Improvement of Heat-Treated Niobium Surface by In-situ Plasma Treatment Applied to Superconducting RF Resonator
Abstract
A specific heat treatment at 300 C, named medium-temperature baking (Mid-T baking) is applied to superconducting radio-frequency (SRF) accelerating cavities to improve the quality factor (Qo) at medium accelerating fields (10 to 20 MV/m). This treatment is very successful when done properly as it can reduce by almost a factor of two the power dissipations in this field range. However, surface contamination can lead to the degradation of Qo instead. Plasma-based surface treatment provides an effective approach to eliminate contaminants from the Niobium surface. In this study an insitu plasma cleaning process with argon containing 10 % O2 was performed to remove hydrocarbons from Niobium surface. The treatment was applied before and after a heat treatment at 500 C under ultra-high vacuum conditions (Mid-T baking). Changes in chemical speciation and oxide layer alteration induced by plasma processing were analyzed using insitu X-ray photoelectron spectroscopy (XPS) and exsitu scanning electron microscopy (SEM). The results show that plasma treatment modifies the composition of Niobium oxides, converting a Nb2O5 layer into NbO2. Furthermore, a plasma treatment before Mid-T baking helps reduce unstable oxides such as NbxO and significantly increases the proportion of metallic Niobium at the surface. The Niobium sample treated by plasma prior to Mid-T baking showed a 53 % reduction in carbide formation. Moreover, the C1s component attributed to NbC bonds shifts toward lower binding energy, indicating the formation of a more metallic NbC phase. Whereas without plasma treatment, the higher binding energy component observed after Mid T baking is consistent with Nb2C.
Related
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BibTeX
@misc{boutelaa2026improvement,
title = {{Improvement of Heat-Treated Niobium Surface by In-situ Plasma Treatment Applied to Superconducting RF Resonator}},
author = {C. Boutelaa and S. Gruszka and C. Cheney and J. Yemane and T. Gerardin and E. Mistretta and J. Demailly and R. Laxdal and P. Kolb and J. Keir and B. Mercier and N. Prud homme and G. Sattonnay and D. Longuevergne},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2606.12091},
eprint = {2606.12091},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.12091},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Improvement of Heat-Treated Niobium Surface by In-situ Plasma Treatment Applied to Superconducting RF Resonator
AU - C. Boutelaa
AU - S. Gruszka
AU - C. Cheney
AU - J. Yemane
AU - T. Gerardin
AU - E. Mistretta
AU - J. Demailly
AU - R. Laxdal
AU - P. Kolb
AU - J. Keir
AU - B. Mercier
AU - N. Prud homme
AU - G. Sattonnay
AU - D. Longuevergne
PY - 2026
DA - 2026/11/01
PB - arXiv
DO - 10.48550/arxiv.2606.12091
UR - https://arxiv.org/abs/2606.12091
AB - A specific heat treatment at 300 C, named medium-temperature baking (Mid-T baking) is applied to superconducting radio-frequency (SRF) accelerating cavities to improve the quality factor (Qo) at medium accelerating fields (10 to 20 MV/m). This treatment is very successful when done properly as it can reduce by almost a factor of two the power dissipations in this field range. However, surface contamination can lead to the degradation of Qo instead. Plasma-based surface treatment provides an effective approach to eliminate contaminants from the Niobium surface. In this study an insitu plasma cleaning process with argon containing 10 % O2 was performed to remove hydrocarbons from Niobium surface. The treatment was applied before and after a heat treatment at 500 C under ultra-high vacuum conditions (Mid-T baking). Changes in chemical speciation and oxide layer alteration induced by plasma processing were analyzed using insitu X-ray photoelectron spectroscopy (XPS) and exsitu scanning electron microscopy (SEM). The results show that plasma treatment modifies the composition of Niobium oxides, converting a Nb2O5 layer into NbO2. Furthermore, a plasma treatment before Mid-T baking helps reduce unstable oxides such as NbxO and significantly increases the proportion of metallic Niobium at the surface. The Niobium sample treated by plasma prior to Mid-T baking showed a 53 % reduction in carbide formation. Moreover, the C1s component attributed to NbC bonds shifts toward lower binding energy, indicating the formation of a more metallic NbC phase. Whereas without plasma treatment, the higher binding energy component observed after Mid T baking is consistent with Nb2C.
ER -