A Resonant Cavity Based on Capacitively Loaded Coaxial Structure for Overhauser Magnetic Sensors

Abstract

The RF excitation coil is an important component of the Overhauser magnetic sensor, which determines whether the dynamic nucleation polarization of the free radical solution can be carried out smoothly. A capacitance-loaded resonant cavity structure is proposed as the RF excitation of the Overhauser magnetic sensor. The structure and equivalent circuit of the capacitance-loaded coaxial resonant cavity are analyzed and improved on the conventional structure, and the resonant frequency is verified to be consistent with the excitation frequency of the free radical solution by modeling and simulation using COMSOL software. The resonant cavity solid was fabricated, and the cavity was tested by using a vector network analyzer. The results show that the initial resonance point of the homemade resonant cavity is 60.55MHz, and the frequency point can be adjusted to 60.7MHz by adjusting the loading capacitor and tuning capacitor; the resonant cavity return loss S11 is about -19dB, and the quality factor Q value is about 506.