Development of a flat-field spectrograph with a Ni/C multilayer grating covering the range 1-3.5 keV at a fixed incident angle

Imazono, Takashi

no journal, , 

A flat-field spectrograph equipped with an aperiodic Ni/C multilayer grating with coverage of the 1-3.5 keV range at a fixed incident angle has been developed. The multilayer coating consists of two kinds of 5.6 nm thick bilayers. One is a conventional Ni/C multilayer having the ratio of Ni thickness to the period of 0.5 and the number of layers of 79. The topmost layer is carbon. The other is a single C/Ni bilayer of Ni thickness ratio of 0.8, which means the deposition order is reversed. Consequently, the C layer just under the topmost Ni layer is a continuous layer of 3.92 nm thickness. The aperiodic multilayer was coated on a laminar grating having a grating constant of 1/2400 mm, groove depth of 2.8 nm, and duty ratio of 0.5. The diffraction efficiency of the multilayer grating varies from 0.8% to 5.4% in 2.1-3.3 keV, and is significantly improved up to 7, 4470 and 102 times higher at 2.1 keV, 2.3 keV and 3.0 keV, respectively, than that of before multilayer deposition.