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

W/C and Co/SiO2 multilayer laminar-type holographic plane gratings (groove density 1/σ = 1200 lines/mm) in the 1-8 keV region are developed. For the Co/SiO2 grating the diffraction efficiencies of 0.41 and 0.47 at 4 and 6 keV, respectively, and for the W/C grating 0.38 at 8 keV are observed. Taking advantage of the outstanding high diffraction efficiencies into practical soft X-ray spectrographs a Mo/SiO2 multilayer varied-line-spacing (VLS) laminar-type spherical grating (1/σ = 2400 lines/mm) is also developed for use with a flat field spectrograph in the region of 1.7 keV. For the Mo/SiO2 multilayer grating the diffraction efficiencies of 0.05-0.20 at 0.9-1.8 keV are observed. The FWHMs of the measured line profiles of Hf-Mα1(1644.6 eV), Si-Kα1(1740.0 eV), and W-Mα1 (1775.4 eV) are 13.7 eV, 8.0 eV, and 8.7 eV, respectively.