JPS6286704A - Permanent current switch for superconductive magnet - Google Patents

Abstract

PURPOSE:To synchronize the operation of the switch, to be used for permanent current mode, with the operation of the switch to be used for a protective circuit without using a special means by a method wherein the superconductive wire for the permanent current mode switch of a magnet, the superconductive wire for the permanent current switch of a protective circuit, and a heater wire are closely arranged to each other, and they are formed in one body by applying an insulating material thereon. CONSTITUTION:A superconductive wire 6 of a permanent current switch 10 is series-connected to a magnetic coil 1, and one end of the other superconductive wire 7 is connected to one end side of the coil, 1, and the other end of the conducting wire 7 is connected to the protective resistor 3 fastened to the other end side of said coil. Besides, when a heater wire 8 is connected to a power source, the superconductive wire 6 and the heater wire 8 are turned to the switch for a permanent current mode, and the superconductive wire 7 and the heater wire 8 are turned to the switch for the protective circuit. To be more precise, when the heater power source is turned ON and the superconductive wires 6 and 7, which are cooled before excitation, are heated up simultaneously, both wire materials are turned to the normal conductive state, and resistance r1 and r2 are generated on both of them. Also, when the heater power source is turned OFF, the resistance of the wire materials 7 and 8 are turned OFF, the resistance of the wire material 7 and 8 are turned to zero.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention compactly integrates the persistent current mode switch of a superconducting magnet and the persistent current switch inserted into the protection circuit of the magnet, and uses one heater power supply. This invention relates to persistent current switches that can be operated simultaneously.

[Conventional technology]

In superconducting magnets, it has been considered to connect a low resistance in parallel with the magnet coil in order to protect the coil during quench (transition from superconductivity to normal conductivity) and to protect the persistent current switch.

Figure 2 shows the equivalent circuit when the coil is excited. In the figure, numeral 1 is a magnet coil, 2 is a persistent current switch (hereinafter referred to as p, c, and s), and 3 is a protective resistor.

In this circuit, when a quench occurs in the coil and the P, C, and S parts and abnormal voltage is generated, current is shunted to the protective resistor 3 with a low resistance value, and the energy stored in the coil is consumed by the protective resistor 3. However, during excitation, Joule loss occurs in the protection circuit in which the protection resistor 3 is inserted, and the heat increases the amount of evaporation of the cryogen (generally liquid helium) that cools the magnet. As shown in FIG. 3, the inventors connected the second P, C, and S4 in series to the protective resistor 3 of the protection circuit, and (-) P, C,
By keeping S4 in a normal conducting state during excitation and in a superconducting state after excitation, the protection circuit during excitation is made high resistance to suppress Joule loss and cryogen evaporation, while in persistent current mode, the equivalent value shown in Figure 4 is maintained. We proposed a technology to bring out the intended protection function of the protective resistor 3 by changing the circuit.

[Problem that the invention seeks to solve]

However, according to method 4, the magnet device has two persistent current switches, and if it is attempted to insert the two switches separately into the magnet, the following three problems arise.

(1) A persistent current switch is generally constructed by combining a superconducting wire and a heater that heats it, so if the two switches are separate, two heater power supplies are required.

(2) In order to operate the two switches at the same time, it is necessary to devise a way to synchronize the power supplies of the two heaters.

(3) It is necessary to secure storage space for the two switches.

[Means for solving problems]

Therefore, the present invention solves the above three problems by integrating two persistent current switches so that they can be operated simultaneously by one heater power source. Specifically, superconducting wire for persistent current mode switch of magnet,
The superconducting wire for the second persistent current switch and one heater wire connected in series to the protective resistor of the protection circuit connected in parallel to the magnet coil are placed close to each other and are integrally coated with an insulating material having good low temperature characteristics. Both ends of the wire are drawn out from the insulating material layer so that the heater and the heater power source can be shared.

Furthermore, by integrating two switches, it is possible to install the switch in a small space at the same time.

〔Example〕

FIG. 1 shows a specific embodiment of this invention.

Reference numeral 5 in the figure is an insulating core, on which two superconducting wires 6.
7 are spirally wound in parallel. Moreover, one heater wire 8 is preferably folded in half from the middle part and spirally wound on these wires, and the outer periphery of the spirally wound part is further wrapped around the wire 6.7.8 except for both ends. , is coated with an insulating material 9 that can withstand low temperatures, such as epoxy resin, and is integrated as a whole. The layer of insulating material 9 is applied to a thickness that provides sufficient thermal insulation between the spirally wound portion of the heater wire 8 and the cryogen that cools the switch.

One electromotive conductor 6 of the persistent current switch 1o configured as above is connected in parallel to the magnet coil 1, and the other electromotive conductor 7 has one end connected to one end of the coil 1 and the other end to the other end of the same coil. When the heater wires 8 are connected to the protective resistors 3 connected to the sides, and the heater wires 8 are connected to a single power source (not shown), the superconducting wires 6 and the heater wires 8 are connected to the persistent current mode switch,
The superconducting wire 7 and the heater wire 8 serve as a switch for a protection circuit, and the equivalent circuit shown in FIG. 3 is constructed during excitation, while the equivalent circuit shown in FIG. 4 is constructed during persistent current mode. In other words, the heater power is turned off.
When the superconducting wires 6.7 which have been cooled before excitation are heated at the same time in N, both wires become normal conductive and a resistance of rIsr2 as shown in FIG. 3 is generated in both of them, resulting in the circuit configuration shown in the same figure. Further, when the heater power is turned off, the resistance of the wire 7.8 becomes 0, resulting in the circuit configuration shown in FIG.

Note that in the illustrated switch, each wire was wound on an insulating core in order to facilitate manufacturing, but the wire 6. The core 8 can be omitted and held only by the insulating material 9.

Further, the arrangement of these wires may be other than a spiral arrangement. In particular, since there is a risk that the heater wire 8 may be induced by the current flowing through the superconducting wire 6.7, it may be folded in half and wrapped as described above, or the wire 6.7 may be wrapped around the wire 6.7 by turning it in the longitudinal direction of the switch at both ends. It is desirable to use a non-inductive wiring pattern that runs along the entire circumference. This heater wire 8 is not limited to the outer periphery of the superconducting wire 6.7, but may be placed between the wire rods 6 and 7 or inside.

[Effects] As described above, the persistent current switch of the present invention has a configuration in which two switch wires using superconducting wires are turned on and off by one heater wire, so only one heater power source is required. .

Furthermore, since the two switch wires and one heater wire are integrated into one compact block using an insulating material, the installation space can be reduced.

Furthermore, since two switch wires are heated simultaneously by one heater wire, it is possible to synchronize the operation of the persistent current mode switch and the protection circuit switch without using special means. .

[Brief explanation of drawings]

Fig. 1 is a partially broken front view showing an example of the persistent current switch of the present invention, Fig. 2 is an equivalent circuit when exciting a superconducting magnet using the switch, and Fig. 3 is an equivalent circuit in persistent current mode. The circuit shown in FIG. 4 is an equivalent circuit during excitation of a known superconducting magnet having a protective resistor. 5... Insulating core, 6, 7... Superconducting wire, 8... Heater wire, 9... Insulating material, 10... Persistent current switch patent applicant Sumitomo Electric Industries, Ltd. Agent: Kama 1) Sentence 2 Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] Superconducting wire for persistent current mode switch of magnet,
The superconducting wire for the second persistent current switch and one heater wire connected in series to the protective resistor of the protection circuit connected in parallel to the magnet coil are placed close to each other and are integrally coated with an insulating material having good low temperature characteristics. A persistent current switch for superconducting magnets in which both ends of the wire are drawn out from the insulating material layer.