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2929 |
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Fabrication of Pt/C Multilayer-Coated Thin Foil Mirrors for Hard X-Ray Telescope Loaded in ASTRO-H Satellite |
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Applications of Precision Engineering in Manufacturing |
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In future satellite missions for X-ray astronomy, hard X-ray imaging will become one of the major observation techniques. It allows astronomers to observe the distribution of hard X-ray objects in the Universe with a high sensitivity. Since hard X-rays can penetrate thick absorbing materials, astronomers are able to discover many massive black holes embedded in thick gas. High-energy phenomena are well studied in hard X-rays, which are essentially produced by accelerated high-energy particles in the universe. The sixth Japanese X-ray astronomy satellite ASTRO-H to be launched in 2013 is expected to provide the first opportunity to perform hard X-ray imaging observations with a supermirror hard X-ray telescope. Similar hard X-ray imaging systems have also been proposed for use in other programs, such as the Italian-French mission Symbol-X (planned for 2014), the European Space Agency (ESA)-Japan X-ray observatory mission XEUS and the future NASA mission Constellation-X. They are now merged into the International X-ray Observatory IXO to be launched in 2020. A hard X-ray telescope is included in the list of instruments to be onboard IXO.
Next-generation hard X-ray telescopes require highly nested aspherical thin mirrors of 100 nm shape accuracy and less than 0.3 nm rms surface roughness. These telescopes are constructed using nested multiple grazing incidence reflecting mirrors consisting of a paraboloid and hyperboloid of revolution. Over two hundred Pt/C multilayer-coated mirrors of different sizes are required. Thin mirror substrates or shells are fabricated by replication from molding dies of high precision. Thus, a machining apparatus that enables the accurate and rapid machining of large aspherical molding dies is necessary, and the shapes of such large molding dies should be measured on the machining apparatus during machining to ensure shape accuracy.
In this paper, we describe a large ultra-precision single-point diamond turning, polishing and measuring machine for fabricating aspherical molding dies of high precision, which can be applied to next-generation hard X-ray telescope mirrors. We also describe the Pt/C coated thin foil mirrors replicated from the aspherical molding dies.
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