Abstract
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.
Highlights
The Nuclear Magnetic Resonance Gyroscope (NMRG) is a rotation-speed sensor, which detects the angular rate by measuring a shift in the Larmor precession frequency of nuclear spins in an applied magnetic field.[1]
We present an average Rb polarization model to analyze the effects of temperature on the spin polarization of Rb and 129Xe in a NMRG with a low pump power
An average Rb polarization model is developed in order 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
Summary
The Nuclear Magnetic Resonance Gyroscope (NMRG) is a rotation-speed sensor, which detects the angular rate by measuring a shift in the Larmor precession frequency of nuclear spins in an applied magnetic field.[1] The NMRG itself is inherently immune to vibration, and has no moving parts.[2,3] such a measurement system can outperform other types of gyros for small, low-power applications.[4] The Northrop Grumman Corporation (NGC) uses a vertical cavity surface-emitting laser (VCSEL) to optically pump the alkali metal atoms, with an output laser power of the VCSEL below 2 mW. The spin polarization of alkali metal atoms and noble gases influence the magnetometer sensitivity and the SNR of the NMRG.
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