JP5307628B2 - Superconducting magnet system - Google Patents

Description

  The present invention relates to a superconducting electromagnet apparatus equipped with a cryogenic refrigerator.

  A superconducting coil as a conventional superconducting magnet is immersed in liquid helium filled in a helium tank as a cryogenic refrigerant tank and kept at a cryogenic temperature, and is arranged so as to surround the helium tank and a helium tank. A GM (Gifford, McMahon) 4K refrigerator that cools the helium tank is attached to the refrigerator attachment port of the vacuum tank, and a heat shield for reducing radiant heat penetration is arranged. A technique of recondensing evaporating helium gas is disclosed (for example, Patent Document 1).

JP 06-069029 A (FIG. 11)

  When a superconducting magnet refrigerator with the above configuration is removed from the vacuum chamber to replace it with an alternative machine for maintenance, helium gas in the helium chamber spouts out, and the helium gas that is ejected freezes in the vicinity of the refrigerator attachment port. Air moisture adheres. If an alternative refrigerator is installed in this state, it causes a mounting failure and prevents good heat connection. Therefore, hot helium gas is blown to remove the frozen air moisture, but heat is transferred to the superconducting coil by the hot helium gas, and the superconducting coil may be quenched (superconducting breakdown). Maintenance is performed by lowering the magnetic field generated by the coil. Therefore, a lot of time is spent on the maintenance, and there is a problem that the maintenance cost is reduced.

  The present invention has been made to solve the above-described problems, and provides a superconducting electromagnet apparatus that does not require lowering the magnetic field of a superconducting coil when replacing a refrigerator.

Superconducting magnet apparatus according to the present invention, the arranged superconducting coil has a central axis, as well as accommodating the superconducting coil, a coolant tank coolant for cooling the superconducting coil is reservoir, the coolant vessel a vacuum chamber enclosing at superconducting magnet apparatus and provided refrigeration installation opening on arranged refrigerator provided in the vacuum chamber, wherein the refrigerator mounting opening projecting axial center of said refrigerant tank And an attachment port front end portion having a gas introduction port, and the attachment port front end portion is provided through the introduction port so that an end surface thereof reaches the refrigerant. When the gas is introduced into the refrigerant tank, the gas diffuses in the refrigerant tank so as not to directly touch the superconducting coil.

Since it is a superconducting electromagnet device configured as described above, when replacing the refrigerator with an alternative machine for maintenance, the superconducting coil can be used even when hot helium gas is removed near the refrigerator attachment port to remove the frozen air moisture. The heat of hot helium gas is not transmitted directly.
Therefore, it is possible to replace the refrigerator even when the superconducting coil is in an excited state, and it is not necessary to lower the magnetic field of the superconducting coil, that is, not to be in an unexcited state. There is an effect that it becomes possible.

1 is a cross-sectional view showing a superconducting electromagnet device according to Embodiment 1. FIG. It is sectional drawing which shows the superconducting electromagnet apparatus of Embodiment 2. 6 is a cross-sectional view showing a superconducting electromagnet device according to Embodiment 3. FIG. It is sectional drawing which shows the superconducting electromagnet apparatus of Embodiment 4.

Embodiment 1 FIG.
Hereinafter, a superconducting electromagnet apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing, for example, a superconducting electromagnet apparatus 100 for MRI placed horizontally. In FIG. 1, a plurality of solenoid-like superconducting coils, that is, four small-diameter superconducting coils 1 and two large-diameter superconducting coils 2 are provided on a central axis 20 so as to be opposed to each other. The superconducting coils 1 and 2 are immersed in liquid helium 4 as a cryogenic refrigerant filled in a helium tank 3 as a cryogenic refrigerant tank and kept at a cryogenic temperature. The vacuum tank 5 is provided so as to surround the helium tank 3, and the vacuum tank 5 and the helium tank 3 are evacuated to insulate them. The heat shield 6 is disposed between the helium tank 3 and the vacuum tank 5 so as to surround the helium tank 3 so as to surround the helium tank 3 and reduce heat intrusion into the helium tank 3.
Note that the output of an excitation power supply (not shown) is supplied to the superconducting coils 1 and 2 via a power lead (not shown). FIG. 1 and FIGS. 2 to 4 to be described later are cross-sectional views of the horizontal type superconducting electromagnet apparatus 100, in which the radial top portion of the large-diameter coil 2 is not immersed in the liquid helium 4 which is a refrigerant This is a state in which the liquid helium 4 in the helium tank 3 is reduced, and about 9/10 of the entire large-diameter coil 2 is immersed in the liquid helium 4 to maintain the superconducting state. Yes.

  At the tip of the refrigerator attachment port 5 a provided in the vacuum chamber 5, there is provided an attachment port tip 5 b that protrudes toward the central axis 20 side of the superconducting electromagnet apparatus 100. The end surface 5c of the mounting port tip 5b reaches the liquid helium 4. Note that the length from the vacuum chamber 5 to the end surface 5c of the attachment port front end portion 5b is such that even if the liquid helium 4 evaporates during operation of the superconducting electromagnet apparatus 100 and the liquid level decreases, the superconducting coils 1 and 2 A length is set such that the end face 5c is in the helium liquid at a liquid level where no quench occurs. The attachment port front end portion 5b has, for example, a cylindrical shape, and hot helium gas for maintenance, which will be described later, passes through the inside of the cylinder and diffuses in the liquid helium 4. Since the end face 5c of the attachment port tip 5b provided in the refrigerator attachment port 5a is always present in the liquid helium 4 as described above, the following work efficiency when replacing the refrigerator 7 is as follows. Will improve.

The superconducting electromagnet apparatus 100 for MRI or the like is regularly maintained, and in particular, the refrigerator 7 is regularly replaced with a serviced substitute machine. The replacement of the superconducting magnet refrigerator shown in the prior art had to be performed after stopping the excitation of the superconducting magnet as described above. However, the excitation of the superconducting coils 1 and 2 of the superconducting electromagnet apparatus 100 according to the first embodiment does not need to be stopped when the refrigerator 7 is replaced. The reason will be explained by the following replacement procedure of the refrigerator 7.
First, the refrigerator 7 shown in FIG. 1 is removed. At this time, liquid helium 4 in the helium tank 3 is ejected, and frozen air moisture adheres to the vicinity of the refrigerator attachment port 5a. The above is the same as in the prior art. In order to remove the frozen air moisture, hot helium gas is blown around the refrigerator attachment port 5a. A part of this hot helium gas passes through the inside of the attachment port front end portion 5b, and from the end surface 5c into the liquid helium 4 Enter and diffuse. Accordingly, the hot helium gas generated by spraying does not directly touch the portion exposed from the helium liquid surface of the large-diameter coil 2, and the heat of the hot helium gas is not transmitted to the large-diameter coil 2, so the risk of quenching of the large-diameter coil 2 is Few. Thereafter, the work is completed by installing the alternative refrigerator 7 at a predetermined position.

As described above, the superconducting electromagnet apparatus 100 according to the first embodiment has a low possibility of quenching even when the superconducting coils 1 and 2 are being excited when the refrigerator 7 is replaced with a maintenance substitute machine. There is no need to stop.
Therefore, it is possible to shorten the work time for replacing the refrigerator and reduce the cost, and thus to save energy. In addition, since it is not necessary to lower the magnetic field, excessive repeated stress is not applied to the superconducting coil, and safe operation is continued.

  In the first embodiment, an example is shown in which a plurality of solenoid-like superconducting coils 1 and 2 are installed opposite to each other in the axial direction. However, the present invention is not limited to this and may be a single superconducting coil. . In addition, it is not necessary to be a solenoidal superconducting coil, and a superconducting coil wound in the axial direction in a racetrack type or a saddle type has a central axis, and a plurality of target superconducting coils are provided. It may be a superconducting electromagnet device such as a beam focusing quadrupole electromagnet of an accelerator.

Embodiment 2. FIG.
Next, the second embodiment will be described with reference to the drawings.
The superconducting electromagnet apparatus 100 according to the second embodiment is provided with a hot helium gas blowing hole 5e near the tip as shown in FIG. 2 in place of the mounting port tip 5b of FIG. 1 of the first embodiment described above. A mounting cap tip 5d is provided, and a reverse cap-shaped wind shield 8 is attached to an end surface 5c of the mounting port tip 5d. Other than this, the second embodiment is the same as the first embodiment. Replacement of the refrigerator 7 in the superconducting electromagnet apparatus 100 having such a configuration follows the same procedure as in the first embodiment. The difference from the first embodiment is that the hot helium gas passing through the inside of the attachment port front end portion 5d is diffused by the reverse cap-shaped wind shield 8 after being blown out from the blowing hole 5e, and does not directly touch the large-diameter coil 2. Therefore, even if the refrigerator is replaced without lowering the magnetic field of the superconducting coils 1 and 2, the risk of quenching of the superconducting coil 2 is small, so that maintenance time and maintenance costs can be reduced.
In the second embodiment, an example in which a plurality of superconducting coils are arranged in the axial direction is shown. However, the number of superconducting coils is not limited to a solenoid shape.

Embodiment 3 FIG.
In the superconducting electromagnet apparatus 100 according to the third embodiment, instead of the mounting port front end portion 5b according to the first embodiment described above, a mounting port front end portion 5f that protrudes toward the inner diameter side as shown in FIG. The large-diameter superconducting coil 2 is hotly protruded from the frame plate 3a between a plurality of small-diameter solenoid-like superconducting coils 1 provided at the inner diameter portion of the helium tank 3 and opposed to each other. A shielding wall 3b provided to shield from helium gas and a wind shielding plate 3c connecting the shielding wall 3b are provided. The end face 5c of the attachment port front end portion 5f and the wind shielding plate 3c have a gap G serving as a space for blowing out hot helium gas. The superconducting coils 1 and 2 of the third embodiment are in the form of solenoids. When replacing the refrigerator 7 of the superconducting electromagnet apparatus 100 having such a configuration, the sprayed hot helium gas is heat-exchanged by the wind shielding plate 3c and directly touches the large-diameter coil 2 by the shielding wall 3b. Therefore, it is not necessary to lower the magnetic field of the superconducting coils 1 and 2, and the maintenance time and cost can be reduced.

Embodiment 4 FIG.
As shown in FIG. 4, the superconducting electromagnet apparatus 100 according to the fourth embodiment is different from the above-described third embodiment in that the windshield 3c projects from the windshield plate 3c and faces the windshield 3c. A plate fin 3d and a plurality of outer diameter fins 3e that protrude in the inner diameter direction from the outer diameter portion of the helium tank 3 and are provided in addition to each other are provided, and the outer diameter fins 3e and the wind shielding plate fins 3d are provided. Are alternately arranged in the axial direction, and the rest is the same as in the third embodiment. In the superconducting electromagnet apparatus 100 having such a configuration, the hot helium gas blown when the refrigerator 7 is exchanged passes between the wind shielding plate fins 3d and the outer diameter fins 3e and performs heat exchange. There is no direct contact with the large-diameter superconducting coil 2.
Therefore, in the fourth embodiment, similarly to the first to third embodiments, it is not necessary to lower the magnetic field of the superconducting coils 1 and 2 when replacing the refrigerator.

  In addition, the heat shielding conductors, such as copper and aluminum, are used for the material of the shielding wall 3b, the wind shielding plate 3c, the wind shielding plate fin 3d, and the outer diameter fin 3e shown in the third and fourth embodiments.

  The present invention can be used for a superconducting electromagnet apparatus for MRI and a superconducting electromagnet apparatus for magnetic levitation and high energy acceleration.

1 Small-diameter superconducting coil, 2 Large-diameter superconducting coil, 3 Helium tank, 3a Frame plate,
3b shielding wall, 3c wind shielding plate, 3d wind shielding plate fin, 3e outer diameter fin, 5 vacuum chamber,
5a Refrigerator mounting port, 5b Mounting port tip, 5c End surface, 5d Mounting port tip,
5e blowout hole, 7 refrigerator, 8 wind shield, 20 central axis,
100 Superconducting electromagnet device.

Claims (7)

The central axis superconducting coils arranged with a said with housing the superconducting coil, the refrigerant tank in which the refrigerant is liquid storage of the superconducting coil is cooled, the vacuum chamber surrounding said refrigerant tank, said vacuum tank a superconducting magnet apparatus and refrigerator attachment opening to arranged refrigerator provided is provided on the the refrigerator mounting opening and projects axially center of the refrigerant tank, the mounting hole having a inlet gas When the gas is introduced into the refrigerant tank through the introduction port , the tip end portion of the attachment port is provided so that the end surface thereof reaches the refrigerant. Further, the superconducting electromagnet apparatus is provided so that the gas diffuses in the refrigerant tank and does not directly touch the superconducting coil. 2. The superconducting electromagnet apparatus according to claim 1, wherein a gas blowing hole is provided in the vicinity of the tip of the attachment port tip, and a reverse cap-shaped wind shield is provided on the end surface. 3. The superconducting electromagnet apparatus according to claim 1, wherein the superconducting coil is a solenoidal superconducting coil. The solenoid-shaped superconducting coil is provided with a plurality of small-diameter and large-diameter superconducting coils opposed in the axial direction, and protrudes from the frame plate of the inner diameter portion of the refrigerant tank in the outer diameter direction. a shielding wall provided so as to shield one another the large diameter superconducting coils Te, wherein with the Futei barrier attached to the shielding walls are provided, the attachment port tip shielding said its end face Futei The superconducting electromagnet apparatus according to claim 3 , wherein the superconducting magnet apparatus is provided with a gap. The solenoid-shaped superconducting coil is a plurality of small-diameter and large-diameter superconducting coils provided in a plurality of axial directions, and a plurality of superconducting coils protruding in the inner diameter direction from the outer diameter portion of the refrigerant tank. an outer diameter fin, and the projecting from the frame plate of the inner diameter portion of the refrigerant tank in the outer diameter direction, relative to shield wall the provided large diameter superconducting coils to shield one another, attached to the shield walls The wind shield plate is provided with a plurality of wind shield fins provided to protrude in the outer diameter direction, and the outer diameter fins and the wind shield fins are alternately arranged in the axial direction. The superconducting electromagnet apparatus according to claim 3 , wherein an end surface of the attachment port front end portion is provided with a gap from the wind shielding plate. The superconducting electromagnet apparatus according to claim 4 , wherein a material of the shielding wall and the wind shield is copper or aluminum. The superconducting electromagnet apparatus according to claim 5 , wherein the shielding wall, the wind shield, the outer diameter fin, and the wind shield fin are made of copper or aluminum.

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