What's it about?

The next generation of x-ray synchrotron systems require increasingly precise mirrors to enable diffraction limited focusing of x-ray beams. Due to the extremely short wavelength of the x-ray radiation, coated silicon mirrors must be used at grazing incidence to focus the x-ray beams. These mirrors need to be polished to nanometer level form error and are particularly susceptible to surface texture, including mid-spatial frequency (MSF) errors and surface roughness. Recognizing a gap in domestic production capability for this need, the United States Department of Energy funded Small Business Innovation Research contracts to improve US domestic manufacturing capabilities of these ultra-precision silicon mirrors.

This presentation will discuss efforts at Optimax to address this need through advancement of robotic smoothing platforms and processes. Flat test parts were ground then had a mirror surface fabricated through single point diamond turning (SPDT). The SPDT process leaves behind characteristic signatures in the surface texture which are detrimental to short wavelength applications. These parts were then smoothed using Optimax’s robotic smoothing platform to eliminate the SPDT signature. Multiple pad and slurry compositions were investigated to determine the optimal choice for each step in the process chain. Significant reduction in the MSF content was achieved, as well as sub- 0.3 nm rms surface roughness, meeting the specifications set out in the project solicitation. Ongoing work is being performed to improve the performance of the robotic smoothing process to address form error.