Atomic-interferometer-based gravity and gravity gradient integrated measuring device and method
By designing an integrated gravity and gravity gradient measurement device based on atomic interferometry, and utilizing components such as a Raman laser emitter and a rotating platform, the repeatability problem caused by Coriolis error was solved, thereby improving the accuracy and repeatability of field measurements.
Patent Information
- Application Number
- CN202610732264.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-26
- Publication Date
- 2026-08-25
AI Technical Summary
In existing atomic interferometric gravity gradient motion measurements, the measurement repeatability problem caused by Coriolis error has not been effectively solved, affecting the accuracy of field measurements.
Design an integrated gravity and gravity gradient measurement device based on atomic interferometry. Utilize a Raman laser emitter, a vacuum connection pipe, a gyroscope north finder, and a rotating platform. Reduce the uncertainty of the Coriolis error through sine fitting and formula correction.
It significantly improves the repeatability and accuracy of field gravity gradient measurements, reduces Coriolis error caused by orientation uncertainty, and is suitable for mobile field surveys.
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Figure CN122632349A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of inertial measurement technology based on atomic interferometry, specifically to an integrated measurement device for gravity and gravity gradient based on atomic interferometry, and also to an integrated measurement method for gravity and gravity gradient based on atomic interferometry, which is suitable for precise surveying of gravity fields. Background Technology
[0002] High-precision gravity and gravity gradient measurement technologies hold significant application potential in resource exploration, autonomous navigation, and geophysical research. Gravity signals attenuate more slowly with increasing detection distance, making them easier to detect; while gravity gradient signals are more sensitive to the boundaries of anomalous masses, enabling the acquisition of images with higher spatial resolution. Simultaneous measurement and joint calculation of gravity and gravity gradients can not only achieve complementary advantages in detection distance and spatial resolution but also help solve the problem of multiple solutions in the inversion process. Gravity and gravity gradient measurement technologies based on cold atom interferometry offer advantages such as high precision, low drift, self-calibration, no mechanical wear, and the ability for long-term continuous observation, making them a promising next-generation measurement technology.
[0003] Since Stanford University in the United States developed the world's first atomic interferometer and applied it to gravity measurements in 1991, significant progress has been made in gravimeters and gravity gradiometers based on atomic interferometry schemes internationally. Currently, atomic interferometric gravimeters are relatively mature, having achieved large-scale external flow measurements and dynamic measurements on mobile carriers such as aircraft and ships. Atomic interferometric gravity gradiometers lag behind in maturity, currently only achieving small-scale external flow measurements and exhibiting measurement repeatability issues in the external field. In a 2022 research paper from the University of Birmingham (Nature, Vol. 602, p. 590), the Coriolis error, caused by the coupling of atomic residual horizontal velocity and Earth's rotation, was listed as one of the two most significant factors affecting measurement repeatability in external field measurements using atomic interferometric gravity gradiometers. The main reason is that under static laboratory conditions, the orientation of the measuring device remains constant, thus the Coriolis error remains constant, allowing the measuring device to achieve very high measurement resolution. Under field survey conditions, the measuring device needs to constantly change the measurement points. Each time it moves to a new point, the orientation of the measuring device may change. Therefore, the Coriolis error at each measurement point, and even multiple measurements at the same point, will be different, which seriously affects the measurement accuracy. Although Coriolis error also exists in gravity measurement, this error is smaller relative to the gravity characteristic signal, but larger relative to the gravity gradient characteristic signal, often reaching or even exceeding the magnitude of the gravity gradient characteristic signal. Therefore, this error and its stability are issues that must be considered in field gravity gradient measurement.
[0004] Integrated atomic interferometric gravity and gravity gradient measurement devices represent a new research direction. The Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences (Phys. Rev. A, Vol. 95, p. 053612) and iXblue (France) have both reported laboratory-scale integrated atomic interferometric gravity and gravity gradient measurement instruments (Phys. Rev. A, Vol. 105, p. 022801). However, no demonstration of integrated gravity and gravity gradient measurements in an outdoor field has yet been achieved. It is certain, however, that the repeatability problem of gravity gradient measurements in the outdoor field caused by Coriolis error remains a bottleneck issue that needs to be addressed. Summary of the Invention
[0005] To address the measurement repeatability problem caused by Coriolis error in existing atomic interferometric gravity gradient motion measurements, this invention proposes an integrated measurement device and method based on atomic interferometric gravity and gravity gradient. This method can significantly reduce the uncertainty of Coriolis error caused by orientation uncertainty, thereby significantly improving the field survey performance of the measurement device.
[0006] To achieve the above objectives, the present invention employs the following technical means: The integrated gravity and gravity gradient measurement device based on atomic interferometry includes a Raman laser emitter. Below the Raman laser emitter are an upper atomic interferometer and a lower atomic interferometer, vertically distributed and connected by a vacuum connection pipe. Below the lower atomic interferometer is a Raman laser reflector, the bottom of which is fixed to the top of a seismometer via a connector. The central axis of the vacuum connection pipe, the Raman laser emitted by the Raman laser emitter, and the central axis of the Raman laser reflector are configured to coincide. The device also includes a structural frame, a gyro north-finding instrument, and a rotating platform. The structural frame is mounted on the rotating platform. The Raman laser emitter, the gyro north-finding instrument, the upper atomic interferometer, the lower atomic interferometer, the Raman laser reflector, the connector, and the seismometer are all mounted on the structural frame and rotate together with the rotating platform. The central axis of the Raman laser reflector is parallel to the rotation axis of the rotating platform.
[0007] The vacuum connection pipe is clamped and fixed to the top plate of the structural frame. The upper atomic interferometer is located outside the structural frame, and the lower atomic interferometer is located inside the structural frame.
[0008] The base plate of the structural frame is set on the rotating platform, and the bottom of the gyro north finder and the seismometer are fixedly set on the base plate of the structural frame.
[0009] The bottom of the structural frame is set on a rotating platform, and an elevated base plate is set at the bottom of the structural frame. There is an elevated space between the elevated base plate and the rotating platform. The adapter is fixedly set on the top surface of the elevated base plate, the seismometer is fixedly set on the bottom surface of the elevated base plate, and the bottom of the adapter is fixedly connected to the top of the seismometer through the elevated base plate. The gyroscope north finder is fixedly set on the bottom or top surface of the elevated base plate.
[0010] Both the upper and lower atomic interferometers include a vacuum cavity, a cooled laser emitter, an anti-Helmholtz coil pair, a bias magnetic field spiral coil, a photodetector, and a magnetic shield. The vacuum cavity contains a cold atom preparation cavity and an interference cavity. The top of the cold atom preparation cavity is connected to the bottom of the interference cavity, forming an upward channel for cold atoms. The laser beam emitted by the cooled laser emitter points to the center of the cold atom preparation cavity. The anti-Helmholtz coil pair is symmetrically distributed on both sides of the center of the cold atom preparation cavity. The photodetector is set on the side wall of the cold atom preparation cavity and faces the center of the cold atom preparation cavity to detect the fluorescence of cold atoms. The bias magnetic field spiral coil is arranged around the outside of the atomic fountain interference cavity, and its central axis is coaxial with the central axis of the atomic fountain interference cavity.
[0011] The cooled laser emitter includes two upward cooled laser emitters, two downward cooled laser emitters, and two horizontal cooled laser emitters. The two upward cooled laser emitters and the two downward cooled laser emitters form two pairs of obliquely opposed optical paths. Each pair of obliquely opposed optical paths includes one upward cooled laser emitter and one downward cooled laser emitter, and the two pairs of oblique optical paths are perpendicular to each other. The two horizontal cooled laser emitters are opposed horizontally, and the optical path direction of the two horizontal cooled laser emitters is perpendicular to the plane of the obliquely opposed optical paths. The laser beams emitted by the upward cooled laser emitters, the downward cooled laser emitters, and the horizontal cooled laser emitters all point to the center of the cold atom preparation cavity.
[0012] The magnetic shielding covers are respectively fitted outside the upper atomic interferometer and the lower atomic interferometer. The magnetic shielding cover fitted outside the upper atomic interferometer has a light-transmitting hole at the top and a first through hole at the bottom wall. The magnetic shielding cover fitted outside the lower atomic interferometer has a second through hole at the top and a light-transmitting hole at the bottom wall. The upper end of the vacuum connecting pipe passes through the first through hole and is sealed to the bottom of the cold atom preparation cavity of the upper atomic interferometer. The lower end of the vacuum connecting pipe passes through the second through hole and is sealed to the top of the atomic fountain interference cavity of the lower atomic interferometer.
[0013] The integrated measurement method for gravity and gravity gradient based on atomic interferometry, utilizing the aforementioned integrated measurement device for gravity and gravity gradient based on atomic interferometry, includes the following steps: Step 1: Read the orientation angle of the measuring device on the horizontal plane using a gyroscope north finder. Change the rotation angle of the rotating platform and measure the angles of different orientations. Corresponding gravity measurement value from the upper atomic interferometer Gravity measurement values from the lower atomic interferometer and gravity gradient measurements And obtain by sinusoidal fitting. curve, curves and Curve, Record Maximum gravity gradient in the curve and the minimum of the gravity gradient and the maximum value of the gravity gradient and the minimum of the gravity gradient The respective measuring devices are oriented at angles. and orientation angle And record in the orientation angle and orientation angle Measurements of the upper atomic interferometer under the given conditions and measured values and at the angle of orientation and orientation angle Measurements of the atomic interferometer under the given conditions and measured values ; Step 2: At the new measurement point, adjust the rotation angle of the rotating platform to adjust the orientation angle of the measuring device read by the gyro north finder. or After the orientation angle of the measuring device is adjusted, gravity and gravity gradient measurements are performed, and the raw gravity measurement value of the upper atomic interferometer is obtained. The original gravity measurement value of the lower atomic interferometer The original measurement of the gravity gradient ; The original gravity measurement value of the upper atomic interferometer The original gravity measurement value of the lower atomic interferometer and the original measurements of the gravity gradient The final gravity measurement value of the upper atomic interferometer is obtained by correcting the following formula. The final gravity measurement value of the lower atomic interferometer And the final measurement of the gravity gradient ; When selected When used as a measurement of orientation angle: ; ; ; When selected When used as a measurement of orientation angle: ; ; .
[0014] Compared with the prior art, the present invention has the following beneficial effects: Initial measurements using the north-finding instrument N and the rotating platform R allow for accurate evaluation of the Coriolis error values for the two gravity measurements and gravity gradient measurements under different orientations. During mobile measurements, the measuring device, via the north-finding instrument N and the rotating platform R, can maintain a constant position at the gravity gradient measurement value. Orientation Angle The derivative, i.e. With an orientation near zero, the uncertainty of the Coriolis error (i.e., the gravity phase shift and gravity gradient phase shift caused by the Coriolis effect due to the Earth's rotation) caused by the orientation angle uncertainty during the movement of the measuring device can be significantly reduced, thereby improving the repeatability of the external field gravity gradient measurement. Attached Figure Description
[0015] Figure 1 This is a schematic diagram illustrating the principle of the present invention; Figure 2 This is a schematic diagram of the first type of structure in which the Raman laser reflector M is fixedly connected to the top of the seismometer S via the adapter J. Figure 3 This is a schematic diagram of a second structure in which the Raman laser reflector M is fixedly connected to the top of the seismometer S via an adapter J. Figure 4 This is a schematic diagram of the upper or lower atomic interferometer. Figure 5 This diagram illustrates the relationship between the measured gravity gradient and the orientation angle of the measuring device. In the diagram: A1 - Upper atomic interferometer; A2 - Lower atomic interferometer; C - Vacuum connection pipe; F - Structural frame; L - Raman laser emitter; M - Raman laser reflector; J - Adapter; S - Seismograph; N - Gyroscope north finder; R - Rotating platform; 1-Vacuum cavity; 1-1-Cold atom preparation cavity; 1-2-Interference cavity; 2-Cooled laser emitter; 2-1-Upward cooled laser emitter; 2-2-Downward cooled laser emitter; 2-3-Horizontally cooled laser emitter; 3-Anti-Helmholtz coil pair; 4-Bias magnetic field spiral coil; 5-Photodetector; 6-Magnetic shield. Detailed Implementation
[0016] 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.
[0017] Example 1:
[0018] 1. Overall The integrated gravity and gravity gradient measurement device based on atomic interferometry includes an upper atomic interferometer A1, a lower atomic interferometer A2, a vacuum connection pipe C, a structural frame F, a Raman laser emitter L, a Raman laser reflector M, a converter J, a seismometer S, a gyroscope north finder N, and a rotating platform R.
[0019] The spatial positions and connections of each component are as follows: like Figure 1 As shown, the upper atomic interferometer A1 and the lower atomic interferometer A2 are distributed vertically upwards and downwards. The vacuum connecting pipe C is located between the upper atomic interferometer A1 and the lower atomic interferometer A2, and the vacuum connecting pipe C connects the vacuum chamber 1 of the upper atomic interferometer A1 and the lower atomic interferometer A2. The Raman laser emitter L is located above the upper atomic interferometer A1, and the Raman laser reflector M is located below the lower atomic interferometer A2. The bottom of the Raman laser reflector M is fixed to the top of the seismometer S through the adapter J. The central axis of the vacuum connection pipe C, the Raman laser emitted by the Raman laser emitter L, and the central axis of the Raman laser reflector M are configured to coincide with each other. This allows the Raman laser emitted by the Raman laser emitter L to pass through the vacuum cavity 1 of the upper atomic interferometer A1, the vacuum connection pipe C, and the vacuum cavity 1 of the lower atomic interferometer A2 in sequence, and then be perpendicularly incident on the Raman laser reflector M. After passing through the Raman laser reflector M, the Raman laser passes through the vacuum cavity 1 of the lower atomic interferometer A2 and the vacuum connection pipe C in sequence, and then returns to the vacuum cavity 1 of the upper atomic interferometer A1.
[0020] like Figure 2 As shown, the base plate of the structural frame F is set on the rotating platform R, and the bottom of the gyro north finder N and the seismometer S are fixedly set on the base plate of the structural frame F.
[0021] As a preferred embodiment, the vacuum connection pipe C is clamped and fixed on the top plate of the structural frame F, the upper atomic interferometer A1 is located outside the structural frame F, and the lower atomic interferometer A2 is located inside the structural frame F.
[0022] like Figure 3As shown, the bottom of the structural frame F is set on the rotating platform R. An elevated base plate is provided at the bottom of the structural frame F, and an elevated space exists between the elevated base plate and the rotating platform R. A connector J is fixedly mounted on the top surface of the elevated base plate, while a gyro-north-finding instrument N and a seismometer S are fixedly mounted on the bottom surface of the elevated base plate. The bottom of the connector J is fixedly connected to the top of the seismometer S via the elevated base plate. It should be noted that the gyro-north-finding instrument N can also be fixedly mounted on the top surface of the elevated base plate.
[0023] like Figure 4 As shown, both the upper atomic interferometer A1 and the lower atomic interferometer A2 include a vacuum cavity 1, a cooled laser emitter 2, an anti-Helmholtz coil pair 3, a bias magnetic field spiral coil 4, a photodetector 5, and a magnetic shield 6. The vacuum cavity 1, cooled laser emitter 2, anti-Helmholtz coil pair 3, bias magnetic field spiral coil 4, and photodetector 5 are located inside the magnetic shield 6. The vacuum cavity 1 contains a cold atom preparation cavity 1-1 and an interference cavity 1-2 (atomic fountain cavity). The top of the cold atom preparation cavity 1-1 is connected to the bottom of the interference cavity 1-2, forming an upward channel for cold atoms. The cooled laser emitter 2 includes two upward cooled laser emitters 2-1, two downward cooled laser emitters 2-2, and two horizontal cooled laser emitters 2-3 (one horizontal cooled laser emitter 2-3 on the back is not shown due to obstruction).
[0024] The spatial positions and connections of the components inside the atomic interferometer are as follows: Two upward-cooled laser emitters 2-1 and two downward-cooled laser emitters 2-2 constitute two pairs of obliquely opposed optical paths. Each pair of obliquely opposed optical paths includes one upward-cooled laser emitter 2-1 and one downward-cooled laser emitter 2-2, and the two pairs of oblique optical paths are perpendicular to each other. Two horizontally cooled laser emitters 2-3 are opposed in a horizontal direction, and the optical path direction of the two horizontally cooled laser emitters 2-3 is perpendicular to the plane of the obliquely opposed optical paths. The laser beams emitted by the upward-cooled laser emitters 2-1, the downward-cooled laser emitters 2-2, and the horizontally cooled laser emitters 2-3 all point to the center of the cold atom preparation cavity 1-1.
[0025] Anti-Helmholtz coils 3 are symmetrically distributed on both sides of the center of the cold atom preparation cavity 1-1. Photodetector 5 is set on the side wall of the cold atom preparation cavity 1-1 and faces the center of the cold atom preparation cavity 1-1 to detect cold atom fluorescence. Bias magnetic field spiral coil 4 is arranged around the outside of the atomic fountain interference cavity 1-2 and its central axis is coaxial with the central axis of the atomic fountain interference cavity 1-2.
[0026] 2. Functional components (1) Upper atomic interferometer A1 and lower atomic interferometer A2 The upper atomic interferometer A1 and the lower atomic interferometer A2 are upward-thrown atomic interferometers. They work together to obtain information on gravitational acceleration and gravitational gradient by measuring the interference phase difference of atoms in a gravitational field.
[0027] (2) Vacuum connection pipe C The vacuum connection pipe C is made of metal. The inner wall of the vacuum connection pipe C is polished to reduce gas adsorption and scattering. The top and bottom of the vacuum connection pipe C are sealed to the bottom of the cold atom preparation cavity 1-1 of the upper atomic interferometer A1 and the top of the interference cavity 1-2 of the lower atomic interferometer A2, respectively, so that the vacuum cavity 1 of the upper atomic interferometer A1 and the lower atomic interferometer A2 are connected to form a common ultra-high vacuum environment.
[0028] (3) Structural frame F The structural frame F is made of metal and serves as the supporting skeleton for the measuring instrument, supporting the upper atomic interferometer A1, the lower atomic interferometer A2, and other components.
[0029] (4) Raman laser emitter L The Raman laser emitter L includes a laser source, an optical fiber collimator, a waveplate, and a mirror, and is used to output Raman laser. It is fixedly connected to the structural frame F by a support and is located above the upper atomic interferometer A1.
[0030] (5) Raman laser reflector M An optical element whose reflecting mirror has an optical surface flatness better than λ / 5, used to reflect the Raman laser output from the Raman laser emitter L.
[0031] (6) Adapter J The adapter J is an optical-mechanical structural component with basic two-dimensional angle adjustment function, which allows the Raman laser to be incident on the Raman laser reflector M at a 0-degree incident angle and return along the original path.
[0032] (7) Seismometer S The seismometer S is a vibration sensing component that can convert vibration velocity signals into analog voltage signals for output.
[0033] (8) Rotating platform R The rotating platform R is a mechanical component that can be manually or electrically rotated around a central axis perpendicular to the platform, and drive other components on the platform to rotate synchronously. The central axis of the Raman laser mirror M is set parallel to the rotation axis of the rotating platform R.
[0034] (9) Vacuum cavity 1 Vacuum cavity 1 is a sealed metal cavity with multiple optical windows, including an upper Raman window, a lower Raman window, a cooling window, and a detection window. The upper Raman window is located at the top of the metal cavity, allowing the Raman laser emitted by the Raman laser emitter L to enter the metal cavity. The lower Raman window is located at the bottom of the metal cavity, allowing the Raman laser emitted to exit to the Raman laser reflector M, and after being reflected by the Raman laser reflector M, to re-enter the metal cavity. The cooling window is used to cool the metal cavity containing the cooling laser emitted by the laser emitter 2 (the laser beams emitted by the upward cooling laser emitter 2-1, the downward cooling laser emitter 2-2, and the horizontal cooling laser emitter 2-3). The detection window is used by the photodetector 5 to receive fluorescence.
[0035] (10) Upward-cooled laser emitter 2-1 The upward cooling laser emitter 2-1 includes a laser source, an optical fiber collimator, a waveplate, and a mirror, and outputs a collimated cooling laser that is angled upward and points towards the center of the cold atom preparation cavity 1-1.
[0036] (11) Downward-cooled laser emitter 2-2 The down-cooled laser emitter 2-2 includes a laser source, an fiber collimator, a waveplate, and a mirror, and outputs a collimated cooling laser that is angled downwards and points towards the center of the cold atom preparation cavity 1-1.
[0037] (12) Horizontally cooled laser emitter 2-3 The horizontally cooled laser emitter 2-3 includes a laser source, an optical fiber collimator, a waveplate, and a mirror, and outputs a collimated cooled laser in a horizontal direction that points to the center of the cold atom preparation cavity 1-1.
[0038] (13) Anti-Helmholtz coil pair 3 The anti-Helmholtz coil pair 3 includes two anti-Helmholtz coils, which are symmetrically distributed on both sides of the center of the cold atom preparation cavity 1-1. The anti-Helmholtz coils are made of enameled copper wire, and the current in the two anti-Helmholtz coils is in opposite directions, which can generate a quadrupole magnetic field with zero central strength.
[0039] (14) Bias magnetic field spiral coil 4 The bias magnetic field spiral coil 4 is made of enameled copper wire and can generate a uniform bias magnetic field on the central axis of the bias magnetic field spiral coil 4.
[0040] (15) Photodetector 5 The photodetector 5 is a semiconductor phototube or photomultiplier tube, which can convert atomic fluorescence signals into current or voltage signals.
[0041] (16) Magnetic shielding cover 6 The magnetic shielding cover 6 is made of high magnetic permeability materials such as permalloy and is respectively fitted outside the upper atomic interferometer A1 and the lower atomic interferometer A2 to shield the static magnetic field of the environment. The top of the magnetic shielding cover 6 fitted outside the upper atomic interferometer A1 has a light-transmitting hole for Raman laser to enter, and the bottom wall has a first through hole for the upper end of the vacuum connection pipe C to pass through. The top of the magnetic shielding cover 6 fitted outside the lower atomic interferometer A2 has a second through hole for the lower end of the vacuum connection pipe C to pass through, and the bottom wall has a light-transmitting hole for Raman laser to pass through.
[0042] Example 2:
[0043] This embodiment is used to illustrate the method of using the integrated gravity and gravity gradient measurement device based on atomic interferometry described in Embodiment 1.
[0044] Six cooling laser beams, directed towards the center of the cold atom preparation cavity 1-1, are emitted from the upward cooling laser emitter 2-1, the downward cooling laser emitter 2-2, and the horizontal cooling laser emitter 3-3. These six beams are fired in pairs, with the laser frequency detuned to the atomic resonance frequency at twice the natural linewidth. This powers the anti-Helmholtz coil pair 3, causing it to generate a quadrupole magnetic field with zero central strength. Under the combined action of the cooling laser and the quadrupole magnetic field, the atoms are cooled and trapped at the center of the cold atom preparation cavity 1-1. Then, the quadrupole magnetic field generated by the anti-Helmholtz coil pair 3 is turned off, and the frequencies of the lasers emitted by the upward cooling laser emitter 2-1 and the downward cooling laser emitter 2-2 are increased and decreased, respectively. This allows the atom to obtain With an initial velocity, it is thrown upwards. This represents the average wavelength of the laser emitted by the upward-cooled laser emitter 2-1 and the downward-cooled laser emitter 2-2. Atoms fly upwards into the interference cavity 1-2, where three Raman laser pulses are emitted sequentially by the Raman laser emitter L. These Raman laser pulses are reflected by the Raman laser mirror M and return along their original path, forming counter-Raman laser pulses. The cold atoms undergo beam splitting, reflection, and combining operations under the influence of these three counter-Raman laser pulses, achieving interference. The interfered atoms fall back to the center of the cold atom preparation cavity 1-1, and the population of the interfered atoms in the ground state energy level is obtained through the photodetector 5.
[0045] In the upper atomic interferometer A1 or the lower atomic interferometer A2, the population of the atoms in the ground state energy level after interference. It can be written as: In the formula and These are the bias parameters and amplitude parameters of the interference signal, respectively, due to the phase shift of the vibration. This disrupts the overall phase of atomic interference, making it impossible to accurately determine the gravitational phase shift caused by gravity. However, only the total phase shift can be obtained. This invention uses a seismometer S to acquire, in real time, the vibration signal of the Raman laser mirror M during the interferometry process. And through relationships: ; The vibration phase shift was calculated. ,in The effective wave vector of the Raman laser. The time interval between three pairs of Raman laser pulses. The duration of the first Raman laser pulse. Let the phase sensitivity function of the atomic interferometer be expressed as: ; in, The Rabi oscillation frequency of the atom. The time variable is used. The vibration phase shift is calculated from... Relationships can be used From the total phase shift of atomic interference The gravitational phase shift caused by vibration is recovered in the middle. And through the formula: ; Achieving gravitational acceleration High-precision measurement.
[0046] The height difference between the upper atomic interferometer A1 and the lower atomic interferometer A2 is Because the gravitational acceleration is different at their locations, the phase shift caused by gravity in the two atomic interferometers has a fixed phase difference. Two cosine signals with a fixed phase difference, namely the population of atoms in the ground state energy level after interference in the upper atomic interferometer A1 and the lower atomic interferometer A2. The following ellipse equation applies between them: ; Fixed phase difference between two cosine signals Therefore, the fitting parameters in the ellipse equation can be obtained by fitting a series of interferometric data pairs (y1, y2). And calculate the phase difference Finally, using the formula Phase difference Converted to gravity gradient This allows for the measurement of the gravitational gradient Γ. Alternatively, the interference phases of the upper atomic interferometer A1 and the lower atomic interferometer A2 can be measured separately, and the difference can be used to obtain a fixed phase difference. However, their respective common-mode phase noise will enter In the measurement results, its common-mode noise suppression effect is significantly weaker than that of the ellipse fitting method.
[0047] The Coriolis effect caused by the Earth's rotation is one of the most significant sources of measurement uncertainty in current atomic interferometric gravity gradient shift measurements. The Coriolis effect caused by the Earth's rotation leads to a gravitational phase shift. Phase shift with gravity gradient They can be written as: ; ; in, Let be the angular velocity of Earth's rotation. The average residual horizontal velocity of the atomic cluster in a single interferometer. Let be the difference in average residual horizontal velocity between the atomic clusters in the two interferometers. The average residual horizontal velocity and its difference are typically caused by the directional deviation of the atomic cooling beam path. Although difficult to measure directly, this deviation is tied to the frame of the measuring device. This means that the gravitational phase shift and gravitational gradient phase shift caused by the Coriolis effect due to Earth's rotation will change with the orientation of the measuring device. From the above equation, given that the Earth's axis of rotation is northward, when the average residual horizontal velocity of the atomic cluster in a single interferometer... Or the average residual horizontal velocity difference of atomic groups in two interferometers Along the east-west direction, the errors caused by the Coriolis effect due to the Earth's rotation, resulting in gravitational phase shift and gravitational gradient phase shift, are at their maximum. At this point, the error value is also least sensitive to the orientation of the measuring device (the slope is zero near the extreme value). This is when the average residual horizontal velocity of the atomic cluster in a single interferometer... Or the average residual horizontal velocity difference of atomic groups in two interferometers The errors caused by the Coriolis effect due to Earth's rotation, resulting in gravitational phase shift and gravitational gradient phase shift, are zero. However, at this point, the error value is most sensitive to the orientation of the measuring device. The theoretical relationship between the direct measurement value of the measuring device and its orientation is as follows: Figure 5 As shown.
[0048] Under static laboratory conditions, the orientation of the measuring device remains constant. Therefore, the errors in gravity phase shift and gravity gradient phase shift caused by the Coriolis effect due to Earth's rotation remain constant, allowing the measuring device to achieve high measurement resolution. However, under field survey conditions, the measuring device needs to constantly change the measurement points. Each time it moves to a new point, the orientation of the measuring device may change. Consequently, the errors in gravity phase shift and gravity gradient phase shift caused by the Coriolis effect due to Earth's rotation are not the same at each measurement point, and even at the same point, resulting in significant variations in measurement accuracy. To address this issue, the measurement process under field survey conditions is divided into the following two stages: 1. Initial measurement of the measuring device: Read the orientation angle of the measuring device on the horizontal plane using the gyro north finder N. (That is, the azimuth angle on the horizontal plane), change the rotation angle R of the rotating platform and measure different orientation angles. Corresponding gravity measurement value of upper atomic interferometer A1 Gravity measurement values from the lower atomic interferometer A2 and gravity gradient measurements The measurement results were sinusoidally fitted to obtain... curve, curves and Curve, Record Maximum gravity gradient in the curve and the minimum of the gravity gradient and the maximum value of the gravity gradient and the minimum of the gravity gradient The respective measuring devices are oriented at angles. and orientation angle Theoretically, facing angle and orientation angle The difference is 180 degrees. This is recorded in the orientation angle. and orientation angle Gravity measurement values of upper atomic interferometer A1 under the conditions and gravity measurement value and at the angle of orientation and Gravity measurement values of atomic interferometer A2 under the following conditions and gravity measurement value .in Examples of curves are as follows Figure 5 As shown in the figure, at the orientation angle and orientation angle Nearby, the measured gravity gradient values are at their maximum and minimum values, respectively. Orientation Angle The derivative is zero, meaning it is least sensitive to orientation, so these two states can be chosen for measurement; simultaneously, the true value of the gravitational gradient lies in... Maximum gravity gradient in the curve and the minimum of the gravity gradient The difference between the two is equal in the middle. At different points, although the gravitational gradient... The value will change, but only for the corresponding The curve on the y-axis ( The shape and amplitude of the curve will not change regardless of the offset in the axial direction. This means that subsequent adjustments can be made by tilting the measuring device towards the angle... and orientation angle The measured values under the given conditions are directly translated to obtain the true value of the gravity gradient. curve, curve and Figure 5 The curves are similar, although at the directional angle and orientation angle Below, gravity measurement value of atomic interferometer A1 Gravity measurements from the lower atomic interferometer A2 Although not at an extreme value, the two gravity measurements at 180-degree angles apart are still symmetrical about the true value. Therefore, the true gravity measurement after eliminating the Coriolis error can also be obtained by translation.
[0049] 2. On-site measurement of the measuring device: Upon reaching a new measuring point, adjust the rotation angle of the rotating platform R, and adjust the orientation angle of the measuring device read from the gyroscope north-finding instrument N to... or .
[0050] After the orientation angle of the measuring device was adjusted, gravity and gravity gradient measurements were performed, and the original gravity measurement value of the upper atomic interferometer A1 was obtained. The original gravity measurement value of the lower atomic interferometer A2 The original measurement of the gravity gradient .
[0051] The original gravity measurement value of the upper atomic interferometer A1 The original gravity measurement value of the lower atomic interferometer A2 and the original measurements of the gravity gradient The final gravity measurement value of the upper atomic interferometer A1 is obtained by correcting the following formula. The final gravity measurement value of the lower atomic interferometer A2 And the final measurement of the gravity gradient .
[0052] When selected When used as a measurement of orientation angle: ; ; ; When selected When used as a measurement of orientation angle: ; ; ; in, and Orientation angles and orientation angle Gravity measurements and gravity values of the upper atomic interferometer A1 under the given conditions; and Orientation angles and orientation angle Gravity measurements and gravity values of atomic interferometer A2 under the specified conditions; and These are the maximum and minimum values of the gravitational gradient, respectively.
[0053] In summary, this invention discloses an integrated gravity and gravity gradient measurement device based on atomic interferometry and an integrated gravity and gravity gradient measurement method based on atomic interferometry suitable for mobile field surveys. Initialization measurements are performed using a gyro-based north finder N and a rotating platform R. This allows for accurate evaluation of the Coriolis error values of the two gravity measurements and gravity gradient measurements at different orientation angles, as well as the orientation angle where the measured values are least sensitive to orientation. During mobile measurement operations, the measurement device, through the north finder N and the rotating platform R, can always remain near the orientation (slope zero) where the gravity gradient is least sensitive to orientation. Therefore, the uncertainty of the Coriolis error caused by orientation uncertainty during the movement of the measurement device can be significantly reduced. Even if the north finder drifts, the uncertainty of the Coriolis error can still be controlled at an extremely low level.
[0054] It should be noted that the embodiments described in this invention are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains can make various modifications or additions to the described 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. An integrated gravity and gravity gradient measurement device based on atomic interferometry, comprising a Raman laser emitter (L), characterized in that, Below the Raman laser emitter (L) are two vertically arranged interferometers, an upper atomic interferometer (A1) and a lower atomic interferometer (A2), connected vertically. The upper and lower interferometers are connected via a vacuum connection pipe (C). Below the lower interferometer (A2) is a Raman laser reflector (M), whose bottom is fixed to the top of the seismometer (S) via an adapter (J). The central axis of the vacuum connection pipe (C), the Raman laser emitted by the Raman laser emitter (L), and the Raman laser reflector (M) are all connected. The central axes are configured to coincide with each other; it also includes a structural frame (F), a gyro north finder (N), and a rotating platform (R). The structural frame (F) is mounted on the rotating platform (R). The Raman laser emitter (L), the gyro north finder (N), the upper atomic interferometer (A1), the lower atomic interferometer (A2), the Raman laser mirror (M), the adapter (J), and the seismometer (S) are all mounted on the structural frame (F) and rotate together with the rotating platform (R). The central axis of the Raman laser mirror (M) is parallel to the rotation axis of the rotating platform (R).
2. The integrated gravity and gravity gradient measurement device based on atomic interferometry according to claim 1, characterized in that, The vacuum connection pipe (C) is clamped and fixed on the top plate of the structural frame (F), the upper atomic interferometer (A1) is located outside the structural frame (F), and the lower atomic interferometer (A2) is located inside the structural frame (F).
3. The integrated gravity and gravity gradient measurement device based on atomic interferometry according to claim 1, characterized in that, The base plate of the structural frame (F) is set on the rotating platform (R), and the bottom of the gyro north finder (N) and the seismometer (S) are fixedly set on the base plate of the structural frame (F).
4. The integrated gravity and gravity gradient measurement device based on atomic interferometry according to claim 1, characterized in that, The bottom of the structural frame (F) is set on the rotating platform (R). The bottom of the structural frame (F) is provided with an elevated base plate. There is an elevated space between the elevated base plate and the rotating platform (R). The adapter (J) is fixedly set on the top surface of the elevated base plate. The seismometer (S) is fixedly set on the bottom surface of the elevated base plate. The bottom of the adapter (J) is fixedly connected to the top of the seismometer (S) through the elevated base plate. The gyro north finder (N) is fixedly set on the bottom or top surface of the elevated base plate.
5. The integrated gravity and gravity gradient measurement device based on atomic interferometry according to claim 1, characterized in that, The upper atomic interferometer (A1) and the lower atomic interferometer (A2) both include a vacuum cavity (1), a cooled laser emitter (2), an anti-Helmholtz coil pair (3), a bias magnetic field spiral coil (4), a photodetector (5), and a magnetic shield (6). The vacuum cavity (1) includes a cold atom preparation cavity (1-1) and an interference cavity (1-2). The top of the cold atom preparation cavity (1-1) is connected to the bottom of the interference cavity (1-2) to form an upward channel for cold atoms. The laser beam emitted by the cooled laser emitter (2) points to the center of the cold atom preparation cavity (1-1). The anti-Helmholtz coil pair (3) is symmetrically distributed on both sides of the center of the cold atom preparation cavity (1-1). The photodetector (5) is set on the side wall of the cold atom preparation cavity (1-1) and faces the center of the cold atom preparation cavity (1-1) to detect the fluorescence of cold atoms. The bias magnetic field spiral coil (4) is arranged around the outside of the atomic fountain interference cavity (1-2) and its central axis is coaxial with the central axis of the atomic fountain interference cavity (1-2).
6. The integrated gravity and gravity gradient measurement device based on atomic interferometry according to claim 5, characterized in that, The cooled laser emitter (2) includes two upward cooled laser emitters (2-1), two downward cooled laser emitters (2-2), and two horizontal cooled laser emitters (2-3). The two upward cooled laser emitters (2-1) and the two downward cooled laser emitters (2-2) form two pairs of obliquely opposed optical paths. Each pair of obliquely opposed optical paths includes one upward cooled laser emitter (2-1) and one downward cooled laser emitter (2-2) that are opposed to each other, and the two pairs of oblique optical paths are perpendicular to each other. The two horizontal cooled laser emitters (2-3) are opposed to each other in the horizontal direction. The optical path direction of the two horizontal cooled laser emitters (2-3) is perpendicular to the plane where the obliquely opposed optical paths are located. The laser beams emitted by the upward cooled laser emitters (2-1), the downward cooled laser emitters (2-2), and the horizontal cooled laser emitters (2-3) all point to the center of the cold atom preparation cavity (1-1).
7. The integrated gravity and gravity gradient measurement device based on atomic interferometry according to claim 5, characterized in that, The magnetic shielding cover (6) is respectively fitted outside the upper atomic interferometer (A1) and the lower atomic interferometer (A2). The magnetic shielding cover (6) fitted outside the upper atomic interferometer (A1) has a light-transmitting hole at the top and a first through hole at the bottom wall. The magnetic shielding cover (6) fitted outside the lower atomic interferometer (A2) has a second through hole at the top and a light-transmitting hole at the bottom wall. The upper end of the vacuum connecting pipe (C) passes through the first through hole and is sealed to the bottom of the cold atom preparation cavity (1-1) of the upper atomic interferometer (A1). The lower end of the vacuum connecting pipe (C) passes through the second through hole and is sealed to the top of the atomic fountain interference cavity (1-2) of the lower atomic interferometer (A2).
8. A method for integrated measurement of gravity and gravity gradient based on atomic interferometry, utilizing the integrated measurement device for gravity and gravity gradient based on atomic interferometry as described in claim 1, characterized in that... Includes the following steps: Step 1: Read the orientation angle of the measuring device on the horizontal plane using the gyro north finder (N). Change the rotation angle of the rotating platform (R) and measure the angles of different orientations. Corresponding gravity measurement values from the upper atomic interferometer (A1) Gravity measurements from the lower atomic interferometer (A2) and gravity gradient measurements And obtain by sinusoidal fitting. curve, curves and Curve, Record Maximum gravity gradient in the curve and the minimum of the gravity gradient and the maximum value of the gravity gradient and the minimum of the gravity gradient The respective measuring devices are oriented at angles. and orientation angle And recorded in the orientation angle and orientation angle Measurements of the upper atomic interferometer (A1) under the given conditions and measured values and at the angle of orientation and orientation angle Measurements of the atomic interferometer (A2) under the specified conditions and measured values ; Step 2: At the new measurement point, adjust the rotation angle of the rotating platform (R) to adjust the orientation angle of the measuring device read by the gyro north finder (N) to... or After the orientation angle of the measuring device was adjusted, gravity and gravity gradient measurements were performed, and the raw gravity measurement values from the upper atomic interferometer (A1) were obtained. The original gravity measurements from the lower atomic interferometer (A2) The original measurement of the gravity gradient ; The original gravity measurement value of the upper atomic interferometer (A1) The original gravity measurements from the lower atomic interferometer (A2) and the original measurement of the gravity gradient The final gravity measurement value of the upper atomic interferometer (A1) is obtained by correcting the following formula. The final gravity measurement from the lower atomic interferometer (A2) And the final measurement of the gravity gradient ; When selected When used as a measurement of orientation angle: ； ； ； When selected When used as a measurement of orientation angle: ； ； 。