An inertial measurement method based on alkali noble gas mixed spin ensemble

Abstract

The present application relates to a kind of inertial measurement method based on alkali noble gas mixed spin ensemble, which can accurately realize the measurement of weak angular velocity.The method measures the equivalent magnetic field of two kinds of nuclear spins (such as 3 He and 21 Ne) in situ by alkali electron spin, and further obtains the nuclear spin precession frequency directly related to magnetic field and angular velocity, compares the frequency of two kinds of nuclear spins to eliminate the response of magnetic field, and combines the light pulse sequence to reverse the equivalent magnetic field of alkali metal, reduces the system error caused by it.The method of the present application is reasonable, simple in experimental operation, suitable for mixed spin ensemble, and can realize the accurate measurement of angular velocity, and provides a basis for the development of high-precision inertial measurement device.

Description

Technical Field

[0001] This invention relates to the field of inertial measurement technology, specifically to an inertial measurement method based on a mixed spin ensemble of alkali metal inert gases. This method can solve the problem of weak angular velocity calibration, and the angular velocity calibration is reasonable and the experimental operation is simple, providing a foundation for the research of high-precision inertial measurement. Background Technology

[0002] In the acquisition and perception of carrier motion information, precise measurement of angular velocity is required. With the continuous development of inertial measurement, the measurement methods have undergone a transformation from mechanical to optical to atomic, and are constantly moving towards higher precision.

[0003] Currently, much attention is focused on the zero-bias stability of angular velocity measurements, which assesses the stability of the output signal when there is no input signal. Specifically, it describes the degree to which the sensor's output signal deviates from the zero reference value under constant conditions and without external influence, and the stability of this deviation over time. However, what is more important for measurement is accuracy, i.e., how close the measured result is to the true result. Existing methods can only calibrate the accuracy of the output result by applying an input signal. Summary of the Invention

[0004] This invention addresses the deficiencies or shortcomings of existing technologies by providing an inertial measurement method based on a mixed spin ensemble of alkali metal inert gases. This method can solve the problem of weak angular velocity calibration, and the angular velocity calibration is reasonable and the experimental operation is simple, thus providing a foundation for the research of high-precision inertial measurement.

[0005] The technical solution of the present invention is as follows:

[0006] An inertial metrology method based on a mixed spin ensemble of alkali metal inert gases, characterized by comprising the following steps:

[0007] Step 1: For the alkali metal inert gas mixed spin ensemble, the alkali metal resonant circularly polarized light is used to polarize the alkali metal electron spin along the z-direction;

[0008] Step 2: Spin exchange optical pumping of the two inert gas nuclear spins is achieved through spin exchange between the electron spins of alkali metals and the nuclear spins of inert gases.

[0009] Step 3: Apply a sequence of light pulses to achieve the flipping of the electron spin of the alkali metal along the z-axis;

[0010] Step 4: Apply a nuclear spin pulse magnetic field to flip the two nuclear spin polarizations from the z-axis to the x-axis, thereby maximizing the transverse polarization component;

[0011] Step 5: Detect the x-axis polarizability of alkali metal electron spin, measure the nuclear spin equivalent magnetic field in situ, and obtain the damped oscillation frequency information by fitting the expression of the damped oscillation signal.

[0012] Step 6: Calculate the angular velocity using the spin-magnetic ratio of the inert gas nuclei and the decaying oscillation frequencies of the two types of nuclear spins.

[0013] In step 3, the optical pulse sequence is a flip of σ+ / σ-, where σ+ refers to left-handed circularly polarized light and σ- refers to right-handed circularly polarized light. The optical pulse frequency is much greater than the nuclear spin precession frequency.

[0014] In step 4, the pulsed magnetic field refers to the y-axis pulsed magnetic field B. y B y The effect causes the two nuclear spin polarizations to flip around the y-axis from the z-axis to the x-axis, and B is determined according to the following formula. y The time of action t p :

[0015] t p = (1 / 2 × n + 1 / 4) / (γ1B) y )=(1 / 2×m+1 / 4) / (γ2B y ),

[0016] Where n is an integer ≥ 0, m is an integer ≥ 0, and B y γ is the amplitude of the y-axis pulsed magnetic field, γ1 is the nuclear spin gyromagnetic ratio of the first type of inert gas, and γ2 is the nuclear spin gyromagnetic ratio of the second type of inert gas.

[0017] Two inert gases can be used in various combinations; for example, the first inert gas is... 3 He, γ1 = 0.0324 Hz / nT, the second inert gas is 21 Ne, γ2=0.003361Hz / nT.

[0018] The expression for the damped oscillation signal in step 5 is as follows:

[0019]

[0020] in, Here, A is the detected x-axis electron spin polarization, A is the amplitude of the first type of nuclear spin decay oscillation signal, f1 is the frequency of the first type of nuclear spin decay oscillation, and t is time. f1 is the fitted phase of the first type of nuclear spin decay oscillation signal, T1 is the relaxation time of the first type of nuclear spin, B is the amplitude of the second type of nuclear spin decay oscillation signal, and f2 is the frequency of the second type of nuclear spin decay oscillation. T2 is the phase fitting of the second type of nuclear spin decay oscillation signal, T2 is the relaxation time of the second type of nuclear spin, and C is a constant term.

[0021] Step 6 includes the following relational expression:

[0022]

[0023] Where Δf is the calculated frequency difference of the damped oscillation signal, B is the applied bias magnetic field, and Ω is the angular velocity to be measured.

[0024] The advantages of this invention compared to the prior art are:

[0025] (1) This invention uses the physical constant, namely the gyromagnetic ratio of nuclear spin, for inertial measurement. The measured input signal is traced back to the physical constant with high accuracy, and the absolute value of angular velocity can be directly measured.

[0026] (2) The method of the present invention is reasonable and the experimental operation is simple, which provides a foundation for the development of high-precision inertial measurement. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart illustrating the implementation of an inertial metrology method based on a mixed spin ensemble of alkali metal inert gases according to the present invention. Figure 1 The process includes: Step 1, continuous optical pumping of z-polarized alkali metal; Step 2, spin-exchange optical pumping of two inert gases; Step 3, optical pulse sequence flipping z-axis electron spin; Step 4, y-axis pulsed magnetic field flipping nuclear spin to transverse; Step 5, fitting a decaying oscillation signal to obtain the frequency; Step 6, frequency difference calculation of angular velocity. Detailed Implementation

[0028] The following is in conjunction with the attached diagram ( Figure 1 The invention will be described in the following sections and examples.

[0029] Figure 1 This is a schematic flowchart illustrating the implementation of an inertial metrology method based on a mixed spin ensemble of alkali metal inert gases according to the present invention. (Reference) Figure 1As shown, an inertial metrology method based on a mixed spin ensemble of alkali metal inert gases includes the following steps: Step 1, for the mixed spin ensemble of alkali metal inert gases, alkali metal resonant circularly polarized light is used to polarize the alkali metal electron spin along the z-axis; Step 2, spin exchange optical pumping of the two inert gas nuclear spins is achieved through spin exchange between the alkali metal electron spin and the inert gas nuclear spin; Step 3, a sequence of optical pulses is applied to achieve the flipping of the alkali metal electron spin along the z-axis; Step 4, a nuclear spin pulse magnetic field is applied to flip the polarization of the two nuclear spins from the z-axis to the x-axis, maximizing the transverse polarization component; Step 5, the x-axis polarizability of the alkali metal electron spin is detected, the equivalent magnetic field of the nuclear spin is measured in situ, and the damped oscillation frequency information is obtained by fitting the damped oscillation signal expression; Step 6, the angular velocity is calculated using the gyromagnetic ratio of the inert gas nuclear spins and the damped oscillation frequencies of the two nuclear spins.

[0030] In step 3, the light pulse sequence is a flip of σ+ / σ-, where σ+ refers to left-handed circularly polarized light and σ- refers to right-handed circularly polarized light. The light pulse frequency is much higher than the nuclear spin precession frequency. In step 4, the pulsed magnetic field refers to the y-axis pulsed magnetic field B. y B y The effect causes the two nuclear spin polarizations to flip around the y-axis from the z-axis to the x-axis, and B is determined according to the following formula. y The time of action t p :

[0031] t p = (1 / 2 × n + 1 / 4) / (γ1B) y )=(1 / 2×m+1 / 4) / (γ2B y ),

[0032] Where n is an integer ≥ 0, m is an integer ≥ 0, and B y γ1 is the amplitude of the y-axis pulsed magnetic field, γ2 is the nuclear spin gyromagnetic ratio of the first inert gas, and γ1 is the nuclear spin gyromagnetic ratio of the second inert gas. For example, the first inert gas is... 3 He, γ1 = 0.0324 Hz / nT, the second inert gas is 21 Ne, γ2=0.003361Hz / nT.

[0033] The expression for the damped oscillation signal in step 5 is as follows:

[0034]

[0035] in, Here, A is the detected x-axis electron spin polarization, A is the amplitude of the first type of nuclear spin decay oscillation signal, f1 is the frequency of the first type of nuclear spin decay oscillation, and t is time. f1 is the fitted phase of the first type of nuclear spin decay oscillation signal, T1 is the relaxation time of the first type of nuclear spin, B is the amplitude of the second type of nuclear spin decay oscillation signal, and f2 is the frequency of the second type of nuclear spin decay oscillation. T2 is the phase fitting of the second type of nuclear spin decay oscillation signal, T2 is the relaxation time of the second type of nuclear spin, and C is a constant term.

[0036] Step 6 includes the following relational expression:

[0037]

[0038] Where Δf is the calculated frequency difference of the damped oscillation signal, B is the applied bias magnetic field, and Ω is the angular velocity to be measured.

[0039] This invention relates to an inertial metrology method based on a mixed spin ensemble of alkali metal inert gases, which can accurately measure minute angular velocities. This method measures two nuclear spins (e.g., alkali metal electron spins) in situ using the electron spins of alkali metals. 3 He and 21 The equivalent magnetic field of Ne is obtained, and the nuclear spin precession frequency, which is directly related to the magnetic field and angular velocity, is obtained. The response of the magnetic field is eliminated by comparing the frequencies of the two nuclear spins, and the equivalent magnetic field of the alkali metal is flipped by the optical pulse sequence to reduce the systematic error caused by it. The method of this invention is reasonable, the experimental operation is simple, it is applicable to hybrid spin ensembles, and it can realize the accurate measurement of angular velocity, providing a foundation for the development of high-precision inertial measurement devices.

[0040] The specific implementation process of this invention is as follows: Figure 1 As shown. The technical solution of the present invention is: The present invention relates to an inertial metrology method based on a mixed spin ensemble of alkali metal inert gases, comprising the following steps:

[0041] Step (1): Utilize alkali metal resonance circularly polarized light to polarize the electron spin of alkali metal along the z-direction.

[0042] Step (2): Spin exchange optical pumping of the two inert gas nuclear spins is achieved through spin exchange between the electron spins of alkali metals and the nuclear spins of inert gases.

[0043] Step (3): After polarization is completed, a sequence of light pulses is applied to achieve the flipping of the electron spin of the alkali metal along the z-direction.

[0044] Step (4): Apply a nuclear spin pulse magnetic field to flip the two nuclear spin polarizations from the z-direction to the x-direction, thereby maximizing the transverse polarization component.

[0045] Step (5): Detect the x-axis polarizability of alkali metal electron spin, measure the nuclear spin equivalent magnetic field in situ, and obtain frequency information by fitting the damped oscillation expression.

[0046] Step (6): Angular velocity is calculated by using the spin-magnetic ratio of the inert gas nuclei and the decaying oscillation frequency of the two types of nuclear spins.

[0047] In step (3), the optical pulse sequence is a flip of σ+ / σ-, where σ+ refers to left-handed circularly polarized light and σ- refers to right-handed circularly polarized light, with a frequency much greater than the nuclear spin precession frequency.

[0048] In step (4), the pulsed magnetic field refers to B. y The magnetic field causes the spin polarization of the two nuclei to flip from the z-axis to the x-axis around the y-axis, requiring the magnetic field to be applied for a duration of t. p = (1 / 2 × n + 1 / 4) / (γ1B) y )=(1 / 2×m+1 / 4) / (γ2B y ), where n is an integer ≥ 0, m is an integer ≥ 0, and t p B is the time when the pulsed magnetic field is applied in the y-direction. y γ is the amplitude of the y-axis pulsed magnetic field, and γ1 is the nuclear spin gyromagnetic ratio of the first inert gas. For example, the first inert gas is... 3 For He, γ1 = 0.0324 Hz / nT, and γ2 is the nuclear spin gyromagnetic ratio of the second inert gas, for example, the second inert gas is... 21 If Ne, then γ2 = 0.003361 Hz / nT.

[0049] The expression for the measured decaying oscillation signal in step (5) is:

[0050]

[0051] in, Here, A is the detected x-axis electron spin polarization, A is the amplitude of the first type of nuclear spin decay oscillation signal, f1 is the frequency of the first type of nuclear spin decay oscillation, which is related to the magnetic field and angular velocity, and t is time. is the fitted phase of the first type of nuclear spin decay oscillation signal, T1 is the relaxation time of the first type of nuclear spin, B is the amplitude of the second type of nuclear spin decay oscillation signal, and f2 is the frequency of the second type of nuclear spin decay oscillation, which is related to the magnetic field and angular velocity. T2 is the phase fitting of the second type of nuclear spin decay oscillation signal, T2 is the relaxation time of the second type of nuclear spin, and C is a constant term.

[0052] In step (6), the decaying oscillation frequencies f1 and f2 are obtained from step (5), and the calculated frequency difference Δf is related to the final angular velocity as follows:

[0053]

[0054] Where Δf is the calculated frequency difference of the damped oscillation signal, B is the applied bias magnetic field, and Ω is the angular velocity to be measured.

[0055] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. An inertial metrology method based on alkali noble gas hybrid spin ensemble, characterized in that, The method comprises the following steps: Step 1, polarizing alkali metal electron spins along the z direction by using alkali metal resonance circularly polarized light for alkali metal inert gas mixed spin ensemble; Step 2, realizing spin-exchange optical pumping of two kinds of inert gas nuclear spins through spin exchange between alkali metal electron spins and inert gas nuclear spins; Step 3, applying a light pulse sequence to realize the inversion of alkali metal electron spins along the z direction; Step 4, applying a nuclear spin pulse magnetic field to invert the polarization of two kinds of nuclear spins from the z direction to the x direction to realize the maximum of the transverse polarization component; Step 5, detecting the x direction polarization rate of alkali metal electron spins, in-situ measuring the nuclear spin equivalent magnetic field, and obtaining the decay oscillation frequency information by fitting the decay oscillation signal expression; Step 6, calculating the angular velocity by using the nuclear spin gyromagnetic ratio of inert gas and the decay oscillation frequencies of two kinds of nuclear spins; The decay oscillation signal expression in step 5 is as follows: wherein, is the detected x-direction electronic spin polarizability, A is the first kind of nuclear spin decay oscillation signal amplitude, f1 is the first kind of nuclear spin decay oscillation frequency, t is time, is the first kind of nuclear spin decay oscillation signal fitting phase, T1 is the relaxation time of the first kind of nuclear spin, B is the second kind of nuclear spin decay oscillation signal amplitude, f2 is the second kind of nuclear spin decay oscillation frequency, is the second kind of nuclear spin decay oscillation signal fitting phase, T2 is the relaxation time of the second kind of nuclear spin, C is a constant term; The relationship expression in step 6 comprises the following relationships: Where Δf is the calculated decay oscillation signal frequency difference, B is the applied nuclear spin pulse magnetic field, Ω is the to-be-measured angular velocity; γ1 is the nuclear spin gyromagnetic ratio of the first kind of inert gas, and γ2 is the nuclear spin gyromagnetic ratio of the second kind of inert gas.

2. The inertial metrology method based on alkali noble gas hybrid spin ensemble according to claim 1, characterized in that, The light pulse sequence in step 3 is σ+ / σ- inversion, σ+ refers to left circularly polarized light, and σ- refers to right circularly polarized light, and the light pulse frequency is much larger than the nuclear spin precession frequency.

3. The alkali noble gas hybrid spin ensemble based inertial measurement method of claim 1, wherein, The pulsed magnetic field in step 4 refers to the y-axis pulsed magnetic field B y , B y , which makes the polarization of the two nuclei flip from the z-axis to the x-axis around the y-axis, and the action time t p of B y is determined according to the following formula: t p = (1 / 2 x n + 1 / 4) / (γ1B y = (1 / 2 x m + 1 / 4) / (γ2B y ), where n is an integer > 0, m is an integer > 0, B y is the amplitude of the y-pulsed magnetic field, γ1is the nuclear spin gyromagnetic ratio of the first noble gas, and γ2is the nuclear spin gyromagnetic ratio of the second noble gas.

4. The inertial metrology method based on alkali noble gas hybrid spin ensemble according to claim 3, characterized in that, The first inert gas is 3 He, γ1 = 0.0324 Hz / nT, the second inert gas is 21 Ne, γ2 = 0.003361 Hz / nT.

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