Superconducting magnet and magnetic resonance imaging apparatus

Abstract

The embodiments disclosed in this specification and accompanying drawings relate to superconducting magnets and magnetic resonance imaging apparatuses. Protection is provided for current leads used in the superconducting magnet. One embodiment of the superconducting magnet includes a superconducting coil, a permanent current switch or a first switch, at least one of an external power source and a load, current leads, a second switch, and a control device. The superconducting coil generates a static magnetic field. The permanent current switch is electrically connected to the superconducting coil, switching between a superconducting state and a normally conducting state. The first switch is electrically connected to the superconducting coil, mechanically or electrically opening and closing the circuit. An external power source supplies current to the superconducting coil. The load releases the magnetic energy of the superconducting coil. The current leads electrically connect the external power source, the load, or both the external power source and the load to the superconducting coil. The second switch is disposed between the external power source, the load, or both the external power source and the load and the superconducting coil. The second switch has a first state where the external power source, the load, or both the external power source and the load are electrically connected to the superconducting coil, and a second state where the electrical connection between the external power source, the load, or both the external power source and the load and the superconducting coil is disconnected. The control device switches the second switch between the first state and the second state.

Description

[0001] This application is based on and enjoys priority benefits from Japanese Patent Application 2025-060840 (filed on April 1, 2025) and Japanese Patent Application 2026-026740 (filed on February 20, 2026). This application incorporates the entire contents of those applications. Technical Field

[0002] The embodiments disclosed in this specification and accompanying drawings relate to superconducting magnets and magnetic resonance imaging (MRI) devices. Background Technology

[0003] An MRI device is an imaging device that uses high-frequency (RF) pulses of the Larmor frequency to excite the atomic spins of a subject placed in a static magnetic field, and performs a scan to collect magnetic resonance (MR) signals generated from the subject in conjunction with the excitation, and generates MR images based on the MR signals collected by the scan.

[0004] In MRI devices, there exists a device where the magnet that generates the static magnetic field is made of a superconducting magnet. The superconducting magnet houses a superconducting coil, which is conventionally cooled to extremely low temperatures by liquid helium. In the liquid helium-cooled superconducting coil, copper current leads are used, for example. These copper current leads are cooled by cryogenic helium gas, which is produced by the vaporization of liquid helium, thus enabling the conduction of currents, for example, up to several hundred amperes. Furthermore, the current leads are conductors used to electrically connect an external power source (i.e., a static magnetic field power source) or an external load, located in a region at room temperature, to the superconducting coil located in a region at extremely low temperatures.

[0005] In superconducting magnets that do not use liquid helium or use only a few liters of helium for cooling superconducting coils, high-temperature superconductors (HTS) with low thermal conductivity and high current carrying capacity are mostly used as current leads to suppress heat intrusion from the room temperature region into the superconducting coil. If an overcurrent is generated in the current lead or the temperature of the current lead rises, the current lead may burn out. Summary of the Invention

[0006] One of the problems to be solved by the superconducting magnets of the embodiments disclosed in this specification and the accompanying drawings is the protection of the current leads used in the superconducting magnets. However, the problems to be solved by the embodiments disclosed in this specification and the accompanying drawings are not limited to the above-mentioned problems. It is also possible to identify other problems as those corresponding to the effects of the various configurations shown in the various embodiments described below.

[0007] One embodiment of a superconducting magnet includes a superconducting coil, a permanent current switch or a first switch, at least one of an external power source and a load, a current lead, a second switch, and a control device. The superconducting coil generates a static magnetic field. The permanent current switch is electrically connected to the superconducting coil, switching between a superconducting state and a normally conducting state. The first switch is electrically connected to the superconducting coil, mechanically or electrically opening and closing the circuit. An external power source supplies current to the superconducting coil. The load releases the magnetic energy of the superconducting coil. The current lead electrically connects the external power source, the load, or both the external power source and the load to the superconducting coil. The second switch is disposed between the external power source, the load, or both the external power source and the load and the superconducting coil. The second switch has a first state where the external power source, the load, or both the external power source and the load are electrically connected to the superconducting coil, and a second state where the electrical connection between the external power source, the load, or both the external power source and the load and the superconducting coil is disconnected. The control device switches the second switch between the first and second states.

[0008] The superconducting magnet and magnetic resonance imaging device constructed as described above can protect the current leads used in the superconducting magnet. Attached Figure Description

[0009] Figure 1 This is a block diagram illustrating an example of the overall configuration of an MRI apparatus according to an embodiment.

[0010] Figure 2 This is a block diagram illustrating the internal structure of a comparative example of a superconducting magnet.

[0011] Figure 3 This is a block diagram illustrating an example of the internal structure of a superconducting magnet according to the first embodiment.

[0012] Figure 4 (A) is a diagram illustrating the concept of the excitation mode in the superconducting magnet of the first embodiment. Figure 4 (B) is a diagram illustrating the concept of the current lead protection mode in the superconducting magnet of the first embodiment. Figure 4 (C) is a diagram illustrating the concept of the permanent current mode in the superconducting magnet of the first embodiment.

[0013] Figure 5 This is a flowchart illustrating an example of the operation of the MRI apparatus according to the first embodiment.

[0014] Figure 6 (A) is a diagram illustrating the concept of the permanent current mode in the superconducting magnet of the first embodiment. Figure 6 (B) is a diagram illustrating the concept of the demagnetization mode in the superconducting magnet of the first embodiment. Figure 6 (C) is a diagram illustrating the concept of the current lead protection mode in the superconducting magnet of the first embodiment.

[0015] Figure 7 This is a block diagram illustrating an example of the internal structure of a superconducting magnet according to a variation of the first embodiment 1.

[0016] Figure 8 This is a flowchart illustrating an example of the operation of the MRI device according to a variation of the first embodiment 1.

[0017] Figure 9 This is a block diagram illustrating an example of the internal structure of a superconducting magnet in a modified example 2 of the first embodiment.

[0018] Figure 10 This is a flowchart illustrating an example of the operation of the MRI device in a variation of the first embodiment, Example 2.

[0019] Figure 11 This is a block diagram illustrating the internal structure of a superconducting magnet in a variation of the first embodiment, Example 3.

[0020] Figure 12 This is a flowchart illustrating an example of the operation of the MRI device of Modification 3 of the first embodiment.

[0021] Figure 13 This is a block diagram illustrating an example of the internal structure of a superconducting magnet according to the second embodiment.

[0022] Figure 14 (A) is a diagram illustrating the concept of the excitation mode in the superconducting magnet of the second embodiment. Figure 14 (B) is a diagram illustrating the concept of the current lead protection mode in the superconducting magnet of the second embodiment. Figure 14 (C) is a diagram illustrating the concept of the permanent current mode in the superconducting magnet of the second embodiment.

[0023] Figure 15 This is a flowchart illustrating an example of the operation of the MRI device according to the second embodiment.

[0024] Figure 16 Figures (A) to (D) of 16 illustrate the switch that transitions from the excitation mode to the permanent current mode in the superconducting magnet of the second embodiment.

[0025] Figure 17 (A) is a diagram illustrating the concept of the permanent current mode in the superconducting magnet of the second embodiment. Figure 17 (B) is a diagram illustrating the concept of demagnetization mode in the superconducting magnet of the second embodiment. Figure 17 (C) is a diagram illustrating the concept of the current lead protection mode in the superconducting magnet of the second embodiment. Detailed Implementation

[0026] Hereinafter, the superconducting magnet 10 and the MRI apparatus 1 according to the embodiments will be described based on the accompanying drawings. In each figure, the same elements are labeled with the same symbols, and repeated descriptions are omitted. Furthermore, the MRI apparatus 1 equipped with the superconducting magnet 10 is shown below, but the superconducting magnet 10 of the embodiments can also be applied to apparatuses other than MRI apparatuses such as NMR apparatuses.

[0027] (Overall structure of an MRI device) Figure 1 This is a block diagram illustrating an example of the overall configuration of an MRI apparatus 1. The MRI apparatus 1 includes a stand 100, a control cabinet 300, a control console 400, and an examination bed 500. Typically, the stand 100 and examination bed 500 are located in the imaging room where the magnetic field is generated, the control cabinet 300 is located in the machinery room, and the control console 400 is located in the user's operating room. The control console 400 can also be located remotely within or outside the hospital via a network.

[0028] The mounting device 100 includes a superconducting magnet 10, a gradient magnetic field coil 11, and a whole-body RF coil (hereinafter referred to as WB coil) 12. These components are housed in a cylindrical shell.

[0029] The superconducting magnet 10 is generally cylindrical in shape and generates a static magnetic field in the imaging region within the bore of the patient, which is then placed as the subject P. The bore refers to the examination space inside the cylinder of the superconducting magnet 10. The superconducting magnet 10 contains a superconducting coil 21 (see reference). Figure 3 The superconducting coil 21 is a coil wound with superconducting wire. It is a superconducting magnet that is cooled to a temperature that makes it superconducting and can stably generate a static magnetic field without supplying current from outside the magnet. The superconducting magnet 10 can be a superconducting magnet immersed in liquid helium or other refrigerants, or it can be a thermosiphon-type superconducting coil that cools the superconducting coil 21 by circulating refrigerant in a tube, or it can be a conduction-cooled superconducting magnet that is cooled almost without using refrigerant through a heat transfer path from a refrigerator. In addition, the superconducting wire used in the superconducting magnet can be any type, including low-temperature superconducting wires such as niobium-titanium and niobium-tin, copper oxide superconducting materials (REBCO), Bi-based materials (Bi-2212, Bi-2223, etc.), and high-temperature superconducting wires such as MgB2.

[0030] It can also be installed as an emergency power supply device capable of demagnetizing the static magnetic field in emergency situations such as quenching of the superconducting coil, and as an uninterruptible power supply (UPS) device that operates during power outages 274 (see reference). Figure 9 (Details regarding the superconducting magnet 10 will be discussed later.) Furthermore, quenching loss refers to the phenomenon where superconducting materials, such as superconducting coils, transition from a superconducting state to a normally conducting state.

[0031] The gradient magnetic field coil 11 is generally cylindrical and is fixed inside the superconducting magnet 10 for generating a static magnetic field in the radial direction of the cylindrical shape. The gradient magnetic field coil 11 receives a current supply from the gradient magnetic field power supply 31 to generate a gradient magnetic field. The gradient magnetic field coil 11 includes coils that generate magnetic fields corresponding to the X-axis, Y-axis, and Z-axis, which are orthogonal to each other. Each coil for each axis receives a current supply from the gradient magnetic field power supply 31, and the magnetic fields corresponding to the X-axis, Y-axis, and Z-axis are superimposed on the static magnetic field to generate a gradient magnetic field.

[0032] Here, the Z-axis direction is the direction set along the magnetic flux of the static magnetic field generated by the superconducting magnet 10, and is the same as the direction of the long side of the top plate 51. The Y-axis direction is a perpendicular direction orthogonal to the Z-axis direction, and is perpendicular to the top plate 51. The X-axis direction is a direction orthogonal to both the Z-axis and Y-axis, and is the same as the direction of the short side of the top plate 51.

[0033] The WB coil 12 is roughly cylindrical in shape and is an RF coil fixed inside the gradient magnetic field coil 11 in a manner that surrounds the subject P. The WB coil 12 sends the RF pulse transmitted from the transmitter 32 to the subject P and receives the MR signal emitted from the subject P by the excitation of hydrogen nuclei.

[0034] In addition to the WB coil 12, the MRI device 1 may also include a local coil 20. The local coil 20 is an RF coil disposed close to the subject P, receiving the MR signal emitted from the subject P at a position close to the subject P. The local coil 20 can also transmit RF pulses transmitted from the transmitter 32 to the subject P. The local coil 20 has a connection point with the head, chest (e.g., [missing information]). Figure 1 Various types of imaging techniques are used to examine the subject P, including the spine, lower limbs, and whole body.

[0035] The control cabinet 300 includes a gradient magnetic field power supply 31, a transmitter 32, a receiver 33, and a sequence controller 34.

[0036] Under the control of the sequence controller 34, the gradient magnetic field power supply 31 supplies current to the gradient magnetic field coil 11 to generate gradient magnetic fields corresponding to the X-axis, Y-axis and Z-axis.

[0037] Based on instructions from the sequence controller 34, the transmitter 32 generates a Larmor band RF pulse train as an RF transmission wave and outputs it to the RF coil to excite the subject P.

[0038] The receiver 33 performs analog-to-digital (AD) conversion on the MR signal received by the RF coil and outputs the digitized MR signal, i.e., raw data, to the sequence controller 34.

[0039] Under the control of the console 400, the sequence controller 34 drives the gradient magnetic field power supply 31, the transmitter 32, and the receiver 33 respectively, thereby performing a scan of the subject P. The sequence controller 34 receives raw data via the receiver 33 and sends the raw data to the console 400.

[0040] The sequence controller 34 includes processing circuitry (not shown). The processing circuitry of the sequence controller 34 may be composed of hardware such as a processor that executes a prescribed program, an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit).

[0041] The examination bed device 500 includes an examination bed body 50 and a top plate 51. The examination bed body 50 is capable of moving the top plate 51 in the vertical and horizontal directions, so that the subject P placed on the top plate 51 is moved to a predetermined height and into the hole.

[0042] The console 400 includes a processing circuit 41, a storage circuit 42, an input interface 43, a network interface 44, and a display 45. The console 400 is an image processing device composed of a computer.

[0043] The processing circuit 41 provides unified control over the entire MRI device 1. The processing circuit 41 is a processor that performs various functions by reading and executing various processing programs stored in the storage circuit 42 or directly incorporated into the processing circuit 41.

[0044] Storage circuit 42 is a recording medium that can be read by a processor, such as RAM (Random Access Memory), flash memory, hard disk, or optical disk. Storage circuit 42 can also be a portable medium such as a USB (Universal Serial Bus) memory or a DVD (Digital Versatile Disk). Storage circuit 42 stores various information and data. In addition, storage circuit 42 stores various programs executed by the processor of processing circuit 41 and the data required for program execution.

[0045] Input interface 43 includes a user-operable input device and input circuitry for processing signals from the input device. Input devices may include, for example, a trackball, switch, mouse, keyboard, touchpad for input via a touch-scanning surface, touchscreen integrating the display and touchpad, contactless input devices using optical sensors, and voice input devices. When the user operates the input device, the input circuitry generates a signal corresponding to that operation and outputs it to processing circuitry 41.

[0046] Network interface 44 is equipped with various information communication protocols corresponding to the network configuration. Network interface 44 performs communication control according to various protocols, and communicates with various devices connected to the network via wired or wireless means to exchange various information and data.

[0047] Display 45 is, for example, a liquid crystal display, an OLED (Organic Light Emitting Diode) display panel, a plasma display panel, or an organic EL (Electro Luminescence) panel. Display 45 displays various information and images under the control of processing circuit 41. Furthermore, display 45 is a display device, and may also function as an input device (GUI).

[0048] Through these components, the console 400 controls the entire MRI apparatus 1. Specifically, the processing circuit 41 receives instructions related to imaging conditions and various other information from users such as examination technicians via the input interface 43. Then, the processing circuit 41 instructs the sequence controller 34 to perform a scan based on the input imaging conditions. In addition, the processing circuit 41 reconstructs MR images based on the raw data sent from the sequence controller 34. The generated MR images are displayed on the display 45 and stored in the storage circuit 42.

[0049] As mentioned earlier, in superconducting magnets, to suppress heat intrusion from the room temperature region into the superconducting coil, current leads made of high-temperature superconductors with low thermal conductivity and high current carrying capacity are used, for example. If an overcurrent is generated in the current lead or the temperature of the current lead rises, the current lead may burn out.

[0050] here, Figure 2 This is a block diagram illustrating the internal structure of a comparative example of a superconducting magnet. In this comparative example, a diode, serving as a protective element, is connected in parallel with the current lead of the superconductor. Therefore, when the current lead transitions to a high-resistance state due to the temperature rise of the superconducting magnet, the current flowing through the current lead bypasses through the diode, thereby preventing the current lead from burning out.

[0051] However, if the diode is connected in parallel with the current lead, it is assumed that the amount of heat intrusion from the diode into the extremely low temperature region will increase, and the cooled components such as the superconducting coil may not reach the desired temperature. In addition, at low temperatures, the diode's forward voltage increases, so there is a time required before current flows to the diode, which may not prevent the current lead from burning out.

[0052] Therefore, the superconducting magnet 10 of the embodiment suppresses heat intrusion from the outside into the extremely low temperature region and protects the current leads by controlling the current to cut off the current flowing through the current leads.

[0053] (First Implementation) Figure 3 This is a block diagram illustrating an example of the internal structure of the superconducting magnet 10 according to the first embodiment. The MRI apparatus 1 includes a superconducting magnet 10, a cooling container 103 housing the superconducting magnet 10, a vacuum container 102 housing the cooling container 103, and a refrigerator 101 mounted on the vacuum container 102. The refrigerator 101 is, for example, a two-stage refrigerator, having a first cooling stage and a second cooling stage 104 with a temperature lower than the first cooling stage. For example, the temperature of the first cooling stage is approximately 40 Kelvin, and the temperature of the second cooling stage is approximately 4 Kelvin. The cooling container 103 is, for example, made of an aluminum heat radiation shielding plate, also referred to as a radiation shielding component.

[0054] The superconducting magnet 10 includes a superconducting coil 21, a protection diode section 22, a permanent current switch 23, current leads 24a and 24b, a second switch 261, an external power supply / load section 27, and a control device 28. Furthermore, the external power supply / load section 27 refers to "an external power supply, a load, or both an external power supply and a load".

[0055] In addition, Figure 3 The diagram shows the case where two current leads 24a and 24b are connected to each end of the superconducting coil 21. The following explanation focuses on the case of two current leads 24a and 24b, but the number of current leads is not limited. One or more can be connected, or only one end of the superconducting coil 21 can be connected, or different numbers can be connected to one end of the superconducting coil 21.

[0056] The superconducting coil 21, the protection diode section 22, and the permanent current switch 23 are integrated within a vacuum container 102, referred to as a cryostat, to be cooled to extremely low temperatures. Two current leads 24a and 24b can be disposed inside the vacuum container 102 and connected to the cooling container 103, either inside or outside the cooling container 103, but are preferably disposed inside the cooling container 103. The temperatures of the two current leads 24a and 24b decrease in the portion closer to the superconducting coil than the portion farther away from the superconducting coil.

[0057] in addition, Figure 3 This is an equivalent circuit diagram showing the electrical connections of the superconducting magnet 10. The superconducting coil 21 generates a static magnetic field. The superconducting coil 21 is electrically connected to the external power supply / load unit 27 via two current leads 24a and 24b.

[0058] exist Figure 3 The diagram schematically shows a superconducting coil 21, but the superconducting coil 21 can also be composed of multiple superconducting coils. When the superconducting coil 21 is composed of multiple superconducting coils, the superconducting coils can be electrically connected in series, in parallel, or in a combination of series and parallel connections.

[0059] The permanent current switch 23 is connected in parallel with the superconducting coil 21, that is, electrically connected to both the current input terminal 211 and the current output terminal 212 of the superconducting coil 21. Additionally, the permanent current switch 23 is electrically connected in parallel with the external power supply / load unit 27. The permanent current switch 23 can be a first switch that mechanically or electrically switches the connection of an electrical circuit. The first switch can be a mechanical switch that connects and disconnects current, or it can be a semiconductor switch.

[0060] The permanent current switch 23 switches between a superconducting state (closed-circuit state) and a normally conducting state (open-circuit state). The permanent current switch 23 is configured, for example, to include a superconducting component and a heater 231 disposed close to the superconducting component. When the heater 231 is off, the permanent current switch 23 is in a closed-circuit state, and the superconducting component remains in a superconducting state. When the heater 231 is on, the superconducting component becomes normally conducting, and therefore, the permanent current switch 23 is in an open-circuit state. Furthermore, the permanent current switch 23, configured with a superconducting component and a heater 231 disposed close to the superconducting component, functions as a switch depending on the presence or absence of resistance; even in the open-circuit state, the two ends of the permanent current switch 23 are electrically connected.

[0061] The control device 28 is composed of hardware such as a processor, FPGA, or ASIC that executes a predetermined program. The control device 28 controls the switching between the superconducting state (closed-circuit state) and the normally conducting state (open-circuit state) of the permanent current switch 23. Additionally, the control device 28 performs control related to the opening and closing of the first switch. Specifically, the control device 28 controls the switching of the heater 231 on and off; when on, the heater 231 is heated.

[0062] The protection diode section 22 is electrically connected in parallel with the superconducting coil 21 and the permanent current switch 23 to protect the superconducting coil 21 and the permanent current switch 23. The protection diode section 22 may include, for example, at least one set of diodes 221 and 222 arranged bidirectionally. By bidirectionally arranging the set of diodes 221 and 222, the superconducting coil 21 and the permanent current switch 23 can be protected during both the excitation and demagnetization processes, and also in the event of an unexpected quench in the superconducting coil or the permanent current switch.

[0063] Here, the excitation process refers to the process of generating a magnetic field by allowing current supplied by the static magnetic field power source to flow through the superconducting coil 21, and the demagnetization process refers to the process of releasing (i.e., consuming) the magnetic energy of the superconducting coil 21 by allowing current to flow through a load (i.e., demagnetizing load), thereby reducing the magnetic field generated by the superconducting coil 21. During the demagnetization process, the static magnetic field power source can be electrically connected to the superconducting coil 21 or it can be disconnected. Furthermore, the protection diode section 22 can be composed of a resistor or a combination of a resistor and a diode.

[0064] The external power supply / load unit 27 is electrically connected to two current leads 24a and 24b. As described above, the external power supply / load unit 27 is configured to include at least one of a static magnetic field power supply 271 and a load 272. The static magnetic field power supply 271 supplies current to the superconducting coil 21 during the excitation process (i.e., excitation mode). During the demagnetization process (i.e., demagnetization mode), the load releases (i.e., consumes) the magnetic energy of the superconducting coil 21, reducing the magnetic field generated by the superconducting coil 21. In the load, for example, a resistor or diode is used to convert electrical energy into heat energy.

[0065] The second switch 261 is electrically connected to the superconducting coil 21. The second switch 261 is disposed between the external power supply / load unit 27 and at least one current lead 24a or 24b, switching the current between the external power supply / load unit 27 and the superconducting coil 21 on and off. The second switch 261 has a first state in which the external power supply / load unit 27 is electrically connected to the superconducting coil 21, and a second state in which the electrical connection between the external power supply / load unit 27 and the superconducting coil 21 is disconnected. Furthermore, the first state is also referred to as the closed-circuit state, and the second state as the open-circuit state.

[0066] The second switch 261 mechanically or electrically switches the connection of the electrical circuit. The second switch 261 can be a mechanical switch that connects and disconnects current, or it can be a semiconductor switch, but a solid-state relay (SSR) with semiconductor switching elements is preferred. An SSR is a contactless relay, capable of stable operation even in the magnetic field of a photography studio. However, generally speaking, compared to mechanical relays, SSRs have higher on-resistance when current is flowing, thus tending to overheat; therefore, a heat-dissipating structure is preferred.

[0067] Therefore, the SSR can be configured, for example, to contact the metal vacuum container 102. Thus, the heat generated in the SSR is conducted to the vacuum container 102 and efficiently de-heated. Alternatively, a heat sink with at least one fin can be configured adjacent to the SSR. The heat sink facilitates the release of heat generated in the SSR. In this way, by thermally connecting the vacuum container 102, the heat sink, and the SSR, efficient heat de-heating is achieved.

[0068] In addition, only one second switch 261 needs to be installed. Figure 3 In this configuration, one is provided between the external power supply / load section 27 and the current lead 24a, but it can also be provided at both ends of the external power supply / load section 27.

[0069] Two current leads 24a and 24b electrically connect the external power supply / load section 27 to the superconducting coil 21. One of the two current leads 24a and 24b is located between one end of the superconducting coil 21 and one end of the external power supply / load section 27. The other of the two current leads 24a and 24b is located between the other end of the superconducting coil 21 and the other end of the external power supply / load section 27. Typically, the temperature of the portion of the current leads 24a and 24b closer to the superconducting coil 21 is lower than the temperature of the portion farther from the superconducting coil 21.

[0070] The current leads 24a and 24b are preferably made of a material that is conductive and has low thermal conductivity. For example, the current leads 24a and 24b are made of high-temperature superconducting materials such as MgB2, REBCO, Bi-based materials, or phosphorus deoxidized copper.

[0071] In a first embodiment, the MRI apparatus 1 includes at least one temperature sensor 25a and 25b for measuring the temperature of at least one current lead 24a and 24b. The temperature of the current leads 24a and 24b is an indicator related to the temperature of the current leads.

[0072] exist Figure 3In this design, temperature sensors 25a and 25b are respectively installed on each of the two current leads 24a and 24b. However, it is also possible to have only one temperature sensor on either of the two current leads 24a and 24b, or to equip multiple temperature sensors 25a and 25b on the current leads 24a and 24b. The temperature sensors can also be configured at both ends of each current lead. If two temperature sensors are configured at both ends of each current lead 24a and 24b, i.e., for each current lead, the high and low temperatures of the current leads 24a and 24b can be measured, thus obtaining temperature-related parameters of the current leads with higher accuracy.

[0073] Figure 4 (A) ~ Figure 4 (C) is a diagram illustrating the concept of three operating modes in the superconducting magnet 10. Figure 4 (A) is a diagram illustrating an example of operation in the excitation mode. The excitation mode refers to the operation mode in which current is supplied to the superconducting magnet 10 (i.e., the non-operating superconducting coil 21) by connecting it to the static magnetic field power supply 271, thereby causing the superconducting magnet 10 to generate a static magnetic field of a specified intensity.

[0074] In excitation mode, the heater 231 of the permanent current switch 23 is turned on by the control device 28. As a result, the permanent current switch 23 becomes normally conducting (open circuit). In excitation mode, the excitation current supplied from the static magnetic field power supply 271 flows in the current loop of current lead 24a, superconducting coil 21, and current lead 24b. When the excitation current gradually increases from zero to reach the rated value, the system switches from excitation mode to permanent current mode.

[0075] Reference Figure 5 Flowcharts and Figure 4 (B) illustrates the operation example of the current lead protection mode during the excitation process.

[0076] In step ST1, the control device 28 acquires the temperatures of the two current leads 24a and 24b. Furthermore, the temperatures of the two current leads 24a and 24b are monitored for a predetermined time or continuously, enabling determinations related to the temperatures of the two current leads 24a and 24b in steps ST2, ST6, and ST8.

[0077] In step ST2, the control device 28 determines, for example, whether the higher of the two current leads 24a and 24b, i.e., the maximum temperature Tmax, is below the specified closed-circuit condition temperature Tb. The closed-circuit condition temperature Tb refers to the temperature at which the circuit cut off to protect the current leads is reopened, i.e., the second switch 261 is closed. The closed-circuit condition temperature Tb is an example of a first condition value related to the opening and closing of the second switch. Furthermore, the first condition value can be any temperature-related condition value; it can be a temperature-related condition value or a condition value related to the amount of temperature change. If the maximum temperature Tmax > the closed-circuit condition temperature Tb (i.e., "NO"), the process proceeds to step ST1. Furthermore, in step ST1, the superconducting coil 21 is not energized. If the maximum temperature Tmax ≦ the closed-circuit condition temperature Tb (i.e., "YES"), the process proceeds to step ST3.

[0078] In step ST3, the control device 28 determines whether the second switch 261 is in a closed state. If the second switch 261 is in a closed state (i.e., "yes"), the process proceeds to step ST5. If the second switch 261 is in an open state (i.e., "no"), the process proceeds to step ST4. In step ST4, the control device 28 performs control to make the second switch 261 a closed state.

[0079] In step ST5, the control device 28 energizes the superconducting coil 21, increasing the excitation current. In step ST6, the control device 28 determines whether the higher of the two current leads 24a and 24b, i.e., the maximum temperature Tmax, is below the specified open-circuit condition temperature Ta. The open-circuit condition temperature Ta refers to the temperature at which the circuit is cut off to protect the current leads, i.e., the temperature at which the second switch 261 becomes open. The open-circuit condition temperature Ta is an example of a second condition value related to the opening and closing of the second switch 261. Furthermore, the second condition value can be any temperature-related condition value, which can be a temperature condition value or a condition value for the amount of temperature change.

[0080] Here, the second condition value is the same as or greater than the first condition value. Generally, the temperature of the current lead changes in stages depending on the energization. Therefore, when the temperature of the current lead tends to rise, if the temperature of the current lead exceeds the second condition value, the control device 28 will open the second switch 261. Conversely, when the temperature of the current lead tends to fall, if the temperature of the current lead is lower than the first condition value which is smaller than the second condition value, the control device 28 will close the second switch 261. In this way, by making the control device 28's control of the second switch 261 have a hysteresis characteristic based on the temperature change of the current lead, oscillation of the second switch 261 can be prevented, and burnout of the current leads 24a and 24b can be prevented.

[0081] If the maximum temperature Tmax > the open circuit condition temperature Ta (i.e., "No"), proceed to step ST7. If the maximum temperature Tmax ≤ the open circuit condition temperature Ta (i.e., "Yes"), proceed to step ST9.

[0082] In step ST7, the control device 28 sets the second switch 261 to the open circuit state. Here, Figure 4 (B) is a diagram illustrating an example of the operation of the current lead protection mode during the excitation process. When the second switch 261 is in the open-circuit state, the current flowing through the two current leads 24a and 24b becomes zero. Furthermore, even if a current loop is formed by the superconducting coil 21 and the permanent current switch 23 ( Figure 4 (C) shows the permanent current mode), and the current flowing through the two current leads 24a and 24b is also zero. With the current flowing through the current leads 24a and 24b becoming zero, the temperature of the current leads 24a and 24b decreases, thus preventing the current leads 24a and 24b from burning out.

[0083] In step ST8, the control device 28 determines whether the higher of the two current leads 24a and 24b, i.e., the maximum temperature Tmax, is below the specified closed-circuit condition temperature Tb. As mentioned above, the closed-circuit condition temperature Tb refers to the temperature at which the circuit cut off to protect the current leads is turned on, and is an example of a first condition value related to the opening and closing of the second switch. If the maximum temperature Tmax of the two current leads is greater than the closed-circuit condition temperature Tb, i.e., "no", the process of step ST8 is repeated.

[0084] If the maximum temperature Tmax of the two current leads is less than or equal to the closed-circuit condition temperature Tb (i.e., "yes"), the process proceeds to step ST4. It is determined that the temperatures of the two current leads 24a and 24b have sufficiently decreased, and the second switch 261 becomes closed.

[0085] In step ST9, the control device 28 determines whether the excitation current has reached the rated value (i.e., the rated current). If the rated current has been reached, i.e., "yes", the process ends. That is, if excitation is complete, the process transitions to permanent current mode. Otherwise, if the rated current has not been reached, i.e., "no", the process proceeds to step ST5.

[0086] Figure 4 (C) is a diagram illustrating an example of operation in permanent current mode. When the excitation current reaches its rated value, the heater 231 of the permanent current switch 23 is disconnected by the control device 28. With the disconnection of the heater 231, the superconducting component of the permanent current switch 23 is cooled and transitions from a normal conducting state to a superconducting state, and the permanent current switch 23 becomes a superconducting state (closed-circuit state).

[0087] As a result, a permanent current loop is formed by the permanent current switch 23 and the superconducting coil 21, with a permanent current flowing through the superconducting coil 21. Both the superconducting coil 21 and the permanent current switch 23 are in a superconducting state, with zero resistance. Therefore, even if the static magnetic field power supply 271 is removed from the superconducting magnet 10, the permanent current loop remains in a permanent current mode. In this case, the second switch 261 can be in a closed-circuit state or an open-circuit state.

[0088] Figure 6 (A) ~ Figure 6 (C) is a diagram illustrating the concept of three operating modes in the superconducting magnet 10. Figure 6 (A) is a diagram showing an example of operation in permanent current mode. Figure 6 In (A), the load 272 is electrically connected to the external power supply / load unit 27 instead of the static magnetic field power supply 271, and otherwise... Figure 4 (C) Same.

[0089] Figure 6 (B) is a diagram illustrating an example of operation in the demagnetization mode. The demagnetization mode refers to the operation mode in which a load is connected to the superconducting magnet 10 that generates a static magnetic field, i.e., the superconducting coil 21 in operation, to convert the magnetic energy of the superconducting coil into heat energy, thereby reducing the magnetic field generated by the superconducting magnet 10.

[0090] In demagnetizing mode, the heater 231 of the permanent current switch 23 is turned on by the control device 28. As a result, in demagnetizing mode where the permanent current switch 23 is in the open circuit state, a demagnetizing current powered by the magnetic energy stored in the superconducting coil 21 flows in the current loop of current lead 24b, load 272, and current lead 24a. The power generated by the magnetic energy stored in the superconducting coil 21 is consumed by the load 272, and the magnetic field generated by the superconducting magnet 10 is reduced.

[0091] Figure 6 (C) is a diagram illustrating an example of the operation of the current lead protection mode during demagnetization. During demagnetization, the MRI device 1 also performs... Figure 5 The same operation occurs in the flowchart. When the second switch 261 is in the open-circuit state, the current flowing through the two current leads 24a and 24b becomes zero. Furthermore, even if a current loop is formed by the superconducting coil 21 and the permanent current switch 23, the current flowing through the two current leads 24a and 24b is also zero. Because the current flowing through the current leads 24a and 24b becomes zero, the temperature of the current leads 24a and 24b decreases, thus preventing burn-out.

[0092] That is, the control device 28 controls the second switch 261 to be in an open or closed state based on indicators related to the temperatures of the current leads 24a and 24b monitored by the control device 28. Specifically, the control device 28 sets the second switch 261 to an open or closed state based on either the temperatures of the current leads 24a and 24b measured by the temperature sensors 25a and 25b, or the temperature change calculated based on the measured temperatures of the current leads 24a and 24b.

[0093] (Modification 1 of the first embodiment) Figure 7 This is a block diagram illustrating the internal configuration of the superconducting magnet 10 in a variation of the first embodiment. In this variation, the second switch 261 is an SSR. Furthermore, the static magnetic field power supply 271 and the load 272 are electrically connected to the superconducting coil 21. The difference between this variation and the first embodiment is that the control device 28 closes the SSR before increasing or decreasing the current flowing through the superconducting coil 21 for excitation, demagnetization (or demagnetization), and opens the SSR when the superconducting coil 21 loses its quench during excitation or demagnetization.

[0094] Reference Figure 8 The flowchart illustrates the operation of the MRI device 1 in the modified example 1 of the first embodiment.

[0095] In step ST31, the control device 28 acquires the temperatures of the two current leads 24a and 24b. Furthermore, the temperatures of the two current leads 24a and 24b are monitored for a predetermined time or continuously, enabling the determination related to the temperatures of the two current leads 24a and 24b in step ST36. Additionally, in step ST31, the superconducting coil 21 is not energized.

[0096] In step ST32, the control device 28 determines whether the current flowing through the superconducting coil 21 will be increased or decreased for excitation or demagnetization (or demagnetization). In step ST32, if the control device 28 determines that the current flowing through the superconducting coil will be increased or decreased for excitation or demagnetization, i.e., if "yes", the process proceeds to step ST33.

[0097] In step ST33, the control device 28 controls the SSR, which serves as the second switch 261, to be in a closed state. In step ST34, the control device 28 energizes the superconducting coil 21, increasing or decreasing the excitation current.

[0098] In step ST35, the control device 28 determines whether the superconducting coil 21 has lost its quench. If the control device 28 determines that the superconducting coil 21 has lost its quench (i.e., "yes"), the process proceeds to step ST37. In step ST37, the control device 28 causes the second switch 261 (SSR), which was in a closed state in step ST33, to become open, returning to the operation of step ST32. If the control device 28 determines that the superconducting coil 21 has not lost its quench (i.e., "no"), the process proceeds to step ST36.

[0099] In step ST36, the control device 28 determines whether the higher of the two current leads 24a and 24b, i.e., the maximum temperature Tmax, is below the specified open-circuit condition temperature Ta. If the maximum temperature Tmax > the open-circuit condition temperature Ta (i.e., "No"), the process proceeds to step ST37. If the maximum temperature Tmax ≤ the open-circuit condition temperature Ta (i.e., "Yes"), the process proceeds to step ST38.

[0100] In step ST38, the control device 28 determines whether the excitation current has reached the target value (i.e., the target current). The target value can be a rated value for excitation or a current value set for demagnetization or demagnetization. In step ST38, if the target current is reached (i.e., "yes"), the process ends. That is, if the target current is not reached in step ST38 (i.e., "no"), the process proceeds to step ST34.

[0101] (Modification 2 of the first embodiment) Figure 9 This is a block diagram illustrating the internal configuration of the superconducting magnet 10 in a variation 2 of the first embodiment. In variation 2 of the first embodiment, the second switch 261 is an SSR. In variation 2 of the first embodiment, the load 272 and the UPS 274 are electrically connected to the superconducting coil 21. That is, variation 2 of the first embodiment is a case where the static magnetic field power supply 271 is not electrically connected to the superconducting coil 21 to perform demagnetization.

[0102] In a variation 2 of the first embodiment, the difference from the first embodiment is that the control device 28 receives an instruction related to demagnetization and sets the SSR to a closed state according to the instruction.

[0103] Reference Figure 10 The flowchart illustrates the operation of the MRI device 1 in Modified Example 2 of the first embodiment. Figure 10 The flowchart (i.e., variation 2 of the first embodiment) includes steps ST31, ST33, ST34, ST36, ST37, and ST38. Figure 8The flowchart (i.e., variation 1 of the first embodiment) is essentially the same, so repeated descriptions are omitted. In variation 2 of the first embodiment, after step ST31, the process proceeds to step ST41.

[0104] In step ST41, the control device 28 receives an instruction related to demagnetization. Upon receiving this instruction, in step ST33 following step ST41, the control device 28 performs control to close the SSR, which serves as the second switch 261. This allows demagnetization to be performed without causing the superconducting coil 21 to lose quench.

[0105] In step ST41, the control device 28 may also receive, for example, indications related to demagnetization associated with power outages, such as sensing the start-up of the UPS 274 that operates during a power outage, sensing the switching from commercial power to the UPS 274.

[0106] In step ST41, the control device 28 may also receive, for example, demagnetization-related instructions from users such as doctors, technicians, or service personnel via the input interface 43, such as those related to suction accidents. Furthermore, it is not limited to... Figure 9 When the UPS274 is electrically connected, it can also provide demagnetization-related instructions via input interface 43 when commercial power is available.

[0107] Furthermore, in a variation of the first embodiment, in step ST41, an instruction related to demagnetization is received; therefore, in step ST34, the control device 28 energizes the superconducting coil 21 to reduce the excitation current. Additionally, in step ST38, the target value becomes a current value set for demagnetization or demagnetization.

[0108] (Modification 3 of the first embodiment) Figure 11 This is a block diagram illustrating the internal configuration of a superconducting magnet according to a variation 3 of the first embodiment. In variation 3 of the first embodiment, the control of the open and closed states of the second switch 261 by monitoring the voltage applied to the current lead differs from the first embodiment, which uses monitoring the temperature of the current lead for this control. Furthermore, in variations 1 and 2 of the first embodiment, the open and closed states of the second switch 261 can also be controlled by monitoring the voltage applied to the current lead.

[0109] In a variation 3 of the first embodiment, the MRI device 1 replaces the temperature sensors 25a and 25b, or together with the temperature sensors 25a and 25b, it includes at least one of a voltmeter 29a for measuring the potential difference of the current lead 24a and a voltmeter 29b for measuring the potential difference of the current lead 24b.

[0110] The potential difference of current lead 24a refers to the difference between the potential of the end of current lead 24a on the high-temperature side (i.e., the external power supply / load section 27 side) and the potential of the end on the low-temperature side (i.e., the superconducting coil 21 side). Similarly, the potential difference of current lead 24b refers to the difference between the potential of the end of current lead 24b on the high-temperature side (i.e., the external power supply / load section 27 side) and the potential of the end on the low-temperature side (i.e., the superconducting coil 21 side). The potential difference of current leads 24a and 24b becomes an indicator related to the potential difference of the current leads. In addition, the potential difference of current leads 24a and 24b can also become an indicator related to the temperature of the current leads.

[0111] Reference Figure 12 The flowchart illustrates the operation of the MRI apparatus 1 in Modification 3 of the first embodiment. Figure 12 In the flowchart (i.e., variant 3 of the first embodiment), instead of Figure 5 The flowchart (i.e., the first embodiment) shows step ST1, and the processes in steps ST11 and ST12 are performed accordingly. Other steps ST2 to ST9 are... Figure 5 The flowchart (i.e., the first embodiment) is essentially the same, so repeated descriptions are omitted.

[0112] In step ST11, control device 28 measures the potential difference between two current leads 24a and 24b. In step ST12, control device 28 estimates the temperature of the current leads based on the potential difference measured by voltmeters 29a and 29b. Furthermore, the measurement of the potential difference between the two current leads 24a and 24b and the estimation of the temperature of the current leads based on the measured potential difference are performed at a predetermined time or continuously, enabling determinations related to the temperatures of the two current leads 24a and 24b in steps ST2, ST6, and ST8.

[0113] exist Figure 12 In the flowchart, the opening and closing state of the second switch 261 is controlled based on the temperature of the current lead estimated from the potential difference, but the opening and closing state of the second switch 261 can also be controlled based on the temperature change of the current lead estimated from the potential difference.

[0114] That is, the control device 28 sets the second switch 261 to an open or closed state based on the potential difference between the current leads 24a and 24b measured by voltmeters 29a and 29b, and the temperature or temperature change of the current leads 24a and 24b estimated from the potential difference measured by voltmeters 29a and 29b. Furthermore, the control device 28 sets the second switch 261 to a closed state if the potential difference between the current leads 24a and 24b, the temperature, and the temperature change are below a predetermined first condition value, and sets the second switch 261 to an open state if the temperature exceeds a predetermined second condition value. Here, the first and second condition values ​​can be temperature-related or potential difference-related conditions.

[0115] (Second Implementation) Figure 13 This is a block diagram illustrating an example of the internal configuration of the superconducting magnet 10 according to the second embodiment. The second embodiment differs from the first embodiment in that it also includes a third switch 262 and a second load 273. The second load 273 in the second embodiment is a resistor, but the second load 273 can also be a diode. In the case where the second load 273 is a diode, the third switch 262 may not be required.

[0116] In the second embodiment, the external power supply / load unit 27 is composed of a static magnetic field power supply 271. In this case, a third switch 262 and a second load 273 are also provided between the static magnetic field power supply 271 and the two current leads 24a and 24b, which are electrically connected in parallel with the static magnetic field power supply 271. The third switch 262 and the second load 273 are connected in series. The third switch 262 mechanically or electrically switches the connection of the electrical circuit. That is, the third switch 262 is configured to switch between an electrically connected state and an electrically open state. Furthermore, regarding the third switch 262, the electrically connected state is referred to as the closed state, and the electrically open state is referred to as the open state. The third switch 262 can be a mechanical switch that switches the current on and off, or it can be a semiconductor switch.

[0117] Figure 14 (A) ~ Figure 14 (C) is a diagram illustrating the concept of three operating modes in the superconducting magnet 10. Figure 14 (A) is a diagram showing an example of the excitation mode.

[0118] In the excitation mode of the second embodiment, the second switch 261 is in a closed state and the third switch 262 is in an open state. Additionally, in the excitation mode, the permanent current switch 23 is in an open state. In this case, the heater 231 of the permanent current switch 23 is turned on by the control device 28. In the excitation mode, the excitation current supplied from the static magnetic field power supply 271 flows in the current loop of current lead 24a, superconducting coil 21, and current lead 24b. When the excitation current gradually increases from zero to reach its rated value, the system transitions from the excitation mode to the permanent current mode.

[0119] Reference Figure 15 Flowcharts and Figure 14 (B) illustrates an example of the operation of the current lead protection mode during the excitation process. Figure 15 In the flowchart (i.e., the second embodiment), instead of Figure 5 The flowchart (i.e., the first embodiment) shows steps ST3, ST4, and ST7, and the processing of steps ST21, ST22, and ST13 is performed. Other steps ST1, ST2, ST5, ST6, ST8, and ST9 are... Figure 5 The flowchart (i.e., the first embodiment) is essentially the same, so repeated descriptions are omitted. In the second embodiment, after step ST2, the process proceeds to step ST21.

[0120] In step ST21, the control device 28 determines whether the second switch 261 is in a closed state and whether the third switch 262 is in an open state. If the second switch 261 is in a closed state and the third switch 262 is in an open state (i.e., "yes"), the process proceeds to step ST5. If the second switch 261 is in an open state and the third switch 262 is in a closed state (i.e., "no"), the process proceeds to step ST22.

[0121] In step ST22, the control device 28 closes the second switch 261 and opens the third switch 262. In the second embodiment, after step ST22, the process proceeds to step ST5, and after step ST6, the process proceeds to step ST23.

[0122] In step ST23, the control device 28 sets the second open / close device 261 to the open state and the third open / close device 262 to the closed state.

[0123] here, Figure 14(B) is a diagram illustrating an example of the operation of the current lead protection mode during the excitation process. When the second switch 261 and the third switch 262 are both in the open-circuit state, the current flowing through the two current leads 24a and 24b becomes zero. Furthermore, even if a current loop is formed by the superconducting coil 21 and the permanent current switch 23 ( Figure 14 (C) shows the permanent current mode), and the current flowing through the two current leads 24a and 24b is also zero. Since the current flowing through the two current leads 24a and 24b becomes zero, the temperature of the current leads 24a and 24b decreases or remains constant, thus preventing burn-out.

[0124] Figure 14 (C) is a diagram illustrating an example of operation in permanent current mode. When the excitation current reaches its rated value, the heater 231 of the permanent current switch 23 is disconnected by the control device 28. With the heater 231 disconnected, the superconducting component of the permanent current switch 23 is cooled and transitions from a normal conducting state to a superconducting state, and the permanent current switch 23 becomes a closed circuit. Furthermore, in the permanent current mode of the second embodiment, the second switch 261 becomes an open circuit, and the third switch 262 becomes a closed circuit.

[0125] Here, refer to Figure 16 (A) ~ Figure 16 (D) describes the switch that transitions from excitation mode to permanent current mode. In excitation mode, the permanent current switch 23 ( becomes an open circuit). Figure 16 (A)) Switch to closed-circuit mode ( Figure 16 (B) After that, the third switch 262 switches from the open circuit state to the closed circuit state. Figure 16 (C) The second switch 261 switches from the closed state to the open state. Figure 16 (D) In ​​this case, the control device 28 monitors the opening and closing status of at least one of the second opener / closer 261 and the third opener / closer 262. In addition, the control device 28 may further monitor the opening and closing status of the first opener / closer.

[0126] That is, during the excitation process of supplying current to the superconducting coil 21, the control device 28 performs control to make the second switch 261 closed and the third switch 262 open. Furthermore, after supplying current to the superconducting coil 21, the control device 28 performs control to make the second switch 261 open and the third switch 262 closed.

[0127] As a result, a permanent current loop is formed by the permanent current switch 23 and the superconducting coil 21, with a permanent current flowing through the superconducting coil 21. Both the superconducting coil 21 and the permanent current switch 23 are in a superconducting state with zero resistance. Therefore, even if the static magnetic field power supply 271 is removed from the superconducting magnet 10, it remains in a permanent current mode that maintains the permanent current loop.

[0128] Figure 17 (A) ~ Figure 17 (C) is a diagram illustrating the concept of three operating modes in the superconducting magnet 10. Figure 17 (A) is a diagram illustrating an example of operation in permanent current mode, and... Figure 14 (C) Same.

[0129] Figure 17 (B) is a diagram illustrating an example of operation in the demagnetization mode. In the demagnetization mode of the second embodiment, the second switch 261 is in an open-circuit state, and the third switch 262 is in a closed-circuit state. Additionally, in the demagnetization mode, the permanent current switch 23 is in a closed-circuit state. In this case, the heater 231 of the permanent current switch 23 is controlled to disconnect by the control device 28. In the demagnetization mode, a demagnetizing current powered by the magnetic energy stored in the superconducting coil 21 flows in the current loop of the current lead 24b, the second load 273, and the current lead 24a. The power generated by the magnetic energy stored in the superconducting coil 21 is consumed by the second load 273, and the magnetic field generated by the superconducting magnet 10 is reduced.

[0130] Figure 17 (C) is a diagram illustrating an example of the operation of the current lead protection mode during demagnetization. During demagnetization, the MRI device 1 also performs... Figure 15 The same operation occurs in the flowchart. When the second switch 261 and the third switch 262 are both in the open circuit state, the current flowing through the two current leads 24a and 24b becomes zero. Furthermore, even if a current loop is formed by the superconducting coil 21 and the permanent current switch 23, the current flowing through the two current leads 24a and 24b remains zero. The zero current flowing through the two current leads 24a and 24b results in a temperature decrease or no change in the current leads 24a and 24b, thus preventing burn-out.

[0131] Thus, according to the MRI apparatus 1 of the embodiment, when the temperature of the current lead reaches or exceeds a predetermined value, in order to prevent burn-out of the current lead, the switch provided between the current lead and the static magnetic field power supply, and the switch provided between the current lead and the load, are opened, cutting off the circuit with the static magnetic field power supply and / or the load, thereby making the current flowing through the current lead zero. As a result, the temperature of the current lead decreases, preventing burn-out of the current lead.

[0132] According to at least one embodiment described above, current leads used in helium-free superconducting magnets can be protected.

[0133] Furthermore, in the above embodiments, the term "processor" refers to circuits such as dedicated or general-purpose CPUs (Central Processing Units), GPUs (Graphics Processing Units), application-specific integrated circuits (ASICs), and programmable logic devices (e.g., simple programmable logic devices (SPLDs), complex programmable logic devices (CPLDs), and field-programmable gate arrays (FPGAs)).

[0134] In the case of a processor, such as a CPU, the processor implements various functions by reading and executing programs stored in memory. Alternatively, in the case of a processor, such as an ASIC, instead of storing the program in memory, the functionality equivalent to that program is directly programmed into the processor's circuitry as logic circuitry. In this case, the processor implements various functions by reading and executing the hardware processing of the program incorporated into the circuitry. Alternatively, the processor can also combine software processing and hardware processing to implement various functions.

[0135] Furthermore, while the above embodiments illustrate an example where a single processor in the processing circuit implements each function, multiple independent processors can also be combined to form the processing circuit, with each processor implementing its respective function. Additionally, when multiple processors are provided, the program storage circuit can be set up separately for each processor, or a single storage circuit can store programs corresponding to the functions of all processors.

[0136] Several embodiments have been described, but these embodiments are given by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, modifications, and combinations of embodiments are possible without departing from the spirit of the invention. These embodiments or variations thereof are included within the scope or spirit of the invention, as well as within the scope of the invention as described in the claims and its equivalents.

[0137] Regarding the above-described embodiments, the following notes are disclosed as an aspect of the invention and as optional features.

[0138] (Note 1) One embodiment of a superconducting magnet includes a superconducting coil, a permanent current switch or a first switch, at least one of an external power source and a load, a current lead, a second switch, and a control device. The superconducting coil generates a static magnetic field. The permanent current switch is electrically connected to the superconducting coil, switching between a superconducting state and a normally conducting state. The first switch is electrically connected to the superconducting coil, mechanically or electrically opening and closing the circuit. An external power source supplies current to the superconducting coil. The load releases the magnetic energy of the superconducting coil. The current lead electrically connects the external power source, the load, or both the external power source and the load to the superconducting coil. The second switch is disposed between the external power source, the load, or both the external power source and the load and the superconducting coil. The second switch has a first state where the external power source, the load, or both the external power source and the load are electrically connected to the superconducting coil, and a second state where the electrical connection between the external power source, the load, or both the external power source and the load and the superconducting coil is disconnected. The control device switches the second switch between the first and second states.

[0139] (Note 2) The current leads can be made of high-temperature superconducting materials or phosphorus deoxidized copper.

[0140] (Note 3) The control device can also switch the second switch between the first state and the second state based on an index related to the temperature of the current lead.

[0141] (Note 4) The current lead may have a first current lead and a second current lead.

[0142] Here, the first current lead and the second current lead are electrically connected to the two ends of the superconducting coil, respectively. The first circuit and the second circuit that electrically connect the first current lead and the second current lead are connected in parallel. The first circuit has the external power supply, and the second circuit has a third switch and a second load. The third switch has an electrically connected state and an electrically open state. The third switch and the second load are connected in series in the second circuit.

[0143] (Note 5) Alternatively, the control device may, during the process of supplying current to the superconducting coil, perform control to make the second switch-off state the first state and the third switch-off state electrically open.

[0144] (Note 6) Alternatively, after the control device completes the process of supplying current to the superconducting coil, it controls the second switch to the second state and the third switch to be electrically connected.

[0145] (Note 7) Alternatively, the superconducting magnet may also include at least one sensor for measuring the temperature of at least one of the current leads. Here, the indicator related to the temperature of the current lead is the temperature of the current lead measured by the sensor.

[0146] (Postscript 8) Alternatively, if the temperature-related index of the current lead is below a first condition value, the control device sets the second switch to the first state. Alternatively, if the temperature-related index of the current lead exceeds a second condition value, the control device sets the second switch to the second state. Here, the second condition value is a value greater than or equal to the first condition value.

[0147] (Note 9) Alternatively, the superconducting magnet may also include at least one voltmeter for measuring the potential difference of at least one of the current leads. The temperature-related parameters of the current leads are estimated based on the potential difference.

[0148] (Postscript 10) Alternatively, the superconducting magnet may also include at least one voltmeter for measuring the potential difference of at least one of the current leads. Here, the control device switches the second switch between the first state and the second state based on an index related to the potential difference of the current leads.

[0149] (Postscript 11) Alternatively, the control device may set the second switch to the first state when the index related to the potential difference of the current lead is below a first condition value, and set the second switch to the second state when the index related to the potential difference of the current lead exceeds a second condition value. Here, the second condition value is a value greater than or equal to the first condition value.

[0150] (Postscript 12) Alternatively, the voltmeter measures the potential difference between the high-temperature end and the low-temperature end of the current lead, which is the potential difference of the current lead.

[0151] (Postscript 13) Alternatively, the second switch may be located at both ends of the external power source, the load, or both the external power source and the load.

[0152] (Postscript 14) Alternatively, the superconducting magnet may also include at least one resistor or at least one set of diodes that are electrically connected in parallel with the superconducting coil and the permanent current switch.

[0153] (Postscript 15) One embodiment of the magnetic resonance imaging apparatus has any of the above-mentioned superconducting magnets and a superconducting coil that generates a static magnetic field.

Claims

1. A superconducting magnet, comprising: Superconducting coils generate static magnetic fields; A permanent current switch or a first switch is electrically connected to the superconducting coil. The permanent current switch switches between the superconducting state and the normal conducting state. The first switch mechanically or electrically opens and closes the electrical circuit. An external power source and a load are required, wherein the external power source supplies current to the superconducting coil and the load causes the magnetic energy of the superconducting coil to be released. Current leads are used to electrically connect the external power source, the load, or both the external power source and the load to the superconducting coil. A second switch is disposed between the external power source, the load, or both the external power source and the load and the superconducting coil. The second switch has a first state in which the external power source, the load, or both the external power source and the load are electrically connected to the superconducting coil, and a second state in which the electrical connection between the external power source, the load, or both the external power source and the load and the superconducting coil is disconnected. as well as The control device switches the second switch between the first state and the second state.

2. The superconducting magnet according to claim 1, The current leads are made of high-temperature superconducting materials or phosphorus deoxidized copper.

3. The superconducting magnet according to claim 1, The control device switches the second switch between the first state and the second state based on an index related to the temperature of the current lead.

4. The superconducting magnet according to claim 3, The current lead includes a first current lead and a second current lead. The first current lead and the second current lead are electrically connected to the two ends of the superconducting coil, respectively. The first circuit and the second circuit, which are electrically connected by the first current lead and the second current lead, are connected in parallel. The first circuit has the external power supply. The second circuit includes a third switch and a second load. The third switch has an electrically connected state and an electrically open state. The third switch and the second load are connected in series in the second circuit.

5. The superconducting magnet according to claim 4, During the process of supplying current to the superconducting coil, the control device causes the second switch to the first state and the third switch to the electrically open state.

6. The superconducting magnet according to claim 4, After the control device completes the process of supplying current to the superconducting coil, it sets the second switch to the second state and sets the third switch to an electrically connected state.

7. The superconducting magnet according to claim 3, The superconducting magnet also includes at least one sensor for measuring the temperature of at least one of the current leads. The metric related to the temperature of the current lead is the temperature of the current lead measured by the sensor.

8. The superconducting magnet according to claim 7, The control device sets the second switch to the first state when the temperature-related index of the current lead is below a first condition value, and sets the second switch to the second state when the temperature-related index of the current lead exceeds a second condition value. The second condition value is a value greater than or equal to the first condition value.

9. The superconducting magnet according to claim 3, The superconducting magnet also includes at least one voltmeter for measuring the potential difference of at least one of the current leads. The parameters related to the temperature of the current lead are based on the temperature of the current lead estimated from the potential difference.

10. The superconducting magnet according to claim 1, The superconducting magnet also includes at least one voltmeter for measuring the potential difference of at least one of the current leads. The control device switches the second switch between the first state and the second state based on an index related to the potential difference of the current lead.

11. The superconducting magnet according to claim 10, The control device sets the second switch to the first state when an index related to the potential difference of the current lead is below a first condition value, and sets the second switch to the second state when the index related to the potential difference of the current lead exceeds a second condition value. The second condition value is a value greater than or equal to the first condition value.

12. The superconducting magnet according to claim 10, The voltmeter measures the potential difference between the high-temperature end and the low-temperature end of the current lead, which is the potential difference of the current lead.

13. The superconducting magnet according to claim 1, The second switch is disposed at both ends of the external power supply, the load, or both the external power supply and the load.

14. The superconducting magnet according to claim 1, The superconducting magnet also includes at least one resistor or at least one set of diodes that are electrically connected in parallel with the superconducting coil and the permanent current switch.

15. A magnetic resonance imaging device comprising a superconducting magnet, The superconducting magnet has the following characteristics: Superconducting coils generate static magnetic fields; A permanent current switch or a first switch is electrically connected to the superconducting coil. The permanent current switch switches between the superconducting state and the normal conducting state. The first switch mechanically or electrically opens and closes the circuit. An external power source, a load, or either the external power source or the load, wherein the external power source supplies current to the superconducting coil and the load causes the magnetic energy of the superconducting coil to be released; A second switch is disposed between the external power source, the load, or both the external power source and the load and the superconducting coil. The second switch has a first state in which the external power source, the load, or both the external power source and the load are electrically connected to the superconducting coil, and a second state in which the electrical connection between the external power source, the load, or both the external power source and the load and the superconducting coil is disconnected. The control device switches the second switch between the first state and the second state.

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