阅读说明：本技术 基于光泵核磁共振的三维线圈系数标定方法 (Three-dimensional coil coefficient calibration method based on optical pump nuclear magnetic resonance ) 是由 钟国宸 郭阳 刘华 李绍良 赵万良 于 2020-12-29 设计创作，主要内容包括：一种基于光泵核磁共振的三维线圈系数标定方法,通过将装有铯原子及缓冲气体的原子玻璃气室置于三维线圈中心,分别对三维线圈中任意一个或两个方向上的线圈施加电流并产生产生直流磁场并通过左旋圆偏振光照射原子气室,圆偏振光照射的方向与所施加直流磁场在同一平面,同时在垂直于直流磁场与圆偏振光平面的方向施加一频率固定的射频磁场,通过调整电流大小达到光泵核磁共振状态,此时透过原子气室的光会受到铯原子的最大调制,对出射光进行光电转换和解调后得到出射光的幅值,当获得最大幅值所对应的电流值时即实现线圈系数标定。本方法特点精度高、避免使用其它磁场测量仪器,同时具备操作简单、通用性好的优点,能够方便应用于核磁共振陀螺仪三维线圈的线圈系数测定。(A three-dimensional coil coefficient calibration method based on optical pump nuclear magnetic resonance is characterized in that an atomic glass air chamber filled with cesium atoms and buffer gas is arranged in the center of a three-dimensional coil, current is applied to the coil in any one or two directions in the three-dimensional coil respectively to generate a direct-current magnetic field, the atomic air chamber is irradiated by left-handed circularly polarized light, the irradiation direction of the circularly polarized light and the applied direct-current magnetic field are in the same plane, a radio-frequency magnetic field with fixed frequency is applied in the direction perpendicular to the direct-current magnetic field and the plane of the circularly polarized light, the optical pump nuclear magnetic resonance state is achieved by adjusting the current, at the moment, light penetrating through the atomic air chamber is maximally modulated by the cesium atoms, the amplitude of emergent light is obtained after photoelectric conversion and demodulation are carried out, and when the current value corresponding to the maximum amplitude. The method has the advantages of high precision, no need of using other magnetic field measuring instruments, simple operation and good universality, and can be conveniently applied to the coil coefficient determination of the three-dimensional coil of the nuclear magnetic resonance gyroscope.)

1. A three-dimensional coil coefficient calibration method based on optical pump nuclear magnetic resonance is characterized in that an atomic glass air chamber filled with cesium atoms and buffer gas is arranged in the center of a three-dimensional coil, current is respectively applied to coils in any one or two directions in the three-dimensional coil to generate a direct-current magnetic field, the atomic air chamber is irradiated by left-handed circularly polarized light, the direction of irradiation of the circularly polarized light and the applied direct-current magnetic field are in the same plane, a radio-frequency magnetic field with fixed frequency is applied in the direction perpendicular to the direct-current magnetic field and the plane of the circularly polarized light, the optical pump nuclear magnetic resonance state is achieved by adjusting the magnitude of the current, at the moment, the light penetrating through the atomic air chamber is subjected to the maximum modulation of the cesium atoms, the amplitude of emergent light is obtained after photoelectric conversion and demodulation are carried out, and when the current value corresponding to.

2. The method for calibrating the three-dimensional coil coefficient based on the optical pumping nuclear magnetic resonance as claimed in claim 1, wherein the optical pumping nuclear magnetic resonance state is as follows: frequency omega ═ gamma B of radio frequency magnetic field₀Wherein: gamma is the gyromagnetic ratio of cesium atoms, being a fixed constant, B₀The field strength of the DC magnetic field and the field strength B of the radio frequency magnetic field₁cosωt。

3. The method for calibrating the three-dimensional coil coefficient based on the optical pump nuclear magnetic resonance as claimed in claim 1, wherein the amplitude of the emergent light is obtained by performing photoelectric conversion and demodulation on the emergent light at the current value corresponding to the maximum amplitude, and when the amplitude is the maximum modulation point, the corresponding current value I satisfies ω ═ γ I λ, so as to obtain the coil coefficient λ of the coil in the corresponding direction.

4. The method for calibrating the three-dimensional coil coefficient based on the optical pump nuclear magnetic resonance as claimed in any one of claims 1 to 3, which is characterized by comprising the following steps:

x-axis direction coil coefficient lambda_xCalibration:

1.1) poling cesium atoms in the x-direction by the pumping direction from a pump laser source, and generating a magnetic field B parallel to the direction of the pump laser by applying a current to a Helmholtz coil of the x-axis parallel to the direction of the pump laser₀＝I_xλ_xWherein: i is_xReading the current value of the current applied to the coil by means of a multimeter, lambda_xIs the coil coefficient of the x-axis Helmholtz coil, and applies a radio frequency magnetic field B on the y-axis Helmholtz coil or the z-axis Helmholtz coil perpendicular to the direction of the pumping light₁cos ω t, where the radio frequency magnetic field frequency ω is a determined value;

1.2) increasing the current I gradually from zero_xSo that the magnetic field parallel to the direction of the pump laser corresponds to B₀Increasing until optical pump magnetic resonance occurs, wherein the intensity of transmitted light is modulated by cesium atoms at the frequency of the maximum amplitude of RF magnetic field frequency ω (γ B)₀Wherein: gamma is the gyromagnetic ratio of cesium atom, sine wave waveform obtained by detection of photoelectric detector is input into phase-locked amplifier and phase-locked with reference signal with frequency of omega to obtain amplitude of signal, and I is regulated_xThe output of the phase-locked amplifier is maximized, and the current I corresponding to the maximum signal amplitude is searched_xmaxReading the current value I applied to the coil at the moment by using a multimeter_xmaxCalculating to obtain corresponding coil coefficient

X coefficient of coil in y-axis direction_yCalibration:

2.1) polarization of Cs atoms in the x-direction in the pumping direction from the pump laser source, and applying a current I to the Helmholtz coil in the x-axis and Helmholtz coil in the y-axis simultaneously_x、I_yThen two orthogonal magnetic field vector sums are generatedWherein: current I applied to the coil_x、I_yRead out separately by a multimeter, in this case perpendicular to the magnetic field B₀Is applied with a radio frequency magnetic field B on a plane z-axis Helmholtz coil₁cos omegat, setting the frequency omega of the radio frequency magnetic field as a determined value;

2.2) constant Current I_xWhile not changing, the current I is gradually increased from zero_yUntil the optical pump magnetic resonance phenomenon is generated, the light intensity of the transmitted light is modulated by the cesium atoms at the frequency with the maximum amplitude of the radio frequency magnetic field frequency omega, wherein omega is gamma B₀Wherein: gamma is the gyromagnetic ratio of cesium atom, sine wave waveform obtained by detection of photoelectric detector is input into phase-locked amplifier and phase-locked with reference signal with frequency of omega to obtain amplitude of signal, and I is regulated_yThe output of the phase-locked amplifier is maximized, and the current I corresponding to the maximum signal amplitude is searched_ymaxReading the current value I applied to the coil at the moment by using a multimeter_ymaxCombining the coil coefficient lambda obtained in the step I_xCalculating to obtain corresponding coil coefficient

③ coil coefficient lambda in the z-axis direction_zIs calibrated with lambda_ySimilarly:

3.1) polarization of cesium atoms in the x-direction in the pumping direction from a pump laser source, when currents I are applied to the x-direction coil and the z-direction coil, respectively_x、I_zThe magnitude of the magnetic field generated at this time is the sum of two orthogonal magnetic field vectorsCurrent I applied to the coil_x、I_zCan be read out by a multimeter respectively and is perpendicular to the magnetic field B₀A radio frequency magnetic field B is applied to the planar y-direction coil₁cos omegat, setting the frequency omega of the radio frequency magnetic field as a determined value;

setting x-direction coilUpper current I_xIs a fixed value, and gradually increases the current I on the coil in the z direction from zero_zUntil the optical pump magnetic resonance phenomenon is generated, the light intensity of the transmitted light is modulated by the cesium atoms at the frequency with the maximum amplitude of the radio frequency magnetic field frequency omega, wherein omega is gamma B₀Wherein: gamma is the gyromagnetic ratio of cesium atom, sine wave waveform obtained by detection of photoelectric detector is input into phase-locked amplifier and phase-locked with reference signal with frequency of omega to obtain amplitude of signal, and I is regulated_zThe output of the phase-locked amplifier is maximized, and the current I corresponding to the maximum signal amplitude is searched_zmaxReading the current value I applied to the coil at the moment by using a multimeter_zmaxCombining the coil coefficient lambda obtained in the step I_xCalculating to obtain corresponding coil coefficient

5. An optical pumping nuclear magnetic resonance-based three-dimensional coil coefficient calibration device for implementing the method of any one of the preceding claims, comprising: set gradually pump laser light source, linear polarizer, lambda/4 wavelength optical lens in magnetism shielding section of thick bamboo side to and set gradually photoelectric detector and the lock-in amplifier in magnetism shielding section of thick bamboo side, wherein: the three-dimensional Helmholtz coil is assembled from inside to outside and then placed in the center of the magnetic shielding cylinder, the cesium atom air chamber is fixed in the center of the three-dimensional Helmholtz coil, laser generated by the pump laser source is sequentially converted into left-handed circularly polarized light through the linear polarizer and the lambda/4 wavelength optical lens, and emergent light of the left-handed circularly polarized light after being transmitted to the cesium atom air chamber in a space free light form is detected by the photoelectric detector and then demodulated by the phase-locked amplifier to obtain the amplitude of a photoelectric signal.

6. The apparatus according to claim 5, wherein the pump laser source is energized to generate laser light with a wavelength of 894.2 nm.

7. The apparatus for calibrating a three-dimensional coil coefficient based on optical pumping nuclear magnetic resonance as claimed in claim 5, wherein the cesium atom gas chamber is a square glass bubble filled with cesium atom gas and buffer gas, and has a size of 4 mm.

Technical Field

The invention relates to a technology in the field of nuclear magnetic resonance, in particular to a three-dimensional coil coefficient calibration method based on optical pump nuclear magnetic resonance.

Background

The nuclear magnetic resonance gyroscope has wide application prospects in the fields of aviation, aerospace, navigation, traffic and the like, wherein performance indexes of the three-dimensional coil serving as a core component have great influence on the detection precision of the nuclear magnetic resonance gyroscope, but the three-dimensional coil of the nuclear magnetic resonance gyroscope is a small-size special-shaped coil and is difficult to calibrate in a conventional mode. The prior art adopts a micro three-axis fluxgate, adopts nuclear magnetic resonance calibration and carries out coil calibration based on an SERF magnetometer, and because the coil volume is small, a magnetometer probe is limited by the size and the shape of the magnetometer probe and cannot be placed at the center of the coil, so that the large calibration error precision can be caused, and the magnetometer probe cannot be applied to the calibration of a three-dimensional coil of a nuclear magnetic resonance gyroscope.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the three-dimensional coil coefficient calibration method based on the optical pump nuclear magnetic resonance, which has the advantages of high characteristic precision, no need of using other magnetic field measuring instruments, simple operation and good universality, and can be conveniently applied to the coil coefficient measurement of the three-dimensional coil of the nuclear magnetic resonance gyroscope.

The invention is realized by the following technical scheme:

the atomic glass gas chamber filled with cesium atoms and some buffer gases is arranged in the center of a three-dimensional coil, current is respectively applied to the coil in any one or two directions in the three-dimensional coil to generate a direct-current magnetic field, the atom gas chamber is irradiated by left-handed circularly polarized light, the irradiation direction of the circularly polarized light and the applied direct-current magnetic field are on the same plane, a radio-frequency magnetic field with fixed frequency is applied in the direction perpendicular to the direct-current magnetic field and the plane of the circularly polarized light, the nuclear magnetic resonance state of an optical pump is achieved by adjusting the current, at the moment, the light penetrating through the atom gas chamber is subjected to the maximum modulation of the cesium atoms, the amplitude of emergent light is obtained after the photoelectric conversion and demodulation of the emergent light, and when the current value corresponding to the maximum.

The optical pump nuclear magnetic resonance state is as follows: frequency omega ═ gamma B of radio frequency magnetic field₀Wherein: gamma is the gyromagnetic ratio of cesium atoms, being a fixed constant, B₀The field strength of the DC magnetic field and the field strength B of the radio frequency magnetic field₁cosωt。

The current value corresponding to the maximum amplitude value obtains the amplitude value of the emergent light after photoelectric conversion and demodulation are carried out on the emergent light, and the maximum modulation point is obtained when the amplitude value is maximum. The corresponding current value I satisfies ω ═ γ I λ, thereby obtaining a coil coefficient λ of the coil in the corresponding direction.

Technical effects

The invention integrally solves the technical problems that the center point of the coil cannot be accurately and effectively calibrated due to the limitation of the volume shape of the coil, the volume shape of the magnetometer and the like when the traditional fluxgate magnetometer is used for calibrating the coil, the calibration is not accurate due to the limitation of the volume shape of a probe of the magnetometer and the complicated installation process is caused by the calibration of a three-dimensional coil.

Compared with the prior art, the invention can accurately calibrate the center of the three-dimensional coil by the optical pump magnetic resonance effect, has high precision and avoids using other magnetic field measuring instruments. The size and shape of the atomic gas chamber used in the invention are easy to change, the minimum size can reach 1mm level at present, and the size of the atomic gas chamber can not be influenced by the shape and size of the calibrated coil. Meanwhile, the coil coefficients of each dimension are calibrated without being assembled and disassembled, so that the method has the advantages of simplicity in operation and good universality, and can be conveniently applied to coil coefficient determination of three-dimensional coils of the nuclear magnetic resonance gyroscope.

Drawings

FIG. 1 is a block diagram of the present invention;

FIGS. 2 and 3 are schematic views of an exemplary detection device;

FIGS. 4 and 5 are schematic diagrams illustrating effects of the embodiment;

in the figure: the device comprises a pump laser light source 1, a linear polarizer 2, a lambda/4 wavelength optical lens 3, a magnetic shielding cylinder 4, an x-axis Helmholtz coil 5, a y-axis Helmholtz coil 6, a cesium atom air chamber 7, a z-axis Helmholtz coil 8, a photoelectric detector 9 and a lock-in amplifier 10.

Detailed Description

As shown in fig. 1 to fig. 3, the present embodiment relates to a three-dimensional coil coefficient calibration apparatus based on optical pump nuclear magnetic resonance, including: set up pump laser light source 1, linear polarizer 2, lambda/4 wavelength optical lens 3 in proper order in magnetism shielding section of thick bamboo 4 side to and set up photoelectric detector 9 and lock-in amplifier 10 in proper order in magnetism shielding section of thick bamboo 4 side, wherein: three-dimensional Helmholtz coils 5, 6 and 8 are arranged in the center of a magnetic shielding cylinder 4 after being assembled from inside to outside, a cesium atom air chamber 7 is fixed in the center of the three-dimensional Helmholtz coils, laser generated by a pump laser light source 1 is sequentially converted into left-handed circularly polarized light through a linear polarizer 2 and a lambda/4 wavelength optical lens 3, and emergent light of the left-handed circularly polarized light which is transmitted to the cesium atom air chamber 7 in a space free light form is detected by a photoelectric detector 9 and demodulated by a phase-locked amplifier 10 to obtain the amplitude of a photoelectric signal.

The pump laser light source 1 is electrified to generate laser with the wavelength of 894.2 nm.

The linear polarizer 2 is used for converting the light generated at the pump laser light source 1 into linearly polarized light.

The lambda/4 wavelength optical lens 3 is used for converting the linearly polarized light after passing through the linear polarizer 2 into left circularly polarized light.

The magnetic shielding cylinder 4 is used for shielding the interference of an environmental magnetic field, and the coil calibration in the magnetic shielding cylinder is more accurate.

The Helmholtz coils 5, 6 and 8 are mutually perpendicular three-dimensional coils to be calibrated and can be used for generating a direct current or alternating current magnetic field.

The cesium atom gas chamber 7 is a square glass bubble, cesium atom gas and buffer gas are filled in the cesium atom gas chamber, and the size of the cesium atom gas chamber is 4 mm.

The photodetector 9 is used for receiving the light emitted from the cesium atom gas chamber 7 and converting the light into a voltage signal.

The lock-in amplifier 10 is used for demodulating the voltage signal output by the photodetector 9, and the lock-in amplifier 10 can obtain the amplitude of the specific frequency component signal from the complex signal.

The embodiment relates to a calibration method of the device, which comprises the following steps:

x-axis direction coil coefficient lambda_xCalibration:

1.1) polarization of cesium atoms in the x-direction by the pumping direction from a pump laser source 1, generating a magnetic field B parallel to the direction of the pump laser when a current is applied to a Helmholtz coil 5 of the x-axis parallel to the direction of the pump laser₀＝I_xλ_xWherein: i is_xFor reading the value of the current applied to the coil 5 by means of a multimeter, lambda_xThe coil coefficients for the x-axis helmholtz coil. While applying a radio frequency magnetic field B on the y-axis helmholtz coil 6 (or z-axis helmholtz coil 8) perpendicular to the direction of the pump light₁cos ω t, where the rf magnetic field frequency ω is a defined value.

1.2) increasing the current I gradually from zero_xSo that the magnetic field parallel to the direction of the pump laser corresponds to B₀Increasing until optical pump magnetic resonance occurs, wherein the intensity of transmitted light is modulated by cesium atoms at the frequency of the maximum amplitude of RF magnetic field frequency ω (γ B)₀Wherein: gamma is the gyromagnetic ratio of cesium atoms. The sine wave detected by the photoelectric detector 9 is input into the phase-locked amplifier 10 and phase-locked by the reference signal with the frequency omega to obtain the amplitude of the signal, and I is adjusted_xThe output of the phase-locked amplifier is maximized, and the current I corresponding to the maximum signal amplitude is searched_xmax. By using a multimeter to read the value of the current I applied to the coil 5 at that time_xmaxCalculating to obtain corresponding coil coefficient

X coefficient of coil in y-axis direction_yCalibration:

2.1) emission of the pump laser light source 1Polarizes cesium atoms in the x-direction, and applies a current I to the x-axis Helmholtz coil 5 and the y-axis Helmholtz coil 6 at the same time_x、I_yThen two orthogonal magnetic field vector sums are generatedWherein: current I applied to the coil_x、I_yRead out separately by a multimeter. At the time of being perpendicular to the magnetic field B₀Is applied with a radio frequency magnetic field B on the planar z-axis Helmholtz coil 8₁cos ω t, the frequency ω of the RF magnetic field is set to a certain value.

2.2) constant Current I_xWhile not changing, the current I is gradually increased from zero_yUntil the optical pump magnetic resonance phenomenon is generated, the light intensity of the transmitted light is modulated by the cesium atoms at the frequency with the maximum amplitude of the radio frequency magnetic field frequency omega, wherein omega is gamma B₀Wherein: gamma is the gyromagnetic ratio of cesium atoms. The sine wave detected by the photodetector 9 is input to the lock-in amplifier 10 and is phase-locked by the reference signal with frequency omega to obtain the amplitude of the signal. Regulation I_yThe output of the phase-locked amplifier is maximized, and the current I corresponding to the maximum signal amplitude is searched_ymax. By using a multimeter to read the value of the current I applied to the coil 6 at that time_ymaxCombining the coil coefficient lambda obtained in the step I_xCalculating to obtain corresponding coil coefficient

③ coil coefficient lambda in the z-axis direction_zIs calibrated with lambda_ySimilarly:

3.1) polarization of Cesium atoms in the X-direction in the pumping direction of the pump laser source 1, when a current I is applied to the X-direction coil 5 and the Z-direction coil 8 respectively_x、I_zThe magnitude of the magnetic field generated at this time is the sum of two orthogonal magnetic field vectors Current I applied to the coil_x、I_zCan be read out separately by a multimeter. In a direction perpendicular to the magnetic field B₀A radio frequency magnetic field B is applied to the planar y-direction coil₁cos ω t, the frequency ω of the RF magnetic field is set to a certain value.

Setting the current I on the x-direction coil 5_xIs a fixed value, and gradually increases the current I on the coil 8 in the z direction from zero_zUntil the optical pump magnetic resonance phenomenon is generated, the light intensity of the transmitted light is modulated by the cesium atoms at the frequency with the maximum amplitude of the radio frequency magnetic field frequency omega, wherein omega is gamma B₀Wherein: gamma is the gyromagnetic ratio of cesium atoms. The sine wave detected by the photodetector 9 is input to the lock-in amplifier 10 and is phase-locked by the reference signal with frequency omega to obtain the amplitude of the signal. Regulation I_zThe output of the phase-locked amplifier is maximized, and the current I corresponding to the maximum signal amplitude is searched_zmax. By using a multimeter to read the value of the current I applied to the coil 8 at that time_zmaxCombining the coil coefficient lambda obtained in the step I_xCalculating to obtain corresponding coil coefficient

By mounting the device of fig. 1 on an optical bench, the atomic gas cell and its fixture are shown in fig. 2, and the coil and magnetic shield are shown in fig. 3. Through specific practical experiments, the coil coefficients of the three-dimensional coil obtained by the method are respectively as follows: lambda [ alpha ]_x＝285.17nT/mA，λ_y＝350.26nT/mA，λ_z381.79 nT/mA. The phase-locked amplifier outputs the maximum output by adjusting the current on the corresponding coil, and a phase-locked output curve can be obtained by scanning the current value as shown in fig. 4 and 5, so as to find the current value corresponding to the output maximum point.

Compared with the prior art, the size of the cesium atom gas chamber of the sensitive substance used in the method is only 4mm square, and the calibration of the magnetic field generated by the center of the coil is more accurate.

The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.