Characterization of Properties of 325-MHz Half-Wave Superconducting Resonators at Low Microwave Field Amplitudes

A prototype of the 325-MHz niobium half-wave coaxial resonator (\(\beta = 0.21\)) is developed, built, and tested at low microwave field amplitudes. Electromagnetic properties of the prototype in the superconducting state are investigated in the continuous wave regime and the damping regime using a highly stable radio-frequency (RF) generator and power detectors. The experimental data on the resonator’s response in the superconducting state are used to calculate its most important characteristics—the intrinsic Q value and the accelerating field. The experimentally measured Q value of the prototype is \({{Q}_{0}} = (3.5 \pm 0.1) \times {{10}^{8}}\) at input powers of up to +20 dBm.