MgB₂ coating for 1.3 GHz Cu superconducting RF cavities

With a higher T_c and higher critical field H_c than Nb and many Nb compounds and alloys, MgB₂ shows promising potential for superconducting RF (SRF) cavities at around 20 K. We demonstrate significant progress in developing MgB₂-coated SRF cavities. MgB₂ films with thickness up to 5 um were coated on 1.3 GHz TESLA-type Cu RF cavities by hybrid physical-chemical vapor deposition (HPCVD). The mock cavities were manufactured in-through deep drawing techniques and heated conductively using a pair of clamshell resistive heaters. MgB₂ films grown on 1 cm × 1 cm Cu substrates attached on the inside wall of cavities show T_c up to 34 K, measured by AC susceptibility [1]. Further characterization using parallel-plate resonators demonstrated that the temperature dependence of the microwave surface resistance and penetration depth aligns with the BCS theory predictions.



[1] Ke Chen and Xiaoxing Xi, MgB₂ Coating by HPCVD for 1.3-GHz Superconducting RF Cavities, IEEE Trans. Appl. Supercond. 34, 3500405 (2024) https://doi.org/10.1109/TASC.2023.3347211