Document Type

Conference Paper

Publication Date




Publication Title

Proceedings of the 19th International Conference on RF Superconductivity



Conference Name

19th International Conference on RF Superconductivity, 30 June-05 July 2019, Dresden, Germany


The performance of high-purity, bulk niobium SRF cavities treated by chemical processes such as BCP or EP is limited by the so-called high-field Q-slope (HFQS). Several models and experimental studies have been proposed and performed over the years to understand the origin of these anomalous losses but a general consensus on what these origins are is yet to be established. In this contribution, we present the results from the RF tests of several 1.3 GHz single-cell cavities limited by the HFQS and tested using a variable input coupler. This allowed to maintain close to critical coupling even at high field and the data showed that the HFQS did not saturate and that in some cases a power dissipation of up to 200 W at 2 K could be sustained without quench.


Published by JACoW Publishing under the terms of the Creative Commons Attribution 3.0 International (CC BY 3.0) license. Any further distribution of this work must maintain attribution to the authors, the published article's title, publisher, and DOI.

Original Publication Citation

Ciovati, G., Gurevich, A. V., & Parajuli, I. P. (2019) Maximum performance of cavities affected by the high-field Q-slope (HFQS). In P. Michel, A. Arnold, & V. R. W. Schaa (Eds.), Proceedings of the 19th International Conference on RF Superconductivity (pp. 533-537). JACoW Publishing.


0000-0003-0759-8941 (Gurevich)