Asymmetry of EPR signal response in nuclear magnetic resonance gyroscope

Abstract

The spin relaxation time of alkali atoms in nuclear magnetic resonance gyroscope is usually on the order of 10<sup>–5</sup> s, which is much less than that in atomic magnetometers. The response of electron paramagnetic resonance signals of atoms with short relaxation time is asymmetric in different directions under oscillating magnetic fields, which makes the measurement results of atomic transverse relaxation time and Larmor frequency different. In this work this phenomenon is analyzed based on Bloch equation theory and the theoretical correction is given. The shorter the relaxation time, the greater the differences of the response intensity and resonance frequency of the electron paramagnetic resonance signal under different magnetic field directions will be. Using this property, the transmission delay time of the system can be measured accurately. In this paper proposed is a method of measuring transverse relaxation time based on the difference between signal phases in <i>X</i>-axis direction and <i>Y</i><italic/>-axis direction, which can accurately and quickly measure very short transverse relaxation time. The difference between the half-width fitting method and the phase measurement method is compared by measuring the transverse relaxation times of <sup>87</sup>Rb atoms under different magnetic field intensities. The half-width fitting method is greatly affected by the transmission delay time and has its measurement limit. The phase measurement method is greatly affected by the angle of the probe light, but the measurement range is wider and the anti-magnetic interference ability is stronger.