Design of soft X-ray wide-band multilayer gratings for constant deviation monochromators

Koike, Masato; Imazono, Takashi

Soft X-ray multilayer has a potential to improve diffraction efficiency of diffraction gratings in the multi-kilo electron volts region. However, to use a conventional multilayer grating at the maximum diffraction efficiency, the incidence and diffraction angles should be varied with photon energy. Recently we developed a wide-band laminar-type multilayer grating for the flat-field spectrograph used in the energy range of 2-4 keV. The structure of the multilayer consists of two regions of massive and few periods having short and long period lengths, respectively, to widen the bandwidth. This method worked successfully that a diffraction efficiency of 1-2 % was obtained experimentally. Another interest on this method is the application to the monochromators. In this paper, we design the diffraction efficiency of the multilayer laminar-type grating covering 1.5-2.5 keV and estimate the throughput of a Monk-Gillieson type monochromator employing this grating.