The X-ray beam expander for advanced synchrotron sources based on Si planar compound parabolic refractive lenses (CRLs) with aperture of 10 micron was considered. The lenses were fabricated by using MEMS technologies including a lithography and a deep silicon etching for CRLs pattern generation in the hard mask and the pattern transfer into silicon wafer down to 40 μm, respectively. To minimize an influence of the manufacturing errors on the CRLs optical properties special control and metrology of the geometrical parameters of the lenses were proposed and applied. The errors influence on the X-ray beam expander parameters was considered theoretically and the related computer simulations were performed.
The X-ray planar compound refractive lenses (CRLs) made of monocrystalline silicon by a lithography and plasma deep Si etching (Bosch process) were considered. The CRL is a planar structure of biconcave parabolic refractive surfaces etched into silicon wafers down to 70 μm. The geometrical parameters of the parabolic lens structures were measured by different SEM-based methods and compared with CAD data. The influence of the manufacturing errors on the CRLs optical properties was discussed. The approaches for the improvement of the lens manufacturing techniques were proposed.
Recently we demonstrated the phase-sensitive X-ray imaging technique based on the bilens interferometer. The essence of the method consisted of scanning a sample, which was set upstream of the bilens across the beam of one lens of the bilens, and recording changes in the interference pattern. This optical scheme involves fine-tuning the position of the sample on the optical axis, while a small deviation can lead to some distortion of its reconstructed phase profile. In this work, the advanced optical layout is considered. Knowing that the bilens generate two diffraction-limited focal spots, the sample can be placed in the focal plane of the bilens CRLs. In this case, the small size of the focused beams provides excellent phase sensitivity and high spatial resolution allowing to avoid possible distortions of the phase profile completely. The capabilities of both optical schemes were studied theoretically and experimentally.
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