CERN Accelerating science

Article
Report number	arXiv:2304.14229
Title	Temperature measurement on copper surfaces for superconducting thin film cavity applications
Author(s)	Bianchi, Antonio (CERN) ; Vandoni, Giovanna (CERN) ; Venturini Delsolaro, Walter (CERN)
Publication	2023-09-27
Imprint	2023-04-27
Number of pages	12
In:	Meas. Sci. Technol. 35 (2024) 015901
DOI	10.1088/1361-6501/acfba2
Subject category	physics.ins-det ; Detectors and Experimental Techniques ; physics.acc-ph ; Accelerators and Storage Rings
Abstract	Superconducting radio-frequency (SRF) thin film cavities on copper substrates are employed in several particle accelerators. However, these SRF cavities historically featured a progressive performance degradation with the accelerating field that is still not completely understood. The degradation of cavity performance, which limits the use of this technology in accelerators where the real-estate gradient has to be maximized, is manifested by the presence of heat losses in the superconducting film. However, measuring the temperature on the outer surface of copper substrates is challenging due to the higher thermal conductivity of copper at low temperatures compared to niobium. This study describes how temperature variations on copper surfaces can be satisfactorily measured in view of superconducting thin film cavity applications at liquid helium temperatures. Furthermore, we explore how the thermal exchange between thermometers and copper surfaces, and thermometers and helium bath must be tuned with respect to each other in order to measure accurately temperature rises in the thin film. Our findings suggest that engineering the copper surfaces can improve heat transfer into the helium bath and potentially enhance the performance of thin film SRF cavities.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: © 2023-2025 The Author(s) (License: CC-BY-4.0)

Corresponding record in: Inspire