Final published version
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - High-Frequency Nonlinear Response of Superconducting Cavity-Grade Nb Surfaces
AU - Oripov, B.
AU - Bieler, T.
AU - Ciovati, G.
AU - Calatroni, S.
AU - Dhakal, P.
AU - Junginger, T.
AU - Malyshev, O.B.
AU - Terenziani, G.
AU - Valente-Feliciano, A.-M.
AU - Valizadeh, R.
AU - Wilde, S.
AU - Anlage, S.M.
PY - 2019/6/13
Y1 - 2019/6/13
N2 - Nb superconducting radio-frequency (SRF) cavities are observed to break down and lose their high-Q superconducting properties at accelerating gradients below the limits imposed by theory. The microscopic origins of SRF cavity breakdown are still a matter of some debate. To investigate these microscopic issues, temperature- and power-dependent local third-harmonic response is measured on bulk Nb and Nb thin-film samples using a novel near-field magnetic microwave microscope between 2.9 and 10 K and 2 and 6 GHz. Both periodic and nonperiodic response as a function of applied rf field amplitude are observed. We attribute these features to extrinsic and intrinsic nonlinear responses of the sample. The rf-current-biased resistively shunted junction (RSJ) model can account for the periodic response and fits very well to the data using reasonable parameters. The nonperiodic response is consistent with vortex semiloops penetrating into the bulk of the sample once sufficiently high rf magnetic field is applied and the data can be fit to a time-dependent Ginzburg-Landau (TDGL) model of this process. The fact that these responses are measured on a wide variety of Nb samples suggests that we are capturing the generic nonlinear response of air-exposed Nb surfaces.
AB - Nb superconducting radio-frequency (SRF) cavities are observed to break down and lose their high-Q superconducting properties at accelerating gradients below the limits imposed by theory. The microscopic origins of SRF cavity breakdown are still a matter of some debate. To investigate these microscopic issues, temperature- and power-dependent local third-harmonic response is measured on bulk Nb and Nb thin-film samples using a novel near-field magnetic microwave microscope between 2.9 and 10 K and 2 and 6 GHz. Both periodic and nonperiodic response as a function of applied rf field amplitude are observed. We attribute these features to extrinsic and intrinsic nonlinear responses of the sample. The rf-current-biased resistively shunted junction (RSJ) model can account for the periodic response and fits very well to the data using reasonable parameters. The nonperiodic response is consistent with vortex semiloops penetrating into the bulk of the sample once sufficiently high rf magnetic field is applied and the data can be fit to a time-dependent Ginzburg-Landau (TDGL) model of this process. The fact that these responses are measured on a wide variety of Nb samples suggests that we are capturing the generic nonlinear response of air-exposed Nb surfaces.
KW - Accelerating gradient
KW - High-frequency nonlinear response
KW - Microwave microscopes
KW - Non-linear response
KW - Resistively shunted junctions
KW - Superconducting cavities
KW - Superconducting properties
KW - Superconducting radio frequency
U2 - 10.1103/PhysRevApplied.11.064030
DO - 10.1103/PhysRevApplied.11.064030
M3 - Journal article
VL - 11
JO - Physical Review Applied
JF - Physical Review Applied
SN - 2331-7019
IS - 6
M1 - 064030
ER -