Extreme ultraviolet performance of a multilayer coated high density toroidal grating

Abstract

The performance of a multilayer coated diffraction grating has been evaluated at EUV wavelengths both in terms of absolute efficiency and spectral resolution. The application of a ten-layer Ir/Si multilayer coating to a 3600-lines/mm blazed toroidal replica grating produced a factor of 9 enhancement in peak efficiency near the design wavelength approximately 30 nm in first order, without degrading its excellent quasistigmatic spectral resolution. The measured EUV efficiency peaked at 3.3% and was improved over the full spectral range between 25 and 35 nm compared with the premultilayer replica which had a standard gold coating. In addition, the grating's spectral resolution of >5000 was maintained.

An EUV imaging spectrograph for high-resolution observations of the solar corona

“…The present design has been optimized for the 235 A to 450 A spectral range using a mechanically ruled tripartite grating with 3600 grooves mm-1 produced by Hyperfine, Inc. Grating parameters and design characteristics of the spectrograph are given in Table II. Evaluation of grating reflectivity at EUV wavelengths is discussed by Thomas et al (1991). The short wavelength limit was based on a desire to include a density-sensitive couplet of FeIx emission lines at 242 A. and 245 A (Feldman, Doschek, and Widing, 1978;Hang, 1979), recognizing that the rapid decrease in grating reflectivity below 300 A would make tong exposures necessary for these lines (which would not have been a problem in a long-duration Space Shuttle mission).…”

“…The reflectivity of the grating was measured using the SURF II facility at the National Institute of Standards and Technology (NIST) (Thomas et al, 1991). For that measurement, the grating was set up in a Wadsworth mount configuration and the diffracted synchrotron radiation measured as function of wavelength with a previously calibrated anodized evaporated aluminium photodiode (Canfield, Johnston, and Madden, 1973).…”

Five Solar Cycles of Solar Corona Investigations

“…The flare scenario that emerged during the first year of analysis was substantially confirmed by analyzing the large set of X and M flares detected in 1980 (Antonucci, Gabriel, and Dennis, 1984;Antonucci et al, 1985b). The complementary information -on the volume of the soft-X-ray source (3.5 -8 keV) in the corona inferred from the Hard X-ray Imaging Spectrometer (HXIS) (Van Beek et al, 1980), on the energy released above 25 keV deduced from the Hard X-Ray Burst Spectrometer (HXRBS) (Orwig, Frost, and Bennis, 1980), and, in a few cases, on the loop footpoint geometry identified in the images of the hard-X-ray channel of the HXIS images, 16 -30 keV (Hoyng et al, 1981;Antonucci, Marocchi, and Simnett, 1984) -made it possible to compute the total energy input by nonthermal electrons in the chromosphere in the assumption of thick-target interaction. The value obtained was fairly consistent with the soft-X-ray energy present at the coronal level as deduced from the XRP data.…”

Reflecting at 30.4 and Antireflecting at 58.4 nm

“…The layer pairs suggested in the literature include, SiC/Mg [4], Mo/Si [5], and Ir/Si [6] with near-normal reflectances of: unknown, 25% and 16%, respectively [4][5][6]. In addition, Larruquert investigated novel ways to obtain high reflectances in the EUV using stacks composed of more than two materials [7].…”