C. Röntgen and the impact of his discovery. The DRM’s location in Remscheid is not coincidental, with Röntgen’s birthplace only a short walk away from the exhibits. Every visit to the museum amounts to a unique expedition through the worlds of medicine, science and technology. The museum’s emphasis on the diversity of Röntgen’s invention by a multilingual, multi-medial approach enables all visitors to make their own personal discoveries. The Deutsches Röntgen-Museum in Remscheid is a must-see for X-ray scientists from anywhere in the world. This contribution provides an insight into the history of X-rays and offers a guided tour of the Deutsches Röntgen-Museum and its exhibits.

Starting in 1951, the 50th anniversary of the award of the first Nobel Prize for physics to Wilhelm Conrad Röntgen, the Lord Mayor of the German City of Remscheid has given out Röntgen Medals. The Röntgen Medal annually honours scientists who "in the broadest sense have made a special contribution to the progress and dissemination of X-ray discoveries in the theoretical and applied sciences". The Röntgen Medal has become highly recognized in the scientific world. To date, more than one hundred excellent scientists have received the honour. Through their chronology, this contribution presents a "Who’s Who" of X-ray science and provides selected insights into their scientific work; with the fields of X-ray optics and X-ray astronomy receiving special focus.

Development of the third generation X-ray synchrotron facilities, beginning in the 1990s offered the prospect of powerful tunable X-ray beams for a broad range of applications and, along with it, a host of beamline and optics challenges. One of the main challenges stemmed from the high power (kWs) of the X-ray beams: beamline and optical components capable of handling the high heat loads of the beams had to be developed and tested. Another challenge was, and remains, the development of precision optical elements that preserve X-ray beam quality. In this talk and based on firsthand experience, I review the development of a number of beamline and optical components, from inception to completion, with emphasis on the lessons learned in the process.

EUV/SXR induced plasmas can be produced by interaction of intense X-ray or extreme ultraviolet (EUV) radiation beams with gases. Ionization of molecules can result in further dissociation to ionic and neutral species. In this work investigations of the EUV induced plasmas with a relatively high electron density were performed using laser-produced plasma (LPP) EUV or soft X-ray sources. LPPs were produced by irradiation of a double stream gas puff target with xenon as the working gas. EUV or SXR radiation was focused using grazing incidence collectors of different type. EUV irradiation of gases resulted in ionization and excitation of atoms and molecules forming low temperature plasmas. Spatio-temporal behavior of this type of plasmas formed in various gases was investigated using an optical streak camera. Significant differences concerning temporal changes of the optical emission from plasmas created in molecular and atomic gases were revealed. Spectral measurements in a wide range were also performed. The most intense emission lines were assigned to singly charged ions or atoms. Various molecular bands were also detected.

Imaging large areas of a sample non-destructively and with high resolution is greatly interesting to science and industry. For X-ray ptychography, the achievable scan area at a given spatial resolution is limited by the coherent photon flux of modern X-ray sources. Multibeam X-ray ptychography can improve the scanning speed by scanning the sample with several parallel mutually incoherent beams generated by illuminating multiple focusing optics in parallel by a partially coherent beam. The main challenge with this scheme is the robust separation of the superimposed signals from the different beams, especially when the beams and the illuminated sample areas are quite similar. We overcome this difficulty by encoding each probing beam with a unique X-ray phase plate. This helps the algorithm reconstruct the multibeam data robustly.

We present experimental results on wavelength-dispersive soft X-ray spectroscopy of Titanium dioxide, demonstrating the functionality of a newly developed, laboratory-scaled setup at the Institute of Applied Photonics e.V. for the first time. In our instrument, the micron-sized photon emission from an electron-excited source is collected efficiently by a rotationally symmetric, ellipsoidal mirror and subsequently dispersed by a reflection zone plate with inscribed diffractive wavefront correction, to compensate for figure and alignment errors of the ellipsoid to some degree. The measured data, recorded with a CCD camera in one meter from the source, show clearly separated peaks from the Ti L (l,n) doublet with a central energy of about 398.3 eV and the Ti L alpha fluorescence line at 452.2 eV, as well as the contribution from O K emission (523.1 eV). An energy resolving power around 38 and a signal-to-noise ratio between 4.4 and 10.7 prove the good quality of the spectrum.

Grazing incident Soft X-ray source (SXR) mirrors find applications in astrophysics, space plasma research, hot plasma research and in various imaging and spectroscopy laboratory systems. SXR sources and vacuum optical beamlines are needed for their characterization and testing. A microfocus laboratory Soft X-ray source, which can be used in facilities for SXR optical components metrology, was designed and realised. The source in vacuum consists of an electron gun with stabilized electron beam focused to a 200 um spot on a target from appropriate material. Four different targets allowing generation of SXR with four different energies from four different elements are placed on a rotational turret. Required photon energy can be selected without vacuum interruption. Comparison of theoretical and experimental characteristics is described.

We present the stitching interferometry system of ALBA. It has been designed for measuring the surface of long X-ray optics (up to 1.5 meters) with sub-nanometer accuracy, thanks to effectively removing the systematic errors introduced by the flat reference. We discuss the main features and measurement routines of the setup, including the aspects related to error removal. The instrument is based on a Fizeau interferometer, Zygo Verifire HD, which is mounted on top of an in-house built scanning and positioning stage with four degrees of freedom: horizontal displacement, vertical displacement, yaw rotation, and roll rotation. The relative orientation between the optical bench and the interferometer platform is measured by an external autocollimator and two inclinometers. Tracking the interferometer trajectory allows us removing the guidance errors and solving reconstruction ambiguities. We show the first commissioning results and we analyze the actual system accuracy.

Many key questions in high energy astronomy (>100 keV) are still unanswered, essentially because current instrumentation lacks the necessary sensitivity and angular resolution. New telescopes able to focus X-/Gamma-rays, based on Laue lenses using Bragg’s diffraction in transmission configuration, offer a promising technology for this purpose. We present our latest results on the development of a sector of a Laue lens, by comparing the alignment accuracy and time stability obtained through fast bonding with a pick & place machine and with an alignment method based on an elastic deformable substrate.

At XRnanotech, a spin-off from the Paul Scherrer Institut (PSI) in Switzerland, we develop X-ray optics to enable experiments at many large-scale research facilities. Our goal is to push the limits of diffractive and refractive X-ray optics by continuously improving the resolution and efficiency enabling new applications in microscopy to make the invisible visible. In X-ray microscopy, Fresnel zone plates (FZPs) are used as high-resolution lenses. Their resolution depends mainly on the size of their smallest outermost zones and many years of development were required in order to push this value into ever-smaller regimes. New procedures have recently also allowed using 3D-printing methods also in the field of X-ray optical applications. For X-ray energies of several keV, a good transmission and refractive properties are achieved along with low surface roughness. Through its versatility, 3D-printing allows manufacturing various types of geometries, X-ray optics, and (resolution) samples alike. The flexibility of this approach allows for achieving previously inaccessible X-ray optical properties. It has allowed us to achieve achromatic focusing with X-rays using a combination of diffractive and refractive optical elements, which we demonstrated for the first time. We will also show some of the recent developments in high efficiency, high resolution, structured beam, and reflection optics.

The hard X-/soft gamma-ray band is still not well explored in astrophysics in spite that several science questions are still unanswered, like the origin of the of the 511 keV positron annihilation line (a mystery 50 years old), the physics of the supernova explosions, the high energy properties (e.g. polarization) of transient sources, like GRB afterglows, magnetars, etc. The main reason is that this band has been explored so far with non-focusing instruments, that can achieve a still unsatisfactory sensitivity and angular resolution. Our goal is the development of a focusing telescope based on a Laue lens made of bent crystals of Silicon and Germanium, that diffract photons in the 50-700 keV band, with unprecedented angular resolution and sensitivity to continuum spectrum and to lines. A satellite mission concept that includes a Laue lens has been submitted to ESA for its long term program “Voyage 2050”. The development of a Laue lens is not a simple task; we have acquired a long experience in terms of the best choice of the crystal material, most efficient diffracting planes, dislocation level, surface roughness, miscut, bending technique, crystal bonding of the crystals to substrates. Results have already been performed and reported. Concerning the crystal bending and bonding, after having explored, for the bending, the lapping procedure, and, for the bonding to its substrate, the use of space qualified resin, to achieve a significantly better reflection efficiency and accuracy in the orientation of the crystals in the lens, we are investigating the possibility to elastically bend the crystals lens by bonding them to their substrates through anodic bonding techniques, with no use of glue. Anodic bonding is a process to seal glass to either silicon or metal without introducing an intermediate layer. It is commonly used to seal glass to silicon wafers in electronics and microfluidics. This bonding technique, well established since tens of years, typically operates with flat substrates. With the aim of aligning a large number of crystals, we aim to manufacture properly bent substrates, which will act as a mold for positioning of the crystals. An equipment is being developed to bend and bond flat crystals on the glass substrates, giving them the prefixed curvature of the lens and a precise positioning. We will report results of this activity.

Potential and applicability of low-Z compounds, like the solid-state materials lithium hydride (LiH), beryllium dihydride (BeH2) and decaborane (B10H14), are studied for use in diffractive-refractive X-ray lenses with an emphasis on applications in space-based astronomy. Optical and chemical properties allow the design of diffraction-limited focusing optics with an efficiency up to 1 sqm x keV within (6 − 18) keV. If scaled to an aperture size of at most 4.9 m, an angular resolution of at least 1 milli-arcsec is achieved. Three-fold lens stacking reduces the outer aspect ratio of the refractive component to 2.5 or less, at an – if combined with segmentation – focal length of no more than about 500 km.