Method used for on-line measurement of density of alkali metal in atom magnetometer air chambers at SERF (spin-exchange relaxation free) states

Abstract

The invention discloses a method used for on-line measurement of density of alkali metal in atom magnetometer air chambers at SERF (spin-exchange relaxation free) states. According to the method, an atom magnetometer is provided with a weak background magnetic field and low frequency stage horizontal linear frequency modulated signals, a data collecting card is used for collecting response signals of the atom magnetometer in frequency sweep time; fast Fourier transform is adopted so as to obtain a magnetic resonance curve in a frequency domain, the resonance line width and the resonant frequency of the magnetic resonance curve are obtained via calculation; the background magnetic field is changed so as to obtain a plurality of resonance line widths and resonant frequencies, quadratic curve fitting of the resonance line widths and the resonant frequencies is carried out so as to obtain spin exchange time; and at last the density of alkali metal in atom magnetometer air chambers at the current temperature can be obtained via calculation. The method can be performed at maintained SERF states, on-line measurement of the density of alkali metal in the air chambers can be realized only using the SERF magnetometer; excellent frequency resolution ratio of linear frequency signals can be achieved at low frequency range (1kHz or lower); and the method is suitable for low frequency scanning range required by SERF magnetometer weak magnetic field.

Description

technical field [0001] The invention belongs to the field of measurement and analysis of key performance parameters of atomic magnetometers, and in particular relates to a method for online measurement of alkali metal density in a gas chamber of an atomic magnetometer in a SERF state. Background technique [0002] SERF (Spin-Exchange Relaxation-Free) Atomic Magnetometer is an instrument that works in the SERF state and utilizes the Zeeman effect of atomic spins to measure the magnetic field. The alkali metal gas chamber is the core sensitive element of the SERF atomic magnetometer, and the density of alkali metal atoms in it directly restricts the intrinsic sensitivity of the magnetometer. Therefore, it is of great significance to achieve accurate measurement of the density of alkali metal atoms in the closed gas chamber by using only the atomic magnetometer itself while maintaining the SERF state. [0003] Currently, laser absorption spectroscopy and Faraday optical rotati...

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Problems solved by technology

However, this method needs to apply a strong magnetic field (~1.2T), which may magnetize the magnetic shielding barrel of the atomic magnetometer and affect the magnetic shielding effect

In addition, both of these methods require the use of other devices and cannot work in the atomic magnetometer SERF state

Therefore, none of them can meet the needs of the SERF atomic magnetometer for online measurement of the atomic density of alkali metals.

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