System and method for converting helium bath cooling system of superconducting magnet for magnetic resonance imaging system into sealed cryogenic system

Abstract

The present disclosure relates to systems and methods for converting a helium bath cooling system of a superconducting magnet for a magnetic resonance imaging system into a sealed cryogenic system. A superconducting magnet system includes: a coil support structure having a body; a superconducting magnet having a plurality of coils disposed around the main body; and a helium container containing the coil support structure and the superconducting magnet. The superconducting magnet system includes a cooling system including a pipe network disposed within the helium vessel and configured to deliver helium within the helium vessel, where the pipe network is thermally coupled counter-to the plurality of coils. The cooling system comprises: a liquid helium storage system located within the helium container; and a helium after-condenser, the helium after-condenser being located outside the helium container. The cooling system includes one or more tubes that couple the helium storage system to the helium recondenser, where the one or more tubes are reverse vacuum-sealed through a location of the helium vessel to make the helium vessel a sealed helium vessel.

Description

Background Art

[0001] The subject matter disclosed herein relates to a superconducting magnet for magnetic resonance imaging (MRI), and more particularly to a system and method for converting a helium bath cooling system to a sealed cryogenic system for a superconducting magnet for an MRI system.

[0002] Non-invasive imaging techniques allow images of internal structures or features of a patient / object to be obtained without performing invasive procedures on the patient / object. Specifically, such non-invasive imaging techniques rely on various physical principles (such as differential transmission of X-rays through a target volume, reflection of acoustic waves within a volume, paramagnetism of different tissues and materials within a volume, decomposition of target radionuclides in the body, etc.) to acquire data and construct an image or otherwise represent the observed internal features of the patient / object.

[0003] During MRI, when a substance such as human tissue is subjected to a uniform magnetic field (polarization field B0), the individual magnetic moments of the spins in the tissue attempt to align with the polarization field, but precess around the polarization field in a random order at a Larmor frequency that is characteristic of these magnetic moments. If the substance or tissue is subjected to a magnetic field that is in the xy plane and close to the Larmor frequency (excitation field B1), the net alignment moment or "longitudinal magnetization" M z can be rotated or "tilted" into the xy plane to produce a net transverse magnetic moment M t After the excitation signal B1 is terminated, a signal is emitted by the excited spins and can be received and processed to form an image.

[0004] When these signals are used to generate images, the magnetic field gradient (G x , G y and G z ). Typically, the area to be imaged is scanned in a series of measurement cycles in which these gradient fields are varied depending on the particular positioning method used. The resulting set of received nuclear magnetic resonance (NMR) signals is digitized and processed to reconstruct an image using one of many well-known reconstruction techniques.

[0005] MRI systems can utilize superconducting magnets. In addition, MRI systems can operate using liquid helium. Sealed cryogenic systems utilize very small amounts of helium (e.g., a few liters, compared to hundreds or even thousands of liters for baths used to cool superconducting magnets). All existing sealed cryogenic magnets use a metal coil support structure (e.g., a coil former) that utilizes a higher thermal conductivity to achieve temperature uniformity. In addition, the metal support structure makes thermal management easier. In addition, the use of a metal coil former makes sleeve / magnet suspension much easier. Liquid helium can also be utilized in a bath for cooling superconducting magnets (e.g., by filling a cryogenic container (e.g., a helium container) with a superconducting magnet disposed therein with liquid helium). In contrast to sealed cryogenic magnets, bath-cooled magnets can utilize a glass fiber composite structure, which presents many challenges. For example, the thermal conductivity of a glass fiber composite structure is very low, which can cause a temperature gradient that can ultimately lead to quenching, greater outgassing, and emissivity. Greater outgassing and emissivity cause additional heat loads, which make it difficult for the glass fiber composite structure to be part of a sealed system. Additionally, the suspension attachment to the fiberglass composite support structure is challenging and can cause deformation of the fiberglass composite coil support structure and magnet uniformity issues. Helium is a commodity that is increasing in price due to global supply chain issues and increased demand. While there is a need to improve the efficiency of helium usage for bath cooling magnets, this will be difficult due to issues with the fiberglass composite coil support structure. Summary of the invention

[0006] The following shows an overview of certain embodiments disclosed herein. It should be understood that these aspects proposed are only to provide the reader with a brief overview of these specific embodiments, and these aspects are not intended to limit the scope of the present disclosure. In fact, the present disclosure may cover various aspects that may not be shown below.

[0007] In one embodiment, a superconducting magnet system for a magnetic resonance imaging system is provided. The superconducting magnet system includes a coil support structure having a main body. The superconducting magnet system also includes a superconducting magnet having a plurality of coils arranged around the main body of the coil support structure. The superconducting magnet system also includes a helium container, which contains the coil support structure and the superconducting magnet. The superconducting magnet system also includes a cooling system. The cooling system includes a pipe network, which is arranged in the helium container and is configured to transport helium in the helium container, wherein the pipe network is reversely thermally coupled to the plurality of coils. The cooling system also includes a liquid helium storage system, which is located in the helium container. The cooling system also includes a helium recondenser, which is located outside the helium container to recondense vapor helium into liquid helium. The cooling system also includes one or more tubes coupling the helium storage system to the helium recondenser, wherein locations where the one or more tubes pass through the helium vessel are reverse vacuum sealed to make the helium vessel a sealed helium vessel, wherein the cooling system is configured to maintain a uniform temperature between the sealed helium vessel and the plurality of coils.

[0008] In another embodiment, a method for cooling a superconducting magnet of a magnetic resonance imaging system is provided. The method includes: filling a sealed cryogenic vessel with liquid helium until a first desired temperature for cooling the superconducting magnet is reached, the superconducting magnet having a plurality of coils disposed around a body of a coil support structure, wherein the superconducting magnet is disposed within the sealed cryogenic vessel. The method also includes: stopping filling the sealed cryogenic vessel with the liquid helium when the first desired temperature is reached. The method also includes: after stopping filling the sealed cryogenic vessel with the liquid helium, pumping out excess helium using a rough vacuum pump coupled to the sealed cryogenic vessel. The method even includes: activating a sealed cryogenic system by flowing a refrigerant through a pipe network to cool the superconducting magnet to a second desired temperature, the sealed cryogenic system including the pipe network disposed within the sealed cryogenic vessel, wherein the second desired temperature is lower than the first desired temperature.

[0009] In another embodiment, a magnetic resonance imaging system is provided. The magnetic resonance imaging system includes a coil support structure having a body. The body of the coil support structure is made of a glass fiber composite material. The magnetic resonance imaging system also includes a superconducting magnet having a plurality of coils arranged around the body of the coil support structure. The magnetic resonance imaging system also includes a helium container, which contains the coil support structure and the superconducting magnet. The magnetic resonance imaging system also includes a cooling system. The cooling system includes a pipe network, which is arranged in the helium container and is configured to transport helium in the helium container, wherein the pipe network is reversely thermally coupled to the plurality of coils. The cooling system also includes a liquid helium storage system, which is located in the helium container. The cooling system also includes a helium recondenser, which is located outside the helium container to recondense vapor helium into liquid helium. The cooling system even includes one or more tubes, which couple the helium storage system to the helium recondenser, wherein the position where the one or more tubes pass through the helium container is reversely vacuum sealed to make the helium container a sealed helium container. The cooling system is configured to first cool the superconducting magnet to a first desired temperature by filling the sealed helium vessel with liquid helium, and then cool the superconducting magnet to a second desired temperature by flowing the helium through the pipe network, wherein the second desired temperature is lower than the first desired temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These and other features, aspects and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters refer to like parts throughout, and in which:

[0011] Figure 1 is a side cross-sectional view of a portion of a cooling system for a magnetic resonance imaging machine according to aspects of the present disclosure;

[0012] Figure 2 A cooling system for a magnetic resonance imaging machine according to various aspects of the present disclosure (including Figure 1 A schematic diagram of a portion of a cooling system in FIG.

[0013] Figure 3 According to various aspects of the present disclosure Figure 1 A cross-sectional view of a cooling pipe of a cooling system in FIG.

[0014] Figure 4 is an example of a method for thermally coupling a coil of a superconducting magnet to a Figure 3 A schematic diagram of the cooling pipe process;

[0015] Figure 5is an example of a method for thermally coupling a coil of a superconducting magnet to a Figure 3 A schematic diagram of the cooling pipe process;

[0016] Figure 6 is directly thermally coupled to the Figure 5 A cross-sectional view of a cooling tube of a coil in FIG.

[0017] Figure 7 is a liquid helium mesh for cooling a superconducting magnet of an MRI machine according to aspects of the present disclosure;

[0018] Figure 8 According to various aspects of the present disclosure Figure 2 A schematic diagram of a vacuum feedthrough (eg, a bellows) between a recondenser and a tank of a cooling system in FIG.

[0019] Fig. 9 According to various aspects of the present disclosure Figure 2 A schematic diagram of a vacuum feedthrough (eg, a bimetallic joint) between a recondenser and a tank of a cooling system in FIG.

[0020] Fig.10 is a schematic diagram of a bimetallic joint coupled to a tube according to aspects of the present disclosure;

[0021] Fig.11 is a schematic diagram of a superconducting switch according to aspects of the present disclosure;

[0022] Fig.12 is a schematic diagram of a current lead coupled to a superconducting switch according to aspects of the present disclosure;

[0023] Fig.13 is a flow chart of a method for cooling a superconducting magnet of a magnetic imaging system according to aspects of the present disclosure; and

[0024] Fig.14 is a schematic diagram of an example magnetic resonance system according to aspects of the present disclosure. DETAILED DESCRIPTION

[0025] One or more specific embodiments will be described below. In order to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related constraints and business-related constraints that may vary from implementation to implementation. In addition, it should be understood that such development efforts may be complex and time-consuming, but are still routine tasks for design, fabrication, and manufacturing for ordinary technicians who benefit from this disclosure.

[0026] When introducing elements of various embodiments of the present subject matter, the articles "a," "an," "the," and "said" are intended to indicate that there are one or more of the respective elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements in addition to the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus the additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.

[0027] Although various aspects of the following discussion are provided in the context of medical imaging, it should be understood that the disclosed technology is not limited to such medical contexts. In fact, the examples and explanations are provided in such medical contexts only to facilitate explanation by providing examples of real-life implementations and applications. However, the disclosed technology can also be used in other contexts, such as non-destructive inspection of manufactured parts or goods (i.e., quality control or quality review applications) and / or image reconstruction of non-invasive inspection of packages, boxes, luggage, etc. (i.e., security or screening applications). In general, the disclosed technology can be used in any imaging or screening context or image processing or photography field, where a group or class of acquired data undergoes a reconstruction process to generate an image or volume.

[0028] The present disclosure provides a system and method for converting a helium bath cooling system for a superconducting magnet for an MRI system into a sealed low-cryogenic system. Specifically, a superconducting magnet system includes a coil support structure (e.g., a coil former), which has a body. In certain embodiments, the coil support structure may be made of a fiberglass composite material. The superconducting magnet system also includes a superconducting magnet having a plurality of coils arranged around the body of the coil support structure. The superconducting magnet system also includes a helium container, which contains the coil support structure and the superconducting magnet. The superconducting magnet system also includes a cooling system. The cooling system includes a pipe network, which is arranged in the helium container and is configured to transport helium in the helium container, wherein the pipe network is reversely thermally coupled to the plurality of coils. The cooling system also includes a liquid helium storage system, which is located in the helium container. The cooling system also includes a helium recondenser, which is located outside the helium container to recondense vapor helium into liquid helium. The cooling system also includes one or more tubes coupling the helium storage system to the helium recondenser, wherein locations where the one or more tubes pass through the helium vessel are reverse vacuum sealed to make the helium vessel a sealed helium vessel, wherein the cooling system is configured to maintain a uniform temperature between the sealed helium vessel and the plurality of coils.

[0029] In some embodiments, to produce the sealed helium container, the superconducting magnet system includes a corresponding bellows located at a position where each corresponding tube of the one or more tubes passes through the helium container, wherein each corresponding bellows forms a vacuum seal and is coupled to the corresponding tube of the one or more tubes, and the one or more tubes are rigid. In some embodiments, to produce the sealed helium container, a corresponding bimetallic joint is arranged around each of the one or more tubes at a position where each corresponding tube of the one or more tubes passes through the helium container, wherein each corresponding bimetallic joint forms a vacuum seal, and the one or more tubes are flexible. In some embodiments, each corresponding bimetallic joint includes an inner metal layer joined to the corresponding tube and an outer metal layer joined to the helium container, and the inner metal layer is made of a different metal material than the outer metal layer.

[0030] In some embodiments, each coil of the plurality of coils is thermally coupled to a corresponding tube of the tube network via a thermal coupling assembly, wherein the thermal coupling assembly includes a flat thermally conductive metal strip (e.g., a flat copper strip) disposed on the corresponding coil, a thermally conductive metal wire outer wrap (e.g., a copper wire outer wrap) wound around both a portion of the flat thermally conductive metal strip and the corresponding coil, and an end of the flat thermally conductive metal strip is coupled to a thermally conductive metal plate (e.g., a copper plate), which is coupled to the corresponding tube. In some embodiments, the thermal coupling assembly includes a thermally conductive metal sheet (e.g., a copper sheet) wrapped around the corresponding tube, and the thermally conductive metal plate is coupled to the thermally conductive metal sheet. In some embodiments, each coil of the plurality of coils is thermally coupled to a corresponding tube of the tube network via a thermal coupling assembly, wherein the thermal coupling assembly comprises a flat thermally conductive metal strip (e.g., a flat copper strip) disposed on the corresponding coil, a thermally conductive metal plate (e.g., a copper plate) disposed around a portion of the flat thermally conductive metal strip, and an end of the flat thermally conductive metal strip is coupled to an additional thermally conductive metal plate (e.g., a copper plate), the additional thermally conductive metal plate being coupled to the corresponding tube. In some embodiments, wherein the thermal coupling assembly comprises a thermally conductive metal sheet wrapped around the corresponding tube, and the additional thermally conductive metal plate is coupled to the thermally conductive metal sheet.

[0031] In certain embodiments, the superconducting magnet system includes a superconducting switch configured to operate at a temperature of 80 Kelvin or less, wherein the superconducting switch is both located within the helium vessel and thermally isolated from the helium vessel, the superconducting switch is configured to switch between a resistive mode and a superconducting mode, and the superconducting switch is thermally coupled to a corresponding tube of the pipe network. In certain embodiments, the superconducting switch includes a liner insulator disposed around a body of the switch and configured to thermally isolate the superconducting switch from the helium vessel, the superconducting switch includes a thermally conductive metal sheet (e.g., a copper sheet) disposed around the liner insulator and thermally connected to the corresponding tube, and wherein the liner insulator and the thermally conductive metal sheet are configured to prevent convection of the superconducting switch during a warm-up period of the superconducting magnet. In certain embodiments, a power lead coupled to the superconducting switch, wherein the power lead comprises a high temperature superconducting wire coupled to a heat sink located outside the helium vessel, wherein an end of the high temperature superconducting wire coupled to the heat sink is electrically isolated, and wherein the power lead comprises a low temperature superconducting wire having a first end coupled to the heat sink and a second end coupled to the superconducting switch, and the low temperature superconducting wire enters the helium vessel from outside the helium vessel through an electrically isolated feedthrough.

[0032] With the above modifications, the superconducting magnet can be cooled using a combination of a cooling loop directly thermally coupled to the coil and helium bath cooling. A method for cooling a superconducting magnet of a magnetic resonance imaging system includes filling a sealed cryogenic vessel with liquid helium until a first desired temperature for cooling the superconducting magnet is reached, the superconducting magnet having a plurality of coils disposed around a body of a coil support structure, wherein the superconducting magnet is disposed within the sealed cryogenic vessel. The method also includes stopping filling the sealed cryogenic vessel with the liquid helium when the first desired temperature is reached. The method also includes pumping out excess helium using a rough vacuum pump coupled to the sealed cryogenic vessel after stopping filling the sealed cryogenic vessel with the liquid helium. The method even includes activating a sealed cryogenic system by flowing a cryogen (e.g., helium) through a pipe network to cool the superconducting magnet to a second desired temperature, the sealed cryogenic system including the pipe network disposed within the sealed cryogenic vessel, wherein the second desired temperature is lower than the first desired temperature. In certain embodiments, the method includes filling the pipe network with the cryogen and sealing it prior to cooling the superconducting magnet. The pressure in the sealed cryogenic vessel after the excess helium is pumped out creates internal convection to ensure uniform temperature distribution between the plurality of coils and the sealed cryogenic vessel.

[0033] The disclosed embodiments provide for converting existing bath cooled magnets (particularly those existing bath cooled magnets with glass fiber composite structures) to sealed low cryogen systems, while keeping the support structure, coil configuration and cryostat (e.g., helium container) almost intact, while replacing the main switch of the superconducting magnet with a switch configured for low cryogen operation and adding superconducting current leads. In addition, the disclosed embodiments provide a liquid helium net that allows direct cooling of the sealed helium container. In addition, the disclosed embodiments provide a feed-through configuration (e.g., a tube for passing through the sealed helium container), which eliminates vibration transmission from the cold head and compensates for thermal expansion differences between the materials involved. Further, the disclosed embodiments enable superconducting magnets disposed in sealed cryogenic containers to be cooled faster (e.g., from 1 week to 3 weeks to 1 day to 3 days), which is equivalent to the cooling of bath cooled magnets. Further still, the disclosed embodiments reduce helium consumption (e.g., due to the elimination of helium addition during the service life of the magnet), and thus reduce the costs associated with helium consumption. Still further, the disclosed embodiments eliminate the need for a quench exhaust line.

[0034] Reference now Figure 1, illustrates a portion of a cooling system 10 for a superconducting magnet of an MRI machine. A portion of the cooling system 10 is reversely assembled to an MRI machine that was originally configured for helium bath cooling using a superconducting magnet. As shown, the cooling system 10 includes a plurality of cooling tubes 12 (e.g., a network of tubes 12 forming a sealed cryogenic system) or other suitable cooling paths, wherein liquid helium circulates within the cooling tubes 12. The cooling tubes 12 define a main cooling loop 14. The cooling tubes 12 are reversely thermally coupled to a main coil former or support shell or body 16 (e.g., a main coil support), and in one embodiment, the cooling tubes may also be thermally coupled to a shielding coil former (e.g., a demagnetizing coil former) or support shell or body 18 (e.g., a shielding coil support) that encloses the main coil former 16. The main coil former 16 and the shielding coil former 18 support or maintain the position of a main MRI magnet coil 20 and a shielding MRI magnet coil 22 (also referred to as a demagnetizing coil) in a manner known in the art, respectively. For example, the main magnet coil 20 can be heat-shrink-fitted and bonded within the main coil former 16 (which can be a cylindrical metal coil former) to provide thermal contact therebetween. Similarly, the shield magnet coil 22 can be heat-shrink-fitted and bonded within the shield coil former 18 (which can be a cylindrical metal coil former) to provide thermal contact therebetween. Other types of coils (e.g., epoxy coils) can be provided. In one embodiment, the main magnet coil 20 and the magnet shield coil 22 can be formed of any material capable of producing a superconducting magnet, such as niobium-titanium (NbTi), niobium-tin (Nb3Sn), or magnesium diboride (MgB2). As described in more detail below, the cooling tube 12 can be directly thermally coupled to the coils 20, 22 on the coil formers 16, 18.

[0035] like Figure 2 As further illustrated in FIG. 1 , which illustrates additional portions of a cooling system 10 , various embodiments of the present invention may be implemented as part of an MRI superconducting magnet system 30 in which cooling may be provided via a two-stage cooling arrangement. For example, initial cooling may be provided via a helium bath, and subsequent cooling may then be provided via circulating liquid helium through cooling tubes.

[0036] Coil formers 16, 18 provide cold mass support structures that maintain the position of or support the magnetic coils 20, 22, respectively. Figure 2Shielded magnetic coil 22 is not shown). Coil formers 16, 18 are made of fiberglass composite material. In certain embodiments, coil formers 16, 18 may be formed of a thermally conductive material (e.g., aluminum). The cooling tube 12, which may be formed of any suitable metal (e.g., copper, stainless steel, aluminum, etc.), is fluidly connected to a liquid cryogen storage system 23, which has one or more liquid cryogen storage tanks 24. The cryogen storage system 23 contains a liquid cryogen used in a closed loop cooling system 10 to cool a cold block 60 including magnet coils 20, 22. In one embodiment, the cryogen is liquid helium. Fluid communication between the cooling tube 12 and the liquid helium storage tank 24 may be provided by one or more fluid channels 26 (e.g., fluid pipes, conduits, etc.). Thus, one or more storage tanks 24 provide liquid helium, which flows through the cooling tube 12 to cool the magnet coils 20, 22 by heat dissipation.

[0037] Collectively, the components of the magnet coils 20 and / or 22, the coil former / support structure 16 and / or 18, and the liquid cryogen storage tank 24 together form a cold block 60. As discussed in detail below, the cold block 60 is cooled to a target temperature. As used herein, "target temperature" refers to a cryogenic temperature sufficient to achieve superconducting operation. In one embodiment, the target temperature is approximately 4K. As used herein, "cold block" refers to any structure that is cooled to a target temperature via the cooling circuit 14 during normal operation. In the illustrated embodiment, the cooling circuit 14 does not include an exhaust port.

[0038] like Figure 2 As best illustrated, in one embodiment, the cooling tubes 12 may be in fluid communication with a vapor return manifold or passage 32 (e.g., a tube or conduit coupled to a recondenser 36) that receives helium vapor from the cooling tubes 12, which dissipates heat to the magnet coils 20, 22 and forms part of a closed loop cooling system.

[0039] The liquid helium storage tank 24 is in fluid communication with a cryogenic refrigerator 40, which includes a recondenser 36. In various embodiments, the recondenser 36 operates to form a free convection circulation loop to cool the magnet coils 20, 22 and the coil support shells 16, 18 to a cryogenic temperature, and fills the liquid helium storage tank 24 with liquid helium via one or more channels 44. The cryogenic refrigerator 40 can be a cold head or other suitable cryogenic refrigerator. The cryogenic refrigerator 40 also includes a motor 50.

[0040] like Figure 2 As illustrated, the cryogenic refrigerator 40 in various embodiments includes a recondenser 36 at the lower end of the cryogenic refrigerator 40 that recondenses boiled-off helium received from a vapor return manifold / channel 32 in parallel with the helium storage system 34. The recondenser 36 allows the liquid helium to reach the liquid helium reservoir 24.

[0041] The magnet coil 20, which is a cast coil in various embodiments, forms a main superconducting magnet 52, which is controlled during operation of the MRI system to acquire MRI image data, as is known in the art. Additionally, during operation of the MRI system, liquid helium traveling through the thermally coupled cooling tube 12 cools the superconducting magnet 52. The superconducting magnet 52 can be cooled to, for example, a superconducting temperature, such as 4.2 Kelvin (K). Part of the cooling process can include recondensing the vaporized helium gas into a liquid by the recondenser 36, and returning to the liquid helium tank 24 and cooling the vaporized helium.

[0042] In addition to cooling via circulating liquid helium through cooling tubes thermally connected to the magnet, cooling can also be provided by immersing the superconducting magnet coils in a liquid helium bath. In various embodiments, once cooled to operating temperature, the magnet coils can be cooled by thermal conduction and / or by thermosyphon cooling. However, as will be readily appreciated, whether cooling is achieved by circulating a liquid cryogen through a cooling loop in thermal communication with the magnet, or by immersing the magnet coils in a liquid cryogen bath, the coil former / support structure, magnet coils, and / or liquid cryogen reservoir form a cold mass 60 having a temperature of approximately 4.2K, which provides superconducting operation.

[0043] As depicted, the coil support shell 20, the cooling tube 12, and the liquid helium storage system 23 are disposed within a cryogenic vessel 48 (e.g., a helium vessel). The cooling tube 12 may be thermally coupled to the cryogenic vessel 48. The cryogenic vessel 48 may be partially filled with liquid helium to cool the main superconducting magnet 52, as described above. The cryogenic vessel 48 may be disposed within a thermal shield 54 (e.g., a thermally insulating radiation shield). The cryogenic refrigerator 40 (including the motor 50 and the recondenser 36) is located outside both the cryogenic vessel 48 and the thermal shield 54. The temperature at the thermal shield 54 may be approximately 50K.

[0044] A pump 72 (e.g., a vacuum pump or a roughing pump) is connected to the cryogenic vessel 48 to allow helium to be pumped directly out of the cryogenic vessel 48. For example, during evacuation and cooling, helium can be pumped out to reduce the pressure (e.g., to as low as tens of millitorr) and, therefore, reduce the temperature within the cryogenic vessel 48. The pump 72 can be coupled to a helium storage unit 74. A controller 76 (e.g., having processing circuitry and memory circuitry) is connected to the pump 72 to control the operation of the pumping, for example, to control the pressure level within the cryogenic vessel 48 during warming up. For example, the controller 76 can be connected to a temperature sensing device (not shown) or a pressure sensing device (not shown) that measures the temperature and pressure of the cryogenic vessel 48, respectively. Thus, the controller 76 can control the pump 72 so that a decompression in the helium vessel is provided during warming up.

[0045] As described above, the cooling system 10 for the superconducting magnet 52 is modified to form a sealed low cryogenic system. In addition to providing the cooling tube 10, the modification includes providing a feedthrough configuration that eliminates vibration transmission from the cold head and compensates for thermal expansion differences between the materials involved. This may include forming a vacuum seal 78 between any tubes or conduits extending between the recondenser 36 and the liquid storage system 23 or any other location (e.g., channels 26, 32) within the cryogenic container 48, thereby providing a feedthrough configuration (e.g., providing a tube passing through a sealed helium container) that eliminates vibration transmission from the cold head and compensates for thermal expansion differences between the materials involved. Other tubes or conduits coupled to the cryogenic container 48 may be vacuum sealed at the locations where they pass through the cryogenic container 48. Adding a vacuum seal makes the cryogenic container 48 a sealed cryogenic container 48.

[0046] The superconducting magnet 52 is electrically coupled to a superconducting switch 53. The retrofit cooling system 10 includes replacing the original main superconducting switch with a superconducting switch 53, which is configured to operate at a temperature of 80 Kelvin or lower. As described in more detail below, the superconducting switch 53 is both located within the helium container 48 and thermally isolated from the helium container. The superconducting switch 53 is configured to switch between a resistive mode and a superconducting mode. In addition, the superconducting switch 53 is thermally coupled to a corresponding tube 10 of the cooling tube 10. In addition, a high temperature superconducting current lead may be provided and coupled to the superconducting switch 53.

[0047] Figure 3 yes Figure 1 FIG. 1 is a cross-sectional view of a cooling tube 13 of a cooling system 10 of FIG. As described above, the cooling tube 12 may be formed of any suitable metal (e.g., copper, stainless steel, aluminum, etc.). As depicted, the cooling tube 12 is configured to be thermally coupled to the coils of a superconducting magnet. Specifically, a thermally conductive sheet 80 made of a metal (e.g., copper) is wrapped or disposed around the cooling tube 12. The thermally conductive sheet 80 is configured to maximize the heat transfer surface for the cooling tube 12. A thermally conductive plate 82 (e.g., a copper plate) is coupled to an end 84 of the thermally conductive sheet 80 via a fastener 86 (e.g., a bolt) and is clamped by the end of the thermally conductive sheet, which passes through the end 84 and the thermally conductive plate 82. The thermally conductive plate 82 may also be welded to the end 84 of the thermally conductive sheet 82. The thermally conductive plate 82 serves as a heat conducting conduit between the cooling tube 12 and the coils of the superconducting magnet. A single cooling tube 12 may be coupled to multiple coils of a superconducting magnet. Directly thermally coupling the coils to the superconducting magnets facilitates forming a sealed cryogenic system because the liquid helium is retained within the cooling tubes 12 .

[0048] Figure 4 is an example of a method for (eg, using a wire overwrap) connecting a coil 86 (eg, Figure 1 The coil 20 or 22 in the embodiment is thermally coupled to Figure 3Schematic diagram of the process of cooling the tube 12 in the embodiment of the present invention. The coil 86 is configured to be arranged on a coil former made of a fiberglass composite material. A flexible heat-conducting tape or braid 88 (e.g., made of a metal such as copper) is arranged or placed on top of the coil 86. Then, a heat-conducting wire overwrap 90 (e.g., made of a metal such as copper) is directly wrapped on top of the coil 86 (and around) to compress the flexible heat-conducting tape or braid 88 against the coil 86, thereby forming a better thermal contact. In certain embodiments, a thermally conductive paste may be arranged between the heat-conducting tape or braid 88 and the coil 86 to improve efficiency. The heat-conducting tape or braid 88 and the heat-conducting wire overwrap 90 thermally couple the coil 86 directly to the cooling tube 12 from a thermal coupling assembly 92. The end 94 of the heat-conducting tape or braid 88 is folded up and connected to the heat-conducting plate 82, which is coupled to the cooling tube 12. This configuration minimizes the surface area of ​​the heat-conducting tape or braid 88 with very high heat transfer along the ring direction. Brazing or welding between metal (eg, copper) parts and the cooling tubes 12 may be used to increase heat transfer efficiency.

[0049] Figure 5 The coil 86 (for example, using a laminated metal plate) of the superconducting magnet is exemplified. Figure 1 The coil 20 or 22 in the embodiment is thermally coupled to Figure 3 Schematic diagram of the process of cooling tube 12 in the coil 86. The coil 86 is configured to be disposed on a coil former made of a fiberglass composite material. A flexible heat conductive tape or braid 88 (e.g., made of a metal such as copper) is disposed or placed on top of the coil 86. A thermally conductive bonding plate 96 (e.g., made of a metal such as copper) is then fastened (e.g., bolted) to a flange of the coil former on top of a portion of the heat conductive tape or braid 88 (see Figure 6 ) to compress the flexible heat-conducting tape or braid 88 against the coil 86, thereby forming a better thermal contact. In certain embodiments, a thermally conductive paste may be disposed between the heat-conducting tape or braid 88 and the coil 86 to improve efficiency. The heat-conducting tape or braid 88 and the thermally conductive bonding plate 96 thermally couple the coil 86 directly to the cooling tube 12 from the thermal coupling assembly 98. The ends 94 of the heat-conducting tape or braid 88 are folded up and connected to the thermally conductive plate 82, which is coupled to the cooling tube 12. This configuration minimizes the surface area of ​​the heat-conducting tape or braid 88 with very high heat transfer along the annular direction. Brazing or welding between metal (e.g., copper) parts and the cooling tube 12 can be used to improve heat transfer efficiency.

[0050] Figure 6 yes Figure 5 86 is a cross-sectional view of a cooling tube directly thermally coupled to coil 86. As depicted, a thermally conductive bond sheet 96 (e.g., made of a metal such as copper) is fastened to coil former 102 (e.g., Figure 1 A flange 100 of the coil former 16 or 18 in the coil body is provided to compress the flexible heat conductive tape or braid 88 against the coil 86 to form a better thermal contact.

[0051] Figure 7 The liquid helium mesh 104 is used to cool the superconducting magnet of the MRI machine. The ring 106 represents the liquid helium mesh 104 that passes through the heat shield (e.g., Figure 2 Annulus 108 represents the entry point through a cryogenic vessel or helium vessel (e.g., Figure 2 1. The cryogenic vessel 48 in FIG. 1 is an entry point for the cryogenic vessel 48 in FIG. 1. The circle 110 represents the entry point or primary penetration point for the liquid helium to be provided to fill the cryogenic vessel. The primary penetration point may be heatsinked to the first stage on the bellows. The circle 112 represents the passage through the reverse magnetic coil former (e.g., Figure 1 The coil frame 18 in the cryogenic container is shown in Figure 1. The dotted line 114 represents the level of liquid helium in the cryogenic container. The sealed cryogenic system liquid helium storage tank 24 is located in the cryogenic container between the main coil frame and the anti-magnetic coil frame. Space availability can determine the storage of helium at ultra-high pressure. When the magnet starts to cool from room temperature, the gas will slowly turn into vapor and liquid. The recondenser 36 is located outside both the thermal shield and the cryogenic container. Each liquid helium storage tank 24 can be coupled to the recondenser 36 via a corresponding pipe 115, which extends from the inside of the cryogenic container to the outside of both the cryogenic container and the thermal shield.

[0052] As depicted, a web 116 of cooling tubes 12 is disposed throughout the cryogenic vessel, thereby forming a sealed cryogenic system. The cooling tubes 12 may be thermally coupled to the coils and the cryogenic vessel. Tubes 118 represent cooling elements for cooling the reverse magnetic coils (e.g., Figure 1 Tube 120 represents a cooling tube 12 for cooling the main coil (e.g., Figure 1 Tube 122 represents a cooling tube 12 for cooling a superconducting switch (e.g., Figure 2 The cooling tube 12 of the superconducting switch 53 in the cooling tube 12. The liquid helium in the tube can be converted into vapor when heat is transferred from various coils and other components. A portion of the cooling tube 12 can be fluidly coupled to a manifold 124, which merges the flow into a single tube to return the vapor liquid helium to the recondenser 36.

[0053] Some tubes or conduits (e.g., liquid / vapor lines between tank 24 and the recondenser) may need to pass through the vacuum boundary. These tubes or conduits will require vacuum feedthroughs (e.g., vacuum feedthroughs that form a vacuum seal) to eliminate vibration transmission from the cold head and compensate for thermal expansion differences between the materials involved. Figure 8 and Fig. 9 Various examples of vacuum feedthroughs for creating sealed cryogenic systems are described.

[0054] Figure 8 yes Figure 2 Schematic diagram of a vacuum feedthrough (e.g., bellows) between a recondenser 36 and a tank 24 (e.g., a liquid helium storage tank) of a cooling system 10 in FIG. As depicted, the recondenser 36 is located outside of a cryogenic vessel 48, and the tank 24 is disposed within the cryogenic vessel 48 (see FIG. Figure 2 ). The recondenser 36 is connected via a pipe 126 (e.g., Figure 2 4 (in the passage 44) is coupled to the tank 24. The tube 126 extends through an opening 128 in the cryogenic container 48. A bellows 130 is located at the opening 128 to form a vacuum feedthrough (e.g., to form a vacuum seal or boundary 132) for the tube 126 to extend through the opening 128. The bellows 130 is disposed along the tube 126 adjacent the opening 128. The tube 126 is a rigid tube. In addition, the tube 126 includes a nearly horizontal strain relief curve adjacent the tank 24 (as shown by reference numeral 134).

[0055] Fig. 9 yes Figure 2 Schematic diagram of a vacuum feedthrough (e.g., bellows) between a recondenser 36 and a tank 24 (e.g., a bimetallic joint) of a cooling system 10 in FIG. As depicted, the recondenser 36 is located outside of a cryogenic vessel 48, and the tank 24 is disposed within the cryogenic vessel 48 (see FIG. Figure 2 ). The recondenser 36 is connected via a pipe 136 (e.g., Figure 2 44 in the cryogenic container 48) is coupled to the tank 24. The tube 136 extends through the opening 128 in the cryogenic container 48. The bimetallic joint 138 is located at the opening 128 to form a vacuum feedthrough (e.g., to form a vacuum seal or boundary 140) for the tube 136 to extend through the opening 128. The bimetallic joint 138 is welded to the cryogenic container 48. The tube 136 extends through the bimetallic joint 138 so that the bimetallic joint 138 is disposed around the tube 136. The tube 136 is a high pressure flexible tube. As shown in FIG. Fig.10 As depicted, the bimetallic joint 138 includes an inner metal layer 140 that is joined to the outer surface of the tube 136 and an outer metal layer 142 that is joined to the cryogenic container 48, and the inner metal layer 140 is made of a different metal material than the outer metal layer 142. For example, the inner metal layer 140 may be made of stainless steel and the outer metal layer 142 may be made of aluminum.

[0056] Fig.11 is a schematic diagram of a superconducting switch 53. The superconducting switch 53 is configured to operate at a temperature of 80 Kelvin or lower. Specifically, the superconducting switch 53 is configured for low cryogen operation. The superconducting switch 53 is located in a cryogenic container (e.g., see Figure 2 ) is thermally isolated from the cryogenic container. The superconducting switch 53 is configured to switch between a resistance mode and a superconducting mode.

[0057] As depicted, the superconducting switch 53 includes a body 144. A thermally conductive metal sheet 146 (e.g., a copper sheet) is disposed around the body 144. The thermally conductive metal sheet 146 enables switch temperature control. The superconducting switch 53 includes a gasket insulator or a cryogenic insulator 148 (e.g., Z), the liner insulator or cryogenic insulator is arranged around the thermally conductive metal sheet 146. The liner insulator 148 is configured to thermally isolate the superconducting switch 53 from the cryogenic container. As disclosed herein, the liner insulator 148 operates normally at a low vacuum level. The superconducting switch 53 also includes a thermally conductive metal sheet 150 (e.g., a copper sheet) that is arranged around the liner insulator 148. The superconducting switch 53 is thermally coupled to the cooling pipe 12. Specifically, the thermally conductive metal sheet 150 is coupled via a thermal short circuit 152. The superconducting switch 53 is also coupled to the cooling pipe via a calibrated thermal shunt 154. The liner insulator 148 and the thermally conductive metal sheet 150 are configured to prevent the superconducting switch 53 from generating convection during the warm-up period of the superconducting magnet. The thermal isolation of the superconducting switch 53 enables the superconducting switch 53 to reach a higher temperature in the driving mode and thus achieve low vaporization during the warm-up period.

[0058] In order to reverse the production of a sealed cryogenic system, power leads comprising high temperature superconducting wires need to be coupled to superconducting switches. Fig.12 is a schematic diagram of a current or power lead 155 coupled to a superconducting switch 53. As depicted, the superconducting switch 53 is located within a cryogenic container 48. A first thermal station 156 (e.g., a pad) is located at a thermal shield 54 (which is approximately 50K), and a second thermal station 158 (e.g., a pad) is located at a cryogenic container 48 (e.g., approximately 4K). The first thermal station 156 and the second thermal station 158 are configured to provide thermal contact and electrical isolation for the current or power lead 155 at the thermal shield 54 and the cryogenic container 48, respectively. The superconducting current or power lead 155 includes a high temperature superconducting wire 160 (which serves as a warming lead) located outside the cryogenic container 48. A first end 162 (e.g., a cold end) of the high temperature superconducting wire 160 is coupled to the first thermal station 156 at the thermal shield 54. A second end 164 (e.g., a hot end) of the high temperature superconducting wire 160 is coupled to the second thermal station 158 at the cryogenic container 48. The two ends 162, 164 of the high temperature superconducting wire 160 may be coated with alumina ceramic for further electrical isolation. The superconducting current or power lead 155 also includes a low temperature superconducting wire 166. The low temperature superconducting wire 166 has a first end 168, which is coupled to the second thermal power station 158 outside the cryogenic container 48. The second end 170 of the low temperature superconducting wire 166 is coupled to the superconducting switch 53 inside the cryogenic container 48. The low temperature superconducting wire 166 enters the cryogenic container 48 from the outside of the cryogenic container 48 through an electrically isolating feedthrough 172.

[0059] Fig.131 is a flow chart of a method 174 for cooling a superconducting magnet of a magnetic resonance imaging system. The method 174 includes filling a sealed cryogenic vessel with liquid helium until a first desired temperature for cooling the superconducting magnet is reached, the superconducting magnet having a plurality of coils disposed around a body of a coil support structure, wherein the superconducting magnet is disposed within the sealed cryogenic vessel (frame 176). The method also includes stopping filling the sealed cryogenic vessel with the liquid helium when the first desired temperature is reached (frame 178). The method also includes pumping out excess helium using a rough vacuum pump coupled to the sealed cryogenic vessel after stopping filling the sealed cryogenic vessel with the liquid helium (frame 180). The method even includes activating a sealed cryogenic system including the pipe network disposed within the sealed cryogenic vessel by flowing a cryogen through a pipe network to cool the superconducting magnet to a second desired temperature, wherein the second desired temperature is lower than the first desired temperature (frame 182). After the excess helium is extracted, the pressure in the sealed cryogenic container produces internal convection to ensure uniform temperature distribution between the multiple coils and the sealed cryogenic container. The pressure of the remaining gas after cooling and pumping can be tens of millitorr. This pressure combined with internal convection can achieve uniform temperature distribution. Method 174 enables the modified sealed low cryogen system to cool the superconducting magnet faster than a typical sealed low cryogen system. In fact, method 174 enables the modified sealed low cryogen system to cool the superconducting magnet similar to a helium bath cooling system. In certain embodiments, the superconducting magnet can be directly cooled to a second desired temperature using only a helium gas flow through the pipeline network (i.e., without initially using a helium bath for cooling the superconducting magnet).

[0060] Fig.14 A schematic block diagram of an example MR system 200 with a modified sealed cryogen system disclosed herein is illustrated. The MR system 200 is used to obtain an image of a subject or for a spectroscopy application of the subject. In an example embodiment, the MR system 200 includes a magnet assembly 202, which includes a magnet 204. In some embodiments, the magnet 204 is a superconducting magnet formed by a plurality of magnetic coils wound around a magnetic coil support or coil former. The magnet 204 is configured to generate a polarized magnetic field. The magnet assembly 202 may include a cryostat or a cryogenic container 205 surrounding the magnet 204. The cryostat container 205 is typically filled with a cryogenic fluid or cryogen, which is used to cool the superconducting coil to an extremely low temperature (e.g., 4K) so that current continues to flow through the superconducting coil without resistance to maintain a uniform and static magnetic field after the power supply is disconnected. The cryogen can be helium, hydrogen, neon, nitrogen, or any combination thereof in liquid form, gas form, or a combination of liquid and gas forms. Helium is described as an example cryogen. Other cryogens may be used in the superconducting magnet assemblies described herein.

[0061] In an exemplary embodiment, the magnet assembly 202 may also include a heat shield assembly 206 that encloses the cryostat container 205 and the magnet 204 therein. In one embodiment, the heat shield assembly 206 may include an inner heat shield member 208 and an outer heat shield member 210. The inner heat shield member 208 is generally cylindrical in shape and radially placed inside the magnet 204. The inner heat shield member 208 is configured to prevent heat from radiating from a warm area where the subject is placed to a cold area where the magnet 204 is placed. The outer heat shield member 210 is concentrically arranged relative to the inner heat shield member 208. The outer heat shield member 210 may also have a generally cylindrical shape and be radially placed outside the magnet 204. The outer heat shield member 210 is configured to prevent heat from radiating from the environment to the magnet 204. The heat shield assembly 206 is made of a metal material (such as aluminum).

[0062] In an exemplary embodiment, the MR system 200 also includes a gradient coil assembly 212 placed inside the inner heat shield member 208. The gradient coil assembly 212 is configured to selectively apply one or more gradient magnetic fields along one or more axes (such as an x-axis, a y-axis, or a z-axis). The MR system 200 also includes a radio frequency (RF) coil 214. The RF coil 214 can be a transmitter coil configured to transmit RF pulses. The RF coil 214 can be a receiver coil configured to detect MR signals from a subject. The RF coil 214 can be a transmitting and receiving coil that both transmits and detects MR signals. The magnet assembly 202, the gradient coil assembly 212, and the main body RF coil 214 are collectively referred to as a scanner assembly 216 because the scanner assembly 216 is formed as a unit and is located in a scanner room. The scanner assembly 216 has a hole 217 in which the subject is positioned during scanning. Figure 1 The scanner assembly 216 shown is a closed hole system, where the hole is cylindrical. The scanner assembly 216 can be a magnet assembly of other designs, such as an open hole system, a bipolar electromagnet configuration, or a Hallbach configuration.

[0063] In an exemplary embodiment, the MR system 200 also includes a controller 218, a magnetic field control 220, a gradient field control 222, a memory 224, a display device 226, a transmit / receive (T / R) switch 228, an RF transmitter 230, and a receiver 232. In operation, a subject is placed in a bore 217 on a suitable support (e.g., a motorized operating table (not shown) or other patient table). The magnet 204 generates a uniform and static magnetic field B0 on ​​the bore 217. The strength and uniformity of the magnetic field B0 in the bore 217 and on the patient, respectively, are controlled by the controller 218 via the magnetic field control 220, which also controls the supply of excitation current to the magnet 204. The gradient coil assembly 212 is excited by the gradient field control 222 and is also controlled by the controller 218 so that one or more gradient magnetic fields are applied to the magnetic field B0. The RF coil 214 and the receiving coil (if provided) are selectively interconnected to one of the RF transmitter 230 or the receiver 232 through the T / R switch 228. The RF transmitter 230 and the T / R switch 228 are controlled by the controller 218 such that RF field pulses or signals are generated by the RF transmitter 230 and selectively applied to the subject for exciting magnetic resonance in the subject.

[0064] In an exemplary embodiment, after the RF pulses are applied, the T / R switch 228 is again actuated to decouple the RF transmit coil 214 from the RF transmitter 230. The detected MR signals are again communicated to the controller 218, which is capable of organizing the MR signals in a particular format for storage in the memory 224. The controller 218 includes a processor 234 that controls the processing of the MR signals to generate a signal representing an image of the patient, which is transmitted to the display device 226 to provide a visual display of the image.

[0065] The technical effects of the disclosed subject matter include providing a method for converting an existing bath cooled magnet (particularly those existing bath cooled magnets having a glass fiber composite structure) to a sealed low cryogen system while keeping the support structure, coil configuration and cryostat (e.g., helium container) almost intact, while replacing the main switch of the superconducting magnet with a switch configured for low cryogen operation and adding a superconducting current lead. In addition, the technical effects of the disclosed subject matter include providing a liquid helium net that allows direct cooling of a sealed helium container. In addition, the technical effects of the disclosed subject matter include providing a feed-through configuration (e.g., a tube for passing through a sealed helium container) that eliminates vibration transmission from a cold head and compensates for thermal expansion differences between the materials involved. Further, the technical effects of the disclosed subject matter include enabling a superconducting magnet disposed in a sealed cryogenic container to be cooled faster (e.g., from 1 week to 3 weeks to 1 day to 3 days), which is equivalent to the cooling of a bath cooled magnet. Still further, the technical effects of the disclosed subject matter include reducing helium consumption (e.g., due to the elimination of helium addition during the service life of the magnet), and thus reducing the costs associated with helium consumption. Still further, technical effects of the disclosed subject matter include eliminating the need for a quench exhaust line.

[0066] Reference is made to the technology presented and claimed herein and applied to physical and specific examples of a practical nature that clearly improves upon the present state of the art and, therefore, is not abstract, intangible, or purely theoretical. In addition, if any claim appended to the end of this specification contains one or more elements designated as "means for [performing] ... [function]" or "steps for [performing] ... [function]," it is intended that such elements be interpreted under 35 U.S.C. § 112(f). However, for any claim containing elements designated in any other manner, it is not intended that such elements be interpreted under 35 U.S.C. § 112(f).

[0067] This written description uses examples to disclose the subject matter, including the best mode, and also to enable any person skilled in the art to practice the subject matter, including making and using any devices or systems and performing any included methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insignificant differences from the literal language of the claims.

Claims

1. A superconducting magnet system for a magnetic resonance imaging system, the superconducting magnet system comprising: a coil support structure having a body; and a superconducting magnet having a plurality of coils disposed around the body of the coil support structure; and a helium container, the helium container containing the coil support structure and the superconducting magnet; and A cooling system, the cooling system comprising: a piping network disposed within the helium vessel and configured to transport helium within the helium vessel, wherein the piping network is reversely thermally coupled to the plurality of coils; a liquid helium storage system, the liquid helium storage system being located within the helium container; a helium recondenser located outside the helium vessel to recondense vapor helium into liquid helium; and one or more tubes coupling the helium storage system to the helium recondenser, wherein the location where the one or more tubes pass through the helium vessel is reverse vacuum sealed to make the helium vessel a sealed helium vessel, wherein the cooling system is configured to maintain a uniform temperature between the sealed helium vessel and the plurality of coils.

2. The superconducting magnet system of claim 1 , further comprising a respective bellows located at a location where each respective tube of the one or more tubes passes through the helium vessel, wherein each respective bellows forms a vacuum seal and is coupled to the respective tube of the one or more tubes, and the one or more tubes are rigid.

3. The superconducting magnet system of claim 1 , further comprising a respective bimetallic joint disposed around each of the one or more tubes at a location where each respective tube of the one or more tubes passes through the helium vessel, wherein each respective bimetallic joint forms a vacuum seal and the one or more tubes are flexible.

4. The superconducting magnet system of claim 3 , wherein each respective bimetallic joint comprises an inner metal layer joined to the respective tube and an outer metal layer joined to the helium vessel, and the inner metal layer is made of a different metal material from the outer metal layer.

5. The superconducting magnet system of claim 1 , wherein each of the plurality of coils is thermally coupled to a corresponding tube of the tube network via a thermal coupling assembly, wherein the thermal coupling assembly comprises a flat thermally conductive metal tape disposed on the corresponding coil, a thermally conductive metal wire outer wrap wound around both a portion of the flat thermally conductive metal tape and the corresponding coil, and an end of the flat thermally conductive metal tape is coupled to a thermally conductive metal plate, and the thermally conductive metal plate is coupled to the corresponding tube. 6 . The superconducting magnet system of claim 5 , wherein the thermal coupling assembly comprises a thermally conductive metal sheet wrapped around the respective tube, and the thermally conductive metal plate is coupled to the thermally conductive metal sheet.

7. The superconducting magnet system of claim 1 , wherein each of the plurality of coils is thermally coupled to a corresponding tube of the tube network via a thermal coupling assembly, wherein the thermal coupling assembly comprises a flat thermally conductive metal strip disposed on the corresponding coil, a thermally conductive metal plate disposed around a portion of the flat thermally conductive metal strip, and an end of the flat thermally conductive metal strip is coupled to an additional thermally conductive metal plate, and the additional thermally conductive metal plate is coupled to the corresponding tube.

8. The superconducting magnet system of claim 7, wherein the thermal coupling assembly comprises a thermally conductive metal sheet wrapped around the respective tube, and the additional thermally conductive metal plate is coupled to the thermally conductive metal sheet.

9. The superconducting magnet system of claim 1 , further comprising a superconducting switch configured to operate at a temperature of 80 Kelvin or less, wherein the superconducting switch is both located within the helium vessel and thermally isolated from the helium vessel, the superconducting switch is configured to switch between a resistive mode and a superconducting mode, and the superconducting switch is thermally coupled to a corresponding tube of the tube network.

10. The superconducting magnet system of claim 9, wherein the superconducting switch comprises a liner insulator disposed around a body of the switch and configured to thermally isolate the superconducting switch from the helium vessel, the superconducting switch comprises a thermally conductive metal sheet disposed around the liner insulator and thermally connected to the corresponding tube, and wherein the liner insulator and the thermally conductive metal sheet are configured to prevent convection of the superconducting switch during a warm-up of the superconducting magnet.

11. The superconducting magnet system of claim 9, further comprising a power lead coupled to the superconducting switch, wherein the power lead comprises a high temperature superconducting wire coupled to a heat sink located outside the helium vessel, wherein an end of the high temperature superconducting wire coupled to the heat sink is electrically isolated, and wherein the power lead comprises a low temperature superconducting wire having a first end coupled to the heat sink and a second end coupled to the superconducting switch, and the low temperature superconducting wire enters the helium vessel from outside the helium vessel through an electrically isolated feedthrough.

12. The superconducting magnet system of claim 1, wherein the body of the coil support structure is made of a fiberglass composite material.

13. A method for cooling a superconducting magnet of a magnetic resonance imaging system, the method comprising: filling a sealed cryogenic vessel with liquid helium until a first desired temperature is reached for cooling the superconducting magnet, the superconducting magnet having a plurality of coils disposed around a body of a coil support structure, wherein the superconducting magnet is disposed within the sealed cryogenic vessel; stopping filling the sealed cryogenic container with the liquid helium when the first desired temperature is reached; After stopping filling the sealed cryogenic vessel with the liquid helium, pumping out excess helium using a rough vacuum pump coupled to the sealed cryogenic vessel; as well as A sealed cryogenic system including the network of pipes disposed within the sealed cryogenic vessel is activated by flowing a cryogen through a network of pipes to cool the superconducting magnet to a second desired temperature, wherein the second desired temperature is lower than the first desired temperature.

14. The method of claim 13, wherein the pressure in the sealed cryogenic vessel after pumping out the excess helium creates internal convection to ensure uniform temperature distribution between the plurality of coils and the sealed cryogenic vessel.

15. The method of claim 13, wherein each of the plurality of coils is thermally coupled in reverse to a corresponding tube of the tube network via a thermal coupling assembly, wherein the thermal coupling assembly comprises a flat thermally conductive metal strip disposed on the corresponding coil, a thermally conductive metal wire overwrap wound around both a portion of the flat thermally conductive metal strip and the corresponding coil, and an end of the flat thermally conductive metal strip is coupled to a thermally conductive metal plate, and the thermally conductive metal plate is coupled to the corresponding tube.

16. The method of claim 13, wherein the magnetic resonance imaging system comprises a cooling system for the superconducting magnet, wherein the cooling system comprises: a liquid helium storage system, the liquid helium storage system being located in the sealed cryogenic container; a helium recondenser located outside the cryogenic vessel to recondense vapor helium into liquid helium; and one or more tubes coupling the helium storage system to the helium recondenser, wherein the one or more tubes are reverse vacuum sealed at locations where they pass through the sealed cryogenic vessel to make the cryogenic vessel the sealed cryogenic vessel, and wherein the cooling system is configured to maintain a uniform temperature between the sealed helium vessel and the plurality of coils.

17. A method according to claim 16, wherein the cooling system includes a respective bimetallic joint disposed around each of the one or more tubes at a location where each respective tube of the one or more tubes passes through the sealed cryogenic container, wherein each respective bimetallic joint forms a vacuum seal, and the one or more tubes are flexible.

18. The method of claim 13, wherein the magnetic resonance imaging system comprises a cooling system for the superconducting magnet, wherein the cooling system comprises a superconducting switch, the superconducting switch being configured to operate at a temperature of 80 Kelvin or less, wherein the superconducting switch is both located within the sealed cryogenic vessel and thermally isolated from the sealed cryogenic vessel, the superconducting switch being configured to switch between a resistive mode and a superconducting mode, and the superconducting switch being thermally coupled to a corresponding tube of the tube network.

19. The method of claim 13, wherein the cooling system comprises a power lead coupled to the superconducting switch, wherein the power lead comprises a high temperature superconducting wire coupled to a heat sink located outside the sealed cryogenic container, wherein an end of the high temperature superconducting wire coupled to the heat sink is electrically isolated, and wherein the power lead comprises a low temperature superconducting wire having a first end coupled to the heat sink and a second end coupled to the superconducting switch, and wherein the low temperature superconducting wire enters the sealed cryogenic container from outside the sealed cryogenic container through an electrically isolating feedthrough.

20. A magnetic resonance imaging (MRI) system, comprising: a coil support structure having a body, wherein the body of the coil support structure is made of a fiberglass composite material; and a superconducting magnet having a plurality of coils disposed around the body of the coil support structure; and a helium container, the helium container containing the coil support structure and the superconducting magnet; and A cooling system, the cooling system comprising: a piping network disposed within the helium vessel and configured to transport helium within the helium vessel, wherein the piping network is reversely thermally coupled to the plurality of coils; a liquid helium storage system, the liquid helium storage system being located within the helium container; a helium recondenser located outside the helium vessel to recondense vapor helium into liquid helium; and one or more tubes coupling the helium storage system to the helium recondenser, wherein the location where the one or more tubes pass through the helium vessel is reversely vacuum sealed to make the helium vessel a sealed helium vessel, wherein the cooling system is configured to first cool the superconducting magnet to a first desired temperature by filling the sealed helium vessel with liquid helium, and then cool the superconducting magnet to a second desired temperature by flowing the helium through the tube network, wherein the second desired temperature is lower than the first desired temperature.

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