Tunneling Spectroscopy Study of Low Baked Bulk Niobium for Superconducting RF Cavity Applications
Abstract
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~∘C for 48 h and subjected to a two-step bake at 75~∘C for 2 h followed by 120~∘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~∘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.
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BibTeX
@misc{curci2026tunneling,
title = {{Tunneling Spectroscopy Study of Low Baked Bulk Niobium for Superconducting RF Cavity Applications}},
author = {Ivana Curci and Gregoire Jullien and Luc Maurice and Fabien Eozenou and Patrick Sahuquet and Thomas Proslier},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.21865},
eprint = {2609.21865},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.21865},
}
RIS
TY - UNPB
TI - Tunneling Spectroscopy Study of Low Baked Bulk Niobium for Superconducting RF Cavity Applications
AU - Ivana Curci
AU - Gregoire Jullien
AU - Luc Maurice
AU - Fabien Eozenou
AU - Patrick Sahuquet
AU - Thomas Proslier
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2609.21865
UR - https://arxiv.org/abs/2609.21865
AB - 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~^∘C for 48 h and subjected to a two-step bake at 75~^∘C for 2 h followed by 120~^∘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~^∘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.
ER -