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

• Published in: Frontiers of Optoelectronics (Online) 2008, Vol.1 (3-4), p.305-308
• Main Authors: ZHU, Jingtao, XU, Da, ZHANG, Shumin, WU, Wenjuan, ZHANG, Zhong, WANG, Fengli, WANG, Bei, LI, Cunxia, XU, Yao, WANG, Zhanshan, CHEN, Lingyan, ZHOU, Hongjun, HUO, Tonglin
• Format: Article
• Language: English
• Subjects: Biomedical Engineering and Bioengineering; Electrical Engineering; Engineering; extreme ultraviolet; magnetron sputtering; multilayer reflective mirror; Physics; Research Article; solar He-II radiation; synchrotron radiation; thin film optics
• ISSN: 2095-2759; 1674-4128; 2095-2767; 1674-4594
• DOI: 10.1007/s12200-008-0028-y

In applications of solar physics, extreme ultraviolet imaging of solar corona by selecting the He-II ( λ = 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 4C/Mg, C/Mg, C/Al, Mo/Si, B 4C/Si, SiC/Si, C/Si, and Sc/Si. Based 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.