Device for measuring resistance of superconducting joint

Abstract

The utility model provides a device for measuring the resistance of a superconducting joint. The device comprises a low-temperature Dewar and a refrigerator, the system further comprises a test system. The test system is suspended in the low-temperature Dewar; the refrigerator provides a cold source for the low-temperature Dewar; the test system comprises a magnet exciting coil, a background magnet and an induction ring fixing groove; the excitation coil and the background magnet are assembled on the bottom plate, and the bottom plate is suspended in the low-temperature Dewar; the magnet exciting coil is sleeved with the induction ring fixing groove, the induction ring fixing groove and the magnet exciting coil are coaxial, and a Hall sensor is further arranged in the center of the magnet exciting coil. The center position of the background magnet is used for placing a superconducting joint. According to the utility model, the measuring system is arranged in the low-temperature Dewar in a suspension manner, is independent from each other and can be separated from each other, so that the refrigeration mode can be changed at will.

Description

Technical Field

[0001] The utility model relates to the technical field of low-temperature superconducting joint preparation and optimization, in particular to a device for measuring the resistance of a superconducting joint. Background Art

[0002] Superconducting joint technology is one of the key technologies of superconducting magnets. Superconducting joints undertake the important task of connecting the electrical circuit of the magnet and are widely used in magnets that require high uniformity of tightly wound solenoid coils, such as magnetic resonance imaging magnets (MRI), nuclear magnetic resonance magnets (NMR) and magnets that operate in a closed loop. The performance of superconducting joints directly determines the stable operation of the magnet, and the performance of superconducting joints is affected by many factors, including the external magnetic field environment, its own mechanical structure, and assembly welding process. Accurate measurement of superconducting joint resistance can help identify potential performance problems of the system, improve the efficiency of the superconducting system, and promote the widespread application of superconducting technology in various fields. Therefore, the development of a reliable and high-precision superconducting joint resistance measurement device is of great significance to promote the advancement of superconducting technology.

[0003] The common method for measuring resistance is the four-lead method, but this method is generally only suitable for measuring resistance greater than 10-9 ohms. The resistance of superconducting joints obtained by today's superconducting joint welding process is generally less than 10-12 ohms, and magnetic resonance imaging magnets (MRI) and nuclear magnetic resonance magnets (NMR) both require even lower resistance for superconducting joints. Measuring such low-level resistance values ​​requires a more sensitive measurement method.

[0004] The current decay method is another commonly used method for measuring superconducting resistance. The superconductor with a superconducting joint is made into a closed loop, namely a joint sample ring. Based on the principle of electromagnetic induction, the current is obtained in the joint sample ring by exciting the main coil. The superconducting joint is located at the center of the magnetic field. Due to the existence of the joint resistance, the current will gradually decay. Based on the record of the decay process, the joint resistance can be measured. The advantages of the induction method are: high test accuracy, convenient and safe operation, greatly reduced operating costs, and shortened experimental cycles.

[0005] Traditional superconducting joint measurement devices all use liquid helium immersion cooling to completely immerse the superconducting joint in liquid helium. Therefore, traditional superconducting joint resistance measurement devices must have a set of cryogenic dewars. All components of the device are placed in a liquid helium tank in the cryogenic dewar for cooling. There are also cold shield systems and vacuum dewar systems outside the liquid helium tank, which makes the superconducting joint resistance measurement device complex in structure and high in cost. The measurement process and sample replacement are also quite cumbersome. In addition, the liquid helium volatilization rate is high, and the operation during the experiment is complicated, which greatly increases the expense and cost of superconducting joint resistance testing. Utility Model Content

[0006] The technical problem to be solved by the utility model is how to reduce the test cost, simplify the test device, and improve the wide adaptability of the test device.

[0007] The utility model solves the above technical problems through the following technical means:

[0008] A device for measuring the resistance of a superconducting joint comprises a cryogenic dewar, a refrigerator and a test system. The test system is suspended in the cryogenic dewar. The refrigerator provides a cold source for the cryogenic dewar.

[0009] The test system includes an excitation coil, a background magnet, and an induction ring fixing groove; the excitation coil and the background magnet are mounted on a bottom plate, and the bottom plate is suspended in a low-temperature dewar; the induction ring fixing groove is sleeved outside the excitation coil and is coaxial with the excitation coil, and a Hall sensor is also arranged at the center of the excitation coil; the center of the background magnet is used to place a superconducting joint. The measurement system in the utility model is located in the low-temperature dewar by suspension, and is independent and separable, so as to facilitate arbitrary changes in the refrigeration method.

[0010] Furthermore, the excitation coil and the background magnet are both fixed by a pressing plate and a bottom plate.

[0011] Furthermore, a slide groove is provided on the bottom plate, and the pressing plate can slide in the slide groove.

[0012] Furthermore, the pressing plate is a Z-shaped plate, one end of which is equipped with the bottom of the winding wheel of the excitation coil / background magnet, and the other end is locked with the slide groove by bolts.

[0013] Furthermore, the induction ring fixing groove is fixed on the base through a column.

[0014] Furthermore, a heating wire support rod is provided between the excitation fairy edge and the background magnet.

[0015] Furthermore, the height of the Hall sensor is half of the excitation coil.

[0016] Furthermore, the Hall sensor is fixed to the center of the excitation coil through a support rod.

[0017] Furthermore, a fixing tube for placing a superconducting joint is placed at the center of the background magnet.

[0018] The utility model also provides a method for measuring the resistance of a superconducting joint, which is applied to the above-mentioned device and includes the following method:

[0019] Fix the excitation coil and background magnet on the base, then place the induction ring in the induction ring fixing groove, place the superconducting joint at the center of the background magnet, and then place the Hall sensor at the set height at the center of the excitation coil; finally, suspend the base on the top cover of the low-temperature Dewar; seal the Dewar, start the refrigerator, turn on the test power, and then you can conduct the test in the set low-temperature environment.

[0020] The advantages of the utility model are:

[0021] 1. The measuring systems in the utility model are suspended in the low-temperature dewar, are independent of each other, and can be separated, so that the refrigeration mode can be changed at will.

[0022] 2. The parts in the measurement system are connected in a detachable way, and the magnets are fixed by a pressure plate. Their positions and heights can be adjusted arbitrarily, and the best measurement results can be obtained through experimental practice. If a part fails, it can be replaced separately without affecting the overall effect of the device, saving costs.

[0023] 3. The device is small in size and easy to operate BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an overall schematic diagram of the device of Example 1 of the utility model;

[0025] Figure 2 This is a schematic diagram of the three-dimensional structure assembly of the measurement system of Example 1 of the utility model;

[0026] Figure 3 This is a schematic diagram of the structure after the excitation coil and the background magnet are hidden in Example 1 of the utility model;

[0027] Figure 4 This is a schematic diagram of the superconducting joint sample structure of Example 1 of the utility model. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the utility model clearer, the technical solution in the embodiments of the utility model will be clearly and completely described below in combination with the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0029] Example 1

[0030] like Figures 1 to 3As shown, this embodiment describes a refrigerator-cooled superconducting joint resistance measurement device based on the current decay method, including a cryogenic system and a measurement system. The cryogenic system is mainly composed of three parts, namely: a refrigerator 17, a cryogenic dewar 16, and a suspension rod 15; the refrigerator 17 is generally fixed on the top of the cryogenic dewar 16. The cryogenic system suspends the measurement system through the suspension rod 15, so that the measurement system is suspended in the cryogenic dewar. The measuring system is mainly composed of nine parts, namely: bottom plate 1, excitation coil 6, Hall plate support rod 2, induction ring fixing groove 5, heating wire support rod 3, background magnet 8, joint fixing tube 4, Z-type pressing plate 9; the excitation coil 6 is coaxial with the Hall plate support rod 2 and the induction ring fixing groove 5, and the height of the induction ring fixing groove 5 (insulating material) and the Hall plate support rod 2 is half of the excitation coil 6, so that the current induced by the transformer transformer composed of them is the largest; the background magnet 8 is coaxial with the joint fixing tube 4, so that the sample joint can be located at the center of the background magnet; the induction ring fixing groove 5, the heating wire support rod 3, and the joint fixing tube 4 are all at the same height, so that the joint sample ring can be fixed horizontally in the device without deformation; the excitation coil 6 and the background magnet 8 are fixed by the Z-type pressing plate 9 with the T-screw 11, the gasket 12, the nut 13, and the tail adjusting screw 10, and the elliptical hole opened on the Z-type pressing plate 9 corresponds to the slide rail 15, so that the Z-type pressing plate 9 can move freely forward and backward, and the position can be adjusted conveniently.

[0031] Specifically, four hanger holes 14 are opened on the base plate 1, and hangers of different sizes can be fixed by nuts of different types. Six threaded holes are opened at corresponding positions of the panel. The Hall plate support rod 2, the three support rods 7 of the induction ring fixing groove 5, the heating wire support rod 3 and the bottom of the joint fixing tube 4 are all threaded and connected to the base plate 1 through these six threaded holes.

[0032] like Figure 4 As shown, the joint sample ring is made by twisting a superconducting wire, which is divided into a single-turn induction ring and a superconducting joint. A superconducting wire is first bent into a single-turn induction ring of a certain diameter, and then two outgoing wires are twisted together to form a twisted pair, and finally a superconducting joint is made. Since the superconducting joint is soft, the single-turn induction ring is placed in the fixing groove 5, and the fixing groove 5 has a notch on the side facing the background magnet, and the superconducting joint is vertically placed in the joint fixing tube 4. The induction ring fixing groove 5 is made of insulating material, coaxial with the excitation coil 6, and half the height of the excitation coil 6. The superconducting joint sample ring and the excitation coil form a mutual inductance transformer, so that an induced current is generated in the joint sample ring. Three threaded holes are evenly distributed at the lower end of the induction ring fixing groove 5, which is fixed by three support rods 7. The heating wire support rod 3 is the same height as the induction ring fixing groove 5, and is used to support the wire part of the heating wire wound between the single-turn induction ring and the superconducting joint to prevent the superconducting joint from shifting due to the excessive weight of the heating wire. The bottom is threaded and connected to the bottom plate 1 through the threaded hole. The material can be stainless steel.

[0033] The front section of the Z-type pressing plate 9 is set as a Z-type notch, which can be engaged with the bottom flange of the winding wheel of the coil. An elliptical through hole and a circular threaded hole are opened in the center. The through hole is in the same direction as the slide groove 18 opened on the bottom plate 1, so that the Z-type pressing plate 9 can move freely forward and backward. The tail adjustment screw 10 passes through the circular threaded hole and is connected to the Z-type pressing plate 9 to fix the position of the Z-type pressing plate 9. The T-type screw 11 passes through the elliptical through hole and is connected to the Z-type pressing plate 9. The nut and the gasket can be used to fix and clamp the Z-type pressing plate 9 and the bottom plate 1, so that the Z-type notch presses the bottom flange of the coil to play the role of pressing the coil.

[0034] In this embodiment, the excitation coil 6 and the background magnet 8 are connected to the bottom plate through a pressure plate device, and the excitation coil 6 and the background magnet 8 are separated by a distance so that their own magnetic fields will not affect each other. The Hall plate support rod 2 is at the same height as the induction ring fixing groove 5, and is half of the excitation coil 6, so that the Hall plate can be fixed at the center of the excitation coil to accurately measure the magnetic field size. The bottom of the Hall plate support rod 2 is threaded and connected to the bottom plate 1 through a threaded hole. The material is stainless steel. The joint fixing tube 4 is coaxial with the background magnet 8, so that the superconducting joint is located at the center of the background magnet, and is at the same height as the induction ring fixing groove 5 and the heating wire support rod 3, so that the superconducting joint sample ring can be placed horizontally. The material is stainless steel.

[0035] Example 2

[0036] Based on the device of Example 1, the method in specific application is:

[0037] Fix the excitation coil and the background magnet on the base, then place the induction ring in the induction ring fixing groove, place the superconducting joint in the center of the background magnet, and then place the Hall sensor at the set height at the center of the excitation coil; hang the assembled measurement system in the low-temperature Dewar through a suspension rod, turn on the refrigerator to make the device reach the low-temperature environment required for the experiment, and the low-temperature Dewar isolates the external heat of the device from the low temperature inside the device, so that the device can maintain a low temperature state continuously and stably.

[0038] Turn on the external power supply to energize the excitation coil to provide current, turn on the heating wire on the superconducting joint sample ring to make the joint quench, then disconnect the heating wire power supply to make the joint sample ring enter the superconducting state, and finally disconnect the excitation coil current, the excitation coil current gradually drops to 0, and an induced current is generated in the joint sample ring. The Hall plate measures the magnetic field size at the center of the street sample ring. Assume that the current at t1 is i1, the current at t2 is i2, and the inductance of the superconducting joint sample induction ring is L. Through the formula The resistance of the superconducting joint can be obtained by calculation.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for measuring the resistance of a superconducting joint, comprising a cryogenic dewar and a refrigerator; characterized in that: It also includes a test system; the test system is suspended in the low-temperature Dewar; the refrigerator provides a cold source for the low-temperature Dewar; The test system includes an excitation coil, a background magnet, and an induction ring fixing groove; the excitation coil and the background magnet are assembled on a base plate, and the base plate is suspended in a low-temperature dewar; the induction ring fixing groove is sleeved outside the excitation coil and is coaxial with the excitation coil, and a Hall sensor is also arranged at the center position of the excitation coil; the center position of the background magnet is used to place a superconducting joint.

2. A device for measuring superconducting joint resistance according to claim 1, characterized in that: The excitation coil and the background magnet are both fixed by a pressing plate and a bottom plate.

3. A device for measuring superconducting joint resistance according to claim 2, characterized in that: The bottom plate is provided with a slide groove, and the pressing plate can slide in the slide groove.

4. A device for measuring superconducting joint resistance according to claim 3, characterized in that: The pressing plate is a Z-shaped plate, one end of which is equipped with the bottom of the winding wheel of the excitation coil / background magnet, and the other end is locked with the slide groove by bolts.

5. A device for measuring superconducting joint resistance according to any one of claims 1 to 4, characterized in that: The induction ring fixing groove is fixed on the base through a column.

6. A device for measuring superconducting joint resistance according to any one of claims 1 to 4, characterized in that: A heating wire support rod is also arranged between the excitation fairy edge and the background magnet.

7. A device for measuring superconducting joint resistance according to any one of claims 1 to 4, characterized in that: The height of the Hall sensor is half of the excitation coil.

8. A device for measuring superconducting joint resistance according to any one of claims 1 to 4, characterized in that: The Hall sensor is fixed to the center of the excitation coil through a support rod.

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