Superconducting magnet device

Abstract

The present invention addresses the problem of coping with misconnection of polarities of a superconducting coil and a power supply thereof. A superconducting magnet device (10) is provided with: a superconducting coil (12); a quench protection circuit (22) that is connected in parallel with the superconducting coil (12) and allows a current in a single direction; and an excitation power supply (24) that is connected to the superconducting coil (12) with a regular polarity determined so that current flows in a single direction in the quench protection circuit (22) when the superconducting coil (12) is quench, and that excites the superconducting coil (12). The excitation power source (24) is configured so as to detect an erroneous connection with the superconducting coil (12) when the excitation power source (24) is connected to the superconducting coil (12) with a polarity opposite to a normal polarity.

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2023-094082 filed on June 7, 2023. The entire contents of the Japanese Patent Application are incorporated herein by reference.

[0002] The invention relates to a superconducting magnet device. Background Art

[0003] Undesirable phenomena that may occur during the operation of a superconducting magnet device include thermal runaway (quench) of the superconducting coil. If a quench occurs, the superconducting coil changes from superconducting to normal conducting, generating resistance inside the coil. A large Joule heat may be generated by the large current flowing through the coil in the previous superconducting state. It may also cause a rise in the voltage inside the coil and discharge caused by it. In addition, due to the imbalance of instantaneous current when a quench occurs, a large electromagnetic force may act on the superconducting coil. Eddy currents may also be generated in the conductor arranged near the coil, causing electromagnetic force to act. The heat, discharge, and electromagnetic force that may be generated in this way may cause damage to the superconducting coil and its surrounding structures or equipment.

[0004] Typically, a protection circuit is provided in a superconducting magnet apparatus to protect the superconducting coil when a superconducting coil is quenched. An example of a protection circuit is an example in which a pair of diodes connected in parallel with opposite polarities are connected in parallel to the superconducting coil. The protection circuit is typically placed in a cryogenic environment together with the superconducting coil and cooled to the same temperature.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2007-234689

[0006] As a result of repeated and in-depth research on the protection circuit of the superconducting magnet device, the inventors found the following problems. Diodes that ensure operation at ultra-low temperatures are more expensive than general diodes that do not do so. If the above pair of diodes is replaced with a single diode in the quench protection circuit, the number of diodes used is halved, which is conducive to low cost of the device. At this time, in the design of the superconducting magnet device, the direction of the current flowing in the superconducting coil in normal operation (i.e., in a state where the superconducting coil has not quenched) should be predetermined so that when a quench occurs, the current flows from the coil to the diode along its forward direction. It is expected that the superconducting coil and its power supply are connected with the correct polarity so that it can operate in this way.

[0007] However, the inventors have found that when manufacturing a superconducting magnet device or assembling it on site, when connecting the superconducting coils to the power supply, there is a risk of mistakenly connecting them with opposite polarities. If such a wrong connection is made, the current flows in the superconducting coil in the opposite direction to the correct direction during normal operation. As a result, when a quench occurs, the current from the superconducting coil to the diode tends to flow in the opposite direction of the diode. That is, as a result of the wrong connection, the operation of the quench protection circuit may be hindered. If the protection circuit does not operate, the risk of damage to the superconducting magnet device when a quench occurs as described above is unexpectedly increased. Summary of the invention

[0008] One of the exemplary purposes of an embodiment of the present invention is to cope with incorrect connection of the polarity of a superconducting coil to its power supply.

[0009] According to one embodiment of the present invention, a superconducting magnet device includes: a superconducting coil; a quench protection circuit connected in parallel with the superconducting coil and allowing a current in a single direction; and an excitation power supply connected to the superconducting coil with a regular polarity that determines that a current flows in a single direction in the quench protection circuit when a quench occurs in the superconducting coil, and excites the superconducting coil. The excitation power supply is configured to detect an incorrect connection with the superconducting coil when the superconducting coil is connected with a polarity opposite to the regular polarity.

[0010] According to one embodiment of the present invention, a superconducting magnet device includes: a superconducting coil; a quench protection circuit connected in parallel with the superconducting coil and allowing current in a single direction; an excitation power supply connected to the superconducting coil with a regular polarity that determines that current flows in a single direction in the quench protection circuit when a quench occurs in the superconducting coil, and excites the superconducting coil; and a coil-side positive terminal and a coil-side negative terminal connected to the superconducting coil. The excitation power supply includes a power-side positive terminal connected to the coil-side positive terminal and a power-side negative terminal connected to the coil-side negative terminal. The coil-side positive terminal is configured to be unable to be connected to the power-side negative terminal, and the coil-side negative terminal is configured to be unable to be connected to the power-side positive terminal.

[0011] Effects of the Invention

[0012] According to the present invention, it is possible to cope with incorrect connection of the polarity between the superconducting coil and its power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram schematically showing a superconducting magnet device according to an embodiment.

[0014] Figure 2 It is a diagram schematically showing a superconducting magnet device according to an embodiment.

[0015] Figure 3 This is a diagram schematically showing an incorrect connection of an excitation power supply in a superconducting magnet device according to an embodiment.

[0016] Figure 4 middle, Figure 4 (a) to Figure 4 (c) is related to the embodiment and is a diagram schematically showing an example of electrical connection between an excitation power supply and a superconducting coil.

[0017] Figure 5 middle, Figure 5 (a) to Figure 5 (c) is related to the embodiment and is a diagram schematically showing another example of the electrical connection between the excitation power supply and the superconducting coil.

[0018] Figure 6 middle, Figure 6 (a) and Figure 6 (b) is related to the embodiment and is a diagram schematically showing an example of measures for incorrect connection between the excitation power supply and the superconducting coil.

[0019] In the figure: 10-superconducting magnet device, 12-superconducting coil, 22-quench protection circuit, 24-excitation power supply, 40a-coil side positive terminal, 40b-coil side negative terminal, 42a-power side positive terminal, 42b-power side negative terminal, 44-detector, 50-sensor. DETAILED DESCRIPTION

[0020] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of the method for implementing the present invention. The same or equivalent components, parts, and processes in the description and the accompanying drawings are marked with the same symbols, and repeated descriptions are appropriately omitted. In each of the accompanying drawings, for the convenience of description, the scale and shape of each part are appropriately set, and unless otherwise specifically stated, they are not to be interpreted as limiting. The implementation methods are examples and do not limit the scope of the present invention in any way. All the features or their combinations described in the implementation methods are not necessarily the essential contents of the invention.

[0021] Figure 1 and Figure 2 1 is a diagram schematically showing a superconducting magnet device 10 according to an embodiment. The superconducting magnet device 10 is mounted on, for example, a single crystal pulling device, an NMR (Nuclear Magnetic Resonance) system, an MRI (Magnetic Resonance Imaging) system, an accelerator such as a cyclotron, a high energy physics system such as a nuclear fusion system, or is mounted on a high magnetic field utilizing device as a magnetic field source of other high magnetic field utilizing devices (not shown), thereby being able to generate a high magnetic field required by the device.

[0022] The superconducting magnet device 10 includes a superconducting coil 12 , a vacuum container 14 , a cryogenic refrigerator 16 , a heat shield 18 , a current introduction line 20 , a quench protection circuit 22 , and an excitation power supply 24 .

[0023] The superconducting coil 12 is arranged in the vacuum container 14, and is configured to generate a strong magnetic field by passing electricity in a state of being cooled to an ultra-low temperature below the superconducting transition temperature. The superconducting coil 12 can be a known superconducting coil (for example, a so-called low-temperature superconducting coil). The superconducting coil 12 is connected to an excitation power supply 24 arranged outside the vacuum container 14 through a current introduction line 20. The excitation current is supplied from the excitation power supply 24 to the superconducting coil 12 through the current introduction line 20. Thus, the superconducting magnet device 10 can generate a strong magnetic field.

[0024] The vacuum container 14 is an insulated vacuum container that provides an ultra-low temperature vacuum environment suitable for setting the superconducting coil 12 to a superconducting state, and is also called a cryostat. Typically, the vacuum container 14 has a cylindrical shape, or a cylindrical shape with a hollow portion in the center. Therefore, the vacuum container 14 has a substantially flat circular or annular top plate 14a and a bottom plate 14b and a cylindrical side wall (a cylindrical outer peripheral wall, or a coaxially arranged cylindrical outer peripheral wall and inner peripheral wall) connecting them. The ultra-low temperature refrigerator 16 can be arranged on the top plate 14a of the vacuum container 14. The vacuum container 14 is formed of, for example, a metal material such as stainless steel or other suitable high-strength materials to withstand ambient pressure (ambient pressure) (e.g., atmospheric pressure).

[0025] The cryogenic refrigerator 16 is configured to cool the heat shield 18 and the quench protection circuit 22 to a first cooling temperature, and to cool the superconducting coil 12 to a second cooling temperature lower than the first cooling temperature. In this embodiment, the cryogenic refrigerator 16 is a two-stage Gifford-McMahon (GM) refrigerator, and is provided with a first cooling stage 16a and a second cooling stage 16b. The first cooling stage 16a and the second cooling stage 16b are respectively arranged to surround the first expansion space and the second expansion space in the cryogenic refrigerator 16, and are formed of, for example, a metal material such as copper or other material having a high thermal conductivity. The first cooling temperature may be in a temperature range of about 20K to about 100K, for example, in a temperature range of about 30K to about 50K, and the second cooling temperature may be in a temperature range of about 3K to about 20K, for example, may be about 4K.

[0026] The heat shield 18 is arranged in the vacuum container 14 in a manner of surrounding the superconducting coil 12. The heat shield 18 is formed of, for example, a metal material such as copper or other material having a high thermal conductivity. The heat shield 18 is directly mounted on the first cooling stage 16a of the ultra-low temperature refrigerator 16 and is thermally connected to the first cooling stage 16a. Alternatively, the heat shield 18 can also be mounted on the first cooling stage 16a via a flexible or rigid heat transfer component. During the operation of the superconducting magnet device 10, the heat shield 18 is cooled to a first cooling temperature by the first cooling stage 16a. The heat shield 18 can thermally protect the low-temperature parts of the second cooling stage 16b of the ultra-low temperature refrigerator 16, the superconducting coil 12, etc., which are arranged inside the heat shield 18 and cooled to a low temperature lower than that of the heat shield 18, from the influence of radiant heat from the vacuum container 14.

[0027] The superconducting coil 12 is thermally connected to the second cooling stage 16b via a heat transfer component 26. The heat transfer component 26 is formed of, for example, a metal material such as copper or other material having a high thermal conductivity, and connects the superconducting coil 12 to the second cooling stage 16b. The heat transfer component 26 may be a rigid component that rigidly connects the superconducting coil 12 and the second cooling stage 16b, or may be flexible and connects the superconducting coil 12 and the second cooling stage 16b in a manner that allows relative displacement of the superconducting coil 12 and the second cooling stage 16b. Alternatively, the superconducting coil 12 may be directly mounted on the second cooling stage 16b and thermally connected to the second cooling stage 16b. During operation of the superconducting magnet device 10, the superconducting coil 12 is cooled to the second cooling temperature by the second cooling stage 16b.

[0028] The current introduction wire 20 includes an external wiring 20a, a feedthrough 20b, an outer current lead 20c, and an inner current lead 20d, and forms a current path from the excitation power supply 24 to the superconducting coil 12. Typically, one current introduction wire 20 on the positive side and one current introduction wire 20 on the negative side are provided.

[0029] The external wiring 20a disposed outside the vacuum container 14 connects the excitation power supply 24 to a feedthrough 20b provided on the wall of the vacuum container 14. The external wiring 20a may be an appropriate power supply cable. The feedthrough 20b is an airtight terminal for introducing current into the vacuum container 14, and connects the external wiring 20a to the internal wiring (i.e., the outer current lead 20c and the inner current lead 20d) in the vacuum container 14. The current introduction wire 20 can penetrate the wall of the vacuum container 14 while maintaining the airtightness of the vacuum container 14 through the feedthrough 20b.

[0030] The outer current lead portion 20c is arranged outside the heat shield 18 in the vacuum container 14, and connects the feed-through portion 20b to the inner current lead portion 20d. The outer current lead portion 20c is formed of a metal material with excellent conductivity, such as pure copper such as oxygen-free copper. The end of the outer current lead portion 20c connected to the inner current lead portion 20d is thermally connected to the heat shield 18. The end of the outer current lead portion 20c is fixed to the heat shield 18, or is connected to the heat shield 18 via an appropriate heat transfer component and is cooled to the first cooling temperature in the same manner as the heat shield 18. Among them, the outer current lead portion 20c is in a state of being electrically insulated from the heat shield 18. For example, the outer current lead portion 20c can be installed on the fixed portion in a manner such that an insulating material (for example, an insulating resin material sheet) is sandwiched between the fixed portion and the heat shield 18 or the heat transfer component.

[0031] The inner current lead portion 20d is arranged inside the heat shield 18 and connects the outer current lead portion 20c to the superconducting coil 12. The inner current lead portion 20d may include a first terminal 20d1, a second terminal 20d2, and a high-temperature superconducting current lead 20d3 connecting the two terminals. The first terminal 20d1 is connected to the outer current lead portion 20c, and the second terminal 20d2 is connected to the superconducting coil 12. The first terminal 20d1 is thermally connected to the heat shield 18 and is cooled to a first cooling temperature in the same manner as the heat shield 18. The second terminal 20d2 is cooled to a second cooling temperature in the same manner as the superconducting coil 12.

[0032] The high-temperature superconducting current lead 20d3 can be formed of, for example, a copper oxide superconductor or other high-temperature superconducting materials. The material of such a high-temperature superconducting current lead has thermal insulation. Therefore, compared with the case where the inner current lead portion 20d is made of metal, the heat that can be transferred from the quench protection circuit 22 to the superconducting coil 12 using the inner current lead portion 20d as a heat transfer path can be reduced. This can reduce the heat load on the second cooling stage 16b of the cryogenic refrigerator 16 and can contribute to good cooling of the superconducting coil 12.

[0033] The quench protection circuit 22 is connected in parallel with the superconducting coil 12. One end of the quench protection circuit 22 is connected to one (for example, the positive electrode side) current introduction line 20, and the other end is connected to the other (for example, the negative electrode side) current introduction line 20, thereby being connected in parallel with the superconducting coil 12. For example, the quench protection circuit 22 and the current introduction line 20 can be connected using a busbar formed of a metal material with excellent conductivity such as copper.

[0034] The quench protection circuit 22 can generate heat by being energized, and may include a normal linear (i.e., following Ohm's law) resistor element, or may include a nonlinear resistor. The nonlinear resistor may have a nonlinear characteristic that the resistance value increases when a small voltage is applied to the nonlinear resistor, and the resistance value decreases when a large voltage is applied to the nonlinear resistor (the nonlinear resistor may have a first resistance value when a voltage applied to the nonlinear resistor is a first value, and may have a second resistance value less than the first resistance value when a voltage applied to the nonlinear resistor is a second value greater than the first value).

[0035] The nonlinear resistor may be, for example, a rectifying element such as a diode or a thyristor. In this embodiment, as an example, the quench protection circuit 22 includes a diode 28. Thus, alternatively, the nonlinear resistor may be a varistor. In addition, the quench protection circuit 22 may include both a linear resistor and a nonlinear resistor, and, for example, they may be connected in series.

[0036] Unlike a typical conventional quench protection circuit including a pair of diodes connected in parallel with opposite polarities, in this embodiment, the quench protection circuit 22 allows current in only one direction, which corresponds to the forward direction of the diode 28, and blocks current in the reverse direction. Such a quench protection circuit 22 contributes to cost reduction of the superconducting magnet device 10 compared to the conventional quench protection circuit. This is because the number of diodes used in the quench protection circuit 22 can be halved by using a single diode 28 instead of a pair of diodes. A diode that is guaranteed to operate at ultra-low temperatures is more expensive than a general-purpose diode that is not such a diode, so reducing the number of diodes used greatly contributes to cost reduction.

[0037] As described above, the quench protection circuit 22 is cooled to a higher cooling temperature than the superconducting coil 12 during the operation of the superconducting coil 12. The quench protection circuit 22 can be thermally connected to the first cooling stage 16a of the cryogenic refrigerator 16 and cooled to the first cooling temperature. Figure 2 , for convenience, the first portion cooled to the first cooling temperature is surrounded by a dotted line 30, and the second portion cooled to the second cooling temperature is surrounded by a dotted line 32. As shown in the example in the figure, the quench protection circuit 22 can be connected between the outer current lead portions 20c, for example, it can be provided at a portion cooled to the first cooling temperature such as the heat shield 18. The quench protection circuit 22 can be connected to the superconducting coil 12 via the inner current lead portion 20d (i.e., the high-temperature superconducting current lead 20d3).

[0038] If the temperature rise of the superconducting coil 12 accompanying the quench is large, the time required for re-cooling for repair may be extended, that is, the downtime of the superconducting magnet device 10 may be increased. In the existing design, the protection circuit of the superconducting coil is usually cooled to the same temperature as the superconducting coil. In this embodiment, the quench protection circuit 22 is cooled to a higher cooling temperature than the superconducting coil 12, so it can be re-cooled in a shorter time compared with the existing design in which the protection circuit is cooled to the same temperature as the superconducting coil (that is, the second cooling temperature). The time required to repair the superconducting magnet device 10 from the quench can be shortened.

[0039] The quench protection circuit 22 is cooled by the first cooling stage 16a of the cryogenic refrigerator 16, so that the heat generated by the quench protection circuit 22 can be effectively removed. This is because the refrigeration capacity of the first stage of the cryogenic refrigerator 16 is generally larger (for example, several dozen times) than that of the second stage, and is relatively sufficient. This is also conducive to shortening the time required to repair the superconducting magnet device 10 from a quench.

[0040] When the quench protection circuit 22 is connected to the superconducting coil 12 via the high-temperature superconducting current lead 20d3, the amount of heat that can be transferred from the quench protection circuit 22 to the superconducting coil 12 using the inner current lead 20d as a heat transfer path can be reduced compared to the case where the inner current lead 20d is made of metal. This can reduce the heat load on the second cooling stage 16b of the cryogenic refrigerator 16 and contribute to good cooling of the superconducting coil 12.

[0041] like Figure 2 As shown, the superconducting coil 12 may have a structure in which it is divided into a plurality of (for example, N, where N is an arbitrary natural number) superconducting coil portions 12a_1 to 12a_N and these superconducting coil portions 12a are connected in series. The quench protection circuit 22 includes a plurality of diodes 28, and the plurality of diodes 28 are respectively connected in parallel to the corresponding superconducting coil portions 12a among the plurality of superconducting coil portions 12a. The high-temperature superconducting current lead 20d3 connects each diode 28 and the corresponding superconducting coil portion 12a. Compared with a coil structure that is not divided, such a coil division structure can reduce the voltage applied to both ends of the superconducting coil 12 when a quench occurs, and is therefore particularly advantageous when the superconducting coil 12 is a large superconducting coil.

[0042] In addition, the superconducting magnet device 10 may include a plurality of superconducting coils 12, and in this case, a quench protection circuit 22 may be provided for each superconducting coil 12. That is, a plurality of quench protection circuits 22 may be provided, and each quench protection circuit 22 may be connected in parallel to a corresponding superconducting coil 12 among the plurality of superconducting coils 12. The plurality of superconducting coils 12 may be divided into a plurality of superconducting coil portions 12a, respectively.

[0043] In this embodiment, in the design of the superconducting magnet device 10, the direction of the current flowing from the excitation power source 24 to the superconducting coil 12 is predetermined so that the current does not flow to the quench protection circuit 22 during the normal operation of the superconducting magnet device 10. The direction of the current supplied from the excitation power source 24 to the superconducting coil 12 is fixed to a single direction. The excitation power source 24 with the current direction fixed in this way is sometimes used in several applications of the superconducting magnet device 10, such as a single crystal pulling device. For example, Figure 2 As shown by arrow 34 in FIG. 1 , the direction of the current flowing from excitation power supply 24 to superconducting coil 12 is opposite to diode 28 of quench protection circuit 22 , so the current is blocked by diode 28 and does not flow to quench protection circuit 22 .

[0044] On the other hand, when a quench occurs during the operation of the superconducting coil 12, the electrical connection between the excitation power supply 24 and the superconducting coil 12 is cut off, and the current from the superconducting coil 12 flows to the quench protection circuit 22. Figure 2 As shown by the arrow 36 in the figure, the direction of the current corresponds to the forward direction of the diode 28. Thus, the current can flow from the superconducting coil 12 to the quench protection circuit 22, and at least a part of the electromagnetic energy stored in the superconducting coil 12 can be converted into heat and consumed by the quench protection circuit 22. In this way, by extracting energy from the superconducting coil 12 by the quench protection circuit 22, the superconducting coil 12 can be protected when a quench occurs. By reducing the energy of the superconducting coil 12, damage to the superconducting coil 12 and its surroundings that may occur due to the reduction can be prevented or reduced.

[0045] Figure 3 1 is a diagram schematically showing an erroneous connection of the excitation power supply 24 in the superconducting magnet device 10 according to the embodiment. As described at the beginning of this specification, the present inventors have found that when the superconducting coil 12 and the excitation power supply 24 are connected during the manufacturing of the superconducting magnet device 10 or during the assembly at the site of use, there is a risk that they may be connected with opposite polarities by mistake. Figure 3 In FIG. 1 , the excitation power source 24 connected in the reverse direction is illustrated by a dotted line.

[0046] If such an incorrect connection is made, Figure 3 As shown by the arrow 38a in FIG. 1 , in normal operation, the current flows in the superconducting coil 12 in the direction opposite to the correct direction. Figure 3 As shown by the arrow 38b in the figure, the current from the superconducting coil 12 to the diode tends to flow in the reverse direction of the diode. That is, as a result of the incorrect connection, the operation of the quench protection circuit 22 may be hindered. If the quench protection circuit 22 does not operate, the risk of damage to the superconducting magnet device 10 when a quench occurs as described above is undesirably increased.

[0047] Therefore, in this specification, several solutions to the problem of incorrect connection of the polarity between the superconducting coil 12 and the excitation power supply 24 are proposed below.

[0048] Figure 4 (a) to Figure 4 (c) is related to the embodiment and is a diagram schematically showing an example of electrical connection between the excitation power supply 24 and the superconducting coil 12. Figure 4 (a) shows the state before the excitation power supply 24 is connected to the superconducting coil 12. Figure 4 (b) shows a state where the excitation power source 24 and the superconducting coil 12 are correctly connected with the correct polarity. Figure 4 (c) shows a state where the superconducting coil 12 is mistakenly connected to the excitation power supply 24 with a polarity opposite to the proper polarity.

[0049] As described above, the superconducting coil 12 is connected to the excitation power supply 24 via the current introduction wire 20. Figure 4 As shown in (a), the current introduction wire 20 on the positive side has a coil side positive terminal 40a at the end, and the current introduction wire 20 on the negative side has a coil side negative terminal 40b at the end, and these coil side terminals are connected to the superconducting coil 12 through the current introduction wire 20. The excitation power supply 24 has a power supply side positive terminal 42a connected to the coil side positive terminal 40a and a power supply side negative terminal 42b connected to the coil side negative terminal 40b. The terminals on the coil side and the power supply side are combined in a manner that can be electrically connected, for example, by fastening, crimping or other appropriate fixing methods.

[0050] The coil side positive terminal 40a is configured to be unable to be connected to the power side negative terminal 42b, and the coil side negative terminal 40b is configured to be unable to be connected to the power side positive terminal 42a. As an example of such an unconnectable structure, the coil side positive terminal 40a and the coil side negative terminal 40b may have different shapes, and the power side positive terminal 42a and the power side negative terminal 42b may also have different shapes corresponding to the difference in the shapes of the coil side positive terminal 40a and the coil side negative terminal 40b.

[0051] For example, as shown in the figure, the coil side positive terminal 40a and the coil side negative terminal 40b may have mutually different terminal lengths, and correspondingly, the power supply side positive terminal 42a and the power supply side negative terminal 42b may also have mutually different terminal lengths. In other words, the coil side positive terminal 40a and the power supply side positive terminal 42a may have the same terminal length, the coil side negative terminal 40b and the power supply side negative terminal 42b may have the same terminal length, and the terminal length on the positive side may be different from the terminal length on the negative side.

[0052] Therefore, if Figure 4As shown in (b), due to the conformity of the terminal shapes, the coil side positive terminal 40a can be connected to the power side positive terminal 42a, and the coil side negative terminal 40b can be connected to the power side negative terminal 42b. In this way, the excitation power supply 24 and the superconducting coil 12 can be correctly connected with the regular polarity.

[0053] On the other hand, Figure 4 As shown in (c), when the operator attempts to mistakenly connect the excitation power supply 24 to the superconducting coil 12 with a polarity opposite to the normal polarity, the terminals on the coil side and the power supply side cannot be connected to each other on at least one of the positive and negative sides (the positive side in the example shown) due to the mismatch of the terminal shapes.

[0054] In this way, it is possible to physically prevent the excitation power supply 24 from being incorrectly connected to the current introduction wire 20 (or even the superconducting coil 12). As a result, it is possible to avoid the risk of the quench protection circuit 22 not operating as a result of the incorrect connection. Instead of a pair of diodes connected in opposite directions to each other, a single diode 28 can be used for the quench protection circuit 22, and the cost of the superconducting magnet device 10 can be reduced.

[0055] Figure 5 (a) to Figure 5 (c) is related to the embodiment and is a diagram schematically showing another example of the electrical connection between the excitation power supply 24 and the superconducting coil 12. Figure 5 (a) shows the state before the excitation power supply 24 is connected to the superconducting coil 12. Figure 5 (b) shows a state where the excitation power source 24 and the superconducting coil 12 are correctly connected with the correct polarity. Figure 5 (c) shows a state where the superconducting coil 12 is mistakenly connected to the excitation power supply 24 with a polarity opposite to the proper polarity.

[0056] As in the above example, a set of coil side terminals (coil side positive terminal 40a and coil side negative terminal 40b) are provided on the current introduction wire 20, and a set of power supply side terminals (power supply side positive terminal 42a and power supply side negative terminal 42b) are provided on the excitation power supply 24. The coil side positive terminal 40a is connected to the power supply side positive terminal 42a, and the coil side negative terminal 40b is connected to the power supply side negative terminal 42b, so that the superconducting coil 12 is connected to the excitation power supply 24 through the current introduction wire 20. In this example, by inserting the coil side terminal into the power supply side terminal, these terminals can be connected to each other.

[0057] As shown in the figure, a detector 44 is provided, which generates a detection signal S1 indicating whether a group of coil side terminals and a group of power supply side terminals are connected with a regular polarity or connected with an opposite polarity. In this example, the detector 44 can be configured to generate the detection signal S1 when the coil side terminals and the power supply side terminals are connected with a regular polarity, and on the other hand, not generate the detection signal S1 when they are connected with a polarity opposite to the regular polarity.

[0058] As an example, the detector 44 may include: a detection signal generator 44a, which is provided at a power supply side terminal (in the example shown in the figure, the power supply side negative terminal 42b); and an operating unit 44b, which is provided at a coil side terminal (in the example shown in the figure, the coil side negative terminal 40b) and operates the detection signal generator 44a. The detection signal generator 44a may be configured to generate a detection signal S1 when operated by the operating unit 44b, for example, it may be a button that generates the detection signal S1 in this way. The operating unit 44b may be configured not to contact the detection signal generator 44a when the terminals on the power supply side and the coil side are not connected, and to contact and operate the detection signal generator 44a when the two terminals are connected, for example, it may be a washer installed on the terminal. In addition, the detection signal generator 44a may also be provided at the coil side terminal, and the operating unit 44b may also be provided at the power supply side terminal.

[0059] The excitation power supply 24 is configured to detect an incorrect connection based on the detection signal S1. The excitation power supply 24 is connected to the detector 44 to receive the detection signal S1 from the detector 44 (specifically, the detection signal generator 44a). Therefore, the excitation power supply 24 can receive the detection signal S1 from the detector 44 and detect an incorrect connection in response to the detection signal S1.

[0060] The excitation power supply 24 may have an interlock mechanism 46 built therein as a safety device. When the detection signal S1 indicates that the excitation power supply 24 and the superconducting coil 12 are correctly connected, the excitation power supply 24 may be configured to release the interlock mechanism 46 on the condition that the detection signal S1 is received. As such an interlock mechanism 46, a known interlock mechanism may be appropriately adopted. In this way, when the connection is correct, the excitation power supply 24 is allowed to supply power to the superconducting coil 12, while when the connection is incorrect, the interlock mechanism 46 can prohibit the power supply.

[0061] Furthermore, the excitation power source 24 may be configured to notify the operator visually, auditorily, or by other appropriate methods that an erroneous connection is detected or that an erroneous connection is not detected (ie, that the connection is correct).

[0062] In this example, if Figure 5As shown in (b), the coil side positive terminal 40a can be connected to the power side positive terminal 42a, and the coil side negative terminal 40b can be connected to the power side negative terminal 42b. At this time, the operating part 44b installed on the coil side negative terminal 40b contacts the detection signal generator 44a installed on the power side negative terminal 42b (that is, the washer presses the button) to generate a detection signal S1. The detection signal S1 is input from the detector 44 to the excitation power supply 24. At this time, the excitation power supply 24 releases the interlocking mechanism 46 according to the detection signal S1. In addition, the excitation power supply 24 can notify the operator that the excitation power supply 24 is correctly connected to the superconducting coil 12 according to the detection signal S1.

[0063] On the other hand, Figure 5 As shown in (c), when the operator mistakenly connects the excitation power supply 24 and the superconducting coil 12 with the polarity opposite to the proper polarity, the detection signal generator 44a of the power supply side negative terminal 42b is not operated because the operation unit 44b is not provided at the coil side positive terminal 40a. As a result, the detector 44 does not generate the detection signal S1. At this time, the excitation power supply 24 maintains the interlocking performed by the interlocking mechanism 46.

[0064] In this way, it is possible to detect the incorrect connection between the excitation power supply 24 and the current introduction line 20 (or even the superconducting coil 12). Thus, even if the connection is incorrect, it is possible to correctly reconnect. The risk that the quench protection circuit 22 does not operate as a result of the incorrect connection can be avoided. Instead of a pair of diodes connected in opposite directions to each other, a single diode 28 can be used for the quench protection circuit 22, and the cost of the superconducting magnet device 10 can be reduced.

[0065] In addition, the detector 44 is not limited to the contact type detector as described above, and may be a non-contact type detector such as an optical type.

[0066] Instead of or in addition to the wrong connection measure using the detector 44, the way the current changes when the excitation power source 24 excites the superconducting coil 12 can be studied, thereby detecting the wrong connection between the excitation power source 24 and the superconducting coil 12. Here, the excitation of the superconducting coil 12 is a part of the preparation stage for the normal operation of the superconducting magnet device 10 to generate a magnetic field, and refers to the step of increasing the coil current supplied from the excitation power source 24 to the superconducting coil 12 from zero to a predetermined current (for example, the rated current of the superconducting coil 12). An example of such wrong connection detection is described below.

[0067] Figure 6 (a) and Figure 6 (b) is related to the embodiment and is a diagram schematically showing an example of a measure for incorrect connection between the excitation power supply 24 and the superconducting coil 12. Figure 6(a) shows a state where the excitation power source 24 and the superconducting coil 12 are correctly connected with the correct polarity. Figure 6 (b) shows a state where the superconducting coil 12 is mistakenly connected to the excitation power supply 24 with a polarity opposite to the proper polarity.

[0068] The excitation power supply 24 can be configured to control the current increase rate when exciting the superconducting coil 12 so that the induced electromotive force generated in the superconducting coil 12 or a part thereof (e.g., the superconducting coil portion 12a) due to the current increase rate exceeds the threshold voltage of the rectifying element (e.g., the diode 28).

[0069] In other words, the excitation power supply 24 may be configured to control the current increase rate (dI / dt) of the superconducting coil 12 during the excitation process so as to satisfy the following equation.

[0070] Vf<L(dI / dt)

[0071] Here, Vf represents a threshold voltage of a rectifying element, and L represents an inductance of superconducting coil 12 or a part thereof connected in parallel with the rectifying element.

[0072] like Figure 6 As shown in (a), when the excitation power supply 24 and the superconducting coil 12 are connected with the correct polarity, the current I from the excitation power supply 24 flows to the superconducting coil 12 during the process of exciting the superconducting coil 12 by the excitation power supply 24. The direction of the current I is equivalent to the reverse direction of the diode 28, so the current I does not flow to the diode 28.

[0073] On the other hand, Figure 6 As shown in (b), when the excitation power supply 24 and the superconducting coil 12 are mistakenly connected with the polarity opposite to the normal polarity, the current I from the excitation power supply 24 flows not only to the superconducting coil 12 but also to the diode 28 during the process of exciting the superconducting coil 12 by the excitation power supply 24. This is because, as described above, the excitation power supply 24 is controlled so that the induced electromotive force L (dI / dt) generated in the superconducting coil 12 exceeds the threshold voltage Vf of the diode 28. At this time, the direction of the current I is equivalent to the forward direction of the diode 28, so the diode 28 is energized (opened) by the induced electromotive force L (dI / dt), and the forward current flows to the diode 28 (in Figure 6 (b) indicated by arrow 48).

[0074] Therefore, a sensor 50 for detecting the power supply to the rectifier element (the diode 28 in this example) can be provided in the superconducting magnet device 10. For example, the sensor 50 can be a current sensor for measuring the current flowing to the rectifier element, for example, a non-contact current sensor. Alternatively, the sensor 50 can also be a magnetic sensor that is arranged near the rectifier element and measures the magnetic flux. The magnetic sensor can detect the magnetic flux generated when the current flows to the rectifier element. Alternatively, the sensor 50 can also be a temperature sensor for measuring the temperature of the rectifier element. The temperature sensor can detect the temperature rise of the rectifier element generated when the current flows to the rectifier element.

[0075] The excitation power supply 24 may be configured to control the current increase speed dI / dt so that the induced electromotive force L (dI / dt) exceeds the threshold voltage Vf of the rectifying element, and detect the wrong connection based on the output of the sensor 50. For example, the excitation power supply 24 may receive the output from the sensor 50 and compare the output of the sensor 50 with a certain threshold value. The excitation power supply 24 may determine that the excitation power supply 24 and the superconducting coil 12 are correctly connected when the output of the sensor 50 is lower than the threshold value, and determine that the excitation power supply 24 and the superconducting coil 12 are wrongly connected when the output of the sensor 50 exceeds the threshold value. The threshold value used for determination can be appropriately set based on the designer's experience or based on the designer's experiments, simulation tests, etc.

[0076] Thus, by setting the current increase rate in the process of exciting the superconducting coil 12 by the excitation power supply 24 as described above, it is possible to detect the incorrect connection between the excitation power supply 24 and the current introduction line 20 (or even the superconducting coil 12). Thus, even if the connection is incorrect for a moment, it is possible to reconnect correctly. The risk that the quench protection circuit 22 does not operate as a result of the incorrect connection can be avoided. Instead of a pair of diodes connected in opposite directions to each other, a single diode 28 can be used for the quench protection circuit 22, and the cost of the superconducting magnet device 10 can be reduced.

[0077] In addition, for convenience, Figure 6 (a) and Figure 6 (b) shows a superconducting coil 12 and a rectifying element (diode 28) connected in parallel therewith. Figures 1 to 3 As described above, a plurality of superconducting coils 12 (or a plurality of superconducting coil portions 12a) and a plurality of corresponding rectifying elements may be provided in the superconducting magnet device 10. In this case, the above-mentioned wrong connection detection method can also be applied in the same manner. That is, the wrong connection can be detected based on whether or not at least one rectifying element among the plurality of rectifying elements is energized.

[0078] Instead of the sensor 50, the excitation power source 24 may be configured to measure the voltage across the excitation power source 24 and detect the incorrect connection based on the measured voltage across the excitation power source 24. When the excitation power source 24 and the superconducting coil 12 are connected with the correct polarity, the excitation power source 24 measures a voltage equivalent to the induced electromotive force L (dI / dt) as the voltage across the excitation power source 24 during the process of exciting the superconducting coil 12 by the excitation power source 24. On the other hand, when the excitation power source 24 and the superconducting coil 12 are incorrectly connected with the polarity opposite to the correct polarity, the voltage across the excitation power source 24 becomes the threshold voltage Vf of the diode 28.

[0079] Therefore, the threshold value for determination based on the voltage across the excitation power supply 24 can be predetermined to be greater than the threshold voltage Vf of the rectifying element and less than the induced electromotive force L (dI / dt). The excitation power supply 24 can measure the voltage across the excitation power supply 24 in the process of exciting the superconducting coil 12 by the excitation power supply 24, and compare the measured voltage across the excitation power supply 24 with the threshold value. The excitation power supply 24 can determine that the excitation power supply 24 and the superconducting coil 12 are correctly connected when the voltage across the excitation power supply 24 exceeds the threshold value, and determine that the excitation power supply 24 and the superconducting coil 12 are incorrectly connected when the voltage across the excitation power supply 24 is lower than the threshold value.

[0080] When a plurality of superconducting coils 12 (or a plurality of superconducting coil portions 12a) are provided, the threshold used for the determination may be greater than the sum of the threshold voltages of the corresponding plurality of rectifying elements (ΣVf, for example, N×Vf when N rectifying elements having the same threshold voltage are provided) and less than the sum of the induced electromotive forces (ΣL(dI / dt)).

[0081] The excitation power supply 24 may be configured to stop the excitation power supply 24 when the measured voltage across both ends is lower than the voltage lower limit. For example, the excitation power supply 24 may include an interlock mechanism 46 (see Figure 5 (a)), the interlock mechanism 46 can stop the excitation power supply 24 when the voltage across the excitation power supply 24 is lower than the voltage lower limit value.

[0082] At this time, the excitation power supply 24 can be configured to control the current increase speed dI / dt so that the induced electromotive force (L(dI / dt) or ΣL(dI / dt)) exceeds the voltage lower limit value, and measure the voltage across the excitation power supply 24, and detect the wrong connection based on the measured voltage across the two ends. The voltage lower limit value can be pre-set to exceed the threshold voltage (Vf or ΣVf) of the rectifier element.

[0083] In this way, when the excitation power source 24 is correctly connected to the superconducting coil 12, the voltage across the excitation power source 24 exceeds the voltage lower limit value, so the interlocking mechanism 46 does not work, and the superconducting coil 12 can be excited. On the other hand, in the case of an erroneous connection, the voltage across the excitation power source 24 is lower than the voltage lower limit value, so the interlocking mechanism 46 works, and the excitation of the superconducting coil 12 by the excitation power source 24 can be stopped.

[0084] In addition, depending on the type or design of the superconducting coil 12, the current increase rate is sometimes slow (or sometimes needs to be reduced) immediately after the excitation starts. In order to avoid misjudging this situation as an incorrect connection, the excitation power supply 24 can invalidate the voltage lower limit value (or interlock mechanism 46) when the current increase rate is lower than a certain level. In this case, the excitation power supply 24 can validate the voltage lower limit value (or interlock mechanism 46) at the stage where the current increase rate increases to a certain level.

[0085] In this way, it is also possible to detect the incorrect connection between the excitation power supply 24 and the current introduction line 20 (or even the superconducting coil 12). Therefore, even if the connection is incorrect, it is possible to correctly reconnect. The risk that the quench protection circuit 22 does not operate as a result of the incorrect connection can be avoided. Instead of a pair of diodes connected in opposite directions to each other, a single diode 28 can be used for the quench protection circuit 22, and the cost of the superconducting magnet device 10 can be reduced.

[0086] The present invention is described above based on the embodiments. Those skilled in the art should understand that the present invention is not limited to the above-mentioned embodiments, and various design changes can be made, and various modifications can be realized, and such modifications are also within the scope of the present invention. The various features described in conjunction with one embodiment can also be applied to other embodiments. The new embodiment generated by the combination has the effects of each of the combined embodiments.

[0087] In the above embodiment, the ultra-low temperature refrigerator 16 is described as a GM refrigerator, but the present invention is not limited thereto. In one embodiment, the ultra-low temperature refrigerator 16 may be a two-stage ultra-low temperature refrigerator of other forms such as a Solvay refrigerator, a Stirling refrigerator, or a pulse tube refrigerator having a first cooling stage 16a and a second cooling stage 16b.

[0088] exist Figure 1 In the figure, one cryogenic refrigerator 16 is shown as an example. However, if the superconducting coil 12 is a large superconducting coil, the superconducting magnet device 10 may include a plurality of cryogenic refrigerators 16 for cooling the same superconducting coil 12 as required.

[0089] In the above-mentioned embodiment, the superconducting magnet device 10 is configured as a so-called conduction cooling type that is directly cooled by the ultra-low temperature refrigerator 16, rather than an immersion cooling type in which the superconducting coil 12 is immersed in an ultra-low temperature liquid refrigerant such as liquid helium. However, the superconducting magnet device 10 may be an immersion cooling type. In this case, the superconducting coil 12 may be cooled by, for example, immersing it in an ultra-low temperature liquid such as liquid helium, and the quench protection circuit 22 may be cooled using a refrigerant having a higher boiling point than the superconducting coil 12 (for example, liquid nitrogen, etc.). In this way, the quench protection circuit 22 may be cooled to a higher cooling temperature than the superconducting coil 12 during the operation of the superconducting coil 12.

[0090] In the above embodiment, the quench protection circuit 22 is thermally connected to the first cooling stage 16a of the cryogenic refrigerator 16 and cooled to the first cooling temperature. However, the present invention is not limited thereto. The quench protection circuit 22 may be thermally connected to the second cooling stage 16b of the cryogenic refrigerator 16 and cooled to the second cooling temperature. Alternatively, the quench protection circuit 22 may be arranged in the surrounding environment outside the vacuum container 14 and set to the surrounding temperature (e.g., room temperature).

[0091] The present invention is described using specific sentences based on the implementation mode, but the implementation mode only shows one aspect of the principle and application of the present invention. In the implementation mode, there may be many variations and configuration changes without departing from the scope of the idea of ​​the present invention defined by the technical solution.

Claims

1. A superconducting magnet device, characterized in that: have: Superconducting coils; a quench protection circuit connected in parallel with the superconducting coil and allowing current flow in a single direction; and an excitation power supply connected to the superconducting coil with a normal polarity determined so that the current in the quench protection circuit flows in the single direction when the superconducting coil is quenched, and excites the superconducting coil, The excitation power supply is configured to detect an erroneous connection with the superconducting coil when the excitation power supply is connected to the superconducting coil with a polarity opposite to the normal polarity.

2. The superconducting magnet device according to claim 1, characterized in that: The quench protection circuit includes a rectifying element connected in parallel with the superconducting coil or a part thereof. The excitation power supply is configured to control a current increase rate when exciting the superconducting coil so that an induced electromotive force generated in the superconducting coil or the portion due to the current increase rate exceeds a threshold voltage of the rectifying element.

3. The superconducting magnet device according to claim 2, characterized in that: Also available: a sensor for detecting the energization of the rectifying element, The excitation power supply is configured to control the current increase speed so that the induced electromotive force exceeds a threshold voltage of the rectifying element, and detect the incorrect connection based on an output of the sensor.

4. The superconducting magnet device according to claim 2, characterized in that: The excitation power supply is configured to control the current increase speed so that the induced electromotive force exceeds a threshold voltage of the rectifying element, and to measure a voltage across both ends of the excitation power supply, and to detect the incorrect connection based on the measured voltage across both ends.

5. The superconducting magnet device according to claim 4, characterized in that: The excitation power supply is configured to stop the excitation power supply when the measured voltage between both ends is lower than a voltage lower limit value. The excitation power supply is configured to control the current increase speed so that the induced electromotive force exceeds the voltage lower limit value, and to measure the voltage across both ends of the excitation power supply, and to detect the incorrect connection based on the measured voltage across both ends. The voltage lower limit value is preset to exceed a threshold voltage of the rectifying element.

6. The superconducting magnet device according to any one of claims 1 to 5, characterized in that: have: a set of coil-side terminals connected to the superconducting coil, The excitation power supply includes a group of power supply side terminals connected to the group of coil side terminals. The superconducting magnet device further includes a detector that generates a detection signal indicating whether the set of coil-side terminals and the set of power-side terminals are connected with the normal polarity or with the reverse polarity. The excitation power supply is configured to detect the incorrect connection based on the detection signal.

7. A superconducting magnet device, characterized in that: have: Superconducting coils; a quench protection circuit connected in parallel with the superconducting coil and allowing current in a single direction; an excitation power supply connected to the superconducting coil with a regular polarity determined so that the current in the quench protection circuit flows in the single direction when the superconducting coil is quenched, and excites the superconducting coil; and The coil side positive terminal and the coil side negative terminal are connected to the superconducting coil, The excitation power supply includes a power supply side positive terminal connected to the coil side positive terminal and a power supply side negative terminal connected to the coil side negative terminal. The coil-side positive terminal is configured to be unable to be connected to the power-side negative terminal. The coil-side negative terminal is configured to be unable to be connected to the power-side positive terminal.

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