Abstract
Polycapillary devices focus X-rays by means of multiple reflections of X-rays in arrays of bent glass capillaries. The size of the focal spot (typically 10–100 μm) limits the resolution of scanning, absorption and phase-contrast X-ray imaging using these devices. At the expense of a moderate resolution, polycapillary elements provide high intensity and are frequently used for X-ray micro-imaging with both synchrotrons and X-ray tubes. Recent studies have shown that the internal microstructure of such an optics can be used as a coded aperture that encodes high-resolution information about objects located inside the focal spot. However, further improvements to this variant of X-ray microscopy will require the challenging fabrication of tailored devices with a well-defined capillary microstructure. Here, we show that submicron coded aperture microscopy can be realized using a periodic grid that is placed at the output surface of a polycapillary optics. Grid-enhanced X-ray coded aperture microscopy with polycapillary optics does not rely on the specific microstructure of the optics but rather takes advantage only of its focusing properties. Hence, submicron X-ray imaging can be realized with standard polycapillary devices and existing set-ups for micro X-ray fluorescence spectroscopy.
Highlights
Experiment, object details at a resolution of approx. 8 microns could be reconstructed using an optics with a 40 μm spot[15]
We demonstrate submicron coded aperture microscopy using an external periodic grid placed at the output surface of the polycapillary optics
In contrast to previous approaches, in which the internal microstructure was used as the coded aperture, grid-enhanced X-ray coded aperture microscopy with polycapillary optics does not rely on the specific structure of a polycapillary optics
Summary
Experiment, object details at a resolution of approx. 8 microns could be reconstructed using an optics with a 40 μm spot[15]. To overcome this problem, a special variant of XCAMPO, namely, defect-assisted microscopy[26], was proposed This approach takes advantage of natural point defects in polycapillary structures, such as missing, crushed or slightly larger capillaries. It was demonstrated that such intrinsic point defects, by breaking the periodicity of capillary arrays, lead directly to the formation of multiple X-ray images of an object placed inside the focal spot of a polycapillary optics. Such multiple images can be analysed using the coded aperture principle and provide a spatial resolution at the level of 0.5 μm. The shape of the coded aperture could be optimized using existing microand nanofabrication technology
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