Effects of temperature on Rb and 129Xe spin polarization in a nuclear magnetic resonance gyroscope with low pump power

We propose an average Rb polarization model to analyze the influence of temperature on the spin polarization of Rb and 129Xe in a Nuclear Magnetic Resonance Gyroscope (NMRG) with low pump power. This model is essentially based on summing the Rb spin polarization along the direction of the pump beam and dividing the result by the cell length. We experimentally study the spin polarization of Rb and 129Xe atoms as a function of the cell temperature at low values of the pump power. The experimental results and the values calculated with the average Rb polarization model are in good agreement for both Rb and 129Xe. The spin polarization of Rb atoms decreases with increasing cell temperature, with a decreasing trend which is rapid at temperatures below 110 °C, and slower at temperatures above 110 °C. The experimental values of the 129Xe polarization, obtained with a pump power of 1 mW, first increase to a maximum P 129Xe−ave = 0.66 % at 118 °C, and then decreases as the temperature increases. Increasing the power of the pump beam shifts the temperature maximum to a higher value. Our model is suitable for the analysis of Rb and 129Xe polarization at high temperature and low pump power, i.e. when the power of the pump beam is completely absorbed within a few millimeters of the front window of the cell. Therefore, the present model can provide theoretical support for the improvement of the Signal-to-Noise-Ratio (SNR) of the NMRG, and to determine its optimal working temperature.