On contrast of biological X-ray nanomicroscopy

We analyse the absorption contrast of histological and cytological preparations, which can be achieved in nanomicroscopic studies using monochromatic radiation in the spectral range of 90 – 600 eV (14 – 2 nm). Two types of unstained biological objects are considered: untreated and fixed in paraffin, and optimum wavelengths are determined for the study of samples with a thickness of 0.5 – 10 μm with a spatial resolution of 100 – 20 nm. Taking into account the efficiency of X-ray optics, the number of source photons required to produce a single image is estimated. It is shown that the greatest interest for the study of fixed objects represents the spectral region of 7 – 14 nm, for which, on the basis of rapidly developing compact sources of incoherent and coherent radiation and effective optics, microscopes for scientific and clinical research can be designed. (paper)