WO2020114065A1 - Current lead structure, and superconducting magnet - Google Patents

Abstract

The present application relates to a current lead structure and a superconducting magnet. The current lead structure comprises a fixed connector, a movable connector, and a deformable sealing assembly establishing a sealed connection between the movable connector and a housing of the superconducting magnet. An external force elastically deforms the deformable sealing assembly, and under the action of a force from the deformation, the movable connector moves, with respect to the housing of the superconducting magnet, in a reciprocating manner between a connection position enabling contact with the fixed connector and a disconnection position away from the fixed connector. In the current lead structure and the superconducting magnet provided in the present application, the movable connector moves to connect to the fixed connector during excitation or a field strength decrease, thereby conducting superconducting coils with an external loop. After the superconducting coils form a closed loop, the movable connector moves to disconnect from the fixed connector while still being connected to the housing of the superconducting magnet via the deformable sealing assembly. In this way, the current lead structure has the operational convenience of permanent current leads, and the advantage of temporary current leads in which unplugging does not cause additional thermal conduction.

Description

Current lead structure and superconducting magnet Technical field

The invention relates to the technical field of superconducting magnets, in particular to a current lead structure and superconducting magnets.

Background technique

Superconductivity refers to the property that the resistance of some substances drops to zero under certain temperature conditions (generally lower temperature), and the superconductivity of the material can be used to make superconducting magnets. Among them, the superconducting coil in the superconducting magnet is connected to the external circuit through the current lead to generate a magnetic field and store energy.

However, the common current leads are permanent current leads and temporary current leads. Among them, the permanent current lead is kept inside the magnet no matter during excitation or field reduction or after any operation is completed, so it is easy to generate additional heat conduction; while the temporary current lead is connected to the magnet during excitation and field reduction, but after completion It is pulled out, so it needs frequent insertion and removal during use, and the operation is complicated.

Summary of the invention

Based on this, a current lead structure and a superconducting magnet that take into consideration the convenience of the permanent current lead operation and the temporary current lead after pulling out will not generate additional heat conduction.

A current lead structure is assembled on a superconducting magnet. The current lead structure includes:

A fixed joint fixedly arranged on one of the internal structure of the cold screen of the superconducting magnet and the cold screen;

A movable joint movably arranged on the superconducting magnet housing in the superconducting magnet; and

Deformation seal assembly, sealingly connected between the mobile joint and the superconducting magnet housing;

Wherein, the deformation seal assembly generates elastic deformation under the action of external force, and the movable joint is connected to the superconducting magnet housing at the connection position in contact with the fixed joint under the action of the deformation force, and separated from the fixed joint Reciprocate between disconnected positions.

In one of the embodiments, a liquid nitrogen chamber for passing liquid nitrogen is opened inside the mobile joint.

In one of the embodiments, the moving joint includes a connecting end extending into the superconducting magnet housing and an operating end exposing the superconducting magnet housing, and the liquid nitrogen chamber is configured to extend from the operating end to The connection end.

In one of the embodiments, the liquid nitrogen chamber includes a liquid nitrogen input channel, a cooling chamber, and a nitrogen output channel, the cooling chamber is disposed at an end of the connection end that contacts the fixed joint, and the liquid nitrogen input channel Both are connected with the nitrogen output channel between the outside world and the cooling cavity.

In one of the embodiments, the deformation seal assembly includes an insulation member and a deformation member, the insulation member is sealed and insulated around the outer periphery of the movable joint, the deformation member is connected to the insulation member and the super Between the hole walls of the assembling hole on the magnet guide shell for the mobile joint to protrude.

In one of the embodiments, the insulating member is made of ceramic or resin.

In one of the embodiments, the deformation member includes an elastic film and a supporting portion, the elastic film is connected to the outer edge of the insulating member, and the supporting portion is connected to the elastic film and the superconducting magnet housing Between the hole walls of the assembly hole.

In one of the embodiments, the elastic film is made of metal stainless steel with deformability.

In one of the embodiments, the current lead structure includes an auxiliary connection mechanism assembled in the superconducting magnet housing, and the moving joint includes a connecting end extending into the superconducting magnet housing and exposing the superconducting magnet The operation end of the housing; the operation end is movably penetrated in the auxiliary connection mechanism in a reciprocating direction.

A superconducting magnet includes a superconducting coil, a low-temperature cooling unit for providing superconducting temperature for the superconducting coil, and a current lead structure for realizing conduction between the superconducting coil and an external circuit; the low-temperature cooling The unit includes a superconducting magnet housing, a cold screen internal structure and a cold screen, the cold screen is disposed between the superconducting magnet housing and the cold screen internal structure; the current lead structure is the current lead structure described above .

The current lead structure and superconducting magnet provided by this application, the connection or disconnection of the two parts of the fixed joint and the mobile joint are controlled. During excitation and field drop, the mobile joint moves to connect with the fixed joint to conduct the super The conducting coil and the external circuit are similar to the permanent current lead; after the closed loop of the superconducting coil is completed, the moving joint is moved to be disconnected from the fixed joint, similar to the temporary current lead, but at this time the moving joint is still connected to the superconducting magnet housing through the deformation sealing assembly In other words, the current lead structure takes into account both the convenience of permanent current lead operation and the advantage of no additional heat conduction after the temporary current lead is pulled out.

BRIEF DESCRIPTION

1 is a schematic diagram of a current lead structure of a superconducting magnet in an embodiment of the invention;

FIG. 2a is a schematic diagram of the cooperation between the deformation seal assembly and the moving joint in the embodiment of the superconducting magnet shown in FIG. 1;

2b is a schematic diagram of the cooperation between the deformation sealing assembly and the moving joint in another embodiment of the superconducting magnet shown in FIG. 1;

2c is a schematic diagram of the cooperation between the deformation seal assembly and the moving joint in another embodiment of the superconducting magnet shown in FIG. 1;

3 is a schematic diagram of a current lead structure of a superconducting magnet in another embodiment of the invention.

detailed description

In order to facilitate understanding of the present invention, the present invention will be described more fully below with reference to related drawings. The drawings show preferred embodiments of the invention. However, the present invention can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

It should be noted that when an element is said to be "fixed" to another element, it may be directly on the other element or there may be an element between the two. When an element is considered to “connect” another element, it may be directly connected to the other element or may exist between the two elements at the same time.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present invention. The terminology used in the description of the present invention herein is for the purpose of describing specific embodiments, and is not intended to limit the present invention. The term "and/or" as used herein includes any and all combinations of one or more related listed items.

With the development of science and technology, superconducting technology has been more widely used in industry and scientific research. Specifically, superconducting magnets made of superconducting materials can be applied to technical fields such as motors, magnetic levitation transportation, magnetic resonance imaging (Magnetic Resonance Imaging, MRI), nuclear magnetic resonance (Nuclear Magnetic Resonance, NMR), and other technical fields. Among them, represented by medical superconducting magnets, medical superconducting magnets have become an important part of modern high-field MRI systems. Their main role is to provide high-strength and high-stability background magnetic fields for MRI work, which is convenient for achieving fast and high contrast. And high-definition imaging.

The superconducting magnet is mainly composed of superconducting coil, superconducting switch, low temperature unit, auxiliary circuit and current lead. Among them, the superconducting coil generates a magnetic field by passing current, which is the main energy storage component; the superconducting switch ensures that the superconducting coil works steadily in the closed-loop and open-loop states, and the low-temperature unit ensures that all components that require superconducting work are at superconducting temperature, assist The circuit mainly completes the quench protection of the superconducting magnet and other functions, so that the superconducting magnet will not damage the coil by high voltage or high temperature during the quenching process; the current lead is used to connect the superconducting coil with the external circuit to realize the superconducting coil Excitation and drop field.

Among them, the temporary current lead is only used when operating the superconducting magnet, such as providing a current channel when exciting or dropping the field; when the predetermined operation is completed, the current lead and the superconducting magnet are separated and taken out. When the temporary current lead is connected to the internal connector of the superconducting magnet (due to entering the 4K environment from the 300K environment), there will be inadequate contact at the junction, resulting in the junction resistance greater than the safe value, thereby increasing the superconductivity during excitation and field reduction The risk of magnet quenching; at the same time, a small amount of air will be brought into the process of joining the temporary current lead and the internal connector of the superconducting magnet, especially after many operations, the frost at the junction of the superconducting magnet and the current lead is even worse The icing directly causes the resistance value of the junction between the temporary current lead and the internal connector of the superconducting magnet to increase, thereby increasing the risk of quenching of the superconducting magnet during excitation and field reduction.

The permanent current lead is kept inside the superconducting magnet no matter during the excitation or field reduction or after any operation is completed. One end is connected to the internal circuit of the superconducting magnet, and the other end is connected to the power cable outside the superconducting magnet. That is, the permanent current lead will always be connected to the internal circuit of the superconducting magnet. When connecting to the external circuit, there is no process from 300K to 4K, which can avoid the adverse factors caused by the temporary current lead and facilitate the excitation and derating of the superconducting magnet at any time. Field operations. The permanent current lead should not only ensure low resistance to avoid excessive heat generation after passing current, but also ensure small thermal conductivity to avoid excessive heat leakage.

In order to solve the above problems of the temporary current leads and the permanent current leads, the present invention provides a semi-permanent current lead structure to solve the above problems.

In order to facilitate understanding, the structure of the superconducting magnet is briefly introduced first. Because of the low-temperature superconducting magnet, it must operate in the low-temperature temperature range of about 4K (-269℃). Therefore, in order to maintain the working environment of the low-temperature superconducting magnet, the low-temperature superconducting magnet is usually designed as a Dewar vessel with high vacuum and high insulation performance.

Among them, the Dewar container includes the internal structure of the cold screen, the superconducting magnet shell and the cold screen. The internal structure of the cold screen is filled with helium and liquid helium, and the superconducting coil in the superconducting magnet is immersed in liquid helium. The superconducting magnet shell is arranged outside the internal structure of the cold screen, and forms a double-walled structure with the internal structure of the cold screen. At the same time, a high vacuum is drawn between the walls to reduce the heat transfer of the gas, and the two opposite surfaces of the double wall are plated or polished to reduce the emissivity, thereby reducing the radiation heat transfer as much as possible. The cold screen (50K environment) is installed between the internal structure of the cold screen and the superconducting magnet shell, and a multi-layer polymer insulation film is wound outside the cold screen to minimize the superconducting magnet shell (the external temperature is 300K) to the cold screen Thermal radiation (ie, heat leakage) of the internal structure (4K environment).

FIG. 1 shows a structural schematic diagram of a current lead structure in an embodiment of the present invention; for ease of description, the drawings only show the structure related to the embodiment of the present invention.

Referring to FIG. 1, in one embodiment of the present invention, the current lead structure 100 is assembled on a superconducting magnet, and is used to connect the superconducting coil with an external circuit to generate a magnetic field to realize energy storage of the superconducting coil. The current lead structure 100 includes a fixed joint 10, a movable joint 30 and a deformation seal assembly 50.

Among them, the fixed joint 10 is fixedly disposed on one of the internal structure 200 and the cold screen of the superconducting magnet mid-cooling screen, the mobile joint 30 is movably disposed on the superconducting magnet housing 400 of the superconducting magnet, and the deformation sealing assembly 50 is hermetically connected to the mobile Between the joint 30 and the superconducting magnet housing 400. The deformation seal assembly 50 is elastically deformed by an external force, and the movable joint 30 reciprocates relative to the superconducting magnet housing 400 between a connection position in contact with the fixed joint 10 and a disconnected position separated from the fixed joint 10 under the deformation force.

In other words, the current lead structure 100 is divided into two parts, one part is fixedly arranged inside the superconducting magnet (ie, the fixed joint 10), and the other part is movable through the deformation sealing assembly 50 but is always connected to the superconducting magnet (ie, moving Connector 30). In this way, the movable joint 30 can also be detachably contacted with the fixed joint 10 through the deformation seal assembly 50 without being pulled out from the superconducting magnet, so as to realize the movable joint 30 and the fixed joint when operating the superconducting magnet 10 Electrical conduction, such as excitation or field drop; and when the predetermined operation is completed, the mobile joint 30 is separated from the fixed joint 10 without being pulled out from the superconducting magnet.

In this application, the current lead structure 100 takes into account both the convenience of the permanent current lead operation and the advantage that no additional heat conduction is generated after the temporary current lead is pulled out, which is equivalent to the semi-permanent type. The connection or disconnection of the fixed joint 10 and the mobile joint 30 is controlled. During excitation and field drop, the mobile joint 30 moves to connect with the fixed joint 10 (connection position), and the superconducting coil is connected to the outside The loop is similar to a permanent current lead; after the closed loop of the superconducting coil is completed, the moving joint 30 moves to be disconnected from the fixed joint 10 (open position), similar to a temporary current lead, but at this time the moving joint 30 is still connected through the deformation seal assembly 50 On the superconducting magnet housing 400.

Compared with the traditional permanent current lead, the semi-permanent current lead structure 100 in this application after the operation is completed, the mobile joint 30 will be separated from the fixed joint inside the superconducting magnet, that is, in a non-contact state in a vacuum environment, cutting off the current lead Structure 100, a heat transfer channel from 300K environment to 4K environment, avoids heat leakage. Compared with the traditional temporary current lead, the semi-permanent current lead structure 100 in this application does not need to be repeatedly inserted and removed during the operation process (that is, there is no need to enter the 4K environment from the 300K environment each time), so there is no temporary current lead insertion and extraction process The frost phenomenon also guarantees that the contact resistance is lower than the designed safe value, and ensures that the heating is within the controllable range.

In this specific embodiment, the fixed joint 10 is set on the cold screen (50K environment), the mobile joint 30 is set on the superconducting magnet housing 400 (300K environment), and both are in the superconducting magnet housing 400 (300K component) and The cold environment (50K components) is clutched in a vacuum environment, and the designed contact area can be much larger than the contact area of the commonly used temporary current lead connector, effectively ensuring that the contact resistance is lower than the safe resistance value.

Specifically, the mobile joint 30 includes a connecting end 31 and an operating end 33. The superconducting magnet housing 400 defines an assembly hole 401, and the connecting end 31 extends into the superconducting magnet housing 400 through the assembly hole 401 for detachable contact with the fixed joint 10. The operation end 33 is exposed outside the superconducting magnet housing 400 through the assembly hole 401, and is used for the user or an external device to perform force control to drive the connection end 31 to contact or separate from the fixed joint 10.

The deformation seal assembly 50 includes an insulating member 51 and a deformation member 53. The insulating member 51 is sealed and insulated around the outer periphery of the mobile joint 30, and the deforming member 53 is connected between the insulating member 51 and the wall of the mounting hole 401 on the superconducting magnet housing 400 for the mobile joint 30 to extend for The movement of the joint 30 provides room for deformation. In this specific embodiment, in order to form a vacuum environment, the insulating member 51 is made of ceramic or resin.

2a-2c, the deformation member 53 includes an elastic film 530 and a supporting portion 532. The elastic film 530 is connected to the outer edge of the insulating member 51. The supporting portion 532 is connected to the elastic film 530 and the mounting hole 401 on the superconducting magnet housing 400 Between the walls of the hole.

Among them, the design, material selection, thickness and size of the deformation member 53 are all related to its own shape. When a force is applied to the mobile joint 30 to connect it with the fixed joint 10, the deformation member 53 must complete the effective displacement deformation under the action of force to ensure the effective connection of the mobile joint 30 and the fixed joint 10, and at the same time ensure the deformation of the deformed member 53 Is within its safe elastic deformation. The structural displacement response of the deformable member 53 can be obtained by solving the overall stiffness matrix balance equation (1) of the structure through the finite element method.

K·q＝P (1)

Where: K is the overall element stiffness matrix of the structure

q is the overall displacement vector of the structure

P is the overall equivalent external load vector of the structure.

After considering setting the same materials, geometric parameters, applying the same load and boundary conditions to different structures, it is used to optimize based on the results of finite element analysis and find the parameters that meet the application. The following describes three deforming members 53 with different structures as examples, but the shape and structure of the deforming member 53 include, but are not limited to, the examples in the above three types, and applications that use similar structures belong to the scope of this invention.

Referring to FIG. 2a, in one embodiment, the deforming member 53 has a generally circular disc structure, and the elastic film 530 and the support portion 532 are located in the same plane when no deformation occurs. Among them, the elastic film 530 is located on the inner periphery of the disc structure and connected to the outer edge of the insulating member 51, and the support portion 532 is connected to the outer periphery of the elastic film 530.

Referring to FIG. 2b, in another embodiment, the deforming member 53 generally has an inverted bowl structure with an opening toward the cold screen, the elastic film 530 is located on the inner periphery of the inverted bowl structure and is connected to the outer edge of the insulating member 51, and the support portion 532 It is connected to the outer periphery of the elastic film 530.

Referring to FIG. 2c, in yet another embodiment, the deforming member 53 generally has a bowl structure opening toward the superconducting magnet housing 400, the elastic film 530 is located on the inner periphery of the bowl structure and is connected to the outer edge of the insulating member 51, and the supporting portion 532 is connected to the outer periphery of the elastic film 530.

In the above three embodiments, the insulating member 51 can be a high-current power feed-through element with a welded edge. The elastic film 530 can be connected to the welded edge of the insulating member 51 by means of vacuum sealant, ceramic sealing or welding. At the same time, both the elastic film 530 and the support portion 532 may be integrally or separately arranged with the same material, or may be integrally or separately arranged with two different materials, which is not limited herein. In this specific embodiment, the elastic film 530 is made of a non-magnetic material with deformability, such as aluminum alloy, titanium alloy, or the like. Correspondingly, the supporting portion 532 can be made of the same metal stainless steel material with the deformability as the elastic film 530; it can also be made of a material with deformability but different from the elastic film 530, and even the supporting portion 532 can It is made of a rigid (not deformable) material, and only needs to realize that the movable joint 30 can move at least under the deformation force of the elastic film 530, which is not limited herein. In addition, in order to facilitate process molding and manufacturing, the deformation member 53 is preferably made of the same material as the superconducting magnet housing 400.

Please refer back to FIG. 1. The current lead structure 100 further includes an auxiliary connection mechanism 70 assembled in the superconducting magnet housing 400. The operating end 33 of the movable joint 30 is movably inserted in the auxiliary connection mechanism 70 in the reciprocating direction. The auxiliary connection mechanism 70 is used to provide support for the assembly of the mobile joint 30 and at the same time provide guidance for the reciprocating movement of the mobile joint 30. Meanwhile, the structure of the auxiliary connection mechanism 70 may be a sleeve mounted on the outer periphery of the mounting hole 401 on the superconducting magnet housing 400, or other supporting guide structures, which is not limited herein.

Please refer to FIG. 3. In another embodiment, a liquid nitrogen chamber for liquid nitrogen is opened inside the mobile connector 30 to cool the mobile connector 30 and reduce the heat generation of the current lead structure 100 during power-on.

Specifically, the liquid nitrogen chamber is configured to extend from the operation end 33 to the connection end 31, so that the entire movable joint 30 is cooled by the input of liquid nitrogen. In this specific embodiment, the liquid nitrogen chamber includes a liquid nitrogen input channel 350, a cooling chamber 352, and a nitrogen output channel 354. The cooling chamber 352 is disposed at the end of the connection end 31 that contacts the fixed joint 10, and the liquid nitrogen input channel 350 and nitrogen output The channels 354 are all connected between the outside and the cooling cavity 352. That is, after the liquid nitrogen input from the liquid nitrogen input channel 350 cools the cavity 352, the mobile joint 30 is cooled and cooled; the heated nitrogen is discharged through the nitrogen output channel 354, so that the liquid nitrogen circulates inside the mobile joint 30 To achieve the effect of cooling and cooling.

The current lead structure 100 provided in this application has the following beneficial effects:

1. Convenient operation. The semi-permanent current lead structure 100 in this application takes into account the convenience of the permanent current lead. It only needs a simple connection operation when it needs to be connected, and there is no problem of repeated insertion and removal of temporary current leads;

2. Low heat generation during use, the joint between the mobile joint 30 and the fixed joint 10 of the semi-permanent current lead structure 100 in this application can reduce the contact resistance and reduce heat generation by expanding the contact area; meanwhile, there is no temporary current lead insertion and removal process The frost phenomenon also effectively ensures that the contact resistance is lower than the designed safe value and controls heating;

3. By charging liquid nitrogen inside the current lead structure 100 to lower the temperature, the temperature rise caused by the heating of the current lead structure 100 during the energization process is reduced;

4. To reduce the heat conduction during use, after the excitation and field reduction process of the semi-permanent current lead structure 100 in this application is completed, the moving joint 30 and the fixed joint 10 in the current lead structure 100 will be disconnected inside the superconducting magnet vacuum chamber, cutting off the heat conduction The channel greatly reduces the heat conduction from the 300K environment to the 4K environment.

The superconducting magnet provided in the first embodiment of the present invention has all the technical features of the current lead structure 100, so it has the same technical effects as the current lead structure 100.

The above-mentioned examples only express several embodiments of the present invention, and their descriptions are more specific and detailed, but they should not be construed as limiting the patent scope of the present invention. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all fall within the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims.

Claims (10)

A current lead structure is assembled on a superconducting magnet. The current lead structure includes: A fixed joint fixedly arranged on one of the internal structure of the cold screen of the superconducting magnet and the cold screen; A movable joint movably arranged on the superconducting magnet housing in the superconducting magnet; and Deformation seal assembly, sealingly connected between the mobile joint and the superconducting magnet housing; Wherein, the deformation seal assembly generates elastic deformation under the action of external force, and the movable joint is connected to the superconducting magnet housing at the connection position in contact with the fixed joint under the action of the deformation force, and separated from the fixed joint Reciprocate between disconnected positions. The current lead structure according to claim 1, wherein a liquid nitrogen chamber for introducing liquid nitrogen is opened inside the movable joint. The current lead structure according to claim 2, wherein the movable joint includes a connecting end extending into the superconducting magnet housing and an operating end exposing the superconducting magnet housing, and the liquid nitrogen cavity structure It extends from the operation end to the connection end. The current lead structure according to claim 2 or 3, wherein the liquid nitrogen chamber includes a liquid nitrogen input channel, a cooling chamber and a nitrogen output channel, the cooling chamber is arranged at the connection end and the fixed joint At the contacted end, the liquid nitrogen input channel and the nitrogen output channel are both connected between the outside world and the cooling chamber. The current lead structure according to claim 1, wherein the deformation seal assembly includes an insulation member and a deformation member, the insulation member is sealed and insulated around the outer periphery of the movable joint, and the deformation member is connected to Between the insulating member and the hole wall of the mounting hole on the superconducting magnet housing for the mobile joint to extend. The current lead structure according to claim 5, wherein the insulating member is made of ceramic or resin. The current lead structure according to claim 5, wherein the deformation member comprises an elastic film and a supporting portion, the elastic film is connected to an outer edge of the insulating member, and the supporting portion is connected to the elastic film Between the hole wall of the assembly hole on the superconducting magnet housing. The current lead structure according to claim 7, wherein the elastic film is made of a non-magnetic metal material with deformability. The current lead structure according to claim 1, wherein the current lead structure includes an auxiliary connection mechanism assembled in the superconducting magnet housing, and the moving joint includes a connection extending into the superconducting magnet housing And an operating end exposing the superconducting magnet housing; the operating end is movably penetrated in the auxiliary connection mechanism in a reciprocating direction. A superconducting magnet, characterized by comprising a superconducting coil, a low-temperature cooling unit for providing superconducting temperature for the superconducting coil, and a current lead structure for realizing conduction between the superconducting coil and an external circuit; The low-temperature cooling unit includes a superconducting magnet housing, an internal structure of a cold screen and a cold screen, the cold screen is disposed between the superconducting magnet housing and the internal structure of the cold screen; the current lead structure is the above claims The current lead structure according to any one of 1-9.

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