JP2000012326A - Conduction cooling type superconducting magnet system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a stable superconducting magnet by varying a cooling capability of a refrigerator with minimum electric power, and obtain energy saving effect by controlling power consumption of a compressor. SOLUTION: A conduction cooling type superconducting magnet system cooling a super conducting coil 2 by conducting cooling refrigerant gas from a refrigerator 5 to the super conducting coil 2 contained in a vacuum chamber 1 comprises a compressor 3 providing compressed refrigerant gas to the refrigerator 5, an inverter 16 varying operating frequency of the compressor 3, a temperature sensor 12 sensing temperature of the superconducting coil 2, and a controller 14 controlling output frequency of the inverter 16 based on the temperature detection signal sensed by the temperature sensor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting electromagnet system for conducting cold heat obtained from a refrigerator to a superconducting coil for cooling.

[0002]

2. Description of the Related Art Conventionally, as this type of superconducting electromagnet system, there is one having a configuration as shown in FIG. In this superconducting electromagnet system, a superconducting coil 2 for forming a superconducting magnet is housed in a vacuum vessel 1 as shown in FIG. 5, and the superconducting coil 2 supplies He gas compressed by a compressor 3 through a He gas hose 4. Cold heat is transmitted from the Gifford McMahon type refrigerator 5 through the second cooling stage 5b and the first cooling stage 5a, and is cooled to a superconducting state.

[0003] That is, the superconducting coil 2 is thermally connected to the first cooling stage 5a of the refrigerator 5, which is a thermally low-temperature end, by the heat connecting portion 6a made of a material having good heat conductivity and electrically insulated. The first cooling stage 5a is connected to a second cooling stage 6b which is a high-temperature end.

[0004] The superconducting coil 2 is made of a current lead 7, 8a,
8b and a high-temperature superconducting lead 9, and further electrically connected to a magnet power supply 11 through a power cable 10 at room temperature.

In this case, the current leads in the vacuum vessel 1 are electrically insulated from the first cooling stage 5a, which is a low-temperature end of the refrigerator 5, and the second cooling stage 5b, which is a high-temperature end. Thermal connection portions 12b and 12a made of a material having good heat conductivity.

In the conventional apparatus having such a configuration, the superconducting coil 2 is brought into direct contact with the first cooling stage 5a of the refrigerator 5 to be cooled to an extremely low temperature to be in a superconducting state, or disclosed in JP-A-6-132568. As shown in FIG. 2, liquid nitrogen is introduced into the outer surface of the superconducting coil 2 so that heat can be exchanged between the superconducting coil 2 and the superconducting coil 2.

[0007]

However, in the case of a system in which a superconducting coil is brought into direct contact with a cooling stage of a refrigerator as in a conventional apparatus, it takes a long time to cool the superconducting coil from room temperature to extremely low temperature. There's a problem.

For example, when a refrigerator 5 having a first cooling stage 5a and a second cooling stage 5b having a lower temperature than the first cooling stage 5a is used as the cooling stage, the first stage having a small heat load is used. The temperature of the cooling stage 5a drops first and reaches a predetermined temperature (50K to 77K). On the other hand, superconducting coil 2 having a large heat capacity and second cooling stage 5b thermally connected to superconducting coil 2
Is cooled by heat conduction, it takes a long time to reach a temperature at which a predetermined superconducting state is reached.

The method disclosed in Japanese Patent Application Laid-Open No. Hei 6-132568 requires a piping for liquid nitrogen and the like, so that the cost is high, and since liquid nitrogen is used, a superconducting magnet which does not use a refrigerant is used. The advantage of the simplicity is impaired.

On the other hand, when a current is supplied to the superconducting coil to make it function as a superconducting magnet, if the excitation speed is increased, heat is generated due to eddy current or the like, and the temperature of the superconducting coil rises. There is a problem that quenching to transfer to occurs. Therefore, the usual method of use is to reduce the speed of the magnetic field excitation, which lowers the efficiency.

In order to prevent the influence of the temperature rise, the cooling capacity of the refrigerator is increased. However, in order to increase the cooling capacity, the power consumption of the compressor of the refrigerator must be increased. There is a problem of increasing costs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can realize a stable superconducting magnet with minimum power, and can control the power consumption of a compressor to obtain an energy saving effect. It is intended to provide a superconducting magnet system of the type.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a conduction cooling type superconducting magnet system by the following means. According to a first aspect of the present invention, there is provided a conduction cooling type superconducting magnet system for cooling a superconducting coil by transmitting cold heat from a refrigerator to a superconducting coil housed in a vacuum vessel. , An inverter for varying the operating frequency of the compressor, and control means for controlling the output frequency of the inverter to vary the refrigerating capacity of the refrigerator.

In the conduction cooling type superconducting magnet system according to the first aspect of the present invention, since the refrigerating capacity of the refrigerator can be varied, the cooling time can be shortened by operating at the maximum refrigerating capacity during the initial cooling. In addition, since it becomes possible to switch to the minimum necessary refrigeration capacity when the temperature reaches a predetermined temperature, the power consumption of the compressor of the refrigerator can be saved.

According to a second aspect of the present invention, there is provided a conduction cooling type superconducting magnet system for cooling a superconducting coil by transmitting cold heat from the refrigerator to a superconducting coil housed in a vacuum vessel. A compressor for supplying a refrigerant gas, an inverter for varying the operating frequency of the compressor, a temperature sensor for detecting the temperature of the superconducting coil, and an output frequency of the inverter based on a temperature detection signal detected by the temperature sensor. And control means for controlling the

In the conduction cooling type superconducting magnet system according to the second aspect of the present invention, the temperature of the superconducting coil detected by the temperature sensor is monitored, and the temperature of the superconducting coil is monitored by the control means, whereby the refrigeration is performed. The superconducting magnet can be used safely even when the machine is not operating. Further, since the refrigerating capacity of the refrigerator can be adjusted according to heat intrusion into the superconducting coil, the superconducting coil can be stably maintained for a long time.

According to a third aspect of the present invention, there is provided a conduction cooling type superconducting magnet system according to the second aspect of the present invention,
The control means outputs a frequency determined based on a relationship between a predetermined refrigerating capacity of the refrigerator and an operating frequency of the compressor.

In the conduction cooling type superconducting magnet system according to the second and third aspects of the present invention, the temperature of the superconducting coil detected by the temperature sensor is monitored, and the temperature of the superconducting coil is monitored by the control means. By doing so, the superconducting magnet can be used safely even when the operation of the refrigerator is stopped. Further, since the refrigerating capacity of the refrigerator can be adjusted according to heat intrusion into the superconducting coil, the superconducting coil can be stably maintained for a long time. Further, it is possible to freely set and control the operation mode for reducing the power consumption of the compressor.

According to a fourth aspect of the present invention, in the conduction-cooled superconducting magnet system according to the first or second aspect, the control means responds to a temperature of the superconducting coil detected by the temperature sensor. To control the output of a magnet power supply for exciting the superconducting coil.

According to a fourth aspect of the present invention, there is provided a conduction cooling type superconducting magnet system according to the present invention.
In addition to the functions and effects of the invention corresponding to the above, the inverter has a function to control the output of the magnet power supply and an inverter that makes the refrigerating capacity of the refrigerator variable, so that the speed of the excitation and demagnetization of the magnetic field is limited within a range where the superconducting coil does not quench. Adjustment can be freely performed.

According to a fifth aspect of the present invention, in the conduction-cooled superconducting magnet system according to the first or second aspect of the present invention, the temperature sensors are respectively provided at a plurality of different positions of the superconducting coil. .

According to a fifth aspect of the present invention, there is provided a conduction-cooled superconducting magnet system according to the present invention.
In addition to the functions and effects of the invention corresponding to (1), since the temperature distribution of the superconducting coil can be grasped, it is possible to accurately measure the temperature rise of the superconducting coil.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a first embodiment of a superconducting magnet system according to the present invention, and the same parts as those in FIG.

In FIG. 1, a superconducting coil 2 for forming a superconducting magnet is accommodated in a vacuum vessel 1, and the superconducting coil 2 is a Gifford McMahon type in which He gas compressed by a compressor 3 is supplied through a He gas hose 4. From the refrigerator 5 of the second stage cooling stage 5b,
Cold heat is conducted through the first cooling stage 5a and is cooled to a superconducting state.

The superconducting coil 2 is thermally connected to a first cooling stage 5a of the refrigerator 5 which is a thermally low-temperature end by a heat connecting portion 6 made of a material having good heat conductivity and electrically insulated. This first stage cooling stage 5a is a second stage at a high temperature end.
It is connected to the stage cooling stage 5b.

The superconducting coil 2 is composed of current leads 7, 8a,
8b and a high-temperature superconducting lead 9, and further electrically connected to a magnet power supply 11 through a power cable 10 at room temperature.

In this case, the current leads in the vacuum vessel 1 are thermally insulated from the first cooling stage 5a at the low temperature end of the refrigerator 5 and the second cooling stage 5b at the high temperature end. Thermal connection portions 6a and 6b made of a material having good heat conductivity.

A temperature sensor 12 (for example, a carbon resistor or a thermocouple) for measuring the temperature of the coil is attached to the superconducting coil 2 via an electrically insulated spacer having good heat conductivity. . This temperature sensor 12 is connected to a controller 14 via a measuring cable 13. Although this measuring cable 13 is not shown in the figure,
It is led out from the inside of the vacuum vessel 1 to the outside through the field through.

The controller 14 controls the control cable 1
5 and connected to the magnet power supply 11 via the control cable 17.
The inverter 16 is connected to the compressor 13 of the refrigerator 5 so that the refrigerating capacity of the refrigerator 5 can be changed by changing the operation cycle of the compressor 13.

The controller 14 has a function of outputting a frequency determined based on a relationship between a predetermined refrigerating capacity of the refrigerator 5 and an operating frequency of the compressor 3, and an output of the magnet power supply 11 for exciting the superconducting coil 2. Control function.

Here, FIG. 2 shows He compressed in the refrigerator 5.
FIG. 3 shows the relationship between the compressor 3 supplying gas and power consumption, and FIG. 3 shows the relationship between the operation cycle of the compressor 3 and the refrigerating capacity of the refrigerator 5.

As is apparent from FIGS. 2 and 3, when the operating frequency of the compressor 3 is increased, the power consumption is increased, and as shown in FIG. 3, the refrigerating capacity of the refrigerator 5 is increased.

Next, the operation of the superconducting magnet system configured as described above will be described. Now, superconducting coil 2
When the amount of heat penetrating into the superconducting coil 2 increases, the temperature of superconducting coil 2 increases. At this time, the temperature of superconducting coil 2 is detected by temperature sensor 12, and the detection signal
4 is input.

When the temperature detection signal of superconducting coil 2 is higher than a preset temperature, inverter 16 outputs a higher frequency to compressor 3 under the control of controller 14. As a result, the operating frequency of the compressor 3 also increases, and the refrigerating capacity of the refrigerator 5 increases, so that the temperature of the superconducting coil 2 is reduced by the first cooling stage 5a.

Such a cycle is continued until the temperature of the superconducting coil 2 reaches a predetermined temperature, and when the temperature is stabilized at a constant temperature, the operating frequency of the compressor 3 is maintained at the optimum operating frequency.

On the other hand, when a current flows through the superconducting coil 2 due to the operation of the magnet power supply 11, heat penetration from the room temperature part increases, and an AC loss occurs due to a time-varying current, so that the superconducting coil 5 generates heat. I do. The temperature of superconducting coil 2 rises due to these heats. The temperature of superconducting coil 2 at this time is detected by temperature sensor 12, and the detection signal is input to controller 14. Then, the controller 14 controls the output of the magnet power supply 11 based on the detection signal from the temperature sensor 12. Therefore, energization control is performed such that the temperature of superconducting coil 2 becomes equal to or lower than a predetermined temperature. At this time, the operation frequency of the compressor 3 is simultaneously controlled by the inverter 16 as described above.

Next, an operation mode for reducing the power consumption of the compressor 3 will be described. Now, refrigerator 5
When the compressor 3 is operated at the maximum refrigerating capacity, the temperature of the superconducting coil 2 drops to an unnecessary temperature.
Essentially, the superconducting coil 2 only needs to be at a temperature specified in advance below the superconducting transition temperature Tc of the wire.

Therefore, maintaining the superconducting coil 2 in a predetermined temperature range by lowering the refrigerating capacity of the refrigerator 5 can reduce the power consumption of the compressor 3. Therefore, by detecting the temperature of the superconducting coil 2 by the temperature sensor 12 and controlling the inverter 16 by the controller 14,
The output frequency of the inverter 16 can be minimized.

As described above, in the first embodiment, the operation of the refrigerator 5 is stopped by monitoring the temperature of the superconducting coil 2 detected by the temperature sensor 12 and monitoring the temperature of the superconducting coil 2 by the controller 14. Even at times, the superconducting magnet can be used with confidence. Also,
Since the refrigerating capacity of the refrigerator 5 can be adjusted according to heat intrusion into the superconducting coil 2, the superconducting coil 2 can be stably maintained for a long time. Furthermore, the controller 14 can freely set and control the operation mode for reducing the power consumption of the compressor 3.

Further, the controller 14 includes an inverter 16 for changing the refrigerating capacity of the refrigerator 5 and the magnet power supply 1.
Since it has a function of controlling the output of No. 1, the speed of exciting and demagnetizing the magnetic field can be freely adjusted within a range where the superconducting coil does not quench.

FIG. 4 shows the configuration of a second embodiment of the superconducting magnet system according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. State.

In the second embodiment, as shown in FIG. 4, the temperature of the superconducting coil 2 is detected by a plurality of, here two, temperature sensors 12a and 12b, and the detection signals are input to the controller 14, respectively. If any of the detection signals exceeds the temperature of the superconducting coil 2 which is specified in advance, the inverter 16 is turned off in the same manner as in the first embodiment.
, The operating frequency of the compressor 3 and the excitation speed of the magnet power supply 11 are controlled.

With such a configuration, the superconducting coil 2
, The temperature rise of the superconducting coil 2 can be accurately measured. The configurations described in the first and second embodiments are examples of the present invention, and can be similarly applied to a superconducting magnet system having another configuration. Further, although the present invention makes the most of the features of the low-temperature superconducting magnet, it is needless to say that the present invention can be sufficiently applied to a high-temperature superconducting magnet.

[0044]

As described above, according to the present invention, since the refrigerating capacity of the refrigerator is made variable, a stable superconducting magnet can be realized with minimum power, and the power consumption of the compressor can be adjusted. And a superconducting magnet system capable of providing an energy saving effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a superconducting magnet system according to the present invention.

FIG. 2 is a diagram showing a relationship between an operating frequency of a compressor and power consumption in the embodiment.

FIG. 3 is a diagram showing the relationship between the operating frequency of the compressor and the refrigerating capacity of the refrigerator in the embodiment.

FIG. 4 is a configuration diagram showing a first embodiment of a superconducting magnet system according to the present invention.

FIG. 5 is a configuration diagram showing an example of a conventional superconducting magnet system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2 ... Superconducting coil 3 ... Compressor 5 ... Refrigerator 5a ... 1st cooling stage 5b ... 2nd cooling stage 6, 6a, 6b ... Thermal connection part 7, 8a, 8b ... current lead 9 ... high-temperature superconducting lead 10 ... power cable 11 ... magnet power supply 12, 12a, 12b ... temperature sensor 14 ... controller 16 ... inverter.

Claims (5)

[Claims] 1. A conduction cooling type superconducting magnet system for cooling a superconducting coil by transmitting cold from a refrigerator to a superconducting coil housed in a vacuum vessel, wherein the compressor supplies compressed refrigerant gas to the refrigerator. And an inverter for varying the operating frequency of the compressor, and control means for controlling the output frequency of the inverter to vary the refrigerating capacity of the refrigerator. 2. A conduction cooling type superconducting magnet system for cooling a superconducting coil by transmitting cold heat from a refrigerator to a superconducting coil accommodated in a vacuum vessel, wherein the compressor supplies compressed refrigerant gas to the refrigerator. An inverter that varies the operating frequency of the compressor, a temperature sensor that detects the temperature of the superconducting coil, and control means that controls an output frequency of the inverter based on a temperature detection signal detected by the temperature sensor. A conduction-cooled superconducting magnet system, wherein the refrigerating capacity of the refrigerator is varied by controlling an operating frequency of a compressor according to a temperature of the superconducting coil. 3. The conduction cooling type superconducting magnet system according to claim 2, wherein said control means outputs a frequency determined based on a predetermined relationship between a refrigerating capacity of said refrigerator and an operating frequency of said compressor. A conduction-cooled superconducting magnet system, characterized in that: 4. The superconducting magnet system according to claim 1, wherein said control means includes a magnet power supply for exciting said superconducting coil according to a temperature of said superconducting coil detected by said temperature sensor. A conduction-cooled superconducting magnet system having a function of controlling output. 5. The conduction-cooled superconducting magnet system according to claim 1, wherein the temperature sensors are respectively provided at a plurality of different positions of the superconducting coil.