Note: Radio frequency surface impedance characterization system for superconducting samples at 7.5 GHz.

Area of Science:

• Superconducting materials science
• Radio frequency (RF) engineering
• Low-temperature physics

Background:

• Accurate characterization of radio frequency (RF) surface impedance is crucial for superconducting devices.
• Existing methods may have limitations in sensitivity, sample size, or operating conditions.
• Development of novel measurement systems is needed for advanced superconducting material research.

Purpose of the Study:

• To develop and present a novel radio frequency (RF) surface impedance characterization (SIC) system.
• To enable direct calorimetric RF surface impedance measurements on flat superconducting material samples.
• To demonstrate the system's utility with initial measurements on a bulk niobium sample.

Main Methods:

• Utilized a novel sapphire-loaded niobium cavity operating at 7.5 GHz.
• Employed direct calorimetric measurement techniques.
• Tested on 5 cm diameter disk samples, measuring the central 0.8 cm² area under specific temperature and RF field conditions.

Main Results:

• Successfully developed and operated the RF surface impedance characterization (SIC) system.
• Demonstrated capability for direct calorimetric measurements on bulk niobium.
• Measurements were performed at temperatures ranging from 2 to 20 K and RF magnetic fields up to 14 mT.

Conclusions:

• The novel sapphire-loaded niobium cavity system is a viable tool for RF surface impedance characterization.
• The system provides direct calorimetric measurements, offering valuable data for superconducting materials.
• Initial results on niobium validate the system's performance and potential for future research.