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The “Commissariat a l’energie atomique et aux energies alternatives” (CEA) studies and designs advanced X-ray diagnostics to probe dense plasmas produced at the future Laser MegaJoule (LMJ) facility. Mainly for X-ray imaging with high spatial resolution, different types of multilayer mirrors were developed to provide broadband X-ray reflectance at grazing incidence. These coatings are deposited on two toroidal mirror substrates that are then mounted into a Wolter-type geometry (working at a grazing angle of 0.45°) to realize an X-ray microscope. Non-periodic (depth graded) W/Si multilayer can be used in the broad photon energy range from 2 keV to 22 keV. A third flat mirror can be added for the spectral selection of the microscope. This mirror is coated with a Mo/Si multilayer for which the d-spacing varies in the longitudinal direction to satisfy the Bragg condition within the angular acceptance of the microscope and also to compensate the angular dispersion due to the field of the microscope. We present a study of such a so-called Gobel mirror which was optimized for photon energy of 10.35 keV. The three mirrors were coated using magnetron sputtering technology by Xenocs SA. The reflectance in the entire photon energy range was determined in the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the synchrotron radiation facility BESSY II in Berlin.

Within the framework of its researches on Inertial Confinement Fusion (ICF), the “Commissariat a l’Energie Atomique et aux Energies Alternatives” (CEA) studies and designs advanced X-ray diagnostics in order to probe dense plasmas produced by Laser facilities. The final goal for those diagnostics is to be used during experiments on the Laser Megajoules french facility (LMJ) at Bordeaux. We present two types of advanced monochromatic High Resolution X-ray Imaging microscopes (HRXI) who have high spatial resolution capability (3-6 μm) and high efficiency. The first microscope so-called MERSSIX consists of two toroidals mirrors mounted into a Wolter type geometry and working at grazing incidence. Non-periodic multilayer (depth graded) mirrors were developed with special coatings designed to provide broadband X-ray reflectance in the 1 - 22 keV energy range. Associated to this Wolter microscope a potential monochromatic third mirror coated with a multilayer stack can be used for monochromatic application in that range. The second microscope is composed of a transmission gold Fresnel Phase Zone Plate (FPZP) and a narrow bandwidth multilayer mirror. We present an experimental study with X-ray plasma-source and a complete characterization of the X-ray optics on the synchrotron radiation facility BESSY II. Potentialities (a few μspatial resolution monochromatic images) and complementarity of these two monochromatic HRXI are discussed. The design of the MLs for each microscope is detailed.

We report the results of two experiments on non-stationary neutron optics. In the first one we measured the spectrum of ultracold neutrons (UCN) diffracted on a phase grating moving across the beam. A discrete spectrum is found in good agreement with theory. This purely quantum effect may be interpreted as resulting from phase modulation of the neutron wave. In the second experiment we observed the UCN focusing in time. Periodical acceleration and deceleration of neutrons is produced by diffraction on a phase grating with a variable space period.

Experimental activity in the field of neutron spin precession optics was started some years ago by the Achiva et al. In 1999 we demonstrated the unique possibility of the IN15 spin-echo instrument of ILL for such kind of investigations. In the present paper we shall report some new results. Larmor precession of neutron spin was used as a clock for the measurement of the delay in neutron time of flight, caused by the difference in neutron velocities in vacuum and in matter. Coherence length density was measured for a number of materials with an accuracy of some percent. It was found that diamagnetic properties of materials may affect the results remarkably. The giant anisotropic diamagnetic acceptability was found for the pyrolytic graphite. The achieved accuracy in the delay time, (3–5)×10 −10 s, permits us to perform a number of new experiments for the measurement of neutron interaction time with different quantum objects.

We report the first use of a long wavelength cut-off filter for a polarized cold neutron beam. If a supermirror polarizer is used, the degree of polarization of neutrons with relatively long wavelengths, say, longer than 1.3 nm, is poor and difficult to determine. The filter we used in this paper separates these undesired neutrons from the beam. The device is 8 mm long and consists of a stack of 118 Si wafers, whose surfaces are covered with m=3 Ni/Ti supermirrors (see Fig. 1 ) Download : Download high-res image (738KB) Download : Download full-size image Fig. 1 . Photograph of the wavelength cut-off filter. The neutron beam enters through the end of the Si wafers. B4C is added around the filter in order to prevent neutrons not filtered from reaching the detector. . The performance of this filter is described.

By characterization of Fe/Si multilayers with a range of layer thickness we show that the diffusion of Si into Fe makes the Si layers 11.4±1.2 A thinner than expected. We can use this information to improve growth of multilayers with high precision of layer thickness. Furthermore, the interdiffusion of Si into Fe creates a magnetically dead layer at the interface of about 5 A. We have used reactive sputtering of Si with N 2 as a method to reduce interdiffusion. With the ability to control thickness more accurately and to reduce interdiffusion we have deposited polarizing Fe/SiN x supermirrors with neutron spin-up reflectivity in excess of 85% at λ / θ =0.3°/ λ (i.e., “ m =3”), allowing us to obtain neutron polarization above 95% in reflection geometry and above 90% in transmission geometry, respectively.

We have investigated the interfacial roughness of a W/Si multilayer sputtered at high Ar gas pressure. The roughness exponents as determined from diffuse X-ray scattering agree well with the Huygens-principle growth model proposed by Tang, Alexander and Bruinsma (TAB). Simple microscopic explanations are given to account for the finding of Edwards-Wilkinson (EW) type growth at low Ar pressure and the TAB growth mechanism at high pressures, as well as for the absence of any scaling according to the Kardar-Parisi-Zhang (KPZ) equation.

A condensed review of theory, application, fabrication, and characterization of multilayers in neutron optics is given. The main results of kinematical theory for periodic multilayers are quoted. The application of multilayers as monochromators, band pass filters and supermirrors is discussed.

We have improved a neutron spin echo spectrometer at the C2-2 port of JRR-3M, JAERI. The new double reflection supermirror monochromators with the wavelength λ =5.9 A (Δ λ / λ =15%) and λ =7.14 A (Δ λ / λ =18%) increased the polarized neutron flux at the sample position about three times more than the old monochromator. The deflection angle 2 θ M at C2-2 port increased up to 7.00° using double reflection, which reduced the disturbance from the iron cover of C2 guide for C2-3 port. In order to gain more neutron intensity, we replaced the spiral coils with a wider one and installed a new detector system with an assembly of eight one-dimensional PSDs.

Current multilayer designs for 10-80 keV hard X-ray telescope missions have focused primarily on the proven properties of W and Pt based multilayer coatings. Recently a number of new material combinations and coating capabilities have emerged which allows for more elaborate designs that can further extend the energy band of current mission designs as well as avoid some of the unwanted absorption edge effects in the effective area near potentially important line emission energies. These new design possibilities are investigated for current hard X-ray mission designs. The new material combinations to be considered are recently proven capabilities of enhanced NiV/C coatings and NiV/SiC coatings in conjuction with the well-established W based coatings.

Graded depth multi-layer coatings have the potential to optimise the performance of X-ray reflective surfaces for improved energy response. A study of deposition techniques on silicon substrates representative of the XEUS High Performance Pore Optics (HPO) technology has been carried out. Measurements at synchrotron radiation facilities have been used to confirm the excellent performance improvements achievable with Mo/Si and W/Si multilayers. Future activities that will be necessary to implement such coatings in the HPO assembly sequence are highlighted. Further coating developments that may allow an optimisation of the XEUS effective area in light of potential changes to science requirements and telescope configurations are also identified. Finally an initial measurement of effects of radiation damage within the multilayers is reported.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

We have experimentally demonstrated that planar neutron waveguides can be used as resonant beam couplers to efficiently produce a coherent neutron line source with cross sections in the submicrometer range. The Fraunhofer far-field diffraction pattern of the first three resonance modes was measured and found to be in excellent agreement with the theoretical model. Our measurements confirm that an excited exiting mode is fully coherent in the direction perpendicular to the surface of the thin-film coupler and may therefore be used for applications of interest to a broad user community in biochemical and semiconductor nanosciences such as static and time-resolved coherent speckle experiments or phase-contrast imaging.

We have studied interfacial roughness in amorphous W/Si multilayers grown by rf sputtering at different deposition parameters by cross-sectional transmission electron microscopy, x-ray reflectivity, and diffuse x-ray scattering. The diffuse scattering intensity has been recorded in an unprecedented wide range of parallel momentum transfer, 5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$\ensuremath{\leqslant}${\mathit{q}}_{\mathrm{\ensuremath{\parallel}}}$\ensuremath{\leqslant}1 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$, giving access to the height-height self- and cross-correlation functions on lateral length scales between a few \AA{} and 1 \ensuremath{\mu}m. The results are compared for the different samples and discussed in view of the deposition parameters. \textcopyright{} 1996 The American Physical Society.

Multilayer mirrors with enhanced bandwidth were developed with special performances for dense plasma diagnostics and mainly for high spatial resolution x-ray imaging. The multilayer coatings are designed to provide broadband x-ray reflectance at low grazing incidence angles. They are deposited onto toroidal mirror substrates. Our research is directed at the development of non-periodic (depth graded) W∕Si multilayer specifically designed for use in the 1 to 30 keV photon energy band. First, we present a study for a 5 to 22 keV x-ray spectral window at 0.45° grazing angle. The goal is to obtain a high and constant reflectivity. Second, we have modeled a broadband mirror coating for harder x-rays in the range from 10 to 30 keV, with a non-periodic structure containing 300 W∕SiC layers with periods in the range from 0.8 to 4 nm, designed for 0.35° grazing incidence angle.

At the previous OSA meeting on X-ray multilayers P. Dhez described using a white-beam, fixed-angle, solid-state detector experiment (the so called energy-dispersive setup) for easy characterization of multilayer structures. The simplicity of the setup makes it ideal for in-situ analysis and hard x-ray reflectivity measurements. The multilayer d-spacings can be readily obtained using only the spectrum of the reflected beam, and the absolute reflectivities can be obtained using both the white-beam spectrum and the reflected spectrum. The simplicity of the setup makes it ideal for in-situ analysis and hard x-ray reflectivity measurements. The multilayer d-spacings can be readily obtained using only the spectrum of the reflected beam, and the absolute reflectivities can be obtained using both the white-beam spectrum and the reflected spectrum. Figure 1 shows an example of a observed white-beam spectrum consisting of Bremsstralung and superimposed W-fluorescence lines. Figure 2 shows an example of the observed spectrum after reflection with a multilayered supermirror structure (described elsewhere in these proceedings).

With the increased availability of hard X-ray (≥ 20 keV) synchrotron sources and a concurrent wish for hard X-ray telescopes. the need for hard X-ray optics has become considerable. For some applications crystals and periodic multilayers are desirable; for others the bandwidth of these may be too narrow. A wider bandwidth can be obtained by using total reflection from heavy elements. This approach. however, is impractical for harder X-rays since it is limited by the inverse proportionality between the critical angle of total reflection and the energy. One solution to this broad-band reflection problem may be the supermirror: a multilayer structure where the bi-layer thickness is gradually changed from top to bottom. In such a structure radiation with different wavelengths will have the criteria for constructive interference fulfilled at different depths in the multilayer. If the bi-layer thicknesses are changed sufficiently slowly. simultaneous diffraction of a continuum of X-ray energies can be obtained. The multilayered supermirror was originally designed for neutron applications1 such as increasing the throughput of guide-tubes. For neutrons, where absorption is extremely low for most materials. reflectivities up to95 can be obtained in a continuous band up to 3 times the critical angle or energy2. For X-rays. the absorption is considerably larger and this strongly influences the performance of the X-ray supermirror.

Multilayer-based x-ray optical components call for heterostructures made of smooth and uniform layers with an abrupt interface, which imposes severe restrictions to the choice of materials. The multilayers have to be very uniform (1%) over the area that will be illuminated by an X-ray beam. For hard x-rays the small angle of incidence implies multilayers that are several tens of centimeter long, even when using a small d-spacing. When the beam is produced by a synchrotron storage ring source the high heat flux connected with the intense x-ray beams requires materials that are chemically very stable.

We have generalized the principle of resonant X-ray beam coupling to waveguides containing multiple guiding layers and characterized their X-ray optical properties. In such a device, several coherent beams of a width on the order of 10-100 nm can be extracted at the end of the waveguide. By measuring the farfield pattern formed by the interference of the beams, we demonstrate the possibility of using these devices as new tools to tailor the field distribution in the near- and far-field region for specific applications. Besides coherent diffraction and imaging, interferometry with two or more nanometer sized beams can be envisioned