Abstract
Scanning fluorescence X-ray microscopy lets one non-destructively and quantitatively map the distribution of most biologically important metals in cells and tissues. For studies on large-scale tissues and organs, a spatial resolution of several micrometres is often sufficient; in this case, bending magnets at synchrotron light sources provide abundant X-ray flux. We describe here the use of bending magnet beamline 8-BM-B at the Advanced Photon Source with two distinct microscopy stations: a pre-existing one with Kirkpatrick-Baez (KB) mirror optics for slightly higher throughput and the ability to accommodate samples tens of centimetres across, and a new prototype station with an axially symmetric, single-bounce, capillary optic with slightly less flux, but finer resolution at similar fluence per time. The KB station provides δ(res) = 10.5 µm spatial resolution at a per-pixel exposure time of t(dwell) = 100 ms and a fluence per time of 5.8 × 10(7) photons µm(-2) s(-1), while the prototype capillary station provides δ(res) = 6.5 µm at t(dwell) = 50 ms and a fluence per time of 5.6 × 10(7) photons µm(-2) s(-1). We used image power spectral density to estimate the achieved spatial resolution δ(res) from individually acquired images, with δ(res) depending on the optic, the fluorescence signal strength of the sample being imaged, and the method used to process raw fluorescence spectral data.