Nb3sn气相扩散涂层中锡在铌上的初始生长
Initial Growth Of Tin On Niobium For Vapor Diffusion Coating Of Nb3sn
摘要：
Nb 3Sn具有在品质因数、加速梯度和操作温度（4.2 K vs 2 K）方面实现优异性能的潜力，从而与传统的铌SRF加速器腔相比显著降低了资本和操作成本。在铌上的Nb 3Sn的锡蒸气扩散涂层似乎是迄今为止制造这种腔的简单但最有效的技术。在这里，空腔内表面涂层是通过两步过程获得的：成核，然后沉积。第一步通常在恒定低温（500 °C）下用Sn/SnCl 2完成数小时。为了阐明这一步骤的作用，我们系统地研究了铌表面成核在不同的工艺条件下。使用SEM/EDS、AFM、XPS、SAM和TEM表征在典型的锡/氯化锡工艺中获得的表面。在标准条件下成核的表面的检查显示不仅锡颗粒，而且锡膜的表面上类似于通过Stranski-Krastanov生长模式获得的表面。与没有成核获得的涂层相比，用SnCl 2尝试的所有成核产生了更好的Nb 3Sn涂层的均匀性，所述涂层通常包括具有不规则晶粒结构的随机斑片状区域。尽管成核参数的变化能够在成核后产生不同的表面，但没有发现对最终涂层有任何显著影响的证据。
英文摘要：
Nb3Sn has the potential to achieve superior performance in terms of quality factor, accelerating gradient and operating temperature (4.2 K vs 2 K) resulting in significant reduction in both capital and operating costs compared to traditional niobium SRF accelerator cavities. Tin vapor diffusion coating of Nb3Sn on niobium appears to be a simple, yet most efficient technique so far to fabricate such cavities. Here, cavity interior surface coatings are obtained by a two step process: nucleation followed by deposition. The first step is normally accomplished with Sn/SnCl2 at a constant low temperature (500 °C) for several hours. To elucidate the role of this step, we systematically studied the niobium surface nucleated under varying process conditions. The surfaces obtained in typical tin/tin chloride processes were characterized using SEM/EDS, AFM, XPS, SAM and TEM. Examination of the surfaces nucleated under the standard conditions revealed not only tin particles, but also tin film on the surfaces resembling the surface obtained by Stranski-Krastanov growth mode. All the nucleation attempted with SnCl2 yielded better uniformity of Nb3Sn coating compared to coating obtained without nucleation, which often included random patchy regions with irregular grain structure. Even though the variation of nucleation parameters was able to produce different surfaces following nucleation, no evidence was found for any significant impact on the final coating.
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