This PDF file contains the front matter associated with SPIE Proceedings Volume 8848, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

We present experiments carried out using a combined hard x-ray focusing set-up preserving the benefits of a large-aperture Kirckpatrick-Baez (KB) mirror system and a small focal length multilayer zone plane (MZP). The high gain KB mirrors produce a pre-focus of 400 nm × 200 nm; in their defocus, two MZP lenses of diameter of 1.6 μm and 3.7 μm have been placed, with focal lengths of 50 μm and 250 μm respectively. The lenses have been produced using pulsed laser deposition (PLD) and focused ion beam (FIB). Forward simulations including error models based on measured deviations, auto-correlation analysis and three-plane phase reconstruction support two-dimensional focus sizes of 4.3 nm × 4.7 nm (7:9 keV, W/Si)¹ and 4.3 nm ×5.9 nm (13:8 keV, W/ZrO₂), respectively.

We have developed a new method to fabricate ultrathin silicon single crystals, which can be used as spectral beam splitters for the hard x-ray regime, based on a reactive dry etching process using plasma at atmospheric pressure. The high crystalline perfection of the crystals was verified by both topographic and high-resolution rocking curve measurements using coherent x-rays at the 1-km-long beamline, BL29XUL of SPring-8. The development of thin crystals enables the construction of a split-delay unit and the provision of a dedicated branch for photon diagnostics. By using a 20-μm-thick Si(111) crystal in the symmetric Bragg geometry as a component of a Si(111) double-crystal monochromator, an arrival-time monitor using a destructive manner has been upgraded to a non-destructive method at SPring-8 Angstrom Compact free-electron LAser. Using the splitting crystals in a helium atmosphere can prevent oxidation, which can introduce a lattice distortion.

A novel design of X-ray optical system - concentrator for astrophysical rocket experiment is investigated. The proposed system is based on four modules with Kirkpatrick-Baez (KB) configuration allowing usage of multi-foil mirrors arranged to parabolic profile. The KB modules are supplemented by rotationally symmetrical parabolic segments. This X-ray optical system effectively uses a circular aperture. The KB modules are placed in four quadrants while the segments are set into a Cartesian cross between the KB modules. Studied optical system is under consideration for the student rocket experiment of University of Colorado that should verify function of NIST’s energy-dispersive detector based on Transition Edge Sensors (TES microcalorimeters).

The refractive index for matter in the hard X-ray range changes rather rapidly with increasing photon energy. In fact away from absorption edges the refractive index decrement varies with the square of the photon energy. As the photon energy dispersion depends on the refractive index decrement, prisms, as used in the visible spectral range, can also be used in the X-ray range for monochromatising or dispersing an incident polychromatic X-ray beam. The dispersion in a single prism is rather small and it is thus mandatory to use ensembles of many prisms for the dispersion process. A particular prism assembly is the Clessidra X-ray lens. The name of the lens, which is Italian for hourglass, describes its appearance as many tiny prisms form two larger prisms with opposing areas. In this form the device can focus an incident plane X-ray wave by refraction. Then the dispersion will make the focusing suffer from chromatic aberrations. The latter can be used in order to operate the structure as a monochromator in combination with an exit slit. For this operation it was found to be advantageous to use a central obstruction in the lens. As the prism array focuses only onedimensionally the object rotation around an axis, which is perpendicular to the incident X-ray beam and which lies in the dispersion plane, is now an available degree of freedom. In a monochromator one can make good use of it, as it permits us to tune the photon energy in a fixed slit. This contribution will discuss the limits for such an operation in terms of achievable spectral resolution and in terms of rapid tuning.

Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses are well suited to generate hard x-ray beams with lateral dimensions of 100 nm and below. The diffraction limited beam size of refractive x-ray lenses mainly depends on the focal length and the attenuation inside the lens material. The numerical aperture of refractive lenses scales with the inverse square root of the focal length until it reaches the critical angle of total reflection. We have used nanofocusing refractive x-ray lenses made of silicon to focus hard x-rays at 8 and 20 keV to (sub-)100 nm dimensions. Using ptychographic scanning coherent diffraction imaging we have characterized these nanobeams with high accuracy and sensitivity, measuring the full complex wave field in the focus. This gives access to the full caustic and aberrations of the x-ray optics.

The study of transient high pressure fuel sprays by X-ray based techniques is worldwide diffused. Synchrotron radiation is successfully exploited for this aim because of its high intensity and pulsed nature. However top-table application are unusual. This work reports the structure of a gasoline spray from an automotive GDI injection system obtained by X-ray Tomography desktop experiments using an 8 keV Cu Kα X-ray. Polycapillary semilens shaped the divergent X-ray beam into quasi-parallel one allowing to focus the radiation on the investigated spray region. High contrast focus images were collected by a CCD detector for X-radiation. A 6-hole GDI injector has been coupled to the high pressure pump by a specially designed rotating device able to work up to 25MPa. X-ray absorption measurements have been performed with angular steps Δθ = 1° at the injection pressure of 12.0 MPa. The sinogram reconstruction of the jets by slices permitted to get information about the inner structure of the fuel spray downstream the nozzle tip, where conventional optical techniques are inhibited. A 3D spatial distribution of the fuel emerging from the injector has been obtained. The data have been used to perform spray density measurements. The results concerning the absorption profile along the fuel jets axis and the cross section distribution at different distances from the nozzle have been reported.

Sagittal focusing is a widely used geometry to horizontally focus X-rays in synchrotron beamlines. Usually, two types of devices are used: toroidal mirrors combined with flat X-ray monochromators or flat mirrors combined with sagittal focusing monochromators. The former option seems to be better since the stresses caused by the bending of the second crystal in a double crystal monochromator (DCM) are avoided. In this work we explore the effect of sagittal focusing in medium to high energy resolution X-ray monochromators. Our studies are based on a theoretical explanation of experimental data acquired in two different experiments performed at the XRD2 beamline at Laboratorio Nacional de Luz Sincrotron (LNLS / Brazilian Synchrotron) and X18A at the National Synchrotron Light Source (NSLS / BNL / USA). The first experiment was carried out with a flat meridional bendable mirror followed by a DCM with the second crystal being sagitally bent. The second experiment was carried out with a flat Si 111 DCM followed by a toroidal, but meridional bendable mirror. Both setups are completed by a Si 551 4-bounce monochromator to scan the energy spectrum around 13.7 keV and 13.9 keV, respectively. The results show that the sagittal curvature induces an energy structure. Theoretical studies made by analyzing the reflecting angles in the mirror surface joined with the dynamical theory of X-ray diffraction in the 4-bounce X-ray monochromators confirm these results, which are also explored by the DuMond diagram.

Saw-tooth refractive lenses (SRL) provide a comparatively attractive option for X-ray focusing for various reasons, including their simple, continuous tunability in energy and focal length. Optimal focusing of a conventional SRL at short focal lengths is limited by the SRL’s length in relation to the focal length. Three approaches to overcome this limitation are described. Analytical solutions verified with ray-tracing are presented. These are bending, variation of the saw-tooth tip angles, and variation of the period.

Kirkpatrick-Baez (K-B) active X-ray optics system is a good choice for focusing the free electron laser (FEL) pulses delivered by FERMI, the first seeded EUV-SXR FEL user facility operated at Elettra Sincrotrone Trieste. The present work reports the results obtained tuning this optical system used at the Diffraction and Projection Imaging (DiProI) beamline in order to improve and optimize its performance in terms of quality and size of the focal spot onto the sample controlling the fluence as well. To characterize the performance and develop reliable and reproducible focusing procedures we performed a campaign of measurements with several diagnostic systems, including a wavefront sensor mounted after the DiProI chamber. Online wavefront measurements have allowed for optimizing the bending acting on the mirrors curvature and the angle positions (pitch and roll) of the K-B system. The experimental results are compared with the predictions from simulations obtained using the WISE code, starting from mirror actual surface metrology characterization. Filtering the Fourier transform of the mirror surface profiles we have analyzed the impact of spatial wavelengths on the focal spot degradation. From the wavefront measurements we have inferred a focal spot of 10 μm x 10 μm confirmed by the PMMA ablation imprints. The results from simulations with the WISE code are in agreement with the measurements and for different energies of the incident beam we established the threshold when the focal spot degradation is not affected by the spatial wavelengths of the K-B mirror surfaces.

Ellipsoidal mirrors are one of the most promising types of X-ray mirror, because the mirror can focus X-rays to nanometer size with a large aperture and no chromatic aberration. However, so far ideal ellipsoidal mirrors cannot be realized by any manufacturing methods. One of the reasons is there is no fabrication method to process their inside surface with a diameter of several millimeters with nanometer-level accuracy. We propose and develop a manufacturing process of the ellipsoidal mirror. First, a master which has the reversed shape is prepared using grinding, polishing and Elastic Emission Machining (EEM). EEM can finish the surface shape to within 2nm (RMS). Then, the ellipsoidal mirror is produced by replicating the surface using an electroforming deposition method. By conducting the process without any stress at room temperature, replicating the surface roughness and shape with nanometer order accuracy is possible. In this paper, we report the current status of manufacturing of the ellipsoidal mirror.

MAESTRO, the Microscopic and Electronic STRucture Observatory, currently under construction at the Advanced Light Source (ALS), will be a world premier facility for the study of electronic and structural properties of in situ grown crystals. The new facility will be comprised of several end-stations, including angle-resolved photoemission spectroscopy, μARPES and nARPES end-stations, and a photoemission electron microscope combined with a lowenergy electron microscope (PEEM/LEEM). Redirection of the x-ray beam between the μARPES and PEEM/LEEM end-stations, which are longitudinally separated by 2.5 meters, uses a system of two bendable mirrors, placed in Kirkpatrick-Baez configuration designed for two foci. Here we present the details of the mirrors’ design and report on the characterization of the mirrors carried out at the ALS X-ray optical laboratory (XROL). Optimal tuning and calibration of the mirrors was performed using a technique recently developed at the OML [Opt. Eng. 48(8), 083601 (2009)]. The technique is based on regression analysis of surface slope data obtained with a long trace profiler (LTP). We provide results of tests of temporal and temperature stabilities of the shape of the mirrors. High reliability of the optical metrology with the mirrors has become possible due to a modification of the tuning procedure described in the present article. The modification allows accounting for the gravity sag effect, as well as the LTP systematic error in measurements with significantly curved x-ray optics.

The ellipsoidal mirror is one of the most effective achromatic focusing optic with large aperture and nanofocusing ability. Because of the large aperture of mm-order size, this optic is suitable for a laboratory-based light source that has a large divergence angle. Recently, soft X-rays produced by high-order harmonics have become available. Such a beam has high spatial coherency but relatively large divergence angle. This light in combination with an ellipsoidal mirror will generate a highly intense focusing nanobeam that will contribute to various experiments and analyses such as those of photoelectron spectroscopy and nonlinear optical phenomena. In this paper, we present the optical design for a lab-based soft X-ray beamline and the results of optical simulation considering the parameters of the source. Finally, we introduce a two-stage focusing system with an axisymmetric mirror as a promising soft X-ray focusing system.

A bent cylindrical mirror and short (150 and 200 mm) elliptically polished Kirkpatrick-Baez (KB) mirrors are used to efficiently focus the entire beam from an insertion device for flux-limited experiments at energies up to 22 keV. Spots of ~50 x 70 μm² (cylinder only) or ~16 microns diameter (KB and cylinder) may be selected, without changing the sample position. The cylinder has nearly 100% throughput, while the KB has losses of about 50% due to system constraints. Design considerations and performance will be discussed.

SCOTS is a high precision slope measurement technology based on deflectometry. Light pattern on a LCD display illuminates the test surface and its reflected image is used to calculate the surface slope. SCOTS provides a high dynamic range full field measurement of the optics without null optics required. We report SCOTS tests on X-ray mirrors to nm and even sub nm level with precise calibration of the test system. A LCD screen with dots/check board pattern was aligned into the system at the test mirror position to calibrate camera imaging distortion in-situ. System errors were further eliminated by testing and subtracting a reference flat which was also aligned at the same position as the test mirror. A virtual reference based on the ideal shape of the test surface was calculated and subtracted from the test raw data. This makes the test a ‘virtual null’ test. Two X-ray mirrors were tested with SCOTS. 0.1μrad (rms) slope precision and sub nm (rms) surface accuracy were achieved.

Numerical simulations of the performance of new x-ray beamlines and those under upgrade require sophisticated and reliable information about the expected surface slope and height distributions of prospective beamline optics before they are fabricated. Ideally, such information is based on metrology data obtained with existing optics, which are fabricated by the same vendor and technology, but generally, have different sizes, and slope and height rms variations. In a recent work [Opt. Eng. 51(4), 046501, 2012], it has been demonstrated that autoregressive moving average (ARMA) modeling of one-dimensional (1D) slope measurements with x-ray mirrors allows a high degree of confidence when fitting the metrology data with a limited number of parameters. With the parameters of the ARMA model, the surface slope profile of an optic with the desired specification can reliably be forecast. Here, we investigate the time-invariant linear filter (TILF) approach to optimally parameterize surface metrology of high quality x-ray optics thought of as a result of a stationary uniform random process. We show that the TILF approximation has all advantages of one-sided AR and ARMA modeling, but it additionally gains in terms of better fitting accuracy and absence of the causality limitation. Moreover, the suggested TILF approach can be directly generalized to 2D random fields. This work is supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

We discuss an application of correlation analysis to surface metrology of high quality x-ray optics with the aim of elicitation and, when possible, suppression of the instrumental systematic errors in the final metrology results. We describe and present the mathematical foundation for a novel method consisting of the randomization of the systematic error by the averaging of multiple measurements, specially arranged to mutually anti-correlate. We also discuss the possibility to apply correlation analysis to the entire residual surface slope distribution in order to find anti-correlation parameters of the distribution. In this case, repeated measurements with the corresponding change of the experimental arrangement (position of the surface and/or its overall tilt) can be used to identify the origin of the observed anticorrelation features by analyzing the difference between the measurements. If the corresponding minimum of the autocorrelation function is due to a systematic error, averaging over the repeated measurements will provide an efficient suppression of the systematic error. If the observed anti-correlation properties are due to the polishing process, and therefore belong to the surface itself, we suggest that the possibility of re-polishing the surface based on the correlation analysis be considered. Throughout the present work we have discussed correlation analysis of surface slope metrology data. However, a similar consideration can be applied to surface topography in the height domain measured with other metrology instrumentation, for example: interferometers and interferometric microscopes.

The use of linear methods to obtain both the error surface and the instrument error from redundant-independent datasets has been proposed to improve the accuracy of angle measuring scanning devices such as the long trace profilometer (LTP) or the nanometer optical measuring machine (NOM). In this work we propose to extend the method to measurements obtained during the calibration of mechanical benders. The proposed method allows determining an error-free measure of the slope error, the curvature and the cubic component of the mirror, as well as the instrument error. The description of the method, simulations and practical works are presented.

The multi-beam long trace profiler (MB-LTP) is under development at NASA’s Marshall Space Flight Center. The traditional LTPs scans the surface under the test by a single laser beam directly measuring the surface figure slope errors. While capable of exceptional surface slope accuracy, the LTP single beam scanning has slow measuring speed. Metrology efficiency can be increased by replacing the single laser beam with multiple beams that can scan a section of the test surface at a single instance. The increase in speed with such a system would be almost proportional to the number of laser beams. The progress for a multi-beam long trace profiler development is presented.

Plasma based radiation sources optimized to emit 13.5 nm Extreme UV radiation also produce a significant amount of light at longer wavelengths. This so called out-of-band (OoB) radiation is detrimental for the imaging capabilities of an EUV lithographic imaging system, particularly the deep ultraviolet (DUV) and ultraviolet (UV) parts of the light (λ=100-400 nm). To suppress these wavelengths while maintaining the high efficiency of the mirror for EUV light, several methods have been developed, including phase-shift gratings (PsG) and anti-reflection layers (SPE layer). PsG’s use the diffraction properties of a quarter-wavelength high multilayer grating to filter out the DUV/UV light, while the SPE layer works as an anti-reflection coating. Both methods have achieved a suppression factor of 10 - 30 around the target wavelength. To achieve a full band suppression effect, a new scheme based on surface pyramid structures was developed. An average suppression ofmore than 10 times can be achieved with a relative EUV efficiency of 89% (compared to standard multilayer (ML)) in theory. Different methods were discussed and their results are presented.

In this article we present an overview of the optimization of LaN/B multilayers that enabled the deposition of a multilayer with a normal incidence reflectance of 57.3 % at 6.6 nm wavelength, the highest value reported to date. Two different ways of nitridation of the La layers were investigated: firstly N-ion post treatment of the La layer and secondly reactive magnetron sputtering of La in N₂ atmosphere. Initially the optimization of the multilayers was performed for 50 period test multilayers, followed by the selection of the best process to study the stability of the full stack deposition and the optical performance of the mirrors. The scaling of reflectivity with increasing number of periods for LaN/B multilayer mirrors will also be discussed.

Fabrication of diffraction grating for x-rays is a very challenging problem due to the exacting requirements of surface quality, groove position, and groove profile. Traditional fabrication techniques have significant limitations and do not cover all the necessary requirements. For example, classical holographic recording is limited in the type of groove patterns that can be produced. This is particularly important in the design of wide aperture high resolution spectrometers, where aberration correction using complex groove patterns is necessary. We are pioneering the use of direct-write mask-less optical lithography to make grating patterns of arbitrary complexity. In this work we report on the first results from our direct-write mask-less approach, including quality assessment of the patterns using interferometric techniques.

We evaluated the irradiation damage induced to platinum/carbon multilayers induced by hard X-ray free-electron lasers (XFELs). In this study, in order to test the use of the platinum/carbon multilayers for future XFEL focusing applications, we evaluated the structures in almost exactly the condition in which they would actually be used. The X-ray reflectivity of the multilayers was measured by using XFELs, and a cross-section of the multilayer that was irradiated by an XFEL was observed by transmission electron microscopy. We used a non-monochromatic beam at a photon energy of 10 keV. We confirmed that the intensity of the conditions under which the multilayers are to be used is sufficiently lower than the breakdown threshold of platinum/carbon multilayers.

X-ray free electron lasers (XFELs) with intense and ultra-short pulse X-rays possibly induce damage to optical elements. We investigated the damage thresholds of optical materials by using focusing XFEL beams with sufficient power density for studying ablation phenomena. 1-μm focusing beams with 10 keV photon energy were produced at the XFEL facility SACLA (SPring-8 Angstrom Compact free electron LAser). The focusing beams irradiated samples of rhodium-coated substrate, which is used in X-ray mirror optics, under grazing incident condition.

Beam inhomogeneities of asymmetric Ge(220)-based V-shaped and single bounce monochromators have been studied both in metrological and imaging applications for photon energies around 8 keV. Presence of growth striations in graded GeSi, grains in single Cu crystal, and strains in thermally tuned V-channel monochromators observed in X-ray topographs excludes these materials from imaging applications. As for stochastic surface processing, chemomechanical polishing (CMP) produces better surface homogeneity than chemical polish. However, CMP is more difficult to be applied in V-channels, where chemical polishing is prefered. For comparison, measurements on surfaces processed by a deterministic mechanical method of single point diamond turning (SPDT) have shown SPDT to be a perspective technology. Again, to prepare deep grooves with this technique is also a challenge, mainly for tool makers. Some process induced features are observed as wavefield distortions in interference fringes.

X-ray tube spectra are obtained using Oroglas materials as scatterers. The measured spectra are corrected for detector efficiency and Compton effect. The relative intensities of the elements in alloys are measured and calculated. The consistency of the experimental results and the theoretical values confirmed the validity of the corrected spectra, indicating that the method introduced in this letter is a simple and valid way of obtaining the X-ray tube spectra for quantitative analysis of X-ray fluorescence analysis.

Stacking technique of the Fresnel zone plate fabrication with effective multilevel zone structure was considered by means of numerical simulation. It was shown that such approach allows increasing focusing efficiency without essential additional fabrication difficulties since the proposed device is a simple combination of bi-level structures. The conditions, at which layers are acting as a single zone plate, as well as criteria of layer alignment aren’t significantly changed compared with those of bi-level case. The angular sensitivity estimation shows that it allows imaging of objects larger than zone plate diameter.

The Alba ray tracing code (ART) is a suite of Matlab functions and tools for the ray tracing simulation of x-ray beamlines. The code is structured in different layers, which allow its usage as part of optimization routines as well as an easy control from a graphical user interface. Additional tools for slope error handling and for grating efficiency calculations are also included. Generic characteristics of ART include the accumulation of rays to improve statistics without memory limitations, and still providing normalized values of flux and resolution in physically meaningful units.

Many synchrotron experimental techniques require a variable size x-ray photon beam on the sample or on the detector. The easiest way to achieve this, with the minimum set of optical elements, is to defocus the beam, typically by changing the bending radius of the focusing mirrors. Nevertheless, to defocus the beam from sample has the problem that the beam profile is heavily modulated by striations caused by the surface error of the focusing optics. To our knowledge, a relationship between these modulations of the beam and the surface errors that originates them has not been properly established. In this work we show that beam modulation of a defocused beam has a nonlinear dependence on the slope profile of the mirror. From the derived relationships it follows that the relative contributions to beam striations of slope error lower and higher spatial frequencies vary depending on how far away the measurement plane is from the image plane. We explore the relationship between the amplitude of the striations and the power spectral density of the slope errors.

Mistral is the soft X-ray full field microscopy beamline at the ALBA light source. The beamline is designed to have large source acceptance and to provide constant magnification at the exit slit for photon energies between 270 and 2600 eV. The monochromator is a variation of the Petersen plane grating monochromator in which a variable line spacing grating is used to maintain the beam focused at the exit slit, independently of the fixed focus constant, and to cancel aberrations. We present the alignment strategy used to compensate errors of the optical elements, and report about the commissioning results.

We have developed an objective soft x-ray flat-field spectrograph installed in electron microscopes (EMs). The spectrograph has two attractive features. One is that it is designed to cover a wide energy range of 50-4000 eV by using four varied-line-spacing holographic gratings (VLSHGs) optimized for 50–200 eV, 155–350 eV, 300–2200 eV, and 2000–4000 eV. The gratings dedicated for the respective energy ranges can be accommodated in the single spectrograph. This advantage comes from that the positions of the source points and image planes are assumed as the common parameters in the design of all gratings. Therefore, it allows to easily change the energy range by only choosing an appropriate grating and its position. The other is the application of a newly invented W/B4C multilayer coating. It has been adopted to the grating for the 2000–4000 eV range to overcome the considerable decrease of the diffraction efficiency in the energy range above ~2 keV. The novel coating makes it possible to enhance uniformly the diffraction efficiency at a constant incidence angle in the whole energy range.

We measured the thermal-contact-conductance (TCC) of indirect cooling components in synchrotron radiation beamlines. To reduce the strain on the optical element, we explored conditions for insertion materials with a high TCC in region with low contact pressures of 0.1-1.0 MPa. We examined the TCC at the interface between oxygen-free copper (OFC) and insertion materials such as indium, graphite, and gold foil. The TCC depended on the hardness and thickness of the insertion material. Thin indium (20 μm thick) showed the highest TCC. Nickel and gold passivation on the OFC surface reduced the TCC to 30% of that for the bare OFC. Future work will involve exploring the passivation conditions of OFC for higher TCC is and measuring the TCC under cryogenic-cooling conditions.

We developed and fabricated a single layer antireflection coating for the molybdenum/silicon multilayer mirrors.The 20 nm thin film of Si_0.52C_0.16N_0.29, deposited by simultaneous electron beam evaporation and nitrogen ion implantation, causes a broadband suppression of the DUV reflectance with a maximum suppression at λ= 285 nm from 58% to 0.3%, corresponding to a factor of 195.