Note: Design and resonant condition measurement of the mushroom-shaped Al test cavity for critical magnetic field evaluation of superconducting thin-film sample

We designed a mushroom-shaped Al test cavity for measurement of the critical magnetic field at a radio frequency microwave with a frequency of 5.2 GHz. The characteristics of the Al test cavity are characterized toward the evaluation of the superconducting multilayer thin films under high-power radio frequency microwaves at cryogenic temperatures by the Nb-based cavity. We evaluated a target resonant frequency, the separations of neighboring modes, and the electromagnetic field distribution of the target mode. The calculated frequency change was in good agreement with that obtained experimentally.