High efficiency diffraction gratings for study of trace boron by soft-X-ray emission spectroscopy

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

When the grazing incidence angle is 3.0, the total reflection condition is satisfied but the reflectivity is 74% due to the large extinction coefficient of 8.410. Carbon has a large critical angle of carbon of and small extinction coefficient of 7.610. We take these advantages to the coating of diffraction gratings. We assume the base laminar-type grating as follows: nickel layer of 30 nm thickness; groove density of 1200/ mm; duty ratio of 0.3; groove depth of 16 nm. Also it is assumed that the additions of conventional amorphous carbon having a density of 2.2 g/cm and diamond-like carbon(ta-C) having 3.1 g/cm. Optimized thickness of a-C and ta-C is 12 and 24 nm, respectively. The increase of 33% 183.3 eV (a-C) and 80% (ta-C) is obtained compared with the base grating, respectively, resulting in high sensitivity measurement of ultra-trace boron K emission.