JP2006324325A - Super-conducting magnet apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a super-conducting magnet apparatus not needing a large-sized helium refrigerator by reducing the injection amount of liquid heluim by minimizing the amount of consumption of the liquid heluim or realizing an apparatus of a small-sized refrigetator with reduced consumption of liuid heluim. <P>SOLUTION: The super-conducting magnet apparatus includes a super-conducting coil 1 contained in a vacuum heat insulation container 4 and dipped in liquid helium 3, or including a conduction cooling type super-conducting coil not using liquid helium, a current lead for guiding a current from an external power supply to the super-conducting coil 1 is constructed by connecting in series an ordinary temperature side current lead 10 formed of a copper conductor or a copper alloy conductor, an intermediate current lead 9a formed of a high temperature superconductor, and a low temperature side current lead 8 formed of the high temperature superconductor. The intermediate current lead 9a and the low temperature side current lead 8 are disposed in a heat insulation vacuum region, and a connection part 11 between the intermediate current lead and the low temperature side current lead is cooled with a small-sized refrigerator 12 without supplying cooling gas or liquid into the current lead. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention relates to a superconducting magnet device, particularly a superconducting device for an accelerator, nuclear fusion, industrial use, etc. The present invention relates to a superconducting magnet device.

  The superconducting coil of the superconducting device is cooled by a cryogenic refrigerant such as liquid helium or cooled by conduction with a small refrigerator, so that the superconducting state is maintained. It is stored in a container. In order to excite the superconducting coil, a current lead is incorporated into the vacuum heat insulating container and connected to an external power source to energize the exciting current.

  At this time, since the normal temperature part and the cryogenic part are connected, if a large amount of heat enters the cryogenic part via this current lead, a large amount of expensive liquid helium will be consumed, and a large The superconducting magnet device requires a dedicated large helium refrigerator.

  Therefore, the current lead is self-cooled using the low-temperature helium gas vaporized by the heat intrusion by itself, and the heat intrusion due to conduction from the room temperature side and the Joule heat generation due to energization are suppressed as much as possible. It is configured with consideration given to

  In general, good conductor metals such as copper or copper alloys have been used as conductors for current leads, but high-temperature superconductors have been discovered and their extremely high critical temperature (the upper limit temperature that can maintain the superconducting state). ) Effectively, the superconducting state can be maintained even in the liquid nitrogen temperature state, resulting in zero Joule heat generation in the low-temperature part, and the thermal conductivity of the high-temperature superconductor is 1/100 that of copper, reducing the amount of heat penetration. Expected to be able to suppress, the development of current leads using high-temperature superconductors has been carried out. (For example, refer to Patent Document 1).

JP-A-11-340027

  FIG. 7 is a cross-sectional configuration diagram illustrating an example of a superconducting device to which the conventional current lead disclosed in Patent Document 1 is applied. In FIG. 7, the superconducting coil 1 is housed in a liquid helium container (not shown), is provided with a radiation shield 6 and is housed in the heat insulating vacuum container 4.

  The superconducting coil 1 is connected to an external power source (not shown) through a low-temperature side current lead 27 made of a metallic superconducting conductor, an intermediate lead 9a made of a high-temperature superconducting conductor, and a room-temperature side current lead 10. The high temperature stage 28a of the small refrigerator 12a cools the connecting portion of the high temperature side current lead 10 and the intermediate current lead 9a and the width shield 6 and the low temperature side stage 28b connects the low temperature ends of the superconducting coil 1 and the low temperature side current lead 27. It is cooling.

  According to the above configuration, the heat intrusion is reduced by using the high temperature superconducting conductor. However, in a high current apparatus in which the current lead is thick, the heat intrusion into the liquid helium container cannot be made sufficiently small. Since the operating temperature of the conductor is high, there is a problem that the current carrying capacity is limited.

  For this reason, the large current device cannot be cooled by a small refrigerator, and a large helium refrigerator is required, which makes it difficult to simplify the system. In addition, the superconducting magnet apparatus using the helium injection method has a problem that the consumption of liquid helium is large and the liquid helium cost required for operation cannot be reduced.

  The present invention solves the above problems, and even in a superconducting magnet device having a relatively large current of several kiloamperes or higher, the consumption of liquid helium is minimized to reduce the amount of liquid injection, An object of the present invention is to provide a superconducting magnet device that does not require a large-sized helium refrigerator by realizing a device that does not consume liquid helium with a small 4K refrigerator.

  It is another object of the present invention to provide a manufacturing method suitable for this apparatus by simplifying the structure of the current lead portion, and also provide means for facilitating operation and maintenance.

  The superconducting magnet device according to the present invention is a superconducting magnet device that is housed in a vacuum heat insulating container and is immersed in liquid helium or a conduction-cooled superconducting coil that does not use liquid helium. The current lead that conducts the current from the normal temperature side current lead made of copper conductor or copper alloy conductor, the intermediate current lead made of high temperature superconductor, and the low temperature side current lead made of high temperature superconductor are connected in series In addition, the intermediate current lead and the low temperature side current lead are disposed in the adiabatic vacuum region, and the connecting portion between the intermediate current lead and the low temperature side current lead is passed through the current lead without passing cooling gas or liquid. Is cooled with a small refrigerator.

  According to this invention, the amount of liquid helium can be minimized to reduce the amount of liquid injection, or a device that does not consume liquid helium can be realized with a small 4K refrigerator, eliminating the need for a large helium refrigerator. be able to. Further, the structure of the current lead part is simplified, and the operation and maintenance becomes easy.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a cross-sectional view schematically showing a superconducting magnet apparatus according to Embodiment 1. FIG. As shown in this figure, the superconducting coil 1 is housed in a liquid helium container 2, covered with a radiation shield 6 and housed in a heat insulating vacuum container 4 in order to reduce heat penetration from room temperature.

  A helium tank 5 is coupled to the liquid helium container 2 so that liquid helium 3 is injected via a liquid helium liquid injection pipe 16 and helium gas 3G is discharged via a helium gas exhaust pipe 17. It is comprised so that.

  A superconducting wire coil lead 7 connected to the superconducting coil 1 is connected in series with a low temperature side current lead 8 and an intermediate current lead 9a made of a high temperature superconductor and a room temperature side current lead 10 made of a copper conductor or a copper alloy conductor. A current lead configured to connect to is connected. The helium tank 5 is also provided with a feedthrough 13, and the superconducting wire coil lead 7 is taken out to the heat insulating vacuum region 15 through the feedthrough 13.

  One end of the low temperature side current lead 8 is connected to the superconducting wire coil lead 7. Further, the vicinity of the connection portion between the low-temperature side current lead 8 and the intermediate current lead 9a is cooled by the small refrigerator 12, and is cooled to a temperature (for example, 10K) considerably lower than the liquid nitrogen temperature. FIG. 1 illustrates a state in which the intermediate terminal 11 is in thermal contact with the low temperature side stage of the small refrigerator 12 through electrical insulation not shown.

  The room temperature side current lead 10 is taken out from the feedthrough 13 to the atmosphere side and cooled by the liquid nitrogen 18 in the liquid nitrogen jacket 19 provided on the atmosphere side and its evaporated gas. Reference numeral 20 denotes a liquid nitrogen injection pipe provided in the liquid nitrogen jacket 19, and 14 denotes a normal temperature side terminal provided in the normal temperature side current lead 10.

  Next, the operation of the first embodiment will be described. The room temperature side current lead 10 and the superconducting wire coil lead 7 are connected by a low temperature side current lead 8 and an intermediate current lead 9a, and the intermediate terminal 11 connecting 8 and 9a is cooled by a small refrigerator 12.

The intermediate current lead 9a is composed of a high-temperature superconductor. However, since the temperature range to be used is higher than that of the low-temperature side current lead 8, a current carrying capacity larger than that of the low-temperature side current lead 8 is required.
Intrusion heat from the intermediate current lead 9 a is cooled by the small refrigerator 12. The cooling capacity of the small refrigerator 12 is larger when it is operated by being attached to the intermediate terminal 11 where the temperature is higher than when it is operated at the temperature of the liquid helium container 2 (about 4.5K). Heat can be removed.

  As described above, according to the first embodiment, the temperature at the high temperature end (on the intermediate terminal 11 side) of the low temperature side current lead 8 is lowered, the heat penetration into the liquid helium container 2 is greatly reduced, and the low temperature side current is reduced. Since the temperature of the entire lead 8 is lowered, the performance of the high-temperature superconductor can be further extracted and the current carrying capacity can be increased. That is, even when the current value is several kiloamperes or more, low heat penetration can be realized.

  In the first embodiment, since the low-temperature side current lead 8 made of a high-temperature superconductor is placed in an adiabatic vacuum, even if it is damaged, an access port (not shown) of the adiabatic vacuum container 4 is opened, Operations such as replacement can be easily performed.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view schematically showing the superconducting magnet device according to the second embodiment. In this figure, the same or corresponding parts as in FIG. The difference from FIG. 1 is that the intermediate current lead 9a in FIG. 1 is replaced with an intermediate current lead 9b made of a copper conductor.

In the second embodiment, in order to minimize the heat penetration amount Qc2 to the low temperature side of the helium tank 5, the ratio of the length L of the intermediate current lead 9b (hereinafter referred to as the lead 9b) and the cross-sectional area of the lead 9b is optimal. It is necessary to make it. The reason will be described below.
The heat conduction equation of the lead 9b is

Can be written. Here, x is the position of the lead 9b in the length direction, T is the temperature of the lead 9b at the position x, λ (T) is the thermal conductivity of the lead 9b at the temperature T, and ρ (T) is the lead 9b at the temperature T. The electrical resistivity, I is the current flowing through the lead 9b, and S is the cross-sectional area of the lead 9b. Solving Eq. (1) with the boundary conditions of (2) and (3) with constant λ and ρ,
In order to minimize the amount of heat penetration Qc2 to the low temperature side, the length L and area S of the lead 9b are set.

It is necessary to do. In fact, when the lead 9b is made of copper (usually electrolytic copper), in the target temperature range (20 to 80 Kelvin (K)), λ = 1000 W / Km and ρ = 6 × 10 ⁻¹⁰ Ωm L = 1.41 × 10 ⁷ S / I.

  When the lead 9b is made of copper (electric copper), the cost can be greatly reduced as compared with the case where the lead 9b is made of a high-temperature superconductor. Since heat penetration into the liquid helium container 2 is mainly determined by the low-temperature side lead, the amount of heat penetration hardly changes even when the lead 9b is made of copper.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described. In the third embodiment, the lead 9b in FIG. 2 is made of phosphorous deoxidized copper or a copper alloy. Illustration is omitted.
In the third embodiment, in order to minimize the heat penetration amount Qc2 to the low temperature side of the helium tank 5, it is necessary to optimize the ratio of the length L of the lead 9b to the cross-sectional area of the lead 9b. The reason will be described below. The heat conduction equation of the lead 9b is

Can be written. Here, x is the position in the length direction of the lead 9b, T is the temperature of the lead 9b at the position x, λ (T) is the thermal conductivity of the lead 9b at the temperature T, and ρ (T) is the lead 9b at the temperature T. The electrical resistivity, I is the current flowing through the lead 9b, and S is the cross-sectional area of the lead 9b. Solving Eq. (5) with the boundary conditions of (6) and (7) with constant λ and ρ,
In order to minimize the amount of heat penetration Qc2 to the low temperature side, the length L and area S of the lead 9b are set.

It is necessary to do. In the case of phosphorous deoxidized copper, since λ = 96 W / Km and ρ = 3.7 × 10 ⁻¹⁰ Ωm, L = 1.76 × 10 ⁶ S / I may be set.

Now, when considering the 4000A as a current value of the device, whereas if the copper becomes the length of even 1.4m against practical cross-sectional area 400 mm ² of the lead 9b, in the case of phosphorus deoxidized copper 0.18m Is the optimum length. Obviously, it is more compact and easier to handle than copper.
The amount of heat penetration Qc2 when the optimum L / S is used is

  Can be written. Whether the lead 9b is composed of a high-temperature superconductor, a copper conductor, or a copper alloy conductor is selected by each superconducting magnet device in consideration of the energizing current, the capacity of the refrigerator, the manufacturing cost, etc., and the performance and manufacturing cost It can be set as a device with a good balance.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a cross-sectional view schematically showing the superconducting magnet device according to the fourth embodiment. In the first to third embodiments, the amount of helium consumed as a form in which the heat of vaporization of liquid helium is absorbed by the heat of vaporization of liquid helium and the generated helium gas is released is greatly reduced. In the fourth embodiment, a recondensing type superconducting magnet device is constructed in which the range shield is doubled and a small refrigerator is added to further reduce the consumption of liquid helium.

  In FIG. 3, reference numeral 21 denotes a low-temperature side range shield added in the fourth embodiment, and 12b and 12c denote additional small refrigerators. Since other configurations are the same as those in FIG. 1, the same reference numerals are given to the same portions, and descriptions thereof are omitted.

  The required number of small refrigerators is determined by the size of the apparatus, and in the small apparatus, one additional 12b may be added. The range shield 21 is cooled by the high temperature side stage of the small refrigerator, and the temperature is set to about 35K. The radiation shield 6 is cooled by liquid nitrogen (not shown) and liquid nitrogen flowing in the pipe.

3 illustrates the superconducting coil 1 immersed in the liquid helium 3. However, the same structure can be applied to an apparatus that employs the conduction cooling type superconducting coil 1 that does not use the liquid helium 3. It is.
As described above, the radiation shield is doubled as shown by 6 and 21, and a refrigerating superconducting magnet device that further suppresses the consumption of liquid helium 3 is obtained by adding a small refrigerator. Can do.

Embodiment 5. FIG.
Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a cross-sectional view schematically showing the superconducting magnet device according to the fifth embodiment. In the fourth embodiment, the room temperature side current lead 10 is cooled by the liquid nitrogen 18 stored in the liquid nitrogen jacket 19, but in the fifth embodiment, as shown in FIG. The portion is placed in the adiabatic vacuum region 15 and cooled from the liquid nitrogen pipe 22 via the heat transfer body 23.

The liquid nitrogen pipe 22 cools the radiation shield 6 after cooling the room temperature side current lead 10. The heat transfer body 23 and the room temperature side current lead 10 are electrically insulated.
Thus, by taking out from the vacuum at room temperature, the room temperature feedthrough 24 can be adopted, and the problem of frost and freezing around the feedthrough can be avoided.

Embodiment 6 FIG.
Next, a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a cross-sectional view schematically showing the superconducting magnet device according to the sixth embodiment. In this figure, the same or corresponding parts as in FIG. The difference from FIG. 4 is that a thermal anchor 25 is added to the high temperature side stage of the small refrigerator 12 to cool the middle part of the lead 9a, thereby realizing a more efficient device. The thermal anchor 25 is made of, for example, a copper braided wire.

  By comprising in this way, intrusion heat can be removed in the temperature range with high freezing function power, and the temperature of the intermediate terminal 11 can be lowered. This leads to an increase in the current carrying capacity of the low-temperature side current lead 8 and a decrease in heat penetration into the helium vessel 2, and it is possible to realize a superconducting magnet apparatus that does not consume helium even in a larger current apparatus.

Embodiment 7 FIG.
Next, a seventh embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a cross-sectional view schematically showing the superconducting magnet device according to the seventh embodiment. In the fifth and sixth embodiments, the room temperature side current lead 10 is cooled from the liquid nitrogen pipe 22 via the heat transfer body 23. However, in the seventh embodiment, the room temperature side current lead 10 is shown in FIG. Most of them are placed on the atmosphere side and cooled by heat conduction from the liquid nitrogen pipe 22 and the heat transfer body 23 on the atmosphere side.

The entire cooling unit is covered with a dew condensation prevention material 26 to prevent dew condensation and icing.
By placing the cooling portion of the room temperature side current lead 10 on the atmosphere side, adjustment of cooling performance, maintenance of the portion, and the like are facilitated.

It is sectional drawing which shows typically the superconducting magnet apparatus by Embodiment 1 of this invention. It is sectional drawing which shows typically the superconducting magnet apparatus by Embodiment 2 of this invention. It is sectional drawing which shows typically the superconducting magnet apparatus by Embodiment 4 of this invention. It is sectional drawing which shows typically the superconducting magnet apparatus by Embodiment 5 of this invention. It is sectional drawing which shows typically the superconducting magnet apparatus by Embodiment 6 of this invention. It is sectional drawing which shows typically the superconducting magnet apparatus by Embodiment 7 of this invention. It is a cross-sectional block diagram which shows the example of the conventional superconducting magnet apparatus.

Explanation of symbols

1 superconducting coil, 2 liquid helium container, 3 liquid helium,
4 Insulated vacuum vessel, 5 Helium tank, 7 Superconducting wire coil lead,
8 Low temperature side current lead,
9a, 9b Intermediate current lead, 10 Room temperature side current lead, 11 Intermediate terminal,
12, 12b, 12c small refrigerator, 19 liquid nitrogen jacket,
21 Low-temperature radiation shield, 22 Liquid nitrogen piping, 23 Heat transfer element,
24 Room temperature feedthrough, 25 Thermal anchor, 26 Anti-condensation material.

Claims (7)

  In a superconducting magnet device having a superconducting coil that is housed in a vacuum heat insulating container and immersed in liquid helium or a conduction-cooling superconducting coil that does not use liquid helium, a current lead that guides a current from an external power source to the superconducting coil, A room temperature side current lead made of a copper conductor or a copper alloy conductor, an intermediate current lead made of a high temperature superconductor, and a low temperature side current lead made of a high temperature superconductor are connected in series. The side current lead is disposed in the adiabatic vacuum region so that the connecting portion between the intermediate current lead and the low temperature side current lead is cooled by a small refrigerator without passing cooling gas or liquid through the current lead. A superconducting magnet device characterized by that.   2. The superconducting magnet device according to claim 1, wherein the intermediate current lead is made of a copper conductor.   2. The superconducting magnet device according to claim 1, wherein the intermediate current lead is made of a phosphorous deoxidized copper or a copper alloy conductor.   A double radiation shield is provided in the vacuum heat insulating container, and the helium tank is cooled by a small refrigerator to form a helium recondensing type that does not consume liquid helium. 4. The superconducting magnet device according to any one of items 3.   5. The superconducting magnet device according to claim 4, wherein the room temperature side current lead is cooled by heat conduction from a liquid nitrogen pipe in an adiabatic vacuum.   6. The superconducting magnet according to claim 5, wherein an intermediate portion of the intermediate current lead is cooled from a high temperature side stage of a small refrigerator that cools a connection portion between the low temperature side current lead and the intermediate current lead. apparatus. The superconducting magnet device according to claim 4 or 6, wherein the room temperature side current lead is cooled from a liquid nitrogen pipe and a heat transfer body provided on the atmosphere side.

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