Signatures of enhanced superconducting properties in niobium cavities
Superconducting radio-frequency (SRF) niobium cavities are critical for modern particle accelerators, as well as for advancing superconducting quantum systems and enabling ultrasensitive searches for new physics. In this work, we report a systematic observation of an anomalous frequency dip in Nb cavities, which occurs at temperatures just below the critical temperature (𝑇𝑐 ), indicative of enhanced superconducting properties at 𝑇 ≪ 𝑇𝑐. The magnitude of this dip is strongly correlated with the rf surface resistance, impurity distribution near the surface, and 𝑇𝑐 . Additionally, we report measurements of the coherence peak in the ac conductivity of two Nb SRF cavities processed using distinct methods. By comparing recent theories developed to model this experimental data, we show that the frequency-dip feature, larger coherence peak height, and reduction in the temperature-dependent surface resistance with rf current occur at minimal but finite levels of disorder.
- Research Organization:
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); USDOE Office of Science (SC), High Energy Physics (HEP)
- Grant/Contract Number:
- 89243024CSC000002; AC02-07CH11359; AC02-76SF00515
- OSTI ID:
- 1823520
- Report Number(s):
- FERMILAB--PUB-21-098-QIS-TD; oai:inspirehep.net:1852642; arXiv:2103.10601
- Journal Information:
- Physical Review Applied, Journal Name: Physical Review Applied Journal Issue: 5 Vol. 23; ISSN 2331-7019
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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