SQUID-based inner centering superconducting gravity measurement device and method

Abstract

The invention discloses an SQUID-based inner centering superconductive gravity measurement device and method, and belongs to the technical field of gravity measurement, the device comprises an SQUID, an input coil, a detection cavity, a superconductive suspension body, a torquer cavity, a suspension coil and a coil support base which are arranged from top to bottom; the input coil and the detection coil are in superconducting connection to form a detection loop; the detection coil induces the vertical displacement of the superconducting suspension body and converts the vertical displacement into a current signal, and the current signal is coupled to the input coil in magnetic flux coupling with the SQUID through the detection loop; the SQUID converts the magnetic flux change into a voltage signal and outputs the voltage signal, so that high-precision detection of displacement is realized; a detection coil is arranged in the detection cavity, and a torquer is arranged in the torquer cavity; different currents are introduced into the first torque superconducting loop and the second torque superconducting loop of the torquer, so that the inclination state of the superconducting suspension body is adjusted. According to the invention, the problem of poor stability of high-precision dynamic gravity measurement is effectively solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gravity measurement, and particularly relates to an internal centering superconducting gravity measurement device and method based on SQUID. BACKGROUND

[0002] High-precision gravity measurement is of great significance for in-depth research in the fields of geodynamics, resource exploration, geodesy and the like. So far, the superconducting gravity meter based on the zero-resistance characteristic and Meissner effect of superconductor is the highest-precision gravity measurement instrument recognized in the world. The demand for high-precision gravity measurement under dynamic conditions is increasing in the fields of airborne geophysical prospecting and marine gravity measurement. Since the vibration noise of a moving carrier under dynamic conditions is at least 3-4 orders of magnitude higher than that under static conditions, the radial and axial support stiffness of the suspended test mass in the superconducting gravity measurement instrument needs to be further increased than that under static conditions, and therefore, increasing the support stiffness of the suspended test mass will help to enhance the dynamic stability of the superconducting gravity measurement instrument. The superconducting gravity meter that has been commercialized uses very small support stiffness to ensure high gravity measurement precision, but the small support stiffness results in poor dynamic adaptability of the superconducting gravity measurement instrument. SUMMARY

[0003] To solve the above technical problems, the application adopts the following technical scheme:

[0004] An internal centering superconducting gravity measurement device based on SQUID, comprising, from top to bottom, a SQUID, an input coil, a detection cavity, a superconducting suspension body, a torque device cavity, a suspension coil, a coil support base and a controller.

[0005] The input coil and the detection coil are superconductively connected to form a detection loop, and the input coil and the detection coil are both superconducting coils; the detection coil senses the vertical displacement of the superconducting suspension body and converts it into a current signal, which is coupled to the input coil that is magnetically coupled to the SQUID through the detection loop; the SQUID converts the change of magnetic flux into a voltage signal output, realizing high-precision detection of displacement.

[0006] The detection cavity is provided with a detection coil, the torque device cavity is provided with a torque device support and a torque device arranged on the torque device support; the torque device comprises four superconducting coils, the four superconducting coils are divided into two groups, each group comprises two cross-wound coils, and the two cross-wound coils form a first torque superconducting loop on the left and a second torque superconducting loop on the right, respectively; by passing different currents into the first torque superconducting loop and the second torque superconducting loop, the inclination state of the superconducting suspension body is adjusted.

[0007] An internal centering superconducting gravity measurement method based on SQUID, used in the internal centering superconducting gravity measurement device based on SQUID, comprising:

[0008] Step 1, passing current to the superconducting coil through the controller to keep the superconducting suspension body vertical and radially have stable stiffness;

[0009] Step 2, passing suspension current to the suspension coil by using high-precision current source to make the superconducting suspension body suspended;

[0010] Step 3, gradually adjusting the current in the four superconducting coils of the suspension coil and the moment device to make the superconducting suspension body suspended at a suitable position;

[0011] Step 4, real-time controlling the tilting state of the superconducting suspension body along the horizontal direction by the controller;

[0012] Step 5, when the suspension and radial tilting control adjustment of the superconducting suspension body 1 is completed, passing a small current to the detection coil by using high-precision current source, and then opening the SQUID to measure the displacement of the superconducting suspension body.

[0013] The present application has the following beneficial effects:

[0014] The present application can improve the displacement measurement resolution of the suspended test mass in the superconducting gravity measurement instrument by using the high-precision quantum flux detection of SQUID, and the improvement of the displacement resolution can provide adjustment margin for further increasing the support stiffness of the suspended test mass, effectively solving the problem of poor dynamic stability caused by the small support stiffness of the suspended test mass in the current commercial superconducting gravity measurement instrument. On the other hand, the present application uses the moment device to support and control the radial direction of the superconducting suspended test mass, greatly increases the radial support stiffness, and improves the radial support stability. Through the synchronous improvement of the radial and axial support stiffness of the suspended test mass, the problem of poor stability in high-precision dynamic gravity measurement is effectively solved. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a structure schematic diagram of the SQUID-based internal centering superconducting gravity measurement device, 1-superconducting suspension body, 2-moment device support, 3-moment device cavity, 4-detection cavity, 5-suspension coil, 6-detection coil, 7-input coil, 8-SQUID, 9-moment device, 10-controller, 14-coil support base;

[0016] Figure 2 It is a three-dimensional structure schematic diagram of the superconducting suspension body, wherein 11 is a partition, 12 is a radial support tube, and 13 is a circular flat plate. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0018] The present application adopts SQUID to measure the axial displacement with high precision, improves the measurement precision of the sensitive axis; and adopts a torque device in the radial direction to improve the support stiffness of the non-sensitive axis. The combination of the two is conducive to the application of the device to high-precision dynamic gravity measurement.

[0019] As shown in Figure 1 The SQUID-based internal centering superconducting gravity measurement device of the present application comprises, from top to bottom, a SQUID (superconducting quantum interference device) 8, an input coil 7, a detection cavity 4, a superconducting suspension body 1, a torque device cavity 3, a suspension coil 5, a coil support base 14, and a controller 10. The detection coil 6 is arranged in the detection cavity 4, and the torque device support 2 and the torque device 9 arranged on the torque device support 2 are arranged in the torque device cavity 3. The torque device 9 comprises four superconducting coils, which are divided into two groups, each group comprising two cross-wound coils (two coils are wound in a double-wire parallel-wound manner on the same skeleton, and a differential magnetic field is generated when opposite currents are passed through, which is used to adjust the inclination angle of the suspension body), which respectively constitute a first torque superconducting loop on the left and a second torque superconducting loop on the right. By passing different currents through the two torque superconducting loops, the inclination state of the superconducting suspension body 1 can be adjusted.

[0020] As shown in Figure 2 The superconducting suspension body 1 is an integrated mechanical processing structure, comprising a partition plate 11, a radial support tube 12, and a circular flat plate 13. The surfaces of each component are covered with superconducting material or made entirely of superconducting material (preferably niobium or lead). The partition plate 11 separates the detection cavity 4 and the torque device cavity 3 along the same axis, which passes through the center of the superconducting suspension body 1. The circular flat plate 13 is suspended above the suspension coil 5, and an upward electromagnetic suspension force is induced on the circular flat plate 13 by passing a current through the suspension coil 5, thereby driving the superconducting suspension body 1 into a suspended state.

[0021] In this embodiment, the detection coil 6 is arranged at the bottom of the detection cavity 4, the input coil 7 is superconductively connected with the detection coil 6 to form a detection loop; the torque device 9 is sleeved on the torque device support 2 and accommodated in the torque device cavity 3; and the controller 10 is externally arranged on the main body of the measurement device and electrically connected with the torque device 9.

[0022] Preferably, the axial depth of the moment coil cavity 3 is greater than the detection cavity 4, so that the moment coil 9 can obtain a greater moment adjustment range, according to the formula: M=FL, when the moment coil 9 generates an electromagnetic force F, the greater the force arm L, the greater the generated moment M, and a greater radial support stiffness will be obtained;

[0023] Preferably, the detection coil 6 is close to the bottom of the detection cavity 4, so as to obtain a better electromagnetic shielding effect.

[0024] The input coil 7 and the detection coil 6 are superconductively connected to form a detection loop, both of which are superconducting coils. The detection coil 6 senses the vertical displacement of the superconducting suspension body 1 and converts it into a current signal, which is coupled to the input coil 7 through the detection loop, and the input coil 7 is magnetically coupled to the SQUID 8; the SQUID 8 converts the magnetic flux change into a voltage signal output, realizing high-precision displacement detection. The SQUID 8 outputs a voltage signal related to displacement change, realizing high-precision displacement detection.

[0025] In actual application, due to the uncertainty of the external magnetic field environment, the SQUID 8 and the input coil 7 need to be well shielded, generally requiring single-layer or multi-layer shielding, and in multi-layer shielding, high magnetic permeability materials and superconducting materials are used for combined shielding, preferably, when multi-layer composite shielding is performed, the outer shielding uses high magnetic permeability materials to preliminarily shield the static magnetic field, and the inner layer uses superconducting shielding to shield the remaining static magnetic field and alternating magnetic field to achieve good shielding effect.

[0026] The moment coil support 2 is used to fix the superconducting coils in the moment coil 9, and the superconducting coils are oppositely wound in pairs to generate a correction moment in the horizontal plane, so as to maintain the vertical attitude of the superconducting suspension body 1.

[0027] The superconducting suspension body 1 is controlled in the horizontal direction by the superconducting coils in the moment coil 9; the controller 10 is connected to the superconducting coils in the moment coil 9 and realizes the tilt control of the superconducting suspension body 1 through PID control output.

[0028] The device further comprises a high-precision current source for supplying power to the suspension coil 5 and the detection loop.

[0029] The above-mentioned SQUID-based internal centering superconducting gravity measurement device utilizes the high-precision displacement detection of SQUID and the radial adjustment and support of the moment coil 9, so as to realize the large stiffness support of the non-sensitive axis and the high-precision gravity measurement of the sensitive axis, and improve the dynamic adaptability of gravity measurement. The device is easy to operate and has good implementation effect.

[0030] The application also provides an SQUID-based internal centering superconducting gravity measurement method for the above-mentioned SQUID-based internal centering superconducting gravity measurement device, comprising:

[0031] Step 1, the superconducting coil is supplied with current (such as 10A current; the greater the current, the greater the support stiffness, the better the stability, 10A is within the safety margin of the superconducting coil) by the controller 10, so that the superconducting suspension body 1 is kept vertical and has radial stability.

[0032] Step 2, the suspension current (such as 3.5A suspension current; different currents correspond to different suspension positions) is supplied to the suspension coil 5 by using a high-precision current source, so that the superconducting suspension body 1 is suspended.

[0033] Step 3, gradually adjust the current in the superconducting coils of the suspension coil 5 and the moment device 9, so that the superconducting suspension body 1 is suspended at a suitable position.

[0034] Step 4, the controller 10 controls the real-time control of the tilt state of the superconducting suspension body in the horizontal direction.

[0035] During the suspension and support stiffness adjustment process of the above-mentioned steps 2 and 3, the superconducting suspension body 1 will inevitably tilt due to the change of the magnetic field. At this time, the tilt of the superconducting suspension body 1 needs to be adjusted by the moment device 9. The adjustment principle of the tilt is as follows: the superconducting coil of the moment device 9 can realize the tilt control of the superconducting suspension body 1. Assuming that the initial state of the superconducting suspension body 1 is coaxial with the moment device 9, the current in the two superconducting loops of the moment device 9 is equal. When the superconducting suspension body 1 is deflected due to the adjustment of the suspension current or the tilt of the whole device, assuming that the superconducting suspension body is deflected to the right, the distance between the moment superconducting loop 1 in the moment device 9 and the inner wall of the moment device cavity 3 becomes smaller, while the distance between the moment superconducting loop 2 in the moment device 9 and the inner wall of the moment device cavity 3 becomes larger. At this time, the current in the moment superconducting loop 1 is increased by the controller 10, and the torque in the deflection direction is increased, so that the superconducting suspension body 1 is deflected back to the initial vertical state. At the same time, the current in the moment superconducting loop 2 can also be reduced by the controller 10, and the torque in the opposite direction of the deflection direction is reduced, so that the superconducting suspension body 1 is deflected back to the initial vertical state. Alternatively, the two methods can be performed simultaneously. When the superconducting suspension body 1 is deflected back to the vertical state, the current adjustment is stopped, and thus the controller 10 completes a control process of the superconducting suspension body 1. In actual application, the controller 10 controls the tilt of the superconducting suspension body 1 by controlling the current in the superconducting coil of the moment device 9 in real time, so that the superconducting suspension body 1 always maintains a vertical state, and the support stability of the non-sensitive axis is improved.

[0036] Step 5, after the suspension of the superconducting suspension body 1 and the radial tilt control adjustment are completed, a small current is supplied to the detection coil 6 by a high-precision current source, and then the SQUID is opened to measure the displacement of the superconducting suspension body 1.

[0037] In step 5, according to the formula: F=kΔx=mΔg, when the gravity acceleration changes, the superconducting suspension body 1 will produce a certain displacement to cause the distance between the detection coil 6 and the superconducting suspension body 1 to change, and the current in the detection coil 6 will change when the distance between the detection coil 6 and the superconducting suspension body 1 changes, the current change is coupled to the SQUID 8 through the input coil 7 connected with the detection coil 6, and finally the SQUID 8 outputs a voltage signal representing the gravity change of the superconducting suspension body 1, so that the gravity measurement is realized. Wherein, F is the force change of the superconducting suspension body 1, k is the suspension support stiffness of the superconducting suspension body 1, Δx is the displacement caused by the force change of the superconducting suspension body 1, m is the mass of the superconducting suspension body 1, and Δg is the change of the gravity acceleration.

[0038] The gravity measurement method needs to ensure that the low-temperature system is normally operated and the whole device reaches the liquid helium bath temperature 4.2K before the energization experiment is performed.

[0039] The above description is only an embodiment of the present application, and does not limit the patent range of the present application, and any equivalent structure or equivalent flow transformation using the content of the specification and the drawings, or direct or indirect application in other related system fields, are also included in the protection range of the present application.

[0040] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art.

Claims

1. A SQUID-based internally centered superconducting gravity measurement device, characterized in that, Comprise: SQUID, input coil, detection cavity, superconducting suspension body, torque cavity, suspension coil, coil support base, controller arranged from top to bottom; The input coil and the detection coil are superconductively connected to form a detection loop; the detection coil senses the vertical displacement of the superconducting suspension body and converts it into a current signal, which is coupled to the input coil coupled to the magnetic flux of the SQUID through the detection loop; the SQUID converts the magnetic flux change into a voltage signal output, realizing high-precision detection of displacement; The detection cavity is provided with a detection coil, the torque cavity is provided with a torque support and a torque in the torque support; the torque includes four superconducting coils, which are divided into two groups, each group including two cross-wound coils, respectively forming a first left torque superconducting loop and a second right torque superconducting loop; by passing different currents into the first torque superconducting loop and the second torque superconducting loop, the tilt state of the superconducting suspension body is adjusted.

2. The SQUID-based, internally centered superconducting gravity measurement device of claim 1, wherein, The superconducting suspension body is an integrated mechanical processing structure, comprising a partition, a radial support tube and a circular flat plate; the partition separates the detection cavity and the torque cavity along the same axis, which passes through the center of the superconducting suspension body; the circular flat plate is suspended above the suspension coil, and an upward electromagnetic suspension force is generated on the circular flat plate by passing a current into the suspension coil, thereby driving the superconducting suspension body into a suspended state.

3. The SQUID-based, internally centered superconducting gravity measurement device of claim 1, wherein, The surface of each component in the superconducting suspension body is covered with superconducting material or made of superconducting material as a whole.

4. The SQUID-based, internally centered superconducting gravity measurement device of claim 1, wherein, The detection coil is arranged at the bottom of the detection cavity, and the input coil and the detection coil are superconductively connected to form a detection loop; the torque is sleeved on the torque support and contained in the torque cavity; the controller is externally connected to the main body of the measuring device and electrically connected to the torque.

5. The SQUID-based, internally centered superconducting gravity measurement device of claim 1, wherein, The axial depth of the torque cavity is greater than that of the detection cavity.

6. The SQUID-based, internally centered superconducting gravity measurement device of claim 1, wherein, The detection coil is close to the bottom of the detection cavity.

7. The SQUID-based, internally centered superconducting gravity measurement device of claim 1, wherein, The torque support is used to fix the superconducting coils in the torque, and the superconducting coils are oppositely wound in pairs to generate a correction torque in the horizontal plane to maintain the vertical attitude of the superconducting suspension body; The superconducting suspension body is tilted in the horizontal direction by the superconducting coils in the torque; the controller is connected to the superconducting coils in the torque, and the tilt control of the superconducting suspension body is realized by PID control output.

8. The SQUID-based, internally centered superconducting gravity measurement device of claim 1, wherein, The SQUID and the input coil are shielded by single or multiple layers, and the high magnetic permeability material and the superconducting material are used for combined shielding in the multiple layers.

9. A SQUID-based internally centered superconducting gravity measurement method for a SQUID-based internally centered superconducting gravity measurement apparatus as claimed in any one of claims 1 to 8, characterized in that Comprise: Step 1, pass a current into the superconducting coil through the controller to keep the superconducting suspension body vertical and have stable radial stiffness; Step 2, pass a suspension current into the suspension coil using a high-precision current source to make the superconducting suspension body float; Step 3, gradually adjust the current in the suspension coil and the four superconducting coils of the torque to make the superconducting suspension body float in the appropriate position; Step 4, control the tilt state of the superconducting suspension body in the horizontal direction in real time through the controller; Step 5, when the superconducting suspension body is floated and the radial tilt control is adjusted, pass a small current into the detection coil through a high-precision current source, and then open the SQUID to measure the displacement of the superconducting suspension body.

10. The SQUID-based, internally centered superconducting gravity measurement method of claim 9, wherein, In step 5, when the gravitational acceleration changes, the superconducting suspension body will produce a certain displacement, which causes the distance between the detection coil and the superconducting suspension body to change, and the current in the detection coil will change when the distance between the detection coil and the superconducting suspension body changes. The current change is coupled to the SQUID through the input coil, and the SQUID outputs a voltage signal representing the change of the gravity of the superconducting suspension body, thereby realizing the measurement of the gravity; wherein F is the change of the force of the superconducting suspension body, k is the suspension support stiffness of the superconducting suspension body, Δx is the displacement caused by the change of the force of the superconducting suspension body, m is the mass of the superconducting suspension body, and Δg is the change of the gravitational acceleration.

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