JPH0697643B2 - Superconducting magnet device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a superconducting magnet device provided with a voltage terminal lead used for detecting a terminal voltage of the superconducting coil for protecting the superconducting coil, and particularly to a voltage terminal lead. The present invention relates to a superconducting magnet device having a structure effective in preventing the dielectric breakdown of the above.

[Conventional technology]

Conventionally, in a superconducting magnet device, Japanese Patent Laid-Open No. 62-1
As described in Japanese Unexamined Patent Publication No. 76108, a normal conduction transition (hereinafter referred to as quench) of a superconducting coil being excited at a cryogenic temperature is detected,
The superconducting coil is protected by, for example, cutting off the exciting current to the superconducting coil when a quench is detected. One of the quench detection methods is to pull out the voltage terminal lead from the superconducting coil and monitor the terminal voltage with a voltmeter installed in a room temperature space.This method is simple and effective and is widely used. Has been.

Next, the wiring of the superconducting magnet device and the configuration of the conventional device will be described. FIG. 3 is a wiring connection diagram of the superconducting magnet device, and FIG. 4 is a schematic configuration diagram of a conventional superconducting magnet device. In particular, a path and a voltage for extracting the voltage terminal leads into the room temperature space from both ends of the superconducting coil in the cryogenic portion. It is a figure which shows the structure of a terminal lead.

As shown in FIGS. 3 and 4, in the superconducting magnet device, the superconducting coil 1 is housed in the cryostat 2 and cooled by a cooling medium such as liquid helium 3. The superconducting coil 1 is connected to a current power lead 4 capable of passing a large current, and the other end of the current power lead 4 is connected to an exciting power source 8 installed in a room temperature space outside the cryostat 2. Further, a voltage terminal lead 5 is connected to the superconducting coil 1 together with a current power lead 4, and the other end of the voltage terminal lead 4 is connected via an electric wire 6 to a quench detection circuit 7 installed in a room temperature space. .

Here, the operation of the superconducting magnet device will be described.
When the current of the excitation power supply 8 is increased, this current starts flowing through the current power lead 4 to the superconducting coil 1. At that time, the current increasing speed (di
/ dt) and the impedance of the superconducting coil 1 (L [H])
A voltage of product V _t = −L · di / dt [V] is generated. This voltage V _t is detected by the quench detection circuit 7 via the voltage terminal lead 5 and the electric wire 6. If the superconducting coil is normal and in the superconducting state, the detected voltage V _t is approximately equal to the calculated voltage value.

When the superconducting coil 1 is quenched, the resistance of the superconducting coil 1 rapidly increases, so that the current sharply decreases. Therefore, the voltage V _t represented by L · di / dt has a very high value. At this time, the quench detection circuit 7 that has detected the high voltage V _t issues a cutoff command to the excitation power supply 8. Thus, the excitation power source 8 is cut off, and the superconducting coil 1 can be prevented from burning.

By the way, in the superconducting magnet device shown in FIG.
The current power lead 4 is a gas cooling power lead cooled by the vaporized gas 9 of liquid helium. The vaporized gas 9 is caused to flow in the current power lead 4 and flow out to the outside from the gas outlet 10 provided in the current power lead. At this time, the evaporated gas removes the Joule heat generated in the power lead due to its sensible heat and the heat penetrating through the current power lead from the room temperature space, and discharges it to the outside. On the other hand, the voltage terminal lead 5 is arranged at a position apart from the current power lead 4 along with the current power lead, and is drawn out from another portion of the cryostat 2 to the outside. Therefore, the voltage terminal lead 5 needs a thick insulating coating that can withstand the high voltage at the time of quenching, and is not cooled by the flow of the evaporative gas unlike the current power lead, and thus needs a thicker conductor.

[Problems to be Solved by the Invention]

When the superconducting coil is quenched during the excitation operation, the terminal voltage of the superconducting coil may reach several thousand volts. Therefore, the electric insulation of the voltage terminal lead drawn out from the cryogenic part to the room temperature room has been carefully taken conventionally.
However, in the experimental stage of superconductivity, a burnout accident of the superconducting magnet often occurs due to the dielectric breakdown between the voltage terminal lead and the cryostat or its accompanying components.

In order to strengthen the electric insulation, the conductor of the voltage terminal lead may be thickened and the insulating coating may be thickened. However, the voltage terminal lead becomes large, which increases the amount of heat that penetrates from the room temperature space to the low temperature portion, and the size of equipment such as the cryostat becomes large, resulting in a decrease in thermal efficiency due to an increase in the amount of refrigerant evaporated. Especially recently, a design has been made to reduce the penetration of heat as much as possible by narrowing the mounting part of the current power lead. This also applies to a rotary cryostat used in a rotating state, and it is difficult to dispose a conventional voltage terminal lead due to the narrow lead-out portion of the current power lead, and it may happen that the installation location cannot be secured.

The present invention has been made in view of the above circumstances,
To provide a superconducting magnet device having a structure in which the voltage terminal lead is arranged in a form attached to the current power lead so that the insulation of the voltage terminal lead is stabilized and the installation location is narrowed. It is an object.

[Means for Solving the Problems]

As seen in FIG. 4, the current power lead 4 and the voltage terminal lead 5 are connected to the end portion of the superconducting coil 1 at substantially the same location. This means that the current power lead 4 and the voltage terminal lead 5 are always at substantially the same potential regardless of the steady operation or the quench.

In general, a thick conductor is used for the current power lead because a large current of several hundreds to several thousands of amperes flows therethrough. Further, in order to remove Joule heat generated in the conductor and heat penetrating from the room temperature space, a gas cooling power lead structure using a refrigerant gas of liquid helium is adopted. Therefore, the current power lead is made very strong, and is made to have a sufficient electric breakdown voltage of several thousand V generated at the time of quenching.

The present invention focuses on the fact that the electric potentials of the current power lead and the voltage terminal lead are substantially the same as described above, and the voltage is applied to the inside or the contact of the current power lead having a sturdy structure and a sufficient electric insulation withstand voltage. The structure is such that leads are arranged.

Therefore, the superconducting magnet device of the present invention comprises a cryostat, a superconducting coil installed in the refrigerant liquid in the cryostat, and a current power lead and a voltage terminal lead arranged from the outside of the cryostat to the superconducting coil, Further, the current power lead has a gas cooling power lead structure that is cooled by the refrigerant gas that evaporates from the refrigerant liquid and flows out to the outside, and the voltage terminal lead is disposed through or in contact with the current power lead. It is characterized by that.

More specifically, the current power lead is a refrigerant flowing out to the outside through a flow path formed between a conductor of the current power lead and an outer cylinder surrounding the conductor and attached to the conductor. It is cooled by the evaporating gas of the liquid, while the voltage terminal lead is wound around the conductor of the current power lead.

Regarding the voltage terminal lead, a hole may be provided in the axial center portion of the current power lead and the voltage terminal lead may be disposed through the hole, or a fin may be attached spirally around the conductor outer periphery of the current power lead. A hole may be formed in the conductor parallel to the axis and the voltage terminal lead may be disposed through the hole, or the voltage terminal lead may be disposed by being wound around the outer cylinder.

[Action]

If the current power lead and the voltage terminal lead are separately pulled out from the superconducting coil as in the conventional case, both the current power lead and the voltage terminal lead need to have a high withstand voltage structure. As mentioned above, the current power lead is made strong because it requires a large current to flow, so it is easy to have a high withstand voltage structure.On the other hand, the voltage terminal lead allows almost no current to flow and that the conductor is transmitted from the room temperature space. In order to reduce incoming heat as much as possible, an electric wire having a soft structure in which a thin copper wire is covered with an absolute material having a withstand voltage of several thousand V is often used. Therefore, the installation work inside the cryostat is difficult and easily scratched,
During the experiment, dielectric breakdown occurred on the voltage terminal lead due to the fact that it was cooled to about 270 ° C and cracked.

According to the present invention, the voltage terminal lead is arranged in or integrated with the current power lead of the high withstand voltage structure so that the withstand voltage between ground (to the cryostat) is held by the current power lead. The electrical insulation withstand voltage of the terminal lead may be a voltage drop of the current power lead and the voltage drop due to the connection resistance of the superconducting coil current power lead, which is about several volts, and a thin insulation-coated electric wire can be adopted and the arrangement is easy. Become.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a superconducting magnet device according to the present invention.

In the superconducting magnet device shown in FIG. 1, the structure and arrangement other than the current power lead 4 and the voltage terminal lead 5 are almost the same as described with reference to FIG. 4, and the wiring connection of the superconducting magnet device is the same. is there. Therefore, the description of those same parts is omitted to avoid duplication,
The different current power lead 4 and voltage terminal lead 5 will be mainly described.

In FIG. 1, the current power lead 4 is a superconducting coil 1.
4a to be connected to and liquid helium 3 surrounding conductor 4a
The outer cylinder 4b includes an outer cylinder 4b having an opening above the liquid surface, and a fin 4c spirally provided on the outer circumference of the conductor 4a.
A gas outlet 10 is provided in the portion protruding to the room temperature space. The voltage terminal lead 5 is guided by being spirally wound around the outer periphery of the conductor 4a from a connection point with the superconducting coil 1, and is provided on a portion of the outer cylinder 4b protruding into the room temperature space,
Further, it is connected to the quench detection circuit 7 via the electric wire 6.

Also, the refrigerant gas of liquid helium 3 passes through the spiral flow path created by the fins 4c from the opening of the outer cylinder 4b, and the gas extraction port
It flows out through 10. At this time, the refrigerant gas 9 cools the current power lead 4 and the voltage terminal lead 5 by its sensible heat, and the Joule heat generated in the current power lead 4 and the cryostat 2 from the outside through the current power lead 4 and the voltage terminal lead 4. It takes the heat that penetrates inside and releases it to the outside. Since the voltage terminal lead 5 is integrated with the current power lead 4 as described above, the current power lead 4 can be provided with an electric withstand voltage against a high voltage generated when the superconducting coil is quenched, and the insulation coating of the voltage terminal lead 5 is provided. Can be made thin, and the conductor of the voltage terminal lead 5 can be made thin and flexible by the effect of cooling,
As a result, the wiring of the voltage terminal lead can be facilitated, and the place for disposing the voltage terminal lead can be secured.

In the first embodiment shown in FIG. 1, the voltage terminal lead 5 is wound around the conductor 4a of the current power lead 4,
In addition, the voltage terminal lead 5 is used as an outer cylinder of the current power lead 4.
Wrap around 4b. Alternatively, a hole is provided in the shaft center portion of the conductor 4a of the current power lead 4 and the voltage terminal lead 5 is passed through the hole,
Alternatively, the fin 4c of the current power lead 4 may be provided with a hole in parallel with the conductor 4a, and a rigid voltage terminal lead may be inserted into the hole. Even with these structures,
As in the embodiment, the current power lead 4 can have an electric withstand voltage against a high voltage at the time of quenching,
The voltage terminal lead 5 can be made thin, and a place for disposing the voltage terminal lead can be secured. Furthermore, since the voltage terminal lead is along the current power lead, it can be wired in a straight line, the amount of wire used is smaller than before, and the weight of the superconducting magnet device can be reduced. The miniaturized and lightweight superconducting magnet device as described above is very effective when applied to a rotary cryostat to which a high rotational centrifugal force is applied. The coolant is not limited to liquid helium, and liquid nitrogen, which is compatible with the constituent material of the superconducting coil and the like, may be used.

FIG. 2 is a diagram showing a second embodiment of the present invention. In the second embodiment, in addition to the superconducting magnet device of the first embodiment, a current terminal contact is provided between the current power lead and the superconducting coil, and a voltage terminal contact is further provided between the voltage terminal lead and the superconducting coil. There is. Except for these added portions, the other constituent portions are the same as those in the first embodiment, so the description is omitted and only the added portions will be described.

In FIG. 2, a current terminal contact 12 connected to the superconducting coil 1 is fixed on a frame provided on the superconducting coil 1,
The current terminal contact 12 is configured so that the tip of the conductor 4a of the current power lead 4 is fitted. In addition, the voltage terminal contact 13 connected to the superconducting coil 1 is connected to the current terminal contact on the frame.
It is configured to be fixed next to 12 and to be fitted with a voltage terminal piece 14 which is insulated from the opening portion of the outer cylinder 4b of the current power lead 4 and is attached to the voltage terminal lead 5. In the figure, the current power lead on the left side shows the state of being attached to the current terminal contact 12, and the current power lead on the right side shows the state of being pulled out. The voltage terminal lead 5 connected to the voltage terminal piece 14 passes through the current power lead 4 and is guided from the voltage connection terminal 11 to the quench detection circuit 7 by the electric wire 6. in this case,
The voltage terminal lead is not useful after the current power lead is pulled out, but it can be effectively used to detect the quench that occurs when the current power lead is attached and the superconducting magnet is excited and demagnetized.

〔The invention's effect〕

According to the present invention, in the superconducting magnet device, since the voltage terminal lead is disposed through or in contact with the current power lead, the electrical insulation of the voltage terminal lead is essentially robust in structure and has a high withstand voltage. It is possible to rely on the current power lead, the conductor wire of the voltage terminal lead can be made thin, and the insulation coating can be made thin. it can. Further, since the voltage terminal lead is cooled by the refrigerant gas that evaporates from the refrigerant liquid that cools the superconducting coil together with the current power lead and flows out to the outside, the voltage terminal lead penetrates through the current power lead from the Joule heat generated in the current power lead and the room temperature space. The heat that enters the voltage terminal leads along with the heat can be removed by the refrigerant gas, and the thermal efficiency of the entire device can be increased.

It is very effective when the device of the present invention, which has been downsized, reduced in weight and improved in thermal efficiency as described above, is applied to a rotary cryostat to which high rotary centrifugal force is applied.

[Brief description of drawings]

1 is a schematic configuration diagram of a first embodiment of a superconducting magnet device according to the present invention, FIG. 2 is a schematic structural diagram of a second embodiment of the present invention, FIG. 3 is a wiring connection diagram of the superconducting magnet device, FIG. 4 is a schematic configuration diagram of a conventional superconducting magnet device. 1 ... Superconducting coil, 2 ... Cryostat, 3 ...
Liquid helium, 4 ... Current power lead, 4a ... Current power lead conductor, 4b ... External cylinder, 4c ... Fin, 5 ...
Voltage terminal lead, 6 ... Electric wire, 7 ... Quench detection circuit, 8 ... Excitation power supply, 9 ... Refrigerant gas, 10 ... Gas outlet, 11 ... Voltage connection terminal, 12 ... Current terminal contact, 13 …
… Voltage terminal contacts.

Claims (7)

[Claims] 1. A cryostat, a superconducting coil installed in a refrigerant liquid in the cryostat, a current power lead and a voltage terminal lead arranged from the outside of the cryostat to the superconducting coil, and the current. In the superconducting magnet device, wherein the power lead has a gas cooling power lead structure that is cooled by a refrigerant gas that evaporates from the refrigerant liquid and flows out to the outside, the voltage terminal lead is disposed through the current power lead. Is a superconducting magnet device. 2. A cryostat, a superconducting coil installed in a refrigerant liquid in the cryostat, and a current power lead and a voltage terminal lead arranged from outside the cryostat to the superconducting coil. The lead is a vaporized refrigerant gas of the refrigerant liquid flowing out to the outside through a flow path formed between the conductor of the current power lead and an outer cylinder surrounding the conductor and attached to the conductor, In the cooled superconducting magnet device, the voltage terminal lead is wound around the conductor of the current power lead and arranged. 3. A cryostat, a superconducting coil installed in a refrigerant liquid in the cryostat, and a current power lead and a voltage terminal lead arranged from outside the cryostat to the superconducting coil. The lead is a vaporized refrigerant gas of the refrigerant liquid flowing out to the outside through a flow path formed between the conductor of the current power lead and an outer cylinder surrounding the conductor and attached to the conductor, In the superconducting magnet device to be cooled, the voltage terminal lead is provided through a hole provided in an axial center portion of the current power lead, the superconducting magnet device. 4. A cryostat, a superconducting coil installed in a refrigerant liquid in the cryostat, and a current power lead and a voltage terminal lead arranged from the outside of the cryostat to the superconducting coil. The lead is a vaporized refrigerant gas of the refrigerant liquid flowing out to the outside through a flow path formed between the conductor of the current power lead and an outer cylinder surrounding the conductor and attached to the conductor, In the cooled superconducting magnet device, the voltage terminal lead is arranged in a fin spirally attached to the outer periphery of the conductor of the current power lead through a hole provided in parallel to the conductor. Superconducting magnet device. 5. A cryostat, a superconducting coil installed in a refrigerant liquid in the cryostat, a current power lead and a voltage terminal lead arranged from the outside of the cryostat to the superconducting coil, and the current power. The lead is a vaporized refrigerant gas of the refrigerant liquid flowing out to the outside through a flow path formed between the conductor of the current power lead and an outer cylinder surrounding the conductor and attached to the conductor, In the superconducting magnet device to be cooled, the voltage terminal lead is wound around the outer cylinder and disposed. 6. The cryostat is a rotary cryostat that is rotationally driven.
The superconducting magnet device described. 7. A superconducting magnet device according to claim 1, wherein attachment / detachment devices are provided at each of a connecting portion between the current power lead and the superconducting coil and a connecting portion between the voltage terminal lead and the superconducting coil.