Effect of interstitial impurities on the field dependent microwave surface resistance of niobium

Martinello, Martina; Grassellino, Anna; Checchin, Mattia; Romanenko, Alexander; Melnychuk, Oleksandr; Sergatskov, Dmitri; Posen, S.; Zasadzinski, J. F.

doi:10.1063/1.4960801

Cited by 51 publications

(81 citation statements)

References 30 publications

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“…This can be expected since only trapped-vortex segments at the surface contribute to rf losses. The flux sensitivity S increased by ∼ 50% after LTB and ∼ 76% after N-doping, showing that surface treatments significantly affect S, consistent with published data on fine-grain Nb cavities [12,15,16].…”

Section: Comparison With Published Data and Theoretical Modelssupporting

confidence: 89%

Flux expulsion in niobium superconducting radio-frequency cavities of different purity and essential contributions to the flux sensitivity

Dhakal

Ciovati

Gurevich

2020

Phys. Rev. Accel. Beams

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Magnetic flux trapped during the cooldown of superconducting radio-frequency cavities through the transition temperature due to incomplete Meissner state is known to be a significant source of radio-frequency losses. The sensitivity of flux trapping depends on the distribution and the type of defects and impurities which pin vortices, as well as the cooldown dynamics when the cavity transitions from a normal to superconducting state. Here we present the results of measurements of the flux trapping sensitivity on 1.3 GHz elliptical cavities made from large-grain niobium with different purity for different cooldown dynamics and surface treatments. The results show that lower purity material results in a higher fraction of trapped flux. We present an overview of published data on the mean free path and frequency dependence of the trapped flux sensitivity which shows a significant scatter which highlights the complexity of the pinning phenomenon on a bulk superconductor with a large curved surface. We discuss contributions of different physical mechanisms to rf losses resulting from oscillations of flexible vortex segments driven by weak rf fields. In particular, we address the dependence of the rf losses on the mean free path in the cases of sparse strong pinning defects and collective pinning by many weak defects for different orientations of the vortex with respect to the inner cavity surface. This analysis shows that the effect of the line tension of vortices is instrumental in the physics of flux trapping and rf losses, and theoretical models taking into account different pinning strength and geometry of flexible pinned vortex segments can provide a good qualitative description of the experimental data.

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Section: Comparison With Published Data and Theoretical Modelssupporting

confidence: 89%

Flux expulsion in niobium superconducting radio-frequency cavities of different purity and essential contributions to the flux sensitivity

Dhakal

Ciovati

Gurevich

2020

Phys. Rev. Accel. Beams

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“…While recent advances in SRF cavity fabrication, especially the novel technique of Nitrogen doping and Nitrogen infusion [86][87][88], have significantly improved the properties of SRF cavities, the microscopic mechanism responsible for this improvement is yet unknown. Nitrogen infused cavity surfaces can perhaps be thought of as a layered superconductor, with a dirty superconductor on top acting like a "slow" superconductor and suppressing vortex nucleation [44,79].…”

Section: Discussionmentioning

confidence: 99%

Time-dependent Ginzburg-Landau treatment of rf magnetic vortices in superconductors: Vortex semiloops in a spatially nonuniform magnetic field

Oripov

Anlage

2020

Phys. Rev. E

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We apply time-dependent Ginzburg Landau (TDGL) numerical simulations to study the finite frequency electrodynamics of superconductors subjected to intense rf magnetic field. Much recent TDGL work has focused on spatially uniform external magnetic field and largely ignores the Meissner state screening response of the superconductor. In this work, we solve the TGDL equations for a spatially non-uniform magnetic field created by a point magnetic dipole in the vicinity of a semiinfinite superconductor. A novel two-domain simulation is performed to accurately capture the effect of the inhomogeneous applied fields and the resulting screening currents. The creation and dynamics of vortex semiloops penetrating deep into the superconductor domain is observed and studied, and the resulting third-harmonic nonlinear response of the sample is calculated. The effects of slow order parameter dynamics and point-like defects on vortex semi-loop behaviour is also studied. This simulation method will assist our understanding of the limits of superconducting response to intense rf magnetic fields.

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“…Internal toroid surface Pickup and detection cavity The use of superconducting wires allows R t to be as small as few nΩ (the minimum RF surface resistance of type II superconductors [30]), or at worst as large as mΩ (the nominal low-temperature resistance of quenched NbTi wires [31]). We expect the resistance will be somewhat larger than nΩ, as the wires operate in the vortex state and harbor toroidal magnetic flux tubes.…”

Section: External Toroid Surfacementioning

confidence: 99%

Axion production and detection with superconducting rf cavities

et al. 2019

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We propose a novel design of a laboratory search for axions based on photon regeneration with superconducting RF cavities. Our particular setup uses a toroid as a region of confined static magnetic field, while production and detection cavities are positioned in regions of vanishing external field. This permits cavity operation at quality factors of Q ∼ 10 10 − 10 12 . The limitations due to fundamental issues such as signal screening and back-reaction are discussed, and the optimal sensitivity is calculated. This experimental design can potentially probe axion-photon couplings beyond astrophysical limits, comparable and complementary to next generation optical experiments.

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Effect of interstitial impurities on the field dependent microwave surface resistance of niobium

Cited by 51 publications

References 30 publications

Flux expulsion in niobium superconducting radio-frequency cavities of different purity and essential contributions to the flux sensitivity

Flux expulsion in niobium superconducting radio-frequency cavities of different purity and essential contributions to the flux sensitivity

Time-dependent Ginzburg-Landau treatment of rf magnetic vortices in superconductors: Vortex semiloops in a spatially nonuniform magnetic field

Axion production and detection with superconducting rf cavities

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