In order to meet the at-wavelength detection requirements of ultra-high precision optical elements, a metrology device based on single grating interferometry is developed on the test beamline at the Shanghai Synchrotron Radiation Facility (SSRF). First, this device uses a single grating configuration, combined with a high-resolution detection system and spatial harmonic imaging technology to form a wavefront detector. Then, using the single grating Talbot interferogram, the sample spectrum is analyzed by Fourier transform of the interferogram. Finally, the systematic error of the wavefront detector is analyzed, and the surface gradient of the composite refractive lens is measured with this device. The experimental results show that the systematic error of the single grating wavefront detector is less than /50 rms, and the surface shape error of the compound refractive lens is about /33 rms. This device can meet the detection requirements of ultra-high precision optical elements.
In recent years, X-ray phase sensing technology has been widely used in at-wavelength metrology and optical characterization. One of the latest developments is the technology based on X-ray speckle. It has attracted wide attention because of its simple and flexible experimental arrangement, high-cost performance, multi-mode, and high angular sensitivity. The speckle-based technique can precisely measure the wavefront and associated aberrations and is therefore a suitable device for in-situ metrology. Shanghai Synchrotron Radiation Facility (SSRF) has been implemented and further improved such a technique. We have demonstrated that the speckle-based technique can be used in the wavefront measurement of the reflective and transmissive optics and diffraction optics such as mirrors, lens, and crystals. This paper will introduce the latest developments in speckle-based wavelength measurement technology and some application examples at SSRF.
The performance of the optical elements at-wavelength measurement is affects by the synchrotron radiation beam divergence angle, and it is necessary to modulate a highly collimated X-ray as the measurement beam. In this paper, a multiple-crystal X-ray diffraction system composed by the channel-cut crystal, which is used to suppress the angular divergence of the synchrotron radiation beam. The Si(111) channel-cut crystal should work at the energy range of 10- 18keV, which can suppress the angular divergence of the beam lower than the Darwin width of the double crystals. The divergence angle was measured by the Si(111) analyzer is 2.9″@10keV at the vertical direction and 2.01″@18keV at the horizontal direction. The measurement results shows that the channel-cut crystal can suppress the synchrotron beam divergence angle and provide a high collimated light for the at-wavelength measurement of the optical components.
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