Development of the Water Window Imaging X-Ray Microscope

Imaging x-ray microscopes currently under development at the Marshall Space Flight Center utilize multilayer x-ray/EUV optical systems and structural components similar to those developed for normal incidence imaging solar x-ray telescopes. The Water Window Imaging X-Ray Microscope is specifically designed to operate at x-ray wavelengths within the `water window' regime, wherein water is relatively transmissive and carbon is highly absorptive. This important natural property of the interaction of x-rays with matter should permit this microscope to sharply delineate carbon based structures within living cells. The ability to image living cells in aqueous physiological environments, with high spatial resolution and high contrast, may afford advantages not available with conventional microscopes and make possible non-invasive strategies for examining living tumor cells without the need of stains or exogeneous chemicals that can produce limiting artifacts. The Water Window Imaging X-Ray Microscope represents a `spinoff' of multilayer x-ray telescope technology. This paper reviews the multilayer x-ray telescope developments which led to this x-ray microscope research. It considers the design, fabrication, optical assembly, alignment, and testing of the prototype microscopes and provides the results of recent studies of ultrahigh resolution photographic films and the design of high reflectivity multilayer coatings for applications in the water window.