CN105651649A - Real-time online atomic density measuring method suitable for atom magnetometer - Google Patents

Abstract

The invention discloses a real-time online atomic density measuring method suitable for an atom magnetometer. The method comprises the specific steps that an alkali metal air chamber of the atom magnetometer is firstly heated; then the pumping light power is reduced, and a direct-current magnetic field is applied a coil, in the direction z, of the atom magnetometer; then sine wave field sweeping and data collecting of the atom magnetometer in the direction y are completed through a ZI lock-in amplifier; then the output signal of the ZI lock-in amplifier and the magnetic resonance line width of the atom magnetometer are subjected to fitting through a Lorenz curve; finally, the alkali metal atom density of the atom magnetometer is calculated. According to the method, the blank that in the prior art, no fast and effective real-time online atom density measuring method is filled in, and theoretical guidance and reference are provided for improving of the sensitivity of the atom magnetometer.

Description

A kind of atomic density real-time online measuring method suitable in atom magnetometer

Technical field

It is contemplated that propose a kind of atomic density real-time online measuring method suitable in atom magnetometer, belong to optical detection, spectrum analysis, density detection technical field.

Background technology

Based on magnetic field, part is widely present in nature, and field detecting device has high researching value as a kind of instrument understanding natural basis. The urgent needs of highly sensitive field detecting device is promoted generation and the development of ultra-high sensitive atom magnetometer. According to up-to-date progress, optical pumping atom magnetometer, start to show the susceptiveness to Exceedingly feeble magnetic field detection.

Atom magnetometer is mainly made up of four big systems: light-source system, magnetic shield and magnetic generation systems, heating system and sensitive gauge outfit (alkali metal air chamber). Owing to atom magnetometer has potential using value extremely widely, therefore, it becomes the heat subject that numerous scholars fall over each other to study. In these researchs, the research measured for atomic density in alkali metal air chamber relates to very few. Zou Sheng et al. proposes the realtime on-line monitoring method and device that alkali metal mixture ratio controls suitable in the alkali metal air chamber course of processing. The method and device are only applicable to the course of processing and monitor roughly the ratio of alkali metal mixture, it is impossible to carry out accurate density measure.

At present, about directly utilizing the method that atom magnetometer device itself completes the accurately and quickly atomic density of real-time online measuring alkali metal plenum interior, not disclosed report.

Summary of the invention

Goal of the invention: directly affecting atomic spin this problem of gaussmeter sensitivity for atomic density, the present invention is based on atom magnetometer itself, it is proposed to a kind of atomic density real-time online measuring method theoretical based on magnetic resonance live width; To fill up the prior art blank without atomic density real-time online measuring method fast and effectively, and theoretical direction and reference can be provided for atom magnetometer sensitivity enhancement.

Technical scheme: for achieving the above object, the technical solution used in the present invention is:

Using the magnetic resonance live width of atom magnetometer as magnetic field function, describing magnetic resonance live width by the full width at half maximum of Lorentz curve, formula is as follows:

In formula: �� �� is magnetic resonance live width, I is nucleon angular momentum (for potassium atom, I=3/2), R_SEFor the mutual collision relaxation that spins,For planck constant, g_SFor the Lande factor of electronics, ��_BFor Bohr magneton, B is magnetic field, ��^eFor electronic rotating magnetism ratio, q is core deceleration parameter (under high magnetic field environments, q=4), and i represents imaginary part.

The known magnetic resonance live width of through type (1) and magnetic field dependence; As it is shown in figure 1, under a certain temperature conditions, magnetic resonance live width increases with the increase in magnetic field, and after magnetic field increases to a certain value, magnetic resonance live width will tend towards stability, and change hardly. In Fig. 1, when temperature is lower than 195 DEG C, to obtain accurate magnetic resonance live width, magnetic field needs at more than 3000nT; When temperature is higher than 195 DEG C, to obtain accurate magnetic resonance live width, magnetic field needs at more than 5000nT.

Based on above-mentioned analysis, we can adopt gaussmeter parameter to describe magnetic resonance live width, such as formula (2) and formula (3):

$\mathrm{\Δ}\mathrm{\υ}=\frac{1}{{\mathrm{\πT}}_2}=\frac{R_{OP}}{4\mathrm{\π}}+\frac{R_{SE}{R}_{SD}}{R_{OP}\mathrm{\π}}G({\mathrm{\ω}}_0,R_{SE})---\left(2\right)$

$G({\mathrm{\ω}}_0,R_{SE})=\mathrm{Re}\[\frac{R_{SE}+4{\mathrm{i\ω}}_0^2/{\mathrm{\π\υ}}_{HF}}{5R_{SE}+8{\mathrm{i\ω}}_0^2/{\mathrm{\π\υ}}_{HF}}\]---\left(3\right)$

In formula: T₂For T2, R_OPFor pumping rate, R_SDRelaxation rate, �� is destroyed for spin₀For Zeeman transition frequency, Re represents real part, ��_HFFor ground state hyperfine splitting.

It is known that magnetic resonance live width is limited to the mutual collision relaxation rate of spin under big magnetic field environment; When pumping auroral poles is weak, spin polarizability P < < 1, convolution (2) and formula (3), it is possible to magnetic resonance live width is expressed as:

$\mathrm{\&Delta;}\mathrm{\&upsi;}=\frac{R_{SE}}{8\mathrm{\&pi;}}---\left(4\right)$

$R_{SE}={\mathrm{n\&sigma;}}_{SE}\sqrt{\frac{8K_{B}T}{\mathrm{\&pi;}M}}---\left(5\right)$

In formula: n is the alkali metal atom density of atom magnetometer, ��_SEFor the mutual collision cross-section that spins (for potassium atom, ��_SE=1.8 �� 10^-14cm²), K_BFor Boltzmann constant, T is temperature, and M is the reduced mass of alkali metal atom,M is the quality of alkali metal atom. When temperature is risen to 190 DEG C by 140 DEG C,Vary less.

Formula (4) and formula (5) are integrated, it is possible to obtain formula (6):

$n=\frac{8\mathrm{\&pi;}\mathrm{\&Delta;}\mathrm{\&upsi;}}{{\mathrm{\&sigma;}}_{SE}\sqrt{\frac{8K_{B}T}{\mathrm{\&pi;}M}}}---\left(6\right)$

Based on above-mentioned analysis, the atomic density real-time online measuring method suitable in atom magnetometer provided by the invention, specifically include following steps:

(1) the alkali metal air chamber of atom magnetometer is heated to temperature T;

(2) reduce pumping luminous power, and apply a D.C. magnetic field to the z directional coils of atom magnetometer;

(3) output port of the y directional coils of atom magnetometer with ZI (ZurichInstruments) lock-in amplifier is connected, sinusoidal wave field sweep and the data acquisition in atom magnetometer y direction is completed by ZI lock-in amplifier, it is sinusoidal wave field sweep frequency that the output signal of ZI lock-in amplifier is designated as f (x), x;

(4) by the magnetic resonance live width of the output signal of Lorentz curve matching ZI lock-in amplifier and atom magnetometer, fitting formula is as follows:

$f\left(x\right)=\frac{a}{\sqrt{{(x-b)}^2+{\left(\frac{\mathrm{\&Delta;}\mathrm{\&upsi;}}{2}\right)}^2}}+c$

Wherein: a is fitting coefficient, b is the resonant frequency of alkali metal atom, and �� �� is the magnetic resonance live width of atom magnetometer;

(5) equation below is adopted to calculate the alkali metal atom density of atom magnetometer:

$n=\frac{8\mathrm{\&pi;}\mathrm{\&upsi;}}{{\mathrm{\&sigma;}}_{SE}\sqrt{\frac{8K_{B}T}{\mathrm{\&pi;}M}}}$

In formula: n is the alkali metal atom density of atom magnetometer, ��_SEFor the mutual collision cross-section that spins, K_BFor Boltzmann constant, M is the reduced mass of alkali metal atom,M is the quality of alkali metal atom.

Concrete, in described step (1), reduce pumping luminous power to 30��100 �� W.

Concrete, in described step (1), apply the D.C. magnetic field of 3000��5000nT to the z directional coils of atom magnetometer.

Beneficial effect: the atomic density real-time online measuring method suitable in atom magnetometer provided by the invention, has the advantage that 1, fills up and lack atomic density fast and effectively and realize the blank of On-line Measuring Method; 2, assess atomic density for atom magnetometer and effective reference is provided; 3, provide safeguard for lifting atom magnetometer sensitivity.

Accompanying drawing explanation

Fig. 1 is magnetic resonance live width and magnetic field dependence;

Fig. 2 is atomic density real-time online measuring device in atom magnetometer, wherein: 1 is reflecting mirror one;2 is beam expanding lens; 3 is the polarizer; 4 areWave plate; 5 is Three-Dimensional Magnetic coil; 6 is the polarizer; 7 is beam expanding lens; 8 is reflecting mirror two; 9 is detection laser; 10 is magnetic shield bucket; 11 is functional generator; 12 is computer; 13 is ZI lock-in amplifier; 14 is alkali metal air chamber; 15 is PBS; 16 is balanced detector; 17 is reflecting mirror three; 18 is baking box; 19 is optically pumped laser;

Fig. 3 is the experimental result at 140 DEG C.

Detailed description of the invention

With potassium atom magnetic strength be calculated as example illustrate utilization originally send measurement alkali metal air chamber in atomic density number.

It is illustrated in figure 2 a kind of atomic density real-time online measuring device suitable in atom magnetometer, the structure identical with prior art employing; Measuring method comprises the steps:

(1) optical path adjusting and line: light path shown in accompanying drawing description 2 carries out finely regulating and wiring;

(2) system prepares: open electric heating system, heats alkali metal plenum interior to 140 DEG C;

(3) start test: pumping luminous power is reduced to 30 �� W, apply 3000nT D.C. magnetic field at z directional coils; Exported, to y direction, the sinusoidal wave field sweep that an amplitude is 5nT by ZI lock-in amplifier, and field sweep frequency range is 11KHz to 26KHz; Meanwhile, by ZI lock-in amplifier data acquisition.

(4) data process: use output signal and the frequency of Lorentz curve matching lock-in amplifier:

$f\left(x\right)=\frac{a}{\sqrt{{(x-b)}^2+{\left(\frac{\mathrm{\&Delta;}\mathrm{\&upsi;}}{2}\right)}^2}}+c$

(5) such as result such as shown in Figure of description 3, when 140 DEG C, using side of the present invention to carry out real-time online density measure, obtained density result is 0.49 �� 10¹³cm^-3��

The above is only the preferred embodiment of the present invention; it is noted that, for those skilled in the art; under the premise without departing from the principles of the invention, it is also possible to make some improvements and modifications, these improvements and modifications also should be regarded as protection scope of the present invention.

Claims (3)

1. the atomic density real-time online measuring method being applicable to atom magnetometer, it is characterised in that: comprise the steps:

(1) the alkali metal air chamber of atom magnetometer is heated to temperature T;

(2) reduce pumping luminous power, and apply a D.C. magnetic field to the z directional coils of atom magnetometer;

(3) the y directional coils of atom magnetometer is connected with the output port of ZI lock-in amplifier, sinusoidal wave field sweep and the data acquisition in atom magnetometer y direction is completed by ZI lock-in amplifier, it is sinusoidal wave field sweep frequency that the output signal of ZI lock-in amplifier is designated as f (x), x;

(4) by the magnetic resonance live width of the output signal of Lorentz curve matching ZI lock-in amplifier and atom magnetometer, fitting formula is as follows:

$f\left(x\right)=\frac{a}{\sqrt{{(x-b)}^2+{\left(\frac{\mathrm{\&Delta;}\mathrm{\&upsi;}}{2}\right)}^2}}+c$

Wherein: a is fitting coefficient, b is the resonant frequency of alkali metal atom, and �� �� is the magnetic resonance live width of atom magnetometer;

(5) equation below is adopted to calculate the alkali metal atom density of atom magnetometer:

$n=\frac{8\mathrm{\&pi;}\mathrm{\&Delta;}\mathrm{\&upsi;}}{{\mathrm{\&sigma;}}_{SE}\sqrt{\frac{8K_{B}T}{\mathrm{\&pi;}M}}}$

In formula: n is the alkali metal atom density of atom magnetometer, ��_SEFor the mutual collision cross-section that spins, K_BFor Boltzmann constant, M is the reduced mass of alkali metal atom,M is the quality of alkali metal atom.

2. the atomic density real-time online measuring method suitable in atom magnetometer according to claim 1, it is characterised in that: in described step (1), reduce pumping luminous power to 30��100 �� W.

3. the atomic density real-time online measuring method suitable in atom magnetometer according to claim 1, it is characterised in that: in described step (1), apply the D.C. magnetic field of 3000��5000nT to the z directional coils of atom magnetometer.