Inertia metering method based on alkali metal inert gas mixed spinning ensemble

Abstract

The invention relates to an inertia metering method based on an alkali metal inert gas mixed spinning ensemble. The method can accurately realize metering of weak angular velocity. According to the method, equivalent magnetic fields of two kinds of nuclear spins (such as 3He and 21Ne) are measured in situ through alkali metal electron spins, then nuclear spin precession frequencies directly related to the magnetic fields and angular velocity are obtained, the frequencies of the two kinds of nuclear spins are compared to eliminate response of the magnetic fields, the alkali metal equivalent magnetic fields are overturned in combination with an optical pulse sequence, and system errors caused by the alkali metal equivalent magnetic fields are reduced. The method is reasonable, the experimental operation is simple, the method is suitable for the mixed spinning ensemble, the accurate measurement of the angular velocity can be realized, and a foundation is provided for the development of a high-precision inertia metering device.

Description

Technical Field

[0001] The present invention relates to the field of inertial measurement technology, and in particular to an inertial measurement method based on an alkali metal inert gas mixed spin ensemble, which 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 basis for the research of high-precision inertial measurement. Background Art

[0002] In the acquisition and perception of carrier motion information, it is necessary to accurately measure the angular velocity. With the continuous development of inertial measurement, the measurement method has undergone a transformation from mechanical to optical to atomic, and is constantly moving towards high precision.

[0003] At present, the results of zero bias stability are of great concern in the measurement of angular velocity. It evaluates the stability of the output signal when there is no input signal. Specifically, it describes the degree to which the output signal deviates from the zero reference value under constant conditions when the sensor is not affected by the outside world, and the stability of this deviation over time. However, what is more important for measurement is whether the measurement is accurate, that is, how close the measurement result is to the true result. The existing methods can only calibrate the output result by applying an input signal in terms of accuracy. Summary of the invention

[0004] In view of the defects or shortcomings in the prior art, the present invention provides an inertial measurement method based on an alkali metal inert gas mixed spin ensemble, which can solve the problem of weak angular velocity calibration, and the angular velocity calibration is reasonable and the experimental operation is simple, providing a basis 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 an alkali metal inert gas mixed spin ensemble, characterized in that it comprises the following steps:

[0007] Step 1, for the alkali metal noble gas mixed spin ensemble, using alkali metal resonant circularly polarized light to polarize the alkali metal electron spin along the z direction;

[0008] 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;

[0009] Step 3, applying a sequence of light pulses to achieve the flipping of the alkali metal electron spin along the z direction;

[0010] Step 4, applying a nuclear spin pulse magnetic field to flip the two nuclear spin polarizations from the z direction to the x direction to maximize the transverse polarization component;

[0011] Step 5, detecting the x-direction polarizability of the alkali metal electron spin, measuring the nuclear spin equivalent magnetic field in situ, and obtaining the attenuated oscillation frequency information by fitting the attenuated oscillation signal expression;

[0012] Step 6, using the gyromagnetic ratio of the inert gas nuclear spins and the decay oscillation frequency of the two nuclear spins, the angular velocity is calculated.

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

[0014] The pulse magnetic field in step 4 refers to the y-axis pulse magnetic field B y , B y The effect of the two nuclear spin polarizations is to flip from the z-axis to the x-axis around the y-axis, and B is determined according to the following formula y The action time 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, B y is the amplitude of the pulsed magnetic field in the y direction, γ1 is the nuclear spin gyromagnetic ratio of the first noble gas, and γ2 is the nuclear spin gyromagnetic ratio of the second noble gas.

[0017] The 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 of the decay oscillation signal in step 5 is as follows:

[0019]

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

[0021] Step 6 includes the following relational expressions:

[0022]

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

[0024] The advantages of the present invention compared with the prior art are:

[0025] (1) The present invention utilizes a physical constant, namely the gyromagnetic ratio of nuclear spins, to perform inertial measurement, and traces the measured input signal back to a physical constant with higher accuracy, thereby directly realizing the absolute value measurement of angular velocity.

[0026] (2) The method of the present invention is reasonable and the experimental operation is simple, which provides a basis for the development of high-precision inertial measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic flow chart of an inertial metrology method based on an alkali metal inert gas mixed spin ensemble according to the present invention. Figure 1 The method includes step 1, continuous optical pumping to polarize the alkali metal in the z direction; step 2, spin exchange optical pumping to polarize the two inert gases; step 3, optical pulse sequence to flip the electron spin in the z direction; step 4, y-direction pulse magnetic field to flip the nuclear spin to the transverse direction; step 5, fitting the attenuated oscillation signal to obtain the frequency; and step 6, frequency difference to calculate the angular velocity. DETAILED DESCRIPTION

[0028] Below is the attached figure ( Figure 1 ) and Examples illustrate the present invention.

[0029] Figure 1 The figure is a schematic flow chart of an inertial measurement method based on an alkali metal inert gas mixed spin ensemble according to the present invention. Figure 1As shown, an inertial metrology method based on an alkali metal inert gas mixed spin ensemble includes the following steps: step 1, for the alkali metal inert gas mixed spin ensemble, using alkali metal resonant circularly polarized light to polarize the alkali metal electron spin along the z direction; step 2, through the spin exchange between the alkali metal electron spin and the inert gas nuclear spin, the spin exchange optical pumping of the two inert gas nuclear spins is realized; step 3, applying a light pulse sequence to realize the flipping of the alkali metal electron spin along the z direction; step 4, applying a nuclear spin pulse magnetic field to flip the polarization of the two nuclear spins from the z direction to the x direction to achieve the maximum transverse polarization component; step 5, detecting the x-direction polarization rate of the alkali metal electron spin, measuring the nuclear spin equivalent magnetic field in situ, and obtaining the decayed oscillation frequency information by fitting the decayed oscillation signal expression; step 6, using the inert gas nuclear spin gyromagnetic ratio, and using the decayed oscillation frequency of the two nuclear spins to calculate the angular velocity.

[0030] In step 3, the optical pulse sequence is a σ+ / σ- flip, σ+ refers to left-handed circularly polarized light, σ- refers to right-handed circularly polarized light, and the optical pulse frequency is much greater than the nuclear spin precession frequency. In step 4, the pulse magnetic field refers to the y-axis pulse magnetic field B y , B y The effect of the two nuclear spin polarizations is to flip from the z-axis to the x-axis around the y-axis, and B is determined according to the following formula y The action time 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, B y is the amplitude of the pulsed magnetic field in the y direction, γ1 is the nuclear spin gyromagnetic ratio of the first noble gas, and γ2 is the nuclear spin gyromagnetic ratio of the second noble gas. For example, the first noble gas is 3 He, γ1 = 0.0324 Hz / nT, the second inert gas is 21 Ne,γ2=0.003361Hz / nT.

[0033] The expression of the decay oscillation signal in step 5 is as follows:

[0034]

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

[0036] Step 6 includes the following relational expressions:

[0037]

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

[0039] The present invention relates to an inertial metrology method based on an alkali metal inert gas mixed spin ensemble, which can accurately measure weak angular velocity. The method measures two nuclear spins (such as 3 He and 21 Ne), and then obtain the nuclear spin precession frequency directly related to the magnetic field and angular velocity, compare the frequency elimination magnetic field response of the two nuclear spins, and combine the optical pulse sequence to flip the alkali metal equivalent magnetic field to reduce the system error caused by it. The method of the invention is reasonable, the experimental operation is simple, it is suitable for the mixed spin ensemble, and can realize the accurate measurement of angular velocity, which provides a basis for the development of high-precision inertial measurement devices.

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

[0041] Step (1): polarize the alkali metal electron spin along the z direction using alkali metal resonant circularly polarized light.

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

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

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

[0046] Step (6): Using the gyromagnetic ratio of the inert gas nuclear spins, the angular velocity is calculated using the decay oscillation frequency of the two nuclear spins.

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

[0048] The pulsed magnetic field in step (4) refers to B y The magnetic field causes the two nuclear spin polarizations to flip from the z-axis to the x-axis around the y-axis, requiring the magnetic field to act for a period of time 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 is the time for applying the pulse magnetic field in the y direction, B y is the amplitude of the pulsed magnetic field in the y direction, γ1 is the nuclear spin gyromagnetic ratio of the first noble gas, for example, the first noble gas is 3 He, then γ1=0.0324Hz / nT, γ2 is the nuclear spin gyromagnetic ratio of the second noble gas, for example, the second noble gas is 21 Ne, then γ2=0.003361Hz / nT.

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

[0050]

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

[0052] In step (6), the attenuated oscillation frequencies f1 and f2 are obtained from step (5), and the relationship between the calculated frequency difference Δf and the final angular velocity is:

[0053]

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

[0055] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. An inertial metrology method based on an alkali metal inert gas mixed spin ensemble, characterized in that: The following steps are involved: Step 1, for the alkali metal noble gas mixed spin ensemble, using alkali metal resonant circularly polarized light to polarize the alkali metal electron spin along the z direction; 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 sequence of light pulses to achieve the flipping of the alkali metal electron spin along the z direction; Step 4, applying a nuclear spin pulse magnetic field to flip the two nuclear spin polarizations from the z direction to the x direction to maximize the transverse polarization component; Step 5, detecting the x-direction polarizability of the alkali metal electron spin, measuring the nuclear spin equivalent magnetic field in situ, and obtaining the attenuated oscillation frequency information by fitting the attenuated oscillation signal expression; Step 6, using the gyromagnetic ratio of the inert gas nuclear spins and the decay oscillation frequency of the two nuclear spins, the angular velocity is calculated.

2. The inertial measurement method based on the alkali metal inert gas mixed spin ensemble according to claim 1, characterized in that: In step 3, the light pulse sequence is a flip of σ+ / σ-, σ+ refers to left-handed circularly polarized light, σ- refers to right-handed circularly polarized light, and the light pulse frequency is much greater than the nuclear spin precession frequency.

3. The inertial measurement method based on the alkali metal inert gas mixed spin ensemble according to claim 1, characterized in that: The pulse magnetic field in step 4 refers to the y-axis pulse magnetic field B y , B y The effect of the two nuclear spin polarizations is to flip from the z-axis to the x-axis around the y-axis, and B is determined according to the following formula y The action time t p : 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, B y is the amplitude of the pulsed magnetic field in the y direction, γ1 is the nuclear spin gyromagnetic ratio of the first noble gas, and γ2 is the nuclear spin gyromagnetic ratio of the second noble gas.

4. The inertial measurement method based on the alkali metal inert gas mixed 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=0.003361Hz / nT.

5. The inertial measurement method based on the alkali metal inert gas mixed spin ensemble according to claim 1, characterized in that: The expression of the decay oscillation signal in step 5 is as follows: in, is the detected x-direction electron spin polarization rate, A is the amplitude of the first nuclear spin decay oscillation signal, f1 is the first nuclear spin decay oscillation frequency, t is the time, is the fitting phase of the first nuclear spin decay oscillation signal, T1 is the relaxation time of the first nuclear spin, B is the amplitude of the second nuclear spin decay oscillation signal, f2 is the second nuclear spin decay oscillation frequency, is the fitting phase of the decay oscillation signal of the second nuclear spin, T2 is the relaxation time of the second nuclear spin, and C is a constant term.

6. The inertial measurement method based on the alkali metal inert gas mixed spin ensemble according to claim 1, characterized in that: Step 6 includes the following relational expressions: Where Δf is the calculated frequency difference of the decaying oscillation signal, B is the applied bias magnetic field, and Ω is the angular velocity to be measured.

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