The hard X-ray nanoprobe beamline (HXN) designed at the Shanghai Synchrotron Radiation facility (SSRF) will be of capability to realize a focal spot size of 10 nm for hard X-rays to satisfy requirements in biology, environmental, material sciences and etc.. The beamline includes two modes of operation, high energy resolution mode and high flux mode respectively. High flux mode utilizes the multilayer KB system to obtain high-flux diffraction-limited focusing of ~10nm. An ultra-high-precision figure fabrication for diffraction-limited focusing is required to meet the Rayleigh Criterion. An idea to overcome this problem is to introduce a phase compensator upstream of the KB system to compensate the wavefront errors in the beamline. At wavelength speckle-based method will be used to measure the wavefront error in the beamline and feedback to the phase compensator. Vibration measurements have been carried out at the secondary source and endstation hutch. The flexure hinge mechanisms and high-precision actuators ensure the KB system and sample manipulator working with high stability. The building of HXN has been designed and is under construction at present.
Determination of multilayer structure was developed so much, but most of studies focused on the relationship between structural imperfections and reflectivity. These imperfections, whether interfacial roughness and interdiffusion or surface feature, measured by grazing X-ray scattering, atomic force microscopy or electric microscopy, reflect relatively high-frequency characteristics. The mid-frequency figure errors were regarded as the main factor to produce large satellite peaks near the focusing spot in the multilayer K-B mirror and were found to produce stripes in the far-field imaging. We report novel method to study mid-frequency interface and layer growth characterizations of multilayer structure using at-wavelength speckle scanning technique. This work is beneficial for matching multilayer manufacture technology to the optimization of beam performances.
X-ray focusing mirrors with elliptical shape are widely used in synchrotron facilities for micro-, nano-scale focusing experiments. Surface interferometry plays an important role in the x-ray mirrors figuring with subnanometer accuracy. To avoid the second order error in stitching interferometry, relative angle determinable stitching interferometry (RADSI) is under development. This method was first developed by Yamauchi et al from Osaka University, which uses a planar mirror to correct the relative stitching angle between the neighboring subapertures. Here, we use RADSI to measure the x-ray spherical and elliptical mirrors with 300mm aperture Fizeau interferometer. The interferometer is combined with 4 accurate rotation and tilt stages for the stitching measurement. To ensure the stitching accuracy, we first studied the measurement accuracy within every single subaperture. Multiple measurement is used to decease the random error of single subaperture. The subaperture positioning is also carefully corrected to ensure the pixels of the adjacent subapertures in overlapping areas can be matched well. A first stitching measurement result of a spherical mirror with 30 meters radius is shown.