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 (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, B₄C/Mg, C/Mg, C/Al, Mo/Si, B₄C/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.

Keywords

thin film optics / solar He-II radiation / extreme ultraviolet / multilayer reflective mirror / magnetron sputtering / synchrotron radiation

References

[1] RavetM F, BridouF, Zhang-SongX, . Ion beam deposited Mo/Si multilayers for EUV imaging applications in astrophysics. Proceedings of SPIE, 2004, 5250: 99–108

[2] GardnerL, KohlJ, CranmerS, . The advanced solar coronal explorer mission (ASCE).Proceedings of SPIE, 1999, 3764: 134–146

[3] GrigonisM, KnystautasE J. C/Si multilayer mirrors for the 25–30 nm wavelength region. Applied Optics, 1997, 36(13): 2839–2842

[4] ZhangZ, WangZ S, QinS J, . The design of X-ray supermirror with broad angle range. Acta Photonica Sinica, 2003, 32(2): 253–256 (in Chinese)

[5] VialJ C, SongX Y, LemaireP, . The solar high-resolution imager-coronagraph LYOT mission. Proceedings of SPIE, 2003, 4853: 479–489

[6] WindtD L, DonguyS, SeelyJ F, . EUV multilayers for solar physics. Proceedings ofSPIE, 2004, 5168: 1–11

[7] WangF L, WangZ S, QinS J, . Investigation of ultra-short-period W/C multilayers for soft X-ray optics. Chinese Optics Letters, 2005, 3(7): 425–427

[8] ZhangZ, WangZ S, WangF L, . Design and fabrication of broad angular range depth-graded C/W multilayer mirror for hard X-ray optics. Chinese Optics Letters, 2005, 3(7): 422–424

[9] ChenB, NiQ L, CaoJ H, . Development of a space soft X-ray and EUV normal incidence telescope. Optics and Precision Engineering, 2003, 11(4): 315–319 (in Chinese)

[10] WangZ S, ZhangS M, WuW J, . B₄C/Mo/Si high reflectivity multilayer mirror at 30.4 nm. Chinese Optics Letters, 2006, 4(10): 611–613

[11] WangZ S, WangH C, ZhuJ T, . Broad angular multilayer analyzer for soft X-rays, Optics Express, 2006, 14(6): 2533–2538

[12] WangZ S, WangH C, ZhuJ T, . Broadband multilayer polarizers for the extreme ultraviolet. Journal of Applied Physics, 2006, 99(5): 056108

[13] WangZ S, WangH C, ZhuJ T, . Extreme ultraviolet broadband Mo/Y multilayer analyzers. Applied Physics Letters, 2006, 89(24): 241120

[14] WangZ S, WangH C, ZhuJ T, . Broadband Mo/Si multilayer transmission phase retarders for the extreme ultraviolet. Applied Physics Letters, 2007, 90(3): 031901

[15] WangH C, ZhuJ T, WangZ S, . Broadband Mo/Si multilayer analyzers for the 15–17 nm wavelength range. Thin Solid Films, 2006, 515(4): 2523–2526

[16] SpillerE. Reflective multilayer coatings for the far UV region. Applied Optics, 1976, 15(10): 2333–2338

[17] WangZ S, MaY Y. Researches on extreme ultraviolet multilayers fabrication. Optical Technique, 2001, 27(6): 532–534 (in Chinese)

[18] WangH C, WangZ S, QinS J, . Analysis of the reflectivity of Mo/Si multilayer film for soft X-ray. Acta Optica Sinica, 2003, 23(11): 1362–1365 (in Chinese)

[19] WangZ S. Effect of film thickness errors on performance of soft X-ray multilayer. Optics and Precision Engineering, 2003, 11(2): 136–138 (in Chinese)

[20] ZhuJ T, WangZ S, ZhangS M, . High reflectivity multilayer mirror for He-II radiation at 30.4 nm in solar physics application, In: Optical Interference Coatings 2007, Tucson: Optical Society of America, 2007, FA9

Acknowledgements

This work was supported by the National Nature Science Foundation of China (Grant Nos. 10435050, 10675092), and Hi-Tech Research and Development Program of China (No. 2006AA12Z139).

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg