Aviation absolute gravity sensor based on cold atom interference

Abstract

The invention relates to an aviation absolute gravity sensor based on cold atom interference. An integral optical-mechanical structure is compressed by utilizing the characteristics of strong expansibility and high processing precision of a metal cavity; by utilizing the characteristic of large area of the optical window of the quartz vacuum chamber, the vacuum chamber still has sufficient optical channels and excellent optical performance under the condition that the volume and the surface area of the vacuum chamber are small enough; and a light path system and a vacuum system are modularized and separated, so that the maintenance cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement of absolute gravitational acceleration, and specifically relates to an airborne absolute gravity sensor using cold atom interferometry. Background Technology

[0002] Airborne absolute gravity acceleration measurement has broad application prospects in fields such as gravity field mapping, resource exploration, geophysical research, and homeland security.

[0003] Currently, airborne absolute gravity measurements primarily rely on strapdown gravimeters. These gravimeters are small, lightweight, and adaptable to various flight platforms, including fixed-wing aircraft, helicopters, and even UAVs. They are suitable for measurement tasks in diverse terrain conditions, including remote mountainous areas and complex environments such as swamps and lakes. Combining advanced inertial navigation systems and differential GPS, they maintain high measurement accuracy and spatial resolution in dynamic environments. While strapdown gravimeters provide efficient data acquisition in airborne gravity measurements, their limitations cannot be ignored. Of particular note is the long-term drift problem, where measurement results gradually deviate from the true values ​​over time, leading to decreased data accuracy. Frequent calibration is required to maintain accuracy. Furthermore, complex data fusion calculations are necessary, placing extremely high demands on the algorithms. These drawbacks, to some extent, limit the application of strapdown gravimeters in high-precision, long-term continuous measurement tasks.

[0004] Cold atom interferometric absolute gravimeters are a novel type of high-precision gravity sensor that has developed rapidly over the past two decades. Unlike strapdown gravimeters and traditional laser interferometric gravimeters, it utilizes atomic clouds cooled to near absolute zero as the test mass. Based on cold atom matter wave interferometry, it precisely measures the phase changes of interference fringes caused by gravity. This instrument can extremely sensitively measure changes in the gravitational field. Using cold atoms as "falling bodies" for gravity measurement has several significant advantages: First, since each atom in a cold atom cloud is almost identical, the influence of mechanical structure, material selection, and manufacturing processes on the measurement results can be ignored. Second, the measurement principle based on the intrinsic properties of atoms greatly reduces the system's sensitivity to changes in the external environment, thus ensuring higher stability and reliability. For these reasons, cold atom interferometric absolute gravimeters are not only of great significance in theoretical research but also demonstrate enormous potential in practical applications. In recent years, this advanced gravity measurement technology has attracted the interest of numerous research teams worldwide and has become a research hotspot in geophysics, geological exploration, and precision measurement. With the continuous advancement of technology, it is expected that cold atom interferometric absolute gravimeters will play an important role in more fields in the future.

[0005] Currently, the core components (ultra-high vacuum chambers) of cold atom absolute gravimeters from various research institutions both domestically and internationally are mostly made of non-magnetic stainless steel or titanium. These vacuum chambers require additional flanges to press the optical windows, resulting in numerous interfaces and a high susceptibility to vacuum leakage under complex vibration conditions and drastic changes in ambient temperature and humidity. Furthermore, their large size, heavy weight, and complex structure make them extremely reliant on high-precision machining, making integration with other systems and subsequent modifications difficult once designed. In addition, the laser optical path system connected to the ultra-high vacuum chamber is typically complex, with multiple optical fibers connecting the vacuum chamber and the laser path, relying on multiple fiber beam splitters to achieve key processes such as two-dimensional magneto-optical traps, three-dimensional magneto-optical traps, and atomic interference. The current ultra-high vacuum unit and complex optical path design of cold atom absolute gravimeters result in complex structures, large sizes, heavy weights, and high costs, while also being extremely sensitive to environmental conditions, particularly vibration.

[0006] Therefore, most cold atom absolute gravimeters are limited to operation in specific laboratory environments, making it difficult to meet the needs of mobile measurements. Although some cold atom gravimeters have achieved a certain degree of miniaturization and weight reduction: Patent CN201710128755.3 applied for by Zhejiang University of Technology discloses a mobile cold atom absolute gravity acceleration sensor, in which the vacuum unit and optical path unit are directly connected in free space. Although this design improves the compactness and stability of the device to some extent, the vacuum structure and optical path structure are not separate modular designs. Once the vacuum structure malfunctions, a large amount of disassembly and restoration work is required during maintenance, which greatly increases the cost of maintenance and renders all previous debugging work useless. Patent CN202010511642.3 applied for by Beijing Radio Metrology and Testing Institute discloses a cold atom gravimeter and detection method, in which the vacuum structure and optical path structure are not separate modular designs, increasing the complexity and cost of maintenance and potentially leading to long-term equipment downtime, affecting the progress of measurement tasks.

[0007] To enable applications in aerospace environments, innovative technologies and structural designs are urgently needed to reduce the device's size, weight, and power consumption, while significantly improving its stability and environmental adaptability, and enhancing the economy and ease of maintenance. This will not only expand the application scope of cold atom absolute gravimeters but also enable high-precision gravity measurements in more fields. Summary of the Invention

[0008] To address the aforementioned issues, this invention proposes an airborne absolute gravity sensor based on cold atom interferometry. The concept lies in utilizing the strong scalability and high processing precision of metal cavities to compress the overall optomechanical structure; leveraging the large optical window area of ​​quartz vacuum cavities to ensure sufficient optical channels and excellent optical performance even with a sufficiently small vacuum chamber volume and surface area; and modularizing and separating the optical path system and vacuum system to reduce maintenance costs.

[0009] The cold atom interferometer airborne absolute gravity sensor includes a magnetically shielded unit 70 with good magnetic permeability. Inside the magnetically shielded unit 70, there is a vacuum unit 10 composed of a titanium metal cavity 16a and a quartz cavity 16b connected vertically. The top of the titanium metal cavity 16a is provided with a Raman observation window 13a for receiving external Raman light 39, and the bottom is tightly connected to the quartz cavity 16b through an indium-sealed interface 13b. The titanium metal cavity 16a is connected to an ion pump 17, an electrode feed flange 12a, a rubidium metal release device 12b, a rubidium source tube 11, a gas extraction tube 18, and a Raman observation window 19 through several interfaces.

[0010] The quartz cavity 16b is formed by bonding two windows on the transverse sides, two windows on the longitudinal sides, and two windows on the upper and lower sides; a bias field coil 15b is wound on the frame 15a; the frame 15a is nested outside the quartz cavity 16b, and the region inside the quartz cavity 16b is defined as the interference region.

[0011] The indium-sealed interface 13b is provided with a downwardly enclosing optical support frame 40. The bottom of the optical support frame 40 is connected to the lower plate unit 20 to form a sealed chamber that accommodates the quartz cavity 16b. The lower plate unit 20 is connected to an external laser source through an optical fiber and generates a first through-beam cold light 36a, a second through-beam cold light 36b and a third through-beam cold light 37.

[0012] A Raman reflector 31 for reflecting Raman light 39 is located directly below the quartz cavity 16b, and an accelerometer 60 is connected to the bottom of the Raman reflector 31. A first mirror group 32a and a second mirror group 32b are respectively located on the horizontal sides of the upper part of the quartz cavity 16b. The first mirror group 32a reflects the first through-beam cold light 36a, and the second mirror group 32b reflects the second through-beam cold light 36b. A third mirror group 32c is located on the vertical side of the middle part of the quartz cavity 16b. The third mirror group 32c reflects the third paired cold light 37; the first paired cold light 36a, the second paired cold light 36b and the third paired cold light 37 all converge at a point in the inner cavity of the quartz cavity 16b, which is the center position of the magneto-optical trap; this point is defined as the center position of the magneto-optical trap; the optical support frame 40 is provided with a blow collimator 38a, the blow collimator 38a emits a blow light 38c, and the blow light 38c is reflected by the blow mirror 38b and then horizontally incident on the center position of the magneto-optical trap;

[0013] An integrated detection optical path system 35 is provided on one side of the quartz cavity 16b, and a detection light reflector 34, which is horizontally aligned with the integrated detection optical path system 35, is provided on the other side of the quartz cavity 16b.

[0014] A first anti-Helmholtz coil 14a and a second anti-Helmholtz coil 14b, respectively, are arranged on the transverse sides of the middle of the quartz cavity 16b; an atomic fluorescence collection system 33 is arranged below the quartz cavity 16b.

[0015] More specifically, an inclinometer 50 is mounted on the optical support frame 40.

[0016] More specifically, the lower plate unit 20 includes a first collimator 201. The initial laser emitted from the first collimator 201 passes sequentially through the fourth reflector 205f, the fifth reflector 205a, and the first half-glass slide 203a to reach the first polarization beam splitter 204a. The first polarization beam splitter 204a splits the initial laser into a first through-beam cold light 36a and a secondary laser. The first through-beam cold light 36a is reflected by the first quarter-glass slide 202a and the sixth reflector 206a to the first reflector group 32a. The secondary laser passes through the seventh reflector... 205b and the second half-glass slide 203b reach the second polarization beam splitter 204b; the second polarization beam splitter 204b splits the secondary laser beam into a second through-beam cold beam 36b and a third through-beam cold beam 37; the third through-beam cold beam 37 passes through the second quarter-glass slide 202b and the eighth mirror 205c and is directed toward the third mirror group 32c; the second through-beam cold beam 36b passes through the third quarter-glass slide 202c, the ninth mirror 205d, the tenth mirror 205e, and the eleventh mirror 206b and is directed toward the second mirror group 32b.

[0017] More specifically, the integrated detection optical path system 35 includes a second collimator 351, which emits detection light. The detection light is split into a first detection light 354 and a second detection light 355, which are parallel to each other, by a third polarization beam splitter 352 and a right-angle cone prism 353. Part of the first detection light 354 is blocked by a light-blocking strip 356 to blow away the F=2 state atomic clusters that have already been detected. The repump light is coupled into the collimator 351 via an optical fiber and generates a repump beam 357 parallel to the first detection light 354, which pumps the F=1 state atoms back to the F=2 state and is then irradiated by the detection light 355 below. The atomic population in the F=2 and F=1 states is detected by the atomic fluorescence collection system 33 and the integrated detection optical path system 35, achieving normalized detection.

[0018] More specifically, the magnetic shielding unit 70 is composed of permalloy with a thickness of 1.5 mm.

[0019] More specifically, the angle between the first pair of cold beams 36a and the second pair of cold beams 36b and the horizontal plane is 45 degrees.

[0020] More specifically, among the windows that make up the quartz cavity 16b, the windows on both sides of the longitudinal direction are coated with 0 degrees and can transmit cooling light in the horizontal direction; the windows on both sides of the transverse direction are coated with 45 degrees and can transmit cooling light at 45 degrees; the windows on the top and bottom sides are coated with 0 degrees and can transmit Raman light.

[0021] The working steps of this invention include:

[0022] 1. Cold Atom Loading: After rubidium atoms are released through the rubidium source tube 11 and the rubidium metal release device 12b, they diffuse into the quartz cavity 16b. The quartz cavity 16b is surrounded by a three-dimensional magneto-optical trap formed by the magnetic fields generated by the first through-beam cold light 36a, the second through-beam cold light 36b, the third through-beam cold light 37, the first anti-Helmholtz coil 14a, and the second anti-Helmholtz coil 14b, which cools and traps the rubidium atoms. After loading a sufficient amount of rubidium atoms, the magnetic field generated by the first anti-Helmholtz coil 14a and the second anti-Helmholtz coil 14b is turned off. Polarization gradient cooling is performed by reducing the detuning and power of the cooling light to cool the temperature of the trapped atom cluster to the micro-open level, thus completing the rapid loading of the low-temperature cold atom cluster.

[0023] 2. Quantum state preparation: A bias magnetic field of 15 is applied to define the quantization axis, which is coaxial with the direction of the Raman light. Then, state selection is performed by microwave action, combined with blowing light 38c to remove atoms on other magnetic sublevels, thus completing the purification of the quantum state.

[0024] 3. Cold atom interference: After the quantum state purification is completed, the cold atom cluster falls freely into the middle section of the quartz cavity 16b. Raman light 39 is applied in the vertical direction. By applying three Doppler-sensitive Raman pulse sequences π / 2-π-π / 2, the atomic wave packets are split, reversed and combined, and finally atomic matter wave interference is achieved.

[0025] 4. Normalized fluorescence detection

[0026] Atomic fluorescence collection system 33 is used to capture the fluorescence signal of atoms. When atoms encounter the standing wave of the first probe light 354, atoms in the F=2 energy state will release fluorescence, which is then captured by the atomic fluorescence collection system 33. After photoelectric conversion and signal amplification, the signal is transmitted to a high-speed data acquisition card. The fluorescence intensity recorded in this process can be regarded as the population P2 of the F=2 state atoms. Then, a traveling wave is generated by the light-blocking bar 356 set below to clear the atoms in the F=2 state. Atoms in the F=1 state continue to fall. After being pumped by the re-pump beam 357, the falling F=1 state atoms are re-excited to the F=2 state and detected by the second probe light 355 below. The fluorescence intensity recorded at this time represents the population P1 of the F=1 state atoms. The normalized atom number expression is P = P2 / (P2 + P1).

[0027] 5. Vibration compensation: The accelerometer 60 collects vibration signals in real time to compensate for the phase shift caused by vibration, and uses the inertial navigation system and satellite positioning system to correct the gravity anomaly caused by changes in latitude and longitude to obtain the absolute gravity value.

[0028] The beneficial effects of this invention include:

[0029] 1. The vacuum chamber combining titanium and quartz cavities is small in size and easy to expand, allowing for sufficient device interfaces and optical windows within a limited space, which greatly improves the integration and compactness of the probe.

[0030] 2. This invention achieves a modular design for the vacuum unit and optical unit, with convenient assembly. The optical path and vacuum system can be replaced and expanded according to experimental needs, greatly reducing sensor maintenance and modification costs and improving probe economics. Currently, most cold atom gravimeter sensors integrate the vacuum and optical modules, making them interdependent. Vacuum leakage means that all optical structures must be completely disassembled for repair or replacement of the vacuum structure. This patented design effectively avoids this drawback. When the vacuum module malfunctions, only the spare vacuum module needs to be replaced to restore probe functionality. Furthermore, any component within the probe can be replaced or upgraded at any time without affecting others. This is essential for dynamic testing in complex scenarios and under harsh vibration conditions, greatly preventing measurement delays or failures due to equipment damage.

[0031] 3. The sensor of the present invention has a compact structure, small size and light weight, and the optomechanical system has strong anti-interference ability. It can operate stably in complex vibration environments. When used with an accelerometer and inclinometer, it is suitable for complex working conditions and can perform dynamic high-precision absolute gravity measurement. Attached Figure Description

[0032] Figure 1 This is a structural diagram of an airborne absolute gravity sensor based on cold atom interferometry according to the present invention.

[0033] Figure 2 This is a right view of an airborne absolute gravity sensor based on cold atom interferometry according to the present invention.

[0034] Figure 3 This is a structural diagram of the internal structure of the titanium metal cavity of the present invention.

[0035] Figure 4 This is an optical path structure diagram of the lower plate unit of the present invention.

[0036] Figure 5 This is a structural diagram of the integrated detection optical path system of the present invention.

[0037] Figure 6 This is a structural diagram of the optical support frame of the present invention.

[0038] Figure 7 This is a diagram illustrating the working steps of the present invention. Detailed Implementation

[0039] The cold atom interferometry airborne absolute gravity sensor of the present invention will be further described below with reference to the accompanying drawings and examples.

[0040] The cold atom interferometer airborne absolute gravity sensor includes a well-sealed magnetic shielding unit 70. Inside the magnetic shielding unit 70 is a vacuum unit 10 composed of a titanium metal cavity 16a and a quartz cavity 16b joined vertically. The top of the titanium metal cavity 16a is provided with a Raman observation window 13a for receiving external Raman light 39, and the bottom is tightly connected to the quartz cavity 16b through an indium-sealed interface 13b. The titanium metal cavity 16a is connected to an ion pump 17, an electrode feed flange 12a, a rubidium metal release device 12b, a rubidium source tube 11, a gas extraction tube 18, and a Raman observation window 19 through several interfaces.

[0041] The quartz cavity 16b is formed by bonding together two windows on the horizontal sides, two windows on the vertical sides, and two windows on the top and bottom sides. A frame 15a is connected to the outside of the quartz cavity 16b, and a bias field coil 15b is wound around the outside of the frame 15a. The area inside the quartz cavity 16b is defined as the interference region. Among the windows that make up the quartz cavity 16b, the windows on the vertical sides are coated with 0 degrees and can transmit horizontal cooling light. The windows on the horizontal sides are coated with 45 degrees and can transmit 45 degrees cooling light. The windows on the top and bottom sides are coated with 0 degrees and can transmit Raman light.

[0042] The indium-sealed interface 13b is provided with a downwardly enclosing optical support frame 40. The bottom of the optical support frame 40 is connected to the lower plate unit 20 to form a sealed chamber that accommodates the quartz cavity 16b. The lower plate unit 20 is connected to an external laser source through an optical fiber and generates a first through-beam cold light 36a, a second through-beam cold light 36b and a third through-beam cold light 37.

[0043] A Raman reflector 31 for reflecting Raman light 39 is located directly below the quartz cavity 16b, and an accelerometer 60 is connected to the bottom of the Raman reflector 31. A first mirror group 32a and a second mirror group 32b are respectively located on the horizontal sides of the upper part of the quartz cavity 16b. The first mirror group 32a reflects the first through-beam cold light 36a, and the second mirror group 32b reflects the second through-beam cold light 36b. A third mirror group 32c is located on the vertical side of the middle part of the quartz cavity 16b, and the third mirror group 32c reflects the third through-beam cold light 37. The first through-beam cold light 36a, the second through-beam cold light 36b and the third through-beam cold light 37 all converge at a point in the inner cavity of the quartz cavity 16b.

[0044] An integrated detection optical path system 35 is provided on one side of the quartz cavity 16b, and a detection light reflector 34, which is horizontally aligned with the integrated detection optical path system 35, is provided on the other side of the quartz cavity 16b.

[0045] A first anti-Helmholtz coil 14a and a second anti-Helmholtz coil 14b, respectively, are arranged on the transverse sides of the middle of the quartz cavity 16b; an atomic fluorescence collection system 33 is arranged below the quartz cavity 16b.

[0046] More specifically, an inclinometer 50 is mounted on the optical support frame 40.

[0047] More specifically, the lower plate unit 20 includes a first collimator 201. The initial laser emitted from the first collimator 201 passes sequentially through the fourth reflector 205f, the fifth reflector 205a, and the first half-glass slide 203a to reach the first polarization beam splitter 204a. The first polarization beam splitter 204a splits the initial laser into a first through-beam cold light 36a and a secondary laser. The first through-beam cold light 36a is reflected by the first quarter-glass slide 202a and the sixth reflector 206a to the first reflector group 32a. The secondary laser passes through the seventh reflector... 205b and the second half-glass slide 203b reach the second polarization beam splitter 204b; the second polarization beam splitter 204b splits the secondary laser beam into a second through-beam cold beam 36b and a third through-beam cold beam 37; the third through-beam cold beam 37 passes through the second quarter-glass slide 202b and the eighth mirror 205c and is directed toward the third mirror group 32c; the second through-beam cold beam 36b passes through the third quarter-glass slide 202c, the ninth mirror 205d, the tenth mirror 205e, and the eleventh mirror 206b and is directed toward the second mirror group 32b.

[0048] More specifically, the integrated detection optical path system 35 includes a second collimator 351, which emits detection light. The detection light is split into a first detection light 354 and a second detection light 355, which are parallel to each other, by a third polarization beam splitter 352 and a right-angle cone prism 353. Part of the first detection light 354 is blocked by a light-blocking strip 356 to blow away the F=2 state atomic clusters that have already been detected. The repump light is coupled into the collimator 351 via an optical fiber and generates a repump beam 357 parallel to the first detection light 354, which pumps the F=1 state atoms back to the F=2 state and is then irradiated by the detection light 355 below. The atomic population in the F=2 and F=1 states is detected by the atomic fluorescence collection system 33 and the integrated detection optical path system 35, achieving normalized detection.

[0049] More specifically, the magnetic shielding unit 70 is composed of permalloy with a thickness of 1.5 mm.

[0050] More specifically, the angle between the first pair of cold beams 36a and the second pair of cold beams 36b and the horizontal plane is 45 degrees.

[0051] More specifically, the permeability of the material of the magnetic shielding unit 70 is in the range of 10. 4 -10 5 mH / m.

[0052] The working steps of this invention include:

[0053] 1. Cold Atom Loading: After rubidium atoms are released through the rubidium source tube 11 and the rubidium metal release device 12b, they diffuse into the quartz cavity 16b. The quartz cavity 16b is surrounded by a three-dimensional magneto-optical trap formed by the magnetic fields generated by the first through-beam cold light 36a, the second through-beam cold light 36b, the third through-beam cold light 37, the first anti-Helmholtz coil 14a, and the second anti-Helmholtz coil 14b, which cools and traps the rubidium atoms. After loading a sufficient amount of rubidium atoms, the magnetic field generated by the first anti-Helmholtz coil 14a and the second anti-Helmholtz coil 14b is turned off. By reducing the detuning and power of the cooling light, the temperature of the trapped atom cluster is cooled to the micro-open level, completing the rapid loading of the low-temperature cold atom cluster.

[0054] 2. Quantum state preparation: A bias magnetic field of 15 is applied to define the quantization axis, which is coaxial with the direction of the Raman light. Then, state selection is performed by microwave action, combined with blowing light 38c to remove atoms on other magnetic sublevels, thus completing the purification of the quantum state.

[0055] 3. Cold atom interference: After the quantum state purification is completed, the cold atom cluster falls freely into the middle section of the quartz cavity 16b. Raman light 39 is applied in the vertical direction. By applying three Doppler-sensitive Raman pulse sequences π / 2-π-π / 2, the atomic wave packets are split, reversed and combined, and finally atomic matter wave interference is achieved.

[0056] 4. Normalized fluorescence detection

[0057] Atomic fluorescence collection system 33 is used to capture the fluorescence signal of atoms. When atoms encounter the standing wave of the first probe light 354, atoms in the F=2 energy state will release fluorescence, which is then captured by the atomic fluorescence collection system 33. After photoelectric conversion and signal amplification, the signal is transmitted to a high-speed data acquisition card. The fluorescence intensity recorded in this process can be regarded as the population P2 of atoms in the F=2 state. Then, a traveling wave is generated by the light-blocking bar 356 set below to clear the atoms in the F=2 state. Atoms in the F=1 state continue to fall. After being pumped by the re-pump beam 357, the falling atoms in the F=1 state are re-excited to the F=2 state and detected by the second probe light 355 below. The fluorescence intensity recorded at this time represents the population P1 of atoms in the F=1 state. The normalized atom number expression is P = P2 / (P2 + P1). This normalized detection technique can effectively eliminate the influence of atom number fluctuations.

[0058] 5. Vibration Compensation: Random vibrations can cause the Raman mirror to vibrate, directly affecting the observed gravitational acceleration g. The actual measured acceleration is a = g + a. vib To reduce the impact of vibration, it is necessary to use an accelerometer 60 to collect vibration signals in real time, compensate for the phase shift caused by vibration, and use an inertial navigation system and a satellite positioning system to correct the gravity anomaly caused by changes in latitude and longitude, so as to obtain the absolute gravity value.

[0059] 6. System error elimination

[0060] Based on the measurement principle, various time-series configuration strategies can be designed to extract and identify different types of systematic errors. Furthermore, by combining dynamic models of solid tides and ocean tides, gravity fluctuations caused by tidal effects are corrected in real time. Simultaneously, by continuously monitoring atmospheric pressure data, necessary corrections are made to gravity changes caused by pressure variations. For the impact of polar motion on gravity values, precise corrections are made by updating polar coordinate information in real time. Through these technical means, the absolute gravitational acceleration value is ultimately provided.

[0061] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept. The scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments. The scope of protection of this invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. An airborne absolute gravimetric sensor based on cold atom interferometry, characterized in that: The magnetic shielding unit (70) is provided with a vacuum unit (10) composed of a titanium metal cavity (16a) and a quartz cavity (16b) spliced together; wherein the top of the titanium metal cavity (16a) is provided with a Raman light observation window (13a) for receiving external Raman light (39), and the bottom is tightly connected with the quartz cavity (16b) through an indium sealing interface (13b); the titanium metal cavity (16a) is connected with an ion pump (17), an electrode feedthrough flange (12a), a rubidium metal dispenser (12b), a rubidium source tube (11), a pumping tube (18) and a Raman light observation window (19) through several interfaces respectively; The quartz cavity (16b) is composed of two window pieces on the transverse sides, two window pieces on the longitudinal sides and two window pieces on the upper and lower sides; the quartz cavity (16b) is connected with a frame (15a) on the outside, and the frame (15a) is wound with a bias field coil (15b) on the outside; the area of the inner cavity of the quartz cavity (16b) is defined as an interference area; The indium sealing interface (13b) is provided with an optical support frame (40) which is enclosed downward, and the bottom of the optical support frame (40) is connected with a lower flat plate unit (20) to form a sealed cavity for accommodating the quartz cavity (16b); the lower flat plate unit (20) is connected with an external laser source through an optical fiber, and generates a first pair of collimated light (36a), a second pair of collimated light (36b) and a third pair of collimated light (37); A Raman light reflector (31) is arranged below the quartz cavity (16b) to reflect the Raman light (39), and the bottom of the Raman light reflector (31) is connected with an accelerometer (60); the transverse sides of the upper part of the quartz cavity (16b) are respectively provided with a first mirror group (32a) and a second mirror group (32b); wherein the first mirror group (32a) reflects the first pair of collimated light (36a), and the second mirror group (32b) reflects the second pair of collimated light (36b); a third mirror group (32c) is arranged on the longitudinal side of the middle part of the quartz cavity (16b), and the third mirror group (32c) reflects the third pair of collimated light (37); the first pair of collimated light (36a), the second pair of collimated light (36b) and the third pair of collimated light (37) all converge at a point in the inner cavity of the quartz cavity (16b), and the point is defined as the center position of the magneto-optical trap; a blowing collimator (38a) is arranged on the optical support frame (40), the blowing collimator (38a) emits blowing light (38c), and the blowing light (38c) is reflected by a blowing mirror (38b) and then horizontally enters the center position of the magneto-optical trap; An integrated detection light path system (35) is arranged on one lateral side of the quartz cavity (16b), and a detection light reflector (34) horizontally aligned with the integrated detection light path system (35) is arranged on the other lateral side of the quartz cavity (16b); The transverse sides of the middle part of the quartz cavity (16b) are respectively provided with a first anti-Helmholtz coil (14a) and a second anti-Helmholtz coil (14b); an atomic fluorescence collection system (33) is arranged below the quartz cavity (16b).

2. An airborne absolute gravimeter based on cold atom interferometry according to claim 1, characterized in that: An inclinometer (50) is mounted on the optical support frame (40).

3. An airborne absolute gravimeter based on cold atom interferometry according to claim 1, characterized in that: The lower flat plate unit (20) comprises a first collimating head (201), and the initial laser emitted by the first collimating head (201) reaches a first polarization beam splitter (204a) via a fourth mirror (205f), a fifth mirror (205a) and a first half-wave plate (203a) in sequence, and the first polarization beam splitter (204a) splits the initial laser into a first pair of cold light (36a) and secondary laser; the first pair of cold light (36a) is reflected by a first quarter-wave plate (202a) via a sixth mirror (206a) and is emitted to a first mirror group (32a); the secondary laser reaches a second polarization beam splitter (204b) via a seventh mirror (205b) and a second half-wave plate (203b); the second polarization beam splitter (204b) splits the secondary laser into a second pair of cold light (36b) and a third pair of cold light (37); the third pair of cold light (37) is emitted to a third mirror group (32c) via a second quarter-wave plate (202b) and an eighth mirror (205c); the second pair of cold light (36b) is emitted to a second mirror group (32b) via a third quarter-wave plate (202c), a ninth mirror (205d), a tenth mirror (205e) and an eleventh mirror (206b).

4. An airborne absolute gravimeter based on cold atom interferometry according to claim 1, characterized in that: The integrated detection light path system (35) comprises a second collimating head (351), and the second collimating head (351) emits detection light, and the detection light is split into parallel first detection light (354) and second detection light (355) via a third polarization beam splitter (352) and a right-angle corner cube prism (353); part of the first detection light (354) is blocked by a light blocking strip (356) to blow away the F=2 state atom groups that have been detected; the re-pumping light is coupled into the collimating head (351) via an optical fiber, and a re-pumping light beam (357) parallel to the first detection light (354) is generated, so that the F=1 state atoms are re-pumped to the F=2 state and are irradiated by the detection light (355) below.

5. An airborne absolute gravimeter based on cold atom interferometry according to claim 1, characterized in that: The magnetic shielding unit (70) is composed of a permalloy with a thickness of 1.5 mm.

6. An airborne absolute gravimeter based on cold atom interferometry according to claim 1, characterized in that: The included angle between the first pair of cold light (36a) and the second pair of cold light (36b) and the horizontal plane is 45 degrees.

7. An airborne absolute gravimeter based on cold atom interferometry according to claim 1, characterized in that: More specifically, among the window pieces constituting the quartz cavity (16b), the window pieces on the longitudinal two sides are 0-degree coated, and can pass the horizontal direction cooling light; the window pieces on the transverse two sides are 45-degree coated, and can pass the 45-degree cooling light; the window pieces on the upper and lower sides are 0-degree coated, and can pass the Raman light.

8. An airborne absolute gravimeter based on cold atom interferometry according to claim 1, characterized in that: The magnetic permeability of the material of the magnetic shielding unit (70) ranges from 10 4 -10 5 mH / m.

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