A small-size high-precision gravimeter based on diamagnetic suspension principle

Abstract

This invention relates to the field of gravity measurement, aiming to provide a small-sized, high-precision gravimeter based on the principle of antimagnetic levitation. The gravimeter includes a low-frequency magnetic potential trap unit, a levitation oscillator unit, a displacement detection unit, and a cavity enclosure unit. The lens groups of the low-frequency magnetic potential trap unit, the levitation oscillator unit, and the displacement detection unit are all located in the cavity of the innermost insulated shell. This invention provides a measurement environment free from external influences for displacement detection of the levitation oscillator, counteracts adjustments to the vertical frequency in the antimagnetic levitation potential trap, and uses a photoelectric converter to measure voltage fluctuations caused by changes in laser intensity to reflect the motion of the object under test, achieving high-precision gravity measurement. The oscillator uses magnetic levitation and does not have mechanical contact with the environment, avoiding long-term irreversible deformation. It eliminates the need for bulky temperature control and magnetic shielding devices or other auxiliary equipment; therefore, the overall size of the gravimeter is small, easy to move, and inexpensive, facilitating widespread adoption.

Description

Technical Field

[0001] This invention belongs to the field of gravity measurement, and more specifically relates to a small-sized, high-precision gravimeter based on the principle of antimagnetic levitation. Background Technology

[0002] A gravimeter is an instrument used to measure gravitational acceleration and is of great significance in fields such as geophysics and underground resource exploration. Currently, gravimeters can be mainly divided into two categories: absolute gravimeters and relative gravimeters.

[0003] In gravity measurement, absolute gravimeters offer higher precision; for example, domestic absolute gravity measurement systems based on cold atoms can achieve a detection sensitivity of approximately 10 μGal. However, absolute gravimeters are large, complex in structure, and expensive, making them difficult to use and maintain, which hinders their widespread application. The basic principle of relative gravimeters is that an elastic body deforms under gravity. When the elastic force of the elastic body is balanced with gravity, the elastic body is at a certain equilibrium position. When gravity changes, the equilibrium position of the elastic body changes. By observing the change in equilibrium position between two points, the gravitational difference can be determined. The weight of a constant mass *m* in a gravitational field varies with *g*. If another force (elastic force, electromagnetic force, etc.) is used to balance this change in weight or gravitational torque, then by observing the equilibrium state of the object, it is possible to measure the gravitational difference between two points. Based on the different ways in which an object is displaced by changes in gravity, gravimeters can be divided into two main categories: translational (or linear displacement) gravimeters and rotational (or angular displacement) gravimeters. Widely used examples include metal spring gravimeters and quartz spring gravimeters, but these types of gravimeters usually have poor measurement accuracy.

[0004] Researchers have proposed a relative gravimeter using a mechanical oscillator. The principle is to measure the positional change of the mechanical oscillator caused by changes in gravity. The response of the mechanical oscillator to external acceleration is as follows:

[0005]

[0006] Where ω0 is the eigenfrequency of the oscillator, ω is the frequency of the external acceleration to be measured, and γ is the dissipation coefficient of the oscillator.

[0007] When the system needs to measure steady accelerations similar to gravity, i.e., when the external acceleration frequency ω→0: Right now Therefore, in order to improve the acceleration measurement accuracy 'a', it is necessary to improve the displacement detection accuracy 'x' of the system and reduce the eigenfrequency of the mechanical oscillator.

[0008] In existing solutions for constructing mechanical oscillator gravimeters, systems that simultaneously meet both requirements are typically quartz springs or MEMS (Micro-Electro-Mechanical Systems). However, these systems are constrained by the inherent properties of the materials themselves. During use, the irreversible deformation of the materials leads to significant linear drift in gravity measurements, often exceeding 500 uGal / day. This severely impacts the accuracy and stability of measurements, making it difficult to meet the increasingly demanding precision requirements of various applications. On the other hand, levitation systems that do not require mechanical contact with the environment, such as optical levitation and electro-levitation, require a continuous input of external energy to maintain levitation. This not only significantly increases the operating costs of the equipment but also introduces additional noise, interfering with the measurement signal and reducing measurement accuracy. In contrast, magnetic levitation technology plays a crucial role in low-loss transportation, precision signal sensing, inertial navigation, and precision mechanics. Compared to traditional mechanical systems, such as MEMS, magnetic levitation systems offer significant advantages such as low loss, long lifespan, and zero energy consumption, making them highly promising for gravimeter applications. However, because magnetic levitation systems are sensitive to factors such as temperature and magnetic field fluctuations in the external environment, they require large-scale temperature control and magnetic shielding devices to maintain stable levitation. This results in the entire device being large in size and expensive, which greatly limits its potential for large-scale industrialization.

[0009] In summary, based on the many shortcomings of existing relative gravimeter technology, this invention proposes a small-sized, high-precision gravimeter based on the principle of antimagnetic levitation, aiming to effectively solve the above problems and meet the needs of high-precision gravity measurement in practical applications. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a small-sized, high-precision gravimeter based on antimagnetic levitation.

[0011] To solve the technical problem, the solution of the present invention is:

[0012] A small-sized, high-precision gravimeter based on antimagnetic levitation is provided, comprising:

[0013] The low-frequency magnetomotive force trap unit includes a magnetically confined potential trap formed by multiple permanent magnets arranged in an axially symmetrical manner; by changing the relative positions of the permanent magnets, the frequency and confinement position of the magnetically confined potential trap can be adjusted.

[0014] The levitation oscillator unit includes an oscillator suspended in a magnetically confined potential well, and a light-blocking component extending from the top of the oscillator into the magnetically confined potential well.

[0015] The displacement detection unit includes a laser, a lens group, and a photoelectric converter, with the light-blocking component located in the optical path inside the lens group;

[0016] The cavity enclosure unit includes an outer shell, a magnetic shielding shell, and a thermal insulation shell nested in sequence and maintaining a distance between them, with the cavity of each shell kept vacuum; the lens groups of the low-frequency magnetic potential trap unit, the levitation oscillator unit, and the displacement detection unit are all located in the cavity of the innermost thermal insulation shell.

[0017] As a preferred embodiment of the present invention, the plurality of permanent magnets are divided into upper and lower layers, and the permanent magnets in each layer are arranged in a surrounding manner; the upper layer magnet has a hollow cavity structure in the center, and the oscillator is suspended in the cavity; the magnetization direction of the lower layer magnet points to the center, and the magnetic field lines converge in the central region to generate a magnetic field and magnetic field gradient in the vertical direction, providing antimagnetic force and constraint to overcome gravity; the magnetization direction of the upper layer magnet points from the center to the outside, providing constraint in the horizontal direction.

[0018] As a preferred embodiment of the present invention, the vertical frequency of the magnetic confinement potential well is adjusted by changing the relative distance between the upper and lower permanent magnets; the confinement position of the magnetic confinement potential well is adjusted by changing the relative distance between the permanent magnets in each layer and their enclosing center.

[0019] As a preferred embodiment of the present invention, the oscillator is a monolithic structure made of antimagnetic graphite or metal material; the oscillator is a columnar structure with a circular or regular polygonal cross-section and a relatively constricted bottom.

[0020] As a preferred embodiment of the present invention, the light-blocking component is located in the optical path inside the lens group in the displacement detection unit to serve as the object of displacement monitoring, specifically a horizontal bar or a light-blocking plate provided on the horizontal bar; the vertical bar fixed to the top of the oscillator is connected to the horizontal bar, and the latter is located outside the magnetic confinement potential well.

[0021] In a preferred embodiment of the present invention, the emitting end of the laser is connected to the first optical fiber, the receiving end of the photoelectric converter is connected to the second optical fiber, and the lens group is located between the emitting end of the first optical fiber and the incident end of the second optical fiber; the lens group includes at least two convex lenses, and the light-blocking component is located at the focal point of the lens group.

[0022] As a preferred embodiment of the present invention, the bottom of the outer casing is seated on the base, and a plurality of foot screws are provided at the bottom of the base;

[0023] The magnetic shielding shell is mounted on the bottom plate of the outer shell via a heat-insulating pad, and the thermal insulation shell is mounted on the bottom plate of the magnetic shielding shell via a heat-insulating pad; alternatively, the magnetic shielding shell is suspended from the top plate of the outer shell via a thermal insulation rope, and the thermal insulation shell is suspended from the top plate of the magnetic shielding shell via a thermal insulation rope; the outer shell, the magnetic shielding shell, and the thermal insulation shell are all provided with sealed side doors in the same direction for installing and adjusting the low-frequency magnetomotive force trap unit and the levitation mechanical oscillator unit, with the low-frequency magnetomotive force trap unit mounted on the bottom plate of the thermal insulation shell.

[0024] As a preferred embodiment of the present invention, the magnetic shielding shell is in multiple sets and nested sequentially with a spacing; the heat insulation shell is in multiple sets and nested sequentially with a spacing; the cavity of each shell is kept vacuum.

[0025] As a preferred embodiment of the present invention, a temperature probe and an electric heater are provided inside the insulation shell, and a temperature controller is provided on the outside of the outer shell. The temperature probe and the electric heater are connected to the temperature controller via cables; or, the laser and the photoelectric converter are installed on the outside of the outer shell.

[0026] The present invention further provides a method for using the aforementioned high-precision gravimeter, including:

[0027] (1) Confirm that all components in the gravimeter are in good condition and that the oscillator is located in the magnetic confinement potential well;

[0028] (2) By changing the relative positions of each permanent magnet in this layer, the constraint position of the magnetic confinement potential well is adjusted so that the oscillator is stably suspended in the upper cavity and the light-blocking component is located in the optical path inside the lens group; by changing the relative positions of the upper and lower permanent magnets, the vertical frequency of the magnetic confinement potential well is adjusted to meet the measurement requirements.

[0029] (3) Close the sealed side doors of each shell, evacuate the cavity between each shell, and set the temperature of the temperature controller according to the measurement scheme;

[0030] (4) Start the laser and use the photoelectric converter to measure the voltage fluctuation caused by the vertical movement of the light-blocking component; according to the pre-calibrated vertical displacement and voltage relationship curve, obtain the vertical displacement of the oscillator and further calculate the change in gravity.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. The gravimeter proposed in this invention uses an antimagnetic levitation potential well composed of permanent magnets, which can provide horizontal constraint to counteract the gravitational field of the mass without any external energy consumption; thus providing a measurement environment free from external influences for the displacement detection of the suspended oscillator, thereby improving the accuracy of acceleration measurement.

[0033] 2. This invention can adjust the vertical frequency in the anti-magnetic levitation potential well by adjusting the distance between the upper and lower permanent magnets, thereby meeting the oscillator frequency requirements for gravity measurement.

[0034] 3. This invention places the suspended oscillator at the focal point of the laser beam path and uses a photoelectric converter to measure the voltage fluctuation caused by the change in laser intensity to reflect the motion of the object under test, thus achieving high-precision gravity measurement.

[0035] 4. The oscillator adopts magnetic levitation and does not come into mechanical contact with the environment, which can avoid long-term irreversible deformation of materials. Actual measurements show that the linear drift of gravity measurement can be suppressed to below 100uGal / day.

[0036] 5. The device of the present invention only needs to place the key measuring components inside the heat-insulating magnetic shielding shell, without the need for bulky temperature control and magnetic shielding devices or other auxiliary equipment. Therefore, the overall size of the gravimeter is small, easy to move, and low in cost, which is conducive to its promotion. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the gravimeter in this invention.

[0038] Figure 2 This is a schematic diagram of the antimagnetic levitation potential well in this invention.

[0039] Figure 3 This is a schematic diagram of the magnetic field generated by two magnets that are tightly attached together.

[0040] Figure 4 This is a schematic diagram of the magnetic field generated by a magnet composed of two alternating layers.

[0041] Figure 5 This is a schematic diagram of a suspended oscillator.

[0042] Figure 6 This is a schematic diagram of the optical path in the displacement detection unit.

[0043] Figure 7 This is a graph showing the relationship between voltage and displacement obtained through a photoelectric converter.

[0044] The attached diagram is labeled as follows: Upper magnet 1; Lower magnet 2; Oscillator 3; Displacement detection unit 4; Vertical rod 401; Laser 402; Photoelectric converter 403; Temperature control unit 5; Temperature probe 501; Electric heater 502; Temperature controller 503; Insulation shell 6; Magnetic shielding shell 7; Outer shell 8; Heat insulation pad 9; Machine foot screw 10. Detailed Implementation

[0045] I. Description of the Invention Principle

[0046] 1. Magnetic levitation principle:

[0047] A substance of mass m and volume V (assuming volume V is small) placed in a static magnetic field B(r) will be induced to produce a magnetic moment μ(r):

[0048]

[0049] Where χ is the magnetic susceptibility, and for diamagnetic materials, χ < 0; μ0 = 4π × 10 -7 N / A 2, is the free permeability, and its corresponding magnetic potential energy E(r) can be expressed as:

[0050]

[0051] According to Engshaw's theorem, in a static magnetic field without current, the magnitude of the magnetic field strength has no local maxima. Therefore, only diamagnetic materials can be stably bound to the minimum point of the static magnetic field. However, the relative magnetic susceptibility of typical diamagnetic materials is |χ| << 1. To ensure that the diamagnetic material can be stably suspended in the potential field, the total force... It must be zero, that is:

[0052]

[0053] in Represents the magnetic field gradient, e z The vector representing the upward direction indicates that the magnetic force on the suspended material in the vertical direction is equal to its gravity, while it experiences no magnetic force in the horizontal direction. Furthermore, a stable constraint must satisfy the following conditions: This holds true for both the x, y, and z directions, at which point the frequency of the levitating oscillator is...

[0054] Where i = x, y, z It represents the second derivative of energy E with respect to the x, y, and z directions.

[0055] 2. Low-frequency magnetomotive force trap unit

[0056] (1) Design of magnetically confined potential well:

[0057] The core innovation of this method is the magnetic confinement potential well (antimagnetic levitation potential well). The magnetic confinement potential well must be constructed of permanent magnets, without incurring any external energy consumption; it must be able to counteract the gravitational field of the mass and provide horizontal confinement. This invention proposes a combination of multiple permanent magnets in a double-layer structure, with the upper and lower magnets having opposite polarization directions, thus forming a stable magnetic potential well in the center. Specifically... Figure 1 As shown. Figure 2-4 As shown in the figure, the arrows indicate the magnetization direction of the magnets; that is, the magnetization direction of the lower magnet points towards the center, and the magnetization direction of the upper magnet points outward from the center. For a permanent magnet structure formed by axial symmetry, the horizontal component of the magnetic field at its center is 0, while there is a magnetic field limit point in the vertical direction, which satisfies the magnetic field structure requirements.

[0058] It should be noted that the specific design is not limited to Figure 2-4The structure shown in the figure is an octagonal structure formed by eight permanent magnets in a single layer. Of course, the number of permanent magnets can be changed to different combinations such as 4, 5, 6, or 7, and the specific shape can also be adjusted as needed. Furthermore, precise quantitative analysis of the shape and volume of the permanent magnets using finite element method (FEM) ensures that the overall antimagnetic levitation characteristics remain unchanged. The core of this design is that the lower magnets converge magnetic field lines in the central region, generating a magnetic field and magnetic field gradient in the z-direction, providing antimagnetic force to overcome gravity and providing z-direction constraint. The upper magnets form an enclosed cavity structure in the center, providing horizontal (x, y) constraint. This creates a magnetic confinement potential well within the cavity structure, allowing the oscillator to achieve stable levitation in three directions. Based on this magnetic confinement design, the number of permanent magnets, as well as the specific geometry and dimensions of the permanent magnets and oscillator, can be adjusted as needed, without substantially changing the implementation principle of the magnetic confinement potential well frequency and constraint position.

[0059] (2) Frequency adjustment:

[0060] The magnetic potential well constructed directly according to the above description, if used directly, will have a vertical frequency... Typically above 2π×10Hz ( The second derivative of energy E with respect to z is insufficient for gravity measurement, necessitating further adjustments to the permanent magnet structure.

[0061] like Figure 3 As shown, if the magnetic fields generated by the upper and lower layers of magnets in the composite magnet are written as B1(r) and B2(r) respectively, then the total magnetic field B(r) = B1(r) + B2(r) and the total energy...

[0062] At this time, the levitation position z0 of the diamagnetic body satisfies:

[0063]

[0064] The corresponding frequency at this time

[0065] like Figure 4 As shown, if the position of the upper magnet is moved up by l, then the levitation position of the diamagnetic body will move down to z1, satisfying:

[0066]

[0067] Where g represents gravitational acceleration; the subscript z indicates that the above two equations hold true at z = z0 and z = z1, respectively.

[0068] The frequency also decreased accordingly.

[0069] Through COMSOL finite element simulation and actual measurement by the applicant's research team, the vertical frequency can be reduced to as low as 2π×1.5Hz, which meets the frequency requirements of mechanical oscillators for gravity measurement.

[0070] 3. Suspension oscillator unit

[0071] As previously stated, the force balance condition required for the oscillator to levitate is:

[0072]

[0073] The oscillator is preferably made of a highly diamagnetic material, such as graphite or bismuth, to utilize its diamagnetism to resist gravity and achieve levitation in a magnetic field. Since the oscillator experiences no force in the horizontal direction, its shape is best designed as a cylinder or regular polygon that is axially symmetric about the vertical direction. Furthermore, according to COMSOL finite element simulation results, the bottom of the oscillator needs to be appropriately narrowed to prevent the oscillator from flipping over in its levitation state.

[0074] In addition, a T-shaped or cross-shaped fixed structure needs to be formed at the top of the oscillator using rods, in which a light-blocking plate is set on the horizontal rod (or the horizontal rod is directly used as a light-blocking component) for position detection in the optical path; the vertical rod is used to make the light-blocking component extend out of the magnetic confinement potential trap.

[0075] 4. Displacement detection unit

[0076] The displacement detection unit includes a laser, a lens group, and a photoelectric converter. A light-blocking component is located within the optical path of the lens group. An optical fiber connects to the laser for input laser light, which is focused onto the light-blocking component after passing through the front lens. Light diverging from the light-blocking component is collected by the rear lens and enters the optical fiber, where it is received by the photoelectric converter. The motion of the object under test is reflected by measuring the voltage fluctuation of the photoelectric converter.

[0077] Since the voltage of the photoelectric converter is proportional to the received light intensity, it is only necessary to directly measure the relationship curve between the displacement of the light-blocking component and the voltage. By pre-positioning the relative positions of the lens group and the light-blocking component in the vertical direction, the voltage V can be measured. z The fluctuations were observed, and a relationship curve was plotted. In subsequent practical applications, the vertical position of the fiber optic group was adjusted to move the optical path focus to the position on the light-blocking component where the voltage was most sensitive to displacement (e.g., ...). Figure 7 (At the upper box of the middle curve). At this point, the voltage and displacement are approximately linear, therefore it can be written as:

[0078] ΔV z =ξz·Δz

[0079] Where Δz represents the magnitude of the vertical displacement of the light-blocking component; ΔV zξz represents the voltage change under that displacement; ξz represents the voltage-displacement conversion coefficient in the vertical direction.

[0080] By using voltage values ​​to represent light intensity, the light intensity-displacement conversion coefficient can be measured. According to the applicant's research team's measurements, the conversion coefficient in the horizontal direction is more than an order of magnitude smaller than that in the vertical direction. This suggests that the total voltage change measured by the photoelectric converter only reflects the vertical displacement. Therefore, voltage changes can be used to assess the amount of displacement under the influence of gravity.

[0081] 5. Cavity Enclosure Unit

[0082] The system noise in a gravimeter mainly includes temperature noise and tilt noise. To further reduce system noise, this invention proposes a multi-nested shell design for the device. The cavity enclosure unit achieves insulation and magnetic shielding while simultaneously creating vacuum isolation, and a temperature control unit implements multi-level PID temperature control. The device's levelness is controlled by mounting screws under the cavity enclosure unit's base, ensuring the tilt angle during measurement meets requirements.

[0083] II. Specific Implementation Plan

[0084] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0085] 1. Structural Description of the Gravimeter

[0086] like Figure 1 As shown, the high-precision gravimeter based on the antimagnetic levitation principle provided by the present invention specifically includes: a low-frequency magnetic potential well unit, a levitation oscillator unit, a displacement detection unit, and a cavity enclosure unit. The low-frequency magnetic potential well unit includes a magnetically confined potential well formed by multiple permanent magnets arranged axially symmetrically; by changing the relative positions of the permanent magnets, the frequency and confinement position of the magnetically confined potential well can be adjusted. The levitation oscillator unit includes an oscillator 3 suspended in the magnetically confined potential well, and a light-blocking component extending from the top of the oscillator 3 into the magnetically confined potential well. The displacement detection unit includes a laser 402, a lens group, and a photoelectric converter 403, with the light-blocking component located in the optical path inside the lens group. The cavity enclosure unit includes an outer shell 8, a magnetically shielded shell 7, and a thermal insulation shell 6 nested sequentially and maintaining a distance between them, with the cavities of each shell maintained as vacuum. The lens groups of the low-frequency magnetic potential well unit, the levitation oscillator unit, and the displacement detection unit are all located within the cavity of the innermost thermal insulation shell 6.

[0087] The outer casing 8 rests on the base, which has multiple mounting screws 10 for adjusting its level and controlling the tilt angle. The magnetic shielding casing 7 rests on the base plate of the outer casing 8 via a heat insulation pad 9, and the insulation casing 6 rests on the base plate of the magnetic shielding casing 7 via a heat insulation pad 9. Alternatively, it can be suspended, with the magnetic shielding casing 7 suspended from the top plate of the outer casing 8 via an insulation rope, and the insulation casing 6 suspended from the top plate of the magnetic shielding casing 7 via an insulation rope. For ease of operation, sealed side doors are provided in the same direction on the outer casing 8, the magnetic shielding casing 7, and the insulation casing 6 for installing and adjusting the low-frequency magnetomotive force trap unit and the levitation oscillator unit. The low-frequency magnetomotive force trap unit rests on the base plate of the innermost insulation casing 6. Multiple sets of magnetic shielding casings 7 can be nested sequentially with spacing; multiple sets of insulation casings 6 can also be nested sequentially with spacing. The cavities of adjacent casings are kept vacuum. Temperature probe 501 and electric heater 502 are located on the innermost heat-insulating shell 6, and temperature controller 503 is located on the outer side of the outer shell 8. Temperature probe 501 and electric heater 502 are connected to temperature controller 503 by cables, and together they form temperature control unit 5.

[0088] like Figure 2-4 As shown, the low-frequency magnetic potential trap unit has multiple permanent magnets arranged in two layers, with the permanent magnets in each layer forming a confined arrangement. The upper magnet 1 has a central cavity structure, in which the oscillator 3 is suspended. The lower magnet 2 is magnetized towards the center, and the magnetic field lines converge in the central region to generate a vertical magnetic field and magnetic field gradient, providing antimagnetic force and constraint to overcome gravity. The magnetization direction of the upper magnet 1 points outward from the center, providing horizontal constraint. By changing the relative distance between the upper and lower permanent magnets, the vertical frequency of the magnetic confinement potential trap is adjusted; by changing the relative distance between the permanent magnets in each layer and their confined centers, the constraint position of the magnetic confinement potential trap is adjusted.

[0089] like Figure 5 As shown, the oscillator 3 is a monolithic structure made of antimagnetic graphite or metal, shaped like a column with a circular or regular polygonal cross-section and a relatively constricted bottom. A light-blocking component is located in the optical path inside the lens group of the displacement detection unit, serving as the object for displacement monitoring; specifically, it is a horizontal bar or a light-blocking plate mounted on the horizontal bar. A vertical bar 401 fixed to the top of the oscillator 3 is connected to the horizontal bar to form a T-shaped or cross-shaped structure, positioning the horizontal bar outside the magnetic confinement potential well.

[0090] like Figure 6As shown, the emitting end of laser 402 is connected to the first optical fiber, and the receiving end of photoelectric converter 403 is connected to the second optical fiber. A lens group is located between the emitting end of the first optical fiber and the incident end of the second optical fiber. The lens group in the figure includes two convex lenses, and the light-blocking component is located at the focal point between the first lens and the second lens. Laser 402 and photoelectric converter 403 are mounted on the outside of the outer casing 8.

[0091] 2. Instructions for use of the gravimeter

[0092] The high-precision gravimeter based on the antimagnetic levitation principle described in this invention is used in the following ways:

[0093] (1) Confirm that all components in the gravimeter are in good condition and that the oscillator is located in the magnetic confinement potential well;

[0094] (2) By changing the relative positions of each permanent magnet in this layer, the constraint position of the magnetic confinement potential well is adjusted so that the oscillator 3 is stably suspended in the upper cavity and the light-blocking plate is located in the optical path inside the lens group; by changing the relative positions of the upper and lower permanent magnets, the vertical frequency of the magnetic confinement potential well is adjusted to meet the measurement requirements.

[0095] (3) Close the sealed side doors of each shell, evacuate the cavity between each shell, and set the temperature of the temperature controller 503 according to the measurement scheme.

[0096] (4) Start the laser 402 and use the photoelectric converter 403 to measure the voltage fluctuation caused by the vertical movement of the light-blocking plate; according to the pre-calibrated vertical displacement and voltage relationship curve, obtain the vertical displacement of the oscillator 3 and further calculate the change in gravity.

[0097] 3. Specific application examples

[0098] The thermal insulation shell 6 is positioned within the magnetic shielding shell 7, supported by the thermal insulation pad 9. The magnetic shielding shell 7 is also positioned within the vacuum chamber shell 8, supported by the thermal insulation pad 9. Both the space between the thermal insulation shell 6 and the magnetic shielding shell 7, and the space between the magnetic shielding shell 7 and the vacuum chamber shell 8, are vacuum environments. The thermal insulation pad 9 is preferably made of polyetheretherketone (PEEK) or ceramic, which has low thermal conductivity, further maintaining the temperature stability inside the thermal insulation shell 6. The thermal insulation pad 9 is installed at the bottom of both the thermal insulation shell 6 and the magnetic shielding shell 7 to improve the stability of the support.

[0099] Another optional installation method is as follows: the thermal insulation shell 6 is suspended inside the magnetic shielding shell 7 by thermal insulation ropes, and the magnetic shielding shell 7 is suspended inside the vacuum chamber shell 8 by thermal insulation ropes. The installation direction and number of thermal insulation ropes can be changed according to specific application requirements, and the material of the thermal insulation ropes is aluminum silicate.

[0100] The shapes of the thermal insulation shell 6, the magnetic shielding shell 7, and the vacuum chamber shell 8 can be cylindrical or cuboid.

[0101] Furthermore, multiple insulating shells 6 can be set, for example, including three layers of insulating shells 6, nested sequentially with spacing, and vacuumed to improve the insulation effect. Furthermore, an independent temperature control unit 5 can be set for each individual insulating shell 6. Multiple magnetic shielding shells 7 can be set, for example, including three layers of magnetic shielding shells 7 nested sequentially with spacing, and vacuumed to improve the shielding effect against external magnetic fields. The nested shell structures are connected by heat insulation pads 9 or heat insulation ropes to maintain the stability between the multiple shells. The vacuum environment formed between the shells can prevent gas heat exchange, and combined with the low thermal conductivity of the heat insulation pads 9 or heat insulation ropes, further reduces heat conduction. Thus, when the temperature outside the vacuum chamber shell 8 changes, due to its low thermal conductivity, the temperature of the insulating shell 6 can remain stable for a long time. This nested structure achieves the first stage of passive temperature control. Even when the external temperature changes by 1K, the temperature change of the insulating shell 6 will be less than 1mK. The above process does not require the participation of the temperature control unit 5.

[0102] Furthermore, temperature sensor 501 measures the inner wall temperature of the insulation shell 6 and transmits the measured temperature data to PID temperature controller 503 outside the insulation shell 6. PID temperature controller 503 adjusts the heating power of heater 502 in real time based on the measured temperature fluctuations to maintain a stable temperature inside the insulation shell 6. Combined with the first-stage passive temperature control, the average temperature fluctuation can be less than 0.1 mK. The vacuum environment inside each shell cavity can be considered as the second-stage passive temperature control. Combined with temperature control unit 5, the temperature fluctuation of the insulation shell 6 can be kept within 0.1 mK, ultimately allowing the temperature fluctuation of the levitation oscillator unit to reach the 10 μK level.

[0103] When the tilt angle of the entire device is θ, the vibrator 3 will be subjected to a gravitational component in the vertical direction. To improve the stability of the device during use, the outer casing 8 is fixedly connected to the base. The connection method can be riveting, welding, or snap-fit. Multiple foot screws 10 (e.g., three precision-adjustable screws) are installed at the bottom of the base using a threaded connection. The foot screws 10 are arranged in a triangle below the base, and adjusting them allows for platform leveling. According to actual measurements, the tilt angle of the entire device can be controlled to be θ < 10°. -5 To avoid generating tilt noise during the measurement process.

[0104] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A small-sized, high-precision gravimeter based on the principle of antimagnetic levitation, characterized in that, include: A low-frequency magnetic potential well unit includes a magnetically confined potential well formed by multiple permanent magnets arranged symmetrically along the axis. The permanent magnets are divided into upper and lower layers, with each layer containing magnets arranged in a confined manner. The upper layer magnet has a central cavity structure in which an oscillator is suspended. The lower layer magnets are magnetized towards the center, and magnetic field lines converge in the central region to generate a vertical magnetic field and magnetic field gradient, providing antimagnetic force and confinement to overcome gravity. The upper layer magnets are magnetized outwards from the center, providing horizontal confinement. The vertical frequency of the magnetically confined potential well is adjusted by changing the relative distance between the upper and lower layers of permanent magnets. The confinement position of the magnetically confined potential well is adjusted by changing the relative distance between each permanent magnet and its confining center. The levitation oscillator unit includes an oscillator suspended in a magnetic confinement potential well, and a light-blocking component extending from the top of the oscillator into the magnetic confinement potential well; the oscillator is a single-unit structure made of antimagnetic graphite or metal material, and the shape of the oscillator is a columnar structure with a circular or regular polygonal cross-section and a relatively contracted bottom; The displacement detection unit includes a laser, a lens group, and a photoelectric converter, with the light-blocking component located in the optical path inside the lens group; The cavity enclosure unit includes an outer shell, a magnetic shielding shell, and a thermal insulation shell nested sequentially and maintaining a distance between them, with the cavities of each shell kept vacuum; the lens groups of the low-frequency magnetic potential trap unit, the levitation oscillator unit, and the displacement detection unit are all located in the cavity of the innermost thermal insulation shell; The insulation shell is equipped with a temperature probe and an electric heater inside, and a temperature controller is located on the outside of the outer shell. The temperature probe and the electric heater are connected to the temperature controller via cables.

2. The gravimeter according to claim 1, characterized in that, The light-blocking component is located in the optical path inside the lens group in the displacement detection unit to be used as a displacement monitoring object. Specifically, it is a horizontal bar or a light-blocking plate set on the horizontal bar. The vertical bar fixed to the top of the oscillator is connected to the horizontal bar and the latter is located outside the magnetic confinement potential well.

3. The gravimeter according to claim 1, characterized in that, The laser emitter is connected to a first optical fiber, the photoelectric converter receiver is connected to a second optical fiber, and the lens group is located between the emitting end of the first optical fiber and the incident end of the second optical fiber; the lens group includes at least two convex lenses, and the light-blocking component is located at the focal point of the lens group.

4. The gravimeter according to claim 1, characterized in that, The bottom of the outer casing sits on the base, and multiple foot screws are provided at the bottom of the base; The magnetic shielding shell is mounted on the bottom plate of the outer shell via a heat-insulating pad, and the thermal insulation shell is mounted on the bottom plate of the magnetic shielding shell via a heat-insulating pad; alternatively, the magnetic shielding shell is suspended from the top plate of the outer shell via a thermal insulation rope, and the thermal insulation shell is suspended from the top plate of the magnetic shielding shell via a thermal insulation rope; the outer shell, the magnetic shielding shell, and the thermal insulation shell are all provided with sealed side doors in the same direction for installing and adjusting the low-frequency magnetomotive force trap unit and the levitation mechanical oscillator unit, with the low-frequency magnetomotive force trap unit mounted on the bottom plate of the thermal insulation shell.

5. The gravimeter according to claim 1, characterized in that, The magnetic shielding shells are in multiple sets, nested sequentially with a certain distance between them; the thermal insulation shells are in multiple sets, nested sequentially with a certain distance between them; the cavities of each shell are kept under vacuum.

6. The method of using the gravimeter according to any one of claims 1 to 5, characterized in that, include: (1) Confirm that all components in the gravimeter are in good condition and that the oscillator is located in the magnetic confinement potential well; (2) By changing the relative positions of each permanent magnet in this layer, the constraint position of the magnetic confinement potential well is adjusted so that the oscillator is stably suspended in the upper cavity and the light-blocking component is located in the optical path inside the lens group; by changing the relative positions of the upper and lower permanent magnets, the vertical frequency of the magnetic confinement potential well is adjusted to meet the measurement requirements. (3) Close the sealed side doors of each shell, evacuate the cavity between each shell, and set the temperature of the temperature controller according to the measurement scheme; (4) Start the laser and use the photoelectric converter to measure the voltage fluctuation caused by the vertical movement of the light-blocking component; according to the pre-calibrated vertical displacement and voltage relationship curve, obtain the vertical displacement of the oscillator and further calculate the change in gravity.

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