Swift Solar Activity X-ray Image (SSAXI-Rocket), mounted on the High-Resolution Coronal Imager (Hi-C) as a sub-payload, is a wide field solar X-ray imager designed to image Solar X-ray flares at high cadence (>5 Hz). SSAXI-Rocket consists of a Wolter-I optic with a focal length of 1 m, coupled with a monolithic CMOS X-ray sensor at the focal plane. The optics for SSAXI-Rocket were fabricated using the Electroformed Ni Replication (ENR) technique at Center for Astrophysics, Harvard-Smithsonian. Each optic has both parabolic and hyperbolic sections with 62 mm diameter at the inflection plane with a total optic length of 18 cm. The performance of the flight and flight spare optic mounted on a spider was measured at the Marshall Space Flight Center (MSFC) Stray Light Testing Facility (SLTF) to characterize the Point Spread Function (PSF) and Effective Area (EA). The flight optic selected for SSAXI-Rocket shows on-axis 16′′ Half Power Diameter (HPD) and 5′′ Full Width Half Maximum (FWHM) at 4.5 keV, exceeding the 23′′ HPD and 9′′ FWHM requirement. The effective area is about 0.64 cm2 at 4.5 keV. Coupled with the fast readout of an X-ray CMOS sensor, this optic enables rapid high-resolution X-ray imaging over a wide field of view (> 20′ x 20′). Here we review the design, fabrication and testing of the SSAXI-Rocket optic and summarize its performance.
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.
Electroforming replication technology at Marshall Space Flight Center has a long heritage of producing high-quality full-shell x-ray mirrors for various applications. Nickel alloys are electroformed onto a super-polished mandrel in the electroforming process, then separated to form the replicated full-shell optic. Various parameters in the electroplating configuration could result in the nonuniformity of the shell’s thickness. Thickness non-uniformities primarily occur due to non-uniform electric field distributions in the electroforming tank during the deposition. Using COMSOL Multiphysics simulations, we have studied the electric field distributions during the deposition process. Using these studies, we have optimized the electric fields inside the tank using customized shields and insulating gaskets on the mandrel. These efforts reduced thickness non-uniformity from over 20% to under 5% percent. Improving the thickness uniformity of the shell aids in better mounting and alignment of shells in the optics module. Optimization of the electroforming process, in some cases, improved the optical performance of the shells. COMSOL optimizing of the electroforming process and the experimental results validating these simulations are presented in this article.
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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