Multi-component atomic gravity gradient measurement device and method based on rotating platform

Abstract

The application discloses a multi-component atomic gravity gradient measuring device based on a rotating platform, which comprises a rotating platform and four atomic interference measuring units which are equally spaced along the circumference of the platform on the platform table of the rotating platform; the atomic interference measuring units on both sides of the center of the platform are connected through corresponding vacuum pipes, and the two vacuum pipes intersect and are in communication with each other. The application also discloses a multi-component atomic gravity gradient measuring method based on a rotating platform, which comprises the following steps: setting the direction of the rotating platform twice, simultaneously and repeatedly performing the cold atom preparation, cold atom interference and fluorescence detection on each atomic interference measuring unit, and performing a one-way collinear gravity gradient calculation process to obtain the one-way collinear gravity gradient measurement value in the corresponding measuring line direction and the one-way collinear gravity gradient measurement value in the opposite direction of the measuring line direction; and then calculating each atomic gravity gradient component corresponding to the reference direction. The application has the positive effects of strong common-mode noise suppression and elimination of various measurement errors.

Description

Technical Field

[0001] This invention belongs to the field of inertial measurement technology based on atomic interferometry, and more specifically relates to a multi-component atomic gravity gradient measurement device based on a rotating platform, and also relates to a multi-component atomic gravity gradient measurement method based on a rotating platform, which is suitable for precise gravity field surveying. Technical Background

[0002] The gravitational gradient is the spatial rate of change of gravitational acceleration; a complete gravitational gradient field... Mathematically, it can be represented by a 3×3 matrix:

[0003] ,

[0004] in Represents gravitational acceleration Directional components exist The rate of change of the direction of gravity. Since the gravitational field is conservative, the components of the gravitational gradient have the following relationship:

[0005] ,direction ,

[0006] ,

[0007] Therefore, the nine matrix components of the gravity gradient contain five independent components.

[0008] Compared to a gravitational field, a gravitational gradient field has higher spatial resolution and contains information in multiple dimensions, thus enabling a more accurate inversion of the surrounding mass distribution. Practice has shown that the more components measured, the higher the inversion accuracy. Furthermore, a gravitational gradiometer with a differential mechanism can suppress common-mode noise, such as vibration noise, thus better meeting the measurement needs under harsh external conditions. Due to these technical characteristics, gravitational gradiometers have significant applications in resource exploration, underground target detection, geophysics, and environmental research. Currently, international implementation schemes for gravitational gradiometers include rotating accelerometer schemes, superconducting schemes, electrostatic levitation schemes, and cold atom interferometry schemes. Among these, the cold atom interferometry scheme, based on novel quantum technology and using atomic energy levels and related transitions as a benchmark, possesses intrinsic accuracy and stability similar to atomic clocks. Therefore, the atomic interferometric gravitational gradiometer has advantages such as high precision, low drift, and room-temperature device operation, making it a promising next-generation gravitational gradiometer.

[0009] An atomic interferometer is an interferometer based on the wave nature of atoms. Its core physical process involves using lasers to manipulate atoms for beam splitting, reflection, and recombination. Simultaneously, the phase of the laser is written into the phase of the atomic matter wave. By measuring the phase of the atomic interference fringes, changes in the spatial position of the atoms are sensed, thereby enabling the measurement of inertial physical quantities such as (gravitational) acceleration, gravitational gradient, and rotation. In this process, short-term jitter and long-term drift of the laser phase sensed by the atoms directly affect the noise level and stability of the measurement results. Therefore, environmental vibration noise will also enter the measurement results by perturbing the laser phase, thus becoming a bottleneck factor restricting the measurement accuracy of atomic gravimeters (accelerometers).

[0010] In gravity gradient measurement schemes, a gravity gradient component is typically obtained by differential measurement using two spatially discrete atomic interferometers. This involves dividing the difference in gravitational acceleration between the two points by the distance between them. Since the direction of the Raman laser operating the interferometer is the direction of the acceleration measurement (projection), the diagonal component of the gravity gradient matrix... This can be achieved directly through collinear measurement, meaning the Raman laser's direction is aligned with the spatial separation direction of the two atomic interferometers, allowing the Raman laser to directly penetrate and synchronously operate both interferometers. During this measurement process, environmental noise (represented by vibration noise) and internal noise (represented by laser source phase noise) simultaneously disturb the two interferometers, thus effectively suppressing them using a differential algorithm. Furthermore, the off-diagonal components of the gravity gradient matrix... ( To directly measure this gradient, the direction of the operating laser needs to be orthogonal to the spatial separation direction of the two atomic interferometers. Therefore, the aforementioned through-line measurement is impossible. Furthermore, neither using two independent operating lasers nor adding a folding element to the optical path can effectively suppress common-mode noise from environmental vibrations. Consequently, all current high-precision gravity gradient measurements based on atomic interferometry schemes internationally focus on the diagonal component of the gravity gradient. High-precision measurements of the off-diagonal components are not reported in the literature, highlighting the urgent need for corresponding technical solutions.

[0011] In addition, it is related to measuring the vertical component (i.e., the diagonal component of the gravitational gradient). Unlike the atomic interferometer gravimeter, the horizontal component (corresponding to the horizontal component of the gravity gradient) is different. , In atomic interferometric gravimetric gradiometers, since the atomic flight trajectories are vertical, while Raman lasers and quantized magnetic fields need to be applied horizontally, at least two spatially separated Raman laser beams and a pair of magnetic field coils are required to achieve coherent manipulation of the atoms. This significantly degrades the common mode of the Raman lasers and the uniformity of the magnetic field compared to vertical atomic interferometric gravimetric gradiometers, ultimately making it difficult to assess the absolute measurement error. To date, no horizontal component atomic interferometric gravimetric gradiometer has been developed internationally to measure the absolute horizontal gravity gradient; only the relative (change) of the horizontal gravity gradient can be measured.

[0012] In summary, multi-component atomic interferometric gravity gradiometers have broad application prospects in fields such as resource exploration. However, there is currently no mature technical solution based on atomic interferometers to achieve precise measurement of the off-diagonal components of the gravity gradient. Furthermore, the absolute measurement (error assessment) of the horizontal component of the gravity gradient remains a technical challenge. The multi-component atomic gravity gradient measurement device and method based on a rotating platform proposed in this invention are of great significance for solving the problems of high-precision multi-component measurement of atomic gravity gradiometers and accurate error assessment of the horizontal component of the gravity gradient. Summary of the Invention

[0013] To address the challenge of existing technologies in measuring multi-component gravity gradients with high noise common-mode suppression, this invention proposes a multi-component atomic gravity gradient measurement device and method based on a rotating platform. This invention enables direct common-mode measurement of the diagonal components of the gravity gradient in the horizontal plane using a common Raman laser beam in a collinear manner. Then, by using a rotating platform to solve mathematical equations, it indirectly measures the values ​​of the other non-diagonal component and the vertical component in the horizontal plane. This method achieves high-precision multi-component measurement of the gravity gradient while maintaining high noise suppression and low system complexity.

[0014] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0015] A multi-component atomic gravity gradient measurement device based on a rotating platform includes a rotating platform and four atomic interferometric measurement units that are equally spaced along the circumference of the platform.

[0016] Each atomic interferometry unit contains a vacuum cavity comprising an interconnected cold atom preparation cavity and an interferometry cavity, with the cold atom preparation cavity located below the interferometry cavity; an upward-cooled laser emitter is mounted below the cold atom preparation cavity, a downward-cooled laser emitter is mounted above the interferometry cavity, and four horizontally cooled laser emitters are on the same horizontal plane as the center of the cold atom preparation cavity;

[0017] The atomic interferometric measurement units symmetrically distributed on both sides of the center of the rotating platform are grouped into a pair of atomic interferometric measurement units. The interference cavities of each pair of atomic interferometric measurement units are connected through corresponding vacuum pipes. The two vacuum pipes intersect to form a vacuum interconnection pipe, and the vacuum is interconnected at the intersection.

[0018] Two Raman laser emitters are arranged vertically on the outer side of the middle of each interference cavity. The Raman laser emitters are symmetrically distributed about the central axis of the interference cavity with respect to the connection point between the Raman laser emitter and the vacuum pipe on the corresponding interference cavity. The photodetector is located on the lower outer side of the interference cavity.

[0019] The two coils in the anti-Helmholtz coil pair are symmetrically distributed in the upper and lower parts of the cold atom preparation cavity, and the line connecting the centers of the two coils in the anti-Helmholtz coil pair is collinear with the central axis of the cold atom preparation cavity; the two coils in the bias magnetic field coil pair are symmetrically distributed on both sides of the vacuum cavity, and the direction of the line connecting the centers of the two coils in the bias magnetic field coil pair is parallel to the extension direction of the vacuum pipe connected to the corresponding interference cavity.

[0020] Each atomic interferometry unit, as described above, is externally fitted with a corresponding magnetic shield.

[0021] The Raman laser emitted from the two Raman laser emitters outside each of the interference cavities as described above enters from one end of the corresponding vacuum pipe and enters another interference cavity connected to the vacuum pipe through the other end of the corresponding vacuum pipe.

[0022] As mentioned above, the vacuum interconnect pipes are made of titanium alloy.

[0023] The inner wall of the vacuum interconnected pipe is polished as described above.

[0024] As mentioned above, the magnetic shielding cover is made of permalloy.

[0025] The multi-component atomic gravity gradient measurement method based on a rotating platform, utilizing the multi-component atomic gravity gradient measurement device based on a rotating platform as described above, includes the following steps:

[0026] Step 1: Determine the geographical direction as east. The reference direction of the axis is north. The axis reference direction is perpendicular to the ground direction. Axial reference direction; Construct a multi-component atomic gravity gradient measurement device based on a rotating platform so that the platform surface of the rotating platform is aligned with the reference direction. The axis reference direction is perpendicular;

[0027] Step 2: Using the extension direction of one vacuum pipe as the first measuring line direction and the extension direction of the other vacuum pipe as the second measuring line direction; rotate the rotating platform so that the first measuring line direction aligns with... The axis forms an angle with the reference direction, denoted as the first angle. The corresponding first survey line direction is denoted as the initial first survey line direction. The direction of the second survey line is denoted as the initial second survey line direction. ;

[0028] Step 3: For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times in a loop, and then performs a unidirectional collinear gravity gradient calculation process based on the detected atomic interference fringes to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction;

[0029] Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the initial first positive collinear gravity gradient measurement value. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the initial second positive collinear gravity gradient measurement value. ;

[0030] Step 4: Rotate the rotating platform by 180 degrees. For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times in a loop. Then, based on the detected atomic interference fringes, perform a unidirectional collinear gravity gradient calculation process to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction.

[0031] Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the initial first reverse collinear gravity gradient measurement value. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the initial second reverse collinear gravity gradient measurement value. ;

[0032] The average collinear gravity gradient measurement is calculated using the following formula:

[0033] ,

[0034] ,

[0035] in, The initial first average collinear gravity gradient measurement value; This is the initial second average collinear gravity gradient measurement value;

[0036] Step 5: Change the angle of the rotating platform so that the direction of the first measuring line is aligned with... The included angle of the axial reference direction becomes the second included angle. The corresponding first survey line direction is denoted as the first survey line direction after rotation. The corresponding direction of the second survey line is denoted as the direction of the second survey line after rotation. ;

[0037] Step 6: For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times in a loop, and then performs a unidirectional collinear gravity gradient calculation process based on the detected atomic interference fringes to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction;

[0038] Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the first positive collinear gravity gradient measurement value after rotation. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the second positive collinear gravity gradient measurement value after rotation. ;

[0039] Step 7: Rotate the rotating platform by 180 degrees. For each pair of atomic interferometry units: Each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times in a loop. Then, based on the detected atomic interferometry fringes, perform a unidirectional collinear gravity gradient calculation process to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction.

[0040] Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the first reverse collinear gravity gradient measurement value after rotation. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the second reverse collinear gravity gradient measurement value after rotation. ;

[0041] The corresponding average collinear gravity gradient measurement value is calculated using the following formula:

[0042] ,

[0043] ,

[0044] in, This is the measured value of the first average collinear gravity gradient after rotation; This is the measured value of the second average collinear gravity gradient after rotation;

[0045] Step 8: Measure the value , , , Substitute into the following formula to solve for the diagonal components of the gravitational gradient. , and the off-diagonal component of the gravity gradient :

[0046] ,

[0047] ,

[0048] ,

[0049] .

[0050] The calculation process for the unidirectional collinear gravity gradient, as described above, specifically includes the following steps:

[0051] The number of atoms in the ground state energy level after interference is obtained by the interference signal of each atom in the atomic interference fringes detected by the photodetector;

[0052] A series of layout pairs measured by centering a pair of atomic interferometry units ( , Substitute the following equations for fitting:

[0053] ,

[0054] in, , , , , , For the fitting parameters, , These represent the layout number of each atomic interferometry unit in a pair of atomic interferometry units;

[0055] Calculate the phase difference between two atomic interferometer units in an atomic interferometer unit pair. ;

[0056] Phase difference Substituting into the following formula, we obtain the unidirectional collinear gravity gradient measurement values ​​for the corresponding survey line direction:

[0057] ,

[0058] In the above formula, This is a measurement of the unidirectional collinear gravity gradient. The effective wave vector of the Raman laser. The distance between two atomic interferometry units connected in the same vacuum pipe. The time interval between two adjacent Raman laser pulses in the three Raman laser pulses.

[0059] The multi-component atomic gravity gradient measurement method based on a rotating platform, as described above, further includes the following step: dividing the diagonal components of the gravity gradient obtained in step 8... , Substitution The diagonal components of the gravitational gradient are obtained. .

[0060] When the first included angle is as described above The second included angle ,

[0061] ,

[0062] ,

[0063] ,

[0064] in, The first included angle The initial first average collinear gravity gradient measurement value at time , The first included angle The initial second average collinear gravity gradient measurement at time , The second included angle The measured value of the first average collinear gravitational gradient after rotation. The second included angle The measured value of the second average collinear gravity gradient after rotation;

[0065] diagonal components of gravity gradient Or the diagonal component of the gravity gradient .

[0066] Compared with the prior art, the present invention has the following advantages:

[0067] This invention enables the calculation of the diagonal component of the gravitational gradient using a single device. , , and the off-diagonal component of the gravity gradient Independent measurements; and all gravity gradient components, especially the off-diagonal components. Both measurements are achieved through collinear measurements, meaning the Raman laser can directly penetrate and synchronously operate the two atomic interferometers. During the measurement process, environmental noise, represented by vibration noise, and internal noise, represented by laser source phase noise, simultaneously disturb the two interferometers and can therefore be effectively suppressed using a differential algorithm. This eliminates the adverse effects of vibration noise and laser source phase noise, enabling high signal-to-noise ratio measurements in noisy environments.

[0068] Furthermore, the composition of measurement errors in atomic interferometers is extremely complex, especially in atomic interferometric gravity gradiometers that measure horizontal components. The non-common-mode factor of Raman lasers and the inhomogeneity of quantized magnetic fields make error assessment even more difficult. In the measurement method based on a rotating platform proposed in this invention, by exchanging the relative orientations of two atomic interferometric measurement units on the same measurement line and then averaging the difference between the forward and reverse unidirectional collinear gravity gradient measurements, measurement errors tied to the instrument structure can be eliminated. These errors include a series of important errors such as magnetic field errors, self-gravity errors, and Raman wavefront distortion errors, thereby improving measurement accuracy. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the multi-component atomic gravity gradient meter based on a rotating platform in this invention.

[0070] Figure 2 This is a schematic diagram of a method for measuring multi-component gravitational gradients by rotating a platform, where (a) is the first included angle. Schematic diagram of the survey line direction on the rotating platform, (b) is the second included angle. A schematic diagram of the measuring line direction on the rotating platform.

[0071] In the diagram: P—rotating platform; A1—first atomic interferometry unit; A2—second atomic interferometry unit; A3—third atomic interferometry unit; A4—fourth atomic interferometry unit; C—vacuum interconnection pipe;

[0072] —Initial first survey line direction; —Initial second survey line direction; —Direction of the first survey line after rotation; —Direction of the second measuring line after rotation;

[0073] 1—Vacuum cavity; 101—Cold atom preparation cavity; 102—Interference cavity; 2—Anti-Helmholtz coil pair; 3—Bias magnetic field coil pair; 401—Upward-cooled laser emitter; 402—Downward-cooled laser emitter; 403—Horizontally cooled laser emitter; 5—Raman laser emitter; 6—Photodetector; 7—Magnetic shield. Detailed Implementation

[0074] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to examples. The embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0075] Example 1

[0076] A multi-component atomic gravity gradient measurement device based on a rotating platform, such as Figure 1As shown: It includes a rotating platform P, four atomic interferometry units and a vacuum interconnection pipe C. Each of the four atomic interferometry units includes a vacuum cavity 1, an anti-Helmholtz coil pair 2, a bias magnetic field coil pair 3, an upward-cooled laser emitter 401, a downward-cooled laser emitter 402, four horizontally cooled laser emitters 403, two Raman laser emitters 5, a photodetector 6 and a magnetic shield 7.

[0077] The spatial positions and connections of each component are as follows:

[0078] Four atomic interferometry units (first atomic interferometry unit A1, second atomic interferometry unit A2, third atomic interferometry unit A3, and fourth atomic interferometry unit A4) are equally spaced along the circumference of the platform surface of the rotating platform P, so that the four atomic interferometry units are symmetrically installed on the platform surface of the rotating platform P.

[0079] Each atomic interferometry unit includes a vacuum cavity 1 comprising an interconnected cold atom preparation cavity 101 and an interferometer cavity 102. The cold atom preparation cavity 101 is located below the interferometer cavity 102. An upward-cooled laser emitter 401 is installed below the cold atom preparation cavity 101, and a downward-cooled laser emitter 402 is installed above the interferometer cavity 102. Four horizontally cooled laser emitters 403 are located in the same horizontal plane as the center of the cold atom preparation cavity 101. All cooled laser emitters (including the upward-cooled laser emitter 401, the downward-cooled laser emitter 402, and the horizontally cooled laser emitter 403) point towards the center of the cold atom preparation cavity 101.

[0080] The atomic interferometry units symmetrically distributed on both sides of the center of the rotating platform P are grouped into a pair of atomic interferometry units. In this embodiment, the first atomic interferometry unit A1 and the third atomic interferometry unit A3 are two atomic interferometry units symmetrically distributed on both sides of the center of the rotating platform P, belonging to a pair of atomic interferometry units; the second atomic interferometry unit A2 and the fourth atomic interferometry unit A4 are two atomic interferometry units symmetrically distributed on both sides of the center of the rotating platform P, belonging to another pair of atomic interferometry units. The interference cavities 102 in each pair of atomic interferometry units are connected by corresponding vacuum pipes. The two vacuum pipes intersect to form a vacuum interconnection pipe C, and the vacuum pipes are interconnected at the intersection.

[0081] Two Raman laser emitters 5 are arranged vertically on the outer side of the center of each interference cavity 102. The Raman laser emitters 5 are symmetrically distributed about the central axis of the interference cavity 102 at the connection point between the Raman laser emitter 5 and the vacuum pipe connecting to the vacuum interconnection pipe C on the corresponding interference cavity 102. A photodetector 6 is located on the lower outer side of the interference cavity 102.

[0082] The two coils in anti-Helmholtz coil pair 2 are symmetrically distributed at the upper and lower parts of the cold atom preparation cavity 101, and the line connecting the centers of the two coils in anti-Helmholtz coil pair 2 is collinear with the central axis of the cold atom preparation cavity 101. The two coils in bias magnetic field coil pair 3 are symmetrically distributed on both sides of the vacuum cavity 1, and the direction of the line connecting the centers of the two coils in bias magnetic field coil pair 3 is parallel to the extension direction of the vacuum pipe connected to the interference cavity 102 in the corresponding vacuum cavity 1.

[0083] Each atomic interferometry unit is externally fitted with a corresponding magnetic shield 7.

[0084] In this embodiment, since the four atomic interferometry units are equally spaced along the circumference of the platform on the rotating platform P, the outer lines (i.e., sequential lines) of the projection of the four atomic interferometry units onto the horizontal plane form a regular quadrilateral, and the diagonal lines are perpendicular to each other to form a cross shape; the two pairs of Raman laser emitters 5 of the two pairs of atomic interferometry units located on the diagonal are respectively installed at both ends of the diagonal, and are in a diagonal-direction-oriented firing configuration.

[0085] 1) Rotating platform P: The rotating platform P includes a rotating shaft and a platform connected to the upper end of the rotating shaft. The platform surface is installed horizontally. The rotating shaft of the rotating platform P is located at the center of the platform, and the extension direction of the rotating shaft is perpendicular to the platform surface. The rotation can be driven manually or by a motor.

[0086] 2) Atomic interferometry unit: It is an upward-throwing atomic interferometry unit.

[0087] 3) Vacuum interconnected pipe C: such as Figure 1 The cross-shaped vacuum component shown is made of titanium alloy and is hollow inside. The height of the hollow part can accommodate two vertically distributed Raman lasers that propagate horizontally (in this embodiment, the Raman lasers emitted from the two Raman laser emitters 5 outside each interference cavity 102 enter from one end of the corresponding vacuum pipe and enter another interference cavity 102 connected to the vacuum pipe through the other end of the corresponding vacuum pipe). The inner wall of the vacuum interconnection pipe C is polished.

[0088] 4) Vacuum cavity 1: It consists of a metal body and an optical window. The optical window is located in the area of ​​the metal body where light needs to pass through.

[0089] 5) Anti-Helmholtz coil pair 2: This consists of two coils symmetrically mounted on the upper and lower parts of the cold atom preparation cavity 101. The coils in the anti-Helmholtz coil pair 2 are made of enameled copper wire, and the currents in the two coils are in opposite directions, which can generate a quadrupole magnetic field with zero central strength.

[0090] 6) Bias magnetic field coil pair 3: such as Figure 1The coil pair shown contains two coils, symmetrically arranged. The coils of bias magnetic field coil pair 3 are wound with enameled copper wire, and the current in both coils is in the same direction, which can generate a bias magnetic field with uniform central strength.

[0091] 7) Cooled laser emitter: including uplink cooled laser emitter 401, downlink cooled laser emitter 402, and horizontal cooled laser emitter 403, all of which include optical components such as fiber collimators, waveplates, and mirrors, and can output collimated circularly polarized laser beams.

[0092] 8) Raman laser emitter 5: includes optical components such as fiber collimator, waveplate, and mirror, and can output collimated circularly polarized laser beam.

[0093] 9) Photodetector 6: It is a semiconductor phototube or photomultiplier tube that can convert atomic fluorescence signals into current or voltage signals.

[0094] 10) Magnetic shield 7: such as Figure 1 The shell-shaped structure shown is made of high magnetic permeability materials such as permalloy and has the function of shielding the static magnetic field of the environment.

[0095] Example 2

[0096] The multi-component atomic gravity gradient measurement method based on a rotating platform, utilizing the multi-component atomic gravity gradient measurement device based on a rotating platform described in Example 1, includes the following steps:

[0097] Step 1: Determine the geographical direction as east. The reference direction of the axis is north. The axis reference direction is perpendicular to the ground direction. Axial reference direction; Construct a multi-component atomic gravity gradient measurement device based on a rotating platform so that the platform surface of the rotating platform P is aligned with the reference direction. The axis reference direction is perpendicular.

[0098] Step 2: Using the extension direction of one vacuum pipe connecting to the corresponding atomic interferometry unit as the first measurement line direction, and the extension direction of another vacuum pipe connecting to the corresponding atomic interferometry unit as the second measurement line direction; rotate the rotating platform P so that the first measurement line direction aligns with... The axis forms an angle with the reference direction, denoted as the first angle. The corresponding first survey line direction is denoted as the initial first survey line direction. The direction of the second survey line is denoted as the initial second survey line direction. At this point, the initial second survey line direction... and Axial reference direction Angle, and simultaneously the initial direction of the second survey line. and The included angle between the axis and the reference direction is equal to the first included angle. .

[0099] In this embodiment, the extension direction of the vacuum pipe connecting the first atomic interferometry unit A1 and the third atomic interferometry unit A3 is taken as the first measurement line direction, and the extension direction of the vacuum pipe connecting the second atomic interferometry unit A2 and the fourth atomic interferometry unit A4 is taken as the second measurement line direction; the initial first measurement line direction... and The axis reference direction coincides (i.e., the first included angle) ), at this time the initial second survey line direction and Axial reference direction Angle, and simultaneously the initial direction of the second survey line. and The axis reference directions coincide.

[0100] Step 3: For each pair of atomic interferometry units (two atomic interferometry units connected by the same vacuum pipe belong to a pair of atomic interferometry units): Each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry, and fluorescence detection multiple times in a loop. Then, based on the detected atomic interference fringes, a unidirectional collinear gravity gradient calculation process is performed to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction. Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first measurement line direction is recorded as the initial first positive collinear gravity gradient measurement value. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the initial second positive collinear gravity gradient measurement value. ;

[0101] Step 4: Rotate the rotating platform P by 180 degrees, and perform the following operations again for each pair of atomic interferometry units: Each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry, and fluorescence detection multiple times in a loop. Then, based on the detected atomic interference fringes, perform a unidirectional collinear gravity gradient calculation process to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction. The unidirectional collinear gravity gradient measurement value corresponding to the first measurement line direction is denoted as the initial first reverse collinear gravity gradient measurement value. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the initial second reverse collinear gravity gradient measurement value. .

[0102] The average collinear gravity gradient measurement is calculated using the following formula:

[0103] ,

[0104] ,

[0105] in, The initial first average collinear gravity gradient measurement value; This is the initial second average collinear gravity gradient measurement.

[0106] Step 5: Change the angle of the rotating platform P so that the direction of the first measuring line is aligned with... The included angle of the axial reference direction becomes the second included angle. The corresponding first survey line direction is denoted as the first survey line direction after rotation. The corresponding direction of the second survey line is denoted as the direction of the second survey line after rotation. At this point, the direction of the second measuring line after rotation... and Axial reference direction Angle, and simultaneously with The included angle of the axial reference direction is equal to the second included angle. .

[0107] In this embodiment, the angle of the rotating platform P is changed, so that the direction of the first measuring line is changed after rotation. and The included angle of the axis reference direction is ,like Figure 2 As shown, the direction of the second measuring line after rotation is... and The included angle of the axis reference direction is also .

[0108] Step 6: For each pair of atomic interferometry units: Each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry, and fluorescence detection multiple times in a loop. Then, based on the detected atomic interference fringes, a unidirectional collinear gravity gradient calculation process is performed to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction. The unidirectional collinear gravity gradient measurement value corresponding to the first measurement line direction is denoted as the first positive collinear gravity gradient measurement value after rotation. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the second positive collinear gravity gradient measurement value after rotation. .

[0109] Step 7: Based on Step 6, rotate the rotating platform P by 180 degrees. For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry, and fluorescence detection multiple times in a loop. Then, based on the detected atomic interference fringes, a unidirectional collinear gravity gradient calculation process is performed to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction. The unidirectional collinear gravity gradient measurement value corresponding to the first measurement line direction is denoted as the first reverse collinear gravity gradient measurement value after rotation. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the second reverse collinear gravity gradient measurement value after rotation. ;

[0110] The corresponding average collinear gravity gradient measurement value is calculated using the following formula:

[0111] ,

[0112] ,

[0113] in, This is the measured value of the first average collinear gravity gradient after rotation; This is the measured value of the second average collinear gravity gradient after rotation.

[0114] Step 8, known measured values , , , and the diagonal component of the gravity gradient , and the off-diagonal component of the gravity gradient (Diagonal component of gravity gradient) , and the off-diagonal component of the gravity gradient The projection relationship between the measured values ​​(all belonging to the horizontal components of the gravity gradient) will be used to determine the measured values. , , , Substituting into the following formula, the diagonal component of the gravitational gradient can be calculated. , and the off-diagonal component of the gravity gradient :

[0115] ,

[0116] ,

[0117] ,

[0118] ,

[0119] Since the number of equations exceeds the number of unknowns, least squares fitting is used to solve the overdetermined system of equations, achieving a solution for the diagonal components of the gravity gradient. , and the off-diagonal component of the gravity gradient The optimal estimate. Then, combining this with the relationship between the three diagonal components of the gravity gradient: The diagonal components of the gravitational gradient are obtained. .

[0120] In this embodiment, at the first included angle The second included angle In special cases, the above projection relationship can be simplified to:

[0121] ,

[0122] ,

[0123] ,

[0124] ,

[0125] in, The first included angle The initial first average collinear gravity gradient measurement value at time , The first included angle The initial second average collinear gravity gradient measurement at time , The second included angle The measured value of the first average collinear gravitational gradient after rotation. The second included angle The second average collinear gravity gradient measurement value after rotation.

[0126] Based on the relationship between the three diagonal components of the gravitational gradient: The above equation can be further written as:

[0127] ,

[0128] ,

[0129] ,

[0130] ,

[0131] Solving the above equations, we can obtain:

[0132] ,

[0133] ,

[0134] ,

[0135] ,

[0136] To reduce measurement errors, we can combine the results of the two measurements to provide a more accurate diagonal component of the gravity gradient. ,Right now:

[0137] ,

[0138] Thus, by rotating the instrument's orientation in the horizontal plane, we achieved the diagonal component of the gravitational gradient. , Direct measurement, and the diagonal component of the gravitational gradient and the off-diagonal component of the gravity gradient ( Indirect measurement (belonging to the horizontal component).

[0139] The process of performing cold atom preparation, cold atom interferometry, and unidirectional collinear gravity gradient calculation includes the following steps:

[0140] (1) Perform cold atomization:

[0141] For each atomic interferometry unit: cold atom preparation is performed in the corresponding cold atom preparation cavity 101 using the corresponding up-cooled laser emitter 401, down-cooled laser emitter 402, four horizontally cooled laser emitters 403 and anti-Helmholtz coil pair 2.

[0142] This embodiment utilizes an upward-cooled laser emitter 401, a downward-cooled laser emitter 402, and four horizontally cooled laser emitters 403 to emit cooling laser beams directed towards the center of the cold atom preparation cavity 101. The six laser beams are fired in pairs, with the laser frequency detuned to the atomic resonance frequency at twice the natural linewidth. Simultaneously, current is switched on the anti-Helmholtz coil pair 2, generating a quadrupole magnetic field with zero central strength. Under the combined action of the laser and the quadrupole magnetic field, the atoms are cooled and trapped at the center of the cold atom preparation cavity 101.

[0143] (2) Performing cold atom interference:

[0144] For each atomic interferometry unit, cold atoms are thrown upward into the corresponding interferometer cavity 102. Two corresponding Raman laser emitters 5 emit corresponding Raman laser pulses, causing the cold atoms to be split, reflected, and combined in sequence to achieve interference. The atoms after interference fall back to the bottom of the interferometer cavity 102 and obtain the corresponding interference fringes through the photodetector 6.

[0145] In this embodiment, after the cold atom preparation is completed, the quadrupole magnetic field is turned off, and the frequency of the laser emitted by the upward-cooled laser emitter 401 is changed upward and the frequency of the laser emitted by the downward-cooled laser emitter 402 is changed downward, so that the difference between the frequency of the laser emitted by the upward-cooled laser emitter 401 and the frequency of the laser emitted by the downward-cooled laser emitter 402 is . This allows the atoms to acquire initial velocity. Therefore, it is thrown upwards. The wavelengths of the laser emitted by the uplink cooled laser emitter 401 and the downlink cooled laser emitter 402 are specified. It represents multiplication.

[0146] The atom flies upward into the interference cavity 102, where three Raman laser pulses are emitted sequentially by two Raman laser emitters 5. The upper Raman laser emitter 5 is installed at the vertex (height) of the atom's parabola: when the atom rises to the height of the lower Raman laser emitter 5, the lower Raman laser emitter 5 emits the first Raman laser pulse to split the atom; when the atom rises to the vertex, the upper Raman laser emitter 5 emits the second Raman laser pulse to reflect the atom; when the atom descends to the height of the lower Raman laser emitter 5, the lower Raman laser emitter 5 emits the third Raman laser pulse to combine the atom and achieve interference.

[0147] (3) Calculation of unidirectional collinear gravity gradient:

[0148] Step A1: Obtain the number of atoms in the ground state energy level after interference by obtaining the interference signal of each atom in the atomic interference fringes detected by photodetector 6.

[0149] Step A2: The relationship between the layout numbers of two diagonally related atomic interferometry units (i.e., a pair of atomic interferometry units connected by the same vacuum pipe) can be described by the equation of an ellipse:

[0150] ,

[0151] in, , , , , , For the fitting parameters, , These represent the number of layouts corresponding to each atomic interferometry unit in a pair of atomic interferometry units (i.e., connected in the same vacuum pipe).

[0152] A series of layout pairs measured by centering a pair of atomic interferometry units ( , Substituting the values ​​into the ellipse equation, we obtain the fitting parameters. , , , , , ;

[0153] Step A3: Calculate the phase difference between two atomic interferometry units connected to the same vacuum pipe (i.e., the two atomic interferometry units in a pair of atomic interferometry units). .

[0154] Step A4: Phase difference Substituting into the following formula, we obtain the unidirectional collinear gravity gradient measurement values ​​for the corresponding survey line direction:

[0155] ,

[0156] In the above formula, This is a measurement of the unidirectional collinear gravity gradient. The effective wave vector of the Raman laser. The distance between two atomic interferometry units connected in the same vacuum pipe. The time interval between two adjacent Raman laser pulses in the three Raman laser pulses.

[0157] For step 3: The first survey line direction is the initial first survey line direction. The corresponding phase difference via the initial first survey line direction The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometry units are obtained, along with the corresponding unidirectional collinear gravity gradient measurements. , denoted as the initial first positive collinear gravity gradient measurement value The direction of the second survey line is the same as the initial direction of the first survey line. The corresponding phase difference via the initial second survey line direction The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometry units are obtained, along with the corresponding unidirectional collinear gravity gradient measurements. , denoted as the initial second positive collinear gravity gradient measurement value .

[0158] For step 4: The direction of the first survey line is the initial direction of the first survey line. The opposite direction, the corresponding phase difference via the initial first survey line direction The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometer measurement units in the opposite direction are obtained, and the corresponding unidirectional collinear gravity gradient measurement values ​​are obtained. , denoted as the initial first anti-collinear gravity gradient measurement value The direction of the second survey line is the same as the direction of the initial first survey line. The opposite direction, the corresponding phase difference via the initial second survey line direction The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometer measurement units in the opposite direction are obtained, and the corresponding unidirectional collinear gravity gradient measurements are obtained. , denoted as the initial second anti-collinear gravity gradient measurement value .

[0159] For step 6: The direction of the first survey line is the direction of the first survey line after rotation. The corresponding phase difference The first measuring line direction after rotation The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometry units are obtained, along with the corresponding unidirectional collinear gravity gradient measurements. , denoted as the measured value of the first positive collinear gravity gradient after rotation. The direction of the second survey line is the direction of the second survey line after rotation. The corresponding phase difference The direction of the second measuring line after rotation The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometry units are obtained, along with the corresponding unidirectional collinear gravity gradient measurements. , denoted as the measured value of the second positive collinear gravity gradient after rotation. .

[0160] For step 7: The direction of the first survey line is the direction of the first survey line after rotation. The opposite direction, the corresponding phase difference The first measuring line direction after rotation The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometer measurement units in the opposite direction are obtained, and the corresponding unidirectional collinear gravity gradient measurement values ​​are obtained. , denoted as the measured value of the first reverse collinear gravity gradient after rotation. The direction of the second survey line is the direction of the second survey line after rotation. The opposite direction, the corresponding phase difference The direction of the second measuring line after rotation The atomic interference fringes detected by photodetector 6 in a pair of atomic interferometer measurement units in the opposite direction are obtained, and the corresponding unidirectional collinear gravity gradient measurement values ​​are obtained. , denoted as the measured value of the second reverse collinear gravity gradient after rotation. .

[0161] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A multi-component atomic gravity gradient measurement device based on a rotating platform, characterized in that, It includes a rotating platform (P), with four atomic interferometry units evenly spaced along the circumference of the platform surface; Each atomic interferometry unit has a vacuum cavity (1) including a cold atom preparation cavity (101) and an interferometer cavity (102) that are interconnected. The cold atom preparation cavity (101) is located below the interferometer cavity (102). An upward cooling laser emitter (401) is installed below the cold atom preparation cavity (101), and a downward cooling laser emitter (402) is installed above the interferometer cavity (102). Four horizontal cooling laser emitters (403) are on the same horizontal plane as the center of the cold atom preparation cavity (101). The atomic interferometric measurement units symmetrically distributed on both sides of the center of the rotating platform (P) are classified into a pair of atomic interferometric measurement units. The interference cavities (102) of each pair of atomic interferometric measurement units are connected through corresponding vacuum pipes. The two vacuum pipes intersect to form a vacuum interconnection pipe (C), and the vacuum is interconnected at the intersection. Two Raman laser emitters (5) are arranged vertically on the outer side of the middle part of each interference cavity (102). The Raman laser emitters (5) and the corresponding interference cavity (102) are symmetrically distributed about the central axis of the interference cavity (102) at the connection point with the vacuum pipe. The photodetector (6) is located on the lower outer side of the interference cavity (102). The two coils in the anti-Helmholtz coil pair (2) are symmetrically distributed on the upper and lower parts of the cold atom preparation cavity (101), and the center line connecting the two coils in the anti-Helmholtz coil pair (2) is collinear with the central axis of the cold atom preparation cavity (101); the two coils in the bias magnetic field coil pair (3) are symmetrically distributed on both sides of the vacuum cavity (1), and the direction of the center line connecting the two coils in the bias magnetic field coil pair (3) is parallel to the extension direction of the vacuum pipe connected to the corresponding interference cavity (102).

2. The multi-component atomic gravity gradient measuring device based on a rotating platform according to claim 1, characterized in that, Each of the atomic interferometry units is externally fitted with a corresponding magnetic shield (7).

3. The multi-component atomic gravity gradient measuring device based on a rotating platform according to claim 1, characterized in that, Raman lasers emitted from the two Raman laser emitters (5) outside each of the interference cavities (102) enter from one end of the corresponding vacuum pipe and enter another interference cavity (102) connected to the vacuum pipe through the other end of the corresponding vacuum pipe.

4. The multi-component atomic gravity gradient measuring device based on a rotating platform according to claim 1, characterized in that, The vacuum interconnected pipe (C) is made of titanium alloy.

5. The multi-component atomic gravity gradient measuring device based on a rotating platform according to claim 1, characterized in that, The inner wall of the vacuum interconnected pipe (C) is polished.

6. The multi-component atomic gravity gradient measuring device based on a rotating platform according to claim 2, characterized in that, The magnetic shield (7) is made of permalloy.

7. A method for measuring multi-component atomic gravity gradients based on a rotating platform, utilizing the multi-component atomic gravity gradient measuring device based on a rotating platform as described in claim 1, characterized in that... Includes the following steps: Step 1: Determine the geographical direction as east. The reference direction of the axis is north. The axis reference direction is perpendicular to the ground direction. Axial reference direction; Construct a multi-component atomic gravity gradient measurement device based on a rotating platform so that the platform surface of the rotating platform (P) is aligned with the reference direction. The axis reference direction is perpendicular; Step 2: Using the extension direction of one vacuum pipe as the first measurement line direction and the extension direction of the other vacuum pipe as the second measurement line direction; rotate the rotating platform (P) so that the first measurement line direction aligns with... The axis forms an angle with the reference direction, denoted as the first angle. The corresponding first survey line direction is denoted as the initial first survey line direction. The direction of the second survey line is denoted as the initial second survey line direction. ; Step 3: For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times in a loop, and then performs a unidirectional collinear gravity gradient calculation process based on the detected atomic interference fringes to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction; Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the initial first positive collinear gravity gradient measurement value. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the initial second positive collinear gravity gradient measurement value. ; Step 4: Rotate the rotating platform (P) by 180 degrees. For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times in a loop. Then, based on the detected atomic interferometry fringes, perform a unidirectional collinear gravity gradient calculation process to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction. Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the initial first reverse collinear gravity gradient measurement value. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the initial second reverse collinear gravity gradient measurement value. ; The average collinear gravity gradient measurement is calculated using the following formula: ， ， in, The initial first average collinear gravity gradient measurement value; This is the initial second average collinear gravity gradient measurement value; Step 5: Change the angle of the rotating platform (P) so that the direction of the first measuring line is aligned with... The included angle of the axial reference direction becomes the second included angle. The corresponding first survey line direction is denoted as the first survey line direction after rotation. The corresponding direction of the second survey line is denoted as the direction of the second survey line after rotation. ; Step 6: For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times in a loop, and then performs a unidirectional collinear gravity gradient calculation process based on the detected atomic interference fringes to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction; Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the first positive collinear gravity gradient measurement value after rotation. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the second positive collinear gravity gradient measurement value after rotation. ; Step 7: Rotate the rotating platform (P) by 180 degrees. For each pair of atomic interferometry units: each atomic interferometry unit simultaneously performs cold atom preparation, cold atom interferometry and fluorescence detection multiple times. Then, based on the detected atomic interference fringes, perform a unidirectional collinear gravity gradient calculation process to obtain the unidirectional collinear gravity gradient measurement value in the corresponding measurement line direction. Among them, the unidirectional collinear gravity gradient measurement value corresponding to the first survey line direction is denoted as the first reverse collinear gravity gradient measurement value after rotation. The unidirectional collinear gravity gradient measurement value corresponding to the second survey line direction is denoted as the second reverse collinear gravity gradient measurement value after rotation. ; The corresponding average collinear gravity gradient measurement value is calculated using the following formula: ， ， in, This is the measured value of the first average collinear gravitational gradient after rotation; This is the measured value of the second average collinear gravity gradient after rotation; Step 8: Measure the value , , , Substitute into the following formula to solve for the diagonal components of the gravitational gradient. , and the off-diagonal component of the gravity gradient : ， ， ， 。 8. The multi-component atomic gravity gradient measurement method based on a rotating platform according to claim 7, characterized in that, The unidirectional collinear gravity gradient calculation process specifically includes the following steps: The number of atoms in the ground state energy level after interference is obtained by the interference signal of each atom in the atomic interference fringes detected by the photodetector (6); A series of layout pairs measured by centering a pair of atomic interferometry units ( , Substitute the following equations for fitting: ， in, , , , , , For fitting parameters, , These represent the layout number of each atomic interferometry unit in a pair of atomic interferometry units; Calculate the phase difference between two atomic interferometer units in an atomic interferometer unit pair. ; Phase difference Substituting into the following formula, we obtain the unidirectional collinear gravity gradient measurement values ​​for the corresponding survey line direction: ， In the above formula, This is a measurement of the unidirectional collinear gravity gradient. The effective wave vector of the Raman laser. The distance between two atomic interferometry units connected in the same vacuum pipe. The time interval between two adjacent Raman laser pulses in the three Raman laser pulses.

9. The multi-component atomic gravity gradient measurement method based on a rotating platform according to claim 7, characterized in that, It also includes the following steps: converting the diagonal components of the gravity gradient obtained in step 8... , Substitution The diagonal components of the gravitational gradient are obtained. .

10. The multi-component atomic gravity gradient measurement method based on a rotating platform according to claim 9, characterized in that, When the first included angle The second included angle , ， ， ， in, The first included angle The initial first average collinear gravity gradient measurement value at time , The first included angle The initial second average collinear gravity gradient measurement at time , The second included angle The measured value of the first average collinear gravitational gradient after rotation. The second included angle The measured value of the second average collinear gravity gradient after rotation; diagonal components of gravity gradient Or the diagonal component of the gravity gradient .

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