A Novel Method of Measuring Spin Polarization of Noble-Gas Atoms in Nuclear Magnetic Resonance Gyroscopes

We propose a precise and efficient method for measuring the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">129</sup>Xe polarization that is applicable to weak magnetic field, low-pressure and low-temperature scenarios where Van der Waals forces are dominant in the spin-exchange collisions of noble-gas and alkali-metal atoms based on the magnetometer in a nuclear magnetic resonance gyroscope system. We also develop an optimized method for measuring the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">129</sup>Xe relaxation over a wide temperatures, which reverses the direction of the main magnetic field to flip the quantization axis and fits the free induction decay signals for obtaining the transversal and longitudinal relaxation time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">129</sup>Xe, simultaneously. Using this accurate and stable method, the dependence of the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">129</sup>Xe relaxation on the cell temperature and the optical pumping rate is studied efficiently, and the depolarization relaxation rate Γ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_n</i> is measured. Thus, the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">129</sup>Xe polarization <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> is derived from the measured <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and Γ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub>, with an error of 6%. This method is meaningful in quick tests and diagnosis online, which helps improve the sensitivity of the nuclear magnetic resonance gyroscope system.