New evidence for thermal boundary resistance effects in superconducting 6 GHz cavities

11th European Conference on Applied Superconductivity

Checchin, M.^1,2 ; Martinello, M.^1,2 ; Palmieri, V.^1,2 ; Rossi, A.A.^1 ; Stark, S.^1 ; Stivanello, F.^1 ; Thakur, R.K.^1,2,4 ; Vaglio, G.Yu.R.^3

Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, Legnaro, Italy^1

Universitä Degli Studi di Padova, Dipartimento di Fisica Ed Astronomia, Padova, Italy^2

CNR-SPIN, University of Napoli Federico II, Piazzale Tecchio 80, 80125, Italy^3

China Institute of Atomic Energy, China^4

关键词: Cavity optimization;    Kapitza resistance;    Measured values;    Superconducting accelerating cavities;    Superfluid transitions;    Temperature differences;    Thermal boundary;    Thermal boundary resistance;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/507/3/032053/pdf
DOI  :  10.1088/1742-6596/507/3/032053

来源: IOP

【 摘 要 】

Thermal boundary resistance and, more specifically, Kapitza resistance effects have been often considered as a possible source of "non ideal" superconducting accelerating cavity behavior, through the formation of a temperature difference between the inner cavity superconducting surface and the helium bath. However, in the present literature the general reported assessment is that such effects could be neglected, at least at low or moderate input power. In this communication we present new data on small test bulk Nb 6Ghz cavities, showing that when the cavity surface resistance (or the Q) is plotted as a function of the temperature at constant input power, a clear anomaly occurs at the Helium superfluid transition point Tλreflecting the abrupt change of the thermal boundary resistance at that temperature. The data analysis shows that this anomaly is consistent with the typically measured values of the thermal boundary (Kapitza) resistance. Implications on the cavity optimization strategy are finally discussed.