Electroforming replication technology at the 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 and then separated to form the replicated full-shell optic. Various parameters in the electroplating configuration could result in the non-uniformity of the shell’s thickness. Thickness non-uniformities primarily occur due to the non-uniform electric field distribution in the electroforming tank during deposition. Using COMSOL Multiphysics simulations, we studied the electric field distributions during the deposition process. Using these studies, we optimized the electric field distribution and strength inside the tank using customized shields and insulating gaskets on the mandrel. These efforts reduced the thickness non-uniformity from over 20% to under 5%. Improving the thickness uniformity of the shell aids in better mounting and aligning shells in the optics module. Optimization of the electroforming process, in some cases, improved the optical performance of the shells. Using finite element modeling, we estimated the effect of electroforming stress on the figure errors of the replicated optics. We observed that the electroforming stress predominantly affects the figure toward the ends of the optics. We presented COMSOL optimization of the electroforming process and the experimental results validating these simulations. We also discuss modeling experimental results of the replication figure errors due to electroforming stresses.
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.
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