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Title: A microstitching interferometer for evaluating the surface profile of precisely figured hard x-ray K-B mirrors.

Abstract

Fabrication and evaluation of elliptical X-ray mirrors, such as Kirkpatrick-Baez (K-B) mirrors produced by the profile-coating technique, requires accurate surface figure measurements over a wide range of spatial frequencies. Microstitching interferometry has proven to fulfill this requirement for length scales from a few {micro}m up to the full mirror length. At the Advanced Photon Source, a state-of-the-art microroughness microscope interferometer that incorporates advanced microstitching capability has been used to obtain measurements of profile-coated elliptical K-B mirrors. The stitched surface height data provide previously unattainable resolution and reproducibility, which has facilitated the fabrication of ultrasmooth (< 1 nm rms residual height) profile-coated mirrors, whose hard X-ray focusing performance is expected to approach the diffraction limit. This paper describes the system capabilities and limitations. Results of measurements obtained with it will be discussed and compared with those obtained with the Long Trace Profiler.

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
970794
Report Number(s):
ANL/XSD/CP-60273
TRN: US1000913
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: SPIE Optics and Photonics 2007; Aug. 26, 2007 - Aug. 30, 2007; San Diego, CA
Country of Publication:
United States
Language:
ENGLISH
Subject:
43 PARTICLE ACCELERATORS; ADVANCED PHOTON SOURCE; DIFFRACTION; EVALUATION; FABRICATION; FOCUSING; INTERFEROMETERS; INTERFEROMETRY; MICROSCOPES; MIRRORS; OPTICS; PERFORMANCE; RESOLUTION; HARD X RADIATION

Citation Formats

Assoufid, L., Qian, J., Kewish, C. M., Liu, C., Conley, R., Macrander, A. T., Lindley, D., Saxer, C., X-Ray Science Division, and KLA-Tencor. A microstitching interferometer for evaluating the surface profile of precisely figured hard x-ray K-B mirrors.. United States: N. p., 2007. Web. doi:10.1117/12.736384.
Assoufid, L., Qian, J., Kewish, C. M., Liu, C., Conley, R., Macrander, A. T., Lindley, D., Saxer, C., X-Ray Science Division, & KLA-Tencor. A microstitching interferometer for evaluating the surface profile of precisely figured hard x-ray K-B mirrors.. United States. doi:10.1117/12.736384.
Assoufid, L., Qian, J., Kewish, C. M., Liu, C., Conley, R., Macrander, A. T., Lindley, D., Saxer, C., X-Ray Science Division, and KLA-Tencor. Mon . "A microstitching interferometer for evaluating the surface profile of precisely figured hard x-ray K-B mirrors.". United States. doi:10.1117/12.736384.
@article{osti_970794,
title = {A microstitching interferometer for evaluating the surface profile of precisely figured hard x-ray K-B mirrors.},
author = {Assoufid, L. and Qian, J. and Kewish, C. M. and Liu, C. and Conley, R. and Macrander, A. T. and Lindley, D. and Saxer, C. and X-Ray Science Division and KLA-Tencor},
abstractNote = {Fabrication and evaluation of elliptical X-ray mirrors, such as Kirkpatrick-Baez (K-B) mirrors produced by the profile-coating technique, requires accurate surface figure measurements over a wide range of spatial frequencies. Microstitching interferometry has proven to fulfill this requirement for length scales from a few {micro}m up to the full mirror length. At the Advanced Photon Source, a state-of-the-art microroughness microscope interferometer that incorporates advanced microstitching capability has been used to obtain measurements of profile-coated elliptical K-B mirrors. The stitched surface height data provide previously unattainable resolution and reproducibility, which has facilitated the fabrication of ultrasmooth (< 1 nm rms residual height) profile-coated mirrors, whose hard X-ray focusing performance is expected to approach the diffraction limit. This paper describes the system capabilities and limitations. Results of measurements obtained with it will be discussed and compared with those obtained with the Long Trace Profiler.},
doi = {10.1117/12.736384},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Computer simulations of nanofocusing by elliptical mirrors are presented wherein the diffraction and propagation of coherent hard x rays are predicted using wave-optical calculations. Surface height data acquired via microstitching interferometry were used to calculate the complex pupil function of a mirror, taking into account the Fresnel reflectivity and treating the surface topography as an aberration to a perfect elliptical mirror. The reflected wave-field amplitude and phase downstream of the mirror were obtained by numerically evaluating the Fresnel-Kirchhoff diffraction integral. Simulated intensity profiles and contours (isophotes) around the focal plane are presented for coherent illumination by a15 keV point source,more » which indicate nearly diffraction-limited focusing at the40 nm level. The effect of high spatial frequency microroughness on nanofocusing was investigated by low-pass filtering the Fourier spectrum of the residual height profile. Simulations using the filtered metrology data confirmed that roughness length scales shorter than0.1 mm have a minor effect on the focal spot size and intensity.« less
  • Stitching interferometry, using small-aperture, high-resolution, phase-measuring interferometry, has been proposed for quite some time now as a metrology technique to obtain 3-dimensional profiles of surfaces of oversized optical components and substrates. The aim of this work is to apply this method to the specific case of long grazing-incidence x-ray mirrors, such as those used in beamlines at synchrotron radiation facilities around the world. Both fabrication and characterization of these mirrors would greatly benefit from this technique because it offers the potential for providing measurements with accuracy and resolution better than those obtained using existing noncontact laser profilers, such as themore » long trace profiler (LTP). Measurement data can be used as feedback for computer-controlled fabrication processes to correct for possible topography errors. The data can also be used for simulating and predicting mirror performance under realistic conditions. A semiautomated stitching system was built and tested at the X-ray Optics Metrology Laboratory of the Advanced Photon Source at Argonne National Laboratory. The initial objective was to achieve a measurement sensitivity on the order of 1 {micro}rad rms. Preliminary tests on a 1 m-long x-ray mirror showed system repeatability of less than 0.6 {micro}rad rms. This value is comparable to that of a conventional LTP. The measurement accuracy was mostly affected by environmental perturbations and system calibration effects. With a fully automated and improved system (to be built in the near future), we expect to achieve measurement sensitivity on the order of 0.0 {micro}rad rms or better. In this paper, after a brief review of basic principles and general technical difficulties and challenges of the stitching technique, a detailed description of the measurement setup is given and preliminary results obtained with it are analyzed and discussed.« less
  • Long trace profilers (LTPS) have been used at many synchrotron radiation laboratories worldwide for over a decade to measure surface slope profiles of long grazing incidence x-ray mirrors. Phase measuring interferometers (PMIs) of the Fizeau type, on the other hand, are being used by most mirror manufacturers to accomplish the same task. However, large mirrors whose dimensions exceed the aperture of the Fizeau interferometer require measurements to be carried out at grazing incidence, and aspheric optics require the use of a null lens. While an LTP provides a direct measurement of ID slope profiles, PMIs measure area height profiles frommore » which the slope can be obtained by a differentiation algorithm. Measurements of the two types of instruments have been found by us to be in good agreement, but to our knowledge there is no published work directly comparing the two instruments. This paper documents that comparison. We measured two different nominally flat mirrors with both the LTP in operation at the Advanced Photon Source (a type-II LTP) and a Fizeau-type PMI interferometer (Wyko model 6000). One mirror was 500 mm long and made of Zerodur, and the other mirror was 350 mm long and made of silicon. Slope error results with these instruments agree within nearly 100% (3.11 {+-} 0.15 {micro}rad for the LTP, and 3.11 {+-} 0.02 {micro}rad for the Fizeau PMI interferometer) for the medium quality Zerodur mirror with 3 {micro}rad rms nominal slope error. A significant difference was observed with the much higher quality silicon mirror. For the Si mirror, slope error data is 0.39 {+-} 0.08 {micro}rad from LTP measurements but it is 0.35 {+-} 0.01 {micro}rad from PMI interferometer measurements. The standard deviations show that the Fizeau PMI interferometer has much better measurement repeatability.« less
  • Of the many methods used to focus x-rays, the use of mirrors with an elliptical curvature shows the most promise of providing a sub-micron white light focus. Our group has been developing the techniques of controlled bending of mirror substrates in order to produce the desired elliptical shape. We have been successful in producing surfaces with the required microradian slope error tolerances. Details of the bending techniques used, results from laboratory slope error measurements using a Long Trace Profiler (LTP) and data from the measurement of focus shape using knife edge and imaging methods using x-rays in the 5-12 KeVmore » energy range are presented. The development of a white light focusing opens many possibilities in diffraction and spectroscopic studies.« less
  • The authors have developed an x-ray micro-probe facility utilizing mirror bending techniques that allow white light x-rays (4--12keV) from the Advanced light Source Synchrotron to be focused down to spot sizes of micron spatial dimensions. They have installed a 4 crystal monochromator prior to the micro-focusing mirrors. The monochromator is designed such that it can move out of the way of the input beam, and allows the same micron sized sample to be illuminated with either white or monochromatic radiation. Illumination of the sample with white light allows for elemental mapping and Laue x-ray diffraction, while illumination of the samplemore » with monochromatic light allows for elemental mapping (with reduced background), micro-X-ray absorption spectroscopy and micro-diffraction. The performance of the system will be described as will some of the initial experiments that cover the various disciplines of Earth, Material and Life Sciences.« less