This PDF file contains the front matter associated with SPIE Proceedings Volume 8502, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

In an ongoing effort to advance the state of the art in x-ray nanofocusing optics ^[1], multilayer Laue lens (MLL) ^[2,3] fabrication at NSLS-II has matured to include multi-gas reactive sputtering for stress and interfacial roughness reduction, which has recently led to a 70 micron thick single-growth MLL. Reactive sputtering was found to produce WSi₂/Si multilayers with an accumulated film stress significantly lower than Ar-only deposition with identical growth conditions. Significant effort has been focused on the achievement of highly-stable gas mixing and process gas pressure measurement for multilayer growth and the problems faced along with implemented solutions will be discussed in detail. Proper layer thickness and placement throughout the stack presents a major obstacle to the fabrication of high-quality nanofocusing MLLs. Initial metrology of extremely thick MLLs by stitching many scanning electron microscope images was found to be greatly simplified by inclusion of marker labels within the stack.

Chirped broadband multilayer mirrors are key components to shape attosecond pulses in the XUV range. Compressing high harmonic pulses to their Fourier limit is the major goal for attosecond physics utilizing short pulse pump-probe experiments. Here, we report about the first implementation of multilayers fulfilling these requirements in the “waterwindow” spectral range.

A soft X-ray, beam-splitting, multilayer optic has been developed for the Bragg Reflection Polarimeter on the NASA Gravity and Extreme Magnetism Small Explorer Mission (GEMS). The optic is designed to reflect 0.5 keV X-rays through a 90 degree angle to the BRP detector, and transmit 2-10 keV X-rays to the primary polarimeter. A transmission requirement prevents the use of a thick substrate, so a 2 µm thick polyimide membrane was used. Atomic force microscopy has shown the membrane to possess high spatial frequency roughness less than 0.2 nm rms, permitting adequate X-ray reflectance. A multilayer thin film was especially developed with reflectance and transmission properties that satisfy the BRP requirements and with near-zero stress. Multilayer depositions for prototype reflectors have been performed via magnetron sputtering. Reflectivity and transmission measurements closely match theoretical predictions, both before and after rigorous environmental testing.

Recently, a new software tool was developed at the ESRF that can perform wave optical simulations on curved multilayer optics. It is based on a Takagi-Taupin approach and the two beam approximation. Outside the multilayer structure the beam is propagated by phase ray tracing and by solving the Kirchhoff integral. Extended sources can be modelled by superposition of point sources. The spatial coherence can be varied by the degree of random averaging of amplitude and phase of these point sources and by their distribution in space. This work deals with applications of this formalism to realistic cases of existing or planned multilayer based nanofocusing mirrors. It also attempts to explore fundamental physical limitations and how they are reproduced by the model. Open questions will be addressed and potential future investigations will be outlined.

We employ a coded aperture pattern in front of a charge couple device (CCD) pixilated detector to image fluorescent xrays (6-25KeV) from samples irradiated with synchrotron radiation. Coded apertures encode the angular direction of xrays, and given a known source plane, allow for a large Numerical Aperture x-ray imaging system. The algorithm to develop the free standing coded aperture pattern of the Non-Two-Holes-Touching (NTHT) was developed. The algorithms to reconstruct the x-ray image from the encoded pattern recorded are developed by means of modeling and confirmed by experiments on standard samples. Spatial resolution and efficiency are determined for the next development stage whereby an energy resolving pixilated CCD will be deployed allowing for elemental imaging.

Beam quality of diamond double-crystal monochromator was characterized at undulator beamlines of SPring-8. The <001<-growth (111) IIa diamond crystals were used for high-heat-load double-crystal monochromator. Main issue of IIa diamond monochromator was intensity non-uniformity of reflected beam that was enhanced at the experimental station more than 10 m apart from monochromator. The simple Fresnel diffraction models from segments of the crystal are introduced to explain the origin of non-uniformity. Lattice inclination across growth sector boundary with 0.5 μrad or more, or lattice step due to stacking faults may cause phase shift between segments. The non-uniformity increases up to ~50% using the simple models. We also characterized recently-available <111<-growth crystals at 1-km beamline of SPring-8. The quality is similar to that of previous <001<-growth crystals, regarding rocking curve width for whole region irradiation.

The very low emittance and low energy spread source of a future Cornell energy recovery linac (ERL) will be equipped with long undulators of large numbers of short period magnets. The power density in the undulator radiation central cone will be much higher than that from normal undulators at current 3^rd generation sources. The deformation of liquid nitrogen (LN₂) cooled silicon crystal monochromators for ERL beamlines is evaluated by parameterizing the thermal problem with a modified linear power density function based on a simplified analytical model. This provides a clear and “universal” description of thermal deformation under different thermal footprints, variable loads and is independent of specific facility. The characteristics of thermal deformation of LN₂-cooled Si crystals for Cornell ERL undulators is also given using finite element analysis (FEA).

X-ray monochromators, made of single crystals or multilayer coatings, are the most common optical components on many synchrotron beamlines. They intercept the broad-spectrum x-ray (white or pink) beams generated by the radiation source and absorb all but select narrow spectral bands of x-rays, which are diffracted according to Bragg’s Law. With some incident beam power in the kW range, minimizing thermally induced deformation detrimental to the performance of the device necessitates the design of optimally cooled monochromators. Monochromator substrate designs have evolved, in parallel with thermal loads of the incident beams, from simple blocks with no cooling, to water cooled (both contact -cooled and internally cooled), and to cryogenically cooled designs where the undesirable thermal distortions are kept in check by operating in a temperature range where the thermomechanical properties of the substrate materials are favorable. Fortuitously, single-crystal silicon at cryogenic temperatures has an exceptionally favorable combination of high thermal conductivity and low thermal expansion coefficient. With further increases in x-ray beam power, partly as a result of the upgrades to the existing synchrotron facilities, the question arises as to the ultimate limits of liquid-nitrogen-cooled silicon monochromators’ ability to handle the increased thermal load. In this paper, we describe the difficulties and begin the investigation by using a simple geometric model for a monochromator and obtain analytical solutions for the temperature field. The temperature can be used as a proxy for thermally induced deformation. The significant role of the nonlinear material properties of silicon is examined.

In this work, we investigate a novel design of optical system for astrophysics. In addition, a new testing method in the X-ray laboratory was verified. The proposed optical system is composed of modules with Kirkpatrick-Baez configuration allowing usage of multi-foil mirrors arranged along a parabolic profile. This system effectively uses a circular aperture, which is divided into petals. Individual petals consist of diagonally oriented KB cells with a common focus. This optical system can be improved by a set of nested rotationally symmetric X-ray mirrors in order to achieve higher reflection efficiency in harder part of considered spectrum.

NASA/MSFC and SAO have developed a High Resolution EUV Solar Coronal Imaging telescope (Hi-C). The scientific objective of the mission is to determine, at higher spatial resolution than previously available, the geometric configuration and topology of the structures making up the inner corona. The Hi-C telescope launched on a rocket in early July 2012. It acts as a technology pathfinder for future satellite based missions. Key technology features of the Hi-C telescope are: (1) A 23.9 meter focal length, allowing for 0.1 arc-second pixels (2) Extremely high quality optics (3) Single wavelength multi-layer coating over the entire surface of each optic (4) Low distortion approach to mounting the primary into the telescope. The low distortion approach to mounting the primary mirror into the telescope is discussed in this paper. In previous solar EUV telescopes (TRACE, AIA, IRIS) the primary mirror is first bonded into a flexured mirror cell that is then bolted into the telescope. Techniques for bonding the mirror into the mirror cell have been well developed. If done properly, these techniques produce minimal distortion in the optic. Experience has shown, however, that bolting of the cell into the telescope produces distortions, typically in the form of astigmatism. The magnitude of the astigmatism may be acceptable for lower resolution missions, but as we approach ever higher resolutions, these astigmatisms contribute significantly to the error budget. In the Hi-C mission the mirror mounting hardware was completely assembled into the telescope tube prior to bonding the mirror to the mount. This final operation was done with the telescope tube vertical and the primary mirror surface facing up. This approach minimizes the "bolt-up" distortions typically seen, thus improving resolution.

Ultra-precision diamond turning can deliver very accurate form, often less than 100nm P-V. A possible manufacturing method for thin Wolter type-1 mirrors in hard X-ray space telescopes thus involves generating electroless nickel plated mandrels by diamond turning, before coating them with a reflective film and substrate. However, the surface texture after turning falls far short from the requirements of X-ray and EUV applications. The machining marks need to be removed, with hand polishing still widely employed. There is thus a compelling need for automated finishing of turned dies. A two step finishing method is presented that combines fluid jet and precessed bonnet polishing on a common 7-axis CNC platform. This method is capable of finishing diamond turned electroless nickel plated dies down to 0.28nm rms roughness, while deterministically improving form error down to 30nm P-V. The fluid jet polishing process, which consists of pressurizing water and abrasive particles for delivery through a nozzle, has been specially optimized with a newly designed slurry delivery unit and computer simulations, to remove diamond turning marks without introducing another waviness signature. The precessed bonnet polishing method, which consists of an inflated membrane rotated at an angle from the local normal to the surface and controlled by geometrical position relative to the work-piece, is subsequently employed with a novel control algorithm to deliver scratch-free surface roughness down to 0.28 nm rms. The combination of these two deterministic processes to finish aspheric and freeform dies promises to unlock new frontiers in X-ray and EUV optics fabrication.

CHESS has pioneered the development of X-ray Video Beam Position Monitors (VBPMs). Unlike traditional photoelectron beam position monitors that rely on photoelectrons generated by the fringe edges of the X-ray beam, with VBPMs we collect information from the whole cross-section of the X-ray beam. VBPMs can also give real-time shape/size information. We have developed three types of VBPMs: (1) VBPMs based on helium luminescence from the intense white X-ray beam. In this case the CCD camera is viewing the luminescence from the side. (2) VBPMs based on luminescence of a thin (~50 micron) CVD diamond sheet as the white beam passes through it. The CCD camera is placed outside the beam line vacuum and views the diamond fluorescence through a viewport. (3) Scatter-based VBPMs. In this case the white X-ray beam passes through a thin graphite filter or Be window. The scattered X-rays create an image of the beam’s footprint on an X-ray sensitive fluorescent screen using a slit placed outside the beam line vacuum. For all VBPMs we use relatively inexpensive 1.3 Mega-pixel CCD cameras connected via USB to a Windows host for image acquisition and analysis. The VBPM host computers are networked and provide live images of the beam and streams of data about the beam position, profile and intensity to CHESS’s signal logging system and to the CHESS operator. The operational use of VBPMs showed great advantage over the traditional BPMs by providing direct visual input for the CHESS operator. The VBPM precision in most cases is on the order of ~0.1 micron. On the down side, the data acquisition frequency (50-1000ms) is inferior to the photoelectron based BPMs. In the future with the use of more expensive fast cameras we will be able create VBPMs working in the few hundreds Hz scale.

We demonstrate the use of electrostatically driven micro-electromechanical systems (MEMS) devices to control and deliver synchrotron x-ray pulses at high repetition rates. Torsional MEMS micromirrors, rotating at duty cycles of 2 kHz and higher, were used to modulate grazing-incidence x rays, producing x-ray bunches shorter than 10 μs. We find that dynamic deformation of the oscillating micromirror is a limiting factor in the duration of the x-ray pulses produced, and we describe plans for reaching higher operating frequencies using mirrors designed for minimal deformation.

Polycapillary optics provide a promising approach for coupling highly-divergent x-ray emission or inelastic scattering to high-resolution crystal analyzers. We present recent results looking at the application of polycapillary collimators to emission spectrometers. The first application uses a collimating optic and a flat crystal to provide a tunable x-ray fluorescence detector. At high-flux synchrotron radiation sources there is sufficient flux (~10¹³ ph/sec) to allow application of X-ray Absorption Spectroscopy (XAS) to ppb concentrations if the fluorescence signal can be isolated from an intense background. The polycapillary based analyzer easily achieves the <10⁶ background reduction needed for such measurements. It has the additional advantage of being confocal, only collecting the signal from a small volume at the optic focus, effectively eliminating background from sample substrates, windows, or air scattering. Second, the same type of analyzer can be used for higher-resolution emission spectroscopy if operated close to 90° Bragg angle, and we report results of the commissioning of a user-available instrument suitable for few-eV resolution emission spectroscopy, including the demonstration of roughly order-of-magnitude improved measurement times compared to use of a traditional, single spherically-bent crystal analyzer. As part of this effort, we have developed a process for enhancing the integral reflectivity of Si analyzer crystals through plastic deformation at high temperatures.

Spectrograph is an optical device that is used to disperse photons of different energies E into distinct directions and space locations, and to take a snapshot of the whole spectrum of photon energies with a spatially sensitive photon detector. Substantial advantage of a spectrograph over an ordinary spectral analyzer, is its ability to deal with many photon energies simultaneously, thus reducing exposure time per spectrum considerably. To realize a spectrograph, dispersing elements with large angular dispersion rate are required. In visible light optics this is easily achieved with diffraction gratings. In hard x-ray regime this is a problem. Here we show, on the example of CDW x-ray optics, that multi-crystal arrangements may feature cumulative angular dispersion rates more than an order of magnitude larger than those attainable in single Bragg reflections. This makes, first, hard x-ray spectrographs feasible, and, secondly, a resolving power beyond E/ΔE approximate > 10⁸

We report the fabrication and characterization of lithographically-fabricated arrays of micron-scale collimating channels, arranged like spokes around a single source position, for use in 3D, or confocal x-ray uorescence microscopy. A nearly energy-independent depth resolution of 1.7±0.1μm has been achieved from 4.5-10 keV, degrading to 3⊥0.5μm at 1.7 keV. This represents an order-of-magnitude improvement over prior results obtained using state-of-the-art, commercial polycapillaries as the collection optic. Due to their limited solid angle, the total collection efficiency of these optics is approximately 10× less than that obtained with polycapillaries. Three designs have been tested, with 1, 2, and 5-μm-wide channels ranging from 30-50 μm in depth and 2 mm in length. In addition to characterizing the devices in confocal geometry, the transmission behavior of individual channels was characterized using a small, highly collimated incident beam. These measurements reveal that, despite taking no particular steps to create smooth channel walls, they exhibit close to 100% reectivity up to the critical angle for total external reflection. Most of this reflected power is spread into a diffuse angular region around the specular reflection condition. These results significantly impact future designs of such collimating channels, since transmission through the channels via side-wall reflection limits their collimating power, and hence device resolution. Ray-tracing simulations, designed specifically for modeling the behavior of channel arrays, successfully account for the transmission behavior of the optics, and provide a useful tool for future optic design.

Traditional tube-based x-ray sources are widely employed in medical imaging, security screening, and industrial inspection. The cone-beam produced by these tubes is simple to apply, but often demands a long stand-off distance to the object of interest. When combined with the bulk of tubes and their attendant power supplies and cooling systems, the footprint requirement of traditional sources often impedes their use, especially in mobile situations. Here we present an approach to a distributed, flat-panel x-ray source, which eliminates the aforementioned bulk, weight and need for standoff. This source uses spontaneous polarization in pyroelectric crystals to generate high fields and field enhanced emission from micropatterned tips to create a large array of electron beamlets. When combined with a transmission Bremsstrahlung target, a mechanism for raster control of the emitters, and a collimator, this source offers a new and cost effective way to perform stationary and portable imaging. The working principles and performance characteristics of this source are presented. The demands placed on the imaging detector and image processing are also described. Finally, prospects for new promising applications (such as mammography) are mentioned.

Crystal-based x-ray optics are widely used in the synchrotron radiation field. Such optics include monochromators, channel-cut crystals, spectral analyzers, and phase plates that are generally made with standard fabrication tools such as grinders, ultrasonic mills, blade saws, and wire saws. However, modern synchrotron radiation instruments require more complicated and high-precision crystal structures that cannot be fabricated by these conventional tools. Examples include narrow channels and crystal cavities that require smooth and strain-free sidewalls or inner surfaces. Since it is extremely difficult to polish such surfaces by conventional means, specialized cutting tools are required to make the as-cut surfaces as smooth as possible. A possible way to obtain such smooth surfaces is to use a dicing saw as a fabrication tool - a tool typically used in the microelectronics industry to cut or dice semiconductor and other materials. Here we present our studies on the use of dicing saws for cutting innovative, monolithic, x-ray optic devices comprised of tall, narrow-standing, thin crystal-plate arrays. We report cutting parameters that include the rotational speed of the cutting blade (a.k.a. spindle speed), cutting speed (a.k.a. feed rate), number of passes for each cut depth (if required), and diamond grit size for producing the flattest and most smooth side walls. Blade type and construction (sintered, Ni, and resin) also play critical roles in achieving optimum results. The best experimental data obtained produced an average surface roughness of 49 nm and a peak-to-valley flatness of 3625 nm. By achieving these results, we have been able to assist experimenters in the synchrotron radiation field in their efforts to create functional and novel optical devices.

Increased thermal power of the x-ray beams produced at synchrotron radiation facilities such as the Advanced Photon Source at Argonne National Laboratory requires improvements in the thermal management of the components with which the beams interact. Crystals of silicon, germanium, diamond, beryllium, and silicon carbide are important substrate materials in this regard. Accurate physical, thermal, and mechanical properties of these materials, especially at cryogenic temperatures, are needed in the analysis and design of high heat load x-ray components. In this paper, we present a collection of the relevant data, and include curve fits, when possible, for ease of use in the analysis.

Beamline 10.0.1 delivers the photons from a 4.5 m long 10 cm periodicity undulator (U100) to various endstations in its three branchlines. The beamline uses a spherical grating monochromator (SGM) to produce high energy resolution photon beam, with three gratings to cover the photon energy range from 17 to 340 eV. Typically, angle-resolved photoemission (ARPES) measurements use 30-70 eV photons. The beam size at the High Energy Resolution Spectroscopy (HERS) endstation, designed for ARPES, is measured to be 250 μm (H) by 100 μm (V). Due to grazing incidence geometry in the HERS endstation, the photon beam will have a large projection on the sample surface which could lead to degradation of experimental resolutions. We are in the process of designing and replacing some of the existing mirrors to improve the focus spot at HERS endstation. The detailed design parameters and possible upgrade paths will be presented with verifications using SHADOW ray-tracing program.