Project of Scanning and Projection Microscopes for the Nanoscopy Station for Biological Research in the “Water Transparency Window”

A brief description of the concept of a soft X-ray microscope for the Nanoscopy station is given, which is planned to be installed at the SKIF fourth-generation synchrotron. The microscope will be designed to study the structure of cells and dynamic processes in them with nanometer spatial resolution. It will use a unique absorption contrast of ~15 between carbon-containing structures and water in the spectral range of the “water transparency window”, λ = 2.3–4.3 nm, which eliminates the need for contrasting and the use of fluorophores and minimizes the doses of ionizing radiation absorbed in the samples to obtain high-quality 3D-images. The scanning and projection schemes of the microscope, their main technical characteristics, including the calculated spectra and parameters of the undulator source are presented, and an estimate of the absorbed doses depending on the resolution is obtained. The main advantage of the proposed concept lies in the use of an objective of high-aperture multilayer X-ray mirrors, which makes it possible to clearly visualize the focal section of the sample. Technically simple axial tomography will also be used to reconstruct the three-dimensional structure of frozen or dried samples. In the scanning scheme, due to the low dose of radiation, it will be possible to study living plant cells with a resolution of up to 10 nm, animals with a resolution of up to 80 nm, and cryofixed samples with a resolution of up to 5 nm. In the projection scheme, due to the simultaneous observation of the entire focal XY-section, the time for obtaining three-dimensional images is significantly reduced, but due to the large dose, it will be oriented mainly on the study of fixed samples.