Advanced materials for multilayer mirrors for extreme ultraviolet solar astronomy

Abstract

We provide an analysis of contemporary multilayer optics for extreme ultraviolet (EUV) solar astronomy in the wavelength ranges: λ=12.9-13.3 nm, λ=17-21 nm, λ=28-33 nm, and λ=58.4 nm. We found new material pairs, which will make new spaceborne experiments possible due to the high reflection efficiencies, spectral resolution, and long-term stabilities of the proposed multilayer coatings. In the spectral range λ=13 nm, Mo/Be multilayer mirrors were shown to demonstrate a better ratio of reflection efficiency and spectral resolution compared with the commonly used Mo/Si. In the spectral range λ=17-21 nm, a new multilayer structure Al/Si was proposed, which had higher spectral resolution along with comparable reflection efficiency compared with the commonly used Al/Zr multilayer structures. In the spectral range λ=30 nm, the Si/B₄C/Mg/Cr multilayer structure turned out to best obey reflection efficiency and long-term stability. The B₄C and Cr layers prevented mutual diffusion of the Si and Mg layers. For the spectral range λ=58 nm, a new multilayer Mo/Mg-based structure was developed; its reflection efficiency and long-term stability have been analyzed. We also investigated intrinsic stresses inherent for most of the multilayer structures and proposed possibilities for stress elimination.

Extreme Ultraviolet Multilayer Nanostructures and Their Application to Solar Plasma Observations: A Review

“…86 Additionally, such ML has been demonstrated to have good stability over time. [87][88][89] Recent research has been oriented to develop techniques for further improving the Al/Zr performance. The adoption of a 1% Si-doping Al layer was proposed for increasing the reflectance peak: 88 this small concentration of Si highly affects the crystallization of both Al and Zr layers with a consequent decrease of the interface roughness.…”

Beryllium-Based Multilayer Mirrors and Filters for the Extreme Ultraviolet Range

“…Mo/Si 30 54 0 875 Al/Mo/SiC 5 6 53.4 0 76 Al/Mo/B 4 C 5 6 55.5 0 875 Zr/Al 31 56 0 6 Si/Al 10 48 0 48 R = 55.5%, = 0.875 nm, and Mo/Al/SiC-R = 53.4%, = 0.76 nm. The Zr/Al MLM has better resolution with comparable reflection coefficient: R = 56%, = 0.6 nm.…”

“…Therefore, when developing and synthesizing a MLM for future space experiments, it becomes necessary to find the optimal ratio of the spectral selectivity and the reflection coefficient. Ideally, it is required to maintain or even exceed the high coefficients of existing MLM for solar astronomy, [4][5][6][7][8][9][10] and to increase their spectral selectivity.…”

Особенности экспериментальных спектров лазерной плазмы с плотной Xe газоструйной мишенью в дальнем ультрафиолетовом диапазоне

“…При этом по мощности EUV-луча Xe источник, как минимум, не будет усту-пать источнику на основе Sn, превосходя последний по " чистоте" и инженерной простоте. Ранее литография на длине волны λ = 11.2 nm считалась невозможной из-за отсутствия зеркал для этой длины волны, но сейчас первые в мире образцы Mo/Be-зеркал, пригодных для работы на λ = 11.2 nm, уже созданы [5].…”