Cooling system, magnetic field generating device and operation method

Abstract

A cooling system (RS) is provided with a vacuum heat-insulating container (4), an object to be cooled (3), an extremely low temperature refrigerator (CR), a heat conduction connection part (TC), a temperature sensor (TS), current leads (D1, D2), and a control part (PS), and the temperature sensor is configured to detect the temperature of any one of the object to be cooled, a cold stage part, the heat conduction connection part, and the current leads. The control unit is configured to perform: an operation stop process for stopping the operation of the extremely low temperature refrigerator when the temperature detected by the temperature sensor drops to a predetermined target cooling temperature during the operation of the extremely low temperature refrigerator; and an operation start process of starting the operation of the extremely low temperature refrigerator when the temperature detected by the temperature sensor rises to a predetermined operation start temperature higher than the predetermined target cooling temperature during the operation stop of the extremely low temperature refrigerator.

Description

Technical Field The invention relates to a cooling system, a magnetic field generating device and an operating method. This application claims priority based on Tokugan Application No. 2022-167959 filed in Japan on October 19, 2022, the entire contents of which are incorporated herein by reference. Background Art Conventionally, there is a cryogenic refrigerator for cooling a cooling object (for example, Patent Document 1). [Prior art literature] [Patent Document] Patent Document 1: Japanese Patent Application Laid-Open No. 5-312425 Summary of the invention [Technical issues] In a conventional cryogenic refrigerator, since it is always operated at a substantially constant output, even after the temperature of the object to be cooled has sufficiently dropped, the object to be cooled is continuously cooled at the same output, which may cause a waste of driving energy. The present invention is proposed to solve the above-mentioned problems, and its purpose is to provide a cooling system, a magnetic field generating device and an operating method that can reduce the driving energy of a very low temperature refrigerator. [Technical solution]

[0001] A cooling system comprises: a vacuum insulation container; a cooling object arranged in the vacuum insulation container; a cryogenic refrigerator having a cold stage portion configured to generate cooling; a heat conductive connection portion connecting the cold stage portion and the cooling object in a heat conductive manner; one or more temperature sensors; a current lead arranged in the vacuum insulation container; and a control portion, wherein the one or more temperature sensors are configured to respectively detect the temperature of any one of the cooling object, the cold stage portion, the heat conductive connection portion and the current lead, and the control portion is configured to perform the following processing: an operation stop processing, during the operation of the cryogenic refrigerator, when the temperature detected by any one of the temperature sensors drops to a predetermined target cooling temperature, the operation of the cryogenic refrigerator is stopped; and an operation start processing, during the operation stop of the cryogenic refrigerator, when the temperature detected by any one of the temperature sensors rises to a predetermined operation start temperature higher than the predetermined target cooling temperature, the operation of the cryogenic refrigerator is started.

[0002] According to the cooling system described in [1], the predetermined target cooling temperature is equal to or higher than the temperature of the cold stage portion when the cooling load of the cold stage portion reaches 5W.

[0003] According to the cooling system described in [1] or [2], the cooling object is configured to include a high temperature superconducting wire, and the predetermined operation start temperature is equal to or lower than a maximum temperature at which the high temperature superconducting wire can become superconducting.

[0004] According to any one of [1] to [3], the thermally conductive connection portion includes a cold storage body.

[0005] According to the cooling system described in [4], the heat capacity of the cold storage body is larger than the heat capacity of the cooling object.

[0006] According to the cooling system described in [4] or [5], the thermally conductive connection portion has one or more heat-equalizing members, and the one or more heat-equalizing members are in contact with the outer peripheral surface of the cold storage body over the entire circumference.

[0007] According to the cooling system described in [6], the thermally conductive connection portion has one or more cooling conductor components, and the one or more cooling conductor components are in contact with the heat-dissipating component and the cooling target.

[0008] According to the cooling system described in any one of [4] to [7], the cold storage body is a core member, the cooling target is a superconducting coil, and the superconducting coil is wound around the core member.

[0009] According to any one of [4] to [8], the cooling system is configured to be used in a magnetic field generating device, the magnetic field generating device comprising: the cooling system; and a substantially C-shaped or substantially U-shaped yoke, the cooling system comprising one or a pair of the vacuum insulation containers, the cooling system comprising a pair of superconducting coils respectively being the cooling objects, the cooling system comprising a pair of split core portions respectively being the cold storage bodies, the pair of split core portions being separate bodies from the yoke, being located on the inner side of the yoke, and being arranged opposite to each other with a working space therebetween, each of the superconducting coils being wound around each of the split core portions in a circumferential direction centered on an axis parallel to a direction in which the pair of split core portions are opposite to each other, a split core coil assembly comprising the split core portions and the superconducting coils wound around the split core portions being contained in the one or a pair of vacuum insulation containers, and the yoke being arranged outside the one or a pair of vacuum insulation containers.

[0010] A magnetic field generating device, comprising: a cooling system as described in any one of [4] to [8]; and a substantially C-shaped or U-shaped yoke, wherein the cooling system has one or a pair of the vacuum insulation containers, the cooling system has a pair of superconducting coils which are respectively the cooling objects, the cooling system has a pair of split core parts which are respectively the cold storage bodies, the pair of split core parts are formed separately from the yoke, are located on the inner side of the yoke, and are arranged opposite to each other with a working space between them, each of the superconducting coils is wound around each of the split core parts along a circumferential direction centered on an axis parallel to the direction in which the pair of split core parts are opposite to each other, a split core coil assembly having the split core parts and the superconducting coils wound around the split core parts is accommodated in the one or a pair of vacuum insulation containers, and the yoke is arranged outside the one or a pair of vacuum insulation containers.

[0011] An operating method for a cooling system described in any one of [1] to [8], wherein the operating method comprises: an operation stopping step, wherein during the operation of the extremely low temperature refrigerator, when the temperature detected by any one of the temperature sensors drops to a predetermined target cooling temperature, the control unit stops the operation of the extremely low temperature refrigerator; and an operation starting step, wherein during the operation stopping of the extremely low temperature refrigerator, when the temperature detected by any one of the temperature sensors rises to a predetermined operation starting temperature higher than the predetermined target cooling temperature, the control unit starts the operation of the extremely low temperature refrigerator. [Effects of the invention] According to the present invention, a cooling system, a magnetic field generating device, and an operating method capable of reducing the driving energy of a cryogenic refrigerator can be provided. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 1 is a cross-sectional view schematically showing a magnetic field generating device according to an embodiment of the present invention including a cooling system according to an embodiment of the present invention. Figure 2 It is enlarged to show Figure 1 Cross-sectional view of a cooling unit. Figure 3 It is schematically shown Figure 2 A perspective view of a cooling unit. Figure 4 It is schematically shown Figure 3 A three-dimensional view of the cooling unit excluding the vacuum insulation container and the radiation shield. Figure 5 Shown in exploded state Figure 3 An exploded perspective view of a split core-coil assembly. Figure 6 It is enlarged to show Figure 1A cross-sectional view of a portion of a magnetic field generating device. Figure 7 : is a diagram showing an example of a capacity curve of a two-stage cryogenic refrigerator. Figure 8 This is a diagram showing an example of critical current characteristics of a REBCO wire which is one type of high temperature superconducting wire. DETAILED DESCRIPTION The cooling system according to the present invention and the operating method according to the present invention can be used to cool any cooling object, for example, can be suitable for cooling superconducting coils. In addition, the cooling system according to the present invention and the operating method according to the present invention can be used in any device, for example, can be used in a magnetic field generating device. The magnetic field generating device according to the present invention can be used for any purpose, for example, it can be used as a heating device for aluminum billets. Hereinafter, embodiments of a cooling system, a magnetic field generating device, and an operating method according to the present invention will be described by way of example with reference to the accompanying drawings. Figure 1 The magnetic field generating device 1 according to one embodiment of the present invention is shown, which is provided with the cooling system RS according to one embodiment of the present invention. The cooling system RS of this embodiment is configured to be used in the magnetic field generating device 1 . like Figure 1 As shown, the magnetic field generating device 1 of this embodiment comprises a cooling system RS and a yoke 21 according to an embodiment of the present invention. The cooling system RS of this embodiment comprises a pair of cooling units RU and a control unit PS. Each cooling unit RU comprises a vacuum insulation container 4, a cooling object 3, a cryogenic refrigerator CR, a thermal connection part TC, a temperature sensor TS and a radiation shield SH. The cooling system RS of this embodiment (and further, the magnetic field generating device 1) comprises a pair of vacuum insulation containers 4, a pair of cooling objects 3, a pair of cryogenic refrigerators CR, a pair of thermal connection parts TC, a pair of temperature sensors TS and a pair of radiation shields SH. In this embodiment, the thermal connection part TC has one or more (one in this embodiment) heat transfer conductor parts TP, one or more (four in this embodiment) heat equalizing parts SK, one or more (two in this embodiment) cooling conductor parts PM and a cold storage body 22. The cooling system RS of this embodiment (and further, the magnetic field generating device 1) comprises a pair of cold storage bodies 22. Each cooling unit RU is configured to cool the respective cooling object 3 . In the present embodiment, the cooling units RU have the same structure as each other, and therefore, when describing the cooling units RU or their components below, unless otherwise specified, each cooling unit RU will be described separately. In the present embodiment, the cooling target 3 is a superconducting coil 3. Hereinafter, the cooling target 3 may be referred to as a "superconducting coil 3". In addition, in this embodiment, the cold storage body 22 is a core member 22, and is a split core part 22. Hereinafter, the cold storage body 22 may be referred to as a "core member 22" or a "split core part 22". The vacuum insulation container 4 is configured to maintain a vacuum inside. Thus, the vacuum insulation container 4 is configured to keep the temperature of the components inside the vacuum insulation container 4 cooled by the cryogenic refrigerator CR cool. The object to be cooled 3 , a part of the cryogenic refrigerator CR, a heat conductive connection portion TC, a temperature sensor TS, and a radiation shield SH are arranged in the vacuum thermal insulation container 4 . The core 2 is constituted by a yoke 21 and a pair of split core portions 22 (ie, cold storage bodies 22 or core members 22 ). The yoke 21 is made of iron and allows magnetic flux to pass through. The yoke 21 is substantially C-shaped or substantially U-shaped (in Figure 1 In the example of FIG. 2 , the yoke 21 is substantially C-shaped. The yoke 21 has a pair of end portions 21a. Figure 1 In the example, the yoke 21 is oriented with a pair of end portions 21a facing the working space 6. However, as long as the yoke 21 is provided with a surface facing the surface of the split core portion 22 on the axial direction outside ADO with a narrow gap, the end portions 21a of the yoke 21 may be oriented in any direction. The yoke 21 is arranged outside the pair of vacuum insulation containers 4 . The pair of split core parts 22 are made of iron and are configured to allow magnetic flux to pass through. The pair of split core parts 22 are separate from the yoke 21. The pair of split core parts 22 are located inside the yoke 21 and are arranged opposite to each other with the working space 6 interposed therebetween. The working space 6 is an air gap. Thus, the core 2 has a substantially C-shape. In this specification, the direction passing through a pair of split core portions 22 and parallel to the axis O extending in the direction opposite to each other is referred to as the "axial direction AD". In addition, the side close to the working space 6 in the axial direction AD is referred to as the "axial direction inner side ADI", and the side away from the working space 6 in the axial direction AD is referred to as the "axial direction outer side ADO". In addition, the direction perpendicular to the axial direction AD is referred to as the "axial straight direction OD". The side close to the axis O in the axial straight direction OD is referred to as the "axial straight direction inner side", and the side away from the axis O in the axial straight direction OD is referred to as the "axial straight direction outer side". In addition, in this specification, the circumferential direction centered on the axis O is sometimes referred to as the "circumferential direction". In addition, unless otherwise specified, the "outer peripheral side" and the "inner peripheral side" refer to the outer peripheral side and the inner peripheral side when the axis O is the center. In addition, in this specification, a direction perpendicular to the axial direction AD is referred to as "longitudinal direction VD", and directions perpendicular to the axial direction AD and the longitudinal direction VD are referred to as "depth direction DD". In addition, one side in the longitudinal direction VD is referred to as "longitudinal first side VD1", and the other side in the longitudinal direction VD is referred to as "longitudinal second side VD2". In the present embodiment, the longitudinal direction VD is directed in the vertical direction and the longitudinal first side VD1 is directed upward, but the longitudinal direction VD may be directed in any direction. The pair of split core parts 22 and the pair of end parts 21a of the yoke 21 are opposite to each other in the axial direction AD. The pair of split core parts 22 are located at the axial inner side ADI relative to the pair of end parts 21a of the yoke 21. The surfaces of the pair of split core parts 22 at the axial outer side ADO and the surfaces of the pair of yokes 21 at the axial inner side ADI are opposite to each other with a narrow gap. like Figures 1 to 6 As shown in FIG. 1 , the superconducting coil 3 is wound around the split core portion 22. More specifically, the superconducting coil 3 is wound around the split core portion 22 along the circumferential direction centered on the axis O (in other words, around the axis O). The superconducting coil 3 is located on the outer peripheral surface 221 of the split core portion 22 (specifically, on the axial direction surface 2211b of the step portion 2211 described later in the outer peripheral surface 221, Figure 5-6 ), thereby being spaced apart from and facing the outer peripheral surface 221 (specifically, the axial direction surface 2211b) in the radial direction. However, the superconducting coil 3 may also be in contact with the outer peripheral surface 221 (for example, the axial direction surface 2211b) of the split core portion 22. The superconducting coil 3 is configured to include a superconductor, in other words, to include a coil body (superconducting wire) containing a superconductor. The coil body (superconducting wire) of the superconducting coil 3 is preferably a high-temperature superconducting wire. The coil body of the superconducting coil 3 is, for example, configured in a strip shape. In addition to the coil body, the superconducting coil 3 may also include a coil housing that accommodates the coil body inside. The coil housing is, for example, made of resin or the like. like Figure 5 As shown, in this example, the superconducting coil 3 is in a roughly quadrilateral ring shape around the axis O in the cross section in the axial direction OD, but the superconducting coil 3 in the cross section in the axial direction OD can be formed into any ring shape, such as a roughly circular ring shape, a roughly elliptical ring shape, etc., as long as it is a ring shape around the axis O. Although not shown in the drawings, magnetic field generating device 1 includes a current supply unit for causing current (for example, direct current) to flow through superconducting coil 3 . The superconducting coil 3 is cooled by the cryogenic refrigerator CR until the superconducting wire and the superconductor constituting the superconducting coil 3 become superconducting (and further, until the resistance becomes substantially zero). like Figure 1 to Figure 2As shown, the split core portion 22 and the superconducting coil 3 wound around the split core portion 22 constitute a split core coil assembly 5. That is, the split core coil assembly 5 includes the split core portion 22 and the superconducting coil 3 wound around the split core portion 22. In the present embodiment, the cooling system RS (and further, the magnetic field generating device 1) includes a pair of split core coil assemblies 5. In the present embodiment, the split core-coil assembly 5 includes one or more (four in the present embodiment) heat-saturating members SK and one or more (two in the present embodiment) cooling conductor members PM in addition to the split core portions 22 and the superconducting coil 3 . Each split core-coil assembly 5 is housed in each vacuum insulation container 4. The yoke 21 is arranged outside the pair of vacuum insulation containers 4. The pair of vacuum insulation containers 4 face each other in the axial direction AD with the working space 6 interposed therebetween. like Figure 6 As shown, the wall 42 on the inner side ADI in the axial direction of the vacuum insulation container 4 is located between the split core coil assembly 5 and the working space 6. In addition, the wall 43 on the outer side ADO in the axial direction of the vacuum insulation container 4 is located between the split core coil assembly 5 and the end 21a of the yoke 21. In magnetic field generating device 1 configured as above, when current flows through superconducting coil 3 by a current supply unit (not shown), magnetic flux passes through core 2 (yoke 21 and a pair of split core portions 22 ), generating a strong magnetic field in work space 6 . The strong magnetic field generated in the work space 6 can be used for any purpose. For example, the magnetic field generating device 1 can also be used as a heating device for aluminum billets. In this case, the heating device includes a motor for rotating the aluminum billet in addition to the magnetic field generating device 1. A DC current flows through the superconducting coil 3, thereby generating a DC strong magnetic field in the working space 6. The aluminum billet is arranged in the working space 6 in such a way that the central axis of the aluminum billet extends in the depth direction DD, and is rotated around the central axis of the aluminum billet by the motor. Therefore, it is equivalent to applying an AC magnetic field to the aluminum billet, and an induced current flows in the aluminum billet, and the aluminum billet is heated. The cryogenic refrigerator CR may have any conventionally known structure. The cryogenic refrigerator CR is preferably a cold storage type cryogenic refrigerator, and more specifically, for example, a Gifford-McMahon (GM) refrigerator. like Figure 2 As shown, the cryogenic refrigerator CR has one or more (two in the present embodiment) cold stage parts CRS configured to generate refrigeration. More specifically, in this embodiment, the cryogenic refrigerator CR is configured as a two-stage GM refrigerator. Figure 2As shown, in this embodiment, the cryogenic refrigerator CR has a cold head CRH and a motor CRM. In this embodiment, the cold head CRH has two cold units CRU (a first-stage cold unit CRU1 and a second-stage cold unit CRU2) each configured to generate cold. Each cold unit CRU has a cylinder CRC, a displacer CRD configured to be able to reciprocate along the extension direction of the cylinder CRC inside the cylinder CRC, a cold storage material CRL arranged inside the displacer CRD, a sealing component CRF and a sleeve CRV arranged between the cylinder CRC and the displacer CRD. Here, the "extension direction of the cylinder CRC" refers to a direction parallel to the central axis of the cylinder CRC. An expansion chamber CRR is divided between the cylinder CRC and the front end surface of the displacer CRD. The sleeve CRV is made of metal and covers the portion of the cylinder CRC that divides the expansion chamber CRR from the outside. However, the sleeve CRV may not be provided. The cold unit CRU has a cold stage portion CRS near the expansion chamber CRR. The cold stage section CRS is configured to generate cold, more specifically, to generate a temperature equal to the temperature of cold generated in the expansion chamber CRR. The cold stage section CRS is configured, for example, by a portion of the cylinder CRC that divides the expansion chamber CRR and a sleeve CRV. The two cold units CRU are connected in series, specifically, the cylinders CRC of each cold unit CRU and the displacers CRD of each cold unit CRU are connected in series. The second-stage cold unit CRU2 is located at the front end side of the cold head CRH relative to the first-stage cold unit CRU1. The motor CRM is configured to, for example, drive (reciprocate) a displacer CRD accommodated in the cold head CRH. A compressor (not shown) is connected to the cryogenic refrigerator CR. The compressor is connected to the cold head CRH and compresses a refrigerant gas. As the refrigerant gas, helium gas can be cited, for example. An inverter (not shown) may be connected to the cryogenic refrigerator CR. In this case, the inverter is connected between the power supply of the cryogenic refrigerator CR and the compressor, for example, and sets the power supply frequency of the cryogenic refrigerator CR to a predetermined power supply frequency. In the operation of the cryogenic refrigerator CR configured as described above, the high-pressure refrigerant gas compressed by the compressor (not shown) is cooled by the cold stored in the cold storage material CRL in each cold unit CRU, and then guided to the expansion chamber CRR for adiabatic expansion and further cooling. Then, the cooled refrigerant gas returns through the cold storage material CRL. At this time, the action of leaving the cold of the refrigerant gas in the cold storage material CRL is repeated, and thus the temperature of the expansion chamber CRR and even the cold stage portion CRS gradually decreases. During this period, the cold temperature generated in the cold stage portion CRS is lower for the cold unit CRU closer to the rear stage (front end side). That is, in this embodiment, the temperature of the cold generated in the cold stage portion CRS of the second-stage cold unit CRU2 (hereinafter also referred to as "second-stage cold stage portion CRS2") is lower than the temperature of the cold generated in the cold stage portion CRS of the first-stage cold unit CRU1 (hereinafter also referred to as "first-stage cold stage portion CRS1"). The cryogenic refrigerator CR may be configured as a single-stage cryogenic refrigerator having only one cold unit CRU, or may be configured as a multi-stage cryogenic refrigerator having an arbitrary number of cold stage sections CRS. In the present embodiment, the cold head CRH of the cryogenic refrigerator CR is arranged in the vacuum insulation container 4, and the parts other than the cold head CRH in the cryogenic refrigerator CR (motor CRM, power supply, etc.), compressor (not shown), inverter, etc. are arranged outside the vacuum insulation container 4. Thus, it is possible to suppress the excessive heat from the parts other than the cold head CRH in the cryogenic refrigerator CR from invading the vacuum insulation container 4. like Figures 1 to 5 As shown, the heat conductive connection portion TC connects the cold stage portion CRS (the second cold stage portion CRS2 in this embodiment) of the last stage (front end side) in the cryogenic refrigerator CR and the cooling object 3 in a heat conductive manner. As a result, the heat of the cooling object 3 is absorbed (and then cooled) by the cold stage portion CRS (the second cold stage portion CRS2 in this embodiment) of the last stage in the cryogenic refrigerator CR via the heat conductive connection portion TC. The thermally conductive connection portion TC may be formed by any one or more members made of a thermal conductor such as metal. In this embodiment, the thermally conductive connection portion TC respectively has one or more (one in this embodiment) heat transfer conductor parts TP made of a heat conductor such as metal, one or more (four in this embodiment) heat equalizing parts SK, one or more (two in this embodiment) cooling conductor parts PM and a cold storage body 22 (i.e., a split core portion 22 or a core part 22). As in Figure 2As shown by the dotted lines in FIG. 1 , in the present embodiment, a first current lead D1 and a second current lead D2 are disposed in the vacuum insulation container 4 as current leads. One end of the first current lead D1 is connected to the first bus bar BB1. The first bus bar BB1 is in contact with the first cold stage CRS1. The other end of the first current lead D1 is connected to the sealed through terminal E. The sealed through terminal E is installed on the wall of the vacuum insulation container 4. One end of the second current lead D2 is a high temperature end D2a, and the other end is a low temperature end D2b. The high temperature end D2a of the second current lead D2 is connected to the first busbar BB1. The low temperature end D2b of the second current lead D2 is connected to the second busbar BB2. The second busbar BB2 is connected to the superconducting coil 3. The low temperature end D2b of the second current lead D2 is cooled by the terminal portion of the superconducting coil 3 cooled by the second stage cold stage CRS2. The high temperature end D2a of the second current lead D2 is cooled by the first stage cold stage CRS1. The temperature sensor TS is configured to detect the temperature of any one of the object to be cooled 3, the cold stage section CRS of the cryogenic refrigerator CR (preferably the cold stage section CRS of the last stage (front end side) (in the present embodiment, the second cold stage section CRS2)), the heat conductive connection section TC, and the current leads D1, D2 (preferably the second current lead D2). In addition, since the temperature of the cold stage section CRS of the last stage (front end side) in the cryogenic refrigerator CR (in the present embodiment, the second cold stage section CRS2) is rapidly transmitted to the object to be cooled 3 via the heat conductive connection section TC, there is a tendency that the temperatures of the object to be cooled 3, the cold stage section CRS (in the present embodiment, the second cold stage section CRS2), and the heat conductive connection section TC are substantially equal to each other. The temperature sensor TS performs the above-mentioned temperature detection periodically (at predetermined time intervals) or continuously. The temperature detection result detected by the temperature sensor TS is output to the control section PS via wired communication and / or wireless communication. The temperature sensor TS is preferably disposed in the vacuum insulation container 4, and more preferably in contact with a component of a temperature detection target (the cooling target 3, the cold stage portion CRS, the thermal connection portion TC, or the current leads D1, D2). In this embodiment, if Figure 1 As shown, the temperature sensor TS is configured to be in contact with the heat conductive connection portion TC (more specifically, the heat transfer conductor member TP) and detect the temperature of the heat conductive connection portion TC (more specifically, the heat transfer conductor member TP). The control unit PS is configured to include a processing device such as a CPU, and is configured to perform the operation method described below by executing a program stored in a storage unit (not shown). Specifically, the control unit PS is configured to perform various processes described below by executing the program, thereby controlling the cryogenic refrigerator CR based on the detection result of the temperature sensor TS. The control unit PS may also be configured to control a compressor and / or an inverter connected to the cryogenic refrigerator CR. The storage unit (not shown) is composed of, for example, a ROM and / or a RAM, and stores various information such as programs for execution by the control unit PS. The storage unit may be located outside the control unit PS or inside the control unit PS. In this embodiment, if Figure 1 As shown, only one control unit PS is provided for a pair of cooling units RU, that is, an operation method described later is performed in each cooling unit RU by the one control unit PS. However, one control unit PS may be provided for each cooling unit RU, that is, each control unit PS may perform the operation method described later in the corresponding cooling unit RU. Here, an operating method according to one embodiment of the present invention will be described. This operating method is an operating method for a cooling system RS and can be used for the cooling system RS according to any of the embodiments described in this specification. First, the power of the cryogenic refrigerator CR is turned on. The temperature sensor TS periodically (at predetermined time intervals) or continuously detects the temperature of the cooling object 3, the cold stage section CRS of the cryogenic refrigerator CR (the second cold stage section CRS2 in this embodiment), the heat conductive connection section TC, and any one of the current leads D1 and D2, and outputs the detection result to the control section PS. When the temperature detected by the temperature sensor TS drops to a predetermined target cooling temperature THL during the operation of the cryogenic refrigerator CR, the control unit PS performs an operation stop process (operation stop step) to stop the operation of the cryogenic refrigerator CR. When the temperature detected by the temperature sensor TS rises to a predetermined operation start temperature THH higher than a predetermined target cooling temperature THL while the cryogenic refrigerator CR is stopped, the control unit PS performs operation start processing (operation start step) to start the operation of the cryogenic refrigerator CR. As described above, in this operation method, after the power supply of the cryogenic refrigerator CR is turned on, the operation stop processing (operation stop step) and the operation start processing (operation start step) are repeated alternately. In addition, the control unit PS may also stop / start the operation of the cryogenic refrigerator CR, for example, by setting the power of the compressor and the cryogenic refrigerator CR to OFF / ON. More specifically, the control unit PS may set the power of the compressor to OFF / ON, and correspondingly, automatically implement the control of stopping / starting the operation of the cryogenic refrigerator CR according to the compressor, thereby stopping / starting the operation of the cryogenic refrigerator CR. Alternatively, in the case where the compressor and the cryogenic refrigerator CR are each controlled by a signal, the control unit PS may also output a control signal of stopping / starting the operation to the compressor and the cryogenic refrigerator CR, thereby stopping / starting the operation of the cryogenic refrigerator CR. During the operation of the cryogenic refrigerator CR, the driving capacity (power frequency, input power to the compressor, etc.) of the cryogenic refrigerator CR remains constant. From the viewpoint of improving the driving efficiency of the cryogenic refrigerator CR, the power frequency of the running cryogenic refrigerator CR is preferably 50Hz or 60Hz, more preferably 60Hz. Usually, in commercially available cryogenic refrigerators CR, the compressor and motor CRM connected to the cryogenic refrigerator CR operate at a common power frequency of 50Hz or 60Hz. Usually, the refrigeration efficiency is better when the power frequency is 60Hz. It can also be considered to set the power input to the compressor and the motor CRM to 50Hz or 60Hz through an inverter. Furthermore, in addition to radiation and heat transfer from the wall of the vacuum insulation container 4, the components in the vacuum insulation container 4 may also be subjected to intrusion heat via components (current leads D1, D2, etc.) extending from the outside of the vacuum insulation container 4 to the inside of the vacuum insulation container 4. The temperature of the cooling object 3 may rise due to such intrusion heat from the outside while the operation of the cryogenic refrigerator CR is stopped. According to the operating method of this embodiment, instead of making the cryogenic refrigerator CR run continuously, the following operation is repeated: after the temperature of the cooling object 3 drops sufficiently during operation, the operation is temporarily stopped, and when the temperature of the cooling object 3 becomes high again, the operation is restarted. Therefore, it is possible to suppress the cooling of the cooling object 3 from being continuously cooled to a temperature higher than necessary, and thus, from an overall perspective, the driving energy of the cryogenic refrigerator CR can be effectively reduced. In addition, instead of temporarily stopping the operation of the cryogenic refrigerator CR, for example, it is also possible to consider temporarily reducing the power frequency of the cryogenic refrigerator CR (and thus the speed of the drive motor of the compressor) by controlling the inverter, or temporarily reducing the capacity of the cryogenic refrigerator CR by temporarily reducing the input power to the compressor. However, in general, the cryogenic refrigerator CR has a tendency that the lower the power frequency and the input power to the compressor are (and thus, the lower the capacity of the cryogenic refrigerator CR is), the lower the driving efficiency (cooling efficiency). Therefore, in the method of temporarily reducing the capacity of the cryogenic refrigerator CR as described above, the driving energy of the cryogenic refrigerator CR cannot be significantly reduced when viewed as a whole. On the other hand, in the operating method of this embodiment, by alternating between operation and stop of the extremely low temperature refrigerator CR without reducing the capacity of the operating extremely low temperature refrigerator CR (and thus without reducing the operating efficiency), the driving energy (cooling energy) of the extremely low temperature refrigerator CR can be effectively reduced from an overall perspective. In addition, the cooling system RS is not limited to the case where the operation of the extremely low temperature refrigerator CR is always repeatedly stopped / started by the above-mentioned operation method. As needed, the cooling system RS can be switched between the case where the operation of the extremely low temperature refrigerator CR is repeatedly stopped / started by the above-mentioned operation method and the case where the operation of the extremely low temperature refrigerator CR is continuously performed as before. The predetermined target cooling temperature THL is preferably the temperature of the cold stage section CRS (the second cold stage section CRS2 in this embodiment) at the last stage (the front end side) in the cryogenic refrigerator CR when the cooling load of the cold stage section CRS becomes 5W (for example, at Figure 7 10K in the example above, more preferably the temperature of the cold stage section CRS when the cooling load of the last stage (front end side) cold stage section CRS (the second stage cold stage section CRS2 in the present embodiment) becomes 8W (for example, at Figure 7 In the example above, 12K). from Figure 7 From an example of the capacity curve of the illustrated cryogenic refrigerator CR, it can be seen that, in general, the cryogenic refrigerator CR has a tendency that the lower the temperature of the cold stage section CRS (and therefore the cooling temperature), the lower the cooling load (W) (and therefore the cooling efficiency) of the cold stage section CRS of the cryogenic refrigerator CR. When the cooling load of the cold stage section CRS is 0W, it means that no further cooling will be performed under any conditions. In addition, Figure 7An example of a capacity curve of a two-stage ultra-low temperature refrigerator CR when the power supply frequency is set to 50 Hz is shown, wherein the horizontal axis is the temperature (K) of the first-stage cold stage section CRS1, the vertical axis is the temperature (K) of the second-stage cold stage section CRS2, and each curve extending along the approximately vertical direction respectively represents the cooling load (W) of the first-stage cold stage section CRS1, and each curve extending along the approximately horizontal direction respectively represents the cooling load (W) of the second-stage cold stage section CRS2. Therefore, by setting the predetermined target cooling temperature THL as described above, the driving efficiency (cooling efficiency) of the operating cryogenic refrigerator CR can be kept high, and overall, the driving energy (cooling energy) of the cryogenic refrigerator CR can be more effectively reduced. From the same viewpoint, the predetermined target cooling temperature THL is preferably 10 K or higher, and more preferably 12 K or higher. The predetermined target cooling temperature THL is lower than the predetermined operation start temperature THH. The temperature (temperature difference) obtained by subtracting the predetermined target cooling temperature THL from the predetermined operation start temperature THH is preferably 20K or more, and more preferably 25K or more. As in the present embodiment, when the object to be cooled 3 is configured to include a superconducting wire (i.e., for example, when the object to be cooled 3 is a superconducting coil 3), from the viewpoint of maintaining the superconducting wire constituting the object to be cooled 3 as superconducting, the predetermined operation start temperature THH is preferably below the maximum temperature at which the superconducting wire constituting the object to be cooled 3 can become superconducting, and more preferably below the maximum temperature. In addition, the predetermined operation start temperature THH is preferably below the temperature at which the critical current becomes approximately twice the current flowing in the vertical magnetic field of the superconducting wire constituting the object to be cooled 3, and more preferably below the critical current. In addition, as described above, the superconducting wire constituting the cooling object 3 is preferably a high-temperature superconducting wire. In this case, the predetermined operation start temperature THH is preferably below the maximum temperature at which the high-temperature superconducting wire constituting the cooling object 3 can become superconducting, and more preferably is lower than the maximum temperature. Generally, the maximum temperature at which the high-temperature superconducting wire can become superconducting can differ depending on the material constituting the high-temperature superconducting wire, for example, about 77K. On the other hand, the maximum temperature at which a general superconducting wire (low-temperature superconducting wire) can become superconducting can differ depending on the material constituting the low-temperature superconducting wire, for example, about 4K. By using the high-temperature superconducting wire constituting the cooling object 3 as the superconducting wire, the cooling temperature of the cryogenic refrigerator CR in operation (while the superconducting wire constituting the cooling object 3 is kept superconducting) can be kept at a higher temperature than the case where the superconducting wire constituting the cooling object 3 is assumed to be a low-temperature superconducting wire, and the driving efficiency (cooling efficiency) of the cryogenic refrigerator CR in operation can be kept higher, the operating time can be shortened, and the driving energy (cooling energy) of the cryogenic refrigerator CR can be more effectively reduced. As described above, in this embodiment, the heat conduction connection portion TC that connects the last stage (front end side) cold stage portion CRS (in this embodiment, the second stage cold stage portion CRS2) of the cryogenic refrigerator CR and the cooling object 3 in a heat conduction manner has a cold storage body 22 ( Figure 2 ). That is, the cold storage body 22 is connected to the cold stage portion CRS and the cooling object 3 in a heat-conducting manner. The cold storage body 22 is made of a heat conductor such as metal, and is configured to be able to store a part of the cold (sensible heat) generated in the cold stage portion CRS (the second cold stage portion CRS2 in this embodiment) of the last stage (the front end side) in the low-temperature refrigerator CR. As described above, in this embodiment, the cold storage body 22 is a split core portion 22 or a core member 22, and is configured to include iron. By having the cold storage body 22, the cold storage body 22 can store a part of the cold generated by the cold stage section CRS (the second cold stage section CRS2 in this embodiment) of the last section (the front end side) during the operation of the cryogenic refrigerator CR, and when the operation of the cryogenic refrigerator CR is stopped, the cold accumulated by itself so far is used to continuously cool the cooling object 3. In this way, the temperature rise of the cooling object 3 during the operation stop of the cryogenic refrigerator CR can be suppressed, and the operation stop time of the cryogenic refrigerator CR can be increased, and the number of operations and operation stops (starts and stops) of the cryogenic refrigerator CR can be reduced. In this way, the burden imposed on the electrical components of the cooling system RS and the like due to the repeated operation and operation stop (starts and stops) of the cryogenic refrigerator CR can be suppressed, and the life of the cooling system RS can be increased. However, the cold storage body 22 may not be provided. The cold storage body 22 preferably has a larger heat capacity (sensible heat capacity) than the cooling object 3. Generally, there is a tendency that the larger the heat capacity, the higher the performance of accumulating cold (cold storage performance). Therefore, by having the cold storage body 22 have a larger heat capacity (sensible heat capacity) than the cooling object 3, the cold storage performance of the cold storage body 22 can be improved, and the temperature rise of the cooling object 3 during the operation stop of the extremely low temperature refrigerator CR can be further suppressed, and the operation stop time of the extremely low temperature refrigerator CR can be increased, and the number of operations and operation stops (starts and stops) of the extremely low temperature refrigerator CR can be further reduced. From the same viewpoint, the cold storage body 22 is preferably larger in volume than the cooling target 3 . As described above, in this embodiment, the heat conductive connection portion TC that connects the cold stage portion CRS (the second cold stage portion CRS2 in this embodiment) of the last stage (the front end side) of the cryogenic refrigerator CR and the cooling object 3 in a heat conductive manner has one or more (four in this embodiment) heat averaging components SK ( Figure 2 , Figure 4 , Figure 5 That is, one or more (four in the present embodiment) heat equalizing components SK are connected to the cold stage portion CRS and the cooling object 3 in a heat-conductive manner. The heat-scaling member SK has the function of transferring cold quickly and evenly to the cold storage body 22. The heat-scaling member SK is made of a heat conductor such as metal, and is preferably made of copper (for example, pure copper (oxygen-free copper)) from the viewpoints of thermal conductivity, availability, processability, price, etc. If the heat-scaling member SK is formed in a plate shape as in the present embodiment, it is easy to transfer cold evenly, so it is preferred. like Figures 4 to 5 As shown, in the present embodiment, one or more (four in the present embodiment) heat equalizing members SK surround the cold storage body 22 in an annular shape, and specifically, are in contact with the outer peripheral surface of the cold storage body 22 over the entire circumference. More specifically, in this embodiment, if Figure 5As shown, the cold storage body 22 is in a roughly rectangular parallelepiped shape with the axis O as the central axis, and the four side surfaces 224 of the cold storage body 22 are located on the outer peripheral side of the axis O. The first side surface 224a and the fourth side surface 224d of the four side surfaces 224 of the cold storage body 22 are parallel to the axial direction AD and the depth direction DD. The first side surface 224a is located closer to the second longitudinal side ⅤD2 than the fourth side surface 224d. The first side surface 224a faces the second longitudinal side VD2 (the lower side in this embodiment), and the fourth side surface 224d faces the first longitudinal side VD1 (the upper side in this embodiment). The second side surface 224b and the third side surface 224c of the four side surfaces 224 of the cold storage body 22 are parallel to the axial direction AD and the longitudinal direction VD, and are separated from each other in the depth direction DD. The second side surface 224b and the third side surface 224c face the opposite side of the axis O in the depth direction DD. In the present embodiment, the four heat-averaging components SK are plate-shaped and contact the four side surfaces 224 of the cold storage body 22 from the outer peripheral side. The first heat-averaging component SKa and the fourth heat-averaging component SKd of the four heat-averaging components SK are respectively directed parallel to the first side surface 224a and the fourth side surface 224d of the cold storage body 22, and contact (surface contact) the first side surface 224a and the fourth side surface 224d of the cold storage body 22. The second heat-averaging component SKb and the third heat-averaging component SKc of the four heat-averaging components SK are respectively directed parallel to the second side surface 224b and the third side surface 224c of the cold storage body 22, and contact (surface contact) the second side surface 224b and the third side surface 224c of the cold storage body 22. The four heat-averaging components SK are in contact with each other at their respective ends, and thus, the four heat-averaging components SK are ring-shaped. In the present embodiment, one or more (four in the present embodiment) heat equalizing components SK are in contact with the outer peripheral surface of the cold storage body 22 throughout the entire circumference. Therefore, through these heat equalizing components SK, the cold transferred from the extremely low temperature refrigerator CR side can be quickly and evenly transferred to the cold storage body 22 throughout the entire circumference (in other words, the cold storage body 22 can be easily heat-equalized), and at the same time, rapid temperature changes can be suppressed, and the cold storage body 22 can be stably stored. As a result, during the operation of the extremely low temperature refrigerator CR, the cold storage body 22 can be stored more effectively and stably. However, the cold storage body 22 and the heat equalizing member SK may have any shape. In addition, one or more heat-scaling members SK may be in contact with any portion of the cold storage body 22 . like Figure 1 to Figure 2 As shown in FIG. 1 , in the present embodiment, the cold head CRH of the cryogenic refrigerator CR extends in the axial direction AD. The front end of the cold head CRH faces the inner side ADI in the axial direction. However, the cold head CRH of the cryogenic refrigerator CR can point in any direction. like Figure 1 to Figure 2 As shown, in this embodiment, the split core-coil assembly 5 is located closer to the first longitudinal side VD1 than the cold head CRH. In this embodiment, the split core-coil assembly 5 is located closer to the axial inner side ADI than the cold head CRH. However, the positional relationship between the cold head CRH of the cryogenic refrigerator CR and the split core-coil assembly 5 may be arbitrary. As described above, in the present embodiment, the heat conductive connection portion TC that connects the cold stage portion CRS (the second cold stage portion CRS2 in the present embodiment) of the last stage (the front end side) of the cryogenic refrigerator CR and the cooling object 3 in a heat conductive manner has one or more (one in the present embodiment) heat conductive conductor parts TP. That is, the one or more (one in the present embodiment) heat conductive conductor parts TP are connected to the cold stage portion CRS and the cooling object 3 in a heat conductive manner. The heat transfer conductor member TP is made of a heat conductor such as metal, and is preferably made of copper (for example, pure copper (oxygen-free copper)) from the viewpoints of thermal conductivity, availability, processability, price, etc. If the heat transfer conductor member TP is formed in a plate shape as in the present embodiment, it is easy to evenly transfer cold, which is therefore preferred. More specifically, the heat transfer conductor part TP is in contact with the cold stage part CRS (the second cold stage part CRS2 in this embodiment) of the last stage (the front end side) in the cryogenic refrigerator CR and at least one of the one or more (four in this embodiment) heat equalizing parts SK (the first heat equalizing part SKa in this embodiment). Figure 2 ), and then connect them in a heat-conducting manner. Thus, the cold generated from the cold stage portion CRS is transferred to at least one (in this embodiment, the first heat-conducting portion SKa) of one or more (in this embodiment, four) heat-conducting portions SK via the heat-conducting conductor portion TP. In the present embodiment, the heat transfer conductor component TP extends along a substantially longitudinal direction VD, the lower end portion of the heat transfer conductor component TP contacts (surface contacts) the front end surface of the cold stage portion CRS (the second-stage cold stage portion CRS2 in the present embodiment) of the last stage (the front end side) in the ultra-low temperature refrigerator CR, and the upper end portion of the heat transfer conductor component TP contacts (surface contacts) at least one of the one or more (four in the present embodiment) heat equalizing components SK (the first heat equalizing component SKa in the present embodiment). However, the shape and extending direction of the heat transfer conductor part TP may be arbitrary. In addition, the heat transfer conductor component TP may not be provided. For example, the cold stage portion CRS (the second-stage cold stage portion CRS2 in the present embodiment) of the last stage (front end side) in the ultra-low temperature refrigerator CR may be in direct contact with at least one of the one or more (four in the present embodiment) heat equalizing components SK. As described above, in this embodiment, the heat conductive connection portion TC that connects the cold stage portion CRS (the second cold stage portion CRS2 in this embodiment) of the last stage (the front end side) of the cryogenic refrigerator CR and the cooling object 3 in a heat conductive manner has one or more (two in this embodiment) cooling conductor parts PM ( Figure 2 ). That is, one or more (two in this embodiment) cooling conductor parts PM are connected to the cold stage part CRS and the cooling object 3 in a heat-conducting manner. More specifically, one or more (two in this embodiment) cooling conductor parts PM are in contact with at least one of one or more (four in this embodiment) heat-averaging parts SK and the cooling object 3, respectively. The cooling conductor part PM is made of a heat conductor such as metal, and is preferably made of copper (e.g., pure copper (oxygen-free copper)) from the viewpoints of thermal conductivity, availability, processability, price, etc. If the cooling conductor part PM is formed in a plate shape as in the present embodiment, it is easy to evenly transfer coldness, so it is preferred. More specifically, the heat conductive connection TC has a first cooling conductor part PMa and a second cooling conductor part PMb as cooling conductor parts, respectively. The first cooling conductor member PMa is disposed between the cold storage body 22 and the object to be cooled 3 in the axial direction AD, and is in contact (surface contact) with the cold storage body 22 and the object to be cooled 3 . More specifically, in this embodiment, if Figure 1 , Figure 2 , Figure 5 As shown, the outer peripheral surface 221 of the cold storage body 22 has an annular step portion 2211. The step portion 2211 extends throughout the entire circumference in the circumferential direction centered on the axis O. The step portion 2211 faces the inner side ADI in the axial direction. The step portion 2211 is recessed inwardly in the axial straight direction. Specifically, the step portion 2211 includes: an axial straight direction surface 2211a, which is approximately parallel to the axial straight direction OD and faces the inner side ADI in the axial direction; and an axial direction surface 2211b, which extends approximately parallel to the axial direction AD from the axial straight direction surface 2211a to the end surface 223 of the inner side ADI in the axial direction of the cold storage body 22. The cooling object 3 extends throughout the entire circumference in the circumferential direction centered on the axis O and is configured in an annular shape, and is arranged in the step portion 2211. Specifically, the cooling object 3 is wound around the step portion 2211 in the circumferential direction centered on the axis O. On the other hand, the first cooling conductor component PMa is configured to be annularly extended along the circumferential direction with the axis O as the center over the entire circumference. The surface of the first cooling conductor component PMa on the axial direction outer side ADO contacts the axial direction surface 2211a of the step portion 2211 of the cold storage body 22, and the surface of the first cooling conductor component PMa on the axial direction inner side ADI contacts the surface of the cooling object 3 on the axial direction outer side ADO. The axial direction surface 2211b of the step portion 2211 is located on the inner circumference side of the first cooling conductor component PMa and the cooling object 3. In addition, at least one of the heat averaging components SK (in this embodiment, the second heat averaging component SKb, the third heat averaging component SKc, and the fourth heat averaging component SKd) extends to the axial direction inner side ADI beyond the axial direction surface 2211a of the step portion 2211 of the cold storage body 22. At least one of the heat averaging components SK (in this embodiment, the first heat averaging component SKa, the second heat averaging component SKb, and the third heat averaging component SKc) contacts the first cooling conductor component PMa. like Figure 6 As shown, at least one of the first cooling conductor component PMa and the heat-scaling component SK in contact with the first cooling conductor component PMa (the first heat-scaling component SKa in this embodiment) can be fixed to each other by a fixing component F such as a screw. In this embodiment, the end surface of the first heat-scaling component SKa on the inner side ADI in the axial direction is located at approximately the same position as the axial direction surface 2211a of the step portion 2211 of the cold storage body 22 in the axial direction AD. The first cooling conductor component PMa contacts the end surface on the inner side ADI in the axial direction of the first heat-scaling component SKa from the inner side ADI in the axial direction at a position closer to the second longitudinal side VD2 than the cooling object 3, and is fixed to the first heat-scaling component SKa by the fixing component F. The second cooling conductor member PMb is arranged on the inner side ADI in the axial direction of the object to be cooled 3 and is in contact with (surface contact with) the object to be cooled 3 . More specifically, in this embodiment, if Figure 1 , Figure 2 , Figure 5 As shown, the second cooling conductor component PMb includes an axial plate portion PMba substantially parallel to the axial direction OD and an axial plate portion PMbb extending from an end portion of the axial plate portion PMba on the second longitudinal side VD2 toward the axial outer side ADO. The surface of the object to be cooled 3 on the inner side ADI in the axial direction is the same surface as the end surface 223 on the inner side ADI in the axial direction of the cold storage body 22. The surface of the axially outer side ADO of the axially straight plate-shaped portion PMba of the second cooling conductor member PMb is in contact with the surface of the object to be cooled 3 on the inner side ADI in the axial direction and the end surface 223 on the inner side ADI in the axial direction of the cold storage body 22. The axial plate-like portion PMbb of the second cooling conductor component PMb is located on the second longitudinal side VD2 of the first heat-averaging component SKa, and the surface of the first longitudinal side VD1 of the axial plate-like portion PMbb of the second cooling conductor component PMb contacts the surface of the second longitudinal side VD2 of the first heat-averaging component SKa. The axial plate-like portion PMbb of the second cooling conductor component PMb is located closer to the axial inner side ADI than the heat transfer conductor component TP. In the present embodiment, the axial plate-like portion PMbb of the second cooling conductor component PMb is separated from the heat transfer conductor component TP, but the axial plate-like portion PMbb of the second cooling conductor component PMb may also contact the heat transfer conductor component TP. In addition, the second cooling conductor member PMb may not have the axial direction plate-shaped portion PMbb. In this way, one or more (two in the present embodiment) cooling conductor parts PM and at least one of the one or more (four in the present embodiment) heat equalizing parts SK are in contact with the cooling object 3, so that during the operation of the cryogenic refrigerator CR, the cold transferred from the cryogenic refrigerator CR side via the heat equalizing parts SK can be transferred to the cooling object 3 via each cooling conductor part PM. Thus, the cooling object 3 can be cooled more uniformly and effectively. Furthermore, while the operation of the cryogenic refrigerator CR is stopped, the cold stored in the cold storage body 22 is transferred to the cooling object 3 via the first cooling conductor member PMa. However, as long as each cooling conductor member PM is in contact with the heat equalizing member SK and the object to be cooled 3, its shape, position, etc. may be arbitrary. From the viewpoint of effectively transferring the cold from the heat-scaling member SK to the cooling object 3 via the cooling conductor member PM, each cooling conductor member PM is preferably in contact with at least one heat-scaling member SK as in the present embodiment, and is in contact (surface contact) with the end surface on either side of the axial direction AD of the cooling object 3. Thus, the contact area between the cooling conductor member PM and the cooling object 3 can be increased, and the cold can be more effectively transferred from the heat-scaling member SK to the cooling object 3 via the cooling conductor member PM. The radiation shielding SH is divided into a radiation shielding space SHR inside. The cooling object 3, a part of the cryogenic refrigerator CR, the heat conductive connection part TC and the temperature sensor TS are arranged in the radiation shielding space SHR. In the present embodiment, the radiation shielding SH is connected (contacted) with the first-stage cold stage part CRS1 of the cryogenic refrigerator CR, whereby the cold generated in the first-stage cold stage part CRS1 can be transferred to the radiation shielding SH. The radiation shielding SH is configured to suppress the radiation heat from the outside of the radiation shielding SH from invading the radiation shielding space SHR. In the cold head CRH of the cryogenic refrigerator CR, the part closer to the rear side (front end side) than the first-stage cold stage part CRS1 (in the present embodiment, the second-stage cold unit CRU) is arranged in the radiation shielding space SHR. The radiation shield SH preferably has a laminated insulation material on a part or all of its wall (e.g., its outer surface). For example, the laminated insulation material is formed by laminating a plurality of metal-evaporated resin films and resin meshes. Examples of the material constituting the main body of the vacuum insulation container 4 include austenitic stainless steel, composite material glass fiber reinforced plastic (GFRP), and the like. However, the radiation shield SH may not be provided. In the cooling system RS and the magnetic field generating device 1 of the present embodiment, since the magnetic field generating device 1 includes the superconducting coil 3 , a stronger magnetic field can be generated in the working space 6 compared to the case where the magnetic field generating device 1 includes a conventional copper coil instead of the superconducting coil 3 . In addition, according to the magnetic field generating device 1 of the present embodiment, since the magnetic field generating device 1 includes the iron core 2, a strong magnetic field can be generated while reducing the amount of superconductors used in the manufacture of the superconducting coil 3, compared to the case where the magnetic field generating device 1 does not include the iron core 2, so the superconductors can be reduced, and the cost can be reduced. Since superconductors are generally expensive, it can be said that the cost reduction effect is greater by reducing the superconductors. Furthermore, according to the present embodiment, since the core 2 of the magnetic field generating device 1 has the yoke 21 , the magnetic circuit resistance can be reduced and the magnetic flux can be increased compared to a case where the core 2 does not have the yoke 21 . In addition, according to the present embodiment, as described above, the iron core 2 is divided into the yoke 21 and the pair of divided iron core parts 22, and each divided iron core coil assembly 5 is respectively accommodated in each vacuum insulation container 4, and the yoke 21 is arranged outside the pair of vacuum insulation containers 4. Therefore, compared with the case where the entirety of the substantially C-shaped iron core that is not divided and the pair of superconducting coils wound around the pair of ends of the iron core are accommodated in the vacuum insulation container, the vacuum insulation container 4 can be miniaturized. As a result, heat intrusion from the outside can be reduced, and energy saving can be achieved. In addition, assuming that an undivided substantially C-shaped iron core is used, in order to miniaturize the vacuum insulation container, it is also conceivable to configure the vacuum insulation container in a ring shape so that the vacuum insulation container only accommodates a pair of superconducting coils around a pair of ends of the iron core. However, in this case, the wall of the vacuum insulation container is interposed between the iron core and the superconducting coil, that is, the iron core and the superconducting coil are separated, so the circumference of the superconducting coil becomes longer accordingly, and the amount of superconducting coil used increases, resulting in an increase in cost. In addition, due to the portion where the iron core and the superconducting coil are separated, the leakage flux increases, so the amount of superconductor required increases, resulting in an increase in cost. In this regard, according to the present embodiment, the superconducting coil 3 is directly wound on the iron core 2 (specifically, the divided iron core part 22) without passing through the wall of the vacuum insulation container, and the iron core 2 (specifically, the divided iron core part 22) is brought into contact with the superconducting coil 3 to eliminate the distance between the two. Therefore, compared with the case where the vacuum insulation container is formed into a ring shape as described above, the circumference of the superconducting coil 3 can be shortened, and the superconductor can be reduced, and the cost can be reduced. In addition, since the iron core 2 (specifically, the split iron core portion 22) and the superconducting coil 3 are brought into contact and the distance between the two is eliminated, the leakage magnetic flux can be reduced compared to the case where the vacuum insulation container is formed into a ring shape as described above, and the superconductor can be reduced, and the cost can be reduced. In addition, since the iron core 2 (specifically, the split iron core portion 22) and the superconducting coil 3 (via the cooling conductor member PM) are brought into contact, the temperature rise of the superconducting coil 3 can be suppressed by utilizing the cold storage effect of the iron core 2 (specifically, the split iron core portion 22), compared to the case where the vacuum insulation container is formed into a ring shape as described above, so in addition to reducing the cooling burden of the extremely low temperature refrigerator CR, the superconducting coil can be sufficiently cooled, and the capacity of the superconductor can be effectively utilized. In addition, according to this embodiment, Figure 6 As shown, in each split core-coil assembly 5, when power is supplied, a Lorentz force ( Figure 6 The electromagnetic force ADI acting on the split core portion 22 inward in the axial direction ( Figure 6 The hollow arrows (indicated by the arrows in the figure) cancel each other out, so the force acting on the split core-coil assembly 5 in the axial direction AD becomes small. Therefore, the support structure for supporting the split core-coil assembly 5 relative to the vacuum insulation container 4 can be simplified. Furthermore, the heat intrusion from the outside to the superconducting coil 3 through the support structure can be reduced, and further, in addition to reducing the cooling burden of the cryogenic refrigerator CR, the superconducting coil can be sufficiently cooled, so that the capacity of the superconductor can be effectively utilized. In this embodiment, if Figure 1 , Figure 2 , Figure 6As shown, the cooling system RS and the magnetic field generating device 1 have a supporting member 7 as a supporting structure for supporting the split core-coil assembly 5 relative to the vacuum insulation container 4. The supporting member 7 is configured to suspend the split core-coil assembly 5 from the vacuum insulation container 4. More specifically, in this example, the supporting member 7 is configured, for example, in the shape of a rod with low thermal conductivity, and is configured to insulate the split core-coil assembly 5 from the wall 41 on the upper side (the first longitudinal side VD1) in the vacuum insulation container 4 and suspend the split core-coil assembly 5. In this way, the supporting member 7 is configured to support the self-weight of the split core-coil assembly 5, and is not configured to restrict the horizontal movement of the split core-coil assembly 5. In this way, in this embodiment, the supporting structure (supporting member 7) for supporting the split core-coil assembly 5 relative to the vacuum insulation container 4 is simply configured. In addition, the support structure for supporting the split core-coil assembly 5 with respect to the vacuum insulation container 4 is not limited to this, and may be any structure. In this embodiment, if Figure 1 , Figure 2 , Figure 6 As shown, the cooling system RS and the magnetic field generating device 1 are provided on the walls 42 and 43 ( Figure 6 ) is provided with a spacing member 8. Thus, when power is supplied, the split core-coil assembly 5 can be more effectively restrained from excessive movement in the axial direction AD. In addition, by maintaining the gap between the split core-coil assembly 5 and the vacuum insulation container 4 when power is not supplied, the amount of heat intrusion when power is stopped can be reduced by the spacing member 8. For example, the spacer member 8 may be fixed to the split core portion 22 of the split core-coil assembly 5 or may be formed integrally with the split core portion 22, and may be separate from the walls 42 and 43 on both sides of the axial direction AD in the vacuum insulation container 4 and may be in a non-fixed state. Alternatively, the spacer member 8 may be separate from the split core-coil assembly 5 and may be in a non-fixed state, and may be fixed to the walls 42 and 43 on both sides of the axial direction AD in the vacuum insulation container 4, or may be formed integrally with the walls 42 and 43. In addition, the spacer member 8 may not be provided. As described above, in this embodiment, if Figure 1 , Figure 2 , Figure 5 , Figure 6As shown, in each of a pair of split core coil assemblies 5, the outer peripheral surface 221 of the split core portion 22 has an annular step portion 2211. The step portion 2211 extends over the entire circumference in the circumferential direction centered on the axis O. The step portion 2211 faces the working space 6 (via the wall 42 of the vacuum insulation container 4). The step portion 2211 is recessed inwardly in the axial direction. Specifically, the step portion 2211 includes: an axial direction surface 2211a, which is roughly parallel to the axial direction OD and faces the axial direction inner side ADI; and an axial direction surface 2211b, which extends roughly parallel to the axial direction AD from the axial direction surface 2211a to the end surface 223 of the axial direction inner side ADI of the split core portion 22. The superconducting coil 3 is wound on the step portion 2211 in the circumferential direction centered on the axis O. Thus, since the superconducting coil 3 and the split core portion 22 are opposed to each other in the axial direction AD, the Lorentz force ( Figure 6 The electromagnetic force ADI acting on the split core portion 22 inward in the axial direction ( Figure 6 The hollow arrows (indicated by the arrows in the figure) more effectively cancel each other out, and the force acting on the split core-coil assembly 5 in the axial direction AD becomes smaller. Therefore, the support structure for supporting the split core-coil assembly 5 relative to the vacuum insulation container 4 can be further simplified. In addition, although the Lorentz force ( Figure 6 The black arrow in the figure acts on the superconducting coil 3, but the movement of the superconducting coil 3 to the outside ADO in the axial direction is restricted by the step portion 2211 (especially, the axial plane 2211a). That is, the step portion 2211 has the function of restricting the movement of the superconducting coil 3 to the outside ADO in the axial direction. Therefore, there is no need to separately set up a restricting structure for restricting the movement of the superconducting coil 3 to the outside ADO in the axial direction. Furthermore, the heat intrusion from the outside into the superconducting coil 3 through the restricting structure can be reduced, and the temperature rise of the superconducting coil 3 can be suppressed. Therefore, in addition to reducing the cooling burden of the extremely low temperature refrigerator CR, the superconducting coil can be fully cooled, so that the capacity of the superconductor can be effectively utilized. In addition, the inner side ADI in the axial direction of the superconducting coil 3 is not covered by the split core portion 22, and faces the working space 6 (via the wall 42 of the vacuum insulation container 4), so a stronger magnetic field can be generated in the working space 6 accordingly. In addition, since the superconducting coil 3 contacts not only the axial surface 2211b of the step portion 2211 but also the axial surface 2211a of the step portion 2211, the contact area with the split core portion 22 is increased accordingly, thereby improving the cooling effect of the superconducting coil through the split core portion 22. In addition, the above-mentioned step portion 2211 is preferably provided in both of the pair of split core-coil assemblies 5 , but may be provided in only one of the pair of split core-coil assemblies 5 . In each example described in this specification, in at least one of the pair of split core-coil assemblies 5, the outer peripheral surface 31 of the superconducting coil 3 is as follows: Figure 6 As shown in the example, it can be located at the same axial OD position as the outer peripheral surface 221 of the split core portion 22, or, although omitted from the illustration, it can be closer to the inner side than the outer peripheral surface 221 of the split core portion 22, or it can be closer to the outer side than the outer peripheral surface 221 of the split core portion 22. In each example described in this specification, although not shown in the figure, in at least one of the pair of split core-coil assemblies 5, the outer peripheral surface 221 of the split core portion 22 may have a protrusion protruding toward the outer peripheral side, and the protrusion has a step portion 2211. In this case, the outer peripheral surface 31 of the superconducting coil 3 may be located at the same axial straight direction OD position as the outer peripheral surface of the protrusion, or may be located closer to the inner peripheral side than the outer periphery of the protrusion, or may be located closer to the outer peripheral side than the outer peripheral surface of the protrusion. Although not shown in the figure, in at least one of the pair of split core coil assemblies 5, the outer peripheral surface 221 of the split core portion 22 may also have an annular groove. The groove extends over the entire circumference in the circumferential direction centered on the axis O. The outer peripheral side of the groove is open. The groove has a pair of groove wall surfaces that are opposite to each other and are roughly parallel to the axial direction OD, and a groove bottom surface that is roughly parallel to the axial direction AD while facing the outer peripheral side. In this case, the superconducting coil 3 is wound in the groove in the circumferential direction and is then accommodated in the groove. However, in at least one of the pair of split core-coil assemblies 5, the superconducting coil 3 may be wound on the outer peripheral surface 221 of the split core part 22 without unevenness such as the step portion 2211 or the groove. In this case, since the Lorentz force acting on the superconducting coil 3 toward the outer side ADO in the axial direction and the electromagnetic force acting on the split core part 22 toward the inner side ADI in the axial direction cancel each other, the force acting on the split core-coil assembly 5 in the axial direction AD becomes smaller. Therefore, the support structure for supporting the split core-coil assembly 5 relative to the vacuum insulation container 4 can be simplified. However, as shown in the above-mentioned examples, when the superconducting coil 3 is wound on the step portion 2211 or the groove of the outer peripheral surface 221 of the split core part 22, the effect is greater. In addition, when the superconducting coil 3 is wound on the outer peripheral surface 221 of the split core part 22 without unevenness such as the step portion 2211 or the groove, it is preferable to separately configure a restriction structure for restricting the movement of the superconducting coil 3 toward the outer side ADO in the axial direction. In each example described in this specification, in at least one of the pair of split core-coil assemblies 5, the superconducting coil 3 is as follows: Figures 1 to 6As shown in the example of , it can be composed of a single-stage structure consisting of only one layer along the axial direction AD, or, although not shown in the figure, it can also be composed of a multi-stage structure in which a plurality of superconducting coil layers are arranged along the axial direction AD. In each example described in this specification, the end portion 21a of the yoke 21 and the wall 43 of the axially outer side ADO of the vacuum insulation container 4 are preferably as follows: Figure 6 They are shown spaced apart from each other, but may also be in contact with each other. In each example described in this specification, the structure of the vacuum insulation container 4 and the split iron core coil assembly 5 is preferably symmetrical relative to the center of the axial direction AD of the cooling system RS and the magnetic field generating device 1, but can also be asymmetrical relative to the center of the axial direction AD of the cooling system RS and the magnetic field generating device 1. In each example described in this specification, the cooling system RS and the magnetic field generating device 1 may include only one vacuum insulation container 4. In this case, a pair of split core-coil assemblies 5 are accommodated in the vacuum insulation container 4, and the yoke 21 is arranged outside the vacuum insulation container 4. In this case, the vacuum insulation container 4 can be miniaturized compared to the case where the unsplit substantially C-shaped iron core and the pair of superconducting coils wound around the pair of ends of the iron core are accommodated in the vacuum insulation container. In this case, the vacuum insulation container 4 may have a connection pipe or the like. Figure 1 The example has a structure in which a pair of vacuum insulation containers 4 are connected to each other and integrated. In the above-mentioned embodiment, each cooling unit RU is provided with only one temperature sensor TS. However, the cooling unit RU may also be provided with a plurality of temperature sensors TS. In this case, each temperature sensor TS of the cooling unit RU detects the temperature of the cooling object 3, any cold stage portion CRS of the cryogenic refrigerator CR, the heat conductive connection portion TC, and any one of the current leads D1 and D2. In this case, preferably, each temperature sensor TS is configured to sense the temperature of different parts. In addition, during the operation of the cryogenic refrigerator CR, when the temperature detected by any one of the predetermined temperature sensors TS drops to the predetermined target cooling temperature THL, the control unit PS performs an operation stop process (operation stop step) of stopping the operation of the cryogenic refrigerator CR. In addition, during the operation stop of the cryogenic refrigerator CR, when the temperature detected by any one of the predetermined temperature sensors TS rises to a predetermined operation start temperature THH higher than the predetermined target cooling temperature THL, the control unit PS performs an operation start process (operation start step) of starting the operation of the cryogenic refrigerator CR. The above-mentioned predetermined temperature sensors TS used in the operation stop step and the operation start step may be the same or different in the operation stop step and the operation start step. Here, the scheduled operation start temperature THH will be supplementally described. High-temperature superconducting wires generally refer to wires that achieve a superconducting state at liquid nitrogen temperatures, but there are also materials such as magnesium diboride (MgB2) that exhibit superconductivity at temperatures between liquid helium and liquid nitrogen, which are classified as high-temperature superconducting wires. The minimum cooling temperature (Tc critical temperature) of a high temperature superconducting wire changes depending on the following conditions. (1) Material preparation method and its deviation (2) Magnetic field strength in the operating environment (3) Current Normally, after determining the condition of (1) above, (2) and (3) which are related to each other are determined, and the necessary cooling temperature is determined based on the results of these three conditions. However, it is difficult to consciously determine the cooling temperature. In the past, when the cooling temperature needed to be set, sometimes after cooling to below the set temperature using the ultra-low temperature refrigerator CR, power was supplied to the heater wound on the cold head CRH to obtain the predetermined temperature by raising the temperature (controlled by a thermostat). The predetermined operation start temperature THH is preferably set to a lower temperature than the critical temperature determined according to (1), (2), and (3) above, taking into account the start-up time and temperature error of the refrigerator. Figure 8 An example of critical current characteristics of a REBCO wire, which is one type of high temperature superconducting wire, is shown. Figure 8 In the example of FIG. 1 , for example, preferably, the predetermined operation start temperature THH is set to about 45K for a superconducting coil current of 300A and a critical temperature of 50K. In addition, in the ultra-low temperature refrigerator CR Figure 1 In the case of a two-stage type as in the embodiment of FIG. 1 , it is preferred that the first-stage cold stage section CRS1 is used to cool the high temperature end D2a of the second current lead D2, and the critical point of the temperature rise due to the intrusion heat into the first-stage cold stage section CRS1 is reached later than that due to the temperature rise on the superconducting coil 3 side. In the case of being faster than that, it is preferred to start the operation of the cryogenic refrigerator CR under the temperature condition of the first-stage cold stage section CRS1. Therefore, for example, a temperature sensor TS may be configured to detect the temperature of the first-stage cold stage section CRS1, and when the temperature detected by the temperature sensor TS rises to a predetermined operation start temperature THH, the operation of the cryogenic refrigerator CR is started. Next, supplementary explanation will be given on the predetermined target cooling temperature THL. Since the temperature of the superconducting coil 3 after the cryogenic refrigerator CR starts operating is always a temperature that satisfies the superconducting condition, the predetermined target cooling temperature THL can be determined by conditions completely different from the maintenance of the superconducting condition. After the operation of the cryogenic refrigerator CR is started, in addition to the external heat of several watts caused by radiation, conduction, etc. of a roughly fixed value, the cryogenic refrigerator CR also cools the sensible heat of the superconducting coil 3 itself and its accessories, and the cooling temperature gradually decreases. As the cooling temperature decreases, the efficiency of the refrigerator decreases, and the cooling capacity is static at a temperature that is in balance with the external heat, and may not be able to cool to a temperature below it. When only maintaining the superconducting state is considered, the operation of the cryogenic refrigerator CR can be stopped at any temperature between the equilibrium temperature and the predetermined operation start temperature THH. However, if the predetermined target cooling temperature THL is increased, the time from the start of operation after the operation is stopped to the stop of operation after the operation is started becomes shorter, and the frequency of starting and stopping of the cryogenic refrigerator CR becomes higher. Since the number of starts and stops of the cryogenic refrigerator CR increases, it will have an adverse effect on the mechanical life of the cryogenic refrigerator CR and related equipment. Therefore, it is possible to consider lowering the predetermined target cooling temperature THL. However, due to the reduction in the efficiency of the cryogenic refrigerator CR, the accumulation of cooling energy caused by the sensible heat of the cold storage body 22 requires time, which is longer than the cooling time caused by the sensible heat of the cold storage body 22 after the operation of the cryogenic refrigerator CR is stopped. The predetermined target cooling temperature THL is preferably set to a value equal to or higher than a balance point between the operation time based on the cold storage amount and the time required for the cold storage amount. The operation based on cold storage is considered to be cooling the external intrusion heat based on cold storage, and therefore, the reference point of the predetermined target cooling temperature THL is considered to be, for example, a point where the cooling capacity is twice the external intrusion heat. At this reference temperature, since a significant amount of cooling heat is required, it becomes a temperature higher than the lowest reachable temperature of the cryogenic refrigerator CR under no-load cooling conditions. For example, when the external intrusion heat is 4 W, it is preferable to set the point where the capacity of the second stage cold stage part CRS2 of the cryogenic refrigerator CR is 8 W, that is, about 15 K, as the reference point of the predetermined target cooling temperature THL. In this case, it is possible to consider setting the operation start and stop time of the cryogenic refrigerator CR to the longest while realizing power saving of the cryogenic refrigerator CR. At temperatures above the reference point, the capacity of the cryogenic refrigerator CR is higher. Although the time until the scheduled operation start temperature THH is shortened, the amount of cold storage per unit time increases, and the ratio of the stop time of the cryogenic refrigerator CR to the operating time increases, which can be considered to be more energy-efficient. In summary, we can say that: (a) It is preferable that the predetermined operation start temperature THH is a value having a necessary margin with respect to a critical temperature reference based on current conditions and cross magnetic field intensity with respect to the use characteristics of the wire material to be used. (b) The predetermined target cooling temperature THL is preferably set based on the cooling capacity of the cryogenic refrigerator CR which is twice the amount of external intrusion heat and the cooling temperature at that time. (c) It is preferable to consider that if the predetermined target cooling temperature THL is set higher than the reference, although the utilization rate of the cryogenic refrigerator CR is improved, the start-stop frequency increases, which has an adverse effect on the life of the mechanical parts. (d) In the case of a two-stage cryogenic refrigerator CR, it is preferred that the cooling temperature condition of the first-stage cold stage portion CRS1, especially the temperature of the high-temperature end D2a of the second current lead D2, does not exceed the allowable range. If it exceeds the range, it is preferred to operate the cryogenic refrigerator CR under this condition. [Practicality] The cooling system according to the present invention and the operating method according to the present invention can be used to cool any cooling object, for example, can be suitable for cooling superconducting coils. In addition, the cooling system according to the present invention and the operating method according to the present invention can be used in any device, for example, can be used in a magnetic field generating device. The magnetic field generating device according to the present invention can be used for any purpose, for example, it can be used as a heating device for aluminum billets. Description of Reference Numerals RS: Cooling system RU: Cooling Unit CR: Cryogenic Refrigerator CRM: Motor CRH: Cold Head CRU: Cold Unit CRU1: First level cold unit CRU2: Cold Unit Level 2 CRC: Cylinder Block CRD: Displacer CRL: Cold Storage Material CRF: Sealing components CRR: Expansion Chamber CRV: Casing CRS: Cold Stage Division CRS1: First cold stage CRS2: Second Cold Stage Section TS:Temperature sensor PS: Control Department TC: Thermally conductive connection SK: Heat dissipation components SKa: First heat sink SKb: Second heat sink SKc: The third heat sink SKd: The fourth heat-saturating component PM: Cooling conductor parts PMa: First cooling conductor part PMb: Second cooling conductor part PMba: axis-direction plate-shaped part PMbb: Axial plate-shaped part TP: Heat transfer conductor parts SH: Radiation Shielding SHR: Radiation Shielded Room F: Fixed parts D1: First current lead (current lead) D2: Second current lead (current lead) D2a: High temperature end D2b: Low temperature end E: Sealed through terminal BB1: First busbar BB2: Second busbar 1: Magnetic field generating device 2: Iron core 21: Yoke 21a: End 22: Split core part (cold storage body, core parts) 221: Outer surface 2211: Steps 2211a: Axis vertical direction surface 2211b: Axis direction surface 223: End face on the inner side of the axis direction 224: Side 224a: First side 224b: Second side 224c: Third side 224d: The fourth side 3: Superconducting coil (cooling object) 31: Outer surface 4: Vacuum insulation container 41: Upper wall 42: Wall on the inner side of the axis 43: Wall on the outside of the axis 5: Split core coil assembly 6: Workspace 7: Supporting parts 8: Spacer components O: Axis AD: Axis direction (relative direction) ADI: Axis direction inner side ADO: Axis direction outer side OD: Axis Direction VD: Vertical VD1: Longitudinal first side VD2: longitudinal second side DD: Depth Direction

Claims

1. A cooling system, comprising: Vacuum insulated container; A cooling object is disposed in the vacuum insulation container; A cryogenic refrigerator having a cold stage portion configured to generate refrigeration; A heat-conducting connection portion, connecting the cold stage portion and the cooling object in a heat-conducting manner; one or more temperature sensors; a current lead disposed in the vacuum insulation container; and Control Department, The one or more temperature sensors are configured to detect the temperature of any one of the cooling object, the cold stage portion, the thermally conductive connection portion, and the current lead, respectively. The control unit is configured to perform the following processing: Operation stop processing, during the operation of the cryogenic refrigerator, when the temperature detected by any one of the temperature sensors drops to a predetermined target cooling temperature, stopping the operation of the cryogenic refrigerator; as well as The operation start processing starts the operation of the cryogenic refrigerator when the temperature detected by any one of the temperature sensors rises to a predetermined operation start temperature higher than the predetermined target cooling temperature during the operation stop of the cryogenic refrigerator.

2. The cooling system according to claim 1, wherein: The predetermined target cooling temperature is equal to or higher than the temperature of the cold stage portion when the cooling load of the cold stage portion reaches 5W.

3. The cooling system according to claim 1, The cooling object is composed of a high temperature superconducting wire. The predetermined operation start temperature is lower than or equal to a maximum temperature at which the high temperature superconducting wire can become superconducting.

4. The cooling system according to claim 1, The heat conductive connection portion has a cold storage body.

5. The cooling system according to claim 4, The heat capacity of the cold storage element is larger than the heat capacity of the object to be cooled.

6. The cooling system according to claim 4, The heat-conducting connection portion has one or more heat-dissipating components. The one or more heat equalizing members are in contact with the outer peripheral surface of the cold storage body over the entire circumference.

7. The cooling system according to claim 6, The heat-conducting connection has one or more cooling conductor parts, The one or more cooling conductor members are in contact with the heat dissipating member and the object to be cooled.

8. The cooling system according to claim 4, The cold storage body is an iron core component, The cooling object is a superconducting coil, The superconducting coil is wound around the core member.

9. A cooling system according to any one of claims 4 to 8, The cooling system is configured for use with a magnetic field generating device, The magnetic field generating device comprises: the cooling system; and A roughly C-shaped or U-shaped yoke, The cooling system comprises one or a pair of the vacuum insulation containers, The cooling system includes a pair of superconducting coils as the cooling objects, The cooling system includes a pair of split core parts, each serving as the cold storage body. The pair of split core parts are formed separately from the yoke, are located inside the yoke, and are arranged opposite to each other with a working space interposed therebetween. Each of the split core parts has the superconducting coils wound around it in a circumferential direction centered on an axis, and the axis is parallel to a direction in which the pair of split core parts face each other. A split core-coil assembly including the split core portion and the superconducting coil wound around the split core portion is accommodated in the one or a pair of the vacuum insulation containers, The yoke is arranged outside the one or the pair of vacuum insulation containers.

10. A magnetic field generating device, comprising: A cooling system according to any one of claims 4 to 8; and A roughly C-shaped or U-shaped yoke, The cooling system comprises one or a pair of the vacuum insulation containers, The cooling system includes a pair of superconducting coils as the cooling objects, The cooling system includes a pair of split core parts, each serving as the cold storage body. The pair of split core parts are formed separately from the yoke, are located inside the yoke, and are arranged opposite to each other with a working space interposed therebetween. Each of the split core parts has the superconducting coils wound around it in a circumferential direction centered on an axis, wherein the axis is parallel to a direction in which the pair of split core parts face each other. A split core-coil assembly including the split core portion and the superconducting coil wound around the split core portion is accommodated in the one or a pair of the vacuum insulation containers, The yoke is arranged outside the one or the pair of vacuum insulation containers.

11. An operating method for a cooling system according to any one of claims 1 to 8, the operating method comprising: an operation stopping step, in which, when the temperature detected by any one of the temperature sensors drops to a predetermined target cooling temperature during the operation of the cryogenic refrigerator, the control unit stops the operation of the cryogenic refrigerator; as well as In the operation start step, when the temperature detected by any one of the temperature sensors rises to a predetermined operation start temperature higher than the predetermined target cooling temperature during the operation stop of the cryogenic refrigerator, the control unit starts the operation of the cryogenic refrigerator.

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