TEM和EELS揭示的降低超导射频铌腔性能的纳米结构特征
Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by TEM and EELS
摘要：
磁穿透深度约100 nm的纳米缺陷结构是限制铌超导射频腔性能的关键。使用先进的腔RF测量过程中的温度测量，TEM结构和从腔壁提取的样品的成分表征的独特组合，我们发现存在的纳米级的电抛光腔的高场Q斜率的限制，并显示减少氢化物的形成在电抛光腔120 C烘烤后。此外，我们证明，添加800 C的氢脱气，然后光缓冲化学抛光恢复氢化物的形成前120 C烘烤水平。我们还表明没有铌氧化物沿晶界和120 ℃烘烤后的表面氧化物的修改。
英文摘要：
Nanoscale defect structure within the magnetic penetration depth of ~100nm is key to the performance limitations of niobium superconducting radio frequency (SRF) cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120C baking. Furthermore, we demonstrate that adding 800C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120C bake.
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