JP2009259923A - Superconducting magnet and magnetic device equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconducting magnet which can form a space of a high uniform magnetic field at a position close to the end face of the magnet. <P>SOLUTION: A superconducting magnet 61 comprises a main coil 51 composed of five coil blocks 1-5. The coil blocks 1-5 are arranged asymmetrically in the axial direction Z of the main coil 51 so that a uniform magnetic field A is formed at the end on one side of the main coil 51. The coil blocks 1-5 is composed of four positive magnetic field coil blocks 1-3 and 5 generating a positive magnetic field, and a negative magnetic field coil block 4 generating a negative magnetic field, wherein the negative magnetic field coil block 4 is arranged between two positive magnetic field coil blocks 3 and 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a superconducting magnet and a magnet device including the same. The present invention is suitable as a superconducting magnet and a magnet device used in a medical MRI (Magnetic Resonance Imaging) apparatus.

  Tomographic imaging (MRI imaging) using nuclear magnetic resonance has no problems such as exposure compared to tomographic imaging using X-rays, and is widely used for medical purposes. In the magnet used as the magnetic field generating means of the MRI apparatus, a permanent magnet is used for a low magnetic field, and a superconducting magnet is used for a high magnetic field. On the other hand, in response to the increase in the number of elderly people in recent years, an example in which an MRI apparatus is used for measuring brain functions in dementia diagnosis is increasing. In the MRI apparatus, the higher the generated magnetic field, the higher the signal intensity and the higher the resolution. Therefore, the magnet tends to have a higher magnetic field, and superconducting magnets have become mainstream in recent years. Against this background, various techniques relating to MRI apparatuses have been disclosed. For example, there are the following techniques disclosed in patent documents.

  In Patent Document 1, a static magnetic field magnet formed in a substantially cylindrical shape, a substantially cylindrical gradient magnetic field coil disposed inside the magnet, a shim coil attached to the outer peripheral surface of the gradient magnetic field coil, A tunnel-type MRI apparatus including an RF coil disposed in a through-type hole of a gradient coil is disclosed (see FIG. 1 of Patent Document 1). In a tunnel-type MRI apparatus as described in Patent Document 1, a space where the magnetic field strength is uniform is usually in the center of the magnet. Measurements such as brain function will be performed in the environment. In such a measurement method, mental stress resulting from limited visual field is a burden on the subject. In addition, subjects with claustrophobia may complain about the test.

  Also disclosed is a technique relating to a magnet for an MRI apparatus, in which a coil for generating a reverse magnetic field is arranged at a symmetrical position from the center of the main coil so as to realize a uniform magnetic field space of a certain size in the center of the magnet. (For example, refer to Patent Document 2). In the magnet for the MRI apparatus described in Patent Document 2, the range of the uniform magnetic field space can be expanded to some extent as compared with a magnet that does not use a coil that generates a reverse magnetic field as described above.

JP 2001-212107 A US Pat. No. 5,818,319

  However, the uniform magnetic field space formed by the magnet described in Patent Document 2 is in the center of the magnet, and even if the range of the uniform magnetic field space can be expanded to some extent, it is uniform at a position far from the magnet end. A magnetic field space will be formed. That is, the technique described in Patent Document 2 cannot solve the problem that the mental stress caused by the limited visual field is a burden on the subject. Moreover, since the coil which generate | occur | produces a reverse magnetic field as described in patent document 2 weakens magnetic field intensity, arrangement | positioning of the coil which generates a reverse magnetic field generally prevents realization of high magnetic field. Without realizing a high magnetic field, measurement accuracy such as brain function cannot be improved. Therefore, in order to solve these problems of the MRI apparatus in the measurement of brain function and the like, it is necessary to realize a high magnetic field uniform magnetic field at a position close to the end face of the magnet.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a superconducting magnet capable of forming a uniform magnetic field space of a high magnetic field at a position close to a magnet end surface.

Means and effects for solving the problems

  In order to achieve the above object, the present invention provides a superconducting magnet having a main coil comprising a plurality of coil blocks formed by winding at least a superconducting wire, and forming a uniform magnetic field space at one end of the main coil. As described above, the plurality of coil blocks are arranged asymmetrically along the axial direction of the main coil, and the plurality of coil blocks generate a plurality of positive magnetic field coil blocks that generate a positive magnetic field and a reverse magnetic field. There is provided a superconducting magnet comprising a reverse magnetic field coil block, wherein the reverse magnetic field coil block is disposed between the two positive magnetic field coil blocks at one end portion.

  In order to increase the magnetic field strength, it is necessary to increase the current density flowing in the wire constituting the coil block. However, if this current density is increased, the tension (hoop stress) acting on the wire will increase, and no countermeasures must be taken. The wire cannot withstand this hoop stress. However, according to the above configuration of the present invention, the reverse magnetic field coil block and the positive magnetic field coil block repel each other by arranging the reverse magnetic field coil block between the two positive magnetic field coil blocks. The force received by the constituent wire is directed toward the center of the coil block. Therefore, if it sees as the whole coil block, the force which the wire receives will be mutually canceled and weakened. That is, even if the current density flowing in the wire constituting the coil block is increased, the force applied to the wire as a whole coil block is suppressed by arranging the reversed magnetic field coil block between the two positive magnetic field coil blocks. be able to. Further, by arranging a plurality of coil blocks asymmetrically, a uniform magnetic field space can be formed at a position close to the magnet end face. As a result, a uniform magnetic field space with a high magnetic field can be formed at a position close to the end face of the magnet.

  In the present invention, the coil block is preferably impregnated with epoxy. According to this configuration, the gap between the wire materials constituting the coil block is filled with epoxy, and the wire materials are firmly fixed via the epoxy. In other words, the wire constituting the coil block is less likely to be misaligned. Thereby, quenching generated in the coil block can be suppressed, and it becomes easier to form a uniform magnetic field space of high magnetic field.

  Further, in the present invention, it is preferable that wax is infiltrated into a gap between the coil block impregnated with epoxy and the coil block mounting surface of the winding body.

  According to this structure, the unevenness | corrugation between the coil block attachment surface of a winding frame body and the wire which comprises a coil block reduces. Thereby, quenching generated in the coil block can be further suppressed, and it becomes easier to form a high magnetic field uniform magnetic field space.

  Further, in the present invention, a cylindrical shield coil is further disposed on the radially outer side of the main coil, and an end portion of the main coil on the side where the uniform magnetic field space is formed and the uniform magnetic field space are formed. A step is provided in the axial direction between the end portion of the shield coil and the end portion of the shield coil, the end portion of the shield coil being positioned inside the end portion of the main coil, It is preferable that a supporting structure member for supporting the shield coil is disposed in the stepped portion.

  According to this configuration, in the magnet device provided with the superconducting magnet of the present invention, the uniform magnetic field space can be formed at a position closer to the end surface of the magnet device.

  Furthermore, in the present invention, it is preferable that the reversed magnetic field coil block is arranged as a second coil block from the end of the main coil on the side where the uniform magnetic field space is formed. According to this configuration, since the reversed magnetic field coil block can be disposed at a position closer to the magnet end face, the uniform magnetic field space can be formed at a position closer to the magnet end face.

  According to a second aspect of the present invention, there is provided a magnet device comprising the superconducting magnet of the present invention. According to this magnet device, a uniform magnetic field space with a high magnetic field can be formed at a position close to the end surface of the magnet device.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a coil block arrangement of a main coil 51 constituting a superconducting magnet 61 according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a coil block arrangement of a main coil according to the prior art shown as a comparison.

(Coil block arrangement according to the prior art)
First, the coil block arrangement according to the prior art cited as a comparative example of the present embodiment will be described. As shown in FIG. 5, the main coil according to the conventional technique includes a positive magnetic field coil block 33 formed in a cylindrical shape, two reverse magnetic field coil blocks 32 arranged outside the positive magnetic field coil block 33, and a positive coil coil block 32. It has two positive magnetic field coil blocks 31 arranged outside the magnetic field coil block 33. Here, the positive magnetic field coil block refers to a coil block that generates a positive magnetic field, and the positive magnetic field refers to a magnetic field directed in a predetermined direction. On the other hand, the reverse magnetic field coil block refers to a coil block that generates a reverse magnetic field, and the reverse magnetic field refers to a magnetic field directed in the opposite direction to the magnetic field direction of the positive magnetic field.

  The two reversed magnetic field coil blocks 32 are arranged in the central portion so as to be symmetric with respect to the center of the main coil in the axial direction Z of the main coil. The two positive magnetic field coil blocks 31 are arranged at both ends thereof in the axial direction Z so as to be symmetric with respect to the center of the main coil. The coil blocks 31 to 33 are accommodated in the liquid helium container 7. Each coil block is formed by winding a superconducting wire (not shown) in a solenoid shape.

  The positive magnetic field coil block 33 having a larger number of turns than the coil blocks 31 and 32 (long in the axial direction Z) is for realizing a high magnetic field. The coil blocks 31 and 32 are for expanding the range of the uniform magnetic field space A. The reversed magnetic field coil block 32 contributes to expanding the range of the uniform magnetic field space A, but on the other hand, the magnetic field strength of the uniform magnetic field space A is weakened. Therefore, in order to increase the magnetic field strength in the magnetic field space, it is necessary to increase the number of turns (the number of winding turns) of the positive magnetic field coil block 33 or increase the current density flowing through the wire constituting the coil block. However, when the number of turns of the coil block is increased, the total length of the positive magnetic field coil block 33 becomes longer, and the uniform magnetic field space A is further away from the end face of the main coil. On the other hand, if the current density flowing through the wire is increased, the tension (hoop stress) acting on the wire increases, and the wire cannot withstand the hoop stress. The hoop stress refers to the product (BJR) of the magnetic field strength B, the current density J flowing through the wire, and the winding radius R of the wire. Further, as shown in FIG. 5, in the arrangement method in which the plurality of coil blocks 31 to 33 are arranged symmetrically along the axial direction Z, the uniform magnetic field space A is formed in the magnet central portion, and the magnet end face is formed. It is difficult to form in a close position.

(Coil block arrangement according to this embodiment)
Next, the coil block arrangement according to the present embodiment will be described. As shown in FIG. 1, the main coil 51 constituting the superconducting magnet 61 of this embodiment includes five coil blocks 1 to 5 arranged in series and a cylindrical shape in which the coil blocks 1 to 5 are attached to the outer periphery. It has a winding frame 6. The superconducting magnet 61 includes a main coil 51 and an electric circuit (not shown). The electric circuit is a circuit (protection circuit) for passing a current through the main coil 51 and protecting the main coil 51 from quenching or the like. The winding body 6 is made of a nonmagnetic material such as an aluminum material or a stainless material (the same applies to other embodiments). A plurality of recesses (grooves) to which the coil blocks 1 to 5 are attached are formed on the outer periphery of the reel body 6. Each of the coil blocks 1 to 5 is formed by winding a wire in a ring shape, and the wire is a superconducting wire in which a niobium-titanium (NbTi) alloy-based ultrafine multi-core wire is embedded in a copper base material (other The same applies to the embodiment). The liquid helium container 7 that accommodates the coil blocks 1 to 5 and the winding frame 6 may be separated, or the winding frame 6 may be shared with the liquid helium container 7.

  The five coil blocks 1 to 5 are arranged asymmetrically along the axial direction Z of the main coil 51 so that the uniform magnetic field space A is formed at one end of the main coil 51. In other words, the coil blocks 1 to 5 are arranged so as to be asymmetric with respect to the center of the main coil 51 in the axial direction Z of the main coil 51. The asymmetrical arrangement of the coil blocks will be further described. For example, the number of turns of the coil block 5 attached to one end of the winding body 6 is the same as that of the coil block 1 attached to the other end of the winding body 6. More than the number of turns (the coil block 5 generates a stronger magnetic field than the coil block 1). Further, the coil block 1 and the coil block 5 have different outer diameters and thicknesses. Thus, the coil blocks are arranged such that the arrangement of the coil blocks is asymmetric in the axial direction Z with respect to the center of the main coil 51.

  The coil blocks 1 to 3 and 5 are positive magnetic field coil blocks, and the coil block 4 is a reverse magnetic field coil block. The reverse magnetic field coil block 4 is disposed between the positive magnetic field coil blocks 3 and 5 so as to be sandwiched between the two positive magnetic field coil blocks 3 and 5 at one end of the winding body 6. If described in comparison with the coil block arrangement according to the prior art, the distance between the reverse magnetic field coil block 4 and the positive magnetic field coil blocks 3 and 5 according to the present invention is the reverse magnetic field according to the prior art shown in FIG. The distance between the coil block 32 and the positive magnetic field coil block 31 is shorter. That is, the reverse magnetic field coil block 4 is disposed near the positive magnetic field coil blocks 3 and 5. Further, as will be described in detail later, the reverse magnetic field coil block 4 is disposed at a position where the wire constituting the positive magnetic field coil blocks 3 and 5 receives (is affected by) the reverse magnetic field coil block 4.

  Further, the reverse magnetic field coil block 4 is the second coil from the end of the main coil 51 on the side where the positive magnetic field coil blocks 3 and 5 having more turns than the positive magnetic field coil block 1 (generating a strong magnetic field) are arranged. It is arranged as a block. Compared to the arrangement of the third, fourth,... Coil blocks from the end of the main coil 51, the reversed magnetic field coil block 4 can be arranged at a position closer to the end surface of the main coil 51. Can be formed at a position closer to the magnet end face.

(High BJR design)
By providing the reverse magnetic field coil block 4, the range of the uniform magnetic field space A can be expanded. This contributes to arranging the uniform magnetic field space A at a position close to the magnet end face. The magnetic field strength of the magnetic field space A is weakened. As described above, as a method of increasing the magnetic field strength of the magnetic field space (compensating for a decrease in the magnetic field strength), there is a method of increasing the current density flowing in the wire constituting the coil block. In this method, the method acts on the wire. Tension (hoop stress) becomes large. The wire alone cannot withstand this large stress.

  On the other hand, the BJR (hoop stress) standard adopted in the conventional design was usually 200 MPa or less, and even a high standard was about 300 MPa. There is an established theory that when the stress exceeds this standard, the magnet cannot quench and reach the rated magnetic field during excitation. However, the present inventor has reviewed the arrangement of the coil blocks and arranged the reversed magnetic field coil block 4 between the positive magnetic field coil blocks 3 and 5 so as to be sandwiched between the two positive magnetic field coil blocks 3 and 5. It has been found that even if a high BJR design is adopted, quenching does not occur and a high magnetic field space can be formed. FIG. 2 shows the analysis result as the basis. FIG. 2 is a vector representation of the magnitude and direction of the force received by each wire in each coil block cross section.

  The five coil blocks 11 to 15 shown in FIG. 2 correspond to the coil blocks 1 to 5 shown in FIG. The coil blocks 11 to 13 and 15 are positive magnetic field coil blocks, and the coil block 14 is a reverse magnetic field coil block. The reverse magnetic field coil block 14 is disposed between the positive magnetic field coil blocks 13 and 15 so as to be sandwiched between the two positive magnetic field coil blocks 13 and 15. A reverse magnetic field coil block 16 is disposed outside the positive magnetic field coil block 15. The reversed magnetic field coil block 16 is a coil block constituting a shield coil. In addition, the arrows in the coil blocks 11 to 16 are vector representations of the magnitude and direction of the force received by each wire in each coil block cross section, and the longer this arrow is, the higher the BJR (high hoop stress). Show.

As can be seen from FIG. 2, in each wire constituting the positive magnetic field coil blocks 13, 15, each wire constituting the positive magnetic field coil blocks 13, 15 has a large BJR (hoop stress). By receiving a force from the reverse magnetic field coil block 14 (the reverse magnetic field coil block 14 and the positive magnetic field coil blocks 13 and 15 repel each other), the force acting on each wire moves toward the center of the coil block. When viewed as a whole block, the force is canceled out, and the overall body force acting on the coil block is weakened. For this reason, the displacement as the whole coil block is suppressed, and it becomes unnecessary for the specific wire to have excessive strength. That is, by arranging the reverse magnetic field coil block 14 between the positive magnetic field coil blocks 13 and 15 so as to be sandwiched between the two positive magnetic field coil blocks 13 and 15, the force applied to the wire material as a whole coil block is suppressed. Even if the current density flowing through the wire is increased (even if a high BJR design is adopted), quenching can be prevented. As a result, a uniform magnetic field space with a high magnetic field can be formed at a position close to the end face of the magnet.
The positive magnetic field coil block 15 is further influenced by the reverse magnetic field coil block 16. That is, as described above, each wire constituting the positive magnetic field coil block 15 receives a force from the reverse magnetic field coil block 16 so that the force is counteracted when viewed as a whole coil block and acts on the coil block. The body force is weakened.

(Epoxy impregnation and wax impregnation of coil block)
Next, FIG. 3 is a diagram for explaining the epoxy impregnation and wax impregnation of the coil block. FIG. 3A is a schematic cross-sectional view showing a winding frame 22 in which a coil block 23 impregnated with epoxy and wax is disposed on the outer periphery thereof. FIG. 3B is an enlarged view of a portion C in FIG. 3A, and FIG. 3C is an enlarged view of a portion D in FIG. As shown in FIG. 3, the coil block 23 is preferably impregnated with epoxy and wax.

  As shown in FIG. 3A, the winding frame 22 has a cylindrical member 22b and flanges 22a formed at both ends of the cylindrical member 22b. A coil block 23 is disposed in a groove formed by the flange 22a and the cylindrical member 22b.

  As shown in FIG. 3B, the coil block 23 is filled in a gap between the superconducting wire 24 wound in an annular shape, the glass cloth 25 sandwiched between the layers of the superconducting wire 24, and the superconducting wire 24. And an epoxy resin 27. Further, as shown in FIG. 3C, wax 28 is infiltrated into the gap between the coil block 23 and the side surface 22c (coil block mounting surface 22c) of the flange 22a. More specifically, the mylar sheet 28 is sandwiched in the gap between the coil block 23 and the coil block mounting surface 22c, and the gap between the sandwiched mylar sheet 28 and the coil block 23 and the mylar sheet are included. Wax 28 is infiltrated into the gap between 28 and the coil block mounting surface 22c. Examples of the wax 28 include paraffin wax and beeswax. The mylar sheet 28 is an electrical insulating sheet that insulates electricity. In addition to the Mylar sheet, a sheet made of Teflon (registered trademark) is also included.

  The method of epoxy impregnation and wax impregnation will be described. First, the winding body 22 is wound while the glass cloth 25 is sandwiched between the layers of the superconducting wire 24. Then, the winding frame body 22 around which the superconducting wire 24 is wound is put into a container (not shown), and an epoxy resin 27 is poured into the container, and the gap between the superconducting wires 24 is filled with the epoxy resin 27. In addition, it is preferable to fill the epoxy resin 27 in a vacuum environment so that no gap is formed in the gap between the superconducting wires 24 (in order to satisfactorily fill the epoxy resin 27). Next, the coil block 23 impregnated with epoxy is once peeled off from the winding body 22, and the mylar sheet 28 is sandwiched between the coil block 23 and the coil block mounting surface 22c and reassembled. The reassembled reel 22 is placed in a container (not shown), wax 28 is poured into the container, and the wax 28 is impregnated (penetrated) between the coil block 23 and the coil block mounting surface 22c. The wax 28 impregnation is preferably performed in a vacuum environment as in the epoxy impregnation. In addition, the coil block 23 impregnated with epoxy is once peeled off from the winding body 22 and then reassembled. At least one of the two flanges 22a is fixed to the cylindrical member 22b before reassembly. The

  By impregnating the coil block 23 with epoxy, the gap between the superconducting wires 24 constituting the coil block 23 is filled with the epoxy resin 27, and the wires are firmly fixed via the epoxy resin 27. That is, the superconducting wires 24 constituting the coil block 23 are less likely to be misaligned with each other. Thereby, even if the current density is increased, quenching generated in the coil block 23 can be suppressed, and a high magnetic field uniform magnetic field space can be more easily formed. Further, in the coil block arrangement as shown in FIGS. 1 and 2, the wire constituting the coil block receives the force as shown in FIG. 2, so that the entire coil block is impregnated by impregnating the coil block 23 with epoxy. As a result, the body force can be further reduced.

  In addition, the coil block mounting surface 22c and the coil block 23 are formed by further infiltrating the wax 28 into the gap between the coil block 23 impregnated with epoxy and the coil block mounting surface 22c of the winding body 22. Unevenness between the superconducting wire 24 is reduced. Thereby, the quench which generate | occur | produces in the coil block 23 can be suppressed more.

(Verification of the effects of epoxy impregnation and wax impregnation)
The effect of the epoxy impregnation and wax impregnation of the coil block was verified. The results are described below.

  First, two coil formers (winding frames) were prepared, and winding was performed on each coil former while sandwiching a glass cloth. After that, one magnet (coil former with windings) was vacuum impregnated with epoxy, and the other magnet was vacuum impregnated with wax.

  When energization (excitation test) was performed on the magnet impregnated with wax, the BJR was 248MPa, 283MPa, 270MPa, 263MPa, and the BJR value increased in the second energization. The value showed a tendency to decrease. After the excitation test, the magnet was cut and an attempt was made to observe the cross section. However, the wires were broken apart and did not remain in shape.

  On the other hand, magnets impregnated with epoxy have been proved to withstand high stress more than double that of magnets impregnated with wax only from the first energization such as BJR = 595 MPa, 670 MPa, 735 MPa, 789 MPa, 798 MPa, 813 MPa. The BJR value at the time of quenching also increased after that. After the excitation test, this magnet was cut and cross-sectional observation was performed. As a result, it was found that epoxy was filled with no gap between the wires, and the entire coil block was united to withstand the resultant force.

  In addition, when the epoxy-impregnated magnet was further vacuum-impregnated with wax by the above-described method (wax penetrated into the gap between the coil block and the coil block mounting surface of the coil former) and subjected to an excitation test, BJR = Quench history of 775 MPa and 820 MPa. The reason why the BJR value far exceeding 700 MPa was reached after the first energization was the result of the wax penetrating the interface to erase the unevenness and reducing the friction.

(Magnet device)
FIG. 4 is a schematic cross-sectional view showing a magnet device 54 according to an embodiment of the present invention. As shown in FIG. 4, the magnet device 54 includes a superconducting magnet 62, a liquid helium container 7 in which the main coil 52 and the shield coil 53 of the superconducting magnet 62 are accommodated, and a support structure provided at both ends of the liquid helium container 7. It has a member 21, a radiation shield 8 provided outside the liquid helium container 7, and a heat insulating vacuum container 9 provided outside the radiation shield 8. Liquid helium is placed in the liquid helium container 7. The support structure member 21 is a member for supporting the main coil 52 and the shield coil 53 via the liquid helium container 7.

The superconducting magnet 62 includes a cylindrical main coil 52, a cylindrical shield coil 53 disposed on the radially outer side of the main coil 52, and an electric circuit (not shown). The electric circuit is a circuit (protection circuit) for passing a current through the coils 52 and 53 and protecting the coils 52 and 53 from quenching and the like. The shield coil 53 is a coil for reducing the leakage magnetic field from the magnet device 54.

  The main coil 52 has six coil blocks 41 to 46 arranged in series, and a cylindrical winding body 17 to which the coil blocks 41 to 46 are attached on the outer periphery. The shield coil 53 has two reverse magnetic field coil blocks 47 and 48 arranged in series, and a cylindrical winding body 20 to which the reverse magnetic field coil blocks 47 and 48 are attached to the outer periphery. The six coil blocks 41 to 46 are arranged asymmetrically along the axial direction Z of the main coil 52 so that the uniform magnetic field space A is formed at one end of the main coil 52. The six coil blocks 41 to 46 are all impregnated with epoxy.

  The coil blocks 41 to 44 and 46 are positive magnetic field coil blocks, and the coil block 45 is a reverse magnetic field coil block. The reverse magnetic field coil block 45 is disposed between the positive magnetic field coil blocks 44 and 46 so as to be sandwiched between the two positive magnetic field coil blocks 44 and 46 at one end of the winding body 17. Further, the reverse magnetic field coil block 45 is arranged as a second coil block from the end of the main coil 52.

  Further, a step S in the axial direction Z of the magnet between the end of the main coil 52 on the side where the uniform magnetic field space A is formed and the end of the shield coil 53 on the side where the uniform magnetic field space A is formed. Is provided, and the end of the shield coil 53 is disposed on the inner side (the center side of the magnet) than the end of the main coil 52. And the support structure member 21 is arrange | positioned in this level | step difference S part. In addition, the size of the step S is determined so that the tip protrusion 21a of the support structure member 21 fits in the step S portion. By providing the step S, the end portion of the main coil 52 can be brought close to the end surface of the magnet device 54, so that the uniform magnetic field space A can be formed at a position closer to the end surface of the magnet device 54. In addition, it is a magnet apparatus that the front-end | tip protrusion part 21a of the support structure member 21 is completely settled in the level | step difference S part like this embodiment (it does not protrude outside from the level | step difference S part at all). Although it is preferable to form the uniform magnetic field space A at a position close to the end face 54, this is not always necessary. However, the distance in the axial direction Z between the end of the main coil 52 and the end of the shield coil 53 is preferably at least 4 cm.

  Here, when the magnet device 54 was energized, a uniform magnetic field space A having a magnetic field strength of 3T (Tesla) could be generated at a location near the end face of the magnet device 54. As a result, it is possible to solve the problem in measuring the brain function that the mental stress caused by the limited visual field is a burden on the subject, and to improve the measurement accuracy of the brain function. When the uniform magnetic field space A having a magnetic field strength of 3T (Tesla) is generated near the end face of the magnet device 54, the BJR value of the coil blocks 44 and 46 is about 700 MPa.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

It is a schematic cross section which shows the coil block arrangement | positioning of the main coil which comprises the superconducting magnet which concerns on one Embodiment of this invention. It is the figure which carried out the vector display of the magnitude | size and direction of the force which each wire rod receives in each coil block cross section. It is a figure for demonstrating the epoxy impregnation and wax impregnation of a coil block. It is a schematic cross section which shows the magnet apparatus which concerns on one Embodiment of this invention. It is a schematic cross section which shows coil block arrangement | positioning of the main coil which concerns on a prior art.

Explanation of symbols

1, 2, 3, 5: Positive magnetic field coil block 4: Reverse magnetic field coil block 6: Winding frame (coil former)
7: Liquid helium container 27: Epoxy resin 51, 52: Main coil 53: Shield coil 54: Magnet device 61, 62: Superconducting magnet A: Uniform magnetic field space

Claims (6)

In a superconducting magnet comprising a main coil comprising a plurality of coil blocks formed by winding at least a superconducting wire,
The plurality of coil blocks are arranged asymmetrically along the axial direction of the main coil so that a uniform magnetic field space is formed at one end of the main coil.
The plurality of coil blocks include a plurality of positive magnetic field coil blocks that generate a positive magnetic field and a reverse magnetic field coil block that generates a reverse magnetic field,
The superconducting magnet according to claim 1, wherein the reverse magnetic field coil block is disposed between the two positive magnetic field coil blocks at one end portion. In the superconducting magnet according to claim 1,
A superconducting magnet, wherein the coil block is impregnated with epoxy. The superconducting magnet according to claim 2,
A superconducting magnet, wherein a wax is infiltrated into a gap between the coil block impregnated with epoxy and a coil block mounting surface of a winding frame. In the superconducting magnet according to one of claims 1 to 3,
A cylindrical shield coil disposed on the radially outer side of the main coil;
A step is provided in the axial direction between the end of the main coil on the side where the uniform magnetic field space is formed and the end of the shield coil on the side where the uniform magnetic field space is formed. The end of the shield coil is positioned inside the end of the main coil,
A superconducting magnet, wherein a supporting structure member for supporting the main coil and the shield coil is disposed in the stepped portion. In the superconducting magnet according to one of claims 1 to 4,
The superconducting magnet, wherein the reverse magnetic field coil block is arranged as a second coil block from an end of the main coil on the side where the uniform magnetic field space is formed.   A magnet device comprising the superconducting magnet according to claim 1.

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