TY  - CONF
AU  - Yang, Z.T.
AU  - Hao, J.K.
AU  - Liu, K.X.
AU  - Quan, S.W.
ED  - Saito, Kenji
ED  - Xu, Ting
ED  - Sakamoto, Naruhiko
ED  - Schaa, Volker R.W.
ED  - Thomas, Paul W.
TI  - The Oxidizing Responses of Baked Niobium Exposed to Various Gases via In-situ NAXPS
J2  - Proc. of SRF2023, Grand Rapids, MI, USA, 25-30 June 2023
CY  - Grand Rapids, MI, USA
T2  - International Conference on RF Superconductivity
T3  - 21
LA  - english
AB  - We carried out in-situ NAXPS (Near-atmospheric X-ray Photoelectron Spectroscopy) on SRF-cavity class niobium to observe its oxidizing responses when exposed to various gases. The niobium samples were baked at 800°C until the peaks of niobium oxides disappeared in the spectrum. Then the revealed pure niobium samples were exposed to the air-proportion mixture of nitrogen and oxygen, pure oxygen, and pure water vapor respectively. And for the pure oxygen and water vapor group, we also carried out TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectroscopy) measurements before and after the baking and oxidation experiments. We found that pure oxygen and water vapor could oxidize niobium at similar rate which was faster than the N2/O2 mixture. After re-oxidized by pure oxygen and water vapor, the niobium sample presented a significant increase of interstitial carbon and a moderate increase of interstitial oxygen in the magnetic penetration depth, while it showed a mild decrease of interstitial hydrogen.
PB  - JACoW Publishing
CP  - Geneva, Switzerland
SP  - 662
EP  - 666
KW  - niobium
KW  - cavity
KW  - experiment
KW  - SRF
KW  - vacuum
DA  - 2023/09
PY  - 2023
SN  - 2673-5504
SN  - 978-3-95450-234-9
DO  - doi:10.18429/JACoW-SRF2023-WEPWB045
UR  - https://jacow.org/srf2023/papers/wepwb045.pdf
ER  - 

TY  - CONF
AU  - Liu, H.
AU  - Hao, J.K.
AU  - Yang, Z.T.
ED  - Saito, Kenji
ED  - Xu, Ting
ED  - Sakamoto, Naruhiko
ED  - Schaa, Volker R.W.
ED  - Thomas, Paul W.
TI  - The Interaction among Interstitial C/N/O/H and Vacancy in  Niobium via First-Principles Calculation
J2  - Proc. of SRF2023, Grand Rapids, MI, USA, 25-30 June 2023
CY  - Grand Rapids, MI, USA
T2  - International Conference on RF Superconductivity
T3  - 21
LA  - english
AB  - We calculate the interaction among zero dimensional defects in niobium lattice through first-principles calculation. And we compare the trapping effect of hydrogen among carbon, nitrogen, and oxygen as well as the trapping effect of interstitial atoms by vacancy. We find that the interstitial C/N/O have similar effect of trapping interstitial hydrogen in niobium lattice, and the vacancy can trap interstitial C/N/O/H in adjacent protocells and strengthen their chemical bond with Nb. These calculations give some explanation for improving superconducting performance of niobium cavities through medium temperature baking.
PB  - JACoW Publishing
CP  - Geneva, Switzerland
SP  - 778
EP  - 783
KW  - niobium
KW  - lattice
KW  - electron
KW  - site
KW  - cavity
DA  - 2023/09
PY  - 2023
SN  - 2673-5504
SN  - 978-3-95450-234-9
DO  - doi:10.18429/JACoW-SRF2023-WEPWB084
UR  - https://jacow.org/srf2023/papers/wepwb084.pdf
ER  -