1,721,006 research outputs found
Ex-situ metrology and data processing techniques developed at the ALS for optimization of beamline performance of bendable x-ray mirrors
Full text linkWe discuss experimental, analytical, and numerical methods recently developed at the Advanced Light Source (ALS) X˗Ray Optics Laboratory (XROL) for calibration and precision shaping of bendable x-ray mirrors. The methods are based on ex situ measurements with the mirrors using surface slope profilers available at the ALS XROL. The first realization of methods and dedicated software has allowed the optimization of the beamline performance of bendable mirrors by adjustment of the mirror shape to minimize the root-mean-square variation of residual (after subtraction of the ideal desired shape) slope deviations from ideal (specified) surface figure. Here, we further develop the methods that in application to elliptically bent mirrors adapt as a figure of merit the minimum of the rms size of the focused beam. The efficacy of the developed methods is demonstrated with examples of optimal tuning of an elliptically bendable cylindrical mirror designed for the ALS beamline 10.3.2
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Magnetostrictively deforming the surface of a silicon wafer at two locations
No full textThe only way to increase the sensitivity of X-ray telescopes without significantly increasing their size (compared to existing telescopes) is to use thinner mirror shells. However, to maintain the figure of thin mirror shells, their shape will need to be adjusted after they are mounted and/or actively controlled during flight. Here we describe progress toward developing a method that can be used to do both. The core of the concept is to coat thin (<500 μm) X-ray mirrors with a ~10 μm layer of magnetic smart material (MSM). When an external magnetic field is applied to the MSM layer it will expand or contract, changing the shape of the mirror. We have previously demonstrated that this method can be used to generate a single localized deformation on the surface of a test sample. Here we present work to study how two deformations affect each other. The first deformation that we created has a height of ~5 μm. The second deformation, generated by applying a magnetic field to the sample 4 mm from the first position, has a height of ~1 μm. It is likely that the second deformation is smaller than the first because the two areas where the magnetic field was applied were close to each other. This could have caused the MSM to already be partially expanded in the second area when the field was applied there
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Performance of plane wavefront Fizeau interferometers in power spectral density measurements with tilted plane optics
Full text linkBinary pseudo-random array (BPRA) test samples are useful devices for calibrating the instrument transfer function (ITF) of Fizeau interferometers, interferometric microscopes, and other optical and non-optical surface and wavefront metrology instruments. The intrinsic white noise character of the power spectral density (PSD) function of the BPRA pattern simplifies the extraction of the ITF from the measured PSD. The ITF determined in a dedicated calibration experiment can be used to reconstruct the surface height profile from the measured data, effectively enhancing the instrument’s spatial resolution. For a high confidence reconstruction procedure, a reliable analytical model of the IFT is desirable. Usually, the model accounts for the contributions to the ITF related the imperfections of the instrument’s optical and detector systems. Here, we experimentally demonstrate that in the case of surface height metrology with Fizeau interferometers, the PSD measurements and, therefore, the efficacy of the ITF calibration of the tool, are strongly affected by the instrument data acquisition and processing procedures, as well as by the shape of the optic under test and its alignment with respect to the interferometer
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Binary pseudo-random array standards for calibration of 3D optical surface profilers used for metrology with significantly curved x-ray optics
Full text linkHigh-accuracy metrology is vitally important in manufacturing ultra-high-quality free-form mirrors designed to manipulate x-ray light with nanometer-scale wavelengths. The current capabilities and possibility for improvements in x-ray mirror manufacturing are limited by inherent imperfections of the integrated metrology tools. In the case of Fizeau interferometry, metrology tools are currently calibrated with super-polished flat test-standard/reference mirrors. This is acceptable for measuring slightly curved x-ray optics. However, for even moderately curved aspherical x-ray mirrors the flat-reference calibration is not sufficiently accurate and stitching Fizeau interferometer-based surface metrology is used to mitigate the problem. But still, the retrace and aberration errors, as well as the limited spatial resolution, described with the instrument transfer function (ITF), can be transferred into the optical surface topography of x-ray mirrors obtained in stitching metrology. For ITF calibration, we have developed an original technique, based on test standards structured as two-dimensional (2D) highly-randomized (HR) binary pseudo-random arrays (BPRAs). The technique employs the unique properties of the HR BPRA patterns in the spatial frequency domain., i.e. the inherent 2D power spectral density of the HR BPRA pattern has a deterministic white-noise-like character that allows direct determination of the ITF with uniform sensitivity over the entire spatial frequency range and field-of-view of an instrument. Here, we explore technological, metrological, and analytical aspects essential for calibration of the retrace and aberration errors of Fizeau interferometers using different types of tilted test samples, including a super-polished reference mirror for the re-trace calibration and the uniformly redundant array (URA) BPRA standards for the geometrical distortion (aberration) calibration. While the first method was previously demonstrated by researchers at DIAMOND Light Source, a method based on the URA BPRA is described and demonstrated here for the first time. We outline the design and fabrication process used in fabrication of URA BPRA test standards, and present the results of application of the URA BPRA standards demonstrating the high efficacy of our approach to geometrical distortion calibration of Fizeau interferometers. We also discuss the possible sources of unexpected peculiarities of the systematic errors, including an astigmatic character of the retrace error, observed with Fizeau interferometers at the Advanced Light Source X-Ray Optics Laboratory
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Towards super-resolution interference microscopy metrology of x-ray variable-line-spacing diffraction gratings: recent developments
Full text linkWe report on recent work towards improving interference microscopy metrology of variable-line-spacing (VLS) x-ray diffraction gratings through a combination of techniques: image reconstruction to correct for distortion and blurring, multi-image super-resolution data acquisition to increase resolution beyond the single-image limit, and image stitching to increase the measurement area. Here, we concentrate on precision characterization and correction for lens distortion (aka geometrical distortion) and provide precise measurements of the effective image pixel distribution. We present and analyze the results of geometrical distortion measurements performed with test samples, including traditional checkerboard test artifacts and binary pseudo-random array (BPRA) standards patterned with two-dimensional uniformly redundant arrays (URA). The URA BPRA standards are also useful for measurement of the instrument transfer function (ITF), a measure of the optical aberrations and limited lateral resolution of the instrument. We also outline other essential elements and the next steps of the project on development of so-called super-resolution interference microscopy, enabling more precise measurements of VLS groove density than previously possible. The global aim of this project is to integrate our metrology technique into the manufacture of high-resolution x-ray gratings
Hard x-ray wavefront engineering for aberration correction and beam shaping
No full textWhile modern x-ray microscopes at synchrotron radiation sources and free-electron lasers require x-ray optics of highest quality, these optics often show aberrations due to limitations in fabrication technology. Based on ptychography, we determine these aberrations and fabricate tailor made refractive phase plates to compensate for them. Starting from the aberrated optics, diffraction-limited beams can be generated by introducing the phase plate behind these optics. In addition, the wavefront can be modified to generate custom beams for special needs, such as donut-shaped beams with orbital angular momentum or for structured-illumination microscopy. The nanofocused beam can be engineered in shape and phase by introducing specially designed phase plates. We introduce a general scheme for wavefront engineering and illustrate it with a numerical example
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Reliability investigation of the instrument transfer function calibration technique based on binary pseudo-random array standards
Full text linkThe reliability of the instrument transfer function (ITF) calibration technique based on binary pseudo-random array (BPRA) standards is investigated and demonstrated in application to interferometric microscopes. We demonstrate the linearity of the calibration (that is, independence of the ITF calibration on the standards root-mean-square roughness) via comparison of the ITF measurements with a number of artifacts with the etched depth varying from 30 nm to 120 nm. We also show that the calibration does not depend on the surface reflectivity, at least in the range between ∼36% and ∼80%. The criteria for selection of the geometrical parameters of the BPRA standard design appropriate for a particular interferometric microscope arrangement (including optical magnification), as well as the data acquisition and analysis procedures for different applications are also discussed
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The ALS interferometric microscope upgraded for measurements with large x-ray optics and optical assemblies
Full text linkWe describe details of a recent deep upgrade of the MicroMap-570 interferometric microscope available at the Advanced Light Source X-Ray Optics Laboratory. The upgrade has included an improvement of the microscope optical sensor and data acquisition software, design and implementation of automated optic alignment and microscope translation systems, and development of a specialized software for data processing in the spatial frequency domain. With the upgraded microscope, we are now capable for automated (remoted) measurements with large x-ray optics and optical systems. The results of experimental evaluation of the upgraded microscope performance and calibration of its instrument transfer function are also discussed. Because the same already obsolete MicroMap-570 microscopes have been used for years at other metrology laboratories at the x-ray facilities around the globe, we believe that our experience on upgrade of the microscope describe in detail in the present paper is broadly interesting and useful
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Fabrication of low blaze angle gratings by replication and plasma etch
Full text linkWe suggest a new method of making ultra-low blaze angle gratings for synchrotron application. The method is based on reduction of the blaze angle of a master grating by replication followed by a plasma etch. A master blazed grating with a relatively large blaze angle is fabricated by anisotropic wet etching of a Si single crystal substrate. The surface of the master grating is replicated by a polymer material on top of a quartz substrate by nanoimprinting and then transferred into quartz by a plasma etch. Then a 2 nd nanoimprint step is applied to transfer the saw-tooth surface into a resist layer on top of a Si grating substrate. The plasma etch through the patterned resist layer provides transfer of the grooves into the Si substrate and results in reduction of the blaze angle due to the difference in etch rates of the resist and Si. We investigated the impact of the replication process on the groove shape, facet surface roughness, and diffraction efficiency of the fabricated 200 lines/mm low blaze angle grating
A high-speed x-ray radiography setup for in-situ electron beam powder bed fusion at PETRA III
No full textA high-energy white synchrotron x-ray beam enables penetration of relatively thick and highly absorbing samples. At the P61A White Beam Engineering Materials Science Beamline, operated by Helmholtz-Zentrum Hereon at the PETRA III ring of the Deutsches Elektronen-Synchrotron (DESY), a tailored x-ray radiography system has been developed to perform in-situ x-ray imaging experiments at high temporal resolution, taking advantage of the unprecedented x-ray beam flux delivered by ten successive damping wigglers. The imaging system is equipped with an ultrahigh-speed camera (Phantom v2640) enabling acquisition rates up to 25 kHz at maximal resolution and binned mode. The camera is coupled with optical magnification (5x, 10x) and focusing lenses to enable imaging with a pixel size of 1,35 micrometre. The scintillator screens are housed in a special nitrogen gas cooling environment to withstand the heat load induced by the beam, allowing spatial resolution to be optimized down to few micrometres. We present the current state of the system development, implementation and first results of in situ investigations, especially of the electron beam powder bed fusion (PBF-EB) process, where the details of the mechanism of crack and pore formation during processing of different powder materials, e.g. steels and Ni-based alloys, is not yet known
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