Enhancement of diffraction efficiency of laminar-type diffraction gratings overcoated with diamond-like-carbon (DLC) in soft X-ray region

Koike, Masato; Imazono, Takashi; Nagano, Tetsuya*; Sasai, Hiroyuki*; Oue, Yuki*; Yonezawa, Zeno*; Kuramoto, Satoshi*; Terauchi, Masami*; Takahashi, Hideyuki*; Notoya, Satoshi*; Murano, Takanori*

Born is a trace element to improve quenching characteristics in steel. In order to detect the B-K emission band at around 6.76 nm more efficiently, we performed a feasibility study to enhance the diffraction efficiency of laminar-type diffraction grating based on a newly discovered physical phenomenon in the region of total reflection. The phenomenon is embodied as a transparent high-density material layer overcoated on a metal layer on grating grooves. The material should have intermediate diffractive index of vacuum and the metal layer. We found that high density diamond-like-carbon (DLC) is a one of the best material and simulated the diffraction efficiency in a spectral region of 3.58.5 nm. The optimum thickness and density of DLC are 24 nm and 3.1 g/cm, respectively, for an incidence angle of 87. Then the first order diffraction efficiency is expected to achieve up to 29.7 %, which is improved from 15.6 % for Ni or 14.1 % for Au, at 6.76 nm.