MODERN MICROSYSTEMS, INC. — Department of Energy SBIR Phase II: 05b

Description

Modern synchrotron x-ray sources provide a useful photon brilliance in excess of 1018 photons⁄s⁄0.1%BW⁄mrad2⁄mm, but they also deposit power densities on the order of 100 W⁄mm2 on the beamline optics. X-ray optics are required that provide the greatest possible focusing power while managing the associated heat flux. The exceptional x-ray optical properties and extreme thermal conductivity of diamond make it an ideal material for synchrotron optics. Diamond kinoform optics are predicted to improve transmission as compared to solid beryllium refractive optics and as compared to silicon kinoform optics in a broad spectrum of photon energies, opening up a wider range of applications. In Phase 1 and 2, Modern Microsystems developed and refined a fabrication process for high- aspect-ratio monocrystalline diamond kinoform refractive optics suitable for use in synchrotron hard x-ray beamlines. The process utilizes a proprietary diamond deep reactive ion etching process with advanced plasma capabilities and advanced hardmask materials to imprint into diamond substrates patterns having micron-scale critical dimensions. In Phase 2B, we propose to introduce fault-tolerant design, post-process dimensional trimming, and post-process sidewall polishing to yield optics with the precision required for even the most demanding applications. The optics are expected to outperform their solid beryllium counterparts over the photon energy range from 2 keV past 50 keV and beyond, with focal depths ranging from 10 m down to 10 cm, and focal spots down to 100 nm or better. Fault-tolerant design and post-process trimming will mitigate non-idealities observed on the most aggressive designs attempted during Phase 2. Specifically, kinoform optics that were exceptionally deep exhibited sidewall verticality near 0.5°. Such small deviations are sufficient to change the degrade the resolution of the optic and to limit the depth, resulting in lower resolution and aperture than is theoretically possible. By designing with an expectation of this type of deviation, by correcting the deviation after the optic has been fabricated, and by polishing the sidewalls of the optics after fabrication, we can produce optics that exhibit performance very close to their theoretically determined capabilities. We will use these advanced design, trimming, and polishing techniques to fabricate diamond kinoform x-ray optics with capabilities not previously achieved, in a variety of configurations representative of the diverse requirements of the synchrotron research community. The chief benefit of the proposed work is to upgrade the focusing power of today’s most advanced x-ray sources, while reducing cost and eliminating the health and environmental risks associated with existing beryllium optics.