Development of a soft X-ray flat-field spectrograph in the 50-4000 eV range and its application to electron microscopies

Imazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru*; Nagano, Tetsuya*; Sasai, Hiroyuki*; Oue, Yuki*; Yonezawa, Zeno*; Kuramoto, Satoshi*; Terauchi, Masami*; Takahashi, Hideyuki*; Handa, Nobuo*; Murano, Takanori*

A soft X-ray flat-field spectrograph in combination with electron microscopes is one of the powerful tools for not only the structural and elemental analyses, but also the valence band analysis of materials. It is expected to be able to detect soft X-ray emissions of 50-4000 eV emitted from various materials, but difficult to cover the whole energy range using a single diffraction grating by restriction of optical imaging property and surface material. To overcome this problem, a flat-field spectrograph compatible with four varied-line-spacing gratings optimized for the respective energy range of 50-200 eV, 155-350 eV, 300-2200 eV, and 2000-4000 eV has been designed. It results in that the spectrograph can be easily selected without complicated optical alignment by just changing the desired grating of the four. In addition, a multilayer mirror to enhance uniformly a reflectivity in 2-4 keV at a constant angle of incidence was invented and applied to a wideband multilayer grating.