X-ray microscopy is a well-established technique for nanoscale imaging. Zone plates are used as microscope objectives and provide high resolution, approaching 10 nm, currently limited by fabrication issues. This Thesis presents zone plate optics that achieve either high resolution or phase contrast in x-ray microscopy. The high-resolution optics use high orders of the zone plate, which alleviates the demands on fabrication, and the phase-contrast optics are single-element diffractive optical elements that produce contrast by Zernike or differential-interference contrast methods. The advantage of phase contrast in x-ray microscopy is shorter exposure times, and is crucial in the hard x-ray regime. Microscopy in the absorption‑contrast region of the water-window (2.34 - 4.37 nm) also benefits from these optics. The development of the optics for a laboratory soft x-ray microscope spans from theoretical and numerical analysis of coherence and stray light to experimental implementation and testing. The laboratory microscope uses laser-produced plasma-sources in the water-window and is unique in its design and performance. It will be shown that the laboratory microscope in its current form is a user-oriented and stable instrument, and has been used in a number of applications. The implementation of a cryogenic sample stage for tomographic imaging of biological samples in their natural environment has enabled applications in biology, and 3D x-ray microscopy of cells was performed for the first time with a laboratory instrument. / QC 20101130

Soft x-ray microscopy in the water-window (λ = 2.28 nm – 4.36 nm) is based on zone-plate optics and allows high-resolution imaging of, e.g., cells and soils in their natural or near-natural environment. Three-dimensional imaging is provided via tomographic techniques, soft x-ray cryo tomography. However, soft x-ray microscopes with such capabilities have been based on large-scale synchrotron x‑ray facilities, thereby limiting their accessibility for a wider scientific community. This Thesis describes the development of the Stockholm laboratory soft x-ray microscope to three-dimensional cryo tomography and to new optics-based contrast mechanisms. The microscope relies on a methanol or nitrogen liquid-jet laser-plasma source, normal-incidence multilayer or zone-plate condenser optics, in-house fabricated zone-plate objectives, and allows operation at two wavelengths in the water-window, λ = 2.48 nm and λ = 2.48 nm. With the implementation of a new state-of-the-art normal-incidence multilayer condenser for operation at λ = 2.48 nm and a tiltable cryogenic sample stage the microscope now allows imaging of dry, wet or cryo-fixed samples. This arrangement was used for the first demonstration of laboratory soft x-ray cryo microscopy and tomography. The performance of the microscope has been demonstrated in a number of experiments described in this Thesis, including, tomographic imaging with a resolution of 140 nm, cryo microscopy and tomography of various cells and parasites, and for studies of aqueous soils and clays. The Thesis also describes the development and implementation of single-element differential-interference and Zernike phase-contrast zone-plate objectives. The enhanced contrast provided by these optics reduce exposure times or lowers the dose in samples and are of major importance for harder x-ray microscopy. The implementation of a high-resolution 50 nm compound zone-plate objective for sub-25-nm resolution imaging is also described. All experiments are supported by extensive numerical modelling for improved understanding of partially coherent image formation and stray light in soft x-ray microscopes. The models are useful tools for studying effects of zone plate optics or optical design of the microscope on image formation and quantitative accuracy in soft x-ray tomography. / QC 20110221