Abstract
The transverse relaxation time τ2 of the built-in alkali metal magnetometer is an important parameter to characterize its performance and the working state of the nuclear magnetic resonance (NMR) oscillator system. The method we propose to measure τ2 is to apply the frequency-scanning magnetic fields along the x-axis and obtain τ2 from the 3 dB bandwidth of the measured x-axis amplitude–frequency response curve of the magnetometer. We give a detailed and rigorous theoretical derivation by using the perturbation-iteration method to demonstrate the rationality of this measuring method. Then, both the actual experiment and the simulation experiment results are presented to verify the validity and good accuracy of the method. All the sampled frequencies in the scanning range should be far away from both the 129Xe and 131Xe NMR frequencies, to avoid introducing any influence on the nuclear spins; therefore, this method can provide a non-interference way for measurement of τ2, helping us monitor the NMR oscillator system’s state under normal operating conditions.
Highlights
The alkali metal atomic magnetometer1,2 uses the coherent precession of the spin polarization to measure the weak magnetic field with pretty high sensitivity
The small and low-frequency magnetic field signal in the xy-plane produced by the limited number of precession nuclear spins in the cell can be measured by utilizing the sensitive in situ alkali metal atomic magnetometer, without the need for an external magnetometer
The sensitivity of the magnetometer is dependent on the spin-coherence dissipation properties of the alkali metal atomic spins in the vapor cell, evaluated by the transverse spin relaxation time τ2.14 The mechanisms of the spin relaxation are related to a variety of environmental conditions, such as collisions with the noble gas and buffer gas,15 alkali metal–alkali metal interactions,16 cell wall collisions,17 and inhomogeneities in the external magnetic fields18 and laser fields
Summary
The alkali metal atomic magnetometer uses the coherent precession of the spin polarization to measure the weak magnetic field with pretty high sensitivity. The small and low-frequency magnetic field signal in the xy-plane produced by the limited number of precession nuclear spins in the cell can be measured by utilizing the sensitive in situ alkali metal atomic magnetometer, without the need for an external magnetometer. The sensitivity of the magnetometer is dependent on the spin-coherence dissipation properties of the alkali metal atomic spins in the vapor cell, evaluated by the transverse spin relaxation time τ2.14 The mechanisms of the spin relaxation are related to a variety of environmental conditions, such as collisions with the noble gas and buffer gas, alkali metal–alkali metal interactions, cell wall collisions, and inhomogeneities in the external magnetic fields and laser fields.. As the transverse relaxation time τ2 of the built-in alkali metal magnetometer is an important parameter to characterize its performance and the working state of the NMR oscillator system, and in order to monitor the working state of the NMR oscillator system while the NMR oscillator system is functioning normally, in this paper, we present a non-interference method for measurement of transverse relaxation time of its built-in alkali metal magnetometer
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