Investigation of Frequency Behavior Near Tc of Niobium Superconducting Radio-Frequency Cavities

Bafia, Daniel; Checchin, Mattia; Melnychuk, Oleksandr; Romanenko, Alexander; Sergatskov, Dmitri; Zasadzinski, J. F.

doi:10.18429/jacow-srf2019-mop031

Cited by 2 publications

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“…Frontiers in Physics frontiersin.org temperatures of the high-Q Nb SRF cavities with nitrogen impurities reported in [11,67,68]. These cavities also show a negative frequency shift anomaly in a very narrow temperature range close to T c [68].…”

Section: T C Versus Disorder In Nbmentioning

confidence: 79%

Effects of anisotropy and disorder on the superconducting properties of niobium

Zarea,

Ueki,

Sauls

2023

Front. Phys.

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We report results for the superconducting transition temperature and anisotropic energy gap for pure niobium based on Eliashberg’s equations and electron and phonon band structures computed from density functional theory. The electronic band structure is used to construct the Fermi surface and calculate the Fermi velocity at each point on the Fermi surface. The phonon bands are in excellent agreement with inelastic neutron scattering data. The corresponding phonon density of states and electron–phonon coupling define the electron–phonon spectral function, α2F(p, p′; ω), and the corresponding electron–phonon pairing interaction, which is the basis for computing the superconducting properties. The electron–phonon spectral function is in good agreement with existing tunneling spectroscopy data except for the spectral weight of the longitudinal phonon peak at ℏωLO = 23 meV. We obtain an electron–phonon coupling constant of λ = 1.057, renormalized Coulomb interaction μ⋆ = 0.218, and transition temperature Tc = 9.33 K. The corresponding strong-coupling gap at T = 0 is modestly enhanced, Δ0 = 1.55 meV, compared to the weak-coupling BCS value Δ0wc=1.78kBTc=1.43meV. The superconducting gap function exhibits substantial anisotropy on the Fermi surface. We analyze the distribution of gap anisotropy and compute the suppression of the superconducting transition temperature using a self-consistent T-matrix theory for quasiparticle-impurity scattering to describe niobium doped with non-magnetic impurities. We compare these results with experimental results on niobium SRF cavities doped with nitrogen impurities.

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Section: T C Versus Disorder In Nbmentioning

confidence: 79%

Effects of anisotropy and disorder on the superconducting properties of niobium

Zarea,

Ueki,

Sauls

2023

Front. Phys.

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“…In addition, small enhancement in penetration depth close to 𝑇 𝑐 was observed. A much pronounced peak was reported in nitrogen and titanium doped cavities [20]. More systematic studies with different surface modification with higher temperature baking (200-400 • C) are planned in order to understand the effect of baking on performance of SRF cavities and flux trapping sensitivity.…”

Section: Discussionmentioning

confidence: 96%

Effect of duration of 120 oC baking on the performance on superconducting radio frequency niobium cavities

Khanal

Dhakal

2022

NAPAC 2022, Albuquerque, NM, USA, 07-12 August 2022

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Over the last decade much attention was given in increasing the quality factor of superconducting radio frequency cavities by impurity doping. Prior to the era of doping, the final cavity processing technique to achieve the high accelerating gradient includes the "in-situ" low temperature baking of SRF cavities at temperature ∼ 120 • C for several hours. Here, we present the results of a series of measurements on 1.3 GHz TESLA shape single-cell cavities with successive low temperature baking at 120 • C up to 96 hours. The experimental data were analyzed with available theory of superconductivity to elucidate the effect of the duration of low temperature baking on the superconducting properties of cavity materials as well as the rf performance. In addition, the rf loss related to the trapping of residual magnetic field refereed as flux trapping sensitivity was measured with respect to the duration of 120 • C bake.

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Investigation of Frequency Behavior Near Tc of Niobium Superconducting Radio-Frequency Cavities

Cited by 2 publications

References 0 publications

Effects of anisotropy and disorder on the superconducting properties of niobium

Effects of anisotropy and disorder on the superconducting properties of niobium

Effect of duration of 120 oC baking on the performance on superconducting radio frequency niobium cavities

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