JP3533689B2 - Current switch for superconducting magnet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current switch for interrupting a permanent current in a superconducting coil for generating a magnetic field of a superconducting electromagnet. 2. Description of the Related Art A superconducting electromagnet utilizes a superconducting phenomenon in which an electric resistance becomes zero when a coil formed of a superconducting material is cooled to a temperature close to absolute zero. Since it has a feature that an extremely large current can flow to generate a high magnetic field, it is used, for example, as a bending electromagnet of an accelerator. The superconducting electromagnet is operated in a permanent current mode using the principle of superconductivity, and a switch for that purpose, a so-called permanent current switch, is used in the circuit. FIG. 4 shows the principle of a permanent current switch. In the figure, reference numeral 1 denotes an electromagnet-side superconducting coil, 2 denotes an external power supply, and 3 denotes a permanent current switch. An electromagnet-side superconducting coil 1 made of a superconducting material is housed in a cryostat 4 of a superconducting electromagnet, and is connected to an external power supply 2 composed of a power supply body 5 and an internal resistor 6 and current leads 7, 7. Connected through.
The cryostat 4 is a closed container whose inside is filled with liquid helium and is kept at an extremely low temperature. The permanent current switch 3 is connected in series with the electromagnet-side superconducting coil 1 inside the cryostat 4. The permanent current switch 3 includes a switch-side superconducting coil 8 made of a superconducting material, and a heater 9 for changing the resistance of the coil 8. When the superconducting electromagnet 10 is operated in the permanent current mode, first, the value R ₁ of the power supply internal resistance 6 is reduced, the heater 9 is turned on, and the switch side superconducting coil 8 is turned on.
The by increasing the resistance value R ₂ of the switch-side superconducting coil 8 was heated, gradually increased to the electromagnet side superconducting coil 1 passing a current, which in the path of the (B). Thereafter, when the heater 9 of the permanent current switch 3 is turned off when a predetermined current flows through the electromagnet-side superconducting coil 1, the temperature of the switch-side superconducting coil 8 is reduced by the surrounding liquid helium, and the coil 8 There the resistance value R ₂ is a superconducting state is zero. Then, since the external power supply 2 includes the internal resistor 6, a current flows through the switch-side superconducting coil 8 having zero resistance, and no current flows through the external power supply 2. Therefore, when the current leads 7, 7 are disconnected, a permanent current flows through the path (A). Although the principle of the permanent current switch has been described above, the actual permanent current switch 3 is, as shown in FIG.
In addition to the switch-side superconducting coil 8 and the heater 9, the protection resistor 11 of resistance R ₃ it is provided. This is because the resistance value R ₂ of the switch-side superconducting coil 8 suddenly changes from zero to a high value when the switch-side superconducting coil 8 shifts from the superconducting state to the normal conducting state by the operation of the heater 9.
At this time, if the protection resistor 11 is not provided, the switch-side superconducting coil 8 generates heat rapidly and may burn out. Therefore, the protection resistor 11 is connected in parallel with the switch-side superconducting coil 8 to distribute the current and prevent burnout. As a specific example of the permanent current switch 3 based on the above principle, as shown in FIG. 6A, the heaters of the switch side superconducting coil 12 and the resistance wire coil 13 are formed in a cylindrical shape. The permanent current switch 1 covered with epoxy resins 14 and 14 and a heat insulating layer 15 and connected to a protective resistor 16 and a heater power supply 17 to form a circuit.
8 and as shown in FIG. 6B, the disk-shaped heating elements 2 are also provided on both sides of the thin disk-shaped switch-side superconducting coil 19.
There is a permanent current switch 21 provided with 0 and 20. [0009] However, the conventional permanent current switch 3 is mounted inside a cryostat 4 filled with liquid helium and maintained at a very low temperature, and the heater 9 is turned off. The switch-side superconducting coil 8 in the superconducting state is configured to be switched to the normal conducting state by heating the switch-side superconducting coil 8 by putting the heater 9 therein. Therefore, since the permanent current switch 3 is immersed in the liquid helium in the hermetically sealed cryostat 4, it is very difficult to perform maintenance, inspection, maintenance work, or replacement work of the permanent current switch. there were. The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a current switch for a superconducting electromagnet capable of easily performing maintenance, inspection, maintenance work, or replacement work. And In order to achieve the above object, a current switch for a superconducting electromagnet according to the present invention comprises a superconducting coil for generating a magnetic field inside a cryostat of a superconducting electromagnet and a superconducting coil outside the cryostat. A superconducting electromagnet current switch installed in a circuit constituted by a power supply and intermittently interrupting a permanent current of the magnetic field generating superconducting coil, wherein a switch-side superconducting switch connected in parallel with the magnetic field generating superconducting coil is provided. A coil, a container accommodating the switch-side superconducting coil, and a vacuum container accommodating the entire container, and the container is formed of either liquid helium or gas helium having a temperature in a normal conduction region. To selectively cool the switch-side superconducting coil to reduce the resistance to zero and cut off the cooling temperature. It is characterized in that it is configured to be replaced. In the current switch for a superconducting electromagnet of the present invention, a container to which either liquid helium or gaseous helium is selectively supplied is provided, and a switch-side superconducting coil is accommodated therein. When liquid helium is introduced into the container, the switch-side superconducting coil is cooled to 7 ° K or less, and when gas helium is introduced,
Heated above ° K. Therefore, in this superconducting electromagnet current switch, the conduction state of the switch-side superconducting coil is switched to either superconductivity or normal conduction by introducing either liquid helium or gaseous helium into the container. Has become. That is, independently of the cryostat filled with liquid helium, the conduction state of the switch-side superconducting coil can be switched only within the container, so that the vacuum container containing the container is installed outside the cryostat. Can function as a current switch. An embodiment of a current switch for a superconducting electromagnet according to the present invention will be described below with reference to FIGS. FIG.
FIG. 2 shows a permanent current switch 22 (current switch for a superconducting electromagnet) of the present embodiment, FIG. 2 shows a helium piping system of the permanent current switch 22, and FIG.
FIG. 4 is a diagram showing a state in which the permanent current switch 22 is installed on a superconducting electromagnet 59. As shown in FIG. It is installed in parallel with the electromagnet-side superconducting coil 54 outside the cryostat 53 in the circuit configured. In the figure, reference numeral 23 denotes a helium-filled container (container), 24 denotes a switch-side superconducting coil, and 25 denotes a vacuum container. As shown in FIG.
Is a tubular helium-filled container body 2 made of CuNi, for example.
6 and lids 28, 28 fixed to flanges 27, 27 formed at both ends thereof. A helium introduction pipe 29 and a helium discharge pipe 30 extending in a direction perpendicular to the main body 26 are connected to the vicinity of both ends of the helium-filled container main body 26, through which liquid helium or gaseous helium is introduced and discharged. It has become so. The switch-side superconducting coil 24 uses an S / C coil, which is a superconducting material, and is inserted into the helium-filled container 23 along the inner wall of the helium-filled container main body 26. . The two ends of the switch-side superconducting coil 24 are connected to the lid 28 of the helium-filled container 23.
Are connected respectively to the lead portions 31 attached to the. The entire helium-filled container 23 is housed in a vacuum container 25. This vacuum vessel 25 is, like the helium-filled vessel 23, a tubular vacuum vessel body 32.
And lids 34, 34 fixed to flanges 33, 33 formed at both ends thereof, and a vacuum exhaust pipe 35 extending in a direction orthogonal to this is provided on the side of the vacuum vessel main body 32. It is connected and communicates with a vacuum exhaust source (not shown), and a shutoff valve 36 is provided on the way. At both ends of the side opposite to the vacuum exhaust pipe 35, connection portions 37, 37 for connecting to the superconducting electromagnet circuit are provided, respectively, and through each connection portion 37, the switch side superconducting coil 24 and the circuit side are connected. The conductor 38 is connected. That is, a copper lead wire 39 is connected to the lead portion 31 at the end of the helium-filled container 23, and the lead wire 39 is connected to the circuit-side conductor 38 via a lead rod 40 having a male screw portion formed at the end. . The lead wires 39, 39, the lead rods 40, 40, and the circuit side wires 38, 38 are nuts 41,
.. Are fixed to the vacuum vessel 25, and are insulated from the vacuum vessel 25 by insulating plates 42, 42 sandwiched between nuts 41, 41,. On the other hand, as shown in FIG. 2, a liquid helium tank 43 and a helium cylinder 44 for supplying liquid helium or gaseous helium to the helium filled container 23.
Are provided outside the permanent current switch 22. FIG. 2 shows a helium piping system between the liquid helium tank 43, the helium cylinder 44, and the permanent current switch 22. A liquid helium introduction pipe 45 is connected to the liquid helium tank 43, and a gas helium introduction pipe 46 is connected to the helium cylinder 44.
The helium introduction pipe 29 on the helium filled container 23 side is connected to the helium introduction tube 29 via a three-way valve 47. Therefore, either the liquid helium or the gaseous helium is introduced into the helium filled container 23 by switching the three-way valve 47. Further, a branch pipe 48 of a gas helium introduction pipe 46 is introduced into the liquid helium tank 43, whereby the inside of the liquid helium tank 43 is pressurized so that the liquid helium flows into the helium filled container 23. I have. Further, a heater 49 is provided in the middle of the gas helium introduction pipe 46, and gas helium heated to about 10 ° K by the heater 49 flows into the helium filling container 23. On the other hand, the helium discharge pipe 30 of the helium filled container 23 is connected to the gas helium discharge pipe 51 through the three-way valve 50.
And a liquid helium discharge pipe 52, and gas helium or liquid helium derived from the helium filled container 23 is discharged through these discharge pipes 51 and 52, respectively. FIG. 3 shows the permanent current switch 22 having the above configuration.
FIG. As shown in this figure, the permanent current switch 22 is installed outside the cryostat 53, and the electromagnet-side superconducting coil 54 inside the cryostat 53 and the external power supply 55 are connected in series via circuit switches 56, 56. The circuit is used in parallel with the electromagnet-side superconducting coil 54 in the circuit. The external power source 55, the internal resistance of the power supply body 57 resistance R ₁ variable 58
It is composed of When using the permanent switch 22, first, the circuit switches 56, 56 are connected, and the value R1 of the internal resistor 58 of the external power supply 55 is set sufficiently small. Therefore,
Gaseous helium is introduced into the helium filled container 23 of the permanent current switch 22. Then, the switch side superconducting coil 2
Since the temperature of No. 4 is about 10 ° K due to gaseous helium, it becomes a normal conduction state and its resistance value R ₂ increases. Therefore, R ₂ smaller R ₁ is large, no current flows to the permanent current switch 22, current will flow in a path (B). Then, this current is gradually increased. When the current value reaches a predetermined value,
The three-way valve 47 of the permanent current switch 22 is switched to introduce liquid helium into the helium filled container 23. Then, the switch-side superconducting coil 24 becomes approximately 7
Since it is cooled to not more than ° K, it becomes a superconducting state and its resistance value R ₂ becomes zero. Then, R ₁ is a finite value, R ₂
Is zero, a current flows through the switch-side superconducting coil 24, and no power supply flows to the external power supply 55 side. That is, the current flows through the path (A). Therefore, when the circuit switches 56, 56 are cut off, a permanent current flows through the path (A). In this state, the external power supply 55 becomes unnecessary and the superconducting electromagnet 5
9 can be operated in permanent current mode. In the permanent current switch 22 of the present embodiment, the switch-side superconducting coil is introduced by introducing either liquid helium or gaseous helium into the helium filled container 23 by switching the three-way valve 47 of the permanent current switch 22. 24 can be switched between superconducting and normal conducting. Therefore, based on the above principle, the superconducting electromagnet 59 can be operated in the permanent current mode using the permanent current switch 22. That is, unlike a conventional permanent current switch which switches between superconducting and normal conducting by immersing a switch-side superconducting coil in a cryostat filled with liquid helium and heating it with a heater, Since the conduction state of the switch-side superconducting coil 24 can be switched only in the helium-filled container 23 independently of the cryostat 53, the permanent current switch 22 can be installed outside the cryostat 53. Therefore, maintenance, inspection, maintenance, or replacement of the permanent current switch 22 can be performed more easily than in the conventional case. In this embodiment, since the switch-side superconducting coil 24 is inserted along the inner wall of the container using the tubular helium-filled container 23, the cooling efficiency for the switch-side superconducting coil 24 is extremely high. In addition, the amount of liquid helium used for cooling can be reduced. In this embodiment, as a means for selectively supplying liquid helium or gaseous helium to the helium filled container 23, a three-way valve 47 as shown in FIG.
Although a helium piping system using helium was used, the present invention is not limited to this configuration, and various design changes may be made, such as using a piping system for separately introducing liquid helium and gaseous helium to the helium filled container 23. Can be. Also,
Switch side superconducting coil 24, helium filled container 23,
The material and shape of the vacuum vessel 25 are not limited to those in the present embodiment, and various kinds can be used. As described above in detail, in the current switch for a superconducting electromagnet of the present invention, a container to which either liquid helium or gaseous helium is selectively supplied is provided. Because the switch-side superconducting coil is housed inside, the conduction state of the switch-side superconducting coil can be switched to either superconducting or normal conducting with only the container independently of the cryostat. Can operate in permanent current mode. Therefore, the current switch for the superconducting electromagnet can be installed outside the cryostat filled with liquid helium, so that maintenance, inspection, maintenance, or replacement can be easily performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a permanent current switch according to an embodiment of the present invention. FIG. 2 is a diagram showing a helium piping system of the permanent current switch. FIG. 3 is a diagram showing one installation example of the permanent current switch. FIG. 4 is a diagram showing the principle of a general permanent current switch. FIG. 5 is a diagram showing a basic configuration of a conventional permanent current switch. FIG. 6 is a diagram showing a specific example of a conventional permanent current switch. [Description of Signs] 22 Permanent current switch (current switch for superconducting electromagnet) 23 Helium filled container (container) 24 Switch side superconducting coil 25 Vacuum container 53 Cryostat 54 Electromagnet side superconducting coil (superconducting coil for generating magnetic field) 55 External power supply (power supply) 59 Superconducting electromagnet

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 39/20 ZAA H01F 6/00 ZAA

Claims (1)

(57) Claims: 1. A current switch for a superconducting electromagnet for interrupting a permanent current of a magnetic field generating superconducting coil housed in a cryostat , wherein a container provided outside the cryostat is provided. , Housed in the container, and in parallel with the magnetic field generating superconducting coil.
A switch-side superconducting coil connected in a row, and selectively supplying either liquid helium or gaseous helium to the container, thereby superconducting or constantly changing the conduction state of the switch-side superconducting coil. Conduction
A current switch for a superconducting electromagnet, characterized by switching to any direction.