Review of Scientific Instruments
Superconducting radio-frequency (SRF) cavities are one of the fundamental building blocks of modern particle accelerators. To achieve the highest quality factors (1010–1011), SRF cavities are operated at liquid helium temperatures. Magnetic flux trapped on the surface of SRF cavities during cool-down below the critical temperature is one of the leading sources of residual RF losses. Instruments capable of detecting the distribution of trapped flux on the cavity surface are in high demand in order to better understand its relation to the cavity material, surface treatments and environmental conditions. We have designed, developed, and commissioned two high-resolution diagnostic tools to measure the distribution of trapped flux at the surface of SRF cavities. One is a magnetic field scanning system, which uses cryogenic Hall probes and anisotropic magnetoresistance sensors that fit the contour of a 1.3 GHz cavity. This setup has a spatial resolution ∼13μm in the azimuthal direction and ∼1 cm along the cavity contour. The second setup is a stationary, combined magnetic and temperature mapping system, which uses anisotropic magnetoresistance sensors and carbon resistor temperature sensors, covering the surface of a 3 GHz SRF cavity. This system has a spatial resolution of 5 mm close to the iris and 11 mm at the equator. Initial results show a non-uniform distribution of trapped flux on the cavities’ surfaces, dependent on the magnitude of the applied magnetic field during field-cooling below the critical temperature.
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in
Parajuli, I., Ciovati, G., & Delayen, J. R. (2022). High resolution diagnostic tools for superconducting radio frequency cavities. Review of Scientific Instruments, 93(11), 1-12, Article 113305.
and may be found at https://doi.org/10.1063/5.0117868.
Article States: "The data that support the findings of this study are available from the corresponding author upon reasonable request."
Original Publication Citation
Parajuli, I., Ciovati, G., & Delayen, J. R. (2022). High resolution diagnostic tools for superconducting radio frequency cavities. Review of Scientific Instruments, 93(11), 1-12, Article 113305. https://doi.org/10.1063/5.0117868
Parajuli, I.; Ciovati, G.; and Delayen, J. R., "High Resolution Diagnostic Tools for Superconducting Radio Frequency Cavities" (2022). Physics Faculty Publications. 699.