SiC/Mg multilayer reflective mirror for He-II radiation at 30.4 nm and its thermal stability

Abstract

In applications of solar physics, extreme ultraviolet imaging of solar corona by selecting the He-II (l 5 30.4 nm) emission line requires high reflectivity multilayer mirrors. Some material combinations were studied to design the mirrors working at a wavelength of 30.4 nm, including SiC/Mg, B on optimization of the largest reflectivity and the narrowest width for the multilayer mirror, a SiC/Mg material combination was selected as the mirror and fabricated by a magnetron sputtering system. The layer thicknesses of the SiC/Mg multilayer were measured by an X-ray diffractometer. Reflectivities were then measured on beamline U27 at the National Synchrotron Radiation Laboratory (NSRL) in Hefei, China. At a wavelength of 30.4 nm, the measured reflectivity is as high as 38.0%. Furthermore, a series of annealing experiments were performed to investigate the thermal stability of the SiC/Mg multilayer.

Focusing diffraction optics for orbital telescopes

“…Therefore, other multilayer mirrors with a high reflection coefficient should be used at this wavelength. The reflectance efficiencies of certain combinations of materials based on Mg and Si (including SiC/Mg, B 4 C/Mg, Mo/Si, B 4 C/Si, SiC/Si, C/Si, and Sc/Si MISs) have been studied in [35] as part of research into the production of a multilayer for λ = 30.4 nm. It was demonstrated that the SiC/Mg combination features the maximum reflectance and the narrowest transmission band.…”

“…The He-II (λ = 30.4 nm) emission line, which was chosen for solar physics applications (e.g., solar corona imaging), necessitates the use of multilayer mirrors with a high reflectance. Several combinations of materials (including SiC/Mg, B 4 C/Mg, C/Mg, Co/Mg, and Si/Mg [35,43]) have been examined for the design of mirrors operating at a wavelength of 30.4 nm. The reflectance values of Co/Mg and SiC/Mg MISs turned out to be the highest ones and reached 40.3% and 44.6%, respectively, under almost normal incidence.…”