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Title: Role of thermal resistance on the performance of superconducting radio frequency cavities

Journal Article · · Physical Review Accelerators and Beams
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Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF) cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q0(Bp) curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. In conclusion, these results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q0(Bp).

Research Organization:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC05-06OR23177
OSTI ID:
1346088
Alternate ID(s):
OSTI ID: 1345904
Report Number(s):
JLAB-ACC-16-2350; DOE/OR/-23177-3931; PRABCJ; 032003
Journal Information:
Physical Review Accelerators and Beams, Journal Name: Physical Review Accelerators and Beams Vol. 20 Journal Issue: 3; ISSN 2469-9888
Publisher:
American Physical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 7 works
Citation information provided by
Web of Science

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  • Kneisel, P.; Ciovati, G.; Dhakal, P.
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journal February 2015
Imaging of the Surface Resistance of an SRF Cavity by Low-Temperature Laser Scanning Microscopy journal June 2013
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Effect of low-temperature baking on the radio-frequency properties of niobium superconducting cavities for particle accelerators journal August 2004
Decrease of the surface resistance in superconducting niobium resonator cavities by the microwave field journal March 2014
Thermal contact resistance at the Nb/Cu interface as a limiting factor for sputtered thin film RF superconducting cavities journal November 2015

Cited By (2)

Fabrication and Vertical Test Experience of the European X-ray Free Electron Laser 3.9 GHz Superconducting Cavities text January 2017
Revealing the role of nitrogen on hydride nucleation and stability in pure niobium using first-principles calculations journal October 2018

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