Measurement of hard X-ray coherence in the presence of a rotating random-phase-screen diffuser

作者：Morgan Kaye S^*; Irvine Sarah C; Suzuki Yoshio; Uesugi Kentaro; Takeuchi Akihisa; Paganin David M; Siu Karen K W

来源：Optics Communications, 2010, 283(2): 216-225.

DOI：10.1016/j.optcom.2009.09.023

• Coherence
• Synchrotron hard X-rays
• Prism interferometer
• Bio-medical phase contrast imaging

A suitably large coherence area is important in coherent X-ray optics, when using techniques such as interferometry or phase contrast imaging (PCI). The work done by Suzuki using a prism interferometer to measure X-ray coherence at 12.4 keV [1] is here extended to consider the use of a diffuser at the bio-medical imaging energy of 25 keV. In order to achieve a broader, more even X-ray field and eliminate speckle, a spinning piece of paper may be used as a rotating random-phase screen to diffuse the hard Xray beam, but this will concomitantly decrease the magnitude of the complex degree of second-order coherence. We also study the effect of source size and source-to-sample distance on coherence, where imaging area and required flux must be considered. Coherence measurements at the 20XU beamline at the SPring-8 synchrotron are compared to results from wave-optical computer modelling. These show that while the diffuser will decrease the magnitude of the complex degree of coherence, further free-space propagation will lessen this effect. In the design of an experiment, the collimating slit size and use of a diffuser must therefore be balanced with distance from the source, in order to maximise coherence while maintaining the desired field of view and exposure time.

• 出版日期2010-1-15