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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.

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 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.

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.

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.

Theoretically, periodic three component multilayers as B 4 C/Mo/Si allow an improvement of the reflectivity in the 25 nm-40 nm range as compared to two component multilayers as B 4 C/Si. Optimized B 4 C/Mo/Si and B 4 C/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 B 4 C/Si is 25% at 32 nm and 23% at 38 nm. For B 4 C/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 B 4 C/Mo/Si than for B 4 C/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 B 4 C/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.

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.

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 4d{sup 1}S{sub 0} {yields} 4p{sup 1}P{sub 1} lasing transition is determined to be {approx}400 {micro}m (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 {approx}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.