CN114993342A - Polarization gradient relaxation measurement method of atomic spin inertia measurement device - Google Patents
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Abstract
A polarization gradient relaxation measurement method of an atomic spin inertia measurement device is characterized in that the polarization gradient relaxation measurement is realized through the following steps, the in-situ measurement of the polarization gradient can be realized in the atomic spin inertia measurement device, and a powerful support is provided for the evaluation and inhibition of the polarization gradient in a gas chamber: step 1, fixing working point parameters of an atomic spin inertia measurement device and having response signals at a diagonal rate; step 2, precession decoupling of alkali metal electron spin and inert gas nuclear spin; step 3, testing the nuclear spin transverse relaxation rate R under the current P1 by using a free precession attenuation method 2 (ii) a Step 4, testing a non-polarized gradient relaxation item in the nuclear spin transverse relaxation; and 5, testing the total transverse relaxation of any pumping laser power point P, and calculating the polarization gradient relaxation of the pumping laser power point P, wherein the polarization gradient relaxation of the point P is the difference value between the total transverse relaxation rate and the non-polarization gradient relaxation rate of the point P.
Description
Technical Field
The invention relates to the field of atomic gyroscopes, in particular to a polarization gradient relaxation measurement method for an atomic spin inertia measurement device.
Background
The Spin-Exchange Relaxation-Free (SERF) atomic Spin inertial measurement unit based on the interaction between optomagnetism and atoms has ultrahigh theoretical measurement sensitivity, and becomes one of the important development directions of future high-precision inertial measurement instruments with unique volume and precision advantages. Atomic spin relaxation is an important source of error in SERF inertial measurement devices that limits performance improvement. There are two main types of atomic spins in the SERF inertial measurement unit: the alkali electron spin and the noble gas nuclear spin. The relaxation time (the values of the relaxation time and the relaxation rate are reciprocal, the unit of the relaxation time is s, the unit of the relaxation rate is 1/s) of each atom is mainly divided into longitudinal relaxation time T1 and transverse relaxation time T2, the longitudinal relaxation time represents the time length of dissipation of the electron spin magnetic moment in the spin polarization direction, and the transverse relaxation time represents the time length of natural dissipation of the spin magnetic moment in the transverse plane corresponding to the polarization direction without external action. And applying a tiny magnetic field bias (2nT) in the Y direction, removing the bias to enable the nuclear spin to precess around the main magnetic field, taking transverse relaxation time as characteristic time to perform free precession attenuation around the main magnetic field direction, testing free precession attenuation signals under different laser powers, and fitting to obtain the nuclear spin transverse relaxation rate of a corresponding power point. The polarization gradient relaxation is one of main sources of noble gas nuclear spin transverse relaxation, and the atomic spin polarization gradient is mainly caused by attenuation of pumping light when laser and atoms interact, and is an error source which is difficult to avoid in an SERF inertial measurement unit. Atomic spin polarization gradients can cause atomic decoherence, leading to atomic relaxation, reducing system sensitivity. Meanwhile, atomic spin polarization gradient relaxation can affect the nuclear spin polarization efficiency of inert gas, weaken the self-compensation capability of nuclei to an external magnetic field, destroy the stability of a system and limit the improvement of the system performance. In an SERF (spin resonance frequency) inertial measurement unit, an effective assessment method for assessment of atomic spin polarization gradient relaxation is lacked, and the invention provides a polarization gradient relaxation measurement method for the atomic spin polarization inertial measurement unit, which provides powerful support for characterization and assessment of atomic spin polarization gradient.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a polarization gradient relaxation measurement method of an atomic spin inertia measurement device.
The technical solution of the invention is as follows:
a polarization gradient relaxation measurement method of an atomic spin inertia measurement device is characterized by comprising the following steps:
step 1, fixing working point parameters of an atomic spin inertia measurement device to have response signals at a diagonal rate, wherein the working point parameters comprise a heating temperature and a pumping laser power point P1, the heating temperature is to heat an alkali metal gas chamber to a target working temperature, a pumping laser at the power point P1 polarizes alkali metal electrons to further hyperpolarize nuclear spin of inert gas, and the device works at a nuclear spin magnetic field self-compensation point through three-axis magnetic field compensation;
step 3, testing the nuclear spin transverse relaxation rate R2 under the current P1 by using a free precession attenuation method;
and 5, testing the total transverse relaxation of any pumping laser power point P, and calculating the polarization gradient relaxation of the pumping laser power point P, wherein the polarization gradient relaxation of the point P is the difference value between the total transverse relaxation rate and the non-polarization gradient relaxation rate of the point P.
The step 3 includes that on the basis of Bz, a bias magnetic field By is applied to the Y direction and is 2nT, the nuclear spin polarization rate Pn precesses around the direction of a main magnetic field, the Pn has polarization rate projection Pnx in the X direction, a free precession attenuation curve changing in the X direction of Pnx is obtained through an output signal, the envelope of the attenuation curve is fitted, and the nuclear spin transverse relaxation rate R under the current pumping power point is obtained 2 。
The step 4 comprises the step of fast processing on the basis of P1The pumping laser power is reduced rapidly to 50 percent of the P1 point, and the nuclear spin transverse relaxation rate R is tested 2 Repeatedly reducing the power point to 50% of the last test point until R is reduced along with the reduction of the pumping laser power 2 Tend to be constant; change of nuclear spin relaxation, R, caused by change of electron polarization distribution when pumping laser power is changed 2 The other relaxation terms in (1) are not affected by the pumping laser power, and the transverse relaxation measured at this time is a non-polarized gradient relaxation term.
The other relaxation terms include spin collision relaxation R sd Electric quadrupole moment relaxation R quad And spin exchange relaxation R se The spin collision relaxation is collision relaxation between Ne atoms, and the spin exchange relaxation is spin exchange relaxation between an inert gas Ne atom and an alkali metal electron:
wherein T is 2 In order to determine the transverse relaxation time of the nuclear spins,
relaxation of electron spin polarization gradient;
wherein p is Ne Is the air pressure of the air chamber;
wherein
The spin exchange relaxation of the Rb and K atoms, respectively, to the Ne atom,
exchange collision coefficients between Ne atoms and Rb, K atoms, respectively, n K 、n Rb A density of K, Rb atoms each;
wherein, the first and the second end of the pipe are connected with each other,
spin collision relaxations of Rb to Ne, Ne to Rb, K to Ne, and Rb to Ne, respectively. n is K 、n Rb 、n Ne Respectively, density of K, Rb, Ne atoms, upsilon NeRb 、υ NeK Spin collision velocities between Ne atoms and Rb, K atoms, respectively;
where Rp is the pumping power, T is the temperature, α is a coefficient independent of the pumping power, D n Is the diffusion coefficient of the inert gas Ne in the gas chamber, d is the diameter of the gas chamber, n K Denotes the density of the alkali metal K atoms, W is a Lambert function, R rel Is the electron relaxation rate, R, of alkali metals p0 Is the pumping power of the incident point, e is a natural constant,
for polarizing gradient, σ v Is the photon absorption cross-sectional area.
The atomic spin inertia measuring device comprises a pumping laser and a detection laser, wherein the pumping laser is sequentially connected with a first convex lens, a first polaroid, a liquid crystal, a second polaroid, a second convex lens and a reflector, the reflector is connected with a first beam splitter through a first 1/2 wave plate, the transmission side of the first beam splitter sequentially passes through a 1/4 wave plate and an air chamber to be connected with a fourth photoelectric detector, the reflection side of the first beam splitter sequentially passes through a first photoelectric detector and a power control system to be connected with the liquid crystal, the detection laser is sequentially connected with a third polaroid, a second 1/2 wave plate, a second beam splitter, an air chamber, a Wollaston prism and a second photoelectric detector, the second photoelectric detector is connected with a signal acquisition system, the reflection end of the second beam splitter is connected with a third photoelectric detector, and the third photoelectric detector and the fourth photoelectric detector are respectively connected with the signal acquisition system, and the periphery of the air chamber is sequentially provided with a heating film, a coil, a ferrite and a shielding cylinder from inside to outside.
The invention has the following technical effects: the method for measuring the polarization gradient relaxation of the atomic spin inertia measuring device can accurately test the polarization gradient relaxation at different pumping light power working points and evaluate the polarization gradient level in the air chamber. When the parameters such as the temperature of the air chamber, the density ratio in the air chamber, the air pressure and the like are fixed, only one time of calibration of a non-polarized gradient relaxation term is needed (3-5 pumping power points are changed to rapidly measure R 2 ) And proceed to the current pumping power operating point R 2 The polarization gradient relaxation at the current working point can be calculated through the test of (1). And transmitCompared with the traditional method for compensating the magnetic field gradient by using the gradient coil and detecting the electron polarizability gradient by using the array detection light, the method provided by the invention can be used for rapidly measuring and directly separating the polarization gradient relaxation, does not need to add an additional coil or change a detection light path, can be used for realizing the in-situ measurement of the polarization gradient in an atomic spin inertia measuring device, and provides powerful support for the evaluation and inhibition of the polarization gradient in the gas chamber.
Drawings
Fig. 1 is a schematic flow chart of a polarization gradient relaxation measurement method for an atomic spin inertia measurement apparatus according to the present invention. Fig. 1 includes the following steps: step 1, fixing working point parameters such as heating temperature, pumping laser power (power point: P1) and the like, and enabling the device to work at a nuclear spin self-compensation point; step 2, applying a magnetic field Bz with a bias ten times of a self-compensation point in the direction of a main magnetic field to decouple electron spin and nuclear spin; step 3, testing the total transverse relaxation rate R of the current working point by utilizing the free precession attenuation signal 2 (ii) a Step 4, reducing the power to 50% of the point P1, and testing R 2 Repeating the steps to reduce the power to 50% of the last test point until R is reduced with the reduction of the pumping light power 2 Obtaining the non-polarization gradient relaxation rate without changing; step 5, testing R of any power working point P 2 Through R 2 And subtracting the non-polarization gradient relaxation rate to obtain the polarization gradient relaxation of the working point P.
Fig. 2 is a schematic structural diagram of a system used for implementing the polarization gradient relaxation measurement method of the atomic spin inertia measurement device according to the present invention. The system in fig. 2 is a SERF atomic Spin inertia measurement system (SERF, Spin-Exchange Relaxation-Free, without Spin Exchange Relaxation). In fig. 2, the optical pumping system sequentially comprises a pumping optical path (from a pumping laser 1, a reflecting mirror 7 to a fourth photoelectric detector 26), a detection optical path (from a detection laser 25 to a second photoelectric detector 17), a shielding cylinder 16, a ferrite 15, a coil 14, a heating film 13 and an air chamber 20 from outside to inside, wherein the pumping optical path comprises a first convex lens 2, a first polarizer 3, a liquid crystal 4, a second polarizer 5, a second convex lens 6, a reflecting mirror 7, a first 1/2 wave plate 8 (lambda/2), a first beam splitter 9, a 1/4 wave plate (lambda/4), a fourth photoelectric detector 26, a reflecting end of the first beam splitter 9 is connected with a feedback end of a power control system 11 through the first photoelectric detector 10, and a control end of the power control system 11 is connected with the liquid crystal 4; the detection optical path comprises a third polarizer 24, a second 1/2 wave plate 23 (lambda/2), a second beam splitter 21, a Wollaston prism 19 and a second photodetector 17; the exit end of the Wollaston prism 19 is connected with a second photoelectric detector 17, and the second photoelectric detector 17 is connected with a signal acquisition system 18; the reflection end of the second beam splitter 21 is connected to the third photodetector 22, and the third photodetector 22 and the fourth photodetector 26 are respectively connected to the signal acquisition system 18.
Detailed Description
The invention is explained below with reference to the figures (fig. 1-2) and examples.
FIG. 1 is a schematic flow chart of a method for measuring polarization gradient relaxation of an atomic spin inertia measurement device according to the present invention. Fig. 2 is a schematic structural diagram of a system used for implementing the polarization gradient relaxation measurement method of the atomic spin inertia measurement device according to the present invention. Referring to fig. 1 to 2, a polarization gradient relaxation measurement method for an atomic spin inertia measurement device is characterized by comprising the following steps: step 1, fixing working point parameters of an atomic spin inertia measurement device to have response signals at a diagonal rate, wherein the working point parameters comprise a heating temperature and a pumping laser power point P1, the heating temperature is to heat an alkali metal gas chamber to a target working temperature, a pumping laser at the power point P1 polarizes alkali metal electrons to further hyperpolarize nuclear spin of inert gas, and the device works at a nuclear spin magnetic field self-compensation point through three-axis magnetic field compensation; step 2, precession decoupling of alkali metal electron spin and inert gas nuclear spin; step 3, testing the nuclear spin transverse relaxation rate R under the current P1 by using a free precession attenuation method 2 (ii) a Step 4, testing a non-polarized gradient relaxation item in the nuclear spin transverse relaxation; and 5, testing the total transverse relaxation of any pumping laser power point P, and calculating the polarization gradient relaxation of the pumping laser power point P, wherein the polarization gradient relaxation of the point P is the difference value between the total transverse relaxation rate and the non-polarization gradient relaxation rate of the point P.
The other relaxation terms include spin collision relaxation R sd Electric quadrupole moment relaxation r quad And spin exchange relaxation R se The spin collision relaxation is collision relaxation between Ne atoms, and the spin exchange relaxation is spin exchange relaxation between an inert gas Ne atom and an alkali metal electron:
wherein T is 2 Is the transverse relaxation time of the nuclear spin,
relaxation of electron spin polarization gradient;
wherein p is Ne Is the air pressure of the air chamber;
wherein
The spin exchange relaxation of the Rb and K atoms, respectively, to the Ne atom,
the exchange collision coefficients between Ne atoms and Rb, K atoms, n K 、n Rb K, Rb atom density, respectively;
wherein, the first and the second end of the pipe are connected with each other,
spin collision relaxation of Rb to Ne, Ne to Rb, K to Ne, and Rb to Ne, respectively。n K 、n Rb 、n Ne Respectively, density of K, Rb, Ne atoms, upsilon NeRb 、υ NeK Spin collision velocities between Ne atoms and Rb, K atoms, respectively;
where Rp is the pumping power, T is the temperature, α is a coefficient independent of the pumping power, D n Is the diffusion coefficient of the inert gas Ne in the chamber, d is the diameter of the chamber, n K Denotes the density of the alkali metal K atoms, W is a Lambert function, R rel Is the electron relaxation rate of alkali metal, R p0 Is the pumping power of the incident point, e is a natural constant,
for polarizing gradient, σ v Is the photon absorption cross-sectional area.
The atomic spin inertia measurement device comprises a pumping laser 1 and a detection laser 25, wherein the pumping laser 1 is sequentially connected with a first convex lens 2, a first polaroid 3, a liquid crystal 4, a second polaroid 5, a second convex lens 6 and a reflector 7, the reflector 7 is connected with a first beam splitter 9 through a first 1/2 wave plate 8, the transmission side of the first beam splitter 9 is sequentially connected with a fourth photoelectric detector 26 through a 1/4 wave plate 12 and a gas chamber 20, the reflection side of the first beam splitter 9 is sequentially connected with the liquid crystal 5 through a first photoelectric detector 10 and a power control system 11, the detection laser 25 is sequentially connected with a third polaroid 24, a second 1/2 wave plate 23, a second beam splitter 21, a gas chamber 20, a Wollas prism 19 and a second photoelectric detector 17, the second photoelectric detector 17 is connected with a signal acquisition system 18, the reflection end of the second beam splitter 21 is connected with a third photoelectric detector 22, the third photoelectric detector 22 and a fourth photoelectric detector 26 are respectively connected with the signal acquisition system 18, and the periphery of the air chamber 20 is sequentially provided with a heating film 13, a coil 14, a ferrite 15 and a shielding cylinder 16 from inside to outside.
A polarization gradient relaxation measurement method for an atomic spin inertia measurement device is characterized in that when parameters of a gas chamber and working temperature points are determined, an atomic free precession attenuation curve under a pumping laser power working point is tested, and the transverse total relaxation rate of nuclear spin is obtained. In nuclear spin transverse relaxation, only polarization gradient relaxation is associated with the pump optical power. And reducing the pumping laser power until the transverse total relaxation rate is constant along with the reduction of the pumping laser power, wherein the relaxation rate of a flat zone is a non-polarization gradient relaxation term in the total relaxation. The difference value of the transverse relaxation rate and the non-polarization gradient relaxation rate of the system working point is the atomic spin polarization gradient relaxation of the current working point. The method can realize the in-situ measurement of the polarization gradient relaxation without adding an additional coil or changing a detection light path. The power of pumping laser is changed rapidly, so that the separation measurement of polarization gradient relaxation can be realized, and powerful support is provided for the evaluation and inhibition of polarization gradient in a gas chamber in an SERF atomic spin inertia measurement device.
A method for measuring polarization gradient relaxation of an atomic spin inertia measurement device comprises the following steps:
step 1, fixing working point parameters such as heating temperature, pumping laser power (working point P1) and the like, enabling the device to be in a normal gyro working state (nuclear spin self-compensation point) through three-axis magnetic field compensation, and enabling the device to have a response signal to angular rate. An alkali metal gas chamber in the atomic spin inertia measurement device is heated to a target working temperature, the pumping laser is utilized to polarize alkali metal electrons, and then the nuclear spin of the hyperpolarized inert gas is achieved, so that the system is in a polarization state, the device works at a magnetic field self-compensation point, and the device can respond to external angular rate input.
And 2, precession decoupling of electron spin and nuclear spin. And a magnetic field Bz which is ten times of the self-compensation point of the magnetic field is applied to the main magnetic field direction Z, so that the precession between the electron spin and the nuclear spin is decoupled.
And 3, testing the nuclear spin transverse relaxation rate under the current pumping working point P1 by using a free precession attenuation method. In addition to Bz, when the Y-direction applied magnetic field bias By is 2nT, the nuclear spin Pn precesses around the main magnetic field direction, and at this time, a polarization ratio projection Pnx exists in the X direction, and a change curve (free precession attenuation curve) of the X-direction polarization ratio projection is obtained from the output signal. Fitting the envelope of the attenuation curve to obtain the kernel under the current pumping power pointSpin transverse relaxation rate R 2 。
And 4, testing a non-polarized gradient relaxation item in transverse relaxation. Rapidly reducing the pumping optical power to 50% of P1 point on the basis of P1, and testing the nuclear spin transverse relaxation rate R 2 Repeatedly reducing the power point to 50% of the last test point until R is reduced along with the reduction of the pumping light power 2 Tends to be constant. Change in nuclear spin relaxation due to change in electron polarization distribution when the pumping laser power is changed, R 2 The other relaxation terms (spin collision relaxation, electric quadrupole relaxation, spin exchange relaxation) in (a) are not affected by the laser power, and the transverse relaxation measured at this time is a non-polarized gradient relaxation term.
And 5, testing the total transverse relaxation of any power point P, and calculating the polarization gradient relaxation of the working point P. And the polarization gradient relaxation of the point P is the difference value of the total transverse relaxation rate and the non-polarization gradient relaxation rate under the current working laser power point P. By testing R at each power point 2 And obtaining the polarization gradient relaxation at the current working point.
The principle of the invention is as follows:
nuclear spin longitudinal transverse relaxation R in SERF atomic spin inertia measurement system 2 Can be expressed as
Wherein T is 2 As nuclear spin transverse relaxation time, R quad For electric quadrupole moment relaxation, R se For exchange relaxation between the Ne atom of the inert gas and the electrons of the alkali metal, R sd In order to relax the collision between the Ne atoms,
relaxation is electron spin polarization gradient.
The expressions for the relaxations of the terms are:
A. electric quadrupole moment relaxation R quad
Wherein p is Ne Is the air pressure of the air chamber.
B. Spin exchange relaxation R se
Wherein
Is the spin exchange relaxation of Rb and K atoms to Ne atoms,
the exchange collision coefficients between Ne atoms and Rb, K atoms, respectively.
C. Spin collision relaxation R sd
Wherein, the first and the second end of the pipe are connected with each other,
spin collision relaxations of Rb to Ne, Ne to Rb, K to Ne, and Rb to Ne, respectively. n is K 、n Rb 、n Ne The densities of K, Rb and Ne atoms. Upsilon is NeRb 、υ NeK The spin collision velocities between Ne atoms and Rb and K atoms, respectively.
D. Polarization gradient relaxation
In the SERF atomic spin inertia measurement system, the main source of the polarization gradient is absorption of the pumping light when the alkali metal atoms are polarized, so that the alkali metal electron spin polarization rate is attenuated along the propagation direction of the pumping light, and the polarization gradient is generated in a gas chamber. In addition, the relaxation of electrons by the gas cell walls, and the diffusion of atoms within the gas cell are also responsible for the polarization gradient. The diffusion effect is mainly related to the temperature and the air pressure of the air chamber, and the relaxation of the wall of the air chamber to electrons is mainly related to the diameter and the air pressure of the air chamber. Both are not affected by the pumping laser power. The working temperature point of a SERF atomic spin inertia measurement system is 170-200 ℃, the absorption effect of atoms on pumping light is severe, and the absorption of polarized alkali metal electrons on the pumping light can be realized by the following pumping rate R p (z) the attenuation equation as the pump light passes through the path length z in the gas cell is expressed as:
wherein, P e (z) is the polarization rate of the electron spin at the incident distance z, σ v Is the photon absorption cross section area, n K Represents the density of alkali metal K atoms. The equation (1) can be solved by using Lambert W function to obtain pumping light intensity I (z) and pumping rate R p (z) as a function of incident distance z:
wherein h is Planck constant, v is pumping laser frequency, and I (0) is light intensity when the incident distance is 0, namely the light intensity of the incident point. e is a natural constant, R p0 Pumping ratio of incident point, R rel Is the electron relaxation rate of alkali metal. Sigma v Is the photon absorption cross-sectional area, z is the length of the path of the pump light through the gas cell, n K Represents the density of alkali metal K atoms. W is a Lambertian function, and is f (W) ═ W × e w The inverse function of (i), i.e. Y ═ X × e X ,X＝W(Y)
Spin-polarizability gradient of electrons along the propagation direction of pump light (Z direction)
Can be expressed as
Wherein z is 1 、z 2 For two points of position along the Z-direction,
is the polarizability at that point.
Polarization gradient relaxation
And polarization gradient
Can be expressed as
Where α is a coefficient independent of the pumping power, D n Is the diffusion coefficient of the inert gas Ne in the chamber, d is the diameter of the chamber, n K Denotes the density of the alkali metal K atoms, W is a Lambert function, R rel Is the electron relaxation rate of alkali metal, R p0 Is the pumping rate of the incident spot.
The derivation of equation (5) with respect to the pumping rate Rp can be found:
according to equation (6), when there is no incident pump light, i.e., Rp0 is 0,
and is
I.e. the incident point pumps the optical power to 0, the polarization gradient relaxations gradually decrease and go to 0, and the decreasing trend becomes slow until the same, i.e. the plateau appears. In a SERF atomic spin inertia measurement device, when the pumping light power is reduced, the measured relaxation rate is close to the non-polarization gradient relaxation rate, namely the relaxation rate corresponding to a flat zone is the non-polarization gradient relaxation rate. Therefore, the measurement of the polarization gradient relaxation of the atomic spin in the system can be realized by measuring the difference between the transverse relaxation rate of the working point and the non-polarization gradient relaxation tested after the pumping power point is rapidly reduced.
Compared with the prior art, the invention has the advantages that: the polarization gradient relaxation under different pumping light power working points can be accurately tested, and the polarization gradient level in the air chamber can be evaluated. When the parameters such as the temperature of the air chamber, the density ratio in the air chamber, the air pressure and the like are fixed, only one-time calibration of the non-polarized gradient relaxation term is needed (3-5 pumping power points are changed to quickly measure R 2 ) And proceed to the current pumping power operating point R 2 The polarization gradient relaxation at the current working point can be calculated. Magnetic field compensation ladder for traditional gradient coilCompared with the method for measuring the electron polarizability gradient by using array detection light, the method provided by the invention can be used for rapidly measuring and directly separating the polarization gradient relaxation, and can be used for realizing the in-situ measurement of the polarization gradient in an atomic spin inertia measuring device without adding an additional coil or changing a detection light path, thereby providing powerful support for the evaluation and inhibition of the polarization gradient in the gas chamber.
Those skilled in the art will appreciate that the invention may be practiced without these specific details. It is pointed out here that the above description is helpful for the person skilled in the art to understand the invention, but does not limit the scope of the invention. Any such equivalents, modifications and/or omissions as may be made without departing from the spirit and scope of the invention may be resorted to.
Claims (6)
1. A polarization gradient relaxation measurement method of an atomic spin inertia measurement device is characterized by comprising the following steps:
step 1, fixing working point parameters of an atomic spin inertia measurement device to have response signals at a diagonal rate, wherein the working point parameters comprise a heating temperature and a pumping laser power point P1, the heating temperature is to heat an alkali metal gas chamber to a target working temperature, a pumping laser at the power point P1 polarizes alkali metal electrons to further hyperpolarize nuclear spin of inert gas, and the device works at a nuclear spin magnetic field self-compensation point through three-axis magnetic field compensation;
step 2, precession decoupling of alkali metal electron spin and inert gas nuclear spin;
step 3, testing the nuclear spin transverse relaxation rate R under the current P1 by using a free precession attenuation method 2 ；
Step 4, testing a non-polarized gradient relaxation item in the nuclear spin transverse relaxation;
and 5, testing the total transverse relaxation of any pumping laser power point P, and calculating the polarization gradient relaxation of the pumping laser power point P, wherein the polarization gradient relaxation of the point P is the difference value between the total transverse relaxation rate and the non-polarization gradient relaxation rate of the point P.
2. The method for polarization gradient relaxation measurement of atomic spin inertia measurement device according to claim 1, wherein step 2 comprises applying a magnetic field Bz biased ten times as much as a self-compensation point of the magnetic field in a main magnetic field direction Z to decouple precession between electron spin and nuclear spin.
3. The method for polarization gradient relaxation measurement of atomic spin inertia measurement device according to claim 2, wherein the step 3 includes applying a bias magnetic field By of 2nT to Y direction based on Bz, precessing the spin polarization ratio Pn around the main magnetic field direction, projecting the polarization ratio Pn in X direction Pnx, obtaining a free precession attenuation curve changing in X direction By output signal Pnx, fitting the envelope of the attenuation curve, and obtaining the transverse relaxation ratio R of nuclear spin at the current pumping power point 2 。
4. The method for polarization gradient relaxation measurement of atomic spin inertia measurement device according to claim 1, wherein the step 4 comprises rapidly lowering the pump laser power to 50% of P1 point based on P1, and testing the nuclear spin transverse relaxation rate R 2 Repeatedly reducing the power point to 50% of the last test point until R is reduced along with the reduction of the pumping laser power 2 Tend to be constant; change in nuclear spin relaxation due to change in electron polarization distribution when the pumping laser power is changed, R 2 The other relaxation terms in (1) are not affected by the pumping laser power, and the transverse relaxation measured at this time is a non-polarized gradient relaxation term.
5. The method of claim 4, wherein the other relaxation terms include spin collision relaxation R sd Electric quadrupole moment relaxation R quad And spin exchange relaxation R se The spin collision relaxation is collision relaxation between Ne atoms, and the spin exchange relaxation is spin exchange relaxation between an inert gas Ne atom and an alkali metal electron:
wherein T is 2 In order to determine the transverse relaxation time of the nuclear spins,
relaxation of electron spin polarization gradient;
wherein p is Ne Is the air pressure of the air chamber;
wherein
The spin exchange relaxation of the Rb and K atoms, respectively, to the Ne atom,
the exchange collision coefficients between Ne atoms and Rb, K atoms, n K 、n Rb K, Rb atom density, respectively;
wherein, the first and the second end of the pipe are connected with each other,
spin collision relaxations of Rb to Ne, Ne to Rb, K to Ne, and Rb to Ne, respectively. n is K 、n Rb 、n Ne Respectively, density of K, Rb, Ne atoms, upsilon NeRb 、υ NeK Spin collision velocities between Ne atoms and Rb, K atoms, respectively;
where Rp is the pumping power, T is the temperature, α is a coefficient independent of the pumping power, D n Is the diffusion coefficient of the inert gas Ne in the gas chamber, d is the diameter of the gas chamber, n K Denotes the density of the alkali metal K atoms, W is a Lambert function, R rel Is the electron relaxation rate of alkali metal, R p0 Is the pumping power of the incident point, e is a natural constant,
for polarizing gradient, σ v Is the photon absorption cross-sectional area.
6. The polarization gradient relaxation measurement method of an atomic spin inertia measurement device according to claim 1, wherein the atomic spin inertia measurement device comprises a pump laser and a detection laser, the pump laser is sequentially connected to a first convex lens, a first polarizer, a liquid crystal, a second polarizer, a second convex lens and a mirror, the mirror is connected to a first beam splitter through a first 1/2 wave plate, a transmission side of the first beam splitter is sequentially connected to a fourth photodetector through a 1/4 wave plate and a gas chamber, a reflection side of the first beam splitter is sequentially connected to the liquid crystal through a first photodetector and a power control system, the detection laser is sequentially connected to a third polarizer, a second 1/2 wave plate, a second beam splitter, a gas chamber, a Wollaston prism and a second photodetector, and the second photodetector is connected to a signal acquisition system, the reflection end of the second beam splitter is connected with a third photoelectric detector, the third photoelectric detector and a fourth photoelectric detector are respectively connected with a signal acquisition system, and a heating film, a coil, a ferrite and a shielding cylinder are sequentially arranged on the periphery of the air chamber from inside to outside.
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