WO2018003420A1

WO2018003420A1 - Superconducting magnet device and magnetic resonance tomographic imaging device

Info

Publication number: WO2018003420A1
Application number: PCT/JP2017/020897
Authority: WO
Inventors: 学青木
Original assignee: 株式会社日立製作所
Priority date: 2016-06-30
Filing date: 2017-06-06
Publication date: 2018-01-04
Also published as: JP2018006493A; JP6655487B2

Abstract

This superconducting magnet device (1) comprises at least a superconducting coil (4), a permanent current switch (9) that is connected to the superconducting coil, and a refrigerant-circulating cooling means that cools the superconducting coil and the permanent current switch and that has a channel through which a refrigerant circulates, the device being characterized in that the cooling means at least comprises: a refrigerant container (8) that retains liquefied refrigerant, a refrigerant circulation channel (6) that allows the refrigerant to circulate, and a heat-transfer member (11) that brings the refrigerant circulation channel into thermal contact with the superconducting coil and the permanent current switch; and a stopping means that stops the circulation of the refrigerant flowing through the refrigerant circulation channel in the segment from the refrigerant container to the location of the heat-transfer member that is in contact with the permanent current switch.

Description

Superconducting magnet apparatus and magnetic resonance tomography apparatus

The present invention relates to a superconducting magnet apparatus and a magnetic resonance tomography apparatus.

The superconducting magnet device is composed of a superconducting coil and a permanent current switch installed in parallel thereto, and the above-described permanent current switch is heated to a normal conduction state by generating a resistance (hereinafter referred to as an open state). ), The current is supplied from the exciting power source to the superconducting coil, and then the permanent current switch is cooled to be in the superconducting state (hereinafter referred to as the closed state). This is a permanent current operation in which a current continues to flow in a superconducting closed circuit composed of a permanent current switch with almost no attenuation. As a result, the superconducting magnet device can maintain the magnetic field for a long time.

A conventional superconducting magnet device is a submerged cooling system that is used by immersing it in a refrigerant typified by liquid helium or liquid nitrogen in order to keep the constituent elements typified by the superconducting coil and the permanent current switch in a superconducting state, and Many conductive cooling systems are employed in which a refrigerator and a component are thermally connected with a metal having good thermal conductivity to cool. However, in the above cooling method, when the apparatus is increased in size, a large amount of refrigerant is required in the immersion method, and in the conduction cooling method, the temperature gradient in the object to be cooled becomes large and cannot be maintained at a desired temperature. Therefore, a refrigerant circulation type cooling system has been studied, and a large apparatus represented by a fusion apparatus employs a forced cooling system in which a refrigerant flow path is provided inside the apparatus and forcedly circulated by a pump (for example, a patent). Reference 1). In a medium-sized apparatus typified by a magnetic resonance tomography apparatus (MRI), the refrigerant is flown in the flow path by using buoyancy due to the density difference between the refrigerant vaporized by a heat source such as a superconducting coil and the refrigerant liquefied by a refrigerator. A loop-type thermosiphon system for natural circulation has been proposed (for example, Patent Documents 2 and 3).

The refrigerant circulation type cooling method is expected to shorten the time required to open and close the permanent current switch compared to the conduction cooling method. On the other hand, when the permanent current switch is heated from the closed state to the open state, it is difficult to actively control the circulation of the refrigerant and immediately stop the cooling. It is necessary to continue heater heating with an output exceeding the cooling capacity.

Japanese Patent Laid-Open No. 07-121421 Japanese Patent Application Laid-Open No. 06-342721 International Publication No. 2014/155476

However, the refrigerant vaporized by the heater heating needs to be released to the outside of the apparatus in order to avoid an increase in the pressure of the apparatus, but there is a problem that the amount of discharge increases as in the case of immersion cooling by continuous heater heating. there were. Accordingly, an object of the present invention is to provide a superconducting magnet apparatus and a magnetic resonance tomography apparatus capable of reducing the amount of refrigerant vaporized by heater heating in a superconducting magnet apparatus adopting a refrigerant circulation type cooling system.

The present invention can take various embodiments in order to solve the above-mentioned problems. As an example, “a superconducting coil, a permanent current switch connected to the superconducting coil, the superconducting coil, and the permanent current switch are cooled. And a superconducting magnet device having at least a refrigerant circulation type cooling means for circulating the refrigerant in the flow path, wherein the cooling means stores at least a refrigerant container for storing the liquefied refrigerant, and a refrigerant circulation for circulating the refrigerant. A heat transfer member that thermally contacts the refrigerant circulation flow channel, the superconducting coil, and the permanent current switch, and the heat transfer member that is in contact with the permanent current switch from the refrigerant container. Examples include a superconducting magnet device having stop means for stopping circulation of the refrigerant flowing through the refrigerant circulation passage in the section to the arrangement location.

According to the present invention, it is possible to provide a superconducting magnet apparatus and a magnetic resonance tomography apparatus capable of reducing the amount of refrigerant vaporized by heating a heater in a superconducting magnet apparatus adopting a refrigerant circulation type cooling system.

It is a figure which shows typically the cross section of the superconducting magnet apparatus 1 which concerns on 1st Embodiment. It is a figure which shows typically the superconducting magnet apparatus 1 which concerns on 1st Embodiment as a circuit. FIG. 2 is a bird's eye view of the superconducting magnet device 1 shown in FIG. 1 in which only the refrigerant circulation channel 6 and the refrigerant container 8 are extracted and illustrated. Sectional drawing of the superconducting magnet apparatus 1 which concerns on 2nd Embodiment is shown. FIG. 5 is a bird's-eye view showing only the refrigerant circulation flow path 6 and the refrigerant container 8 with respect to the superconducting magnet device 1 shown in FIG. 4. It is sectional drawing regarding the superconducting coil 4 and the coil bobbin 5 of the superconducting magnet apparatus 1 which concerns on 4th Embodiment. FIG. 7 is a cross-sectional view of the superconducting magnet device 1 shown in FIG. 6 taken along the line AA. FIG. 7 is a BB sectional view of the superconducting magnet device 1 shown in FIG. FIG. 7 is a bird's-eye view showing only the refrigerant circulation flow path 6, the refrigerant container 8, and the permanent current switch 9 of the superconducting magnet device 1 shown in FIG. 6. Sectional drawing of the superconducting magnet apparatus which concerns on 5th Embodiment is shown. 1 is a schematic diagram of a magnetic resonance imaging apparatus.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

(First embodiment)
Hereinafter, a superconducting magnet device 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. FIG. 1 schematically shows a cross section of a superconducting magnet device 1 according to the first embodiment.

The superconducting magnet device 1 includes a vacuum vessel 2, a radiation shield 3 contained in the vacuum vessel 2, a plurality of superconducting coils 4 contained in the radiation shield 3, a coil bobbin 5 to which the superconducting coil 4 is fixed, a refrigerant circulation channel 6, The basic configuration includes a refrigerant 7 contained in the refrigerant circulation channel 6, a refrigerant container 8 storing the refrigerant 7, a permanent current switch 9, and a refrigerator 12 attached to the refrigerant container 8. As the refrigerant 7, for example, liquid helium or liquid nitrogen can be used. Moreover, the shape of the vacuum vessel 2 and the radiation shield 3 shown in FIG. 1 can take any shape as long as the support structure and the constituent members constituting the superconducting magnet device 1 are allowed.

Note that the central axis 21 of the superconducting coil 4 of the present embodiment is oriented in the vertical direction. The central axis 21 is the winding central axis of the superconducting coil 4 and coincides with the direction of the magnetic field generated when the superconducting coil 4 is energized. The refrigerant circulation channel 6 has a structure in which the superconducting coil 4 and the coil bobbin 5 are thermally contacted and cooled via a heat conduction path 11 which is a heat transfer member. Therefore, the heat conduction path 11 is composed of a good conductor having high heat conductivity, and specifically, a copper mesh wire or the like is used. Further, the permanent current switch 9 is also cooled by the refrigerant circulation passage 6 in the same manner as the superconducting coil 4. The refrigerant circulation channel 6 and the heat conduction path 11 mainly constitute the cooling means of this embodiment.

FIG. 2 schematically shows the superconducting magnet device 1 as a circuit. As shown in this figure, the protective resistors 10 are provided in the same number as the number of superconducting coils 4 installed, and each protective resistor 10 is installed in parallel to each superconducting coil 4. A DC power source 13 and a current breaker 14 that are current sources for exciting the superconducting coil 4 are installed outside the vacuum vessel 2. A superconducting coil 4 and a permanent current switch 9 are installed inside the vacuum vessel 2 and are kept below the critical temperature and are in a superconducting state.

In the circuit as shown in FIG. 2, for example, the procedure for generating a permanent current is as follows. First, current is supplied from the DC power supply 13 to the superconducting coil 4 with the permanent current switch 9 opened. Thereafter, with the permanent current switch 9 closed, the supply current from the DC power supply 13 is made zero and the current breaker 14 is opened. As a result, the operation is a permanent current operation in which the current continues to flow in the superconducting closed circuit composed of the superconducting coil 4 and the permanent current switch 9 with almost no attenuation. Thereby, the superconducting magnet apparatus 1 can hold a magnetic field for a long time. When the permanent current switch 9 is opened, it means that the permanent current switch 9 is changed to a normal conduction state and an electric resistance is generated. Moreover, the permanent current switch 9 is closed by shifting the permanent current switch 9 to the superconducting state and setting the electrical resistance to a very low state.

FIG. 3 shows a bird's-eye view of the refrigerant flow path in the superconducting magnet device 1 with respect to the superconducting magnet device 1 shown in FIG. The refrigerant circulation path and the mechanism by which the refrigerant 7 circulates along the path will be described as follows.

The refrigerant circulation channel 6 is connected to the refrigerant circulation part 6d that is in thermal contact with the permanent current switch 9, the refrigerant circulation part 6e that is in thermal contact with the superconducting coil 4, the refrigerant circulation part 6d, and the refrigerant container 8. It is comprised from the part 6c (6a and 6b).

The refrigerant 7 flowing through the

refrigerant circulation parts

6d and 6e has a lower density per unit volume than the refrigerant 7 in the refrigerant container 8 and the refrigerant circulation part 6c. Buoyancy is generated by this density difference, and the refrigerant 7 moves along the refrigerant circulation passage 6 with a force from the bottom to the top in the vertical direction. The reason why the density of the refrigerant 7 flowing through the

refrigerant circulation parts

6d and 6e is reduced is that the refrigerant 7 thermally absorbs heat from these heat sources because it is thermally connected to the permanent current switch 9 and the superconducting coil 4. This is because the volume per unit mass increases. The refrigerant 7 that moves due to buoyancy moves along the refrigerant circulation channel 6, then returns to the refrigerant container 8, is cooled and condensed or cooled by the refrigerator 12, and is supplied to the refrigerant circulation channel 6 again. Reference numeral 20 in the figure indicates the circulation direction of the refrigerant 7 described above.

As described above, since the loop thermosyphon is a refrigerant circulation system that utilizes the density difference of the refrigerant 7 generated in the refrigerant circulation section, there is an advantage that a pump or the like for circulating the refrigerant 7 is unnecessary. Further, since the amount of the refrigerant 7 used is sufficient to create a flow that circulates through the refrigerant container 8 and the refrigerant circulation passage 6, the cooling state is maintained even if the amount of the refrigerant 7 used is small compared to the immersion cooling method. Can be maintained.

However, in the above method, it is difficult to stop the cooling by actively controlling the natural circulation of the refrigerant 7 when the permanent current switch 9 is heated by a heater or the like and is switched to the normal conduction state (when it is opened). is there. This is because even if a part of the permanent current switch 9 is changed to normal conduction by heating of the heater, when the heating of the heater is stopped, the part of the permanent current switch 9 is immediately cooled down by the action of the circulating refrigerant 7 and is in a superconducting state. Will return to. Therefore, it is necessary to continue heating to keep the permanent current switch 9 open. Further, in order to avoid an increase in the internal pressure of the superconducting magnet apparatus 1 due to the refrigerant 7 vaporized by the heater heating, it is necessary to discharge the refrigerant 7 to the outside of the apparatus, and the discharge amount increases as in the case of immersion cooling. It is also considered to use a conduction cooling method in order to avoid an increase in the discharge amount. However, when the permanent current switch 9 is cooled and closed, the cooling time tends to be longer compared to the loop thermosyphon system that can utilize the latent heat or sensible heat of the refrigerant.

Also, even if the cooling means is not a loop thermosyphon type but a forced circulation type, a time lag occurs until the refrigerant circulation stops even if the pump used for circulation stops. Therefore, similarly to the loop thermosiphon type cooling, it is necessary to continue heating the heater for a certain period of time so that the permanent current switch 9 maintains a critical temperature or higher.

Therefore, the superconducting magnet device 1 of the present embodiment discharges or shields the refrigerant 7 flowing through the refrigerant circulation channel 6 in the section from the refrigerant container 8 to the arrangement position of the heat conduction path 11 in contact with the permanent current switch 9. Stop means for stopping the circulation of the refrigerant 7 is provided. A specific concept of this stopping means will be described below. In the following description, the case of adopting the loop thermosiphon type is taken as an example, but the same applies to the forced circulation type.

The superconducting magnet device 1 of the present embodiment has a structure shown in FIGS. 1 and 3 as a stopping means for stopping the circulation of the refrigerant 7. These structures are mainly composed of the refrigerant circulation section 6c, the heater 52 as circulation suppression means, the branch pipe 6f, and the opening / closing means of the branch pipe 6f. Moreover, you may add the refrigerant | coolant storage part 15 to a basic structure.

The refrigerant circulation portion 6 c is a meandering portion that is provided in a part of the refrigerant circulation passage 6 and that is vertically related to the vertical direction. As shown in FIG. 3, it is comprised from the refrigerant | coolant circulation part 6a and the refrigerant | coolant circulation part 6b. The refrigerant circulation unit 6 a is a pipe that is connected to the vicinity of the bottom of the refrigerant container 8 and that extends upward from the vicinity of the bottom of the refrigerant container 8. Moreover, the refrigerant | coolant circulation part 6b is piping which goes below from the upper end part of the refrigerant | coolant circulation part 6a. In the connection structure between the refrigerant circulation unit 6a and the refrigerant circulation unit 6b, the refrigerant storage unit 15 is provided at each end, and the upper end of the refrigerant circulation unit 6a and the upper end of the refrigerant circulation unit 6b are connected to the refrigerant storage unit 15. Structure. Specifically, as illustrated in FIG. 1, the refrigerant storage unit 15 is provided at the upper and lower folding position of the refrigerant circulation unit 6 c. In addition, the refrigerant | coolant storage part 15 may use a container different from piping as the refrigerant | coolant storage part 15, and does not provide another member as the refrigerant | coolant storage part 15, but the edge vicinity of the refrigerant | coolant circulation part 6a and the refrigerant | coolant circulation part 6b. You may form by expanding a diameter and connecting expansion parts.

When the refrigerant storage unit 15 is made of a material different from that of the refrigerant circulation unit, it is desirable that the refrigerant storage unit 15 be made of a material having higher thermal conductivity than the refrigerant circulation unit. The refrigerant reservoir 15 is heated by the heater 51 when the permanent current switch 9 is opened, and the internal refrigerant 7 needs to be quickly evaporated. Therefore, it is desirable to be made of copper or aluminum. In addition, the refrigerant | coolant circulation part 6c and the refrigerant | coolant container 8 which are connected with the refrigerant | coolant storage part 15 are comprised with a material with low heat conductivity, for example, stainless steel. By constituting with a material having low thermal conductivity, even when the refrigerant reservoir 15 is heated, heat transfer to the superconducting coil 4 can be reduced, and the temperature of the superconducting coil 4 can be efficiently maintained with refrigerant saving. it can.

In addition, the refrigerant reservoir 15 is installed in a vertical direction so as to be lower than the liquid level of the refrigerant 7 accommodated in the refrigerant container 8. This is because the refrigerant 7 filled in the refrigerant reservoir 15 rises and flows in the refrigerant circulation unit 6 a against gravity due to the dead weight of the refrigerant 7 accommodated in the refrigerant container 8.

The heater 51 is provided at least in the vicinity of the meandering portion, and prevents the refrigerant 7 from circulating by evaporating the refrigerant 7 flowing through the refrigerant circulation portion 6c. The attachment position of the heater 51 is set to the refrigerant | coolant storage part 15 as shown in FIG. 3, or the refrigerant |

coolant circulation part

6a or 6b. Even if the heaters 51 are provided in the

refrigerant circulation sections

6a and 6b, the bubbles generated by the heating work toward the branch pipe 6f so as to stop the circulation of the refrigerant 7.

The heater 51 operates at the same timing as the heater 52 that heats the permanent current switch 9. Therefore, by sharing the power source and the conductive wire with the heater 52, the heating timing can be easily synchronized, and the structure can be simplified. The heater 51 is a general electric heater, and for example, a nichrome wire heater can be used.

The branch pipe 6 f is a pipe that reaches the outside of the vacuum vessel 2 and that discharges the refrigerant 7 evaporated by the operation of the heater 51. A pressure sensor or a temperature sensor may be attached to the branch pipe 6f as means for detecting the liquid level of the refrigerant 7. Under the permanent current operation, the liquid level position (the liquid level position in the rated state) of the refrigerant 7 is approximately the same between the refrigerant container 8 and the branch pipe 6f. Detecting the liquid level of the refrigerant 7 in the branch pipe 6f has the following advantages.

The superconducting magnet device 1 of this embodiment employs a loop thermosyphon cooling system. For this reason, when bubbles accumulate in the refrigerant circulation channel 6 and the refrigerant reservoir 15, the buoyancy derived from the density difference that is the source of the conveying force of the refrigerant 7 is not efficiently transmitted, and the circulation of the refrigerant 7 stops or the efficiency decreases. There is a possibility that. In particular, the meandering part constituted by the refrigerant circulation part 6c and the refrigerant storage part 15 of the present embodiment has no heat source under a permanent current operation. The refrigerant 7 is conveyed by the pressure generated from the difference between the density of the refrigerant 7 in the refrigerant container 8 and the density of the refrigerant 7 in the refrigerant circulation unit 6d. Therefore, in order to efficiently circulate the refrigerant 7, it is desirable to suppress a decrease in the circulation efficiency of the refrigerant 7 in the meandering portion, and to detect it immediately when a decrease in efficiency occurs. Therefore, a means for detecting the liquid level position of the refrigerant 7 and a means for estimating the storage state of the refrigerant 7 may be provided in the branch pipe 6f.

The temperature sensor, which is one of the concrete means candidates, is installed in the liquid at a position lower than the liquid level position in the rated state, for example, in the rated state, so that the detected temperature of the temperature sensor becomes higher than the rated state. It can be seen that the liquid level is lowered. In addition, the pressure sensor obtains information on the gas pressure in the rated state in advance, and if a higher gas pressure is measured in spite of the rated state, excessive evaporation of the refrigerant 7 occurs. Can be detected. When the refrigerant 7 in the refrigerant reservoir 15 is depleted, the amount of the refrigerant 7 can be returned to an appropriate state by discharging the gas stored from the branch pipe 6f and replenishing the liquefied refrigerant 7. it can.

The means for controlling the opening and closing of the branch pipe 6f is, for example, a valve 61 as shown in FIG. The valve 61 is provided outside the vacuum vessel 2 and may be operated either manually or automatically. When stopping the circulation of the refrigerant 7, the heater 51 is operated to evaporate the refrigerant 7. After the permanent current switch 9 is opened by an operation described later, when the valve 61 is opened, the vaporized refrigerant 7 is discharged to the outside. This discharge can prevent an excessive pressure from being applied to the meandering portion and stop the circulation of the refrigerant 7. Further, as shown in FIG. 1, a configuration may be employed in which a flow path returning from the branch pipe 6f to the refrigerant container 8 is provided and the refrigerant gas generated in the branch pipe 6f is liquefied again and used. By providing the flow path returning to the refrigerant container 8, the consumption amount of the refrigerant 7 can be further reduced.

In the superconducting magnet device 1 of the present embodiment described above, the permanent current switch 9 is opened and closed as follows.

When switching the permanent current switch 9 from the closed state to the open state, the heater 51 is energized with the

valves

61 and 62 closed. The refrigerant 7 circulating through the meandering portion is vaporized by the heater 51. The vaporized refrigerant 7 or the refrigerant 7 whose density has decreased due to the temperature rise obtains buoyancy and stays in the refrigerant reservoir 15. The accumulated refrigerant 7 hinders the circulation of the refrigerant 7 in the meandering portion, and the circulation of the refrigerant 7 toward the permanent current switch 9 is stopped. The heater 52 is energized in conjunction with the energization of the heater 51, the refrigerant 7 in the refrigerant circulation section 6d that is in thermal contact with the permanent current switch 9 vaporizes or rises in temperature, and the resulting buoyancy causes the refrigerant 7 Returns to the refrigerant container 8.

By energizing the heater 52, the permanent current switch 9 and the refrigerant 7 existing in the refrigerant circulation part 6d evaporate, and the liquid level rapidly decreases. In other words, when the liquid level is lower than the permanent current switch 9, in other words, the position where the liquid level of the refrigerant 7 liquefied at the liquid level is in direct or indirect thermal contact with the permanent current switch 9. When it becomes lower than that, the energization to the heater 51 and the heater 52 may be stopped. At such a stop point, the cooling rate of the permanent current switch 9 via the refrigerant circulation portion 6d is lower than the rated state, and the cooling of the permanent current switch 9 by the liquefied refrigerant 7 is suppressed, so the heater This is because the permanent current switch 9 can be kept open without continuing heating by energization.

Note that energization of the heater 52 may be continued even after the liquid level of the refrigerant 7 has sufficiently decreased. By continuing the energization, the temperature of the permanent current switch 9 can also rise quickly and shift to the open state. Further, according to FIG. 1, the part of the permanent current switch 9 and the heated refrigerant circulation portion 6 d are arranged so as to be substantially in the same position in the vertical direction. With such an arrangement relationship, both structures can be heated together by one heater 52, and the configuration is simplified. In addition, when the permanent current switch 9 and the refrigerant circulation part 6d are connected by the heat conduction path 11, and the attachment position of the heat conduction path 11 with respect to each differs in the vertical direction, a heater is provided at each attachment position. Also good.

In the case of the loop thermosyphon system, the thermal connection position of the permanent current switch 9 to the refrigerant circulation part 6d and the installation position of the refrigerant storage part 15 are lower than the liquid level height of the refrigerant container 8 and the liquid level height. It is desirable to be in the vicinity. Under the permanent current operation, the liquid level of the refrigerant container 8, the branch pipe 6f, and the refrigerant circulation part 6d is substantially equal, and exists in the branch pipe 6f and the refrigerant circulation part 6d when the circulation of the refrigerant 7 is stopped. It is necessary to evaporate and remove the refrigerant 7. Therefore, by providing the connection position and the installation position described above at a position close to the liquid level of the refrigerant container 8, the amount of the refrigerant 7 to be evaporated can be reduced, and the liquid level of the refrigerant 7 can be quickly reduced to circulate the refrigerant 7. Can be stopped.

Further, the connecting portion between the branch pipe 6f and the refrigerant container 8 is set to a position higher than the liquid level of the refrigerant 7 in the refrigerant container 8. At this position, it is possible to prevent the refrigerant 7 from flowing back into the branch pipe 6f due to gravity. Further, the branch pipe 6f employs a material having a low thermal conductivity such as stainless steel, thereby suppressing the heat conduction through the branch pipe 6f other than the heating portion, thereby the permanent current switch 9 is cooled and closed. Can be avoided. In order to quickly adjust the liquid level in the refrigerant circulation part 6d, the refrigerant circulation part 6d may be made of two materials. For example, the part where the heater 52 is installed is made of a high heat conductive member such as aluminum, and the other part is made of stainless steel so that they are joined by a dissimilar material joint.

In the above example, the case where a loop-type thermosiphon-type cooling method is employed has been described. When the method of forcibly circulating the refrigerant 7 using a pump or the like is employed, the permanent current switch 9 is shifted from the closed state to the open state according to the same procedure as described above after stopping the pump or the like. When the pump or the like is stopped, the circulation of the refrigerant 7 with respect to the superconducting coil 4 is stopped. Therefore, the cooling of the superconducting coil 4 may be continued using cooling or conduction cooling using heat storage of the solid refrigerant together. Alternatively, a plurality of independent refrigerant containers 8 may be provided, and the circulation of the refrigerant 7 for cooling the superconducting coil 4 and the circulation of the refrigerant 7 for cooling the permanent current switch 9 may be separated.

The case where the permanent current switch 9 is shifted from the closed state to the open state has been described above. When the permanent current switch 9 is cooled to change from the open state to the closed state, the following procedure is executed. First, the valve 61 shown in FIG. 1 is opened, and the low-density refrigerant 7 staying in the refrigerant reservoir 15 is discharged out of the superconducting magnet device 1. A check valve 71 is provided between the discharge side end of the branch pipe 6f and the valve 61 so that the atmosphere does not flow through the branch pipe 6f.

When the internal pressure of the refrigerant reservoir 15 is reduced by the discharge of the refrigerant 7 and the pressure generated by the dead weight of the refrigerant 7 stored in the refrigerant container 8 exceeds the internal pressure, the refrigerant 7 passes from the refrigerant container 8 through the refrigerant circulation unit 6a. It flows into the refrigerant reservoir 15. When the refrigerant reservoir 15 is sufficiently cooled by the refrigerant 7 that has flowed in, the refrigerant circulation unit 6c basically has no heat source, so that the refrigerant 7 maintains the same density as the state stored in the refrigerant container 8. The refrigerant flows into the refrigerant circulation section 6d as it is.

Since the permanent current switch 9 serves as a heat source for the refrigerant circulation section 6d, the density difference of the refrigerant 7 is caused thereby, and the circulation of the refrigerant 7 is resumed. The permanent liquid switch 9 starts to be cooled when the liquid level inside the refrigerant circulation section 6d rises and is held above the position where it is in thermal contact with the permanent current switch 9. Note that when the permanent current switch 9 is kept closed, it is difficult to completely eliminate the influence of radiant heat or the like, although the refrigerant circulation portion 6c basically has no heat source. The refrigerant 7 vaporized by the heat entering the

refrigerant circulation parts

6 a and 6 b without being shielded stays in the refrigerant storage part 15, thereby preventing refrigerant circulation. In order to suppress the occurrence of such a state, it is preferable that the valve 61 is closed and the valve 62 is opened so that the vaporized refrigerant 7 returns to the refrigerant container 8 through the refrigerant circulation portion 6g. Note that the refrigerant circulation unit 6g can be used as a flow path for supplying the refrigerant 7 to the refrigerant container 8 in a preparation stage in which the superconducting magnet device 1 is operated. A check valve 72 is provided in order to prevent atmospheric inflow, similarly to the atmospheric end of the branch pipe 6f.

Further, when forced circulation is adopted as a method of circulating the refrigerant 7, the pump or the like may be restarted after discharging the gaseous refrigerant 7 retained in the refrigerant reservoir 15 as described above.

As described above, the superconducting magnet device 1 of the present embodiment can quickly open and close the permanent current switch 9 by partially stopping the circulation of the refrigerant in the refrigerant circulation type superconducting magnet device. Moreover, since the refrigerant | coolant storage part 15 and the refrigerant | coolant circulation part 6c provided with the meandering part are included and partial circulation stop can be performed by the selective heating of this part, the quantity of the refrigerant | coolant 7 consumed compared with the past Can be made in small quantities. In addition, the heater heating time of the permanent current switch 9 can be reduced as compared with the prior art, and the waiting time for excitation and demagnetization of the superconducting magnet device can be shortened. In particular, in the loop thermosyphon, since it is possible to actively control the refrigerant circulation, it is possible to achieve a remarkable effect that the time required for opening and closing the permanent current switch 9 is equivalent to that of immersion cooling.

(Second Embodiment)
FIG. 4 shows a cross-sectional view of the superconducting magnet device 1 according to the second embodiment. FIG. 5 is a bird's-eye view showing only the refrigerant circulation channel 6 and the refrigerant container 8 taken out. Compared with the first embodiment shown in FIG. 1, the second embodiment further includes a branch pipe 6 f that leads the refrigerant 7 to the outside of the superconducting magnet device 1, and a gas cylinder 81 that is a gas refrigerant introduction unit is provided. The difference is that the vaporized refrigerant 7 can be supplied from the gas cylinder 81 to the refrigerant reservoir 15. The stop means for stopping the circulation of the refrigerant 7 in this embodiment is mainly composed of the refrigerant circulation portion 6c, a gas cylinder 81 which is a circulation suppression means, and a branch pipe 6f. Moreover, you may add the refrigerant | coolant storage part 15 to this. By adopting this structure, a heater for heating the refrigerant reservoir 15 can be omitted, the number of parts housed in the vacuum container 2 is reduced, and the structure is simplified.

In the superconducting magnet device 1 according to the second embodiment, the operation of moving the permanent current switch 9 from the closed state to the open state is performed as follows. First, the valve 61 and the valve 62 are closed, and then the valve 63 is opened. After the valve 63 is opened, the gaseous refrigerant 7 is introduced from the gas cylinder 81 into the branch pipe 6f. The introduced gaseous refrigerant 7 generates a pressure that pushes down the liquid level of the refrigerant 7 below the branch pipe 6f because the valve 61 and the valve 62 are closed. When this pressure is controlled by the introduction amount and the gaseous refrigerant 7 is introduced to the extent that the liquid refrigerant 7 disappears from the refrigerant reservoir 15, the circulation of the refrigerant 7 in the refrigerant circulation unit 6c is stopped. Thereafter, as in the first embodiment, current is supplied to the heater 52, and the refrigerant circulation section 6d is heated, so that the permanent current switch 9 quickly shifts to the open state.

Also, when the permanent current switch 9 is shifted from the open state to the closed state, the following procedure is executed. First, the valve 63 is closed, and then the valve 61 is opened. As a result, the gaseous refrigerant 7 accommodated in the branch pipe 6 f and the refrigerant reservoir 15 is discharged through the valve 61. The discharge of the refrigerant 7 continues until the liquid level in the branch pipe 6f and the liquid level of the refrigerant container 8 become approximately the same. The valve 61 is retightened when the discharge pressure of the refrigerant 7 decreases and the refrigerant 7 is filled with the liquefied refrigerant 7. Thereafter, when the refrigerant circulation unit 6c and the refrigerant storage unit 15 are sufficiently cooled and have the same density as the refrigerant 7 in the refrigerant container 8, the circulation of the refrigerant 7 starts again using the permanent current switch 9 as a heat source.

It should be noted that after the valve 63 is closed, the valve 62 may be open or closed. While the gaseous refrigerant 7 is discharged through the valve 61, it is possible to collect a part of the refrigerant 7 released into the atmosphere and return it to the refrigerant container 8 by maintaining the open state. on the other hand. If the valve 62 is closed, the gaseous refrigerant 7 does not flow into the refrigerant container 8. As a result, since the output of the refrigerator 12 over the period during which the circulation is maintained is not required, the superconducting magnet device 1 can be stably moved even with a small refrigerator.

With the superconducting magnet device 1 according to the second embodiment described above, not only can the same effect as in the first embodiment be obtained, but the time required to stop the circulation of the refrigerant 7 can be reduced by the heating of the refrigerant 7. Since this phase change time is not required, the time is further shortened compared with the first embodiment. Further, since it is not necessary to use heat in order to stop the circulation of the refrigerant 7, the refrigerant circulation part 6c and the refrigerant storage part 15 are all constituted by members having low thermal conductivity, and the amount of heat input from the outside of the vacuum vessel 2 It is possible to design with a focus only on reducing the size, and to ease the design constraints.

(Third embodiment)
FIG. 5 shows a cross-sectional view of the superconducting magnet device 1 according to the third embodiment. Compared with the first embodiment, the third embodiment has a structure in which the refrigerant circulation portion 6d that is in thermal contact with the permanent current switch 9 is extended from 6e that is in thermal contact with the superconducting coil 4. Is different. Although this embodiment has a structure having the heater 51 as in the first embodiment, it may have a system in which the gaseous refrigerant 7 is introduced as in the second embodiment. By adopting a structure in which the refrigerant circulation part 6c and the refrigerant circulation part 6d are branched from the refrigerant circulation part 6e as in the present embodiment, the permanent current switch 9 is arranged in the vicinity of the superconducting coil 4, and the vacuum vessel 2 and the like The entire containment vessel can be made compact.

In the system shown in FIG. 5, when the refrigerant reservoir 15 is heated by the heater 51, the heat is easily transmitted to the refrigerant circulation part 6e through the refrigerant circulation part 6c. Therefore, it is desirable to employ a stainless steel material having a low thermal conductivity for the refrigerant circulation portion 6a to reduce the amount of heat input to the refrigerant circulation portion 6e. Such a configuration reduces the thermal load on the superconducting coil 4 derived from the heat generated by the heater 51 and contributes to temperature stabilization of the superconducting magnet device 1.

(Fourth embodiment)
FIG. 6 is a cross-sectional view of the superconducting magnet device 1 according to the fourth embodiment, and particularly relates to the superconducting coil 4 and the coil bobbin 5. FIG. 7 is a cross-sectional view of the superconducting magnet device 1 shown in FIG. FIG. 8 is a BB cross-sectional view of the superconducting magnet device 1 shown in FIG. FIG. 9 is a bird's eye view in which only the refrigerant circulation flow path 6, the refrigerant container 8, and the permanent current switch 9 of the superconducting magnet apparatus 1 shown in FIG. 6 are taken out.

The fourth embodiment is different from the first embodiment in that the central axis 21 of the superconducting coil 4 is oriented in the horizontal direction and the refrigerant circulation part 6e that is in thermal contact with the superconducting coil 4 is a superconducting coil. 4 and the central axis 21 are different from each other in that they are configured as a plurality of arcuate members. 7 and 8, the superconducting magnet device 1 according to the present embodiment has a circular or elliptical cross section on the inner peripheral surface when a cross section perpendicular to the central axis 21 is obtained. Thus, the vacuum container 2 is configured, and an open space can be formed along the direction of the central axis 21. Moreover, arbitrary shapes are employ | adopted for the outer peripheral surface of the vacuum vessel 2 or the radiation shield 3 according to a utilization form. As shown in FIG. 6, the superconducting magnet device 1 includes a plurality of superconducting coils 4 in the direction of the central axis 21. The diameter of each superconducting coil 4 may be different.

In the superconducting magnet device 1 according to the fourth embodiment, since the central axis 21 of the superconducting coil 4 faces the horizontal direction, the shape of the refrigerant circulation portion 6e is different from those of the first to third embodiments. 8 and 9 show the refrigerant circulation section 6e in the present embodiment. The refrigerant circulation section 6 e is mainly composed of an arc-shaped pipe formed along the outer peripheral curved surface of the superconducting coil 4 and a horizontal pipe for circulating the refrigerant 7 in the direction of the central axis 21. By providing the arc-shaped pipe along the outer peripheral curved surface, the refrigerant 7 flowing through the refrigerant circulating portion 6e is intensively used for cooling the superconducting coil 4, and the cooling efficiency can be improved.

In addition, arrangement | positioning of arc-shaped piping is not restricted to the aspect in alignment with the outer periphery of a superconducting coil. If it is structurally acceptable, it may be configured along the inner peripheral surface. In this case, for example, the superconducting coil 4 is cooled by providing a heat conduction path 11 penetrating the coil bobbin 5. Arc-shaped pipes may be provided at different positions in the direction of the superconducting coil 4 and the central axis 21. For example, an arcuate pipe or a straight pipe may be arranged at the position AA in FIG. Also in this case, the superconducting coil 4 is cooled by providing the heat conduction path 11 so as to penetrate the coil bobbin 5. As described above, the piping structure that does not follow the outer peripheral curved surface is useful for suppressing the internal structure of the vacuum vessel 2 from expanding in the radial direction with respect to the central shaft 21 and miniaturizing the superconducting magnet device 1. is there.

Further, by adopting such a structure, the same effect as that of the first embodiment can be obtained, and a magnetic resonance tomography apparatus (with the central axis 21 oriented in the horizontal direction as shown in FIG. 11A) ( The superconducting magnet apparatus 1 can be applied to a horizontal magnetic resonance imaging apparatus and a horizontal MRI apparatus. FIG. 11A is a schematic diagram of a horizontal MRI apparatus 100.

The MRI apparatus requires a static and strong magnetic field (static magnetic field) for imaging, and a superconducting magnet apparatus is used as a component for generating the static magnetic field. The superconducting magnet device 1 of the present embodiment can be used as a device (static magnetic field generator) that generates this static magnetic field. Since the static magnetic field generator in the conventional MRI apparatus employs an immersion cooling method using liquid helium, the consumption of helium accompanying energization and demagnetization of the superconducting magnet is enormous. On the other hand, in the MRI apparatus 100 to which the superconducting magnet apparatus 1 of the present embodiment is applied, the amount of the refrigerant 7 used is significantly smaller than that of the immersion cooling, and the consumption amount is in principle the volume of the refrigerant reservoir 15. It can also be suppressed.

(Fifth embodiment)
FIG. 10 is a cross-sectional view of the superconducting magnet device 1 according to the fifth embodiment. Compared with the first embodiment, the fifth embodiment is provided with a plurality of refrigerant circulation portions 6 e that are in thermal contact with the superconducting coil 4, and is opened by the vacuum vessel 2 and the radiation shield 3 perpendicular to the central axis 21. The difference is that 22 is formed.

By adopting such a structure, the same effects as those of the first embodiment can be obtained, and a magnetic resonance tomography apparatus (vertical magnetic resonance imaging apparatus, vertical MRI with the central axis 21 oriented in the vertical direction) can be obtained. The superconducting magnet device 1 can be applied to the device. FIG. 11B is a schematic diagram of the vertical MRI apparatus 100. Also in this case, the MRI apparatus 100 to which the superconducting magnet apparatus 1 of the present embodiment is applied requires a remarkably small amount of the refrigerant 7 to be used as compared with the immersion cooling, and the consumption amount is in principle the volume of the refrigerant reservoir 15. It can also be suppressed.

The present invention has been described above by taking a plurality of embodiments as examples. However, the present invention is not limited to these embodiments, and it goes without saying that the structure and material may be changed, added, or deleted without departing from the scope of the invention. In the above-described embodiment, liquid helium is used as the refrigerant 7. However, when the superconducting coil 4 is composed of a high-temperature superconducting wire, liquid nitrogen or the like may be used. A refrigerant circulation type cooling method and a conduction cooling method may be combined. Further, the cooling system of the superconducting magnet apparatus 1 of the present embodiment includes, for example, a superconducting magnet for an accelerator, a superconducting rotating gantry for a particle beam therapy apparatus, a superconducting flyhole, a superconducting bulk body, etc. It can be applied to all devices and members that are required to maintain the superconducting state.

1 Superconducting magnet device (static magnetic field generator)
2 Vacuum container 3 Radiation shield 4 Superconducting coil 5 Coil bobbin 6 Refrigerant circulation channel (cooling means)
6a, 6b, 6c Refrigerant circulation part (meandering part) (stopping means)
6d, 6e, 6g Refrigerant circulation part 6f Branch piping (stopping means)
7 Refrigerant 8 Refrigerant container (cooling means)
9 Permanent current switch 10 Protection resistance 11 Heat conduction path (heat transfer member) (cooling means)
12 Refrigerator 13 DC power supply 14 Current breaker 15 Refrigerant storage part (meandering part) (stop means)
20 Refrigerant circulation direction 21 Central axis 22

Opening

51, 52 Heating heater (heating heater) (circulation suppression means) (stopping means)
61, 62, 63

Valve

71, 72 Check valve 81 Gas cylinder (gas refrigerant introduction means) (circulation suppression means) (stop means)
100 MRI system (magnetic resonance tomography)

Claims

A superconducting coil;
A permanent current switch connected to the superconducting coil;
Refrigerant circulation type cooling means for cooling the superconducting coil and the permanent current switch and circulating a refrigerant through the flow path;
A superconducting magnet device having at least
The cooling means is at least
A refrigerant container for storing the liquefied refrigerant; a refrigerant circulation passage for circulating the refrigerant; a heat transfer member that thermally contacts the refrigerant circulation passage, the superconducting coil, and the permanent current switch;
Have
A superconducting magnet apparatus having stop means for stopping circulation of the refrigerant flowing through the refrigerant circulation passage in a section from the refrigerant container to an arrangement position of the heat transfer member in contact with the permanent current switch.
The superconducting magnet device according to claim 1,
The stopping means is at least
At least one meandering portion that meanders up and down in the vertical direction formed in the refrigerant circulation channel;
A circulation suppression means provided in the meandering portion;
A branch pipe branched from the meandering portion and communicating to the outside of the superconducting magnet device;
A superconducting magnet device having the structure.
The superconducting magnet device according to claim 2,
A heating heater that functions as the circulation suppressing means;
The heating heater is a superconducting magnet device that evaporates the refrigerant flowing through the meandering portion and shields the circulation of the refrigerant.
The superconducting magnet device according to claim 2 or 3, wherein
Gas refrigerant introduction means for introducing the refrigerant in a gas state functioning as the circulation suppression means into the meandering portion;
The superconducting magnet device, wherein the gas refrigerant introduction means introduces the refrigerant in a gas state into the meandering portion and shields circulation of the refrigerant flowing through the meandering portion.
The superconducting magnet device according to claim 4,
The superconducting magnet device, wherein the gas refrigerant introducing means is connected to the branch pipe and connected to the meandering portion.
The superconducting magnet device according to claim 2 or 3, wherein
The refrigerant circulation flow path has a refrigerant storage part at a vertical folding position of the meandering part,
The circulation suppressing means and the branch pipe are superconducting magnet devices provided in the refrigerant reservoir.
The superconducting magnet device according to any one of claims 1 to 3,
A superconducting magnet apparatus, wherein a flow path is provided from the branch pipe to the refrigerant container via the outside of a vacuum container in which the superconducting coil is accommodated.
The superconducting magnet device according to any one of claims 1 to 3,
A superconducting magnet device in which a central axis of the superconducting coil is oriented in a vertical direction.
The superconducting magnet device according to any one of claims 1 to 3,
A superconducting magnet device in which the central axis of the superconducting coil is oriented horizontally.
A magnetic resonance tomography apparatus comprising the superconducting magnet device according to any one of claims 1 to 3 as a static magnetic field generator.