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19 July 1996 Solar X-ray Imager (SXI) optical performance analysis
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The solar x-ray imager (SXI) telescope has a Wolter-I design with both grazing-incidence mirrors made from a single Zerodur substrate. The mirror fabrication requirements were for 40 percent encircled energy within 5-arc-seconds image diameter at an x-ray wavelength of 8.34 angstrom and for 56 percent, at 44.8 angstrom. The low-spatial-frequency mirror- surface error allocations (including on-orbit effects) were predicted to contribute (Using the ray-trace program GRAZTRACE) a geometric-image core of 3.34 arc seconds RMS diameter. The allocated mid- and high-frequency mirror surface errors had RMS values of 94 angstrom and 5 angstrom, respectively. The x-ray scattering program EEGRAZ was used to predict the resulting 5-arc-second diameter image encircled energies of 48 percent and 67 percent at 8.34 angstrom and 44.8 angstrom, respectively. These predictions exceeded the requirements. The characterization of the mirror as actually fabricated was accomplished using a ZYGO interferometer, a circularity test stand and a WYKO interferometer. Based on this data, the predicted geometric- image core RMS diameter was 4.03 arc seconds. The measured mid- and high-frequency surface errors had RMS values of 104 angstrom and 7.2 angstrom, respectively. Thus the allocated tolerances were not met. The resulting predicted encircled energies at 5-arc-second diameter were 32 and 52 percent at 8.34 angstrom and 44.8 angstrom, respectively. THese values fall short of the requirements for mirror fabrication by a small margin. The actual performance of the SXI mirror will be experimentally tested. The results will then be compared with the predictions.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Martin E. Smithers and David E. Zissa "Solar X-ray Imager (SXI) optical performance analysis", Proc. SPIE 2805, Multilayer and Grazing Incidence X-Ray/EUV Optics III, (19 July 1996);

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