A novel imaging x-ray microscope based on a spherical crystal

Abstract

A novel, compact, large field, and spectrally tunable imaging x-ray microscope is presented. It is based on the use of an isotropic point x-ray source and a spherically curved crystal. The x-ray beam intensity is modulated by the object attenuation, then monochromatized and enlarged using a spherical crystal and, finally, imaged using a detector downstream from the crystal. We demonstrate by ray tracing simulations that this system allows microscopy studies with high spatial resolution, high magnification ratios, and large field of view. Microscopes using this model can be easily built using different x-ray sources, like conventional x-ray tube generators, x rays emitted by laser-generated plasmas or x-pinch plasmas, and also synchrotron radiation when used in combination with other condenser optics. Preliminary experiments are presented to demonstrate the feasibility of the proposed setup. High resolution (∼4 μm) monochromatic (δλ/λ∼10−5–10−3) images over a large field of view (few mm2) were recorded in the spectral range 8–14 Å using a laser-generated plasma source and a spherical mica crystal. Compared to x-ray crystal imagers used in relation with plasma sources, the new configuration produces high quality stigmatic images working at many different Bragg angles, thus improving the spectral tunability and allowing a more flexible design.