Investigation of spatial spin polarization of 87Rb and 129Xe atomic ensemble pumped by Gaussian beam in a miniature nuclear magnetic resonance gyroscope

The spin polarization of 87Rb and 129Xe atomic ensemble has great impact on the signal intensity of a nuclear magnetic resonance gyroscope. The coupled spin polarization modelling process for 87Rb and 129Xe atoms ensemble is presented in detail. Three dimensional spatial distribution of the spin polarization field is obtained by numerical solution and is in good agreement with the experiment results. Influencing factors including temperature, power and detuned frequency of the pumping laser, average collision times of anti-relaxation coatings and partial pressure of gas composition are investigated. The work presents an indirect method to estimate the average collision times given the Xe polarization with different temperatures. It is found the average collision times of the 129Xe atoms with the inner surface of a bare glass cell of 3×3×3mm3 can reach up to about 2.7×105 times. It is also found that the pumping frequency corresponding to the maximum polarization of the Xe atoms polarized by spin exchange of Rb atoms is not consistent with the D1 line of the 87Rb atom when the temperature of the cell is above a certain temperature, but is detuned at a certain frequency. Quantitative analysis of the effect of anti-relaxation coatings on the spin polarization suggests that the appropriate average number of collisions of the Rb atoms with the inner surface of the cell is about 1500 times.