Nonlinear Near-Field Microwave Microscope for RF Defect Localization in Superconductors

Tai, Tamin; Xi, X. X.; Zhuang, Chenggang; Mircea, Dragos I.; Anlage, Steven M.

doi:10.1109/tasc.2010.2096531

Cited by 14 publications

(29 citation statements)

References 13 publications

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“…In our experiment the localized harmonic response of superconductors is excited by a magnetic write head probe extracted from a commercial magnetic hard drive [11]. Based on the gap geometry of the magnetic write head probe, submicron resolution is expected.…”

Section: Introductionmentioning

confidence: 99%

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MgB2nonlinear properties investigated under localized high rf magnetic field excitation

Tai

Ghamsari

Tan

et al. 2012

Phys. Rev. ST Accel. Beams

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The high transition temperature and low surface resistance of MgB 2 attracts interest in its potential application in superconducting radio frequency accelerating cavities. However, compared to traditional Nb cavities, the viability of MgB 2 at high rf fields is still open to question. Our approach is to study the nonlinear electrodynamics of the material under localized rf magnetic fields. Because of the presence of the small superconducting gap in the band, the nonlinear response of MgB 2 at low temperature is potentially complicated compared to a single-gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two-band structure of MgB 2 , as well as extrinsic sources of nonlinearity, is an urgent requirement. A localized and strong rf magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [T. Tai et al., IEEE Trans. Appl. Supercond. 21, 2615(2011. MgB 2 films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that several possible mechanisms are responsible for this nonlinear response.

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Section: Introductionmentioning

confidence: 99%

“…Supercond. 21, 2615(2011. MgB 2 films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response.…”

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confidence: 99%

MgB2nonlinear properties investigated under localized high rf magnetic field excitation

Tai

Ghamsari

Tan

et al. 2012

Phys. Rev. ST Accel. Beams

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“…Our idea is to look at the active surface of SRF cavities with a very intense and localized magnetic field (on the order of the thermodynamic critical field of bulk Nb), and directly measure the local electromagnetic response in the cavity operating regime at low temperature [8]. Our method is to integrate a magnetic write head from a longitudinal recording hard drive [9] into a nearfield microwave microscope [10][11] and directly measure the local nonlinear response in the multi-GHz frequency regime at cryogenic temperatures. The microscope can study bulk samples from Nb cavities or any material of interest to the SRF community, such as MgB 2 thin films [12] [13].…”

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confidence: 99%

“…The probe shows third harmonic response only at excitation powers of 15 dBm and above. This is because the magnetic write head is made of ferrite which has hysteretic characteristics and generates background nonlinearity [10]. For measurement below T c , all curves (at temperature T 1 , T 2 , · · · , T 5 ) show a sharp P 3f onset from the noise floor of the spectrum analyzer and then follow a continuous increase of nonlinearity until a turnover at high excitation power.…”

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confidence: 99%

“…Defective regions which create quenches in SRF cavities are expected to be strong sources of nonlinear response. Up to this point localized nonlinear microwave response has only been measured from superconducting thin films [10] In our first experiment, we measure the third harmonic scalar power (P sample 3f ) that is generated by the bulk Nb sample due to local harmonic excitation at a fixed location. The third-harmonic power is studied because it is sensitive to the extrinsic properties (i.e.…”

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Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials

Tai

Ghamsari

Bieler

et al. 2014

Applied Physics Letters

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A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two new measurements are performed to demonstrate these capabilities with a novel near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high ResidualResistance-Ratio bulk Nb sample showing strong localized nonlinear response for the first time, with surface RF magnetic field B surf ace ∼ 10 2 mT. The second is a raster scanned harmonic response image on a high quality MgB2 thin film demonstrating a quench defect-free surface over large areas.Materials issues limit the ability to mass-produce bulk Nb Superconducting Radio Frequency (SRF) cavities with consistent high accelerating gradient performance. Much debate regarding this inconsistent performance has concluded that certain types of defects on the Nb cavity surface behave as a source of quenching in high RF magnetic fields [1] [2]. Quench occurs when the superconductor returns to the normal state in the presence of strong fields, thus limiting the utility of the entire SRF cavity. In addition it is widely observed that the quality factor (Q) of SRF cavities falls dramatically with increasing surface RF magnetic field, particularly as the quench field is approached [3]. A detailed microscopic understanding of this Q drop is lacking but is most likely related to the inevitable defects on the inner surface of bulk Nb cavities [1] [2]. These defects may be either nonsuperconducting or have lower critical temperature (T c ), making them sources of dissipation which interrupt the superconducting current flow [4]. Unfortunately, it is difficult to totally remove all of these defects even after sophisticated physical and chemical treatments. Because different defects each have their own quench limit, not all of the defects behave as sources of quenching under given cavity operation conditions. Therefore it is necessary to quantitatively understand the relation between physical defects and their individual electromagnetic properties such as local critical field.Currently, in order to isolate specific defects in SRF cavities, most measurements utilize a complete accelerator cavity [5] and image the quenching hot spots at high accelerating gradient via a thermometer array attached to the outside wall of the cavity [2]. Such measurements reveal the locations of quench sites only to within a few millimeters, far larger than the defect itself, making their unique identification difficult. Microscopic techniques have not been used in the past because traditionally it is difficult to create strong and localized RF magnetic fields at the cavity operating frequency (several GHz) [6][7]. Our idea is to look at the active surface of SRF cavities with a very intense and localized magnetic field (on the order of the thermodynamic critical field of bulk Nb), and directly measure the local electromagnetic response in the cavity operating regime a...

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Flux-pinning properties of nanocrystalline HfO₂ added YBa₂ Cu₃ O_7−δ superconductor

Rejith¹,

Vidya²,

Vipinlal³

et al. 2013

Phys. Status Solidi B

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The effect of addition of different weight percentages of nanocrystalline HfO2, synthesized through a modified combustion method in bulk coarse‐grained orthorhombic YBa2Cu3O7−δ powder was studied. The structure and microstructure of the samples examined by X‐ray diffraction (XRD) and scanning electron microscopy (SEM) showed the formation of a secondary phase YBa2HfO5.5 in the superconductor without deteriorating the superconducting properties. The variation of sintering temperature, density, critical transition temperature (Tc), magnetic field dependence of critical current density (Jc), and flux‐pinning force (Fp) of YBa2Cu3O7−δ having different proportions of YBa2HfO5.5 formed in the matrix were studied in detail. The samples showed a transition temperature (Tc) of ∼92 K and the self‐field critical current density (Jc) increases significantly up to an optimum value of 5.42 × 104 A cm−2 for 2 wt% addition of nano HfO2. The enhancement of the critical current density in the YBa2Cu3O7−δ‐HfO2 samples is attributed to the presence of the nonreacting YBa2HfO5.5 phase, formed due to the addition of HfO2 as artificial pinning center. The formation of YBa2HfO5.5 in YBa2Cu3O7−δ bulk superconductor also enhances the pinning force density from 3 × 106 to 30.4 × 106 N m−3 at 77 K.

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Nonlinear Near-Field Microwave Microscope for RF Defect Localization in Superconductors

Cited by 14 publications

References 13 publications

MgB2nonlinear properties investigated under localized high rf magnetic field excitation

MgB2nonlinear properties investigated under localized high rf magnetic field excitation

Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials

Flux-pinning properties of nanocrystalline HfO₂ added YBa₂ Cu₃ O_7−δ superconductor

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Nonlinear Near-Field Microwave Microscope for RF Defect Localization in Superconductors

Cited by 14 publications

References 13 publications

MgB2nonlinear properties investigated under localized high rf magnetic field excitation

MgB2nonlinear properties investigated under localized high rf magnetic field excitation

Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials

Flux-pinning properties of nanocrystalline HfO2 added YBa2 Cu3 O7−δ superconductor

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Flux-pinning properties of nanocrystalline HfO₂ added YBa₂ Cu₃ O_7−δ superconductor