Superconducting magnet device and control device for superconducting magnet device

Abstract

The present application provides a kind of diagnostic techniques for superconducting magnet device in ultra-low temperature refrigerator.The superconducting magnet device (100) has: superconducting coil device (110), which can be operated in multiple operating modes;Ultra-low temperature refrigerator (10), which cools the superconducting coil device;Controller (140) is configured to operate the superconducting coil device in the operating mode selected from the multiple operating modes, and determine the operating parameters of the ultra-low temperature refrigerator (10) according to the comparison of the cooling temperature of the superconducting coil device (110) or the ultra-low temperature refrigerator (10) and the temperature target value, and drive the ultra-low temperature refrigerator (10) using the determined operating parameters;And ultra-low temperature refrigerator monitor (142) is configured to obtain the value of the determined operating parameters when the superconducting coil device (110) is operated in the selected operating mode, and diagnose the ultra-low temperature refrigerator (10) according to the obtained value of the operating parameters.

Description

[0001] This application claims priority to Japanese Patent Application No. 2025-075734, filed on April 30, 2025. The entire contents of that Japanese application are incorporated herein by reference. Technical Field

[0002] This invention relates to a superconducting magnet device and a control device for the superconducting magnet device. Background Technology

[0003] Previously, to save energy, superconducting magnet devices using cryogenic refrigerators equipped with inverters for cooling were known. In these superconducting magnet devices, when cooling from ambient temperature (e.g., room temperature) to a set cryogenic temperature (e.g., 10K) upon device startup, if the measured temperature of the superconducting magnet device is higher than the set temperature, the cooling capacity of the cryogenic refrigerator is increased by increasing the output frequency of the inverter. Conversely, if the measured temperature of the superconducting magnet device is lower than the set temperature, the cooling capacity of the cryogenic refrigerator is decreased by decreasing the output frequency of the inverter.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2000-121192 Through in-depth research on superconducting magnet devices, the inventors have recognized the following challenges. In superconducting magnet devices, if the cryogenic refrigerator malfunctions, cooling is lost, ultimately forcing the device to cease operation. Due to the large heat capacity of superconducting magnet devices, cooling down after heating requires a considerable amount of time. In particular, in the event of a sudden malfunction, such as the time required to schedule repairs to the cryogenic refrigerator, the recovery time for the superconducting magnet device is often even longer, which is undesirable.

[0005] However, if the malfunctions or symptoms of the cryogenic refrigerator can be identified and addressed in advance in a planned manner, the impact on the operation of the superconducting magnet device can be minimized. A typical countermeasure is to monitor the cooling temperature of the cryogenic refrigerator to track its performance degradation over time. However, this method may not be effective for cryogenic refrigerators equipped with frequency converters. This is because even if the cooling performance of the cryogenic refrigerator decreases, this performance degradation can be compensated for to some extent by increasing the output frequency of the frequency converter, thus having little impact on the cooling temperature. Summary of the Invention

[0006] One exemplary objective of one embodiment of the present invention is to provide a diagnostic technique for cryogenic refrigerators in superconducting magnet devices.

[0007] According to one embodiment of the present invention, a superconducting magnet device includes: a superconducting coil device capable of operating in multiple operating modes; a cryogenic refrigerator for cooling the superconducting coil device; a controller configured to operate the superconducting coil device in an operating mode selected from the multiple operating modes, and to determine operating parameters of the cryogenic refrigerator based on a comparison between the cooling temperature of the superconducting coil device or the cryogenic refrigerator and a target temperature value, and to drive the cryogenic refrigerator using the determined operating parameters; and a cryogenic refrigerator monitor configured to acquire values ​​of the determined operating parameters when the superconducting coil device operates in the selected operating mode, and to diagnose the cryogenic refrigerator based on the acquired values ​​of the operating parameters.

[0008] According to one embodiment of the present invention, a control device for a superconducting magnet device is provided. The superconducting magnet device includes a superconducting coil device capable of operating in multiple operating modes and a cryogenic refrigerator for cooling the superconducting coil device. The control device includes: a controller configured to operate the superconducting coil device in an operating mode selected from multiple operating modes, and to determine operating parameters of the cryogenic refrigerator based on a comparison between the cooling temperature of the superconducting coil device or the cryogenic refrigerator and a target temperature value, and to drive the cryogenic refrigerator using the determined operating parameters; and a cryogenic refrigerator monitor configured to acquire values ​​of the determined operating parameters when the superconducting coil device is operating in the selected operating mode, and to diagnose the cryogenic refrigerator based on the acquired values ​​of the operating parameters.

[0009] Furthermore, any combination of the above-mentioned constituent elements, or the substitution of the constituent elements or expressions of the present invention among methods, apparatuses, systems, computer programs, storage media, etc., are also effective as embodiments of the present invention.

[0010] Invention Effects According to the present invention, a diagnostic technique for cryogenic refrigerators in superconducting magnet devices can be provided. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating the superconducting magnet device involved in the embodiment.

[0012] Figure 2 It schematically shows that it can be mounted on Figure 1 The diagram shows the cryogenic refrigerator of the superconducting magnet device.

[0013] Figure 3 It schematically shows that it can be mounted on Figure 1 The diagram shows the cryogenic refrigerator of the superconducting magnet device.

[0014] Figure 4This is a diagram schematically illustrating an exemplary operation of the superconducting magnet device involved in the embodiment.

[0015] Figure 5 This is a flowchart illustrating an example of a diagnostic method for a cryogenic refrigerator according to an embodiment.

[0016] Figure 6 It is a chart schematically showing the historical records of the operating parameters of the cryogenic refrigerator used in the diagnosis of the cryogenic refrigerator involved in the embodiment.

[0017] Figure 7 It is a chart schematically illustrating the statistical analysis of the operating history data of the superconducting magnet device used in the diagnosis of the cryogenic refrigerator according to the embodiment.

[0018] In the diagram: 10-Cryogenic refrigerator, 12-Compressor, 14-Expander, 24-Compressor motor, 42-Expander motor, 100-Superconducting magnet device, 112-Superconducting coil, 138-Control device, 140-Controller, 142-Cryogenic refrigerator monitor. Detailed Implementation

[0019] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the specification and drawings, the same or equivalent constituent elements, components, and processes are labeled with the same reference numerals, and repeated descriptions are omitted where appropriate. The proportions and shapes of the components shown in the drawings are provided for ease of explanation and should not be interpreted as limiting unless otherwise specified. The embodiments are illustrative and do not limit the scope of the invention in any way. All features or combinations thereof described in the embodiments are not necessarily the essence of the invention.

[0020] Figure 1 This diagram schematically illustrates the superconducting magnet device 100 according to the embodiment. The superconducting magnet device 100 is, for example, mounted as a magnetic field source in 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 other high magnetic field utilization machines (not shown), and is capable of generating the high magnetic field required by these devices.

[0021] The superconducting magnet device 100 includes a superconducting coil device 110, a cryogenic device 120, at least one temperature sensor 130, a status monitoring sensor 132, and a control device 138. The superconducting coil device 110 includes a superconducting coil 112, a current-carrying wire 114, and an excitation power supply 116. The cryogenic device 120 includes a vacuum container 122, a cryogenic refrigerator 10, and a thermal shield 124. The control device 138 of the superconducting magnet device 100 includes a controller 140 for controlling the superconducting coil device 110 and the cryogenic refrigerator 10, and a cryogenic refrigerator monitor 142 for diagnosing the cryogenic refrigerator 10.

[0022] A superconducting coil 112 is disposed within a vacuum container 122. The superconducting coil 112 is thermally connected to a cryogenic refrigerator 10 disposed within the vacuum container 122 and is used in a cryogenic state cooled to below a critical temperature. The superconducting coil 112 is configured to generate a strong magnetic field by energizing it in this cooled state. The superconducting coil 112 can be a known superconducting coil (e.g., a so-called cryogenic superconducting coil).

[0023] Vacuum container 122 is an insulated vacuum container that provides a cryogenic vacuum environment suitable for placing superconducting coil 112 in a superconducting state; it is also called a cryostat. Typically, vacuum container 122 has a cylindrical shape or a cylindrical shape with a hollow center. Thus, vacuum container 122 has a generally flat circular or annular top plate 122a and a bottom plate 122b, and cylindrical sidewalls (cylindrical outer peripheral walls, or coaxially arranged cylindrical outer and inner peripheral walls) 122c connecting them. A cryogenic refrigerator 10 may be disposed on the top plate 122a of vacuum container 122. Vacuum container 122 is made of, for example, a metallic material such as stainless steel or other suitable high-strength materials to withstand ambient pressure (e.g., atmospheric pressure).

[0024] The cryogenic refrigerator 10 is configured to cool the heat shield 124 to a first cooling temperature and cool the superconducting coil 112 to a second cooling temperature lower than the first cooling temperature. In this embodiment, the cryogenic refrigerator 10 is a two-stage cryogenic refrigerator and includes a first cooling stage 33 and a second cooling stage 35. The first cooling temperature can be in the temperature range of about 20K to about 100K, for example, in the temperature range of about 30K to about 50K, and the second cooling temperature can be in the temperature range of about 3K to about 20K, for example, in the temperature range of about 4K. An exemplary structure of the cryogenic refrigerator 10 will be referred to... Figure 2 and Figure 3 To be described later.

[0025] exist Figure 1In the example shown, one cryogenic refrigerator 10 is shown. However, depending on the needs, such as when the superconducting coil 112 is large, the superconducting magnet device 100 may have multiple cryogenic refrigerators 10, and the same superconducting coil 112 may be cooled by these cryogenic refrigerators 10.

[0026] A heat shield 124 is disposed within the vacuum container 122, surrounding the superconducting coil 112. The heat shield 124 is made of a metallic material, such as copper, or other materials with high thermal conductivity. The heat shield 124 is directly mounted to and thermally connected to the first cooling stage 33 of the cryogenic refrigerator 10. Alternatively, the heat shield 124 may be mounted to the first cooling stage 33 via a flexible or rigid heat transfer component. During operation of the superconducting magnet device 100, the heat shield 124 is cooled to a first cooling temperature by the first cooling stage 33. The heat shield 124 provides thermal protection to cryogenic components of the cryogenic refrigerator 100, such as the second cooling stage 35 and the superconducting coil 112, which are disposed inside the heat shield 124 and cooled to a lower temperature than the heat shield 124, from radiant heat from the vacuum container 122.

[0027] In this embodiment, the superconducting magnet device 100 is configured as a so-called conductive cooling type, that is, the superconducting coil 112 is directly cooled by the cryogenic refrigerator 10. The superconducting coil 112 is thermally connected to the second cooling stage 35 via a heat transfer member 126. The heat transfer member 126 is made of a metal material such as copper or other materials with high thermal conductivity, and connects the superconducting coil 112 to the second cooling stage 35. The heat transfer member 126 can be a rigid member that rigidly connects the superconducting coil 112 to the second cooling stage 35, or it can be connected in a flexible manner that allows relative displacement between the superconducting coil 112 and the second cooling stage 35. Alternatively, the superconducting coil 112 can be directly mounted on the second cooling stage 35 and thermally connected to the second cooling stage 35. During the operation of the superconducting magnet device 100, the superconducting coil 112 is cooled to a second cooling temperature by the second cooling stage 35.

[0028] Alternatively, in other embodiments, the superconducting magnet device 100 can also be configured as an immersion-cooled type, in which the superconducting coil 112 is immersed in a cryogenic liquid refrigerant such as liquid helium. In this case, the cryogenic refrigerator 10 is used for cooling, i.e., recondensation, of the liquid refrigerant. The cryogenic refrigerator 10 can cool the superconducting coil 112 via the liquid refrigerant.

[0029] The superconducting coil 112 is connected to an excitation power supply 116 located outside the vacuum container 122 via a current feed line 114. Current (hereinafter also referred to as excitation current) is supplied from the excitation power supply 116 to the superconducting coil 112 through the current feed line 114. As a result, the superconducting magnet device 100 is able to generate a strong magnetic field.

[0030] The current lead 114 includes an external wiring 114a, a feedthrough terminal 114b, an outer current lead 114c, and an inner current lead 114d, and forms a current path from the excitation power supply 116 to the superconducting coil 112. Typically, one current lead 114 is provided on the positive side and one on the negative side.

[0031] An external wiring 114a, located outside the vacuum container 122, connects the excitation power supply 116 to a feedthrough terminal 114b located on the wall of the vacuum container 122. The external wiring 114a can be a suitable power cable. The feedthrough terminal 114b is an airtight terminal for introducing current into the vacuum container 122, connecting the external wiring 114a to the internal wiring (i.e., the outer current lead 114c and the inner current lead 114d) within the vacuum container 122. The current lead 114 can maintain the airtightness of the vacuum container 122 while passing through the wall of the vacuum container 122 via the feedthrough terminal 114b.

[0032] An outer current lead 114c is disposed outside the heat shield 124 within the vacuum container 122, and connects the feedthrough terminal 114b to the inner current lead 114d. The outer current lead 114c is made of a highly conductive metallic material, such as pure copper (e.g., oxygen-free copper). The low-temperature end of the outer current lead 114c, connected to the inner current lead 114d, is thermally connected to the heat shield 124. The low-temperature end of the outer current lead 114c is fixed to the heat shield 124, or connected to the heat shield 124 via a suitable heat transfer component, and is cooled to a first cooling temperature, similar to the heat shield 124. However, the outer current lead 114c is electrically insulated from the heat shield 124. For example, it can be mounted to the heat shield 124 by sandwiching an insulating material (e.g., a sheet of insulating resin) between the outer current lead 114c and the heat shield 124 or a heat transfer component.

[0033] An inner current lead 114d is disposed inside the heat shield 124, and connects the outer current lead 114c to the superconducting coil 112. The inner current lead 114d can also be a high-temperature superconducting current lead made of, for example, a copper oxide superconductor or other high-temperature superconducting material. The high-temperature end of the inner current lead 114d connected to the outer current lead 114c is thermally connected to the heat shield 124 and is cooled to a first cooling temperature, similar to the heat shield 124. The low-temperature end of the inner current lead 114d connected to the superconducting coil 112 is cooled to a second cooling temperature, similar to the superconducting coil 112.

[0034] Figure 2 and Figure 3 It schematically shows that it can be mounted on Figure 1 The diagram shows the cryogenic refrigerator 10 of the superconducting magnet device 100. Figure 2 The appearance and schematic block diagram of the cryogenic refrigerator 10 are shown. Figure 3 The internal structure of the cryogenic refrigerator 10 is shown. The cryogenic refrigerator 10 is exemplified as a two-stage Gifford-McMahon (GM) refrigerator.

[0035] The cryogenic refrigerator 10 includes a compressor 12 and an expander 14. The compressor 12 is configured to recover the working gas of the cryogenic refrigerator 10 from the expander 14, pressurize the recovered working gas, and supply the working gas back to the expander 14. The working gas is also called the refrigerant gas, which is usually helium, but other suitable gases may also be used.

[0036] Furthermore, the pressure of the working gas supplied from compressor 12 to expander 14 and the pressure of the working gas returned from expander 14 to compressor 12 are typically much higher than atmospheric pressure, and can be referred to as the first high pressure and the second high pressure, respectively. For ease of explanation, the first high pressure and the second high pressure are also simply referred to as high pressure and low pressure, respectively. Typically, the high pressure is, for example, 2 to 3 MPa. The low pressure is, for example, 0.5 to 1.5 MPa, for example, about 0.8 MPa. For ease of understanding, arrows are used to indicate the flow direction of the working gas.

[0037] The compressor 12 has a compressor body 22 and a compressor frame 23 that houses the compressor body 22. The compressor 12 is also referred to as a compressor unit.

[0038] The compressor body 22 is configured to internally compress the working gas drawn in from its inlet and discharge it from its outlet. The compressor body 22 can be, for example, a scroll pump, a rotary pump, or another pump that pressurizes the working gas. The compressor body 22 can be configured to discharge a constant flow rate of working gas. Alternatively, the compressor body 22 can be configured to allow a variable flow rate of the working gas to be discharged. The compressor body 22 is also referred to as a compression chamber.

[0039] Furthermore, the compressor 12 includes a compressor motor 24 and a compressor inverter 25 that controls the operating frequency (speed) of the compressor motor 24. The compressor motor 24 is the drive source for driving the compressor body 22, and is, for example, an electric motor driven by three-phase AC power. The compressor inverter 25 is configured to convert the AC power input from the power supply 46 into AC power of a different frequency, and supply the converted AC power to the compressor motor 24. The power supply 46 can be an external power source such as commercial power (three-phase AC power). The operating frequency of the compressor motor 24 can be controlled by the compressor inverter 25 within the range of 30Hz to 100Hz or within the range of 40Hz to 70Hz.

[0040] It is known that the compressor 12 may have various other components not shown. For example, an oil separator, an adsorber, etc., may be provided in the working gas flow path on the discharge side. Other components such as a storage tank may be provided in the working gas flow path on the suction side. Furthermore, the compressor 12 may be equipped with an oil circulation system that uses oil to cool the compressor body 22, or a cooling system that uses cooling water to cool the oil, etc.

[0041] Expander 14 includes expander cylinder 16 and displacer assembly 18. Expander cylinder 16 guides the linear reciprocating motion of displacer assembly 18 and forms expansion chambers (32, 34) for working gas between expander cylinder 16 and displacer assembly 18. Expander 14 also includes pressure switching valve 40, which determines the start timing of intake of working gas into expansion chamber and the start timing of exhaust of working gas from expansion chamber.

[0042] In this specification, for ease of explanation regarding the positional relationships between the constituent components of the cryogenic refrigerator 10, the side closer to the top dead center of the axial reciprocating movement of the displacement device is labeled "upper," and the side closer to the bottom dead center is labeled "lower." The top dead center is the position where the displacement device has the largest volume of the expansion space, and the bottom dead center is the position where the displacement device has the smallest volume of the expansion space. During operation of the cryogenic refrigerator 10, a temperature gradient is generated from axial upward to downward; therefore, the upper side can also be referred to as the high-temperature side, and the lower side as the low-temperature side.

[0043] The expander cylinder 16 includes a first cylinder 16a and a second cylinder 16b. As an example, the first cylinder 16a and the second cylinder 16b are cylindrical components, with the diameter of the second cylinder 16b being smaller than the diameter of the first cylinder 16a. The first cylinder 16a and the second cylinder 16b are coaxially arranged, and the lower end of the first cylinder 16a is rigidly connected to the upper end of the second cylinder 16b.

[0044] The displacement assembly 18 includes a first displacement 18a and a second displacement 18b connected together, which move integrally. As an example, the first displacement 18a and the second displacement 18b are cylindrical components, with the diameter of the second displacement 18b being smaller than the diameter of the first displacement 18a. The first displacement 18a and the second displacement 18b are coaxially arranged.

[0045] The first displacement device 18a is housed in the first cylinder 16a, and the second displacement device 18b is housed in the second cylinder 16b. The first displacement device 18a can reciprocate axially along the first cylinder 16a, and the second displacement device 18b can reciprocate axially along the second cylinder 16b.

[0046] like Figure 3As shown, the first displacement device 18a houses the first cold storage device 26. The first cold storage device 26 is formed by filling the cylindrical main body of the first displacement device 18a with a metal wire mesh, such as copper, or other suitable first cold storage material. The upper and lower cover portions of the first displacement device 18a can be provided as separate parts from the main body of the first displacement device 18a. The upper and lower cover portions of the first displacement device 18a are fixed to the main body by suitable methods such as fastening or welding, thereby accommodating the first cold storage material in the first displacement device 18a.

[0047] Similarly, the second displacement device 18b houses the second cold storage device 28. The second cold storage device 28 is formed by filling the cylindrical main body of the second displacement device 18b with a non-magnetic cold storage material such as bismuth, a magnetic cold storage material such as HoCu2, or other suitable second cold storage material. The second cold storage material can be formed in granular form. The upper and lower cover portions of the second displacement device 18b can be provided as separate parts from the main body of the second displacement device 18b, and the upper and lower cover portions of the second displacement device 18b can also be fixed to the main body by suitable methods such as fastening or welding, thereby accommodating the second cold storage material in the second displacement device 18b.

[0048] The displacement assembly 18 forms an upper chamber 30, a first expansion chamber 32, and a second expansion chamber 34 inside the expander cylinder 16. For heat exchange with the object or medium to be cooled by the cryogenic refrigerator 10, the expander 14 includes a first cooling platform 33 and a second cooling platform 35. The upper chamber 30 is formed between the upper cover of the first displacement unit 18a and the upper part of the first cylinder 16a. The first expansion chamber 32 is formed between the lower cover of the first displacement unit 18a and the first cooling platform 33. The second expansion chamber 34 is formed between the lower cover of the second displacement unit 18b and the second cooling platform 35. The first cooling platform 33 is fixed to the lower part of the first cylinder 16a surrounding the first expansion chamber 32, and the second cooling platform 35 is fixed to the lower part of the second cylinder 16b surrounding the second expansion chamber 34. The first cooling platform 33 and the second cooling platform 35 are made of, for example, pure copper (e.g., oxygen-free copper, tough copper, etc.) or other metals with high thermal conductivity.

[0049] The first regenerator 26 is connected to the upper chamber 30 via a working gas flow path 36a formed on the upper cover of the first displacement device 18a, and is connected to the first expansion chamber 32 via a working gas flow path 36b formed on the lower cover of the first displacement device 18a. The second regenerator 28 is connected to the first regenerator 26 via a working gas flow path 36c formed from the lower cover of the first displacement device 18a to the upper cover of the second displacement device 18b. Furthermore, the second regenerator 28 is connected to the second expansion chamber 34 via a working gas flow path 36d formed on the lower cover of the second displacement device 18b.

[0050] A first seal 38a and a second seal 38b may be provided to guide the working gas between the first expansion chamber 32, the second expansion chamber 34 and the upper chamber 30 to the first accumulator 26 and the second accumulator 28, instead of the gap between the expander cylinder 16 and the displacement assembly 18. The first seal 38a may be installed on the upper cover of the first displacement unit 18a in a manner that is disposed between the first displacement unit 18a and the first cylinder 16a. The second seal 38b may be installed on the upper cover of the second displacement unit 18b in a manner that is disposed between the second displacement unit 18b and the second cylinder 16b.

[0051] like Figure 2 As shown, the expander 14 includes an expander housing 20 that houses the pressure switching valve 40. The expander housing 20 is combined with the expander cylinder 16, thereby forming an airtight container that houses the pressure switching valve 40 and the displacement assembly 18. The expander housing 20 and the expander cylinder 16 are made of, for example, stainless steel or other suitable high-strength materials to withstand internal and external pressure differences as airtight containers.

[0052] like Figure 3 As shown, the pressure switching valve 40 includes a high-pressure valve 40a and a low-pressure valve 40b, and is configured to generate periodic pressure fluctuations within the expander cylinder 16. The working gas outlet of the compressor 12 is connected to the upper chamber 30 via the high-pressure valve 40a, and the working gas inlet of the compressor 12 is connected to the upper chamber 30 via the low-pressure valve 40b. The high-pressure valve 40a and the low-pressure valve 40b are configured to selectively and alternately open and close (i.e., one is open when the other is closed).

[0053] The pressure switching valve 40 can be a rotary valve. That is, the pressure switching valve 40 can be configured to alternately open and close the high-pressure valve 40a and the low-pressure valve 40b by rotating and sliding the valve disc relative to the stationary valve body. In this case, the expander motor 42 can be connected to the pressure switching valve 40 to rotate the valve disc of the pressure switching valve 40. For example, the pressure switching valve 40 can be configured such that the valve rotation axis is coaxial with the rotation axis of the expander motor 42.

[0054] Alternatively, the high-pressure valve 40a and the low-pressure valve 40b can be valves that can be controlled separately. In this case, the pressure switching valve 40 may not be connected to the expander motor 42.

[0055] Expander 14 includes expander motor 42 and motion conversion mechanism 43. Expander motor 42 is the drive source for expanding expander 14, such as a three-phase AC electric motor. Expander motor 42 is mounted in expander housing 20. Motion conversion mechanism 43, like pressure switching valve 40, is housed in expander housing 20.

[0056] The expander motor 42 is connected to the displacement drive shaft 44 via a motion conversion mechanism 43, such as a Scottish yoke mechanism. The motion conversion mechanism 43 converts the rotational motion output by the expander motor 42 into the linear reciprocating motion of the displacement drive shaft 44. The displacement drive shaft 44 extends from the motion conversion mechanism 43 into the upper chamber 30 and is fixed to the upper cover of the first displacement unit 18a. The rotation of the expander motor 42 is converted into the axial reciprocating movement of the displacement drive shaft 44 by the motion conversion mechanism 43, and the displacement unit assembly 18 reciprocates axially linearly within the expander cylinder 16.

[0057] Furthermore, the cryogenic refrigerator 10 is equipped with an expander inverter 45 that controls the operating frequency, i.e., the speed, of the expander motor 42. In this example, the expander inverter 45 is mounted on the compressor 12, but it is not limited to this and can also be mounted on the expander 14. The expander inverter 45 is configured to convert the AC power input from the power source 46 into AC power of a different frequency, and supply the converted AC power to the expander motor 42. The operating frequency of the expander motor 42 can be controlled by the expander inverter 45 within the range of 30Hz to 100Hz or within the range of 40Hz to 70Hz.

[0058] Furthermore, a first temperature sensor 130a for measuring the first cooling temperature and a second temperature sensor 130b for measuring the second cooling temperature can be provided.

[0059] The first temperature sensor 130a can be configured to measure the temperature of any part of the superconducting magnet device 100 that has been cooled to a first cooling temperature. For example, as Figure 2 As shown, the first temperature sensor 130a can be mounted on the first cooling platform 33. Alternatively, as... Figure 1 As shown, the first temperature sensor 130a can be mounted on a portion of the current lead 114 that is cooled to a first cooling temperature (e.g., the high-temperature end of the inner current lead 114d or the low-temperature end of the outer current lead 114c). The first temperature sensor 130a can be mounted on the thermal shield 124.

[0060] The second temperature sensor 130b can be configured to measure the temperature of any part of the superconducting magnet device 100 that is cooled to the second cooling temperature. For example, as Figure 2 As shown, the second temperature sensor 130b can be mounted on the second cooling platform 35. Alternatively, as... Figure 1 As shown, the second temperature sensor 130b can be mounted on the superconducting coil 112 or the heat transfer component 126.

[0061] The first temperature sensor 130a and the second temperature sensor 130b are respectively connected to the controller 140 via wired or wireless means, and are able to transmit information representing the measured temperature to the controller 140. A first temperature signal T1, representing the first cooling temperature, measured by the first temperature sensor 130a, can be input to the controller 140 from the first temperature sensor 130a. A second temperature signal T2, representing the second cooling temperature, measured by the second temperature sensor 130b, can be input to the controller 140 from the second temperature sensor 130b.

[0062] The status monitoring sensor 132 is configured to measure status parameters associated with the superconducting magnet device 100. These status parameters can be associated with the superconducting coil device 110 or with the cryogenic device 120. The status parameters associated with the superconducting coil device 110 can be excitation status parameters representing the excitation state of the superconducting coil device 110.

[0063] In this embodiment, the state monitoring sensor 132 can measure the current flowing to the superconducting coil 112 through the current lead-in line 114 as an excitation state parameter. That is, the state monitoring sensor 132 can be a current sensor that measures the excitation current supplied to the superconducting coil 112. Figure 1 As shown, the status monitoring sensor 132 can be located on the excitation power supply 116 to measure the excitation current flowing to the superconducting coil 112. Alternatively, the status monitoring sensor 132 can be located on the current feed line 114 (e.g., external wiring 114a) and measure the excitation current flowing to the superconducting coil 112.

[0064] Since the strength of the magnetic field generated by the superconducting coil 112 is approximately linearly related to the excitation current flowing through the superconducting coil 112, the state monitoring sensor 132 can measure the magnetic field (e.g., magnetic flux density) generated by the superconducting coil 112 as an excitation state parameter. This magnetic field sensor can be configured at any location within the region where the superconducting coil 112 generates the magnetic field. For example, the magnetic field sensor can be configured outside the vacuum container 122, such as mounted on the outer surface of the vacuum container 122. Alternatively, the magnetic field sensor can be configured inside the vacuum container 122, such as mounted on or near the superconducting coil 112.

[0065] The status monitoring sensor 132 is connected to the controller 140 via wired or wireless means and can transmit information representing the measured status parameters to the controller 140. The status signal S representing the status parameters measured by the status monitoring sensor 132 can be input from the status monitoring sensor 132 to the controller 140.

[0066] The superconducting coil device 110 can operate in multiple operating modes. These multiple operating modes differ in terms of the excitation state of the superconducting coil device 110. The multiple operating modes can include four operating modes: zero magnetic field mode, excitation scanning mode, steady-state excitation mode, and demagnetization scanning mode.

[0067] The zero-magnetic-field mode refers to the stopped state of the superconducting coil device 110, that is, the state in which no excitation current is supplied to the superconducting coil 112. Therefore, in the zero-magnetic-field mode, the superconducting coil 112 does not generate a magnetic field.

[0068] The excitation scanning mode is used when the superconducting magnet device 100 is started. In excitation scanning mode, an excitation current is supplied from the excitation power supply 116 to the superconducting coil 112 via the current feed line 114, thereby generating a magnetic field in the superconducting coil 112 corresponding to the excitation current. The excitation power supply 116 can increase the excitation current from zero to a target current value according to a predetermined current increase rate (e.g., a constant current increase rate). The target current value can be the rated current value of the superconducting coil 112.

[0069] Steady-state excitation mode refers to the operating state of the superconducting coil device 110, that is, the excitation current flowing to the superconducting coil 112 is maintained at the target current value. In steady-state excitation mode, the excitation power supply 116 can maintain the excitation current at the rated current value.

[0070] The demagnetizing scan mode is used when the superconducting magnet device 100 is not in operation. In the demagnetizing scan mode, the excitation power supply 116 can reduce the excitation current of the superconducting coil 112 from a target current value to zero at a predetermined current reduction rate (e.g., a constant current reduction rate).

[0071] The controller 140 is configured to operate the superconducting coil device 110 in a selected operating mode from a variety of operating modes. The controller 140 can receive input indicating the operating mode to be executed and select that operating mode from a variety of operating modes. Such input can be from a user of the superconducting magnet device 100 to the controller 140, or from a host system including the superconducting magnet device 100 to the controller 140. Alternatively, the controller 140 can autonomously select the operating mode to be executed, for example, based on state parameters associated with the superconducting magnet device 100. The controller 140 can be configured to control the excitation power supply 116 to operate the superconducting coil device 110 in the selected operating mode.

[0072] Furthermore, the controller 140 is configured to provide temperature regulation control for the superconducting magnet device 100. Therefore, the controller 140 is configured to determine the operating parameters of the cryogenic refrigerator 10 based on a comparison between the cooling temperature of the superconducting coil device 110 or the cryogenic refrigerator 10 (from the temperature sensor 130, such as the measured temperature of the first temperature sensor 130a or the second temperature sensor 130b) and the target temperature value, and to operate the cryogenic refrigerator 10 using the determined operating parameters.

[0073] For example, controller 140 can be configured to determine a temperature error based on a comparison between the measured temperature from temperature sensor 130 and a target temperature value, and to determine the operating parameters of the cryogenic refrigerator 10 based on the temperature error. Controller 140 may have a feedback control system that determines the operating parameters of the cryogenic refrigerator 10 in a manner that reduces or minimizes the temperature error. Regarding the cryogenic refrigerator 10, the larger its operating parameters, the higher its output cooling capacity; therefore, the larger the temperature error, the larger the determined operating parameters, and vice versa.

[0074] During operation of the superconducting magnet device 100, the target temperature value can be set to a constant value. Alternatively, the target temperature value can be changed during operation of the superconducting magnet device 100. For example, the controller 140 can set different target temperature values ​​according to the selected operating mode. In this way, the changes in the heat generation of the superconducting coil 112 due to changes in the operating mode can be effectively addressed.

[0075] For example, when the excitation current varies (e.g., in excitation scanning mode or demagnetization scanning mode), the heat generated by the superconducting coil 112 may increase compared to when the excitation current remains constant (e.g., in zero-field mode or steady-state excitation mode). One reason for this is that, for example, during excitation or demagnetization, AC losses may cause the superconducting coil 112 to heat up and its temperature to rise. AC losses are caused by the rate of change of the excitation current flowing to the superconducting coil 112 (in other words, the magnetic field generated by the superconducting coil 112). Furthermore, during excitation or demagnetization, stick-slip may sometimes occur due to the deformation of the superconducting coil 112. Due to this mechanical disturbance, instantaneous heating may be locally generated inside the superconducting coil 112.

[0076] Therefore, the controller 140 can set the target temperature value used in operating modes where the excitation current varies (e.g., excitation scan mode, demagnetization scan mode) to be lower than the target temperature value used in operating modes where the excitation current remains constant (e.g., zero magnetic field mode, steady-state excitation mode). In this way, the temperature rise of the superconducting coil 112 in operating modes where the excitation current varies can be suppressed, and the risk of quench loss (loss of superconductivity) can be reduced.

[0077] The operating parameters of the cryogenic refrigerator 10 can be the operating frequency of the compressor motor 24 or the operating frequency of the expander motor 42. The controller 140 can be configured to generate a compressor command signal B1 representing the operating frequency of the compressor motor 24 based on a comparison between the measured temperature from the temperature sensor 130 and a target temperature value, and output this signal to the compressor inverter 25. The compressor inverter 25 can drive the compressor motor 24 at the operating frequency of the command signal B1. Furthermore, the controller 140 can be configured to generate an expander command signal B2 representing the operating frequency of the expander motor 42 based on a comparison between the measured temperature from the temperature sensor 130 and a target temperature value, and output this signal to the expander inverter 45. The expander inverter 45 can drive the expander motor 42 at the operating frequency of the command signal B2.

[0078] Details will be described later. The cryogenic refrigerator monitor 142 is configured to acquire the values ​​of the operating parameters of the cryogenic refrigerator 10 determined by the controller 140 when the superconducting coil device 110 is running in the selected operating mode, and to diagnose the cryogenic refrigerator 10 based on the acquired values ​​of the operating parameters.

[0079] The internal structure of the control device 138 (e.g., controller 140, cryogenic refrigerator monitor 142) is implemented in terms of hardware structure by elements or circuits, represented by a computer's CPU or memory, and in terms of software structure by computer programs, but is appropriately depicted in the figures as functional modules implemented through their cooperation. Those skilled in the art will understand that these functional modules can be implemented in various forms through a combination of hardware and software.

[0080] For example, the control device 138 (e.g., controller 140, cryogenic refrigerator monitor 142) can be implemented as a combination of a processor (hardware) such as a CPU (Central Processing Unit) or a microcomputer and a software program executed by the processor (hardware). Such a hardware processor can be, for example, a programmable logic device such as a FPGA (Field Programmable Gate Array), or a control circuit such as a Programmable Logic Controller (PLC). The software program can be a computer program used to enable the control device 138 to perform control of the superconducting magnet device 100 or diagnostics of the cryogenic refrigerator 10.

[0081] like Figure 1 and Figure 2As shown, the control device 138 can also be configured separately from the excitation power supply 116 of the superconducting magnet device 100 and the cryogenic refrigerator 10. Alternatively, the control device 138 can be assembled in the excitation power supply 116. Alternatively, the control device 138 can be mounted on a component of the cryogenic refrigerator 10 (e.g., compressor 12 or expander 14). Alternatively, the control device 138 can be remotely configured relative to and communicatively connected to the superconducting magnet device 100 and the cryogenic refrigerator 10.

[0082] Furthermore, in the illustrated example, the cryogenic chiller monitor 142 is integrated into the control unit 138 (e.g., controller 140), but other configurations are possible. For example, the cryogenic chiller monitor 142 can be remotely configured relative to the controller 140, for example, by communicating with the controller 140 via the Internet or other suitable communication networks.

[0083] With the above structure, during the operation of the compressor 12 and expander motor 42, the cryogenic refrigerator 10 generates periodic volume changes and synchronous pressure changes of the working gas in the first expansion chamber 32 and the second expansion chamber 34. Typically, during the suction process, with the low-pressure valve 40b closed and the high-pressure valve 40a open, high-pressure working gas flows from the compressor 12 into the upper chamber 30 through the high-pressure valve 40a, and is supplied to the first expansion chamber 32 through the first accumulator 26, and to the second expansion chamber 34 through the second accumulator 28. Thus, the first expansion chamber 32 and the second expansion chamber 34 are pressurized from low pressure to high pressure. At this time, the displacement assembly 18 moves from the bottom dead center to the top dead center, thereby increasing the volume of the first expansion chamber 32 and the second expansion chamber 34. If the high-pressure valve 40a closes, the suction process ends.

[0084] During the exhaust process, with the high-pressure valve 40a closed and the low-pressure valve 40b open, the high-pressure first expansion chamber 32 and second expansion chamber 34 open to the low-pressure working gas inlet of the compressor 12. Therefore, the working gas expands in the first expansion chamber 32 and second expansion chamber 34, resulting in the low-pressure working gas being discharged from the first expansion chamber 32 and second expansion chamber 34 through the first accumulator 26 and second accumulator 28 to the upper chamber 30. At this time, the displacement assembly 18 moves downward from the top dead center to the bottom dead center, thereby reducing the volume of the first expansion chamber 32 and second expansion chamber 34. The working gas is recovered from the expander 14 to the compressor 12 through the low-pressure valve 40b. If the low-pressure valve 40b is closed, the exhaust process ends.

[0085] Thus, a cooling cycle, such as the GM cycle, is formed, and the first cooling stage 33 and the second cooling stage 35 are cooled to the desired ultra-low temperature. The first cooling stage 33 can be cooled to a first cooling temperature in the range of about 30K to about 70K, for example. A portion of the current lead 114 thermally connected to the first cooling stage 33 (e.g., the low-temperature end of the outer current lead 114c and the high-temperature end of the inner current lead 114d) and the thermal shield 124 are also cooled to the first cooling temperature. The second cooling stage 35 can be cooled to a second cooling temperature lower than the first cooling temperature (e.g., about 1K to about 4K). The superconducting coil 112 is cooled to the second cooling temperature by the second cooling stage 35.

[0086] Thus, the cryogenic refrigerator 10 can cool the superconducting coil 112 below the critical temperature, and the superconducting magnet device 100 can enable the superconducting coil device 110 to operate in an operating mode selected from a variety of operating modes.

[0087] Figure 4 This is a diagram schematically illustrating exemplary operation of the superconducting magnet device 100 according to an embodiment. Figure 4 The diagram illustrates the state parameters of the superconducting magnet device 100 during normal operation and the operating parameters of the cryogenic refrigerator 10. Figure 4 The upper part, as an example of the operating parameters of the cryogenic refrigerator 10, shows the operating frequency f of the compressor 12. comp Changes over time. Figure 4 The lower part, as an example of the state parameters of the superconducting magnet device 100, shows the magnetic field B generated by the superconducting coil 112. mag Changes over time.

[0088] In the operation of the illustrated superconducting magnet device 100, the operating mode switches sequentially over time: zero magnetic field mode, excitation scanning mode, steady-state excitation mode, demagnetization scanning mode, and zero magnetic field mode. Therefore, as... Figure 4 As shown in the lower part, magnetic field B mag The value is zero in zero magnetic field mode, increases from zero to a certain value in excitation scan mode, maintains that value in steady-state excitation mode, and decreases to zero in demagnetization scan mode.

[0089] The target temperature value for cooling the superconducting coil 112 can be set for each operating mode. For example, as mentioned above, the target temperature values ​​for excitation scanning mode and demagnetization scanning mode can be lower than the target temperature values ​​for zero magnetic field mode and steady-state excitation mode. Therefore, the operating frequency f of the compressor 12... compThe larger values ​​(e.g., approximately 60 Hz) are used in the excitation and demagnetization scanning modes, and the smaller values ​​(e.g., approximately 30 Hz in zero magnetic field mode and approximately 35 Hz in steady-state excitation mode) are used in the zero magnetic field mode and steady-state excitation mode. Similarly, the operating frequency of the expander 14 is also related to the operating frequency f of the compressor 12. comp Similar changes occur, with increases and decreases.

[0090] Alternatively, the target temperature value can be set to a constant value independent of the operating mode. As mentioned above, when the excitation current varies (e.g., in excitation scanning mode or demagnetization scanning mode), the heat generated by the superconducting coil 112 may increase compared to when the excitation current remains constant (e.g., in zero-field mode or steady-state excitation mode). Therefore, in this case, as... Figure 4 As shown, the operating parameters of the cryogenic refrigerator 10 can take larger values ​​in the excitation scanning mode and demagnetization scanning mode, and smaller values ​​in the zero magnetic field mode and steady-state excitation mode.

[0091] Thus, the operating parameters of the cryogenic cryostat 10 will change to different values ​​when the operating mode of the superconducting coil device 110 changes, but will remain at a specific value corresponding to that operating mode during operation within the same operating mode. Furthermore, shortly after switching from one operating mode to another, the operating parameters may change significantly due to the transient response, but... Figure 4 For simplicity, this transition response has been omitted.

[0092] As mentioned at the beginning of this article, a method is known to monitor the performance degradation of a cryogenic refrigerator over time by monitoring its cooling temperature. In this method, an increase in cooling temperature is considered a decrease in the refrigeration performance of the cryogenic refrigerator. This may be effective in conventional cryogenic refrigerators without inverter control. In cryogenic refrigerators without inverters, since the motor is driven at a constant operating frequency, a decrease in refrigeration performance directly leads to an increase in cooling temperature.

[0093] The inventors realized that this diagnostic method based on cooling temperature is not necessarily effective for cryogenic refrigerators equipped with frequency converters (e.g., cryogenic refrigerator 10). This is because, in cryogenic refrigerator 10, even if the cooling performance decreases to a certain extent, it is compensated for by increasing operating parameters under temperature regulation control, thus maintaining the cooling temperature at the target value. Only when the cryogenic refrigerator 10 deteriorates or malfunctions to the point that temperature regulation control becomes ineffective will the cooling temperature significantly deviate from the target value. That is, in cryogenic refrigerators equipped with frequency converters, it is difficult to detect faults or their symptoms by monitoring the cooling temperature and take preventative measures, thus making it difficult to minimize the impact on the operation of the superconducting magnet device.

[0094] In this embodiment, as described above, the controller 140 is configured to determine the operating parameters of the cryogenic refrigerator 10 based on a comparison between the cooling temperature of the superconducting coil device 110 or the cryogenic refrigerator 10 and a target temperature value, and to drive the cryogenic refrigerator 10 using the determined operating parameters. Therefore, a decrease in the performance of the cryogenic refrigerator 10 will lead to an increase in the operating parameters of the cryogenic refrigerator 10.

[0095] Therefore, in this embodiment, the cryogenic refrigerator monitor 142 is configured to acquire the values ​​of the operating parameters of the cryogenic refrigerator 10 determined by the controller 140 when the superconducting coil device 110 is running in the selected operating mode, and to diagnose the cryogenic refrigerator 10 based on the acquired values ​​of the operating parameters.

[0096] For reference Figure 4 The operating parameters of the cryogenic refrigerator 10 will be maintained at a specific value corresponding to the operating mode during normal operation of the superconducting coil device 110 in the same operating mode. Therefore, if the operating parameters of the superconducting coil device 110 increase relative to the reference value of the operating parameters of that operating mode when it is operating in a certain operating mode, it can be determined that the cooling performance of the cryogenic refrigerator 10 has decreased compared with the normal state.

[0097] Thus, the cryogenic refrigerator 10 can be diagnosed based on the values ​​of its operating parameters in the selected operating mode of the superconducting coil device 110. By detecting performance degradation of the cryogenic refrigerator 10 and performing preventative maintenance (e.g., repair, replacement) on the cryogenic refrigerator 10, sudden failures of the cryogenic refrigerator 10 can be prevented in advance, and the impact on the operation of the superconducting magnet device 100 can be minimized. The exemplary diagnostic method involved in the embodiments is described below.

[0098] Figure 5 This is a flowchart illustrating an example of a diagnostic method for the cryogenic refrigerator 10 according to an embodiment. The cryogenic refrigerator monitor 142 can perform this diagnostic process in response to a switch in the operating mode of the superconducting coil device 110. The cryogenic refrigerator monitor 142 can acquire operating mode information representing the operating mode selected from multiple operating modes of the superconducting coil device 110, and detect a switch in the operating mode based on the operating mode information. The operating mode information is generated by the controller 140, and the cryogenic refrigerator monitor 142 can acquire the operating mode information from the controller 140. Alternatively, the cryogenic refrigerator monitor 142 can acquire measured values ​​of the state parameters of the superconducting magnet device 100 (e.g., excitation state parameters representing the excitation state of the superconducting coil device 110) from the state monitoring sensor 132, and detect a switch in the operating mode based on these values.

[0099] Alternatively, the cryogenic chiller monitor 142 can perform diagnostic procedures at any time (e.g., periodically) regardless of changes in operating mode.

[0100] like Figure 5 As shown, when the diagnostic process begins, the cryogenic refrigerator monitor 142 determines whether the superconducting magnet device 100 is in a stable state (S10). The cryogenic refrigerator monitor 142 can determine whether the superconducting magnet device 100 is in a stable state based on the state parameters of the superconducting magnet device 100.

[0101] For example, the state parameter could be the time elapsed since the operating mode switch. This is because the transitional state accompanying the operating mode switch converges over time. Therefore, the cryogenic refrigerator monitor 142 can determine whether a predetermined time has elapsed since the start of the selected operating mode. If the predetermined time has not elapsed, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is not in a stable state (i.e., in a transitional state). If the predetermined time has elapsed, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is in a stable state. The predetermined time used for determination can be appropriately set based on the designer's experience or through experiments or simulations conducted by the designer. This predetermined time can be set to different values ​​for different operating modes.

[0102] The state parameter can be the cooling temperature of the superconducting coil device 110 (e.g., superconducting coil 112 or thermal shield 124) or the cryogenic refrigerator 10 (e.g., the second cooling stage 35 or the first cooling stage 33). The cryogenic refrigerator monitor 142 can determine whether the cooling temperature is below a temperature threshold. If the cooling temperature exceeds the temperature threshold, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is not in a stable state. If the cooling temperature is below the temperature threshold, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is in a stable state. The temperature threshold can be appropriately set based on the designer's experience or through experiments or simulations conducted by the designer. The temperature threshold can be set to different values ​​for different operating modes.

[0103] The state parameter can be the rate of change of the cooling temperature over time for the superconducting coil device 110 or the cryogenic refrigerator 10. The cryogenic refrigerator monitor 142 can determine whether the rate of change of the cooling temperature over time is below a threshold. If the rate of change of the cooling temperature over time exceeds the threshold, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is not in a steady state. If the rate of change of the cooling temperature over time is below the threshold, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is in a steady state. The threshold for the rate of change of time can be appropriately set based on the designer's experience or through experiments or simulations conducted by the designer. The temperature threshold can be set to different values ​​for different operating modes.

[0104] The state parameter can be the time-varying rate of change of the operating parameters of the cryogenic refrigerator 10. The cryogenic refrigerator monitor 142 can determine whether the time-varying rate of change of the operating parameters is below a threshold. If the time-varying rate of change of the operating parameters exceeds the threshold, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is not in a stable state. If the time-varying rate of change of the operating parameters is below the threshold, the cryogenic refrigerator monitor 142 determines that the superconducting magnet device 100 is in a stable state. The threshold for the time-varying rate can be appropriately set based on the designer's experience or through experiments or simulations conducted by the designer. The temperature threshold can be set to different values ​​for different operating modes.

[0105] If the superconducting magnet device 100 is not in a stable state (S10 "No"), the cryogenic refrigerator monitor 142 will not perform a diagnosis of the cryogenic refrigerator 10, but will determine whether the superconducting magnet device 100 is in a stable state again at the next opportune time (S10). In this way, the cryogenic refrigerator monitor 142 will standby until the superconducting magnet device 100 becomes a stable state.

[0106] If the superconducting magnet device 100 is in a stable state (S10 "Yes"), the cryogenic refrigerator monitor 142 acquires the values ​​of the operating parameters of the cryogenic refrigerator 10 (e.g., the operating frequency of the compressor 12) determined by the controller 140 (S11). Therefore, the cryogenic refrigerator monitor 142 can acquire the current values ​​of the operating parameters of the cryogenic refrigerator 10 when the superconducting coil device 110 is operating in the selected operating mode and the superconducting magnet device 100 is in a stable state. This avoids diagnostics during transitional states caused by operating mode switching, thereby reducing the risk of misinterpreting temporary increases in operating parameters during transitional states as a decrease in cooling performance.

[0107] Next, the cryogenic refrigerator monitor 142 performs a diagnostic test on the cryogenic refrigerator 10 by comparing the acquired operating parameter values ​​with the operating parameter thresholds (S12). During the comparison, the cryogenic refrigerator monitor 142 determines the operating parameter thresholds based on the recorded operating parameter values ​​under the selected operating mode. As described later, the recorded values ​​can be the previous values ​​of the operating parameters acquired during the last diagnostic test under the same operating mode. The previous value of the operating parameter can be used as the threshold. Alternatively, the previous value of the operating parameter plus a predetermined margin can also be used as the threshold. The threshold can be appropriately set based on the designer's experience or through experiments or simulations conducted by the designer.

[0108] The cryogenic refrigerator monitor 142 can determine whether the value of the acquired operating parameter exceeds a threshold. If the value of the acquired operating parameter exceeds the threshold ("Yes" in S12), the cryogenic refrigerator monitor 142 notifies the cryogenic refrigerator 10 of a decrease in cooling performance (S13). The cryogenic refrigerator monitor 142 can notify or warn the cryogenic refrigerator 10 of a decrease in cooling performance through visual, auditory, or other arbitrary notification means.

[0109] If the acquired operating parameter value is below the threshold (S12 "No"), then the cooling performance of the cryogenic refrigerator 10 is considered to be within the normal range, and therefore the cryogenic refrigerator monitor 142 does not notify of a decrease in the cooling performance of the cryogenic refrigerator 10. Alternatively, the cryogenic refrigerator monitor 142 may also notify that the cooling performance of the cryogenic refrigerator 10 is within the normal range.

[0110] The cryogenic chiller monitor 142 records the acquired operating parameter values ​​(S14). As described above, the recorded operating parameter values ​​can be used to determine the operating parameter thresholds to be used the next time a diagnostic is performed under the same operating mode. Thus, this diagnostic process ends.

[0111] Other methods can also be used to determine the threshold values ​​for operating parameters. For example, the cryogenic refrigerator monitor 142 can be configured to select any one of multiple preset values ​​based on the operating mode selected by the superconducting coil device 110, thereby determining the threshold values ​​for the operating parameters. In other words, the threshold values ​​for operating parameters can be preset for each of the multiple operating modes, and the threshold values ​​corresponding to the selected operating mode can be used.

[0112] In the above embodiments, the diagnosis of the cryogenic refrigerator 10 is based on the comparison of the acquired operating parameter values ​​with the threshold values ​​of the operating parameters, but other methods may also be used. The diagnosis of the cryogenic refrigerator 10 may be based on the historical records of operating parameters in the operating mode selected by the superconducting coil device 110.

[0113] Therefore, the cryogenic refrigerator monitor 142 can be configured to update the historical record of operating parameters in the selected operating mode of the superconducting coil device 110 based on the acquired values ​​of operating parameters, and to perform diagnostics on the cryogenic refrigerator 10 based on the updated historical record. The cryogenic refrigerator monitor 142 can replace... Figure 5 S12, for example, determines whether the updated historical records of the cryogenic refrigerator 10 meet predetermined conditions. If the conditions are met, the cryogenic refrigerator monitor 142 can notify that the cooling performance of the cryogenic refrigerator 10 has decreased ( Figure 5 (S13). If the condition is not met, the refrigeration performance of the cryogenic refrigerator 10 can be considered to be within the normal range.

[0114] Figure 6 It is a graph schematically showing the historical records 150 of the operating parameters of the cryogenic refrigerator 10 used for diagnosis of the cryogenic refrigerator 10 involved in the implementation. Figure 6 The vertical axis represents the operating parameters of the cryogenic refrigerator 10, and the horizontal axis represents time. Figure 6 The diagram illustrates the operating parameters of the cryogenic refrigerator 10 under a specific operating mode within various operating modes of the superconducting coil device 110. Specifically, in... Figure 6 The figure shows time-series data of the operating parameters of the cryogenic refrigerator 10 acquired over time for a certain operating mode.

[0115] The cryogenic refrigerator monitor 142 acquires the values ​​of the operating parameters of the cryogenic refrigerator 10 determined by the controller 140 (e.g., Figure 6 Point 152 in the middle) Figure 5 (S11). The cryogenic chiller monitor 142 can update the history of operating parameters 150 by adding the acquired values ​​of operating parameters to the history of operating parameters 150.

[0116] The diagnostic condition could be, for example, that the increase in the acquired operating parameter value (column point 152) relative to the initial value 154 of the operating parameter in the historical record 150 exceeds a threshold. If this increase exceeds the threshold, the cryogenic refrigerator monitor 142 can notify that the cryogenic refrigerator 10 has experienced a decrease in cooling performance. Figure 5 (S13). If the increase is below the threshold, the refrigeration performance of the cryogenic refrigerator 10 can be considered to be within the normal range. Alternatively, the diagnostic condition can be that the value of the acquired operating parameter continuously increases (e.g., the value of the operating parameter is acquired multiple times). If the value of the operating parameter continues to increase, the cryogenic refrigerator monitor 142 can notify that the refrigeration performance of the cryogenic refrigerator 10 has decreased. The diagnostic conditions can be appropriately set based on the designer's experience or through experiments or simulations conducted by the designer.

[0117] As another example of a diagnostic method, the cryogenic refrigerator monitor 142 can be configured to diagnose the cryogenic refrigerator 100 based on statistical analysis of historical operating data of the superconducting magnet device 100. The historical operating data of the superconducting magnet device 100 may include operating parameters of the cryogenic refrigerator 100 and at least one state parameter associated with the superconducting magnet device 100. The state parameter associated with the superconducting magnet device 100 may include an excitation state parameter representing the excitation state of the superconducting coil device 110. The state parameter associated with the superconducting magnet device 100 may be the cooling temperature of the superconducting coil device 110 or the cryogenic refrigerator 10.

[0118] Figure 7 It is a chart schematically illustrating the statistical analysis of the operating history data of the superconducting magnet device 100 used for diagnosis of the cryogenic refrigerator 10 involved in the embodiment. Figure 7 The vertical axis represents the operating parameters of the cryogenic refrigerator 10, and the horizontal axis represents the state parameters related to the superconducting magnet device 100. Here, for simplicity, a statistical analysis of the historical operation data plotted on a plane consisting of one operating parameter and one state parameter is schematically shown. However, it should be understood that statistical analysis of the historical operation data is also possible in a multidimensional space consisting of multiple operating parameters and multiple state parameters.

[0119] By applying multivariate analysis, such as cluster analysis, to the historical operating data of the superconducting magnet device 100, a healthy region 160 can be defined in a multidimensional space with operating parameters and state parameters as variables. The healthy region 160 indicates that the cryogenic refrigerator 10 is functioning normally when the combination of acquired operating parameters and state parameters is contained within this region; this region is a specific area within the multidimensional space. Machine learning can be used to perform this statistical analysis.

[0120] Therefore, the cryogenic refrigerator monitor 142 can determine whether the combination of operating parameters and status parameters obtained from the controller 140 is within the healthy region 160. If it is within the healthy region 160, the cryogenic refrigerator monitor 142 can determine that the cooling performance of the cryogenic refrigerator 10 is within the normal range. If the combination of operating parameters and status parameters deviates from the healthy region 160, the cryogenic refrigerator monitor 142 can notify that the cooling performance of the cryogenic refrigerator 10 has decreased.

[0121] Alternatively, statistical analysis of the historical operating data of the superconducting magnet device 100 can be performed as regression analysis. The cryogenic refrigerator monitor 142 can diagnose the cryogenic refrigerator 10 by comparing the combination of acquired operating parameters and status parameters with the regression equations obtained through statistical analysis.

[0122] Alternatively, the cryogenic refrigerator monitor 142 may have a diagnostic algorithm based on machine learning such as deep learning. The diagnostic algorithm may be configured to take the historical operation data of the superconducting magnet device 100 as input and output a diagnostic result representing the soundness of the cryogenic refrigerator 10 (e.g., the cooling capacity of the cryogenic refrigerator 10).

[0123] The present invention has been described above with reference to embodiments. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various design changes and modifications are possible, 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. New embodiments resulting from combinations possess the effects of each of the combined embodiments.

[0124] In the above embodiments, the case of the cryogenic refrigerator 10 being a GM refrigerator was described as an example, but the present invention is not limited thereto. In one embodiment, the cryogenic refrigerator monitor 142 involved in the embodiment can be applied to other types of cryogenic refrigerators that can be used in the cooling of the superconducting magnet device 100, such as pulse tube refrigerators, GM-JT refrigerators, Stirling refrigerators, etc.

[0125] According to the embodiments, the present invention has been described using specific statements. However, the embodiments are merely one aspect illustrating the principles and applications of the present invention. In the embodiments, many modifications or configuration changes are permitted without departing from the spirit of the present invention.

Claims

1. A superconducting magnet device, characterized in that, have: A superconducting coil device capable of operating in multiple modes; An ultra-low temperature refrigerator is used to cool the superconducting coil device; The controller is configured to operate the superconducting coil device in an operating mode selected from the multiple operating modes, and to determine the operating parameters of the cryogenic refrigerator based on a comparison between the cooling temperature of the superconducting coil device or the cryogenic refrigerator and a target temperature value, and to drive the cryogenic refrigerator using the determined operating parameters. and The cryogenic refrigerator monitor is configured to acquire the values ​​of determined operating parameters of the superconducting coil device when it is running in the selected operating mode, and to diagnose the cryogenic refrigerator based on the acquired operating parameter values.

2. The superconducting magnet device according to claim 1, characterized in that, The cryogenic refrigerator monitor is configured to diagnose the cryogenic refrigerator by comparing the acquired operating parameter values ​​with the threshold values ​​of the operating parameters.

3. The superconducting magnet device according to claim 2, characterized in that, The cryogenic refrigerator monitor is configured to determine the threshold of the operating parameters based on the historical values ​​of the operating parameters of the superconducting coil device in the selected operating mode.

4. The superconducting magnet device according to claim 2, characterized in that, The ultra-low temperature refrigerator monitor is configured to select any one of multiple preset values ​​from the selected operating mode of the superconducting coil device to determine the threshold of the operating parameters.

5. The superconducting magnet device according to claim 1, characterized in that, The cryogenic refrigerator monitor is configured to update the historical records of the operating parameters of the superconducting coil device in the selected operating mode based on the acquired operating parameter values, and to diagnose the cryogenic refrigerator based on the updated historical records.

6. The superconducting magnet device according to any one of claims 2 to 5, characterized in that, The cryogenic refrigerator monitor is configured to acquire the values ​​of the determined operating parameters when the superconducting coil device is operating in the selected operating mode and the superconducting magnet device is in a stable state.

7. The superconducting magnet device according to claim 1, characterized in that, The cryogenic refrigerator monitor is configured to diagnose the cryogenic refrigerator based on statistical analysis of the historical operating data of the superconducting magnet device, which includes the operating parameters and at least one state parameter related to the superconducting magnet device.

8. The superconducting magnet device according to claim 1, characterized in that, The cryogenic refrigeration unit comprises: a compressor equipped with a compressor motor; and an expander equipped with an expander motor. The controller is configured to determine the operating frequency of at least one of the compressor motor and the expander motor based on a comparison between the cooling temperature and the target temperature value, as the operating parameter of the cryogenic refrigerator, and to use the determined operating frequency to drive the cryogenic refrigerator. The cryogenic refrigerator monitor is configured to acquire the value of the determined operating frequency of the superconducting coil device when it is running in the selected operating mode, and to diagnose the cryogenic refrigerator based on the acquired operating frequency value.

9. The superconducting magnet device according to claim 1, characterized in that, The various operating modes differ from one another in terms of the excitation state of the superconducting coil device.

10. A control device for a superconducting magnet device, characterized in that, The superconducting magnet device includes a superconducting coil device capable of operating in multiple operating modes and a cryogenic refrigerator for cooling the superconducting coil device. The control device includes: The controller is configured to operate the superconducting coil device in an operating mode selected from the multiple operating modes, and to determine the operating parameters of the cryogenic refrigerator based on a comparison between the cooling temperature of the superconducting coil device or the cryogenic refrigerator and a target temperature value, and to drive the cryogenic refrigerator using the determined operating parameters. and The cryogenic refrigerator monitor is configured to acquire the values ​​of determined operating parameters of the superconducting coil device when it is running in the selected operating mode, and to diagnose the cryogenic refrigerator based on the acquired operating parameter values.

Images