Abstract: The authors have theoretically designed and analyzed the optical components and mechanical structures for an imaging x-ray microscope which will be configured to operate in the water window. This instrument affords new and noninvasive strategies for examining living tumor cells without the use of dyes, stains or other exogenous chemicals, which can produce limiting artifacts. The Water Window Imaging X-Ray Microscope is based on doubly reflecting, normal incidence multilayer optical technology, such as has been previously employed in telescopes for high resolution x-ray imaging of the sun. Multilayer coatings have now been fabricated with near theoretical reflectivities and perfect bandpass matching for the new rocket-borne solar observatory, the Multi-Spectral Solar Telescope Array (MSSTA). These telescopes employ multilayer mirror substrates with sub-angstrom (rms) smoothness which are made possible by Advanced Flow Polishing. Recent developments in multilayer coating technology and Advanced Flow Polishing methods used with Zerodur and Hemlite grade sapphire have paved the way for the development of the Water Window Imaging X-Ray Microscope. In this narrow water window wavelength regime of the x-ray spectrum, which lies between the K absorption edges of oxygen (23.3 angstroms @) and of carbon (43.62 angstroms @), water is relatively highly transmissive and carbon is highly absorptive. This principle allows the Water Window Imaging X-Ray Microscope to delineate, with high resolution and high contrast, carbon-based structures in the aqueous physiological environments found within living cells. The theoretical design and analysis of the microscope optical and mechanical components are described and the fabrication effort underway for the development of this new optical instrument, which should improve diagnosis and greatly benefit experimental studies of tumor cell biology, is discussed.!
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