NASA / MSFC has made new full-shell NiCo replicated hard X-ray optics
for the fourth flight of the Focusing Optics X-ray Solar Imager
sounding rocket set to observe the sun in March 2023. The new FOXSI-4
high resolution optics were made using enhanced
mandrel polishing techniques incorporating a Zeeko CNC deterministic
polishing machine and an improved module assembly station with in-situ metrology.
FOXSI-4 will fly three new 2-meter focal length high
resolution mirror modules with two shells each. The previous FOXSI-3
optics achieved an angular resolution of 20 arcsec HPD (5 arcsec FWHM) for
ten-shell modules. Initial X-ray measurements of FOXSI-4 shells
before module integration show a performance of 8 arcsec HPD and 3
arcsec FWHM, a substantial improvement over the FOXSI-3 optics. We present the
advances made in the polishing, replication, and assembly processes, and
measurements of the performance of the completed modules taken in the
Marshall 100 meter X-ray beam line.
Technology for a large-area, high-angular resolution mirror module for a future Great Observatory x-ray mission is progressing along different paths. To date, none of these are fully developed. Work at the Marshall Space Flight Center (MSFC) seeks to leverage the benefits of full shell optics while exploring the limits of using shell replication technology for optics production. Here, we provide an updated accounting of spatial-resolution-constraining error terms to give context to recent improvements in MSFC replicated optics, as well as guidance and justification for current and future directions of research and development. Content includes straw-man error allocations for an optical system that is parametrically Lynx-like, where the replicated-optics technology stands relative to these allocations, and methodology for mapping development plans to efficiently identify the limiting factors, and approaches to overcoming these.
NiC multilayers have been identified as a promising coating design for hard x-ray astrophysical imaging applications enabling bandpass extension beyond the Pt K-edge of approximately 78 keV. However, these coatings are difficult to deposit with low interfacial roughness below a bilayer thickness of about 35 Å. Utilizing a DC magnetron sputtering system, NiC multilayer of varying d-spacings are deposited on flat Si wafers and characterized using 8.048 keV x-ray reflectometry measurements. The residual coating stress is also measured using interferometry. We investigate how deposition parameters affect both the coating quality (i.e. surface/interfacial roughness, density, etc.) and the residual coating stress. From these experimental results conducted on flat substrates, we employ FEM and ray trace simulations to determine how NiC multilayer stress could impact the figure, and therefore performance, of full shell x-ray optics.
The Marshall 100-Meter x-ray Beamline is a user facility for x-ray and EUV optics and instrumentation calibration, located at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Also known as the Stray Light Test Facility, the Marshall-100 provides a range of focal plane detectors, x-ray sources, translation stages, cleanrooms, and high-vacuum level capability to the high-energy astrophysics community. Facility time is made available to Astronomy and Physics Research and Analysis (APRA) funded projects and is also available to the broader community upon request made to beamline management. The beamline has successfully been employed in the calibration of larger scope projects such as the Spectrum-Roentgen-Gamma Astronomical Röentgen Telescope X-ray Concentrator (ART-XC) telescope and the Small Explorer (SMEX) class Imaging X-ray Polarimetry Explorer (IXPE) Space Telescope. Additionally, the Marshall-100 is instrumental in supporting testing related to MSFC’s high-angular resolution optics development program.
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