Fast calibration of magnetic field coils in miniaturized NMRGs from Rabi oscillation of nuclear spins

Abstract

We propose a fast and accurate method for the in situ calibration of the transverse coils in miniaturized nuclear magnetic resonance gyroscopes based on the Rabi oscillation of hyperpolarized gaseous 129Xe nuclear spins. In contrast to the conventional method based on the free induction decay initial amplitude of different pulse durations, this method circumvents the error introduced by the frequency detuning of the transverse driving field. We experimentally confirm that the accuracy of the calibration is influenced by the longitudinal relaxation time T1, the transverse relaxation time T2, and the magnitude of the transverse driving field B1. Through the numerical simulation of Bloch equations, we show that the behavior of My′ and Mz can be completely specified by two dimensionless quantities a and b, and we provide a ready-to-use selection criterion of b ≥ 24 for choosing the proper B1. By switching the embedded magnetometer into the longitudinal mode, we demonstrate the effectiveness and efficiency of our new calibration method. Finally, we examine the effectiveness of the selection criterion with our new calibration method. This method is expected to improve the authenticity of coil calibration and relaxation measurement in a more efficient way.