"Scanning Phase Contrast Microscopy with a Segmented Detector"Christian Holzner,1 Benjamin Hornberger,1,4 Martin de Jonge,2 David Paterson,2 Konstatine Ignatyev,3 Stefan Vogt,3 Ian McNulty3 and Chris Jacobsen1 1Department of Physics and Astronomy, Stony Brook University Phase Contrast dominates over absorption in transmission imaging (i.e. of low-Z elements) over a wide range of x-ray energies. In a scanning transmission x-ray microscope (STXM) differential phase contrast (DPC) images can be obtained by measuring spatial beam intensity variations in the transmission detector plane with a multi-segment detector. A segmented detector capable of phase contrast imaging in a STXM has been developed at Stony Brook University [1] for operation at the NSLS. A later version of this detector suitable for hard x-rays was developed together with fluorescence beamlines at the APS [2] where it is now in routine use; furthermore efforts are underway to install the detector at the newly built nanoprobe beamline at the APS and at the Australian Synchrotron. Two methods for the retrieval of the refractive index from images obtained with this detector have recently been published [3] and [4], allowing for quantitative phase reconstruction of the specimen. Hard x-ray fluorescence (XRF) microprobes excel at mapping and quantification of trace elements in biological specimens. However, current XRF microprobes have significant difficulties in determining absolute concentrations, correlating metal distributions with soft tissue ultrastructure, as well as giving full three dimensional information of the biological specimen. We are developing scanning phase contrast microscopy to complement conventional XRF microprobes in order to overcome their shortcomings. In a scanning microprobe DPC images can be obtained at no cost to the fluorescence by measuring the transmission signal of the specimen; therefore, making the two techniques highly complementary. [1] M. Feser, B. Hornberger, C. Jacobsen, et al. NIMA (2006) 565, 841-54 |