This PDF file contains the Front Matter associated with SPIE Proceedings Volume 7802, including the Title page, Copyright information, Table of Contents, Conference Committee listing, and introduction.

To realize achromatic full-field hard X-ray microscopy with a resolution better than 100 nm, we studied an imaging system consisting of an elliptical mirror and a hyperbolic mirror. The figure accuracies of the elliptical and hyperbolic mirrors required to obtain diffraction-limited resolution were investigated using a wave-optical simulator, and then elliptical and hyperbolic mirrors were precisely fabricated, following the criterion of the figure accuracies. Experiments to form a demagnified image of a one-dimensional slit installed 45 m upstream were conducted using the imaging system at an X-ray energy of 11.5 keV at BL29XUL of SPring-8. The system could form a demagnified image with the best resolution of 78 nm. In addition, the field of view to obtain a resolution better than 200 nm was 4.2 micron.

Reactive ion etching (RIE) has been employed in a wide range of fields such as semiconductor fabrication, MEMS (microelectromechanical systems), and refractive x-ray optics with a large investment put towards the development of deep RIE. Due to the intrinsic differing chemistries related to reactivity, ion bombardment, and passivation of materials, the development of recipes for new materials or material systems can require intense effort and resources. For silicon in particular, methods have been developed to provide reliable anisotropic profiles with good dimensional control and high aspect ratios^1,2,3, high etch rates, and excellent material to mask etch selectivity. A multilayer Laue lens⁴ is an x-ray focusing optic, which is produced by depositing many layers of two materials with differing electron density in a particular stacking sequence where the each layer in the stack satisfies the Fresnel zone plate law. When this stack is sectioned to allow side-illumination with radiation, the diffracted exiting radiation will constructively interfere at the focal point. Since the first MLLs were developed at Argonne in the USA in 2006⁴, there have been published reports of MLL development efforts in Japan⁵, and, very recently, also in Germany⁶. The traditional technique for sectioning multilayer Laue lens (MLL) involves mechanical sectioning and polishing⁷, which is labor intensive and can induce delamination or structure damage and thereby reduce yield. If a non-mechanical technique can be used to section MLL, it may be possible to greatly shorten the fabrication cycle, create more usable optics from the same amount of deposition substrate, and perhaps develop more advanced structures to provide greater stability or flexibility. Plasma etching of high aspect-ratio multilayer structures will also expand the scope for other types of optics fabrication (such as gratings, zone plates, and so-on). However, well-performing reactive ion etching recipes have been developed for only a small number of materials, and even less recipes exist for concurrent etching of more than one element so a fully material specific process needs to be developed. In this paper, sectioning of WSi₂/Si multilayers for MLL fabrication using fluorinated gases is investigated. The main goals were to demonstrate the feasibility of this technique, achievement of high anisotropy, adequate sidewall roughness control and high etching rates. We note that this development for MLL sidewalls should be distinguished from work on improving aspect ratios in traditional Fresnel zone plates. Aspect ratios for MLL sidewalls are not similarly constrained.

Future large X-ray telescopes will be based on segmented designs and will require different techniques for error analysis and budgeting from those used for full shell optics. In this paper we develop a grazing incidence optical model using commercial software Zemax for figure error compensation. In particular we show how the image of a pair of mirror segments with average radius and/or average cone angle errors can be optimized with rigid body motions such as pitch, radial despace and axial despace. We show detailed tolerance analysis of the optical model and present results on how to compensate for these errors up to limitations determined by mechanical constraints of the telescope module.

The development of Fourier Transform (FT) spectral techniques in the soft X-ray spectral region has been advocated in the past as a possible route to constructing a bench-top size spectral imager with high spatial and spectral resolution. The crux of the imager is a soft X-ray interferometer. Auxiliary subsystems include a wide-band soft X-ray source, focusing optics and detection systems. When tuned over a sufficiently large range of path delays, the interferometer will sinusoidally modulate the source spectrum centered at the core wavelength of interest, the spectrum illuminates a target, the reflected signal is imaged onto a CCD, and data acquired for different frames is converted to spectra in software by using FT methods similar to those used in IR spectrometry producing spectral image per each pixel. The use of shorter wavelengths results in dramatic increase in imaging resolution, the modulation across the beam width results in highly efficient use of the beam spectral content, facilitating construction of a bench-top instrument. With the predicted <0.1eV spectral and <100 nm spatial resolution, the imager would be able to map core-level shift spectra for elements such as Carbon, which can be used as a chemical compound fingerprint and imaging intracellular structures. We report on our progress in the development of a Fourier Transform X-ray (FTXR) interferometer. The enabling technology is X-ray beam splitting mirrors. The mirrors are not available commercially; multi layers of quarter-wave films (used in IR and visible) are not suitable, and several efforts by other researchers who used parallel slits met only a very limited success. In contrast, our beam splitters use thin (about 200 nm) SiN membranes perforated with a large number of very small holes prepared in our micro-fabrication laboratory at JPL. Precise control of surface roughness and high planarity are needed to achieve the requisite wave coherency. The beam splitters prepared-to-date had surface RMS and planarity better that <0.3 nm over a 0.45 mm x 1.4 mm area, meeting requirements for spectral imaging at 100eV. Efforts to improve the mirror flatness to a level required for core-level shifts of Carbon are under way.

Multilayer coated blazed gratings with high groove density are the best candidates for use in high resolution EUV and soft x-ray spectroscopy. Theoretical analysis shows that such a grating can be potentially optimized for high dispersion and spectral resolution in a desired high diffraction order without significant loss of diffraction efficiency. In order to realize this potential, the grating fabrication process should provide a perfect triangular groove profile and an extremely smooth surface of the blazed facets. Here we report on recent progress achieved at the Advanced Light Source (ALS) in fabrication of high quality multilayer coated blazed gratings. The blazed gratings were fabricated using scanning beam interference lithography followed by wet anisotropic etching of silicon. A 200 nm period grating coated with a Mo/Si multilayer composed with 30 bi-layers demonstrated an absolute efficiency of 37.6% in the 3^rd diffraction order at 13.6 nm wavelength. The groove profile of the grating was thoroughly characterized with atomic force microscopy before and after the multilayer deposition. The obtained metrology data were used for simulation of the grating efficiency with the vector electromagnetic PCGrate-6.1 code. The simulations showed that smoothing of the grating profile during the multilayer deposition is the main reason for efficiency losses compared to the theoretical maximum. Investigation of the grating with cross-sectional transmission electron microscopy revealed a complex evolution of the groove profile in the course of the multilayer deposition. Impact of the shadowing and smoothing processes on growth of the multilayer on the surface of the sawtooth substrate is discussed.

High-order laser harmonics (HHs) produced by the interaction between a very intense ultrashort laser pulse and a gas jet represent an extreme-ultraviolet (XUV) radiation source with high brightness, coherence and peak intensity. The characterization of processes involving the use of HHs deserves a particular attention in the design of the beamline that is demanded to manage the XUV radiation. From the instrumental point of view, the photon throughput depends mainly from the efficiency of the optical elements. Here we present the experimental study of the optical properties of thin carbon films to be used as grazing-incidence coatings for XUV HHs. Several carbon samples were deposited on plane glass substrates by electron beam evaporation technique. The sample reflectivity was measured at different incidence angles in the 6.7-120 nm (190-10 eV) region. The optical constants (real and imaginary part of the refraction index) have been calculated. The results are in good agreement with what is reported in the literature and confirm that carboncoated optics operated at grazing incidence have a remarkable gain over conventional metallic coatings in the XUV. Since XUV HHs co-propagate with the intense infrared laser generating beam, it is important to measure the damage threshold of the coating when exposed to ultrashort infrared laser pulses. The experimental results obtained on carbon samples will be presented.

We present the design and characterization of the spectrometer to be used at the FLASH facility (DESY, Hamburg) to characterize the spectral properties of free-electron-laser radiation in terms of high harmonics content. The spectrometer is sensitive in the 2-40 nm region. The optical design consists of two spherical gratings with variable groove spacing and a extreme-ultraviolet-enhanced CCD detector. The instrument design and characterization are presented.

In this paper, a new type of spectral filter mirrors for extreme ultraviolet radiation based on DLC/Si multilayer coatings is presented (DLC - diamond-like carbon). The coating is nearly transparent for infrared radiation (IR) of λ = 10.6 nm but highly reflective at λ = 13.5 nm (EUV). We deposited DLC/Si multilayers by ion beam sputter deposition with 40 and 60 periods exhibiting maximum EUV reflectances of about R_max = 43 % and R_max = 50 %, respectively. Combining IR antireflective and EUV reflective coatings, first prototype mirrors have been fabricated with an EUV reflectance of about 42.5 % and an IR reflectance of about 4.4 % at the same time. Investigations on the thermal behavior of the multilayer stack and the cleaning properties for tin contaminated mirror surfaces have been carried out. Excellent stabilities of EUV peak position and reflectance values have been found using annealing temperatures of up to 700 °C. Furthermore, several cycles of Sn etching under H₂ reactive conditions have been applied to the mirrors without significant changes of the filter performance.

The mechanical stress induced during the growth of thin films and multilayers is a critical parameter for the fabrication of reflective x-ray optical elements. Strong stress can cause deformation of the optical surface, de-lamination of the respective coating, or even breaking of the underlying substrate. In order to characterize stress in a growing film or multilayer in a nearly in-situ mode, a dedicated monitor was installed on the ESRF multilayer deposition system. It is based on an autocollimator that measures the curvature change of a sample after subsequent coating steps while keeping it in the vacuum environment. Based on the theory of elasticity, the corresponding stress levels in the coating can be derived. Both the commissioning of the instrument and some initial results on single Ru and B₄C films and Ru/B₄C multilayers will be presented. A comparison with ex-situ investigations will complement this work.

To improve the stress property of multilayer optics working in extreme ultraviolet and x-ray range, mono-layer thin films of Mo, MoSi2, Si, with thickness of 100nm, and periodic multilayers of [Mo/Si]₂₀, [MoSi₂/Si]₂₀, with period thickness of 20nm, were prepared by direct current magnetron sputtering method. Before and after each deposition, the radius of surface curvatures of substrates were measured using a stylus profiler and then the film stress was calculated. The measurement results indicate that, Mo, MoSi₂ and Si mono-layer thin films all shows compressive stress, while Mo/Si multilayer shows tensile stress, i.e., the film stress changes significantly during Mo/Si multilayer growth. For MoSi₂/Si multilayer, the film stress still keeps compressive, which indicates more stable stress property.

The flux distributions in the focal plane of Kirkpatrick-Baez optics are investigated as the parameters of the focusing ellipse of the mirrors are changed from typical laboratory optics to synchrotron beam line optics. This work shows the effects of the most predominant focusing imperfections that arise from conditions that violate the original assumptions of Kirkpatrick-Baez systems, including orthogonality of the mirror surfaces and paraxial rays.

We report a successful fabrication and testing of the first set of Platinum (Pt)-coated Kirkpatrik-Baez (KB) mirrors for a submicrofocusing x-ray polychromatic beam from a conventional beamline (64 m long) at the 34-ID of Advanced Photon Source (APS). The set includes one 80 mm long mirror and one 40 mm short mirror fabricated by depositing Pt on finely polished spherical Silicon (Si) substrates using the APS-developed profile coating technique with the magnetron sputtering system. Profile coating masks were calculated through the coating profile data from metrology measurements acquired using interferometric stitching technique. Instead of flat substrates, spherical substrates (with shapes approximately mimicking the tangential profiles of the desired ellipses) were used, reducing the coating thickness and, thus, stress. The mirror pair was commissioned on the beamline and generated a 2-D spot with full width at half maximum (FWHM) 280 nm (V) x 150 nm (H). The detailed fabrication methods, metrology measurements, and calculations are discussed.

The focusing performance of shell optics for the hard X-ray region strongly depends on their axial mid-spatialfrequency- range figure errors. This paper presents the development of a deterministic computer-controlled polishing process to minimize these axial figure errors on cylindrical shaped mandrels from which the mirror shells are replicated. A mathematical model has been developed to simulate the residual surface figure errors due to the polishing process parameters and the polishing tools used, along with their non-conformance to the mandrel. We present design considerations of a large-size polishing lap where the experimentally determined process variables have been used for optimizing the lap configuration and the machine operational parameters. Furthermore, the developed model is capable of generating a corrective polishing sequence for a known surface error profile. Practical polishing experiments have been performed to verify the model and to determine its ability to correct known axial figure errors through polishing machine control.

Recent work in UCD has centred on the development of a liquid metal coating process for EUV and soft X-ray collector optics. The work involves using a room temperature liquid metal coated on a solid metal substrate of the appropriate form. The advances made demonstrate that a stable thin coating film on the interior surface of a rotating optic substrate is possible, and this offers promise as a solution to the problem of producing an atomically flat reflector that remains unspoiled in front of a multi-kilowatt EUV plasma. We report on the results of preliminary EUV tests carried out on a simple focusing liquid metal mirror.

We present a systematic study in which multilayers of different composition (W/Si, Mo/Si, Pd/B₄C), periodicity (from 2.5 to 5.5 nm), and numbers of layers have been characterised. Particularly, we investigated the intrinsic quality (roughness and reflectivity) as well as the performance (flatness and coherence of the outgoing beam) as a monochromator for synchrotron radiation hard X-ray micro-imaging. The results indicate that the material composition is the dominating factor for the performance. This is of high importance for synchrotron-based hard X-ray imaging which has become a widely applied tool for probing the microstructure of bulk samples. The high spatial resolution and different contrast modalities available here strongly depend on using coherent beams from highly brilliant sources. In order to satisfy the demand for a high flux of quasi-monochromatic photons, multilayer-coated mirrors are commonly used as monochromators. Their properties present a good tradeoff between spectral bandwidth and photon flux density. Since the photon flux density at the sample position is higher than with standard crystal monochromators, better spatial resolution can be reached. This comes at the cost of reduced energy resolution and stronger non-uniformities in the incoming beam profile. By helping scientists and engineers specify the design parameters of multilayer monochromators, our results can contribute to a better exploitation of the advantages of multilayer monochromators over crystal-based devices; i.e., larger spectral bandwidth and high photon flux density for X-ray imaging.

Beryllium windows are used on many X-ray synchrotron beamlines to separate and protect the ultra-high vacuum of the storage ring from the experimental environment. Currently, such a window is typically made of a thin, high-purity, beryllium foil, which may or may not have been polished. It is well known that these windows affect the transmitted beam quality. The impact ranges from non-perceptible to profound, depending on the experiment. The degradation of the X-ray beam is of increasing importance and concern, however, and in fact a number of beamlines now are run windowless or with a very small and thin silicon nitride window. There remain many instances where a large and robust window is desirable or necessary, and it is for this reason that developing windows that have little or no impact on the transmitted X-ray beam quality is important. This presentation reports on the progress in developing single-crystal beryllium X-ray windows. Due to its high purity and homogeneity, relative structural perfection, and high polishiblity single-crystal beryllium is an attractive window material candidate, particularly for beamlines conducting imaging or coherence-based experiments. Development of thin and uniform windows with less than 1 nm rms surface roughness and their preliminary characterization results are presented.

A method is proposed to analyze the mutual coherence function of a general x-ray beam. The mutual coherence function is shown to be the Fourier pair of the wavevector distribution of the beam inside a finite volume. A rocking-curve profile to be measured with a perfect-crystal plate is calculated as a kind of one-dimensional projection of the wavevector distribution of the incident beam. Collecting rocking-curve profiles measured with several reciprocal lattice vectors, we can construct the wavevector distribution with a computed-tomography technique, and then calculate the mutual coherence function. The mutual coherence function of a synchrotron x-ray beam was analyzed with a high spatial resolution and a wide dynamic range.

Simulation of optical systems is an important tool for optics design for known applications, and in assessing the potential for new applications. Monte Carlo simulations were developed to model complex reflective x-ray optical systems, including polycapillary lenses and micropore optics. The simulations are fully three-dimensional, tracking both the photon trajectories and optic surface normals as vectors. Simulation verification was performed for a wide variety of optics geometries, x-ray source configurations and photon energies and included comparison with both theoretical modeling and experimental data. Glass defects such as surface roughness and ripple as well as defects in optics geometry such as rotation of micropore walls and profile error in polycapillary optics were incorporated and were shown to have differing effects, including reducing throughput or increasing focal spot size, depending on the source and optic geometry and photon energy.

EXtreme ultraviolet spectrosCope for ExosphEric Dynamics (EXCEED) will carry out the extreme ultraviolet (EUV) spectroscopic imaging observations from earth orbit. It clarifies the plasma distributions and compositions around the various planets and examines the interactions with the solar wind. Observations should be carried out at high altitude so that the earth's atmospheric absorption is free. Our spectral range is from 60 to 145 nm and the spectral resolution is 0.2 to 0.5 nm (FWHM). The mission is planned to be launched in 2013, beginning of the next period of solar maximum. In this paper, we will introduce the general mission overview, scientific objectives and development of instrument.

We have reported a discharge-produced plasma extreme ultraviolet source based on a pure potassium vapor. Potassium ions produced strong broadband emission around 40 nm with a bandwidth of 8 nm [full width at halfmaximum (FWHM)]. The current-voltage characteristics of discharge suggest that the source operates in a hollow cathode mode. By comparison with atomic structure calculations, the broadband emission is found to be primarily due to 3d-3p transitions in potassium ions ranging from K ²⁺ to K⁴⁺.

The soft x-ray micro-characterization beamline (SXRMB) has recently undergone commissioning at the Canadian Light Source. SXRMB is a synchrotron bending magnet based design that covers a photon energy range of 1.7-10 keV, using a double-crystal monochromator that employs two crystal pairs - InSb-111 and Si-111. The indium antimonide crystals are typically used over the photon energy sub-range of 1.7-4 keV, to cover the K-edges of many important elements, including Si, P, S, Cl, and Ca. The performance of the InSb-111 crystal pair has proven problematic, requiring several iterations to improve the photon flux performance to an acceptable level. Thermal distortions for indium antimonide are considerable even at power levels below 50 W, since it suffers from poor thermal conductivity and a large linear thermal expansion coefficient. Finite element analysis results for different crystal thicknesses will be presented. Improvements to the crystal cage holders and cooling, as well as metrological improvements to properly mount the crystals will also be discussed.

The effect of ultrasound artificial anisotropy of crystals in X-ray frequency range was observed and an effort to theoretically interpret this effect in Bragg-Laue diffraction case was made. It was established that an isotropic crystal optically turns into an artificially anisotropic one with optical axis along the direction of applied external influence as a symmetry axis, giving rise to the double refraction. Investigations of this kind are important because the results can be applied such as the artificial anisotropy effects in optics (in analogy Kerr effect in optics).