E. Meltchakov et al., Proceeding SPIE 8777 (2013), 877747 Single and multi-channel Al-based multilayer systems for space applications in EUV range E. Meltchakov a* , S. De Rossi a , R. Mercier a , F. Varniere a , A. Jérome a , F. Auchere b , X. Zhang b , M. Roulliay c , and F. Delmotte a a Laboratoire Charles Fabry, Institut d'Optique Graduate School, 91127 Palaiseau, France; b Institut d’Astrophysique Spatiale (IAS), 91403 Orsay, France; c Institut des Sciences Moléculaires d’Orsay (ISMO), 91403 Orsay, France ABSTRACT 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/B 4 C 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 multi- channel 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/B 4 C material combinations. Al-based multilayer systems are proposed as optical coatings in EUV telescopes of future space missions and in other EUV applications. Keywords: multilayer, Aluminum, roughness, EUV, reflectivity 1. INTRODUCTION Many scientific and industrial applications of short-wavelength radiation have become possible with the emergence of normal incidence multilayer coatings, which were proposed nearly 40 years ago. 1,2 In recent years, the use of multilayer mirrors for the EUV and soft x-ray ranges is rapidly expanding at synchrotron radiation and free-electron laser facilities, in high-order harmonic generation techniques, and particularly in the solar imaging instruments of space missions. 3 The solar EUV radiation consists of multiple emission lines originated from electronic transitions between various levels corresponding to different ionization states of elements presented in the solar atmosphere. 4 These states are characteristic to the temperature of solar plasma, therefore a possibility to collect the data on the intensity variation of specific EUV emission lines would provide important information on phenomena occurring in inner and outer regions of the solar atmosphere: chromosphere, transition region, corona and heliosphere. A typical periodic multilayer mirror at fixed incidence angle is normally used to reflect efficiently only one particular wavelength corresponding to the first order Bragg peak. This means that a special instrument is needed for each emission * evgueni.meltchakov@institutoptique.fr; phone +33-164533162; fax +33-169358807; www.institutoptique.fr