Nb3Sn is a promising next-generation material for superconducting radiofrequency cavities, with significant potential for both large scale and compact accelerator applications. However, so far, Nb3Sn cavities have been limited to cw accelerating fields <18 MV/m. In this paper, new results are presented with significantly higher fields, as high as 24 MV/m in single cell cavities. Results are also presented from the first ever Nb3Sn-coated 1.3 GHz 9-cell cavity, a full-scale demonstration on the cavity type used in production for the European XFEL and LCLS-II. Results are presented together with heat dissipation curves to emphasize the potential for industrial accelerator applications using cryocooler-based cooling systems. The cavities studied have an atypical shiny visual appearance, and microscopy studies of witness samples reveal significantly reduced surface roughness and smaller film thickness compared to typical Nb3Sn films for superconducting cavities. Possible mechanisms for increased maximum field are discussed as well as implications for physics of RF superconductivity in the low coherence length regime. Outlook for continued development is presented.

中文翻译：

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Nb3Sn 超导射频腔在首次实际加速器应用方面的进展

Nb3Sn 是一种很有前途的下一代超导射频腔材料，在大规模和紧凑型加速器应用中具有巨大的潜力。然而，到目前为止，Nb3Sn 腔仅限于 cw 加速场 <18 MV/m。在本文中，新的结果显示了更高的场，在单细胞腔中高达 24 MV/m。还展示了第一个 Nb3Sn 涂层 1.3 GHz 9 单元腔的结果，这是对欧洲 XFEL 和 LCLS-II 生产中使用的腔类型的全面演示。结果与散热曲线一起呈现，以强调使用基于低温冷却器的冷却系统的工业加速器应用的潜力。研究的空腔具有非典型的闪亮视觉外观，目击样品的显微镜研究表明，与用于超导腔的典型 Nb3Sn 薄膜相比，表面粗糙度显着降低，薄膜厚度更小。讨论了增加最大场的可能机制以及对低相干长度范围内 RF 超导物理的影响。提出了持续发展的展望。