JPS6161713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current supply device for supplying current to superconducting equipment such as a superconducting magnet housed in a cryostat.

Conventional current supply devices for superconducting equipment have power leads made of copper pipes, and are configured to flow refrigerant gas such as helium gas, which is used as a cryostat refrigerant, into the copper pipes during excitation and demagnetization of the superconducting magnet. Ta. With such a configuration, it is possible to prevent the heat generated by the copper pipe from entering the cryostat during excitation and demagnetization of the superconducting magnet, but when the superconducting magnet inside the cryostat is in operation, The heat from the cryostat entered the cryostat and caused the refrigerant inside the cryostat to evaporate unnecessarily. As a means to prevent this heat intrusion, (1) constantly circulating refrigerant through the copper pipe of the power lead, (2) making the copper pipe of the power lead thinner,
It is possible that However, constantly circulating an expensive refrigerant such as helium through the copper pipes poses a cost problem. Furthermore, if the copper pipe of the power lead is made thinner, heat generation increases during excitation and demagnetization of the superconducting magnet, and there is a risk of burnout.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a current supply device for superconducting equipment in which the amount of heat intrusion into a cryostat is extremely small.

In the present invention, a current supply device for superconducting equipment is composed of an outer tube made of a material with low thermal conductivity and a power lead for supplying excitation current, and the low temperature side of the power lead is made of a material with low electrical conductivity and is made of a superconducting wire. The cryostat is composed of a wrapped superconducting part, and when the superconducting equipment is excited and demagnetized, the refrigerant in the cryostat is circulated in the outer tube in advance to cool the superconducting part of the power lead until it reaches a critical temperature. This is designed to reduce heat intrusion into the tattoo from the outside.

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

The figure shows a state in which a current supply device 1 for superconducting equipment according to the present invention is used in a cryostat 2.
The cryostat 2 is composed of an inner tank 3 and an outer tank 4, and a superconducting device 5 such as a superconducting magnet is cooled by liquid helium 6 and housed in the inner tank 3. A space 7 between the inner tank 3 and the outer tank 4 is made into a vacuum for heat insulation, and a shield plate 8 is placed in this space 7, and a shield pipe 9 through which liquid nitrogen flows is attached to the shield plate 8. This increases the heat shielding effect. A shield supply pipe 10 for supplying liquid nitrogen to be circulated through the shield pipe 9 and a shield discharge pipe 11 for discharging the liquid nitrogen circulated through the shield pipe 9 are connected to the shield pipe 9 and provided to penetrate the outer tank 4. Further, a supply pipe 12 for supplying liquid helium to the inner tank 3 is installed so as to penetrate from the inner tank 3 to the outer tank 4. A current supply device 1 for superconducting equipment that allows current to flow during excitation and demagnetization of superconducting equipment 5 includes:
In order to reduce the amount of heat intrusion into the superconducting equipment 5 as much as possible,
The current supply device 1 for superconducting equipment is connected to the superconducting equipment 5 by making a detour around the inner tank 3 to increase the distance from the outside of the cryostat 2. The current supply device 1 for superconducting equipment is comprised of an outer tube 12 made of a material with low thermal conductivity, such as stainless steel, and a power lead 13 inserted into the outer tube 12.
The outer tube 12 is the outer tank 4 and inner tank 3 of the cryostat 2.
It is arranged to connect the The power lead 13 formed of a copper pipe is divided into four parts, and from the inner tank 3 side of the power lead 13 there is a lead part 14 made of copper (OFHC etc.) with high electrical conductivity, compared to copper (OFHC etc.). It consists of a superconducting part 17 in which a superconducting wire 16 is wound around a material 15 such as Cypronickel, which has a low thermal conductivity, and a normal-conducting part 18 in which the room temperature side is made of a normal-conducting material. This normal conducting part 18
is divided into two parts, and the superconducting part side lead 19 is made of a material such as copper (OFHC etc.) which has a higher electrical conductivity than the general current supply material such as phosphorus deoxidized copper used for the other side, the normal temperature side lead 20. It is formed. The power lead 13 configured as described above is led out of the cryostat 2. The part of the normal conducting part 18 of the power lead 13 drawn out to the outside of the cryostat 2 and the outer tube 12 are connected to an electrically insulating material 2 such as fiber reinforced plastic (FRP) material.
Step 1: electrically insulate and seal to maintain airtightness. In addition, a heater 21 is installed in the inner tank 3 and the outer pipe 1
Liquid helium 6 in the inner tank 3 is vaporized by the heat generated by the heater 22, and this helium gas flows through the outer tube 12 to cool the power lead 13. The outlet 23 for releasing this helium gas to the outside is the outer tank 4 of the outer tube 13.
It is located outside of the A germanium thermometer 25 is provided near the connection point between the lead wire 24 of the heater 22 and the superconducting portion 17 and the normal conductive portion 18 of the power lead 13. Although this lead wire 26 is not shown, it connects the inner tank 3 and the outer tank 4. It penetrates and is directly drawn out to the outside of the cryostat 2. In addition, a good thermal conductor 28 having a penetration 27 and having a high thermal conductivity such as aluminum is provided in a part of the normal temperature side lead 20 of the normal conductive part 18 of the power lead 13 so as to be in contact with the outer tube 12. A liquid nitrogen reservoir 29 is provided at the location where the good thermal conductor 28 is provided, and the thermal anchor 30 is installed.
This liquid nitrogen is led from shield piping 9. Note that the lead portion 14 of the power lead 13
and superconducting equipment 5 are connected via a bus bar 31.

Next, the operation will be explained.

A case in which the superconducting device 5 is excited will be explained. First, the helium gas outlet 23 provided in the outer tube 12 of the current supply device 1 is closed, and the heater 22 provided in the inner tank 3 is caused to generate heat. This heater 22
Due to the heat generated, the liquid helium 6 in the inner tank 3 is vaporized, and helium gas flows into the outer pipe 12 and fills it.
The power lead 13 is thereby cooled. A germanium thermometer 25 installed near the superconducting part 17 of the power lead 13 measures the temperature at which the superconducting part 17 becomes superconducting like the superconducting wire 16 (usually 6K).
~7K or less), then apply current to the power lead 13. The normal temperature side lead 20 of the normal conductive part 18 uses a general current supply material such as phosphorus-deoxidized copper, so it generates heat, but since the thermal anchor 30 is installed, part of this heat generation is absorbed. . Furthermore, since the superconducting part side lead 19 of the normal conducting part 18 is formed of a material with high electrical conductivity, the other part of the heat generated in the normal temperature side lead 20 of the normal conducting part 18 is transferred to the superconducting part of the normal conducting part 18. The heat is conducted to the superconducting lead 19, but the superconducting lead 19 generates almost no heat, so the heat is absorbed by the helium gas filling the outer tube 12. Therefore, the heat generated in the normal conducting part 18 can be prevented from being conducted to the superconducting part 17, so the superconducting wire 16 of the superconducting part 17 can maintain a stable superconducting state, and the superconducting wire 16 in the superconducting device 5 can be kept in a stable state. Current can be stably supplied to the superconducting equipment 5 through the power lead 13 without allowing heat to enter the inner tank 3.

Next, a case will be described in which the superconducting device 5 enters the operating state in the superconducting mode.

The heater 22 in the inner tank 3 is turned off to stop generating heat, and the helium gas outlet 23 of the outer tube 12 is opened. Heat outside the cryostat 2 attempts to enter the cryostat 2 through the outer tube 12 and the power lead 13. The outer tube 12 is made of a material with low thermal conductivity such as stainless steel, and a thermal anchor 30 is installed in the middle, so that no heat is conducted through the outer tube 12 and enters the inner tank 3. Regarding the power lead 13, a considerable amount of heat enters through the normal temperature side lead 20 of the normal conductive portion 18, but a considerable amount of heat is absorbed by the thermal anchor 30. In actual temperature measurements, when the temperature at the inlet of the power lead 13 was 300K, the temperature was reduced to 80K by the thermal anchor 30. In this way, heat entering from the outside is conducted to the superconducting portion 17. This superconducting portion 17 has a structure in which a superconducting wire 16 is wound around a material 15 such as Cypronickel having low electrical conductivity. Superconducting materials generally have low thermal conductivity. Therefore, the heat that has penetrated to the superconducting part 17 is absorbed by the helium gas flowing into the outer tube 12 due to the outflow of helium gas due to natural evaporation of the liquid helium 6 in the inner tank 3, so that the heat from the outside reaches up to the inner tank 3. cannot be invaded.

It should be noted that although the explanation was made only during the excitation of the superconducting device 5,
The same applies during demagnetization.

As is clear from the above explanation, when the current supply device according to the present invention is used, there is less heat generated in the power lead during excitation and demagnetization of superconducting equipment, and heat intrusion from the outside occurs while the superconducting equipment is operating in superconducting mode. The cryostat can be operated efficiently.

[Brief explanation of the drawing]

The drawing is a sectional view showing a cryostat equipped with a current supply device for superconducting equipment according to the present invention. 1... Current supply device for superconducting equipment, 2... Cryostat, 5... Superconducting equipment, 6... Liquid helium (refrigerant), 12... Outer tube, 13... Power lead, 15... Thermal conductivity Small materials, 16...
...Superconducting wire, 17...Superconducting part, 18...Normal conducting part, 19...Superconducting part side lead of normal conducting part, 20
...The normal temperature side lead of the normal conductive part.

Claims (1)

[Claims] 1. In a current supply device for superconducting equipment that is equipped with a power lead that supplies excitation current from the room temperature side to the superconducting equipment immersed in an inner tank containing a refrigerant in a cryostat, the low temperature side of the power lead is made of a superconductor. The normal temperature side of the power lead is formed of a superconducting part, and the normal temperature side of the power lead is formed of a normal conducting part made of a normal conductor, and the power lead is covered with an outer tube made of a material with low thermal conductivity, and the power lead is connected to the normal temperature side from the inner tank. During excitation and demagnetization of the superconducting equipment, the refrigerant in the inner tank is evaporated in advance by a heater provided in the inner tank and forced to flow into the outer tube to make the superconducting part of the power lead critical. A current supply device for a superconducting device, characterized in that the superconducting device is cooled to a certain temperature, and when the superconducting device is in operation, the naturally evaporated refrigerant in the inner tank is circulated through the outer tube to cool the superconducting device.