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Reflection spectra for different grazing angles and reflectivity angular dependences of the Si-SiO2 system with different dioxide thicknesses have been measured in the energy range 40-850 eV, including the Si L2.3 and O K absorption edges. The angular dependences have been used for the dielectric constant determination. By turning a BN hexagonal crystal and using s-polarized radiation a strong reflectivity dependence on the crystal orientation has been detected. Indicatrices of the surface roughness scattering have been recorded for the BNhex crystal surface. The statistical properties of the roughness have been investigated by means of perturbation theory. These measurements were obtained using synchrotron radiation, and the interest in the specific properties of this radiation for such measurements is emphasized.

International audienceMetrology of XUV beams (X-ray lasers, high-harmonic generation and VUV free-electron lasers) is of crucial importance for the development of applications. We have thus developed several new optical systems enabling us to measure the optical properties of XUV beams. By use of a Michelson interferometer working as a Fourier-transform spectrometer, the line shapes of different X-ray lasers have been measured with a very high accuracy (Δλ/λ~10^-6). Achievement of the first XUV wavefront sensor has enabled us to measure the beam quality of laser-pumped as well as discharge-pumped X-ray lasers. A capillary discharge X-ray laser has demonstrated a very good wavefront allowing us to achieve an intensity as high as 3×10^14 W cm^-2 by focusing with a f=5 cm mirror. The sensor accuracy has been measured using a calibrated spherical wave generated by diffraction. The accuracy has been estimated to be as good as λ/120 at 13 nm. Commercial developments are underway. At Laboratoire drsquoOptique Appliquée, we are setting up a new beamline based on high-harmonic generation in order to start the femtosecond, coherent XUV optic

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