Superconducting magnet assembly

Abstract

A superconducting magnet assembly, the superconducting magnet assembly comprising: a main magnet assembly (10), the main magnet assembly including at least one toroidal coil (12) arranged around an axis, and at least one shielding coil (16), the shielding coil having a diameter larger than that of the main magnet assembly (10) and arranged around the axis. At least one support member (20; 60) is attached to the shielding coil (16) and the main magnet assembly (10).

Description

Technical Field

[0001] The present invention relates to superconducting magnets and, in particular, to superconducting magnets for use in magnetic resonance imaging (MRI) systems and nuclear magnetic resonance (NMR) systems. Background Art

[0002] Typically, such superconducting magnets include active shielding to reduce stray magnetic fields. The active shielding includes a counter-running coil located outside the main electromagnetic coil. For an effective design, there should be a large radial gap between the shielding coil and the inner magnet. In operation, the shielding coil typically experiences many tons of axial body forces and must be accurately positioned. It can be difficult to support these shielding coils in an efficient and cost-effective manner.

[0003] The present invention solves this problem and is intended to provide an arrangement for supporting these shielding coils in an efficient and cost-effective manner.

[0004] Figure 1 A conventional superconducting magnet for an MRI system as described in WO2013 / 102509 is shown. The self-supporting main magnet assembly 1 may include at least one toroidal superconducting main coil. A plurality of shielding coils 6 having a diameter larger than the diameter of the main coil are provided, and the shielding coils 6 are coaxially placed with the main coil about an axis A-A (schematically shown). The intermediate coil support structure 3 is fixed to the self-supporting main magnet assembly 1 and the journal 8 holding the shielding coils 6 to hold the main coil and the shielding coils in their respective correct positions.

[0005] The coil-less structure 1 is particularly suitable for very lightweight magnet structures, such as those required for cryogen-free magnets that require a fast cool-down time. For very thin coils, other conventional arrangements become impracticable. As Figure 1 in the self-supporting main magnet assembly 1 shown, it may become impracticable to directly suspend the "cooling block" from the vacuum vessel, as it may cause an unacceptable level of deformation of the magnet assembly.

[0006] When it is required to keep the "cooling block" low, i.e., when the equipment block maintained at the operating temperature of a superconducting magnet, which is typically below 20K, is typically about 4K, the above problems, including the solution proposed by WO2013 / 102509, become difficult to solve. Recent developments include conduction-cooled magnets that are not provided with a bath of liquid cryogen. To minimize the cool-down time of such structures, the coils and, if provided, the coil former tend to become very thin and have reduced inherent stiffness due to the drive to reduce mass. Nevertheless, it is necessary to allow the suspension of the cooling block within the cryostat without excessive deformation, and it becomes difficult to provide an arrangement for supporting the shielding coils from the main magnet assembly.

[0007] A coil-free full-binding solution where the coil is bound to the side of an annular spacer in a similar radial range can be used for very light structures, such as those required for a cryogen-free magnet with a fast cool-down time. As the coil becomes thinner, known coil support solutions become increasingly difficult or impossible to implement. The cooling block may need to be significantly strengthened to allow the magnet suspension to be directly connected to the cooling block. There is a need for a lightweight and robust structure that supports the shield coil around the entire circumference of the coil without subjecting any of the coils to concentrated mechanical loads that could otherwise cause the coil to deform. Summary of the Invention

[0008] The present invention is intended to provide a thin and lightweight support for mounting a thin and lightweight shield coil onto a thin and lightweight main magnet assembly. The support of the present invention adds relatively little mass to the cooling block, which maintains the cooling efficiency of the conduction-cooled magnet. The resulting cooling block structure has high inherent stiffness when fully assembled, minimizing coil deformation during suspension while minimizing thermal and electromagnetic loads.

[0009] In use, due to the interaction of the magnetic field generated by the superconducting coil with the magnetic field generated by the entire superconducting magnet, each superconducting magnet coil is subject to electromagnetic loads including radial and axial forces. Each superconducting coil is subject to an axial body force that typically acts outward from the mid-plane but can also act inward towards the mid-plane, depending on the magnet design, and each superconducting coil is also subject to a significant radial force that typically acts in the radially outward direction but can also act radially inward in some cases, depending on the magnet design. For thin coils, if supported at only a few points, this combination of forces due to electromagnetic loads can cause the superconducting coil to bend and at least cause local deformation that results in high local stresses and a low magnetic field uniformity. Conventionally, this stress concentration problem has been solved by making the superconducting coil structure heavier and more expensive. The present invention provides a continuous support around the circumference of the superconducting coil such that stress concentration is effectively eliminated, deformation is minimized, and buckling modes are avoided. This in turn minimizes any resulting degradation in magnetic field uniformity.

[0010] The present invention seeks to provide a lightweight and rigid structure that supports the shield coil around the entire circumference of the coil without subjecting any of the coils to concentrated mechanical loads.

[0011] Accordingly, the present invention provides an apparatus as defined in the appended claims. Brief Description of the Drawings

[0012] The above and other objects, features and advantages of the present invention will become more apparent from the following description of certain embodiments of the present invention when read in conjunction with the accompanying drawings, in which:

[0013] Figure 1 Schematically shows a conventional arrangement structure of a shield coil support structure;

[0014] Figure 2 Schematically shows an arrangement structure of a shield coil support structure according to an embodiment of the present invention;

[0015] Figure 2A Shows details of alternative features of a specific embodiment of the present invention;

[0016] Figure 3 Shows Figure 2 an enlarged view of certain features of;

[0017] Figure 4 Schematically shows an arrangement structure of a shield coil support structure according to an alternative embodiment of the present invention;

[0018] Figure 5 Shows another alternative embodiment of the present invention, in which a shield coil support arrangement is provided and an arrangement for supporting the entire cooling block within an outer vacuum chamber (OVC) is shown; and

[0019] Figure 6 Shows another embodiment of the present invention in which a conical support is used as part of a thermal radiation shield. Detailed Description

[0020] Figure 2 Shows a partial cross-section of an embodiment of the present invention that is substantially rotationally symmetric about axis A-A and reflection symmetric about central plane C-C.

[0021] As illustrated by the exemplary embodiment schematically shown in Figure 2 the present invention provides one or more conical annular supports 20 for connecting a thin and flexible inner magnet (“main magnet assembly”) 10 to a thin shield coil 16. Although all these components are flexible and relatively mechanically weak before assembly, when connected together, they form a very rigid and extremely light structure. Figure 3 Shows Figure 2 an enlarged view of certain features of.

[0022] In Figure 2Among them, the main magnet assembly 10 not shown in detail includes at least one superconducting coil. A shielding coil 16 having a diameter larger than the diameter of the main magnet assembly 10 is provided. In the illustrated embodiment, an end ring 18 is provided, and the end ring 18 is coupled to the axially outer end of each respective shielding coil 16. The end ring 18 may be of resin-impregnated fibrous material.

[0023] According to a feature of the present invention, a conical annular support 20 is provided. The radially inner peripheral portion 22 of the conical annular support 20 is attached to the main magnet assembly 10. In the illustrated example, this is achieved by bolts 24 passing through an inner flange 26 in the material of the conical annular support 20 and into threaded holes in the material of a spacer, or into threaded inserts held within the material of the spacer itself, the inner flange 26 pointing axially inward from the radially inner peripheral portion 22 of the annular support 20. The radially outer peripheral portion 28 of the conical annular support 20 is attached to one of the shielding coils 16. In the illustrated embodiment, this is achieved by bolts 30 axially passing through a circumferentially radially extending outer flange 32 in the material of the conical annular support 20 and into threaded holes in the material of the end ring 18, or into threaded inserts held within the material of the end ring 18 itself.

[0024] In a preferred embodiment, a similar arrangement is provided at the other axial end of the main magnet assembly 10 to provide support for the axially outer end of the other shielding coil.

[0025] In a preferred embodiment, the conical annular support 20 or each conical annular support 20 is formed of a thin metal plate, such as 1 mm thick stainless steel, aluminum, or aluminum alloy, although each conical annular support 20 may be made of other materials such as composite materials like CFRP or GRP.

[0026] In some embodiments, such as Figure 2 as illustrated, one or more suspension elements, such as leg supports 34, may be attached to the main magnet assembly 10. As illustrated, and conveniently, the leg supports 34 may be attached to the main magnet assembly 10 by one or more of the bolts 24 that attach the conical annular support 20 to the main magnet assembly 10. The other end of the leg support 34 may be attached to the inner surface of an outer vacuum container (OVC) ( Figure 2 not shown), which outer vacuum container defines a vacuum region around the magnet structure. In this way, the weight of the main magnet assembly 10 can be borne by the OVC through the tension in the leg supports 34. The weight of the shielding coil 16 can be borne by the OVC through the tension in the leg supports 34 and the tension and compression in the conical annular support 20.

[0027] In use, the shield coil 16 is subject to many tons of axially outward forces, which may be sufficient to deform the conical annular support 20 or each conical annular support 20. In Figure 2 the view shown in Figure 2 , such deformation will appear as follows: the shield coil 16 rotates a certain degree around the radially inner peripheral portion 22 of the annular support 20, and the material of the conical annular support 20 deforms. This in turn will mean that the radially extending outer flange 32 no longer points radially, and may cause the shape of the shield coil 16 to deform. To resist such deformation, in certain embodiments of the present invention, an axial rod 36 may be provided, which extends between the shield coil support structures at opposite ends of the magnet structure. For example, eight such rods may be provided, which are circumferentially distributed around the magnet structure. The axial rod 36 provides additional stiffness in the axial direction and thus prevents excessive distortion of the conical annular support 20. This additional stiffness provided by the axial rod 36 may allow the use of thinner materials to form the conical annular support 20. In a preferred embodiment, a conical annular support 20 is provided near each axial end of the main magnet assembly 10, and the axial rod 36 extends between the two conical annular supports 20. In

[0028] the embodiment shown in Figure 2 , flat areas 38 are provided at circumferential intervals near the outer flange 32, and the corresponding axial rods 36 are mounted to the corresponding flat areas 38 by bolts or by attaching nuts to the threaded portions of the axial rods 36 themselves.

[0029] In Figure 2A the alternative arrangement shown in Figure 2 , the axial rod 40 is a hollow rod, and threaded bolts 42 or the like are installed in each end of the axial rod 40 so that the axial rod 40 can be mounted to the conical annular support 20 in the same manner as the

[0030] axial rod 36 of

[0031] The conical annular support member 20 is attached to the main magnet assembly 10 at least spaced apart around the circumference of the main magnet assembly, for example, attached to the main magnet assembly 10 by bolts 24. In some embodiments, the conical annular support member 20 may be continuously attached to the main magnet assembly 10, for example, attached to the main magnet assembly 10 by a resin-impregnated glass tape overlapping with the inner flange 26 and the main magnet assembly. In alternative embodiments, the conical annular support member 20 is bonded to the main magnet assembly 10 or clamped to the main magnet assembly 10 by a mechanical compression band. Concealed fasteners such as the bolts 24 shown in the drawings simplify manufacturing, but in embodiments where the conical annular support member 20 is a resin-impregnated composite material, adhesive joints may be found to be advantageous.

[0032] In the radial direction, the conical annular support member 20 provides rigid support and maintains the annular shape of the main magnet assembly 10. This is necessary to enable the magnetic field to be sufficiently uniform.

[0033] The conical annular support member 20 is attached to the shield coil 16 at least spaced apart around the circumference of the main magnet assembly, for example, attached to the shield coil 16 by bolts 30. In some embodiments, the conical annular support member 20 may be continuously attached to the main magnet assembly 10, for example, attached to the main magnet assembly 10 by a resin-impregnated glass tape overlapping with the inner flange 26 and the main magnet assembly. In the radial direction, the conical annular support member 20 provides rigid support and maintains the annular shape of the shield coil 16. This ensures that the shield coils are precisely positioned relative to each other and relative to the main magnet assembly 10. By supporting the shield coils around the entire circumference of the shield coils, out-of-plane bending and stress concentration of the shield coils can be avoided, although both occur in conventional methods of using discrete tensioning elements to support the shield coils.

[0034] The conical annular support member 20 provides axial stiffness and radial stiffness to resist mechanical loads, thermal loads, and electromagnetic loads.

[0035] The conical annular support member 20 may also provide a mounting location for a tensioning suspension system as discussed below with reference to Figure 5 or provide a mounting location for a tensioning or compression suspension system such as a column support member 34 using the inner flange 26 of the conical annular support member 20 as discussed above with reference to Figure 2 The column support member 34 may be attached to the conical annular support member 20 as Figure 2 and Figure 3 illustrated, but may alternatively be mounted to the main magnet assembly 10, preferably near the conical annular support member 20. The conical annular support member 20 holds the main magnet assembly 10 in a circular shape and thus helps prevent the column support member from distorting the inner magnet.

[0036] The constraints of the main magnet assembly 10 and the shield coil 16 provided by the conical annular support 20 can be balanced by appropriately selecting the parameters of the conical annular support 20, such as the cone material, thickness, and inclination angle β, according to the axial stiffness requirements. If axial rods are provided, further adjustment of the mechanical properties of the structure can be achieved by adjusting the stiffness, number, and position of the axial rods 36, 40.

[0037] In certain embodiments of the present invention, the conical annular support 20 can be made of a material with a relatively high thermal conductivity, such as copper or aluminum. This will provide a high thermal conductivity path between the main magnet assembly 10 and the shield coil 16. This will contribute to thermal uniformity, especially in conduction-cooled magnets.

[0038] Conventionally, a terminal area is provided on the main magnet assembly 10, such as shown in Figure 2 39. There, the ends of the superconducting wires forming the main magnet coil and the shield coil are placed together and electrically connected to a superconducting persistent switch, also known as an electromagnetic switch, and a power supply, a stop load, etc. Conventionally, such a terminal area can be provided on the radially outer surface of the main magnet assembly 10. The conical annular support 20 of the present invention allows such areas to be particularly easily accessible. In the case where the tension rods 36, 40 are omitted, for example, in an embodiment where the conical annular support 20 itself provides sufficient stiffness to position and hold the shield coil, the accessibility of these areas will be further improved.

[0039] The conical annular support 20 can be manufactured in a cost-effective manner by fabricating, spinning, or pressing a metal plate or by composite lamination. Compared with conventional support structures and magnet structure supports for shield coils, the support structure provided by the present invention has a much lower number of components and complexity.

[0040] Figure 4 Details of an alternative embodiment of the present invention are shown, in which the shield coil 16 is not provided with end rings ( Figure 2In 18). Alternatively, a cladding layer 41 of composite material, such as resin-impregnated glass fiber or resin-impregnated carbon fiber, is at least partially provided on the radially outer surface of each shielding coil 16. The cladding layer 41 axially protrudes beyond the axially outer ends of the corresponding shielding coils 16. In the illustrated embodiment, the conical annular support 20 has a radially outer end that axially rotates towards the axial center of the magnet to form an axially directed outer flange 42. In the illustrated embodiment, the cladding layer 41 is attached to the axially directed outer flange 42 by fasteners such as rivets 44. Such fasteners may be provided at circumferential intervals around the shielding coil 16. The number of fasteners and thus the spacing of the fasteners should be determined to ensure that the shielding coil 16 does not deform significantly during normal use. This determination should also take into account the mechanical strength of the cladding layer 41, which will provide annular support for the shielding coil.

[0041] Similar to Figure 2 the embodiment of, the axial rod 36 or the axial rod 40 is preferably attached to the corresponding flat area 46 provided near the outer flange 42. In either embodiment, the flat area may be provided axially inside or outside the cone of the conical annular support 20. In some embodiments, since the conical annular support 20 preferably uses relatively thin material, the flat area 46 for attaching the axial rod 36 or the axial rod 40 is provided with a reinforcement such as a material plate, thereby effectively locally increasing the material thickness of the conical annular support 20, or press-in features or screw-in features in the material of the conical annular support 20.

[0042] In other embodiments not specifically illustrated, the orientation of the conical annular support 20 is reversed, i.e., the conical annular support 20 reaches the axial inner edge of the shielding coil and axially inclines outwardly towards the surface of the main magnet assembly 10. In another embodiment not specifically illustrated, each shielding coil 16 may be provided on the axial side of the conical annular support 20 opposite to the axial side presented so far. The conical annular support 20 may be replaced with annular supports of other shapes to improve the required structural characteristics.

[0043] Figure 5 Another embodiment of the present invention is illustrated. In this embodiment, the conical annular support 20 is adapted to support the weight of the main magnet assembly 10 through support rods 70, which are supported against the outer vacuum vessel (OVC) 50. The support rods 70 preferably also support the weight of the thermal radiation shield 52. The OVC 50 provides a vacuum volume surrounding the superconducting magnet. The thermal radiation shield 52 (at approximately 50K) must of course be held and mechanically supported in such a way as to ensure thermal insulation between the thermal radiation shield 52 and the OVC (at approximately 300K) and the superconducting magnet (at approximately 4K).

[0044] The thermal radiation shield 52 is located between the superconducting magnet and the OVC. The thermal radiation shield 52 prevents thermal radiation from the inner surface of the OVC, which is typically at about 300 K, from reaching the superconducting magnet, which is typically at about 4 K. The thermal radiation shield 52 is typically cooled to a temperature of about 50 K. Cryocoolers typically provide greater cooling capacity at 50 K than at 4 K, so it is useful to remove any heat inflow at 50 K rather than attempting to remove heat inflow at 4 K. Thus, thermal radiation reaching the superconducting magnet from the thermal radiation shield 52 is emitted only at 50 K and thus carries much less energy than thermal radiation emitted at 300 K, allowing the heat inflow reaching the superconducting magnet from the thermal radiation shield 52 to be removed at 4 K by the cryocooler.

[0045] Figure 5 An embodiment of the present invention is illustrated that is capable of such retention and mechanical support. As is conventional in itself, a multi-layer insulation (MLI) 54 can be provided in the space between the OVC and the thermal radiation shield. The MLI typically comprises multiple layers of aluminized polyester sheets. For ease of representation, the MLI is shown intermittently, but in practice will substantially surround the thermal radiation shield 52. Its purpose is to reflect thermal radiation from the OVC and establish a stable thermal gradient between the OVC and the thermal radiation shield.

[0046] Figure 5 The embodiment shares many features with other embodiments of the present invention, and these features carry the same reference numerals as those carried in the previous figures.

[0047] A plurality of rod bosses 62 are introduced into the conical annular support 60. For example, four such rod bosses can be provided circumferentially distributed around each conical annular support 60. Each rod boss in the rod bosses is preferably made of a material such as resin-impregnated fiberglass or carbon fiber, stainless steel, or titanium, and includes a radially directed through-hole 68 that is inclined with respect to the axis A-A to receive a corresponding support rod 70. Each rod boss 62 can be shaped or otherwise arranged to be held in place within the conical annular support 60.

[0048] In a preferred embodiment, eight such bosses are provided, with four bosses present on each of the two conical annular supports 60, each of the two conical annular supports 60 being located at a respective end of the superconducting magnet assembly. The inclination angle β of each conical annular support preferably corresponds to the orientation of the support rod 70 mounted to the rod boss 62. Each of the eight support rods 70 is arranged at a complex angle between the OVC and the respective conical annular support 60 to provide mechanical support for the weight of the superconducting magnet structure through the material of the conical annular support 60, wherein each support rod 70 is mounted to a respective one of the rod bosses 62. By providing the tension rods 70 following the cone angle, the distortion and bending of the material of the conical annular support 60 are minimized. Thus, it is possible to provide support for the weight of the superconducting magnet without the need for lengthening of the entire structure.

[0049] In the illustrated embodiment, both ends of the support rod 70 are threaded. At the radially inner end of the support rod, the support rod 70 passes through the rod boss 62. At the radially outer end of the support rod, the support rod passes through a hole or notch in the mounting point 72, which is attached to the inner surface of the OVC by welding or some similar permanent attachment means. The two threaded end portions of the support rod 70 are respectively fastened in place with nuts and preferably also with washers. The support rod 70 is respectively tensioned by tightening the respective nuts so as to restrain and support the superconducting magnet structure within the OVC.

[0050] Figure 5 Another preferred feature of the embodiment is that the weight of the thermal radiation shield 52 is borne by the support rods 70. For this purpose, the shield support 74 is mounted on the support rods 70. At least one shield support 74 is mounted on at least one support rod, but preferably, at least one shield support 74 is mounted on each support rod 70. Each shield support 74 is attached to the respective support rod at an appropriate location such that, under stable thermal conditions, the temperature of the support rod at the location of the shield support 74 will be approximately the same as the temperature of the thermal radiation shield, such that in use, little heat transfer occurs between the thermal radiation shield and the support rod 70. The shield support 74 is attached to the thermal radiation shield such that the weight of the thermal radiation shield is at least partially borne by the shield support 74.

[0051] In certain embodiments of the present invention, such as in Figure 6In the embodiments illustrated as examples herein, the conical annular supports 20, 60 form part of an "opaque" thermal radiation shield. For example, an opaque lightweight tube 80, such as a thin conductive metal tube 80 like aluminum foil or copper foil or a composite substrate covered in foil, can be provided between the radially outer ends of the conical annular supports 20, 60 of any embodiment of the present invention to form a radiation shield for the magnet cooling block including the main magnet assembly 10 and the shield coil 16. In this way, the conical annular support 20, the conical annular support 60, the lightweight tube 80, and the main magnet assembly 10 form an isothermal volume in which the terminal portion 39 can be accommodated without additional thermal shielding. The main magnet assembly 10 can be placed within the isothermal volume by adding a thermally conductive layer 80, such as an aluminum foil or copper foil thermally conductive layer 80, to the surface of the main magnet assembly, otherwise these surfaces would be exposed outside the isothermal volume.

[0052] Accordingly, the present invention provides a superconducting magnet assembly comprising: a main magnet assembly 10 including at least one annular superconducting coil arranged about an axis A-A; and at least one shield coil 16 arranged about the axis A-A and having a diameter larger than that of the main magnet assembly 10, wherein at least one annular support is provided attached to the shield coil 16 and the main magnet assembly 10.

[0053] In a preferred embodiment, the annular support can be conical; and in another preferred embodiment, the annular support can be described as a thin conical section spanning the radial gap between the inner (main) coil and the outer (shield) coil.

[0054] This arrangement provides a lightweight and mechanically rigid shield coil support suitable for supporting very thin coils. By varying the cone geometry, thickness, and material, the mechanical properties of the shield coil support can be easily adjusted. The support structure of the present invention is lightweight and suitable for magnets with no coolant or conduction cooling, as such magnets need to be rapidly cooled from room temperature during installation. The shield coil supports 20, 60 of the present invention also have a low material content and corresponding low mass, allowing for easier magnet positioning, shorter cooling times, and reduced transportation costs. The annular shield coil support structure 20, 60 of the present invention is simple and cost-effective. In a preferred embodiment, using the conical support structure of the present invention allows unobstructed access to the terminal region of the magnet.

[0055] Due to the mechanical stiffness imparted by the annular shield coil support, the annular shield coil support structure of the present invention allows a very lightweight magnet cooling block to be mechanically suspended within a cryostat without excessive deformation.

[0056] In certain embodiments of the present invention, the annular supports 20, 60 form part of a thermal radiation shield around the cooling block, and the annular supports 20, 60 also provide a light-tight isothermal volume for mounting terminal components and electromagnetic switches.

Claims

1. A superconducting magnet assembly, the superconducting magnet assembly comprising: A main magnet assembly (10), the main magnet assembly (10) including at least one toroidal coil arranged around an axis; And at least one shielding coil (16), the shielding coil (16) having a diameter larger than that of the main magnet assembly (10) and arranged around the axis, wherein at least one conical toroidal support member (20; 60) attached to the shielding coil (16) and the main magnet assembly (10) is provided, the superconducting magnet assembly further including an end ring (18), the end ring (18) being coupled to the axially outer end of the shielding coil (16), and the radially outer peripheral portion (28) of the material of the conical toroidal support member being attached to the end ring.

2. The superconducting magnet assembly according to claim 1, wherein, An outer flange (32) is provided in the material of the toroidal support member (20), and the toroidal support member (20) is attached to the shielding coil (16) through the outer flange (32).

3. The superconducting magnet assembly according to claim 2, wherein, The outer flange (32) extends radially and is attached to the end ring (18).

4. A superconducting magnet assembly, the superconducting magnet assembly comprising: A main magnet assembly (10), the main magnet assembly (10) including at least one toroidal coil arranged around an axis; And at least one shielding coil (16), the shielding coil (16) having a diameter larger than that of the main magnet assembly (10) and arranged around the axis, wherein at least one conical toroidal support member (20; 60) attached to the shielding coil (16) and the main magnet assembly (10) is provided, the superconducting magnet assembly further including a cladding layer (41), the cladding layer (41) being coupled to the radially outer surface of the shielding coil (16) and axially protruding beyond the axial ends of the shielding coil, and the radially outer peripheral portion (28) of the material of the conical toroidal support member (20) being attached to the cladding layer (41).

5. The superconducting magnet assembly according to claim 4, wherein, An outer flange (42) is provided in the material of the toroidal support member (20), and the toroidal support member (20) is attached to the shielding coil (16) through the outer flange (42).

6. The superconducting magnet assembly according to claim 5, wherein, The outer flange (42) extends axially and is attached to the cladding layer (41).

7. The superconducting magnet assembly according to any one of claims 1 to 6, wherein, The radially inner peripheral portion (22) of the material of the toroidal support member is attached to the main magnet assembly (10).

8. The superconducting magnet assembly according to claim 7, wherein, An inner flange (26) is provided in the material of the toroidal support member (20), the inner flange (26) axially inwardly pointing from the radially inner peripheral portion (22) of the material of the toroidal support member (20), and the toroidal support member (20) is attached to the main magnet assembly (10) through the inner flange (26).

9. The superconducting magnet assembly according to claim 7, wherein The main magnet assembly (10) includes resin-impregnated coils connected together by intermediate composite spacers, and the radially inner peripheral portion (22) of the material of the toroidal support member is attached to one of the composite spacers.

10. The superconducting magnet assembly according to any one of claims 1 to 6, wherein, The toroidal support member (20) is formed of a stainless steel plate.

11. The superconducting magnet assembly according to any one of claims 1 to 6, wherein, The toroidal support member (20) is formed of a composite material.

12. The superconducting magnet assembly according to any one of claims 1 to 6, wherein, The toroidal support member (20) is formed of a copper plate or an aluminum plate.

13. The superconducting magnet assembly according to any one of claims 1 to 6 further comprises one or more suspension elements attached to the main magnet assembly (10) and the outer vacuum chamber to carry the weights of the main magnet assembly (10), the shield coil (16), and the conical annular support (20).

14. The superconducting magnet assembly according to claim 13, wherein, The one or more suspension elements include leg supports (34).

15. The superconducting magnet assembly according to claim 14, wherein, The leg supports (34) are attached to the main magnet assembly by one or more bolts (24) that attach the annular support (20) to the main magnet assembly.

16. The superconducting magnet assembly according to any one of claims 1 to 6 further comprises an axial rod (36) that extends between annular supports (20) at opposite ends of the main magnet assembly.

17. The superconducting magnet assembly according to claim 16, wherein, The annular supports are circumferentially spaced with flat regions (38) near corresponding outer flanges (32; 42), and the respective axial rods are attached to the respective flat regions.

18. The superconducting magnet assembly according to claim 17, wherein, The flat regions are provided with additional reinforcement.

19. The superconducting magnet assembly according to any one of claims 1 to 6, wherein, The annular support provides support for the main magnet assembly (10) against the outer vacuum chamber.

20. The superconducting magnet assembly according to claim 19, wherein, In the annular support (60), rod bosses (62) are provided, each rod boss (62) including a through hole (68) that receives a support rod (70) extending between the rod boss (62) and a mounting point (72) attached to the inner surface of the outer vacuum chamber.

21. The superconducting magnet assembly according to claim 20 further includes a thermal radiation shield (52), the thermal radiation shield (52) being located between the superconducting magnet and the outer vacuum chamber, wherein, The thermal radiation shield is held and mechanically supported by the support rod (70).

22. The superconducting magnet assembly according to claim 21, wherein, At least one shield support (74) is mounted on the support rod (70), and the shield support is attached to the thermal radiation shield (52) such that the weight of the thermal radiation shield is at least partially borne by the shield support (74).

23. The superconducting magnet assembly according to any one of claims 1 to 6 further comprises an opaque tube (80) that extends between the radially outer ends of the respective annular supports (20; 60) to form a thermal radiation shield for the main magnet assembly (10) and the shield coil (16).

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