Development of an objective flat-field spectrograph for electron microscopic soft X-ray emission spectrometry in 50-4000 eV

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*

We have developed an objective soft X-ray flat-field spectrograph to be able to attach to electron microscopes. This spectrograph has two attractive features. One is that it is designed to cover a wide energy range of 50-4000 eV by using four varied-line-spacing holographic gratings optimized for 50-200 eV, 155-350 eV, 300-2200 eV, and 2000-4000 eV. They can be accommodated in the single spectrograph. The other is a newly invented W/BC multilayer coating covering the 2000-4000 eV range. It can enhance the diffraction efficiency above a practical level of % at a constant incidence angle in the whole energy range.