CN112764115B - Quantum absolute gravimeter and probe thereof - Google Patents

Abstract

The invention discloses a quantum absolute gravimeter and a probe thereof, wherein the probe comprises a measuring part and a support frame; the measuring part comprises an ultrahigh vacuum unit for capturing atoms and providing free falling space for the atoms, and the periphery of the ultrahigh vacuum unit is provided with a light path structure which is connected with the laser system and guides to generate a plurality of laser beams and a magnetic field unit which is matched with the light path structure to generate a three-dimensional magneto-optical trap for cooling and capturing the atoms; the top, the side wall and the bottom of the ultrahigh vacuum unit are all limited with optical windows for injecting laser beams necessary for absolute gravity measurement; the support frame is limited with upper, middle and lower support parts which are arranged at intervals, the optical path structures are distributed on the upper, middle and lower support parts, the magnetic field units are arranged on the middle support part, and through holes are formed on the upper, middle and lower support parts. The invention has the characteristics of relative lightness, compact structure and movable productization.

Description

Quantum absolute gravimeter and probe thereof

Technical Field

The invention relates to absolute gravity measuring equipment, in particular to a quantum absolute gravimeter and a probe thereof.

Background

The high-precision gravity measuring instrument can be used in the fields of oil and gas general survey, mineral resource exploration, geological survey, environmental monitoring, geophysical and the like, and has a very wide application prospect. Gravity measurement can be divided into absolute gravity measurement and relative gravity measurement, depending on the measurement mode. The absolute gravity measurement is to measure the absolute gravity value of a specific position in the earth gravity field, and the relative gravity measurement is to measure the gravity difference value of a specific two points in the earth gravity field. Absolute gravity measurements typically employ a kinetic method. Two methods were mainly used, one was to observe the movements of free-falling bodies, which was the method used by g. galileo in 1590 for the first gravity measurement in the world. The second is to observe the pendulum motion, which was proposed by netherlands physicist c. The basic principle of the currently common absolute gravimeter is to observe the movement of a free falling body, wherein the free falling body mass body is an optical prism, the wavelength of a stable helium ammonia laser beam is used as an optical ruler of a michelson interferometer, and the spatial distance is directly measured; the time standard is compared with an astronomical atomic frequency index by using a high-stability quartz oscillator. And obtaining the absolute gravity acceleration of the measuring point according to the falling distance and the falling time of the mass body.

The quantum absolute gravimeter is a novel high-precision absolute gravimeter, which uses microscopic atoms as test mass and realizes precise gravity acceleration measurement based on cold atomic substance wave interference. Cold atoms are used as a group of unique quantum substances, atomic substance wave interference similar to light wave interference can be realized by using the cold atoms, and beam splitting, deflection and beam combination of atomic wave packets are realized through laser pulses, so that atomic interference fringes are realized, and the falling path of microscopic atoms can be changed by the gravity acceleration, so that the phase of the interference fringes is changed. And extracting the phase of the atomic interference fringes to obtain the information of the gravity acceleration. The quantum absolute gravimeter generally comprises a probe system, an optical path system and an electric control system.

There are about 71% of the oceans on the earth's surface, and in order to obtain global gravity data, marine gravity measurements must be made. In desert, glacier, marsh, Chongshan mountain and original forest and other places where traffic is inconvenient and the pedestrian is difficult to reach, an aviation gravity measurement method is adopted for gravity measurement. In order to counteract the disturbance effect of a carrier, auxiliary measuring equipment must be added in dynamic gravity measurement of oceans, aviation and the like, and the auxiliary measuring equipment has strict requirements on the size and the weight of a gravity meter probe.

Chinese patent application publication No. CN106959473A provides a movable cold atom absolute gravitational acceleration sensor, which adopts a two-dimensional magneto-optical trap + three-dimensional magneto-optical trap structure, and the vacuum chamber adopts a quartz glass vacuum chamber. The rubidium atoms are pre-cooled in the two-dimensional magneto-optical trap, and the atoms are loaded by blowing light into the three-dimensional magneto-optical trap. And then, obtaining a measurement result through quantum state preparation, cold atom interference, normalized detection, vibration compensation, inclination correction and system error elimination. Although the system can be moved, the quartz glass vacuum chamber is expensive in manufacturing cost and easy to damage, and a special transportation platform needs to be designed for precise storage in the transportation process. Meanwhile, the two-dimensional magneto-optical trap and the three-dimensional magneto-optical trap have complicated structures, so that the miniaturization of a probe system is limited.

Chinese patent application publication No. CN106597561A provides a vacuum apparatus for atomic interference gravity measurement, which also adopts a two-dimensional magneto-optical trap + three-dimensional magneto-optical trap structure, and the vacuum chamber is a titanium alloy vacuum chamber. The three-dimensional magneto-optical trap component is a tetrakaidecahedron formed by cutting off eight vertex angles through a cube, and each face of the tetrakaidecahedron is provided with a hole. The tetrakaidecahedron is vertically arranged, the upper part of the tetrakaidecahedron is connected with the detection component, the lower part of the tetrakaidecahedron is connected with the optical component, and the left side of the tetrakaidecahedron is connected with the two-dimensional magneto-optical trap component. When the three-dimensional magneto-optical trap component works, atoms in the two-dimensional magneto-optical trap component are pre-cooled by four beams of laser and then pushed into the three-dimensional magneto-optical trap component to be further three-dimensionally cooled by six beams of laser; after being fully cooled, atoms are thrown upwards into the interference part, and Raman laser enters from the top end and interacts with the atoms to generate atom interference; and after the interference is finished, detecting the atoms when the atoms fall back to the detection part. Although the system can ensure the measurement accuracy, the whole system is too large, the structure of the two-dimensional magneto-optical trap and the three-dimensional magneto-optical trap causes the complexity of an auxiliary cooling light path, and more laser collimation systems are introduced. The three-dimensional magneto-optical trap component is a tetrakaidecahedron formed by cutting off eight vertex angles through a cube, and each surface of the tetrakaidecahedron is provided with a hole, so that the three-dimensional magneto-optical trap component is complex to manufacture and difficult to process. The system can only be used for laboratory measurement and has no mobility.

Chinese patent application publication No. CN108279441A provides a vacuum structure of a miniaturized atomic interferometer, which adopts a single three-dimensional magneto-optical trap structure, and the vacuum cavity is a titanium alloy vacuum cavity. The three-dimensional magneto-optical trap part is an octagonal cylindrical cavity, and each surface of the octagonal cylindrical cavity is provided with a hole; the upper hole of the top surface is used for installing a connecting component, the lower hole of the bottom surface is used for installing an interference component, the side hole of one side surface is used for installing an atomic source component, the side holes of the other seven side surfaces are internally embedded with and welded with optical windows, and threaded holes are formed in the periphery of the side holes and used for installing external optical components. The atoms prepared in the initial state fall to the interference part and interact with Raman light in the vertical direction, the atoms generate interference, and finally the atoms fall to the detection part to detect the atoms. Although the system removes a two-dimensional magneto-optical trap, the three-dimensional magneto-optical trap is optimized, and a beam of cooling light and Raman light share a laser collimation system. But the structure is still complex, and the whole cooling light path still needs 5 laser alignment systems. And the three-dimensional magneto-optical trap is in an octagonal column shape, and is difficult to process.

In addition, the vacuum chambers of the quantum absolute gravimeter probe commonly used at present are a titanium alloy vacuum chamber and a quartz glass vacuum chamber. The titanium alloy vacuum cavity has a reliable structure, is difficult to process and has a small light-passing area; the quartz glass vacuum cavity is easy to miniaturize, but is expensive, easy to damage and not easy to bake at high temperature. Most research units at home and abroad still stay at the laboratory measurement stage for the design of the quantum absolute gravimeter probe, and the whole vacuum system and the matched light path have complex structure, large volume and high cost and are not suitable for mobile measurement. On the premise of ensuring the measurement accuracy of the whole gravimeter system, how to further reduce the volume, reduce the weight and reduce the cost becomes a problem to be solved urgently in the research of the quantum absolute gravimeter.

Disclosure of Invention

Based on the above technical problems, a first object of the present invention is to provide a probe for a quantum absolute gravimeter, which is relatively light and compact, and has the characteristics of being mobile and being commercialized.

It is a second object of the present invention to provide a quantum absolute gravimeter including the probe described above.

In order to achieve the above object, according to one aspect of the present invention, there is provided a quantum absolute gravimeter probe including a measuring portion and a support frame; the measuring part is arranged on the support frame;

the measuring part comprises an ultrahigh vacuum unit for capturing atoms and providing free falling space for the atoms, and the periphery of the ultrahigh vacuum unit is provided with a light path structure which is connected with the laser system and guides to generate a plurality of laser beams and a magnetic field unit which is matched with the light path structure to generate a three-dimensional magneto-optical trap for cooling and capturing the atoms; wherein, the top, the side wall and the bottom of the ultrahigh vacuum unit are all limited with optical windows for injecting laser beams necessary for absolute gravity measurement; the ultrahigh vacuum unit comprises an integrally formed titanium alloy cavity, a vacuum pipeline communicated with the top of the titanium alloy cavity and a vacuumizing device communicated with the vacuum pipeline, wherein the titanium alloy cavity is a cuboid and is respectively configured into a three-dimensional magneto-optical well region, an interference region and a detection region from top to bottom, the upper end and the lower end of the titanium alloy cavity are open, an upper optical window and a lower optical window are limited on each side of the titanium alloy cavity, the first optical window on the upper portion of the titanium alloy cavity is opposite to the three-dimensional magneto-optical well region, the second optical window on the lower portion of the titanium alloy cavity is opposite to the detection region, the upper end opening of the titanium alloy cavity is connected with the vacuum pipeline through a connecting component, and the lower end opening of the titanium alloy cavity is configured with a third optical window.

Preferably, the support frame is limited with an upper support member, a middle support member and a lower support member which are arranged at intervals, the adjacent support members are connected through a support rod, the optical path structure is arranged on the upper support member, the middle support member and the lower support member, the magnetic field unit is arranged on the middle support member, through holes are formed in the upper support member, the middle support member and the lower support member, the through holes in the middle support member are used for embedding the ultrahigh vacuum unit, and the through holes in the upper support member are used for avoiding laser beams which are emitted from the optical structure part of the upper support member and enter the top of the ultrahigh vacuum unit.

Preferably, each first optical window and each second optical window on the adjacent side of the titanium alloy cavity are correspondingly arranged at the same height, the bottom of each first optical window is higher than the middle support component, and the top of each second optical window is lower than the middle support component.

Preferably, the length of the first optical window is not less than the width of the first optical window, and an incident laser beam of the three-dimensional magneto-optical trap is injected from the first optical window and converged in the titanium alloy cavity; one pair of opposite first optical windows is used for injecting two beams of oppositely emitted first cooling light beams into the titanium alloy cavity in a crossing manner, and meanwhile, one of the first optical windows is also used for injecting blowing laser beams; the other pair of opposite first optical windows is used for injecting a second cooling beam which is vertical to the two first cooling beams along the horizontal direction.

Preferably, the length of the second optical window is not less than the width thereof, wherein a pair of opposing second optical windows are used for injection of the detection laser beam for detecting atoms.

Preferably, a fourth optical window at the top of the ultrahigh vacuum unit is opposite to a third optical window at the bottom of the titanium alloy cavity, the fourth optical window is used for enabling the raman laser beam to enter the ultrahigh vacuum unit, and the raman laser beam is reflected by a raman light reflecting device below the third optical window and then returns to the titanium alloy cavity to form an interference laser beam.

Preferably, the support frame is limited with an upper support component, a middle support component and a lower support component which are arranged at intervals, and the optical path structure comprises a first optical path structure for realizing three beams of cooling light beams of the three-dimensional magneto-optical trap; the first light path structure comprises a first collimating device and an optical component connected with the first collimating device, wherein the optical component is used for dividing a laser beam emitted by the first collimating device into two first cooling light beams which are oppositely emitted and inclined by 45 degrees relative to the vertical direction and one second cooling light beam which is oppositely emitted and injected along the horizontal direction and vertically intersected with the two first cooling light beams;

the optical assembly comprises a plurality of optical components at least arranged on three reference planes between the upper supporting component and the middle supporting component, wherein the first reference plane is higher than the center of the three-dimensional magneto-optical trap, the second reference plane is as high as the center of the three-dimensional magneto-optical trap, and the third reference plane is lower than the center of the three-dimensional magneto-optical trap.

Preferably, the optical module includes a first light splitting device, a second light splitting device, a first reflecting member, a fourth reflecting member, a fifth reflecting member, a sixth reflecting member, an eighth reflecting member, and a ninth reflecting member; the action surfaces of the first reflection component and/or the fourth reflection component are arranged on a first reference plane, the action surfaces of the eighth reflection component and the ninth reflection component are arranged on a second reference plane, and the action surfaces of the fifth reflection component and/or the sixth reflection component are arranged on a third reference plane; the action surfaces of the first reflection component, the fourth reflection component, the fifth reflection component, the sixth reflection component, the eighth reflection component and the ninth reflection component are all right opposite to the center of the three-dimensional magneto-optical trap; the first reflecting component and the sixth reflecting component are positioned on one side of the center of the three-dimensional magneto-optical trap, and the fourth reflecting component and the fifth reflecting component are arranged on the other side of the center of the three-dimensional magneto-optical trap; phase adjusting components for changing the phase of the light beams so as to enable the opposite light beams to be mutually opposite in phase are arranged between the action surfaces of the fifth reflecting component, the sixth reflecting component and the ninth reflecting component and the center of the three-dimensional magneto-optical trap;

the first light splitting device is connected with the first collimating device and is used for splitting a laser beam emitted by the first collimating device into a first secondary light beam and a second secondary light beam, the propagation directions of the first secondary light beam and the second secondary light beam are mutually perpendicular, the first secondary light beam is directly or indirectly incident on the second light splitting device, the second secondary light beam is directly or indirectly incident on the action surface of the first reflecting component, the second secondary light beam is reflected by the first reflecting component, propagates in the downward-inclined 45-degree direction, sequentially penetrates through the center of the three-dimensional magneto-optical trap and the corresponding phase adjusting component, and then is vertically incident on the action surface of the fifth reflecting component, and the fifth reflecting component reflects the second secondary light beam back to the original path to form a first cooling light beam which is 45-degree opposite to the vertical direction;

the first secondary light beam is divided into a third secondary light beam and a fourth secondary light beam, the propagation directions of the third secondary light beam and the fourth secondary light beam are mutually vertical, the third secondary light beam is directly or indirectly incident on the action surface of the fourth reflection component, the third secondary light beam is reflected by the fourth reflection component, then propagates downwards along an oblique 45-degree direction, penetrates through the center of the three-dimensional magneto-optical trap and the corresponding phase adjustment component and then vertically enters the action surface of the sixth reflection component, and the sixth reflection component reflects the third secondary light beam back to the original path to form another first cooling light beam which is opposite to the vertical direction at an angle of 45 degrees;

the fourth secondary light beam directly or indirectly enters the action surface of the eighth reflecting component, is reflected by the eighth reflecting component, penetrates through the center of the three-dimensional magneto-optical trap and the corresponding phase adjusting component along the horizontal direction perpendicular to the two cooling light beams, and then vertically enters the action surface of the ninth reflecting component, and the ninth reflecting component reflects the fourth secondary light beam back to the original circuit so as to form a second cooling light beam which is oppositely emitted along the horizontal direction.

Preferably, the first optical path structure further includes a second reflecting member, a third reflecting member, and a seventh reflecting member;

the second reflecting component and the third reflecting component are arranged on a propagation path of the third secondary light beam and are used for changing the propagation direction of the third secondary light beam so that the third secondary light beam propagates to the opposite side of the three-dimensional magneto-optical trap while avoiding the three-dimensional magneto-optical trap;

the seventh reflecting component is arranged on the propagation path of the fourth secondary light beam and is used for directly or indirectly reflecting the fourth secondary light beam to the eighth reflecting component.

In another aspect of the invention, a quantum absolute gravimeter is provided, which specifically comprises a control system, a laser system and a probe interconnected by wires and/or optical fibers; the control system comprises a controller and a plurality of mechanical shutters connected with the controller and capable of eliminating corresponding laser beams when needed;

the laser system is used for providing a laser light source which is used for generating a plurality of laser beams used for assisting in cooling, capturing, blowing, interfering and detecting atoms; the probe is as described above.

Compared with the prior art, the invention has the beneficial effects that:

the invention improves the structure of the vacuum cavity, the light path and the like, removes redundant lines, has compact structure, ensures that the gravimeter has the characteristics of light weight, compact structure and movable productization, and has better market prospect.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the application, and the description of the exemplary embodiments of the application are intended to be illustrative of the application and are not intended to limit the application.

FIG. 1 is a schematic diagram of a quantum absolute gravimeter probe system according to an embodiment of the present invention;

FIG. 2(a) is a schematic view of the structure of FIG. 1 from the perspective A;

FIG. 2(B) is a schematic view of the structure from the perspective B in FIG. 1;

FIG. 3 is a schematic structural diagram of a support frame according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of an ultra-high vacuum unit (without a vacuum extractor) in an embodiment of the present invention;

FIG. 5 is a schematic structural view of a vacuum chamber made of a titanium alloy according to an embodiment of the present invention;

FIG. 6 is an exploded view of a portion (first optical window) of a titanium alloy vacuum chamber in an embodiment of the present invention;

FIG. 7 is a schematic structural diagram of an optical path structure in an embodiment of the present invention;

fig. 8(a) is a structural top view of a first optical path structure in the embodiment of the present invention;

fig. 8(b) is a schematic structural diagram of a first optical path structure in the embodiment of the present invention;

fig. 8(c) is a schematic view of an optical path structure of a first optical path structure in the embodiment of the present invention;

FIG. 9 is a schematic diagram of the peripheral components used to create a three-dimensional magneto-optical trap in an embodiment of the present invention.

Wherein, 1, an ultrahigh vacuum unit; 2. a support frame; 3. an optical path structure; 4. an atomic number monitoring device; 5. an inclinometer; 6. an optical power monitoring section;

11. a titanium alloy cavity; 12. a vacuum line; 13. a vacuum pumping device;

111. a first optical window; 112. a second optical window; 113. a third optical window; 114. a fourth optical window; 115. a flange; 116. a stepped hole; 117. a stepped groove;

1111. indium wire; 1112. a window sheet; 1113. a gasket; 1114. a cover plate;

21. an upper support member; 22. a middle support member; 23. a lower support member; 24. a support bar;

211. a through hole in the upper support member; 221. a through hole in the middle support member;

3101. a first light splitting device; 3102. a second light splitting device; 3103. a first reflecting member; 3104. a second reflecting member; 3105. a third reflecting member; 3106. a fourth reflecting member; 3107. a fifth reflecting member; 3108. a sixth reflecting member; 3109. a seventh reflecting member; 3110. an eighth reflecting member; 3111. a ninth reflecting member; a. a first secondary beam; b. a second secondary beam; c. a third secondary beam; d. a fourth secondary beam; 3116-; 3118. a second cooling beam; 3119. a first collimating device;

31011. a first quarter wave plate; 31012. a second half wave plate; 31013. a first quarter wave plate; 31014. a second quarter wave plate; 31015. a third quarter wave plate; 31016. a first polarization splitting prism; 31017. a second polarization beam splitter prism; 31018. a fourth quarter wave plate; 31019. a fifth quarter wave plate; 31020. a sixth quarter wave plate;

3201. a Raman light generating device; 3202. a Raman light reflecting device;

3301. a third collimating device; 3302. a blowing light reflection member;

3401. a fourth collimating means; 3402. a detection light reflection member;

71. a three-dimensional magneto-optical trap coil; in addition, the dotted line portion in the figure indicates a light beam.

Detailed Description

The invention is further described with reference to the following figures and examples.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "a plurality" means two or more unless explicitly defined otherwise.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

The embodiment provides a quantum absolute gravimeter, which comprises a control system, a laser system and a probe, wherein the control system, the laser system and the probe are connected with each other through electric wires and/or optical fibers; wherein:

the control system comprises a controller and a plurality of mechanical shutters connected with the controller and capable of eliminating corresponding laser beams when needed;

the laser system is used for providing a laser light source which is used for generating a plurality of laser beams used for assisting in cooling, capturing, blowing, interfering and detecting atoms;

as a preferred embodiment, the probe comprises a measuring part for performing absolute gravity measurement and a support frame 2 used as a carrier of the measuring part, wherein the measuring part comprises an ultrahigh vacuum unit for capturing atoms and providing free falling space for the atoms, the periphery of the ultrahigh vacuum unit is provided with an optical path structure which is connected with the laser system and guides to generate a plurality of laser beams and a magnetic field unit which is matched with the optical path structure to generate a three-dimensional magneto-optical trap for cooling and capturing the atoms, and the top, the side wall and the bottom of the ultrahigh vacuum unit are all limited with optical windows for injecting laser beams necessary for absolute gravity measurement.

As a preferred embodiment, as shown in fig. 1, fig. 2(a) - (b) and fig. 3, the supporting frame 2 defines upper, middle and lower supporting members arranged at intervals, the adjacent supporting members are connected by the supporting rod 24, through holes are formed on the upper, middle and lower supporting members, the through hole 221 on the middle supporting member 22 is used for embedding the ultra-high vacuum unit, and the through hole 211 on the upper supporting member 21 is used for avoiding the laser beam emitted from the optical structure part of the upper supporting member 21 and entering the top of the ultra-high vacuum unit 1. Preferably, the supporting frame 2 is made of an aluminum alloy material.

As a preferred embodiment, as shown in fig. 4, the ultra-high vacuum unit 1 includes an integrally formed titanium alloy cavity 11, a vacuum pipe 12 communicating with the top of the titanium alloy cavity 11, and a vacuum pumping device 13 communicating with the vacuum pipe 12.

As a preferred embodiment, as shown in fig. 5 and 6, the titanium alloy cavity 11 is a rectangular parallelepiped, and is configured with a three-dimensional magneto-optical well region, an interference region and a detection region from top to bottom, the upper end and the lower end of the titanium alloy cavity 11 are open, and each side surface of the titanium alloy cavity defines an upper optical window and a lower optical window, wherein the upper first optical window 111 faces the three-dimensional magneto-optical well region, the lower second optical window 112 faces the detection region, the upper end opening of the titanium alloy cavity 11 is connected to the vacuum pipe 12 through a connecting component, and the lower end opening of the titanium alloy cavity 11 is configured with a third optical window 113. By optimizing the structure of the ultrahigh vacuum unit and adjusting the structure of the vacuum cavity and the position and shape of an optical window of the vacuum cavity, the three-dimensional magneto-optical well region, the interference region and the detection region in the vacuum cavity can be integrally formed, so that the processing difficulty and the processing cost of the titanium alloy cavity 11 can be effectively reduced, the smoothness inside the titanium alloy cavity 11 can be ensured, the time consumed in the vacuum pumping process is reduced, the problem of low vacuum degree caused by welding seams, connecting seams and the like is avoided, and the measurement accuracy is favorably improved; more importantly, the scheme is also obviously beneficial to simplifying the structure of the probe system, so that the probe system is more portable and convenient to move.

In a preferred embodiment, each of the first optical windows 111 and each of the second optical windows 112 on the adjacent side surfaces of the titanium alloy cavity 11 are disposed at the same height, and the bottom of the first optical window 111 is higher than the middle support member, and the top of the second optical window 112 is lower than the middle support member.

As a preferred embodiment, the length of the first optical window 111 is not less than its width, and as shown in fig. 9, the incident laser beam of the three-dimensional magneto-optical trap is injected from the first optical window 111 and converged into the titanium alloy cavity 11; specifically, the method comprises the following steps: one pair of the opposite first optical windows 111 is used for injecting two oppositely emitted first cooling light beams 3116 into the titanium alloy cavity 11 in a crossing manner, and meanwhile, one of the first optical windows 111 is also used for injecting blowing laser beams; another pair of opposing first optical windows 111 is used for injection of a second cooling beam 3118 perpendicular to the two first cooling beams 3116 in the horizontal direction.

In a preferred embodiment, the second optical window 112 has a length not less than its width, wherein a pair of opposing second optical windows 112 are used for injection of a detection laser beam for detecting atoms.

In a preferred embodiment, the fourth optical window 114 at the top of the ultrahigh vacuum unit is opposite to the third optical window 113 at the bottom of the titanium alloy cavity 11, the fourth optical window 114 is used for allowing an interference laser beam to enter the ultrahigh vacuum unit, and the interference laser beam is reflected by the interference laser beam reflecting component below the third optical window 113 and then returns to the titanium alloy cavity 11.

In a preferred embodiment, the first optical window 111 and the second optical window 112 each include a window 1112, and the window 1112 is sealingly fixed to a sidewall of the titanium alloy cavity 11.

As a preferred embodiment, as shown in fig. 6, a stepped hole 116 is defined in the side wall of the titanium alloy chamber 11, the stepped hole 116 has an elongated hole shape on the inner side, and a stepped groove 117 having a shape matching the window 1112 and extending to the edge is formed on the outer side, and the window 1112 is fitted in the stepped groove 117.

As a preferred embodiment, referring to fig. 6, the sealing assembly structure between the window 1112 and the stepped hole 116 includes an indium wire 1111, a gasket 1113 and a cover plate 1114 in sequence from inside to outside, wherein the indium wire 1111, the gasket 1113 and the cover plate 1114 are all in a ring shape, the indium wire 1111 is attached to the surface of the stepped groove 117, the window 1112 is embedded in the stepped groove 117 and covers the indium wire 1111, and the gasket 1113 and the cover plate 1114 are in sequence covered outside the window 1112.

In a preferred embodiment, the cover 1114 is bonded or bolted to the sidewall of the titanium alloy cavity 11; preferably, the cover plate 1114 is bolted to the side walls of the titanium alloy cavity 11.

In a preferred embodiment, as shown in fig. 5, a flange 115 is connected or integrally formed on the top of the titanium alloy cavity 11, and the vacuum pipe 12 is connected through the flange 115.

As a preferred embodiment, the bottom of the titanium alloy cavity 11 is connected to an annular pressing plate, and the window 1112 of the third optical window 113 is embedded on the annular pressing plate or between the bottom of the titanium alloy cavity 11 and the annular pressing plate.

In a preferred embodiment, the vacuum tube 12 is connected at one end to a source of alkali metal (preferably rubidium) for providing atoms as a gravimetric mass and at the other end to an evacuation device 13, preferably the evacuation device 13 comprises an ion pump, which is disposed on the upper support member.

As shown in fig. 1, fig. 2(a) - (b) and fig. 7, the optical path structures 3 are disposed on the upper, middle and lower support members, and specifically, the optical path structures include a first optical path structure for three laser beams to realize a three-dimensional magneto-optical trap; as shown in fig. 1 and fig. 2(b), the first optical path structure includes a first collimating device 3119 and an optical assembly coupled to the first collimating device 3119, the optical assembly is configured to divide the laser beam emitted from the first collimating device 3119 into two first cooling beams 3116, 3117 which are oppositely directed and inclined by 45 ° with respect to the vertical direction and a second cooling beam 3118 which is oppositely directed and injected along the horizontal direction and perpendicularly intersects the two first cooling beams 3116, 3117;

as a preferred embodiment, as shown in fig. 2(a), 2(b) and 8(a), the optical assembly includes a plurality of optical components disposed on at least three reference planes between the upper support member 21 and the middle support member 22, wherein the first reference plane is higher than the center of the three-dimensional magneto-optical well, the second reference plane is at the same height as the center of the three-dimensional magneto-optical well, and the third reference plane is lower than the center of the three-dimensional magneto-optical well, so as to realize a three-dimensional layout of the optical components at the periphery of the ultra-high vacuum unit 1, thereby effectively reducing the volume occupied by the optical components of the three-dimensional magneto-optical well region and making the structure of the part more compact. In addition, the structure can also reduce the number of the collimating heads and other devices (in this embodiment, only one collimating head is adopted in the first optical path structure to realize the arrangement of the three-dimensional magneto-optical well region cooling optical path), thereby reducing the number of optical fibers introduced into the gravimeter probe and reducing the assembly complexity.

As a preferred embodiment, as shown in fig. 2 and 2(b), the maximum diameter of the first optical path structure is smaller than the minimum diameter of the upper support surface and/or the middle support surface. In this way, the distance from the emitting end of the two oppositely-directed first cooling beams 3116 and the emitting end of the one oppositely-directed second cooling beam 3118 to the center of the three-dimensional magneto-optical trap is limited to the inner side of the longitudinal edge of the supporting component, so that the horizontal dimension occupied by the first optical path structure forming the three-dimensional magneto-optical trap is reduced to the minimum, the external dimension and the weight of the probe system are further reduced, and the mobility of the gravimeter is further increased.

As a preferred embodiment, as shown in fig. 7, the optical module includes a first light splitting device 3101, a second light splitting device 3102, a first reflecting member 3103, a fourth reflecting member 3106, a fifth reflecting member 3107, a sixth reflecting member 3108, an eighth reflecting member 3110 and a ninth reflecting member 3111; among them, the action surface of the first reflecting member 3103 and/or the fourth reflecting member 3106 is provided on the first reference plane, the action surfaces of the eighth reflecting member 3110 and the ninth reflecting member 3111 are provided on the second reference plane, and the action surface of the fifth reflecting member 3107 and/or the sixth reflecting member 3108 is provided on the third reference plane; the active surfaces of the first reflecting member 3103, the fourth reflecting member 3106, the fifth reflecting member 3107, the sixth reflecting member 3108, the eighth reflecting member 3110 and the ninth reflecting member 3111 are all aligned with the center of the three-dimensional magneto-optical trap; the first reflecting member 3103 and the sixth reflecting member 3108 are positioned on one side of the center of the three-dimensional magneto-optical well, and the fourth reflecting member 3106 and the fifth reflecting member 3107 are positioned on the other side of the center of the three-dimensional magneto-optical well; phase adjusting members for changing the phase of the light beams and inverting the phase of the incident light beams are provided between the operating surfaces of the fifth reflecting member 3107, the sixth reflecting member 3108 and the ninth reflecting member 3111 and the center of the three-dimensional magneto-optical trap;

the first beam splitter 3101 is coupled to the first collimating device 3119 and is configured to split the laser beam emitted from the first collimating device 3119 into a first secondary beam a and a second secondary beam b, the propagation directions of which are perpendicular to each other, wherein the first secondary beam a directly or indirectly enters the second beam splitter 3102, the second secondary beam b directly or indirectly enters the acting surface of the first reflecting member 3103, the second secondary beam b is reflected by the first reflecting member 3103, propagates in a 45 ° downward oblique direction, sequentially passes through the center of the three-dimensional magneto-optical trap and the corresponding phase adjusting member, and then perpendicularly enters the acting surface of the fifth reflecting member 3107, and the fifth reflecting member 3107 reflects the second secondary beam b back to the original path to form a first cooling beam 3116, which is incident at 45 ° to the perpendicular direction;

the first secondary light beam a is divided into a third secondary light beam c and a fourth secondary light beam d by a second light splitting device 3102, the propagation directions of which are perpendicular to each other, the third secondary light beam c is directly or indirectly incident on the action surface of a fourth reflecting member 3106, the third secondary light beam c is reflected by the fourth reflecting member 3106, propagates in the 45 ° downward oblique direction, passes through the center of the three-dimensional magneto-optical trap and the corresponding phase adjusting member, and is vertically incident on the action surface of a sixth reflecting member 3108, and the sixth reflecting member 3108 reflects the third secondary light beam c back to the original path to form another first cooling light beam 3117 which is incident at 45 ° to the perpendicular direction;

the fourth order light beam d is directly or indirectly incident on the action surface of the eighth reflecting member 3110, reflected by the eighth reflecting member 3110, passes through the center of the three-dimensional magneto-optical well and the corresponding phase adjusting member in a horizontal direction perpendicular to the two cooling light beams, and then is vertically incident on the action surface of the ninth reflecting member 3111, and the ninth reflecting member 3111 reflects the fourth order light beam d back to the original path to form a second cooling light beam 3118 which is incident in the horizontal direction. The above structure enables the first reflecting member 3103 and the fourth reflecting member 3106 to be arranged closer to the center of the three-dimensional magneto-optical trap, and more specifically, the first reflecting member 3103 and the fourth reflecting member 3106 to be arranged closer to the horizontal plane of the vertical axis of the center of the three-dimensional magneto-optical trap, and the first reflecting member 3103 and the second reflecting member 3104 to be arranged closer to the vertical plane of the center of the three-dimensional magneto-optical trap, so that the plurality of optical components in the whole first optical structure can be further moved closer to the center of the three-dimensional magneto-optical trap, that is, the layout of the first optical path structure is more compact, the external dimension and the weight of the probe system are reduced, and the mobility of the gravimeter is further increased.

In a preferred embodiment, the first optical path structure further includes a second reflecting member 3104, a third reflecting member 3105 and a seventh reflecting member 3109;

the second reflecting member 3104 and the third reflecting member 3105 are disposed on the propagation path of the third secondary light beam c, and are configured to change the propagation direction of the third secondary light beam c so that the third secondary light beam c propagates to the opposite side of the three-dimensional magneto-optical trap while avoiding the three-dimensional magneto-optical trap;

the seventh reflecting member 3109 is disposed on a propagation path of the fourth order light beam d, and directly or indirectly reflects the fourth order light beam d to the eighth reflecting member 3110.

As a preferred embodiment, as shown in fig. 1, 2(a) - (b), 7, and 8(a) - (c), the action surfaces of the first light splitting device 3101, the second light splitting device 3102, the first reflecting member 3103, the second reflecting member 3104, the third reflecting member 3105, and the fourth reflecting member 3106 are all provided on a first reference plane, the action surfaces of the fifth reflecting member 3107 and the sixth reflecting member 3108 are all provided on a third reference plane, and the action surfaces of the seventh reflecting member 3109, the eighth reflecting member 3110, and the ninth reflecting member 3111 are all provided on a second reference plane; wherein:

as a preferred embodiment, as shown in fig. 8(a) -8 (c) and 9, the first light splitting device 3101 is disposed on one side of the three-dimensional magneto-optical trap and splits an incident laser beam into a first secondary light beam a propagating forward along the one side of the three-dimensional magneto-optical trap and a second secondary light beam b propagating horizontally away from the three-dimensional magneto-optical trap; the first reflecting member 3103 is adjacent to the first light splitting device 3101, and its active surface is positioned in the emission direction of the second secondary light beam b;

as a preferred embodiment, as shown in fig. 8(a) -8 (c), the second light splitting device 3102 is adjacent to the first light splitting device 3101, receives the first secondary light beam a directly or indirectly, and splits it into a downward-propagating fourth secondary light beam d and a parallel but reverse-propagating third secondary light beam c;

as a preferred embodiment, as shown in fig. 8(a) - (c), the second light splitting device 3102, the second reflecting member 3104 and the third reflecting member 3105 are sequentially arranged along the outer circumference of the three-dimensional magneto-optical trap, and the second reflecting member 3104 and the third reflecting member 3105 are both arranged on the propagation path of the third secondary light beam c, and the acting surfaces of the second reflecting member 3104 and the third reflecting member 3105 are parallel to each other, so that the third secondary light beam c is guided to continuously turn and horizontally enter the fourth reflecting member 3106 after avoiding the three-dimensional magneto-optical trap;

as a preferred embodiment, as shown in fig. 8(b) -8 (c) and 9, the seventh reflecting member 3109 is disposed below the second beam splitter 3102 and adjacent to the eighth reflecting member 3110, and reflects the fourth-order light beam d emitted downward from the second beam splitter 3102 into a light beam propagating in the horizontal direction and directly or indirectly incident on the action surface of the eighth reflecting member 3110.

As a preferred embodiment, as shown in fig. 1 and fig. 2(a) - (b), the first light splitting device 3101, the second light splitting device 3102, the first reflecting member 3103, the second reflecting member 3104, the third reflecting member 3105 and the fourth reflecting member 3106 are all mounted upside down on the bottom of the upper support member by mounting bases. Accordingly, the first reflecting member 3103, the second reflecting member 3104, the third reflecting member 3105, the fourth reflecting member 3106, the fifth reflecting member 3107, the sixth reflecting member 3108, the seventh reflecting member 3109, the eighth reflecting member 3110, the ninth reflecting member 3111, the raman light reflecting device 3202 and the probe light reflecting member 3402 each include a corresponding optical lens and a mounting seat for fixing the optical lens, as shown in fig. 8(c), the phase adjusting member between the fifth reflecting member 3107 and the center of the three-dimensional magneto-optical well includes a fourth quarter wave plate, and the phase adjusting member between the sixth reflecting member 3108 and the center of the three-dimensional magneto-optical well includes a fifth quarter wave plate; the phase adjustment means between the ninth reflecting means 3111 and the centre of the three-dimensional magneto-optical well comprises a sixth quarter-wave plate.

As a preferred embodiment, as shown in fig. 8(c), the first light splitting device 3101 includes a first half-wave plate 31011, a first quarter-wave plate 31013 and a first polarization splitting prism 31016, wherein the first half-wave plate 31011 is disposed between the first polarization splitting prism 31016 and the first collimating device 3119, and the first quarter-wave plate 31013 is disposed between the first polarization splitting prism 31016 and the first reflecting member 3103.

In a preferred embodiment, the second beam splitting device 3102 includes a second half-wave plate 31012, a second quarter-wave plate 31014, a third quarter-wave plate 31015 and a second polarization beam splitting prism 31017, wherein the second half-wave plate 31012 is disposed between the second polarization beam splitting prism 31017 and the first polarization beam splitting prism 31016, the second quarter-wave plate 31014 is disposed between the second polarization beam splitting prism 31017 and the seventh reflecting member 3109, and the third quarter-wave plate 31015 is disposed between the second polarization beam splitting prism 31017 and the second reflecting member 3104.

In a preferred embodiment, an optical power monitoring unit 6 is further connected to the second optical splitter 3102.

As a preferred embodiment, as shown in fig. 1, fig. 2(a) - (b) and fig. 7, the second optical path structure 3 includes a raman light collimation adjustment device 3201 disposed on the upper support member 21 and a raman light reflection device 3202 disposed on the lower support member 23;

the raman light collimation adjustment device 3201 is used for adjusting the emergent direction of raman light, so that the emergent direction is superposed with a gravity field; the raman light reflecting device 3202 is used to reflect the second laser beam back to the original path to generate a superimposed raman band to induce the atoms to interfere.

As a preferred embodiment, the raman light collimation adjustment device 3201 includes a second collimation device and a collimation frame fixed thereto, wherein the collimation frame is used for adjusting the light emergent direction of the second collimation device; the raman light reflecting device 3202 includes a raman mirror and an adjusting bracket for fixing the raman mirror, and the adjusting bracket is used for adjusting the mirror surface direction of the raman mirror so that the light beam reflected by the mirror surface coincides with the second laser beam.

As a preferred embodiment, as shown in fig. 1, 2(a) and 7, the third optical path structure includes a third collimating device 3301 disposed on the middle support member and a blowing light reflecting member 3302 adjacent thereto, the third collimating device 3301 is configured to provide a third laser beam, and the blowing light reflecting member 3302 reflects the third laser beam to the center of the three-dimensional magnetic trap, so that, during the microwave state selection and the raman speed selection, high-temperature atoms with a magnetic photon energy level different from 0 are blown off, and atoms with a magnetic photon energy level of 0 and a low speed are selected.

As a preferred embodiment, as shown in fig. 1, fig. 2(a) - (b) and fig. 7, the fourth optical path structure includes a fourth collimating device fixed on the lower support member and a detecting light reflecting member 3402 associated therewith, the fourth collimating device is used for providing a fourth laser beam for detecting the position of atoms, wherein the fourth collimating device is opposite to the detecting region of the quantum absolute gravimeter, the detecting light reflecting member 3402 is disposed opposite to the fourth collimating device, and the fourth optical path structure is used for detecting atoms with F =2 state and F =1 state.

As a preferred embodiment, as shown in fig. 1, 2(a) and 2(b), the magnetic field unit is disposed at the middle support member and includes a three-dimensional magneto-optical trap coil 71 and a C-field coil, wherein, as shown in fig. 1 and 9, the three-dimensional magneto-optical trap coil 71 includes a pair of anti-helmholtz coils respectively fixed at both sides of the vacuum chamber and providing a magnetic field with a gradient of about 10 Gauss/cm; the C-field coil comprises a helmholtz coil extending in a vertical direction, which provides a uniform magnetic field of about 300 mG.

In a preferred embodiment, the probe system further comprises a magnetic shielding unit surrounding the probe for shielding the interfering magnetic field in the gravity measurement environment, and the magnetic shielding unit is preferably made of permalloy.

In a preferred embodiment, the probe system further comprises a microwave unit for generating microwaves for screening out atoms in a state insensitive to magnetic fields.

As a preferred embodiment, the probe system further comprises an atomic number monitoring device 4 disposed on the middle support member and facing the center of the three-dimensional magneto-optical trap for monitoring the number of atoms captured.

In a preferred embodiment, the probe system further comprises a fluorescence collection device, which is directly opposite to one of the second optical windows 112.

In a preferred embodiment, the probe system further comprises an inclinometer 5, the inclinometer 5 being arranged on the lower support member for assisting in the determination and adjustment of the vertical direction.

In a preferred embodiment, the probe system further comprises an accelerometer for acquiring real-time vibration signals.

As a preferred embodiment, the probe system further includes a horizontal adjustment base, the horizontal adjustment base is disposed below the measurement portion and the support frame 2, and the contact degree between the entire measurement portion and the gravitational field can be adjusted by adjusting the inclination angle of the horizontal adjustment base.

As a preferred embodiment, the probe system further comprises a vibration isolation platform, which is disposed below the horizontal adjustment base, and on which the adjustment device of the raman light reflection device 3202 is disposed, and which isolates random vibration noise of the lower bearing surface.

The basic principle on which the invention is based is: alkali metals (for example rubidium atoms) are cooled to cold atoms of the order of 10 micro-openings in a vacuum environment under the interaction of a magnetic field and an optical field. And then closing the magnetic field and the optical field, and performing free falling body motion on cold atoms under the action of the gravity field, firstly performing quantum state preparation in the process, and after the preparation is completed, starting Raman light after the cold atoms enter an interference region, so that the cold radicals generate substance wave interference. And when the atomic groups continue to fall to the interference region, collecting atomic signals by adopting normalized fluorescence detection. And finally, obtaining an absolute gravity acceleration value by methods of vibration compensation, inclination correction, system error elimination and the like. Based on this principle, the implementation process of the present invention can be generally divided into: instrument adjustment, cold atom loading, quantum state preparation, cold atom interference, normalized detection, vibration compensation, inclination correction and system error elimination are carried out for 8 steps; the method comprises the following specific steps:

and (3) instrument adjustment:

firstly, the horizontal adjustment base is adjusted, and bubbles in a level on the base are observed, so that the gravity meter is in a horizontal state. Then, a diaphragm is added to the Raman light outlet, and the diaphragm hole is as small as possible. A box filled with water is placed on the bottom vibration isolation platform. And adjusting the Raman light collimation device to enable Raman reflected light to coincide with incident light. At this time, the second laser beam emitted from the raman light collimation adjustment device 3201 coincides with the gravity direction. And then the box filled with water is taken off, the Raman light reflector adjusting device is arranged on the vibration isolation platform, and the Raman light reflector adjusting device is adjusted to enable the reflected light to coincide with the incident light.

Cold atom loading step:

as can be seen from the foregoing, the three-dimensional magneto-optical trap is composed of three pairs of oppositely emitted cooling light beams and a pair of anti-helmholtz coils, and the cooling light beams include two pairs of first cooling light beams 3116 and 3117 at 45 ° to the vertical direction and a pair of second cooling light beams 3118 in the horizontal direction. The two oppositely incident first cooling light beams 3116, 3117 are circularly polarized light opposite to each other. The atoms are gradually cooled and trapped under the action of the three-dimensional magneto-optical trap, and the process is called Doppler cooling. And when the Doppler cooling is finished and the temperature of the atoms is reduced to 100 mu K magnitude, carrying out polarization gradient cooling to further reduce the temperature of the atomic groups. Meanwhile, the atomic number monitoring system can be used for collecting atomic fluorescence signals in real time, converting the atomic fluorescence signals into electric signals and calculating the number of captured atoms.

Quantum state preparation:

after the atom group capture is completed, the quantum state preparation is needed next. The quantum state preparation comprises two steps: firstly, microwave state selection; secondly, Raman speed selection. The purpose of microwave state selection is to select a state insensitive to a magnetic field, and the purpose of Raman speed selection is to reduce the velocity distribution of atomic groups in the vertical direction and obtain atoms at a lower temperature. This process must be performed within a magnetic shield in order to shield stray magnetic fields such as the earth's magnetic field. Firstly, opening a C field to define a quantization axis, wherein the direction of the quantization axis is parallel to the direction of Raman light, then realizing the transfer of atoms on each energy state through two microwave pi pulses and one Raman pi pulse, and removing atoms on other magnetic photon energy levels by combining a third laser beam (namely, a blowing laser beam), and finally realizing the preparation of the quantum state.

Cold atom interference step:

after the quantum state preparation is finished, cold atomic groups enter an interference region, Raman light acts in the vertical direction, atomic wave packet interference is subjected to beam splitting, deflection and beam combination through a three-beam Raman pulse sequence pi/2-pi/2, and atomic substance wave interference is finally caused.

A normalized fluorescence detection step:

when the atoms fall into the detection area, the atom signals are collected by adopting a normalized fluorescence detection method. When the atoms fall to the first beam of the detection light standing wave, the atoms on the F =2 state emit fluorescence, are collected by an atomic fluorescence collection system, are transmitted to a high-speed data acquisition card through photoelectric conversion and amplification, and can be considered as an atomic population P2 of the F =2 state. After completion of the probing, atoms on the F =2 state are blown away. The atoms in the F =1 state continue to fall, are prepared again in the F =2 state by the action of the re-pumping light, and are detected by the lower detection light, which can be regarded as the atom layout number P1 of the F =1 state. The normalized atomic number can be written as P = P2/(P2 + P1), and the influence of atomic number jitter can be eliminated by using the normalized detection method.

A vibration compensation step:

random vibration acceleration in the vertical direction of the ground causes the raman mirror to vibrate, thereby affecting the measurement result. The Raman light reflector adjusting device is placed on the shock insulation platform and can isolate random high-frequency vibration noise on the ground. Meanwhile, the accelerometer collects real-time low-frequency vibration signals, and compensation is carried out in an active feedback mode, so that the gravity measurement sensitivity can be improved.

A tilt correction step:

the inclinometer 5 is placed on the lower supporting plate 23, the inclination angles of the lower supporting plate 23 in two horizontal directions are measured, the measurement resolution is smaller than 1 micro radian, the inclination angles in the X direction and the Y direction are output in real time and are acquired by a computer at a high speed, and the inclinometer is mainly used for determining and adjusting the vertical direction and assisting in correcting absolute gravity measurement.

And (3) eliminating system errors:

and eliminating system errors by reversing Raman light wave vectors, halving Raman light power and reversing the probe by 180 degrees in combination with solid tide and sea tide models, measuring atmospheric pressure data in real time, calculating polar coordinates in real time and the like, and finally fitting to obtain an absolute gravity acceleration value.

Further, it should be noted that:

in the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and not to be construed as limiting the present invention, and those skilled in the art can make changes, modifications, substitutions and alterations to the above embodiments without departing from the principle and spirit of the present invention, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention still fall within the technical scope of the present invention.

Claims (8)

1. A probe of a quantum absolute gravimeter is characterized by comprising a measuring part and a support frame (2); the measuring part is arranged on the support frame (2);

the measuring part comprises an ultrahigh vacuum unit (1) for capturing atoms and providing free falling space for the atoms, and the periphery of the ultrahigh vacuum unit (1) is provided with a light path structure which is connected with a laser system of the quantum absolute gravimeter and is used for guiding and generating a plurality of laser beams and a magnetic field unit which is matched with the light path structure to generate a three-dimensional magneto-optical trap for cooling and capturing the atoms; wherein, the top, the side wall and the bottom of the ultrahigh vacuum unit (1) are all limited with optical windows for injecting laser beams necessary for absolute gravity measurement; the ultrahigh vacuum unit (1) comprises an integrally formed titanium alloy cavity (11), a vacuum pipeline (12) communicated with the top of the titanium alloy cavity (11) and a vacuum pumping device (13) communicated with the vacuum pipeline (12), wherein the titanium alloy cavity (11) is a cuboid, a three-dimensional magneto-optical well region, an interference region and a detection region are respectively configured in the titanium alloy cavity from top to bottom, the upper end and the lower end of the titanium alloy cavity (11) are open, an upper optical window and a lower optical window are respectively defined on each side of the titanium alloy cavity, a first optical window (111) on the upper portion is over against the three-dimensional magneto-optical well region, a second optical window (112) on the lower portion is over against the detection region, an opening on the upper end of the titanium alloy cavity (11) is connected with the vacuum pipeline (12) through a connecting component, and a third optical window (113) is configured at an opening on the lower end of the titanium alloy cavity (11);

the supporting frame (2) is limited with an upper supporting part, a middle supporting part and a lower supporting part which are arranged at intervals, the adjacent supporting parts are connected through a supporting rod (24), the optical path structure is arranged on the upper supporting part, the middle supporting part and the lower supporting part, the magnetic field unit is arranged on the middle supporting part, through holes are formed in the upper supporting part, the middle supporting part and the lower supporting part, the through holes in the middle supporting part are used for embedding the ultrahigh vacuum unit (1), and the through holes in the upper supporting part are used for avoiding laser beams which are emitted from the optical structure part of the upper supporting part and enter the top of the ultrahigh vacuum unit (1);

the optical path structure comprises a first optical path structure for realizing three beams of cooling light beams of the three-dimensional magneto-optical trap; the first light path structure comprises a first collimating device (3119) and an optical assembly coupled with the first collimating device (3119) and used for dividing a laser beam emitted by the first collimating device (3119) into two oppositely-emitted first cooling light beams (3116, 3117) inclined at 45 degrees relative to the vertical direction and one oppositely-emitted second cooling light beam (3118) injected along the horizontal direction and vertically intersected with the two first cooling light beams (3116, 3117);

the optical assembly comprises a plurality of optical components which are at least arranged on three reference planes between the upper supporting component and the middle supporting component, wherein the first reference plane is higher than the center of the three-dimensional magneto-optical trap, the second reference plane is as high as the center of the three-dimensional magneto-optical trap, and the third reference plane is lower than the center of the three-dimensional magneto-optical trap.

2. A quantum absolute gravimeter probe according to claim 1, wherein each first optical window (111) and each second optical window (112) on the adjacent side of the titanium alloy cavity (11) are correspondingly disposed at the same height, and the bottom of the first optical window (111) is higher than the middle support member, and the top of the second optical window (112) is lower than the middle support member.

3. A quantum absolute gravimeter probe according to claim 2, wherein the length of the first optical window (111) is not less than its width, and the incident laser beam of the three-dimensional magneto-optical trap is injected from the first optical window (111) and converged in the titanium alloy cavity (11); one pair of opposite first optical windows (111) is used for injecting two oppositely emitted first cooling light beams (3116, 3117) into the titanium alloy cavity (11) in a crossing manner, and meanwhile, one of the first optical windows (111) is also used for injecting a blowing laser beam; another pair of opposing first optical windows (111) is for injecting a second cooling beam (3118) perpendicular to the two first cooling beams (3116, 3117) in the horizontal direction.

4. A quantum absolute gravimeter probe according to claim 1, characterized in that the length of the second optical window (112) is not less than its width, wherein a pair of opposite second optical windows (112) is used for injection of a detection laser beam for detecting atoms.

5. A Quantum absolute gravimeter probe according to claim 1, characterized in that the fourth optical window (114) at the top of the ultra high vacuum unit (1) is directly opposite to the third optical window (113) at the bottom of the titanium alloy cavity (11), the fourth optical window (114) is used for feeding Raman laser beam into the ultra high vacuum unit (1), and the Raman laser beam is reflected by the Raman light reflection device (3202) below the third optical window (113) and returns to the titanium alloy cavity (11) to form interference laser beam.

6. A quantum absolute gravimeter probe according to claim 1, wherein the optical assembly comprises a first beam splitter (3101), a second beam splitter (3102), a first reflective member (3103), a fourth reflective member (3106), a fifth reflective member (3107), a sixth reflective member (3108), an eighth reflective member (3110) and a ninth reflective member (3111); wherein the action surface of the first reflecting member (3103) and/or the fourth reflecting member (3106) is provided on a first reference plane, the action surfaces of the eighth reflecting member (3110) and the ninth reflecting member (3111) are provided on a second reference plane, and the action surface of the fifth reflecting member (3107) and/or the sixth reflecting member (3108) is provided on a third reference plane; the acting surfaces of the first reflecting member (3103), the fourth reflecting member (3106), the fifth reflecting member (3107), the sixth reflecting member (3108), the eighth reflecting member (3110) and the ninth reflecting member (3111) are all right opposite to the center of the three-dimensional magneto-optical trap; the first reflecting component (3103) and the sixth reflecting component (3108) are positioned on one side of the center of the three-dimensional magneto-optical trap, and the fourth reflecting component (3106) and the fifth reflecting component (3107) are positioned on the other side of the center of the three-dimensional magneto-optical trap; phase adjusting components for changing the phase of the light beams and enabling the opposite light beams to be mutually opposite in phase are arranged between the acting surfaces of the fifth reflecting component (3107), the sixth reflecting component (3108) and the ninth reflecting component (3111) and the center of the three-dimensional magneto-optical trap;

the first light splitting device (3101) is connected with the first collimating device (3119) and is used for splitting the laser beam emitted by the first collimating device (3119) into a first secondary light beam and a second secondary light beam, the propagation directions of the first secondary light beam are mutually perpendicular, the first secondary light beam directly or indirectly enters the second light splitting device (3102), the second secondary light beam directly or indirectly enters the action surface of the first reflecting component (3103), the second secondary light beam is reflected by the first reflecting component (3103), propagates along the direction which is inclined by 45 degrees and sequentially penetrates through the center of the three-dimensional magneto-optical trap and the corresponding phase adjusting component, and then is perpendicularly incident on the action surface of the fifth reflecting component (3107), and the fifth reflecting component (3107) reflects the second secondary light beam back to the original circuit to form a first cooling light beam (3116) which is opposite to the perpendicular direction by 45 degrees;

the first secondary light beam is divided into a third secondary light beam and a fourth secondary light beam by a second light splitting device (3102), the propagation directions of the third secondary light beam are mutually vertical, the third secondary light beam directly or indirectly enters an action surface of a fourth reflecting component (3106), the third secondary light beam is reflected by the fourth reflecting component (3106), then propagates along the direction of 45 degrees downwards in an inclined way, penetrates through the center of the three-dimensional magneto-optical trap and a corresponding phase adjusting component and then vertically enters an action surface of a sixth reflecting component (3108), and the sixth reflecting component (3108) reflects the third secondary light beam back to the original way so as to form another first cooling light beam (3117) which is opposite to the vertical direction at 45 degrees;

the fourth order light beam directly or indirectly enters the action surface of an eighth reflecting component (3110), is reflected by the eighth reflecting component (3110), penetrates through the center of the three-dimensional magneto-optical trap and a corresponding phase adjusting component along the horizontal direction perpendicular to the two cooling light beams, and then vertically enters the action surface of a ninth reflecting component (3111), and the ninth reflecting component (3111) reflects the fourth order light beam back to the original circuit to form a second cooling light beam (3118) which is opposite to the horizontal direction.

7. A quantum absolute gravimeter probe according to claim 6, wherein the first optical path structure further comprises a second reflective member (3104), a third reflective member (3105) and a seventh reflective member (3109);

the second reflecting member (3104) and the third reflecting member (3105) are arranged on a propagation path of the third secondary light beam, and are used for changing the propagation direction of the third secondary light beam so as to avoid the three-dimensional magneto-optical trap and simultaneously propagate to the opposite side of the three-dimensional magneto-optical trap;

the seventh reflecting member (3109) is provided on a propagation path of the fourth-order light beam, and directly or indirectly reflects the fourth-order light beam onto the eighth reflecting member (3110).

8. The quantum absolute gravimeter is characterized by comprising a control system, a laser system and a probe which are connected with each other through electric wires and/or optical fibers; the control system comprises a controller and a plurality of mechanical shutters connected with the controller and capable of eliminating corresponding laser beams when needed;

the laser system is used for providing a laser light source which is used for generating a plurality of laser beams for assisting in cooling, capturing, blowing, interfering and detecting atoms; the probe of any one of claims 1-7.

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