[P-CG20] Future missions and instrumentation for space and planetary science

[PCG20-14] Development of ultra-lightweight X-ray telescopes fabricated with MEMS technologies for GEO-X

*Masaki Numazawa¹, Yuichiro Ezoe¹, Kumi Ishikawa¹, Daiki Ishi², Hiromi Morishita¹, Yukine Tsuji¹, Luna Sekiguchi¹, Takatoshi Murakawa¹, Yudai Yamada¹, Daiki Morimoto¹, Rei Ishikawa¹, Aoi Ishimure¹, Shunei Miyauchi¹, Yuto Ogasawara¹, Hiroshi Nakajima³, Yuki Satoh³, Ikuyuki Mitsuishi⁴, Yoshiaki Kanamori⁵, Kohei Morishita⁶, Kazuhisa Mitsuda⁷ (1.Tokyo Metropolitan University , 2.Japan Aerospace Exploration Agency, 3.Kanto Gakuin University, 4.Nagoya University, 5.Tohoku University, 6.Kyushu University, 7.National Astronomical Observatory of Japan)

Keywords:X-ray micropore optics, Small satellite, Solar wind charge exchange, Earth's magnetosphere

We have been developing ultra-lightweight Wolter type-I X-ray telescopes fabricated with MEMS technologies for GEO-X (GEOspace X-ray imager) which is a small satellite mission to perform soft X-ray imaging spectroscopy of the entire Earth's magnetosphere. The telescope is our original type of micropore optics and possesses lightness (~5 g), a short focal length (~250 mm), and a wide field of view (~5 deg x 5 deg). The MEMS X-ray telescope is made of 4-inch Si (111) wafers. The Si wafer is firstly processed by deep reactive ion etching such that they have numerous curvilinear micropores (20-micrometer width) whose sidewalls are utilized as X-ray reflective mirrors. High-temperature hydrogen annealing and chemical mechanical polishing processes are applied to make those sidewalls smooth and flat enough to reflect X-rays. After that, the wafer is plastic-deformed into a spherical shape and Pt-coated by a plasma atomic layer deposition process to focus X-rays with high reflectivity. Finally, we assemble two optics bent with different curvatures (1000- and 333-mm radius) and complete the Wolter type-I telescope. We optimized each process to enable the optics to achieve an angular resolution of ~5.4 arcmins in half power width in a part of the mirror (~10 arcmins in half power diameter in the entire telescope, required for GEO-X) from the reflective surface figures and the whole wafer shapes. We are conducting an X-ray irradiation test to assemble the full-processed optics into an engineering model (EM) telescope for GEO-X and evaluate its performance. We also fabricated a structural thermal model (STM) telescope and verified its environmental tolerances by conducting a vibration test, a proton/heavy-ion radiation test, and a thermal-cycle test. We report on our latest development status as the X-ray imaging performance of the GEO-X EM telescope and the results of the environmental tests of the STM telescope.