Document Type


Publication Date




Publication Title

Frontiers in Electronic Materials




1339293 (1-12)


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.


© 2024 Parajuli, Ciovati and Gurevich.

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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.


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