Document Type

Article

Publication Date

2024

DOI

10.3389/femat.2024.1339293

Publication Title

Frontiers in Electronic Materials

Volume

4

Pages

1339293 (1-12)

Abstract

The performance of superconducting radio-frequency Nb cavities at high radio-frequency (rf) fields in the absence of field emission can be limited by either a sharp decrease of the quality factor Q0(Bp) above peak surface magnetic fields Bp ∼100 mT or by a quench. We have measured Q0(Bp) at 2 K of several 1.3 GHz single-cell Nb cavities with different grain sizes, and with different ambient magnetic fields and cooldown rates below the critical temperature. Temperature mapping and a novel magnetic field mapping systems were used to find the location of “hot-spots” and regions of trapped magnetic flux. The use of a variable input coupler allowed further exploring the dissipative state. The results showed a remarkable thermal stability in some cavities with up to 200 W of rf power dissipation at 2 K, whereas other cavities quenched at much lower rf power. We observed a narrow distributions of the onset fields of hot-spots which were not affected by thermal cycling or by conditions which favor the formation of Nb hydrides. Furthermore, a poor correlation was found between the location of hot-spots and trapped vortices. We suggest that the totality of our experimental data can be explained by a sharp increase of the residual surface resistance above 120–140 mT due to the field-induced breakdown of a proximity-coupled metallic suboxide layer at the surface.

Rights

© 2024 Parajuli, Ciovati and Gurevich.

This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Data Availability

Article states: "The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation."

Original Publication Citation

Parajuli, I., Ciovati, G., & Gurevich, A. (2024). Magneto-thermal limitations in superconducting cavities at high radio-frequency fields. Frontiers in Electronic Materials, 4, 1-12, Article 1339293. https://doi.org/10.3389/femat.2024.1339293

ORCID

0000-0002-0873-2068 (Parajuli), 0000-0003-0759-8941 (Gurevich)

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