Computer-Controlled Fabrication of Concentric Multilayer Fresnel Zone Plate for Synchrotron Radiation Hard X-Ray
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COMPUTER-CONTROLLED FABRICATION OF CONCENTRIC MULTILAYER FRESNEL ZONE PLATE FOR SYNCHROTRON RADIATION HARD X-RAY
Masato Yasumoto1,4, Shigeharu Tamura2,4, Nagao Kamijo3,4, Yoshio Suzuki4, Mitsuhiro Awaji4, Akihisa Takeuchi4, Hidekazu Takano4, Yoshiki Kohmura5, Katsumi Handa6 1 Photonics Research Institute, AIST, AIST Tsukuba Central2, Tsukuba 305-8568 Japan 2 Photonics Research Institute, AIST, AIST Kansai, Ikeda Osaka 563-8577 Japan 3 Kansai Medical University, Uyama-higashi, Hirakata, Osaka, 573-1136, Japan 4 Japan Synchrotron Radiation Research Institute (SPring-8), Mikazuki-cho, Hyogo, 679-5198, Japan 5 RIKEN Harima Institute (SPring-8), Mikazuki-cho, Hyogo, 679-5198, Japan 6 Ritsumeikan University, Noji-higashi, Kusatsu, Shiga, 525-8577, Japan
ABSTRACT A Fresnel zone plate (FZP) is a micro-focusing optical element of synchrotron radiation hard X-ray. Our developed multilayer FZP produced a sub-micron size spot at the hard X-ray energy and the focusing efficiency is about 25%. However the higher efficiency FZP is required to utilize the sub-micron probe in microscopy, diffraction and imaging applications. A kinoform FZP composed of gradient refractive index phase zones has the advantage of a high focusing efficiency compared to the conventional multilayer FZP. In order to fabricate the kinoform FZP, we developed a computer-control system. The developed computer-control system automatically operates whole combinatorial deposition processes of the kinoform FZP by inputting the optical parameters of the FZP (focal length, X-ray wavelength, number of zones, zone materials).
INTRODUCTION A zone plate (ZP) plays a key role in an optical element for focusing the X-ray synchrotron radiation (SR). The zone plate is alternatively composed of an opaque zone and a transparent zone for the X-ray. Each zone is spaced in such a way that constructive interference concentrically occurs at the focal point. The ZP for soft X-ray SR has been developed by an electron beam lithography method and already provided for microscopy beamlines [1,2]. A high spatial resolution X-ray microscope using the ZP clearly resolved a pattern with a half period of 25nm at an X-ray energy of 250 through 900 eV [3]. However, the ZP made by the electron beam lithography method is difficult to extend to X-ray energies of above 8 keV because of the high aspect ratio of a transparent zone and an opaque zone of the ZP required. In order to focus above 8 keV X-ray SR, a thick (high aspect ratio) ZP has been fabricated using a sputtered-sliced method [4,5]. We have fabricated a concentric multilayer Fresnel zone plate (FZP) with S5.4.1
the sputtered-sliced method [6]. Our multilayer FZP is alternately composed of an Al zone and a Cu zone for the transparent zone and the opaque zone, respectively. Using our recently developed FZP, we found the focal beam size to be about 0.6µm at an X-ray energy of 8.86keV[7,8,9]. Moreover, we plan to make a multilevel FZP with a gradient refractive index phase multilayer by the sputtered-sliced method. The multilevel FZP h
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