JP2020145371A - Superconducting magnet device, cyclotron, and method for rebooting superconducting magnet device - Google Patents

Abstract

To facilitate reboot of a superconducting magnet device.SOLUTION: A superconducting magnet device 10 comprises: a superconductive coil 12; a cryostat 14 that comprises an ultralow temperature refrigerator 16 cooling the superconductive coil 12 by conduction cooling and houses the superconductive coil 12; an evacuation system 20 evacuating the cryostat 14; a sensor that generates a measurement signal S3 indicating a measurement temperature at a portion cooled by the ultralow temperature refrigerator 16 or a measurement pressure in the cryostat 14; and a control unit 24 that detects deterioration of a temperature rising or a vacuum level in the cryostat 14 on the basis of the measurement signal S3 during an operation stop of the superconductive coil 12, reacts to the deterioration of the temperature rising or the vacuum level in the detected cryostat 14, and outputs a control signal to the evacuation system 20 to evacuate the cryostat 14.SELECTED DRAWING: Figure 1

Description

The present invention relates to a superconducting magnet device, a cyclotron, and a method of restarting a superconducting magnet device.

The superconducting magnet device is mounted on and used in an accelerator such as a cyclotron and various other devices. The superconducting magnet device is cooled to a cryogenic temperature in order to operate, and there are roughly two cooling methods. One is to immerse the superconducting coil in a cryogenic refrigerant such as liquid helium to cool it, and it is also called immersion cooling. In the other method, no cryogenic refrigerant is used. The superconducting coil is directly cooled in a cryogenic refrigerator such as a Gifford-McMahon (GM) refrigerator. This is also called conduction cooling.

Japanese Unexamined Patent Publication No. 6-69030

When the present inventors examined the restart of the superconducting magnet device, they came to recognize the following problems. If the superconducting magnet device stops operating due to some abnormality such as accidental interruption of the exciting power supply, the superconducting magnet device will be restarted if the cause is resolved. Upon restarting the conduction-cooled superconducting magnet device, the superconducting coil is recooled to the target cooling temperature using a cryogenic refrigerator. However, at this time, it may take a considerably long time to recool the superconducting coil, or the superconducting coil cannot be cooled to the target cooling temperature, and the restart of the superconducting magnet device may not be completed. The inventors have found.

One exemplary object of an aspect of the invention is to provide a technique that facilitates the restart of a superconducting magnet device.

According to an aspect of the present invention, the superconducting magnet device includes a superconducting coil, a cryogenic refrigerator for cooling the superconducting coil by conduction cooling, a cryostat accommodating the superconducting coil, and a vacuum for evacuating the cryostat. A sensor that generates a measurement signal indicating the measurement temperature or pressure inside the cryostat of the exhaust system and the part cooled by the cryogenic refrigerator, and the temperature rise inside the cryostat based on the measurement signal while the superconducting coil is stopped. Alternatively, it is provided with a control unit that detects the deterioration of the degree of vacuum and outputs a control signal to the vacuum exhaust system so as to evacuate the cryostat in response to the detected temperature rise in the cryostat or the deterioration of the degree of vacuum.

According to certain aspects of the invention, the cyclotron comprises the superconducting magnet device described above.

According to certain aspects of the invention, a method of restarting a superconducting magnet device is provided. The superconducting magnet device is equipped with a superconducting coil and a cryogenic refrigerator that cools the superconducting coil by conduction cooling, a cryostat that houses the superconducting coil, a vacuum exhaust system that evacuates the cryostat, and a cryogenic refrigerator. The restart method comprises a sensor that generates a measurement signal indicating the measurement temperature or the measurement pressure in the cryostat of the part cooled by the temperature rise in the cryostat based on the measurement signal while the superconducting coil is stopped. Alternatively, it is provided with detecting the deterioration of the degree of vacuum and outputting a control signal to the vacuum exhaust system so as to evacuate the cryostat in response to the detected temperature rise in the cryostat or the deterioration of the degree of vacuum. ..

It should be noted that any combination of the above components or the components and expressions of the present invention that are mutually replaced between methods, devices, systems, and the like are also effective as aspects of the present invention.

According to the present invention, the restart of the superconducting magnet device can be facilitated.

It is schematic cross-sectional view which shows the superconducting magnet apparatus and the cyclotron which concerns on embodiment. It is a flowchart which shows the restart method of the superconducting magnet apparatus which concerns on embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes are designated by the same reference numerals in the description and drawings, and duplicate description will be omitted as appropriate. The scales and shapes of the illustrated parts are set for convenience of explanation and are not interpreted in a limited manner unless otherwise specified. The embodiment is an example and does not limit the scope of the present invention in any way. Not all features and combinations thereof described in the embodiments are necessarily essential to the invention.

FIG. 1 is a schematic cross-sectional view showing a superconducting magnet device and a cyclotron according to an embodiment. The cyclotron 100 is a circular accelerator that accelerates charged particles and outputs a charged particle beam. Examples of charged particles include protons, heavy particles (heavy ions), and electrons. Charged particles are supplied from an ion source (not shown). The cyclotron 100 is used, for example, as an accelerator for charged particle beam therapy.

The cyclotron 100 includes a superconducting magnet device 10, a yoke 102, and a pair of poles 104. The superconducting magnet device 10 includes a superconducting coil 12, a cryostat 14 having a cryogenic refrigerator 16, an exciting power supply device (hereinafter, also simply referred to as a power supply) 18, a vacuum exhaust system 20, a sensor 22, and a control unit. 24 and.

In the following description, an example in which the central axis of the cyclotron 100 (that is, the central axis of the superconducting magnet device 10) C is arranged in a posture extending in the vertical direction (horizontal posture) will be described. Expressions such as "top", "bottom", "left", and "right" are sometimes used to describe the positional relationship between the components, unless the cyclotron 100 is placed in a specific position. It doesn't mean that it doesn't become. The cyclotron 100 may be arranged, for example, in a posture in which the central axis C extends in the horizontal direction (vertical posture).

The superconducting coil 12 has an annular shape and is arranged in the cryostat 14 so that its central axis coincides with the central axis C. The superconducting coil 12 has two air-core coils and a metal coil support frame 13. The two air-core coils are juxtaposed in the direction of the central axis C, and are attached to the coil support frame 13 and integrally supported. The coil support frame 13 includes an upper flange attached to the upper part of the upper air core coil, a central flange sandwiched between the two air core coils, and a lower flange attached to the lower part of the lower air core coil. Has. Further, the superconducting coil 12 is supported by the cryostat 14 by a pair of supports 26. The pair of supports 26 are arranged vertically so as to sandwich the superconducting coil 12, and are attached to the upper flange and the lower flange of the coil support frame 13, respectively.

The cryostat 14 is a vacuum vessel that provides an environment for putting the superconducting coil 12 into a superconducting state. The cryostat 14 has a hollow annular shape, is arranged coaxially with the central axis C, and houses the superconducting coil 12 inside.

The yoke 102 is a hollow disk-shaped block in which a cryostat 14 is arranged. The position of the cryostat 14 in the yoke 102 is maintained by the block body 102a inserted so as to close the hole in which the cryostat 14 is arranged. Further, the pair of poles 104 are arranged at the air core portion of the cryostat 14 (the air core portion of the superconducting coil 12). A pair of dee electrodes (acceleration electrodes) (not shown) are arranged in the space G between the pair of poles 104.

The cryogenic refrigerator 16 is installed in the cryostat 14 and is thermally coupled to the superconducting coil 12 so as to cool the superconducting coil 12 by conduction cooling. For example, the low temperature portion of the cryogenic refrigerator 16 is directly attached to the coil support frame 13 (for example, the lower flange) or connected via an appropriate heat transfer member, and the cryogenic refrigerator 16 is a superconducting coil 12 Cools directly. In the superconducting magnet device 10, a cryogenic refrigerant such as liquid helium is not used for cooling the superconducting coil 12. A plurality of cryogenic refrigerators 16 are typically installed in the cryostat 14, but only one is shown in the figure for simplicity.

The cryogenic refrigerator 16 includes a compressor for working gas (for example, helium gas) (not shown) and an expander also called a cold head, and the compressor and the expander constitute a refrigeration cycle of the cryogenic refrigerator 16. This cools the low temperature part to the desired cryogenic temperature. The cryogenic refrigerator 16 is, for example, a single-stage or two-stage Gifford-McMahon (GM) refrigerator, but is a pulse tube refrigerator, a sterling refrigerator, or other type of cryogenic refrigerator. It may be a refrigerator.

The power supply 18 is connected to the superconducting coil 12 via the current introduction line 19. The current introduction line 19 has a superconducting current lead made of a superconducting material and other conductive members such as copper. The power supply 18 is communicably connected to the control unit 24.

The vacuum exhaust system 20 is configured to evacuate the cryostat 14. The vacuum exhaust system 20 has a vacuum pump 20a, a vacuum valve 20b, and a vacuum gauge 20c, and is connected to the connection port 21 of the cryostat 14. The connection port 21 may have a vacuum valve different from the vacuum valve 20b. During operation of the superconducting magnet device 10, the vacuum valve at the connection port 21 may be closed, thereby maintaining the vacuum inside the cryostat 14.

The vacuum pump 20a is configured to operate according to the pump control signal S1. The vacuum pump 20a is communicably connected to the control unit 24, and the pump control signal S1 is input from the control unit 24 to the vacuum pump 20a. For example, the vacuum pump 20a receives the pump control signal S1 and starts or stops the operation accordingly. That is, the pump control signal S1 may switch the vacuum pump 20a on and off. The vacuum pump 20a may be, for example, a turbo molecular pump, a rotary pump, or any other suitable vacuum pump, or a combination thereof.

The vacuum valve 20b is configured to operate according to the valve control signal S2. The vacuum valve 20b is communicably connected to the control unit 24, and the valve control signal S2 is input from the control unit 24 to the vacuum valve 20b. For example, the vacuum valve 20b may be an on / off valve, which receives the valve control signal S2 and is opened or closed accordingly. Therefore, the vacuum exhaust system 20 can evacuate the cryostat 14 when both the vacuum pump 20a and the vacuum valve 20b are on.

The vacuum gauge 20c is configured to measure the pressure of the vacuum exhaust system 20. The vacuum gauge 20c can be installed in, for example, a vacuum exhaust flow path or a vacuum pipe connecting the vacuum pump 20a to the vacuum valve 20b and can measure the pressure thereof. However, the vacuum gauge 20c may be installed, for example, in the vacuum exhaust flow path or the vacuum pipe connecting the vacuum valve 20b to the connection port 21, or in another place of the vacuum exhaust system 20. Alternatively, the vacuum gauge 20c may be installed inside the cryostat 14 to measure the pressure inside the cryostat 14.

When required, the pressure gauge 20c generates a measurement signal indicating the measurement pressure (for example, the pressure of the vacuum exhaust system 20 or the pressure in the cryostat 14), and outputs the measurement signal to the control unit 24. You may.

The sensor 22 is configured to generate a measurement signal S3 indicating the internal state of the cryostat 14. The sensor 22 is communicably connected to the control unit 24 so as to output the measurement signal S3 to the control unit 24.

As an example, the sensor 22 may be a temperature sensor, and the measurement signal S3 may indicate the measurement temperature of the portion cooled by the cryogenic refrigerator 16. The sensor 22 may be attached to the surface of the superconducting coil 12 or embedded inside the superconducting coil 12. For example, the sensor 22 is attached to the surface of the coil support frame 13.

The location of the sensor 22 may be various as long as it is a portion cooled by the cryogenic refrigerator 16. For example, the sensor 22 may be installed in a low temperature portion of the cryogenic refrigerator 16 or a heat transfer member that connects the low temperature portion to the superconducting coil 12. The sensor 22 may be mounted on the cryostat 14, for example, on the heat shield plate of the cryostat 14 surrounding the superconducting coil 12.

The control unit 24 is configured to receive the measurement signal S3 from the sensor 22 and control the vacuum exhaust system 20 based on the measurement signal S3. The control unit 24 generates a pump control signal S1, a valve control signal S2, or both based on the measurement signal S3, and outputs the control signal to the vacuum exhaust system 20.

The control unit 24 may be configured to monitor the state of the power supply 18. The power supply 18 may generate a power supply status signal S4 and output the power supply status signal S4 to the control unit 24. The power supply status signal S4 may indicate a voltage abnormality of the power supply 18 and / or a cutoff of the power supply 18. Further, the control unit 24 may be configured to control the power supply 18. The power supply 18 causes a current to flow through the superconducting coil 12 in accordance with a command from the control unit 24, whereby the superconducting coil 12 generates a magnetic field.

The control unit 24 may be configured to receive the input signal S5 and control the superconducting magnet device 10 (and the cyclotron 100) based on the input signal S5. The input signal S5 is generated by the user operating an input means such as a mouse or keyboard for receiving an input from the user, and / or is generated by another device communicably connected to the control unit 24. Can be done.

For example, the input signal S5 may be a control signal instructing the restart of the superconducting magnet device 10. When the operation of the superconducting magnet device 10 is stopped due to some abnormality, the input signal S5 may be input to the control unit 24 based on, for example, a user's operation when the cause is resolved. The control unit 24 may start restarting the superconducting magnet device 10 in response to the input signal S5.

Further, the control unit 24 is configured to store data related to the control of the superconducting magnet device 10 (and the cyclotron 100), and may include, for example, a semiconductor memory or other data storage medium.

The control unit 24 is realized by elements and circuits such as a computer CPU and memory as a hardware configuration, and is realized by a computer program or the like as a software configuration, but is appropriately realized by cooperation thereof in the figure. It is drawn as a functional block. It is understood by those skilled in the art that these functional blocks can be realized in various forms by combining hardware and software.

In the superconducting magnet device 10, the superconducting coil 12 in the cryostat 14 in a vacuum state is cooled by the cryogenic refrigerator 16, and a strong magnetic field is formed by passing an electric current through the superconducting coil 12 from the power supply 18. Charged particles are supplied to the cyclotron 100 from an ion source (not shown), and the charged particles are accelerated by the action of a pair of poles 104 and a dee electrode (not shown). As a result, a charged particle beam is output from the cyclotron 100.

By the way, when the superconducting coil 12 stops operating due to some abnormality such as an accidental interruption of the power supply 18, the temperature of the superconducting coil 12 and the cryostat 14 accommodating the superconducting coil 12 may rise. One of the reasons for the temperature rise is that, particularly in the conduction cooling type superconducting magnet device 10, the cryogenic refrigerator 16 also stops operating, and the superconducting coil 12 can lose the cooling source. In addition, at the moment when the power is cut off, the current fluctuates rapidly, and an eddy current is generated in the metal member (for example, the coil support frame 13) inside the superconducting coil 12, and as a result, Joule heat may be generated. This can also raise the temperature of the superconducting coil 12 and the cryostat 14.

Since the cryostat 14 is cooled to an extremely low temperature during the operation of the superconducting coil 12, gas molecules are adsorbed and captured by each part in the cryostat 14. If the temperature of the cryostat 14 rises (for example, to 50 K or more) after the operation of the superconducting coil 12 is stopped, the adsorbed gas molecules may be released and the degree of vacuum in the cryostat 14 may decrease.

Upon restarting the conduction cooling type superconducting magnet device 10, the superconducting coil 12 is recooled using the cryogenic refrigerator 16 to a target cooling temperature at which the operation can be resumed. However, if the degree of vacuum in the cryostat 14 is reduced, the superconducting coil 12 is less likely to be recooled. This is because the decrease in the degree of vacuum reduces the vacuum insulation performance of the cryostat 14, which may increase the heat input inside the cryostat 14 from the surrounding environment. Therefore, it may take a considerably long time to recool the superconducting coil 12. Alternatively, if the heat input from the outside exceeds the refrigerating capacity of the cryogenic refrigerator 16, the superconducting coil 12 cannot be cooled to the target cooling temperature, and the restart of the superconducting magnet device 10 cannot be completed. There is also a possibility.

Therefore, in restarting the superconducting magnet device 10 according to the present embodiment, the control unit 24 restores the vacuum degree of the cryostat 14 based on the internal state of the cryostat 14 while the operation of the superconducting coil 12 is stopped. Controls the vacuum exhaust system 20. For example, the control unit 24 detects a temperature rise or deterioration of the degree of vacuum in the cryostat 14 based on the measurement signal S3 while the operation of the superconducting coil 12 is stopped, and the temperature rise or the degree of vacuum in the detected cryostat 14 is detected. In response to the deterioration, control signals (S1 and S2) are output to the vacuum exhaust system 20 so as to evacuate the cryostat 14.

FIG. 2 is a flowchart showing a method of restarting the superconducting magnet device according to the embodiment. First, in preparation for restarting the superconducting magnet device 10, it is confirmed that the power supply 18 is restored and can operate normally. The control unit 24 may confirm that the power supply 18 can operate normally based on the power supply status signal S4. Further, the cooling of the superconducting coil 12 by the cryogenic refrigerator 16 is restarted. The superconducting coil 12 is still inactive.

As shown in FIG. 2, when the restart process of the superconducting magnet device 10 is started, the temperature inside the cryostat 14 is measured (S10). The sensor 22 measures the temperature of the installation location, generates a measurement signal S3 indicating the measured temperature, and outputs the measurement signal S3 to the control unit 24. The control unit 24 acquires the measurement signal S3.

Next, the control unit 24 compares the measured temperature with the first temperature threshold value T1 based on the measurement signal S3 (S12). The first temperature threshold value T1 is a temperature value set for determining whether or not there is a temperature rise in the cryostat 14. For example, the first temperature threshold T1 is set to a temperature at which the gas molecules adsorbed in the cryostat 14 can be re-emitted (for example, about 50 K) or higher. The first temperature threshold T1 may be selected, for example, from the range of 50K to 60K. In this way, the temperature rise in the cryostat 14 is detected based on the measurement signal S3 while the operation of the superconducting coil 12 is stopped.

When the measured temperature is higher than the first temperature threshold value T1 (Y in S12), the control unit 24 controls the vacuum exhaust system 20 so as to start the vacuum exhaust of the cryostat 14 (S14). The control unit 24 generates a pump control signal S1 that turns on the vacuum pump 20a and outputs the pump control signal S1 to the vacuum pump 20a. Further, the control unit 24 generates a valve control signal S2 that turns on (that is, opens) the vacuum valve 20b, and outputs the valve control signal S2 to the vacuum valve 20b. In this way, the vacuum exhaust system 20 starts the vacuum exhaust of the cryostat 14.

The temperature inside the cryostat 14 is measured again (S16). The control unit 24 compares the measured temperature with the second temperature threshold value T2 based on the measurement signal S3 (S18). The second temperature threshold value T2 is set to a temperature value lower than the first temperature threshold value T1, and may be selected from the range of, for example, 10K to 40K.

When the measured temperature is higher than the second temperature threshold value T2 (N in S18), the vacuum exhaust of the cryostat 14 is continued. That is, both the vacuum pump 20a and the vacuum valve 20b remain on.

The control unit 24 controls the vacuum exhaust system 20 so as to end the vacuum exhaust of the cryostat 14 when the measurement temperature is equal to or lower than the second temperature threshold value T2 (Y in S18) (S20). The control unit 24 generates a pump control signal S1 that turns off the vacuum pump 20a and outputs the pump control signal S1 to the vacuum pump 20a. Further, the control unit 24 generates a valve control signal S2 that turns off (that is, closes) the vacuum valve 20b and outputs the valve control signal S2 to the vacuum valve 20b. In this way, the vacuum exhaust system 20 ends the vacuum exhaust of the cryostat 14.

The first temperature threshold value T1 and the second temperature threshold value T2 are set in advance and stored in the control unit 24. These temperature thresholds can be appropriately set based on the empirical knowledge of the designer or experiments and simulations by the designer.

On the other hand, when the measured temperature is equal to or less than the first temperature threshold value T1 (N in S12), the control unit 24 does not operate the vacuum exhaust system 20. In this case, the temperature rise in the cryostat 14 is not large enough to re-release the gas molecules adsorbed in the cryostat 14. Therefore, it is not necessary to evacuate the cryostat 14.

When the vacuum exhaust of the cryostat 14 is completed, the control unit 24 waits until the superconducting coil 12 and the cryostat 14 are cooled to the target cooling temperature. For example, the superconducting coil 12 is cooled to a target cooling temperature of about 4K to 6K. The control unit 24 confirms that the cooling has been performed to the target cooling temperature based on the measurement signal S3 from the sensor 22, operates the power supply 18 again, and generates a magnetic field in the superconducting coil 12. In this way, the operation of the superconducting magnet device 10 is restarted, and the restart is completed.

As described above, the method of restarting the superconducting magnet device 10 is to detect a temperature rise in the cryostat 14 based on the measurement signal S3 while the operation of the superconducting coil 12 is stopped, and to detect the temperature rise in the cryostat 14. The control signals (S1 and S2) are output to the vacuum exhaust system 20 so as to vacuum exhaust the cryostat 14 in response to the temperature rise of the above.

Therefore, according to the embodiment, when the superconducting coil 12 stops operating due to some abnormality such as an accidental interruption of the power supply 18, even if the temperatures of the superconducting coil 12 and the cryostat 14 rise, the cryostat 14 The vacuum exhaust and the recooling of the superconducting coil 12 can be automatically performed to complete the restart of the superconducting magnet device 10.

For a device such as the cyclotron 100 that can be a source of radiation, an area for prohibiting or restricting the entry of people is defined in the place of installation and the surrounding area, and the superconducting magnet device 10 can be arranged in such an area. In such a case, the operator may not be able to easily access the superconducting magnet device 10 in order to restore the superconducting magnet device 10, and may not be able to manually restart the superconducting magnet device 10.

However, according to the embodiment, since the superconducting magnet device 10 can be automatically restarted, it is easy to restore the superconducting magnet device 10 even if it is installed in the restricted access area. Yes, it's convenient.

The present invention has been described above based on examples. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, various design changes are possible, various modifications are possible, and such modifications are also within the scope of the present invention. By the way. The various features described in relation to one embodiment are also applicable to other embodiments. The new embodiments resulting from the combination have the effects of each of the combined embodiments.

In the above-described embodiment, the sensor 22 is a temperature sensor, but instead, the sensor 22 may be a pressure gauge or a pressure sensor that generates a measurement signal S3 indicating the measurement pressure in the cryostat. The control unit 24 detects the deterioration of the degree of vacuum in the cryostat 14 based on the measurement signal S3 from the sensor 22 while the operation of the superconducting coil 12 is stopped, and responds to the detected deterioration of the degree of vacuum in the cryostat 14. Then, the control signals (S1 and S2) may be output to the vacuum exhaust system 20 so as to evacuate the cryostat 14.

The control unit 24 compares the pressure measured by the sensor 22 with the first pressure threshold value, and controls the vacuum exhaust system 20 so as to start the vacuum exhaust of the cryostat 14 when the measured pressure is higher than the first pressure threshold value. You may. Even if the control unit 24 compares the measured pressure with the second pressure threshold value and controls the vacuum exhaust system 20 so as to terminate the vacuum exhaust of the cryostat 14 when the measured pressure is lower than the second pressure threshold value. Good. The second pressure threshold may be lower than the first pressure threshold.

Although the present invention has been described using specific terms and phrases based on the embodiments, the embodiments show only one aspect of the principles and applications of the present invention, and the embodiments are claimed. Many modifications and arrangement changes are permitted within the range not departing from the idea of the present invention defined in the scope.

10 Superconducting magnet device, 12 Superconducting coil, 14 Cryostat, 16 Cryogenic refrigerator, 20 Vacuum exhaust system, 22 Sensors, 24 Control unit, 100 Cyclotron, S1 Pump control signal, S2 Valve control signal, S3 Measurement signal.

Claims (5)

With superconducting coil
A cryostat that includes a cryogenic refrigerator that cools the superconducting coil by conduction cooling and houses the superconducting coil.
A vacuum exhaust system that evacuates the cryostat and
A sensor that generates a measurement signal indicating the measurement temperature of the part cooled by the cryogenic refrigerator or the measurement pressure in the cryostat.
While the operation of the superconducting coil is stopped, the temperature rise or deterioration of the degree of vacuum in the cryostat is detected based on the measurement signal, and in response to the detected temperature rise or deterioration of the degree of vacuum in the cryostat, the said A superconducting magnet device including a control unit that outputs a control signal to the vacuum exhaust system so as to evacuate a cryostat. The measurement signal indicates the measurement temperature of the portion cooled by the cryogenic refrigerator.
The control unit compares the measured temperature with the first temperature threshold value and controls the vacuum exhaust system so as to start vacuum exhausting of the cryostat when the measured temperature is higher than the first temperature threshold value. The superconducting magnet device according to claim 1, wherein the superconducting magnet device is provided. The control unit compares the measured temperature with the second temperature threshold and controls the vacuum exhaust system so as to terminate the vacuum exhaust of the cryostat when the measured temperature is lower than the second temperature threshold. The superconducting magnet device according to claim 2, wherein the second temperature threshold value is lower than the first temperature threshold value. A cyclotron comprising the superconducting magnet device according to any one of claims 1 to 3. A method of restarting a superconducting magnet device, wherein the superconducting magnet device includes a superconducting coil, a cryogenic refrigerator for cooling the superconducting coil by conduction cooling, and a cryostat accommodating the superconducting coil. A vacuum exhaust system that vacuum exhausts the cryostat, and a sensor that generates a measurement signal indicating the measurement temperature of the portion cooled by the cryogenic refrigerator or the measurement pressure in the cryostat are provided, and the restart is provided. The method is
Detecting a temperature rise or deterioration of the degree of vacuum in the cryostat based on the measurement signal while the operation of the superconducting coil is stopped.
A method comprising: outputting a control signal to the vacuum exhaust system so as to evacuate the cryostat in response to a detected temperature rise or deterioration of the degree of vacuum in the cryostat.

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