发表机构
IRFU, CEA, University Paris-Saclay（法国原子能及替代能源研究所，法国原子能和替代能源委员会，巴黎萨克雷大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过点接触隧道谱实验，发现低温烘烤（特别是两步烘烤）能显著抑制腔级铌表面由氢化物引起的超导退化区域，为理解SRF腔性能提升提供了微观证据。
AI 中文摘要
采用点接触隧道（PCT）谱技术，探测了经代表超导射频（SRF）腔表面处理的腔级铌的局部超导性质。将电抛光（EP）样品与在120~$^\circ$C下烘烤48小时、以及经过75~$^\circ$C烘烤2小时随后120~$^\circ$C烘烤48小时两步烘烤处理的样品进行了比较。尽管超导能隙$\Delta$主要分布在体铌值（约1.5 meV）附近，但在EP样品的15%–29%的结中观察到能隙被强烈抑制的区域（minigaps）。其出现率在120~$^\circ$C烘烤后降至6%，在两步处理后仅降至1%。具有minigaps的谱线可由Usadel邻近效应模型很好地描述，这与超导铌耦合到正常区域（我们归因于氢化物形成）的模型一致。这些结果提供了直接的微观证据，表明低温烘烤抑制了腔级铌中表面超导性退化的区域。两步烘烤所实现的显著减少进一步支持了氢化物相关邻近效应与决定SRF腔性能的表面超导性质之间的联系。
英文摘要
Point-contact tunneling (PCT) spectroscopy was used to probe the local superconducting properties of cavity-grade niobium following surface treatments representative of superconducting radio-frequency (SRF) cavities. Electropolished (EP) samples were compared with samples baked at 120~$^\circ$C for 48 h and subjected to a two-step bake at 75~$^\circ$C for 2 h followed by 120~$^\circ$C for 48 h. Although the superconducting gap $Δ$ is predominantly distributed around the bulk Nb value (~1.5 meV), regions exhibiting strongly suppressed gaps (minigaps) are observed in 15--29% of junctions on EP samples. Their occurrence decreases to 6% after the 120~$^\circ$C bake and to only 1% after the two-step treatment. Spectra exhibiting minigaps are well described by the Usadel proximity-effect model, consistent with superconducting Nb coupled to normal regions that we attribute to hydride formation. These results provide direct microscopic evidence that low-temperature baking suppresses regions of degraded surface superconductivity in cavity-grade Nb. The pronounced reduction achieved by the two-step bake further supports a link between hydride-related proximity effects and the surface superconducting properties governing SRF cavity performance.
