Based on our simulations, we have developed a systematic approach to identifying suitable materials for short-period multilayer mirrors operating at 30 keV. We tested many materials and evaluated the performance of each possible combination, focusing on two key figures of merit: integrated reflectivity and peak reflectivity. While it is typical to optimize a multilayer structure to maximize the peak reflectance, we found that this approach can lead to bias. Instead, we propose using integrated reflectivity as a more robust criterion for material selection. Our results demonstrate the effectiveness of this approach in identifying high-performance multilayer mirrors for x-ray applications.
The era of attosecond physics requires complex EUV and soft X-ray optical components with challenging specifications.
Interference coatings with high efficiency, good stability, enhanced selectivity and/or broad bandwidth and phase control are key components to manipulate the ultra-short pulses generated by coherent sources like High Harmonic Generation or X-ray Free Electron Lasers. In this talk, we will discuss details of novel, tailored multilayer optics that we have been developing for the last 20 years for ultrafast sources. We will show that phase-controlled interference coatings provide a powerful tool towards transporting or even compressing attosecond pulses. Measuring the spectral phase of such mirrors requires specific methods that have been developed for the EUV range and extended up to the soft X-ray domain. Finally, we will present the recent development of a delay line with advanced multilayer optics for the femto/attosecond beamlines in Paris-Saclay (ATTOLAB).
Development of multilayer mirrors for the water window (a region between absorption edges of carbon and oxygen, from 282 to 533 eV) remains quite a challenge. Proposed 25 years ago, the Cr/Sc multilayer provides theoretical reflectivity about 60% at near-normal incidence near the Sc L2,3 edge. However, the maximum measured peak reflectance achieved so far just slightly exceeds 20%. We report on our approach to design highly reflective Cr/Sc-based multilayer coatings using a process of nitridation of chromium during deposition and adding boron carbide as a third material in the multilayer structure. We will report on our strategy of optimisation of the CrN/B4C/Sc multilayer system and discuss the main findings and results. The peak reflectance as high as 32% at 397 eV was measured with this type of coating which proves to be potentially interesting for various water window applications such as x-ray microscopy.
We present here experimental results and modeling of multilayer gratings developed for the EUV spectro-imager abroad Solar-C mission. Periodic Al/Mo/SiC multilayers were optimized and deposited by magnetron sputtering on high groove density lamellar gratings with various depths. All grating samples were characterized before and after multilayer deposition by atomic force microscopy (AFM) and by grazing incidence x-ray reflectometry (GIXR) at 8.05 keV. AFM measurements reveal the surface prole evolution when the number of deposited layers increases. This effect is confirmed with a transmission electron microscope cross-section analysis. The EUV diffraction efficiency of the multilayer gratings was measured by monochromatic synchrotron radiation on the XUV Metrology beamline at SOLEIL Synchrotron. The results are in good agreement with the model simulated by rigorous coupled-wave analysis and using structural parameters determined by AFM and GIXR. The measured near-normal incidence first-order efficiency reaches a maximum of about 9.27%, 6.54%, and 7.18% at wavelengths of 27.3 nm, 21.4 nm, and 19.4 nm respectively.
In the last decades, extreme ultraviolet (EUV) multilayer coatings have proved to be key components in the development and success of telescope imagers onboard space missions to image the solar corona. More recently, we have been able to significantly increase the efficiency, to develop new functionality and to extend the range of operation of EUV multilayer coatings, thanks to the development and optimization of new material combinations and new coating designs. Furthermore, multilayer mirrors with high efficiency, good stability, enhanced selectivity and/or broad bandwidth and phase controlled are key components to manipulate the ultra-short pulses generated by coherent sources.
In this presentation, we will review the recent development of EUV multilayer optics for solar imaging, in particular for the two Solar Orbiter EUV telescopes, which produced the closest images of the Sun in 2022 with the first dual-band EUV coatings. We will also discuss multilayer mirrors for pico-, femto- and attosecond sources, including the recent development of a delay line with advanced multilayer optics for the femto/attosecond beamlines in Paris-Saclay (ATTOLAB).
We will finally discuss the problem of inaccuracies in the available EUV optical properties of materials that makes it difficult to design and calibrate such instruments. We will discuss solutions to improve the accuracy in the determination of optical properties.
Precise knowledge of the wavelength-dependent refractive index of materials is required to accurately design, build and calibrate the in-band and out-of-band performance of EUV/x-ray instruments. Such instruments include exposure and patterning tools, imagers, microscopes and spectrometers for photolithography, plasma physics, synchrotron and laser science, solar physics and astrophysics. Yet, the available refractive index values in the EUV/x-ray are often unreliable. This is due to the extreme sensitivity of materials to contamination and oxidation, to the difficulty in fabricating appropriate thin film samples, to the presence of near-edge absorption fine structure, and to multiple reflections present at the longer EUV wavelengths, which are complicating the measurements. We are presenting a new methodology to measure the EUV refractive index and new sets of measurements for several important EUV materials. We use combinations of transmittance and reflectance data in the spectral range 826.5 eV (1.5 nm) to 15 eV (82.5 nm) and reveal for the first time highly resolved fine structure in the regions of L, M, N and O absorption edges, in both the absorptive and dispersive portions of the refractive index, resulting in improvements of up to a factor of 3 compared to earlier values. The improved refractive index accuracy is validated by sum rule tests and by simulating experimental data of multilayer coatings containing these materials.
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter mission will image the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral ranges. The development of the EUI instrument has been successfully completed with the optical alignment of its three channels’ telescope, the thermal and mechanical environmental verification, the electrical and software validations, and an end-toend on-ground calibration of the two-units’ flight instrument at the operating wavelengths. The instrument has been delivered and installed on the Solar Orbiter spacecraft, which is now undergoing all preparatory activities before launch.
The thin film optical constants are key parameters to carry out optical simulation or optimization of multilayer mirrors with high efficiency. However, for most materials, different sets of optical constants can be found in the literature especially in the EUV range, as these parameters are not as well-known in the EUV as in the visible or wavelength range. In this work, we have used several reflectance and transmittance measurements in the wavelength range from 10 nm to 60 nm. Different optical constant files have been tested and compared with the IMD simulation software. We will present some experimental spectra and theoretical simulations to highlight the existing problem on the reliability of optical constants sets and to discuss potential solutions. We focus our research on a few materials of particular interest in the EUV range such as aluminum, aluminum oxide, molybdenum, zirconium, magnesium, silicon carbide, and boron carbide. These analyses lead us to select the most reliable and accurate optical constants set, or to create the best one from the concatenation of existing data for each material of interest.
We study Cr/Sc-based multilayer mirrors designed to work in the water window range using hard and soft x-ray reflectivity as well as x-ray fluorescence enhanced by standing waves. Samples differ by the elemental composition of the stack, the thickness of each layer, and the order of deposition. This paper mainly consists of two parts. In the first part, the optical performances of different Cr/Sc-based multilayers are reported, and in the second part, we extend further the characterization of the structural parameters of the multilayers, which can be extracted by comparing the experimental data with simulations. The methodology is detailed in the case of Cr/B4C/Sc sample for which a three-layer model is used. Structural parameters determined by fitting reflectivity curve are then introduced as fixed parameters to plot the x-ray standing wave curve, to compare with the experiment, and confirm the determined structure of the stack.
After a brief review of recent results achieved at Laboratoire Charles Fabry concerning high reflectivity mirrors, mirrors with enhanced spectral purity and broadband mirrors, we describe a new approach to design high efficiency multilayer mirrors for application on a broad spectral range. The main idea is to use 2 “spacer” materials (Aluminum and Scandium) in combination with a third material (Boron carbide or Silicon Carbide). We present several examples of design optimization using such multilayers. Finally, we show the first preliminary experimental results with Al/Sc/B4C and Al/Sc/SiC multilayers deposited by ion beam sputtering.
The Extreme Ultraviolet Imager (EUI) is one of the remote sensing instruments on-board the Solar Orbiter mission. It will provide dual-band full-Sun images of the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm), and high resolution images of the solar disk in both extreme ultraviolet (17.1 nm) and vacuum ultraviolet (Lyman-alpha 121.6 nm). The EUI optical design takes heritage of previous similar instruments. The Full Sun Imager (FSI) channel is a single mirror Herschel design telescope. The two High Resolution Imager (HRI) channels are based on a two-mirror optical refractive scheme, one Ritchey-Chretien and one Gregory optical design for the EUV and the Lyman-alpha channels, respectively. The spectral performances of the EUI channels are obtained thanks to dedicated mirror multilayer coatings and specific band-pass filters. The FSI channel uses a dual-band mirror coating combined with aluminum and zirconium band-pass filters. The HRI channels use optimized band-pass selection mirror coatings combined with aluminum band-pass filters and narrow band interference filters for Lyman-alpha. The optical performances result from accurate mirror manufacturing tolerances and from a two-step alignment procedure. The primary mirrors are first co-aligned. The HRI secondary mirrors and focal planes positions are then adjusted to have an optimum interferometric cavity in each of these two channels. For that purpose a dedicated alignment test setup has been prepared, composed of a dummy focal plane assembly representing the detector position. Before the alignment on the flight optical bench, the overall alignment method has been validated on the Structural and Thermal Model, on a dummy bench using flight spare optics, then on the Qualification Model to be used for the system verification test and qualifications.
The Solar Orbiter mission is composed of ten scientific instruments dedicated to the observation of the Sun’s atmosphere and its heliosphere, taking advantage of an out-of ecliptic orbit and at perihelion reaching a proximity close to 0.28 A.U. On board Solar Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun image sequences of the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm), and high-resolution image sequences of the solar disk in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet (121.6 nm). The EUI concept uses heritage from previous similar extreme ultraviolet instrument. Additional constraints from the specific orbit (thermal and radiation environment, limited telemetry download) however required dedicated technologies to achieve the scientific objectives of the mission. The development phase C of the instrument and its sub-systems has been successfully completed, including thermomechanical and electrical design validations with the Structural Thermal Model (STM) and the Engineering Model (EM). The instrument STM and EM units have been integrated on the respective spacecraft models and will undergo the system level tests. In parallel, the Phase D has been started with the sub-system qualifications and the flight parts manufacturing. The next steps of the EUI development will be the instrument Qualification Model (QM) integration and qualification tests. The Flight Model (FM) instrument activities will then follow with the acceptance tests and calibration campaigns.
Phase controlled multilayer mirrors provide an efficient solution to transport, focus and/or compress attosecond pulses in
the extreme ultraviolet (EUV) domain (30 – 100 eV). In this spectral range, one can access the spectral phase of the
multilayer stack by measuring the photocurrent generated at the mirror surface as a function of the incoming photon
energy. It has been already demonstrated that one can extract the spectral phase from such measurements under specific
hypotheses. In this paper, we present the experimental protocol for such measurements and discuss the validity of this
technique in the EUV and in the soft x-ray domains. In the EUV spectral range, our experimental results are in good
agreement with simulations. However, the previous hypotheses are no longer valid at shorter wavelengths, in the soft xrays
domain. This is mainly due to the fact that the electron mean free path becomes comparable to the individual layer
thickness in the multilayer mirror. Here we propose a new method that enables one to extend the validity of phase
characterization using photocurrent measurements in the soft x-ray domain (100 – 1000 eV). We present the first
experimental results concerning the phase characterization of Cr/Sc multilayer mirrors in the water window and compare
these results with simulation.
The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission will provide full-sun and high-resolution image sequences of the solar atmosphere at selected spectral emission lines in the extreme and vacuum ultraviolet. After the breadboarding and prototyping activities that focused on key technologies, the EUI project has completed the design phase and has started the final manufacturing of the instrument and its validation. The EUI instrument has successfully passed its Critical Design Review (CDR). The process validated the detailed design of the Optical Bench unit and of its sub-units (entrance baffles, doors, mirrors, camera, and filter wheel mechanisms), and of the Electronic Box unit. In the same timeframe, the Structural and Thermal Model (STM) test campaign of the two units have been achieved, and allowed to correlate the associated mathematical models. The lessons learned from STM and the detailed design served as input to release the manufacturing of the Qualification Model (QM) and of the Flight Model (FM). The QM will serve to qualify the instrument units and sub-units, in advance of the FM acceptance tests and final on-ground calibration.
Since more than 20 years, Laboratoire Charles Fabry and Institut d’Astrophysique Spatiale are involved in development
of the EUV multilayer coating for solar imaging. Previous instruments, such as the SOHO EIT and STEREO EUVI
telescopes, employed the Mo/Si multilayer coatings, which offered at that time the best efficiency and stability. We
present here recent results of the development of highly efficient EUV multilayers coatings at 17.4 nm and 30.4 nm for
the Solar Orbiter mission. New multilayer structures, based on a combination of three materials including aluminum,
have been optimized both theoretically and experimentally. We have succeeded to reduce interfacial roughness of Albased
multilayers down to 0.5 nm via optimization of the multilayer design and the deposition process. The EUV peak
reflectance of Al/Mo/SiC and Al/Mo/B4C multilayer coatings reaches 56% at 17.4 nm, the highest value reported up to
now for this wavelength. We have also optimized specific bi-periodic structures that possess two reflection bands in the
EUV range with high spectral selectivity. The EUV reflectivity of these Al-based dual-band coatings are compared with
the Si/Mo/B4C baseline coating for Solar Orbiter. Since the stability of reflecting multilayer coating is an important issue
for space missions, we have also studied the temporal stability as well as the resistivity of the coatings to thermal cycling
and to proton irradiation. Experimental results confirm that Al/Mo/SiC and Al/Mo/B4C multilayer coatings are good
candidates for the Solar Orbiter EUV imaging telescopes.
A new channel of an X-ray broadband spectrometer has been developed for the 2 – 4 keV spectral range. It uses a spectral filtering by using a non-periodic multilayer mirror. This channel is composed by a filter, an aperiodic multilayer mirror and a detector. The design and realization of the optical coating mirror has been defined such as the reflectivity is above 8% in almost the entire bandwidth range 2 – 4 keV and lower than 2% outside. The mirror is optimized for working at 1.9° grazing incidence. The mirror is coated with a stack of 115 chromium / scandium (Cr / Sc) non-periodic layers, between 0.6 nm and 7.3 nm and a 3 nm thick top SiO2 layer to protect the stack from oxidization. To control thin thicknesses, we produced specific multilayer mirrors which consist on a superposition of two periodic Cr / Sc multilayers with the layer to calibrate in between. The mirror and subnanometric layers characterizations were made at the “Laboratoire Charles Fabry” (LCF) with a grazing incidence reflectometer working at 8.048 keV (Cu Kα radiation) and at the synchrotron radiation facility SOLEIL on the hard X-ray branch of the “Metrology” beamline. The reflectivity of the mirrors as a function of the photon energy was obtained in the Physikalisch Technische Bundesanstalt (PTB) laboratory at the synchrotron radiation facility Bessy II.
We report on further development of reflective multilayer coatings containing aluminum as low absorbing material for the extreme ultra-violet (EUV) applications, in particular for solar physics. Optimizations of the multilayer design and deposition process have allowed us to produce Al-based multilayers having relatively low interface roughness and record EUV reflectances in the range from 17 to 40 nm. The peak reflectance values of 56 % at 17.5 nm, 50 % at around 21 nm, and 42 % at 32 nm were achieved with new three-material multilayers Al/Mo/SiC and Al/Mo/B4C at near-normal incidence. We observe a good temporal stability of optical parameters of the multilayers over the period of 4 years. Moreover, the multilayer structure remains stable upon annealing at 100 °C in air during several weeks. We will discuss the optical properties of more complex Al-based systems with regard to the design of multilayer coatings that reflect more than one wavelength and reject some others within the spectral range from 17 to 40 nm. Such multichannel systems with enhanced reflectance and selectivity would provide a further advance in optical performance and compactness of EUV solar imaging instruments. We will discuss general aspects of design, optimization and fabrication of single- and multi-channel multilayer mirrors made with the use of aluminum. We will present recent results on the EUV reflectivity of multilayer coatings based on the Al/Mo/SiC and Al/Mo/B4C material combinations. Al-based multilayer systems are proposed as optical coatings in EUV telescopes of future space missions and in other EUV applications.
The Solar Orbiter mission will explore the connection between the Sun and its heliosphere, taking advantage of an orbit
approaching the Sun at 0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI) will provide full-sun and
high-resolution image sequences of the solar atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet.
To achieve the required scientific performances under the challenging constraints of the Solar Orbiter mission it was
required to further develop existing technologies. As part of this development, and of its maturation of technology
readiness, a set of breadboard and prototypes of critical subsystems have thus been realized to improve the overall
instrument design.
The EUI instrument architecture, its major components and sub-systems are described with their driving constraints and
the expected performances based on the breadboard and prototype results. The instrument verification and qualification
plan will also be discussed. We present the thermal and mechanical model validation, the instrument test campaign with
the structural-thermal model (STM), followed by the other instrument models in advance of the flight instrument
manufacturing and AIT campaign.
Membranes a few hundred nanometers thick are used in EUV optics to make, for example, beams splitters or passband
filters. Despite their necessity in numerous applications these components are, because of their thinness, extremely
fragile and their implementation in space instruments is always difficult. The authors are developing thin film filters for
the Full Sun Imager, one of the EUV telescopes on board the Solar Orbiter mission with objectives of high optical
efficiency and mechanical strength. These filters are specifically designed to isolate one or the other of the two
passbands (17.4 and 30.4 nm) reflected by the telescope's dual band mirror coating. In this paper we present the optical
properties of the prototype components.
In this paper, we present the development of Al-based multilayer mirrors for the spectral range [17 nm - 34 nm]. The
purpose of presented study is to optimize the deposition of Al-based multilayers by the ion beam sputtering (IBS)
technique according to several parameters such as the ion beam current and the angle of inclination of targets, which
allowed us to vary the energy of ad-atoms deposited onto a substrate. We expected to achieve good reflectivity values
for both two- and three-material stacks: aluminum/molybdenum Al/Mo, aluminum/molybdenum/boron carbide
Al/Mo/B4C and aluminum/molybdenum/silicon carbide Al/Mo/SiC. We have undertaken a series of structural and
chemical analyses of these systems. We present their optical characteristics in the EUV range.
We report on further development of three-material multilayer coatings made with a use of aluminum for the extreme
ultra-violet (EUV) applications such as solar physics, high-order harmonic generation or synchrotron radiation. It was
found that an introduction of refractory metal in Al-based periodic stack helps to reduce significantly an interfacial
roughness and provides for a higher theoretical reflectance in the spectral range from 17 to 40 nm. The normal incidence
reflectivity as high as 55 % at 17 nm, 50 % at 21 nm and 42 % at 30 nm was achieved with the new Al/Mo/SiC and
Al/Mo/B4C multilayer mirrors, which have been optimized, fabricated and characterized with x-rays and synchrotron
radiation. A good temporal and thermal stability of the tri-component Al-based multilayers has been observed over 3
years.
We present the design, the optimization and the realization of multilayer mirrors for the transport and the compression of
attosecond pulses generated by high harmonics emission from 35 eV to 55 eV. At wavelength characterizations have
been performed on an attosecond source. We explore also the phase determination of the complex reflectivity from
photon-electron emission measurement on synchrotron beamline.
With regards to the future Laser Megajoules french facility (LMJ), our laboratory is developing advanced time-resolved
High Resolution X-ray Imaging (HRXI) systems to diagnose laser produced plasma. Shrapnel and X-ray
loading on this laser imposes to place any HRXI as far away from the source as possible. Grazing incidence X-ray
microscopes are the best solution to overpass this limitation. These imagers combine therefore grazing X-ray
microscope and camera. We designed imaging diagnostics, mainly with a long working distance (> 50 cm) and high
spatial resolution. All of them are composed of single or multi-toroïdal(s) mirror(s).
To increase the bandwidth of reflectivity of all these mirrors, multilayer coatings have been deposited. We present
mainly microscopes using non-periodic W/SiC multilayer coatings (Supermirrors), developed in collaboration with
Institut d'Optique.
Supermirrors were designed for a first set of diagnostics to work at 0.7° grazing incidence. Secondly, we have
implemented this supermirror on a Wolter-type microscope used at a smaller grazing incidence (0.6° angle) in order
to increase the bandwidth of reflectivity up to 12 keV.
Metrology for x-ray reflectance in the whole range on the synchrotron radiation facility BESSY II is also presented.
In this paper, we present a brief history of EUV multilayer mirrors and recent results achieved at Institut d'Optique in the
fields of space science and ultra-fast pulses. Concerning space science, we present two solutions to improve reflectivity
of EUV multilayer for solar imaging: three material multilayers and Al-based multilayers. Concerning attosecond pulses,
we demonstrate the possibility to realize multilayer mirrors for an efficient transport of high harmonics on a broad
energy band with high efficiency.
We present the characterization of Al/SiC periodic multilayers designed for optical applications. In some samples, a thin
layer of W or Mo is added at the SiC-on-Al interfaces. We use x-ray reflectivity (XRR) in order to determine the
parameters of the stacks, i.e. thickness and roughness of all the layers. We have performed x-ray emission spectroscopy
(XES) to identify the chemical state of the Al and Si atoms present within the structure from an analysis of the shape of
the Al Kβ and Si Kβ emission bands. Finally, time of flight secondary ion mass spectrometry (ToF-SIMS) is used to
obtain the depth profile of the different elements present within the studied stacks. A fit of the XRR curves shows that
the Al/SiC multilayer present large interfacial roughness (up to 2.8 nm), which is decreased considerably (down to 1 nm
or less) when the refractory metal layers are introduced in the periodic structure. The combination of XES and ToFSIMS
allows us to conclude that in these systems the roughness is a purely geometrical parameter and not related to
chemical interfacial reactions.
Through its participation to European programs, SAGEM has worked on the design and manufacturing of normal
incidence collectors for EUV sources. By opposition to grazing incidence, normal incidence collectors are expected to
collect more light with a simpler and cheaper design. Designs are presented for the two current types of existing sources:
Discharge Produced Plasma (DPP) and Laser Produced Plasma (LPP). Collection efficiency is calculated in both cases. It
is shown that these collectors can achieve about 10 % efficiency for DPP sources and 40 % for LPP sources. SAGEM
works on the collectors manufacturability are also presented, including polishing, coating and cooling. The feasibility of
polishing has been demonstrated with a roughness better than 2 angstroms obtained on several materials (glass, silicon,
Silicon Carbide, metals...). SAGEM is currently working with the Institut d'Optique and the Laboratoire des Materiaux
Avancés on the design and the process of EUV coatings for large mirrors. Lastly, SAGEM has studied the design and
feasibility of an efficient thermal control, based on a liquid cooling through slim channels machined close to the optical
surface.
HECOR (HElium CORonagraph) is a coronagraph designed to observe the solar corona at 30.4 nm between 1.2 and 4
solar radii. The instrument is part of the Herschel sounding rocket payload to be flown from White Sands Missile Range
in December 2007. Much like for neutral hydrogen, the residual singly ionized helium present in the corona can be
detected because it resonantly scatters the intense underlying chromospheric radiation. Combined with the simultaneous
measurements of the neutral hydrogen corona made by SCORE, the other coronagraph of the Herschel payload, the
HECOR observations will provide novel diagnostics of the solar wind outflow. HECOR is an externally occulted
coronagraph of very simple design. It uses a triple-disc external occulting system, a single off axis multilayer coated
mirror and a CCD camera. We present measurements of the EUV mirror roughness and reflectivity, tests of the image
quality, and measurements of the stray light rejection performance. The mirror uses a novel multilayer design with three
components that give HECOR a high throughput.
The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is being developed to be
part of the PROBA2 payload, an ESA technological mission to be launched in early 2008. SWAP is directly derived
from the concept of the EIT telescope that we developed in the '90s for the SOHO mission. Several major innovations
have been introduced in the design of the instrument in order to be compliant with the requirements of the PROBA2
mini-satellite: compactness with a new of-axis optical design, radiation resistance with a new CMOS-APS detector, a
very low power electronics, an athermal opto-mechanical system, optimized onboard compression schemes combined
with prioritization of collected data, autonomy with automatic triggering of observation and off-pointing procedures in
case of Solar event occurrence, ... All these new features result from the low resource requirements (power, mass,
telemetry) of the mini-satellite, but also take advantage of the specificities of a modern technological platform, such as
quick pointing agility, new powerful on-board processor, Packetwire interface and autonomous operations.
These new enhancements will greatly improve the operations of SWAP as a space weather sentinel from a low Earth
orbit while the downlink capabilities are limited. This paper summarizes the conceptual design, the development and the
qualification of the instrument, the autonomous operations and the expected performances for science exploitation.
Among X-ray and extreme ultraviolet light sources able to produce shorter and shorter, coherent and intense pulses, High
order harmonics generated in rare gases are currently the unique way to generate attosecond pulses. However, the
manipulation and transport of attosecond pulses require the development of dedicated optics for reaching specific
characteristics in terms of amplitude but also in terms of spectral phase control. We present here a multilayer design for
chirp compensation of attosecond pulses. We also present an application of these multilayers mirrors for attosecond train
pulse holography experiment with high harmonics. This experience took benefit of both temporal and spatial phase
properties of high harmonics. A resolution of 750 nm has been achieved by using a 350 as train pulse for the reference
wave constituted of four consecutive harmonics (λ=28 nm to λ=41 nm). This new method will allow making ultra fast
movies with attosecond resolution of transient phenomena with quasi-3D resolution.
The development of new high power EUV sources and EUV space imaging requires optics having specific
properties which depend on applications and operating conditions. These both applications are very different in the
working multilayers environment. For the high power sources, multilayers are submitted to short pulses with high
energy peak whereas, for the space imaging, multilayers are submitted to continuous flux with low level. Moreover
photon energy and environment for both applications may be different. The environment may affect structure and top
layer contamination when optics are stored, handled, mounted on the final device and finally operating. Main
environmental parameters investigated are temperature and humidity variation.
One objective is the optimisation of multilayer coatings to offer the highest resistance under photonic, ionic
fluxes and temperature cycle. This means that interfacial diffusion between thin layers and degradation of the capping
layers have to be avoided or reduced. The present study relies with designing, depositing and testing different structures
of multilayer coatings in order to minimise the influence of the environment.
Multilayer coatings based on molybdenum, silicon and silicon carbide materials have been deposited by magnetron
sputtering on silicon and zerodur substrates. Samples were submitted to radiations emitted by an EUV source at
wavelength closed to 13.5 nm. Furthermore they were also submitted to thermal cycles and annealing under warm
humidity in the aim to simulate extremes storage or handling conditions as space mission's conditions.
The damages and the performance of the multilayers were evaluated by using grazing incidence reflectometry
at 0.154 nm and EUV reflectometry at the operating wavelength.
After a presentation of the multilayer design, deposition and metrology tools, we will describe the different
environmental effects on the coatings to take in care during EUV source exposure, handling and storage conditions.
First results on multilayers performances to EUV source exposure and space specification tests are presented. Main
damages studies were on annealing, thermal cycling and warm humidity.
Theoretically, periodic three component multilayers as B4C/Mo/Si allow an improvement of the reflectivity in the 25 nm-40 nm range as compared to two component multilayers as B4C/Si. Optimized B4C/Mo/Si and B4C/Si multilayers have been deposited by magnetron sputtering and ion beam sputtering. The multilayers have been characterized by x-ray grazing reflectometry (λ = 0.154 nm) and synchrotron radiation measurements at near normal incidence. The maximum experimental reflectivity for B4C/Si is 25% at 32 nm and 23% at 38 nm. For B4C/Mo/Si multilayers, we obtained an experimental reflectivity of 34% at 32 nm and 29% at 39.5 nm. Moreover the width of the Bragg peak is larger for B4C/Mo/Si than for B4C/Si. We have used these multilayers in a non periodical structure in order to produce broadband mirrors. It consists of the superposition of two periodic B4C/Mo/Si multilayers with different period thickness. Theoretical optimization of such structure by simulation is presented. Preliminary experimental results demonstrate the interest of such structure : two broadband mirrors have been deposited and measured over a wide wavelength range (12 nm to 45 nm). The first mirror presents a broadband spectrum centered at 32 nm with peak reflectivity of 22% and bandwidth larger than 9 nm. The second mirror has been optimized to produce theoretically an average reflectivity of 19% from 25 nm to 35 nm.
We present an experimental study of aging and thermal stability of Sc/Si multilayers deposited by magnetron sputtering. These multilayers have been characterized by using hard X-ray grazing incidence reflectometry at 0.154 nm and synchrotron radiation reflectometry at near normal incidence. The reflectivity was found to be stable after one year. A maximum reflectivity of 46% has been measured at 46 nm. However a 20% relative decrease of the reflectivity have been observed after one hour thermal annealing at 200°C. In order to improve thermal stability, we studied two different barriers layers (B4C and ScN ). We compare the decrease of peak reflectivity and its wavelength shift after one hour annealing at 200°C under argon atmosphere. The best result was observed with the design using 0.3 nm B4C barrier layers. A relative decrease of 2% of the reflectivity peak has been observed with this design as compared to a 20% decrease without barrier layers.
In the race towards attosecond (as) pulses for which high order harmonics generated in rare gases are the best candidates, both the Harmonic spectral range and spectral phase have to be controlled. We present in this proceeding four mirrors numerically optimized and designed to compensate for the intrinsic Harmonic chirp recently discovered and which is responsible for a temporal broadening of the pulses. They are capable of compressing the duration down to 100 as. We present the fabrication of those aperiodic multilayers and show the measurement of reflectivity, which prooves that those multilayers are in agreement with the specifications and so let us think that they will be able to compress attosecond high harmonics trains.
Imaging of the solar corona by selecting Fe IX (λ=17.1nm,), Fe XII (λ=19.5nm), Fe XV (λ=28.4nm) and He II (λ=30.4nm) emission lines with a Ritchey-Chretien telescope requires to coat the optics with multilayers having a high accuracy in their layer thicknesses, a high reflectivity and an optimal bandpass. Multilayers were simulated in order to determine the most adequate formula for each wavelength channel. Mo/Si coatings were deposited by using the ion beam sputtering technique in a high vacuum chamber equipped with a micro balance and an in-situ reflectometer. The multilayers were studied by grazing angle reflectometry at 0.1541nm, and their reflectances around the operating wavelengths were measured on the SA62 IAS/LURE beam line of the SuperACO
synchrotron facility located at Orsay. In addition, aging versus time and behavior of the multilayers under a rapid thermal annealing were investigated.
Performances of the ion-beam deposited multilayers have been improved compared to the Mo/Si coatings obtained in the past by the e-beam evaporation technique for the SOHO mission Extreme UV Imaging Telescope (EIT). The EUVI telescopes for the STEREO mission are being proceduced by depositing these new generation of multilayers onto
primary and secondary mirrors. The reflectivity measurements on a telescope are presented.
The MAGRITTE telescopes are part of the SHARPP instrument suite, part of the Solar Dynamics Observatory (SDO), a NASA spacecraft to be launched in a geostationnary orbit in 2007. The MAGRITTE instrument package will provide high resolution images of the solar corona at high temporal frequency simultaneously in 5 EUV and in Ly-α narrow bandpasses. The 1.4 R0 MAGRITTE common field of view complements the other SHARPP instruments, as well as its spectral coverage with 6 narrow bandpasses located within the 19.5 to 120 nm interval. The key challenges of the MAGRITTE instrument are a high angular resolution (0.66 arcsec/pixel) with a high responsivity (exposure times smaller than 8 sec), combined with restricted spacecraft resources. The design of MAGRITTE is based on a high performance off-axis Ritchey-Chretien optical system combined with a large detector (4 K x 4 K, 12 µm pixel). The tight pointing stability performance of 1.2 arcsec over the image exposure time requires an active image motion control, using pointing information of a Guide Telescope, to compensate low frequency boresight variations produced by spacecraft jitter. The thermomechanical design and the mirror polishing are highly critical issues in the instrument design. This paper presents the MAGRITTE design concept with the expected performances based on a realistic error budget. The mirror polishing concept and performances are discussed.
The Extreme Ultraviolet Imager (EUVI) is part of the SECCHI instrument suite currently being developed for the NASA STEREO mission. Identical EUVI telescopes on the two STEREO spacecraft will study the structure and evolution of the solar corona in three dimensions, and specifically focus on the initiation and early evolution of coronal mass ejections (CMEs). The EUVI telescope is being developed at the Lockheed Martin Solar and Astrophysics Lab. The SECCHI investigation is led by the Naval Research Lab. The EUVI’s 2048 x 2048 pixel detectors have a field of view out to 1.7 solar radii, and observe in four spectral channels that span the 0.1 to 20 MK temperature range. In addition to its view from two vantage points, the EUVI will provide a substantial improvement in image resolution and image cadence over its predecessor SOHO-EIT, while complying with the more restricted mass, power, and volume allocations on the STEREO mission.
We present the longitudinal coherence measurement of the transient inversion collisional x-ray laser for the first time. The Ni-like Pd x-ray laser at 14.68 nm is generated by the LLNL COMET laser facility and is operating in the gain-saturated regime. Interference fringes are produced using a Michelson interferometer setup in which a thin multilayer-coated membrane is used as a beam splitter. The longitudinal coherence length for the picosecond duration 4d1S0 -> 4p1P1 lasing transition is determined to be ~400 µm (1/e HW) by adjusting the length of one interferometer arm and measuring the resultant variation in fringe visibility. This is four times improved coherence than previous measurements on quasi-steady state schemes largely as a result of the narrower line profile in the lower temperature plasma. The inferred gain-narrowed linewidth of ~0.29 pm is also substantially narrower than previous measurements on quasi-steady state x-ray laser schemes. This study shows that the coherence of the x-ray laser beam can be improved by changing the laser pumping conditions. The x-ray laser is operating at 4 - 5 times the transform-limited pulse.
Metrology of XUV beams and more specifically X-ray laser (XRL) beam is of crucial importance for development of applications. We have then developed several new optical systems enabling to measure the x-ray laser optical properties. By use of a Michelson interferometer working as a Fourier-Transform spectrometer, the line shapes of different x-ray lasers have been measured with an unprecedented accuracy (δλ/λ~10-6). Achievement of the first XUV wavefront sensor has enable to measure the beam quality of laser-pumped as well as discharge pumped x-ray lasers. Capillary discharge XRL has demonstrated a very good wavefront allowing to achieve intensity as high 3*1014 Wcm-2 by focusing with a f = 5 cm mirror. The measured sensor accuracy is as good as λ/120 at 13 nm. Commercial developments are under way.
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