EUV Properties Of Two Diffraction Gratings

We have obtained two mechanically ruled replica gratings from Hyperfine Inc. and one holographically ion-etched grating from Ferranti Astron, Ltd. The gratings, made on spheroid cervit blank, are 86.3 x 86.3 x 12mm and have a groove density of 1710 grooves per mm with a platinum overcoating. The grating manufacturers were given identical specifications (size, groove density reflective coating, etc.). Both gratings were blazed to reflect into the first inside order for a wavelength of ≈ 700 Å. We have evaluated the two gratings at the extreme ultraviolet (EUV) calibration facility at the University of California, Berkeley, Space Sciences Laboratory to determine the suitability for adoption in an EUV spectrometer, the primary instrument of the Remote Atmospheric and Ionospheric Detection System (RAIDS) to be flown aboard a TIROS satellite in 1991. The grating efficiency was measured at five EUV wavelengths using a pencil beam at five positions on the grating. Our measurements show that the efficiencies of the mechanically ruled grating were higher than the holographically ruled grating for the operating order. However, the efficiencies of the holographic grating into the other orders were unexpectedly higher than the ruled ones. The holographically ruled grating displayed about an order of magnitude less scattered light than the mechanically ruled grating.