Abstract
At-wavelength phase-shifting point diffraction interferometer (PDI) is a technique to measure wavefront error of EUV lithography optics. While they use radiation from undulators in medium size electron storage rings with further wavelength purification by monochrometers, we propose to use direct radiation from a compact undulator. We carried out an experiment at NewSUBARU and found that rather broad band radiation is applicable to this PDI, which is attributed to the wavelength dependency of grating diffraction. We designed an undulator with a periodic length of 2.9 cm, periodic number of 150 and magnetic field of 4.4 kG to be installed in a small storage ring. Applying a beam line conversion efficiency of 200, the exposure time to take one PDI picture for future EUVL optics was estimated to be 2.4 s with proper margin.
Published Version
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