Development of the water window imaging x-ray microscope utilizing normal incidence multilayer optics

Abstract

We describe the development of the water window imaging x-ray microscope based on normal-incidence multilayer x-ray mirrors. The narrow bandpass response inherent in multilayer x-ray optics is accurately tuned to wavelengths within the "water window." Similar doubly-reflecting multilayer optical systems have been fabricated for our astronomical rocket-borne x-ray/EUV telescopes. Previous theoretical studies performed during the MSFC X-Ray Microscope Development Program established that high-resolution multilayer x-ray imaging microscopes are possible by using either spherical (Schwarzschild configuration) optics or aspherical configu rations. These microscopes require ultrasmooth mirror substrates, which have been fabricated using advanced flow polishing methods. Hemlite-grade sapphire microscope optic substrates have been accurately figured and polished to a smoothness of 0.5-Å rms, as measured by the Zygo profilometer. We describe the current status of fabrication and testing of the optical and mechanical subsystems for the water window imaging x-ray microscope. This new instrument should yield images of carbon-based microstructures within living cells of unprecedented spatial resolution and contrast, without need for fixatives, dyes, and chemical additives.