Development of soft X-ray multilayer laminar-type plane gratings and VLS spherical grating for flat-field spectrograph in the 1-8 keV region

Koike, Masato; Ishino, Masahiko; Imazono, Takashi; Sano, Kazuo*; Sasai, Hiroyuki*; Hatayama, Masatoshi*; Takenaka, Hisataka*; Heimann, P. A.*; Gullikson, E. M.*

A multilayer laminar-type holographic grating having an average groove density of 2400 lines/mm was designed and fabricated for use with a soft X-ray flat field spectrograph covering the 0.70-0.75 nm region. A varied-line-spacing grooves pattern is generated by the use of an aspheric wavefront recording system and laminar-type grooves are formed by a reactive ion-etching method. Mo/SiO multilayers optimized for the emission bands of hafnium M, silicon K, and tungsten M are deposited on one of the three designated areas on the grating surface in tandem. The measured first-order diffraction efficiencies at the respective centers of the areas are 18-20 percent. A flat field spectrograph equipped with the grating indicates a spectral line width of 8-14 eV for the emission spectra generated from an electron-impact X-ray sources.