Effects of interstitial oxygen on the superconductivity of niobium

Koch, Carl C.; Scarbrough, J. O.; Kroeger, D. M.

doi:10.1103/physrevb.9.888

Cited by 179 publications

(63 citation statements)

References 24 publications

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“…These studies indicate that baking causes a partial disintegration of the external Nb 2 O 5 layer and the formation of metallic suboxides (NbO, NbO 2 ). The effect of interstitial oxygen on the upper critical field of niobium was studied by Koch et al [34]. The concentration c O of oxygen in atomic per cent can be derived from an expression valid at 4.2 K [35] c O [at.…”

Section: Critical Surface Fieldmentioning

confidence: 99%

Surface superconductivity in niobium for superconducting RF cavities

Casalbuoni

Knabbe²,

Kötzler

et al. 2005

Nuclear Instruments and Methods in Physics Research Section A:

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A systematic study is presented on the superconductivity (sc) parameters of the ultrapure niobium used for the fabrication of the nine-cell 1.3 GHz cavities for the linear collider project TESLA. Cylindrical Nb samples have been subjected to the same surface treatments that are applied to the TESLA cavities: buffered chemical polishing (BCP), electrolytic polishing (EP), low-temperature bakeout (LTB). The magnetization curves and the complex magnetic susceptibility have been measured over a wide range of temperatures and dc magnetic fields, and also for different frequencies of the applied ac magnetic field. The bulk superconductivity parameters such as the critical temperature T c = 9.26 K and the upper critical field B c2 (0) = 410 mT are found to be in good agreement with previous data. Evidence for surface superconductivity at fields above B c2 is found in all samples. The critical surface field exceeds the Ginzburg-Landau field B c3 = 1.695B c2 by about 10% in BCP-treated samples and increases even further if EP or LTB are applied. From the field dependence of the susceptibility and a power-law analysis of the complex ac conductivity and resistivity the existence of two different phases of surface superconductivity can be established which resemble the Meissner and Abrikosov phases in the bulk: (1) "coherent surface superconductivity", allowing sc shielding currents flowing around the entire cylindrical sample, for external fields B in the range B c2 < B < B coh c3 , and (2) "incoherent surface superconductivity" with disconnected sc domains for B coh c3 < B < B c3 . The "coherent" critical surface field separating the two phases is found to be B coh c3 = 0.81 B c3 for all samples. The exponents in the power law analysis are different for BCP and EP samples, pointing to different surface topologies.

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Section: Critical Surface Fieldmentioning

confidence: 99%

Surface superconductivity in niobium for superconducting RF cavities

Casalbuoni

Knabbe²,

Kötzler

et al. 2005

Nuclear Instruments and Methods in Physics Research Section A:

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“…Extensive data [21] are available on the increase of H c2 resulting from the presence in the niobium lattice of interstitial oxygen in various proportions. They show that H c2 is multiplied by 1.54 (resp.…”

Section: The Upper Critical Fieldmentioning

confidence: 99%

Fluxon pinning in niobium films

Benvenuti

Calatroni

Darriulat

et al. 2001

Physica C: Superconductivity

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“…If the presence of Ta clusters is feared, eddy current scanning can be used to exclude Nb discs with such defects from the cavity fabrication process [24].…”

Section: Niobium Purity and Tantalum Contentmentioning

confidence: 99%

“…Specifications for the content of main impurities in Nb were dictated by the need to assure a high RRR value and to limit the concentration of impurities such as hydrogen and oxygen which have well known negative impact on the superconducting properties of Nb [24,25]. The understanding of various factors which contribute to Nb RRR continues to mature [26].…”

Section: Bulk Nb Materials Randdmentioning

confidence: 99%

Superconducting Radio-Frequency Technology R&D for Future Accelerator Applications

Reece¹,

Ciovati²

2013

Reviews of Accelerator Science and Technology

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Superconducting rf technology (SRF) is evolving rapidly as are its applications. While there is active exploitation of what one may term the current state-of-the-practice, there is also rapid progress expanding in several dimensions the accessible and useful parameter space. While state-of-the-art performance sometimes outpaces thorough understanding, the improving scientific understanding from active SRF research is clarifying routes to obtain optimum performance from present materials and opening avenues beyond the standard bulk niobium. The improving technical basis understanding is enabling process engineering to both improve performance confidence and reliability and also unit implementation costs. Increasing confidence in the technology enables the engineering of new creative application designs. We attempt to survey this landscape to highlight the potential for future accelerator applications.

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Effects of interstitial oxygen on the superconductivity of niobium

Cited by 179 publications

References 24 publications

Surface superconductivity in niobium for superconducting RF cavities

Surface superconductivity in niobium for superconducting RF cavities

Fluxon pinning in niobium films

Superconducting Radio-Frequency Technology R&D for Future Accelerator Applications

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