Shielding current induced stress eliminating device, interpolated magnet and hybrid magnet system

Abstract

The invention belongs to the technical field of superconducting electricians, and particularly discloses a shielding current induced stress eliminating device, an interpolated magnet and a hybrid magnet system. According to the invention, the shielding coil is coaxially arranged on the axial outer side of the high-temperature superconducting interpolated magnet, and the magnetic field detection unit is arranged to monitor the vertical magnetic field. The control module dynamically adjusts the excitation current of the shielding coil in stages according to the current signals of the interpolated magnet and the external magnet, and specifically, the control module applies gradually increased reverse direct current when the interpolated magnet starts excitation; the current of the shielding coil is gradually reduced in the excitation process of the external magnet, and the current reduction rate is adjusted according to the vertical magnetic field change condition fed back by the magnetic field detection unit. The vertical magnetic field at the end part of the interpolated magnet is in a descending trend through active regulation and control, and the reverse shielding current is induced at the end part to counteract the initial shielding current, so that the edge concentrated stress is effectively relieved, and the stability and the reliability of the interpolated magnet are improved.

Description

Technical Field

[0001] This application belongs to the field of superconducting electrical technology, and more specifically, relates to a device for eliminating shielding current-induced stress, an intercalated magnet, and a hybrid magnet system. Background Technology

[0002] With the increasing maturity of manufacturing processes for high-temperature superconducting materials, the engineering and practical application of high-temperature superconducting magnets are accelerating. Compared to traditional low-temperature superconducting magnets, high-temperature superconducting magnets have significant advantages in current density, magnetic field resistance, and operating temperature range, thus showing greater potential in ultra-high field applications. Currently, high-temperature superconducting magnets have been gradually applied in several key technology areas, including nuclear magnetic resonance imaging (MRI), high-field NMR spectrometers, steady-state strong magnetic field devices, advanced particle accelerators, and magnetic levitation systems.

[0003] To achieve a high central magnetic field, high-temperature superconducting coils are typically used as intercalation magnets in hybrid magnet systems. During the excitation of the superconducting coil, changes in the local vertical magnetic field induce a large number of concentrated shielding currents at the edges of the superconducting tape. These shielding currents interact with the strong magnetic field, generating concentrated Lorentz forces at the coil edges, resulting in significant circumferential strain in the tape. This strain not only degrades the performance of the superconducting tape but also increases the risk of mechanical degradation, thus posing a challenge to the reliability of high-temperature superconducting coils in ultra-high field applications. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a device for eliminating shielded current-induced stress, an intercalation magnet and a hybrid magnet system, which aim to solve the problem of plastic deformation or even loss of superconductivity in superconducting tapes.

[0005] To achieve the above objectives, in a first aspect, this application provides a device for eliminating shielded current-induced stress, comprising: A shielding coil, coaxially positioned on the outside of the axial end of the target insert magnet, is made of superconducting wire and is used to generate a vertical magnetic field component at the axial end of the target insert magnet that is in the same direction as the vertical magnetic field component of the target insert magnet's own field. A third excitation power supply electrically connected to the shielding coil is used to provide an adjustable DC excitation current to the shielding coil; A magnetic field detection unit is located on the side of the shielded coil near the target inserted magnet, and is used to monitor the total vertical magnetic field component at the location in real time. The control module is connected to the third excitation power supply and the magnetic field detection unit respectively. It is used to control the third excitation power supply to dynamically adjust the magnitude of the DC excitation current applied to the shielding coil in real time according to the operating stage of the target inserted magnet and the external low temperature superconducting magnet and the monitored vertical magnetic field component. This further regulates the vertical magnetic field component of the shielding coil acting on the end of the target inserted magnet, so as to reduce the shielding current in the edge region of the target inserted magnet.

[0006] Preferably, if the shielding coil uses high-temperature superconducting tape, the width of the tape used is smaller than the width of the tape used for the target inserted magnet.

[0007] Preferably, the control module performs phased dynamic closed-loop control on the third excitation power supply: First stage: When the target inserted magnet is energized, the third excitation power supply is controlled to start applying DC excitation current to the shielding coil, gradually increasing it to the preset value, so as to ensure that the shielding coil has sufficient magnetic field regulation capability before entering the second stage. Second stage: When the target inserted magnet is maintained in its rated state and the external low-temperature superconducting magnet is energized, the DC excitation current of the third excitation power supply is gradually reduced to ensure that the reduction of the vertical magnetic field generated by the shielding coil at the end of the inserted magnet is greater than the increase of the vertical magnetic field generated by the external low-temperature superconducting magnet at this point, so that the vertical magnetic field at the end of the inserted magnet shows a monotonically decreasing trend. The third stage: When both the target internal magnet and the external low-temperature superconducting magnet reach their rated values ​​and stabilize, the output current of the third excitation power supply is controlled to return to zero synchronously, so as to avoid additional energy consumption and heat generation of the shielding coil.

[0008] Preferably, the amplitude of the preset value in the first stage The calculation formula is:

[0009] in, For the preset compensation coefficient, ≥1.0, The vertical magnetic field generated at the end of the intercalated magnet by a unit external low-temperature superconducting magnet current. The vertical magnetic field generated at the end of the inserted magnet by the unit shielded coil current. The rated operating current of the external low-temperature superconducting magnet is configured such that the positive and negative signs of the preset value are configured to make the vertical magnetic field component generated by the shielding coil at the end of the target inserted magnet have the same direction as the vertical magnetic field component of the target inserted magnet's own field.

[0010] Preferably, the control of the third excitation power supply to gradually reduce the DC excitation current is as follows: First, based on the change in current of the external low-temperature superconducting magnet Calculate the base adjustment amount :

[0011] in, The vertical magnetic field generated at the end of the intercalated magnet by a unit external low-temperature superconducting magnet current. The vertical magnetic field generated at the end of the inserted magnet by the unit shielded coil current; Subsequently, the total change in the vertical magnetic field was monitored in real time by the magnetic field detection unit. Generate feedback correction amount When detected When a negative feedback correction value is generated. To increase the rate of decrease in the shielding coil current; when detected At that time, feedback correction amount It is zero; Finally, calculate the actual amount of adjustment implemented. .

[0012] To achieve the above objectives, in a second aspect, this application provides a high-temperature superconducting intercalation magnet, integrating a shielding current-induced stress elimination device and a first excitation power supply as described in the first aspect; wherein, In the device for eliminating current-induced stress in shielding, the shielding coil is coaxially positioned on the outer side of the axial end of the high-temperature superconducting intercalation magnet. The first excitation power supply is electrically connected to the high-temperature superconducting intercalation magnet and signal-connected to the control module. It is used to provide the high-temperature superconducting intercalation magnet with an adjustable DC excitation current in both magnitude and direction. The output current serves as one of the detection signals of the control module.

[0013] To achieve the above objectives, in a third aspect, this application provides a hybrid magnet system, comprising: a high-temperature superconducting intercalation magnet as described in the second aspect, an external low-temperature superconducting magnet, and a second excitation power supply; An external low-temperature superconducting magnet is coaxially sleeved on the outside of a high-temperature superconducting intercalation magnet without making contact, and is used to provide a central magnetic field with the same direction as the magnetic field generated by the high-temperature superconducting intercalation magnet. The second excitation power supply is electrically connected to the external cryogenic superconducting magnet and signal-connected to the control module. It is used to provide the external cryogenic superconducting magnet with an adjustable DC excitation current in both magnitude and direction, and the output current serves as one of the detection signals of the control module.

[0014] Preferably, the control module acquires the output current signals of the first excitation power supply and the second excitation power supply in real time, and determines the operating stage of the magnet system based on the two output current signals: When the output current of the first excitation power supply is detected to rise and the output current of the second excitation power supply is zero, or when the output current of the first excitation power supply is detected to be at the rated value and the output current of the second excitation power supply is zero, it is determined to be the first stage. When the output current of the first excitation power supply is maintained at the rated value and the output current of the second excitation power supply rises, it is determined to be the second stage. When the output current of both the first excitation power supply and the second excitation power supply reaches the rated value, it is judged to be in the third stage.

[0015] It is understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0016] Overall, the technical solutions conceived in this application have the following advantages compared with the prior art: This application provides a device for eliminating shielding current-induced stress, an intercalation magnet, and a hybrid magnet system. A shielding coil is coaxially arranged on the outer side of the high-temperature superconducting intercalation magnet, and a magnetic field detection unit is equipped to monitor the vertical magnetic field. The control module dynamically adjusts the excitation current of the shielding coil in stages based on the current signals from the intercalation magnet and the external magnet. Specifically, a gradually increasing reverse DC current is applied when the intercalation magnet is energized; during the excitation of the external magnet, the shielding coil current is gradually decreased, and the rate of current reduction is adjusted according to the changes in the vertical magnetic field fed back by the magnetic field detection unit. This application, through active regulation, causes the vertical magnetic field at the end of the intercalation magnet to show a downward trend, inducing a reverse shielding current at the end to offset the initial shielding current, thereby effectively alleviating edge-concentrated stress and improving the stability and reliability of the intercalation magnet. This application can effectively eliminate the concentrated shielding current and stress in the intercalation magnet without interfering with the steady-state magnetic field, significantly reducing the risk of plastic deformation of the superconducting tape, thereby improving the reliability and service life of the high-temperature superconducting intercalation magnet. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the shielding current induced stress elimination device, the intercalated magnet, and the hybrid magnet system provided in the embodiments of this application.

[0018] Figure 2 This is a two-dimensional axisymmetric schematic diagram of the fully superconducting magnet structure and the shielding current-induced stress elimination device provided in the embodiments of this application.

[0019] Figure 3 This is a graph showing the excitation current of the fully superconducting magnet and shielded coil provided in the embodiments of this application.

[0020] Figure 4A This is a schematic diagram of the magnetic field distribution and shielding current when the intercalated magnet and the shielding coil are synchronously energized, as provided in the embodiments of this application.

[0021] Figure 4B This is a schematic diagram of the magnetic field distribution and reverse shielding current when the excitation current of the shielded coil decays, provided in an embodiment of this application.

[0022] Figure 5A This is a comparison diagram of the simulation results of the vertical magnetic field at the upper edge of the single-pane coil under the embodiment working conditions and the comparative example working conditions provided in this application.

[0023] Figure 5B This is a comparison diagram of the simulation results of the current density at the upper edge of a single disc coil under the embodiment conditions and the comparative embodiment conditions provided in this application.

[0024] Figure 5C This is a comparison diagram of the simulation results of the maximum circumferential strain of a single disc coil during the excitation process under the embodiment conditions and the comparative embodiment conditions provided in this application.

[0025] Figure 6 This is a diagram showing the circumferential stress distribution of a single disc coil when it reaches its maximum circumferential strain under the embodiment and comparative operating conditions provided in this application.

[0026] Figure 7 This is a comparison diagram of the maximum circumferential strain of each single-pane coil in the first interpolated magnet under the embodiment working conditions and the comparative example working conditions provided in this application.

[0027] Figure 8 This is a graph showing the overall maximum circumferential strain of the shielded coil during the excitation process as a function of time, as provided in the embodiments of this application.

[0028] Figure 9 This is a comparison diagram of the simulation results of the change of the central magnetic field strength over time after excitation is completed, under the embodiment working conditions and the comparative working conditions provided in this application.

[0029] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is a shielded coil, 2 is an internal magnet, 3 is a magnetic field detection unit, 4 is a control module, 5 is the first excitation power supply, 6 is the second excitation power supply, 7 is the third excitation power supply, 8 is an external low-temperature superconducting magnet, 21 is the first internal magnet, 22 is the second internal magnet, and 41 is a single-pane coil. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] The embodiments of this application are described below with reference to the accompanying drawings.

[0032] like Figure 1 As shown, this application provides a device for eliminating shielding current-induced stress, comprising: a shielding coil 1 coaxially disposed on the outer side of the axial end of the target inserted magnet 2, which is wound with superconducting wire, for generating a vertical magnetic field component at the axial end of the target inserted magnet 2 with the same direction as the vertical magnetic field component of the target inserted magnet 2's own field; a third excitation power supply 7 electrically connected to the shielding coil 1 for providing an adjustable DC excitation current to the shielding coil 1; a magnetic field detection unit 3 disposed on the side of the shielding coil 1 near the target inserted magnet 2 for real-time monitoring of the total vertical magnetic field component at its location; and a control module 4 signal-connected to the third excitation power supply 7 and the magnetic field detection unit 3, for controlling the third excitation power supply 7 to dynamically adjust the magnitude of the DC excitation current applied to the shielding coil 1 in real time according to the operating stage of the target inserted magnet 2 and the external low-temperature superconducting magnet 8 and the monitored vertical magnetic field component, thereby further regulating the vertical magnetic field component of the shielding coil 1 acting on the end of the target inserted magnet 2, so as to reduce the shielding current in the edge region of the target inserted magnet and further suppress the concentrated stress at the edge of the inserted magnet.

[0033] The shielding coil 1 is made of low-temperature superconducting wire or high-temperature superconducting wire, and its operating temperature is the same as that of the high-temperature superconducting intercalation magnet.

[0034] In one illustrated embodiment, the low-temperature superconducting wire is selected from NbTi or Nb3Sn; the high-temperature superconducting wire is selected from ReBCO, Bi-2223, Bi-2212, MgB2 or iron-based superconductors.

[0035] Preferably, if the shielding coil 1 uses high-temperature superconducting tape, the width of the tape used is smaller than the width of the tape used in the target inserted magnet 2, so as to reduce the shielding current and induced stress of the shielding coil itself.

[0036] Preferably, the control module 4 performs phased dynamic closed-loop control on the third excitation power supply 7: First stage: When the target inserted magnet 2 is energized, the third excitation power supply 8 is controlled to start applying DC excitation current to the shielding coil 1, gradually increasing it to the preset value, so as to ensure that the shielding coil 1 has sufficient magnetic field adjustment capability before entering the second stage. Second stage: When the target inserted magnet 2 is maintained in its rated state and the external low-temperature superconducting magnet 8 is energized, the third excitation power supply 7 is controlled to gradually reduce the DC excitation current to ensure that the reduction of the vertical magnetic field generated by the shielding coil 1 at the end of the inserted magnet 2 is greater than the increase of the vertical magnetic field generated by the external low-temperature superconducting magnet 8 at this point, so that the vertical magnetic field at the end of the inserted magnet 2 shows a monotonically decreasing trend. Third stage: When both the target internal magnet 2 and the external low-temperature superconducting magnet 8 reach their rated values ​​and stabilize, control the output current of the third excitation power supply 7 to synchronously return to zero, so as to avoid additional energy consumption and heat generation of the shielding coil 1.

[0037] It should be noted that this application achieves phased dynamic closed-loop control through the above-mentioned dynamic excitation strategy, actively regulating the vertical magnetic field component acting on the axial end of the inserted magnet, so that it shows a downward trend as the external magnetic field rises, thereby inducing a reverse shielding current at the edge of the inserted magnet to counteract the initial shielding current and effectively alleviate the concentrated stress at the edge.

[0038] Preferably, the amplitude of the preset value in the first stage The calculation formula is:

[0039] in, For the preset compensation coefficient, ≥1.0, to ensure that the shielding coil has sufficient current regulation margin to counteract the rise of the magnetic field of the external magnet; The vertical magnetic field generated at the end of the intercalated magnet by a unit external low-temperature superconducting magnet current. The vertical magnetic field generated at the end of the inserted magnet by the unit shielded coil current. The rated operating current of the external low-temperature superconducting magnet is configured such that the positive and negative signs of the preset value are configured to make the vertical magnetic field component generated by the shielding coil at the end of the target inserted magnet have the same direction as the vertical magnetic field component of the target inserted magnet's own field.

[0040] Preferably, the control of the third excitation power supply to gradually reduce the DC excitation current is as follows: First, based on the change in current of the external low-temperature superconducting magnet Calculate the base adjustment amount :

[0041] in, The vertical magnetic field generated at the end of the intercalated magnet by a unit external low-temperature superconducting magnet current. The vertical magnetic field generated at the end of the inserted magnet by the unit shielded coil current; Subsequently, the total change in the vertical magnetic field was monitored in real time by the magnetic field detection unit. Generate feedback correction amount When detected When a negative feedback correction value is generated. To increase the rate of decrease in the shielding coil current; when detected At that time, feedback correction amount It is zero; Finally, calculate the actual amount of adjustment implemented. .

[0042] It should be noted that in the second stage, the control module uses a "model feedforward + feedback correction" strategy to calculate the adjustment amount of the third excitation power supply output current. Basic adjustment amount. It is inherently negative, when detected When the vertical magnetic field does not show a downward trend, a negative feedback correction value is generated. This increases the rate at which the shielding coil current decreases. Through this control logic, it is ensured that the change in the reverse magnetic field generated during the current reduction process can suppress the magnetic field increment of the external magnet, causing the vertical magnetic field at the end of the inserted magnet to exhibit an absolute decreasing trend.

[0043] like Figure 1 As shown, based on the above, this application provides a high-temperature superconducting intercalation magnet, integrating a device for eliminating shielding current-induced stress and a first excitation power supply, as described above; wherein, The shielding coil 1 in the shielding current induced stress elimination device is coaxially arranged on the outer side of the axial end of the high-temperature superconducting intercalation magnet. The first excitation power supply 5 is electrically connected to the high-temperature superconducting intercalation magnet and signal-connected to the control module 4. It is used to provide the high-temperature superconducting intercalation magnet with an adjustable DC excitation current in both magnitude and direction. The output current is one of the detection signals of the control module 4.

[0044] like Figure 1 As shown, based on the above, this application provides a hybrid magnet system, including: a high-temperature superconducting intercalation magnet as described above, an external low-temperature superconducting magnet, and a second excitation power supply; The external low-temperature superconducting magnet 8 is coaxially sleeved on the outside of the high-temperature superconducting intercalation magnet without contacting it, and is used to provide a central magnetic field with the same direction as the magnetic field generated by the high-temperature superconducting intercalation magnet. The second excitation power supply 6 is electrically connected to the external cryogenic superconducting magnet 8 and to the control module signal 4. It is used to provide the external cryogenic superconducting magnet 8 with a DC excitation current whose magnitude and direction can be adjusted. The output current is used as one of the detection signals of the control module 4.

[0045] Preferably, the control module 4 acquires the output current signals of the first excitation power supply 5 and the second excitation power supply 6 in real time, and determines the operating stage of the magnet system based on the two output current signals: When the output current of the first excitation power supply is detected to rise and the output current of the second excitation power supply is zero, or when the output current of the first excitation power supply is detected to be at the rated value and the output current of the second excitation power supply is zero, it is determined to be the first stage. When the output current of the first excitation power supply is maintained at the rated value and the output current of the second excitation power supply rises, it is determined to be the second stage. When the output current of both the first excitation power supply and the second excitation power supply reaches the rated value, it is judged to be in the third stage.

[0046] Example like Figure 2 As shown, the target intercalation magnet 2 in this embodiment has a double-layer structure, including a first intercalation magnet 21 and a second intercalation magnet 22. The external cryogenic superconducting magnet 8 is wound with cryogenic superconducting wire and equipped with an independent second excitation power supply, capable of providing a central magnetic field strength of 20 T. Both the first intercalation magnet 21 and the second intercalation magnet 22 are stacked from double-pane coils wound with ReBCO high-temperature superconducting tape, connected in series and powered by the first excitation power supply with a rated current of 260 A, contributing 5 T and 11 T of central magnetic field respectively. The shielding coil 1 is coaxially positioned directly above (i.e., axially outside) the first intercalation magnet 21 and closely arranged with it to meet the requirements of a compact structure design; this shielding coil 1 is powered by an independent third excitation power supply to provide a precisely adjustable DC excitation current. Furthermore, a magnetic field detection unit is located near the axial end of the shielding coil 1 (not shown) to monitor the total vertical magnetic field component at this critical location in real time.

[0047] Figure 3 The dynamic control curve of the excitation current of the shielding coil by the control module is shown during the excitation process of the magnet system. The whole process is divided into three stages: 1) In the first stage ( (seconds), the inserted magnets 21 and 22 begin energizing at 0 seconds, until... Excitation is completed within seconds, with the central magnetic field reaching 16 T. During this period, the external cryogenic superconducting magnet 8 is not yet energized, and the control module controls the third excitation power supply to apply a DC excitation current in the first direction to the shielding coil 1. Specifically, the "first direction" is configured so that the vertical magnetic field component generated by the shielding coil 1 at the end of the inserted magnet is in the same direction as (i.e., superimposed in the same direction) the vertical magnetic field component of the inserted magnet itself. This current gradually increases over time, until... The preset value is reached in seconds, and the amplitude of this preset value is... In this embodiment, the amplitude is set to 200 A. It is based on the rated parameters of the external magnet and the preset compensation coefficient. ( =1.2) is calculated to pre-store sufficient magnetic field potential energy in the shielding coil, so as to pre-set the adjustment margin for the next stage.

[0048] 2) In the second stage ( (seconds), external cryogenic superconducting magnet 8 in Excitation begins in seconds, until Excitation is completed within seconds, with the central magnetic field increasing from 16 T to 36 T. During this period, the inserted magnet maintains its rated current, and the control module gradually reduces the excitation current of shielding coil 1 from 200 A to zero. Throughout this process, the control module maintains an active closed-loop control strategy of "model feedforward + feedback correction": first, it performs feedforward calculations based on the rate of change of the external magnet current and the pre-stored magnetic field coefficient to derive the basic adjustment amount. Simultaneously, the total change in the vertical magnetic field is monitored in real time. To calculate the feedback correction amount In the ideal simulation environment of this embodiment, due to the accuracy of the feedforward model, the basic adjustment is sufficient to meet the requirements. Under the condition that the feedback correction amount is obtained, The calculation is zero; however, in practical engineering applications, once detected... (For example, due to model errors or external disturbances), the control module will automatically generate a negative feedback correction value, which will be superimposed on the basic adjustment value, thereby forcing the correction current to decrease at a certain rate. Through the above logic, it is ensured that the total vertical magnetic field at the end of the interpolated magnet continuously decreases during this stage, regardless of whether the operating conditions are ideal or disturbed.

[0049] Figure 4A and Figure 4B This demonstrates the physical mechanism by which the excitation process of the shielded coil is controlled to eliminate induced stress according to embodiments of this application. Here, 41 represents the uppermost single-pane coil (i.e., the region with the strongest vertical magnetic field and the most concentrated stress) in the first intercalated magnet 21. Figure 4A As shown, in the first stage, the inserted magnet and the shielding coil 1 are synchronously energized. The inserted magnet generates an upward magnetic field. Its vertical magnetic field component at the single-disc coil 41 is denoted as The direction is outward (i.e., away from the magnet's axis). At this time, a first-direction current is applied to the shielding coil 1, which generates a vertical magnetic field at the single-panel coil 41. The current flows outwards in the same direction. As the excitation current increases, a shielding current is induced within the single-disc coil 41. It should be noted that although a magnetic field from the shielding coil is superimposed at this time, due to the magnetic field at this moment... The electromagnetic force is relatively small and has not yet reached its extreme value, so it will not produce large strain at this stage, nor will it damage the magnet structure.

[0050] like Figure 4B As shown, in the second stage, the external cryogenic superconducting magnet 8 is energized, generating an outward-directed vertical magnetic field increment at the single-pane coil 41. At this time, the excitation current of shielding coil 1 gradually decreases, and the outward magnetic field it generates... It weakens rapidly. In vector superposition, the decrease of an outward vector is equivalent to the superposition of a change in the vertical magnetic field directed inward. Because of the aforementioned closed-loop control strategy, it was ensured that... Therefore, the total change in the vertical magnetic field at point 41 of the single-disc coil... satisfy This means that although the external background field is increasing, the vertical magnetic field at the end of the inserted magnet is decreasing. According to Lenz's law, this decreasing magnetic field will induce a current in the single-panel coil 41 that is opposite in direction to the initial shielding current. (i.e., reverse shielding current), which cancels out the positive shielding current generated in the first stage, thereby significantly reducing the corresponding shielding current induced stress.

[0051] To verify the effectiveness of the proposed method, this application uses finite element simulation software to establish an electromagnetic-mechanical coupling model and performs numerical analysis on the electromagnetic field distribution and circumferential strain of the interpolated magnet in this embodiment. The simulation parameters and results are shown in Table 1.

[0052] Table 1 Main parameters for magnet simulation

[0053] During the simulation, the working conditions using the technical solution of this application (hereinafter referred to as "example working conditions") were compared with the original magnet working conditions without the technical solution (hereinafter referred to as "comparative working conditions").

[0054] 1) Comparison of electromagnetic and mechanical properties at key locations ( Figures 5A-5C ): Figure 5A The simulation results of the vertical magnetic field at the upper edge of the innermost turn of the single-pane coil 41 (i.e., the uppermost coil with the most concentrated stress) were compared between the working conditions of the embodiment and the comparative example. Figure 5B The current density distribution at this location is shown; Figure 5C The maximum overall circumferential strain of the single-pane coil 41 during the entire excitation process is given under two operating conditions. Figure 5A and Figure 5B As can be seen, in the comparative case, a large positive shielding current is consistently maintained at the upper edge of the innermost turn of the single-pane coil. In contrast, in the second stage of the embodiment case ( As the excitation current in the first direction of the shielding coil gradually decreases (equivalent to a superimposed change in the reverse magnetic field), the vertical magnetic field at the upper edge of the innermost turn of the single-pane coil shows a significant decreasing trend, causing the original induced shielding current to be gradually weakened, and eventually inducing a shielding current in the opposite direction. Further combining... Figure 5CAs can be seen, thanks to the aforementioned electromagnetic control, the maximum circumferential strain of the single-pane coil 41 during the excitation process is reduced from 0.420% in the comparative case to 0.229% in the embodiment case, representing a relative reduction of 45.48%. This result confirms that the scheme of this application can significantly suppress the peak circumferential strain of the coil.

[0055] 2) Comparison of circumferential stress distribution ( Figure 6 ): Figure 6 This paper presents the circumferential stress distribution contour maps under two working conditions at the moment when the single-disc coil 41 reaches its maximum circumferential strain. Figure 6 It can be seen that in the comparative example, significant stress concentration occurs in the upper edge region of the single-pane coil 41, with a peak positive circumferential stress of 637 MPa and a peak negative stress of -430 MPa. However, in the embodiment, the stress distribution inside the coil is significantly improved, with the peak positive circumferential stress reduced to 364 MPa and the peak negative stress reduced to -173 MPa. The results indicate that by adding a shielded coil and dynamically adjusting its excitation current, the concentrated stress at the coil edge can be effectively mitigated, significantly reducing the risk of localized plastic deformation or mechanical damage to the superconducting tape.

[0056] 3) Evaluation of the improvement effect of axial distribution ( Figure 7 To further evaluate the effect of the shielding coil on improving the stress of the first internal magnet 21, the strain generated by the 2nd, 5th, and 10th single-pane coils located at the end positions of the first internal magnet 21 during the excitation process was compared and analyzed under the conditions of the embodiment and the comparative example. The 2nd, 5th, and 10th single-pane coils are the 2nd, 5th, and 10th layers in the top-to-bottom arrangement of the first internal magnet 21, respectively. Figure 7 The strain comparison results of the above-mentioned single-disc coil under two operating conditions are presented. Figure 7 It can be seen that, under the operating conditions of the embodiment, the maximum circumferential strain of the No. 2 single-coil coil significantly decreased from 0.418% to 0.288%, a reduction of 31.100%; the strain of the No. 5 single-coil coil decreased from 0.375% to 0.327%, a reduction of 12.800%; and the strain of the No. 10 single-coil coil decreased from 0.286% to 0.267%, a reduction of 6.643%. These results indicate that the coils closer to the axial end of the inserted magnet bear greater circumferential strain. By setting a shielded coil and reasonably controlling its excitation process, the strain level in the end region of the inserted magnet can be effectively reduced, and the improvement effect on the strain of the single-coil coils near the end is more significant, which helps to further reduce the risk of local plastic deformation and quenching of the magnet.

[0057] 4) Safety assessment of the shielding coil itself ( Figure 8 ): Figure 8 This demonstrates the variation of the maximum circumferential strain of the shielded coil body over time during excitation. Figure 8 It can be seen that in the first stage ( Inside the shielding coil, although a preset current flows, the background field it experiences is relatively small, resulting in extremely low circumferential strain. As the external cryogenic superconducting magnet begins excitation in the second stage, the circumferential strain of the shielding coil gradually increases, reaching a peak of 0.095% at the end of this stage. This peak value is far below the critical strain threshold of typical high-temperature superconducting tapes (usually >0.4%) and significantly less than the strain level of the interpolated magnet. This indicates that the shielding coil's mechanical safety is fully guaranteed when performing stress relief tasks, without introducing new structural failure risks, demonstrating good engineering feasibility.

[0058] 5) Impact assessment on the central magnetic field ( Figure 9 ): Figure 9 This presents simulation results of the change in central magnetic field strength over time under two operating conditions after excitation is completed (steady-state phase). Figure 9 It can be seen that the central magnetic field intensity curves of the embodiment and the comparative embodiment highly overlap, with the maximum difference under steady state being only 0.00067 T. This result indicates that this application effectively suppresses the concentrated stress in the superconducting magnet while having minimal impact on the central magnetic field performance of the magnet, thus helping to ensure the stable operation of the magnet system.

[0059] In this application, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0060] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0061] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0062] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0063] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0064] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0065] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0066] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A stress relief device for shielding current induced stress, characterized by, include: A shielding coil, coaxially positioned on the outside of the axial end of the target insert magnet, is made of superconducting wire and is used to generate a vertical magnetic field component at the axial end of the target insert magnet that is in the same direction as the vertical magnetic field component of the target insert magnet's own field. A third excitation power supply electrically connected to the shielding coil is used to provide an adjustable DC excitation current to the shielding coil; A magnetic field detection unit is located on the side of the shielded coil near the target inserted magnet, and is used to monitor the total vertical magnetic field component at the location in real time. The control module is connected to the third excitation power supply and the magnetic field detection unit respectively. It is used to control the third excitation power supply to dynamically adjust the magnitude of the DC excitation current applied to the shielding coil in real time according to the operating stage of the target inserted magnet and the external low temperature superconducting magnet and the monitored vertical magnetic field component. This further regulates the vertical magnetic field component of the shielding coil acting on the end of the target inserted magnet, so as to reduce the shielding current in the edge region of the target inserted magnet.

2. The cancellation device of claim 1, wherein, If the shielding coil uses high-temperature superconducting tape, the width of the tape used is smaller than the width of the tape used for the target inserted magnet.

3. The cancellation device of claim 1, wherein, The control module performs phased dynamic closed-loop control of the third excitation power supply: First stage: When the target inserted magnet is energized, the third excitation power supply is controlled to start applying DC excitation current to the shielding coil, gradually increasing it to the preset value, so as to ensure that the shielding coil has sufficient magnetic field regulation capability before entering the second stage. Second stage: When the target inserted magnet is maintained in its rated state and the external low-temperature superconducting magnet is energized, the DC excitation current of the third excitation power supply is gradually reduced to ensure that the reduction of the vertical magnetic field generated by the shielding coil at the end of the inserted magnet is greater than the increase of the vertical magnetic field generated by the external low-temperature superconducting magnet at this point, so that the vertical magnetic field at the end of the inserted magnet shows a monotonically decreasing trend. The third stage: When both the target internal magnet and the external low-temperature superconducting magnet reach their rated values ​​and stabilize, the output current of the third excitation power supply is controlled to return to zero synchronously, so as to avoid additional energy consumption and heat generation of the shielding coil.

4. The elimination device as described in claim 3, characterized in that, The magnitude of the preset value of the first stage The calculation formula is: wherein, is a preset compensation factor, ≥ 1.0, is the vertical magnetic field generated by the unit external cryogenic superconducting magnet current at the end of the interpolated magnet, is the vertical magnetic field generated by the unit shield coil current at the end of the interpolated magnet, is the rated operating current of the external cryogenic superconducting magnet, the positive or negative sign of the preset value is configured to make the vertical magnetic field component generated by the shield coil at the target interpolated magnet end and the target interpolated magnet self-field vertical magnetic field component in the same direction.

5. The cancellation device of claim 3, wherein, The control of the third excitation power supply to gradually reduce the DC excitation current is as follows: First, the basic adjustment amount is calculated based on the amount of change in the current of the external low-temperature superconducting magnet : in, The vertical magnetic field generated at the end of the intercalated magnet by a unit external low-temperature superconducting magnet current. The vertical magnetic field generated at the end of the inserted magnet by the unit shielded coil current; Subsequently, the total change in the vertical magnetic field was monitored in real time by the magnetic field detection unit. Generate feedback correction amount When detected When a negative feedback correction value is generated. To increase the rate of decrease in the shielding coil current; when detected At that time, feedback correction amount Zero; Finally, calculate the actual amount of adjustment implemented. .

6. A high-temperature superconducting intercalation magnet, characterized in that, It integrates a shielding current-induced stress elimination device and a first excitation power supply as described in any one of claims 1 to 5; wherein, In the device for eliminating current-induced stress in shielding, the shielding coil is coaxially positioned on the outer side of the axial end of the high-temperature superconducting intercalation magnet. The first excitation power supply is electrically connected to the high-temperature superconducting intercalation magnet and signal-connected to the control module. It is used to provide the high-temperature superconducting intercalation magnet with an adjustable DC excitation current in both magnitude and direction. The output current serves as one of the detection signals of the control module.

7. A hybrid magnet system, characterized in that, include: The high-temperature superconducting intercalation magnet, the external low-temperature superconducting magnet, and the second excitation power supply as described in claim 6; An external low-temperature superconducting magnet is coaxially sleeved on the outside of a high-temperature superconducting intercalation magnet without making contact, and is used to provide a central magnetic field with the same direction as the magnetic field generated by the high-temperature superconducting intercalation magnet. The second excitation power supply is electrically connected to the external cryogenic superconducting magnet and signal-connected to the control module. It is used to provide the external cryogenic superconducting magnet with an adjustable DC excitation current in both magnitude and direction, and the output current serves as one of the detection signals of the control module.

8. The magnet system as claimed in claim 7, characterized in that, The control module acquires the output current signals of the first excitation power supply and the second excitation power supply in real time, and determines the operating stage of the magnet system based on the two output current signals: When the output current of the first excitation power supply is detected to rise and the output current of the second excitation power supply is zero, or when the output current of the first excitation power supply is detected to be at the rated value and the output current of the second excitation power supply is zero, it is determined to be the first stage. When the output current of the first excitation power supply is maintained at the rated value and the output current of the second excitation power supply rises, it is determined to be the second stage. When the output current of both the first excitation power supply and the second excitation power supply reaches the rated value, it is judged to be in the third stage.

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