用于大m值11B4C基Ni/Ti超镜中子光学器件的材料设计优化
Material design optimization for large-m 11B4C-based Ni/Ti supermirror neutron optics
AI总结：
针对含11B4C的Ni/Ti中子超镜，本文比较多种多层结构，提出深度梯度混合设计，在全散射矢量范围实现更高反射率。
摘要：
最先进的Ni/Ti超镜中子光学器件因界面宽度而存在反射强度有限和中子能量范围受限的问题。掺入低中子吸收的11B4C可增强反射率，并允许沉积更薄的层，从而实现具有更高m值、更高效的超镜。然而，掺入11B4C会降低光学衬度，限制低散射矢量处可达到的反射率，使该方法不可行。本研究探索了多种方法，以优化含11B4C的Ni/Ti超镜的材料设计，从而在低散射矢量处保持高反射率，并在大散射矢量处实现较小的界面宽度。针对30 Å、48 Å和84 Å的多层膜周期，研究了散射长度密度衬度与界面宽度的关系，所涉及的设计包括纯Ni/Ti多层膜、在Ni层和Ti层中共沉积11B4C的多层膜、仅在Ni层中共沉积11B4C的多层膜，以及在Ni层与Ti层之间将11B4C作为薄中间层的多层膜。结果表明，采用深度梯度混合材料设计，即在约26 Å以下的Ni层和Ti层内部掺入11B4C，并在较厚的Ni层与Ti层之间引入1.5 Å的11B4C中间层，可在整个散射矢量范围内实现比最先进Ni/Ti多层膜更高的反射率。
英文摘要：
State-of-the-art Ni/Ti supermirror neutron optics have limited reflected intensity and a restricted neutron energy range due to the interface width. Incorporating low-neutron-absorbing 11B4C enhances reflectivity and allows for thinner layers to be deposited, with which more efficient supermirrors with higher m-values can be realized. However, incorporating 11B4C reduces the optical contrast, limiting the attainable reflectivity at low scattering vectors, making this approach infeasible. This study explores various approaches to optimize the material design of 11B4C-containing Ni/Ti supermirrors to maintain high reflectivity at low scattering vectors and achieve low interface widths at large scattering vectors. The scattering length density contrast versus interface width is investigated for multilayer periods of 30 Å, 48 Å, and 84 Å, for designs involving pure Ni/Ti multilayers, multilayers with 11B4C co-deposited in Ni and Ti layers, multilayers with 11B4C co-deposited only in Ni layers, and multilayers with 11B4C as thin interlayers between Ni and Ti layers. Our results suggest that a depth-graded hybrid material design by incorporating 11B4C inside the Ni and Ti layers, below approximately 26 Å, and introducing 1.5 Å 11B4C interlayers between the thicker Ni and Ti layers can achieve a higher reflectivity than state-of-the-art Ni/Ti multilayers over the entire scattering vector range.
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