Fabrication and Evaluation of Holographically Varied Line-Spacing Gratings for Soft-X-Ray Flat Field spectrographs

摘要

Recent progress in the desing of aspheric wave-front recording systems has enabled the manufacture of holographic gratings with strongly varied groove densities suitable for soft X-ray flat field spectrographs. A holgraphic grating thus recorded was processed to produce a laminar profile by reactive ion-etching. Measurements are reported here of the absolute diffraction efficiency of this grating and of a comparable mechanically ruled grating using a synchrotron radiation. It is found that the holographic grating is effective at suppressing the higher orders. The spectral resoltuion was determined using a Carbon K#alpha# X-ray generator and a spectrograph with an imaging detector. the spectral resolution of the holographic grating was about three tiems worse than that of the ruled grating.