JPH02239605A - Cryostat - Google Patents

Abstract

PURPOSE:To reduce the intrusion of heat to a cryogenic refrigerant tank largely by installing a communicating hole closed when a power lead is retreated and a valve body capable of being abutted against and sealing the periphery of the communicating hole to the cryogenic refrigerant tank. CONSTITUTION:When power leads 5A, 5B are engaged with connectors 10A, 10B in order to complete the permanent current mode of a superconducting magnet 3, a valve body 19 is separated from the peripheral section of the communicating hole 22 of a cryogenic refrigerant tank 1 and the communicating hole 22 is opened, the gas of a cryogenic refriderant is flowed into a piping 4 for the power leads from the inside of the cryogenic refrigerant tank 1, and the power leads 5A, 5B are cooled. When the permanent current mode of the superconducting magnet 3 is completed and the power leads 5A, 5B are detached from the connectors 10A, 10B, the valve body 19 is abutted against and seals the peripheral section of the communicating hole 22 of the cryogenic refrigerant tank 1 and the communicating hole 22 is closed, the inflow of the cryogenic refrigerant gas from the inside of the cryogenic refrigerant tank 1 is stopped, and the inside of the piping 4 for the power leads is closed. The cryogenic refrigerant gas in the piping 4 is removed, and the inside of the piping is held under a vacuum or low pressure. Accordingly, heat loss due to a convection is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cryostat characterized by a detachable energization mechanism for energizing a superconducting magnet kept at an extremely low temperature by a coolant such as liquid helium.

(Prior Art) Conventionally, in a cryostat equipped with a removable magnet energizing mechanism, as shown in FIG.
A power lead piping 4 is provided to connect the cryogenic refrigerant tank l and the vacuum chamber 2 through the heat shield plate, and the cryogenic refrigerant tank l is installed in the pipe 4 and covered with a heat shield plate. A pair of power leads 5A and 5B are provided that can be inserted into and removed from the cryogenic refrigerant tank 1, and the power leads 5A and
5B is provided with a pair of detachable connectors IOA and IOB, a superconducting magnet 3 is immersed in cryogenic refrigerant stored in a cryogenic refrigerant tank 1, and the connectors IOA and JOB are connected to the superconducting magnet 3, respectively. Lead wires 12A, 12
B is connected via persistent current switch l1, and after connecting power leads 5A and 5B to connectors IOA and IOB and turning off persistent current switch 11, power 6[27
Power leads 5A, 5B and lead wire 12AS 1
2B to the superconducting magnet 3, and after reaching a predetermined current, the persistent current switch 11 is closed and the power supply current is set to zero to complete the persistent current mode. After that, the power leads 5A and 5B are connected to the connectors. I am trying to separate it from IOA and 10B. Also, the connector IOA. ．． After being separated from the IOB, the power leads 5A and 5B are either left in the power lead piping 4 as shown in FIG. 6, or are completely removed from the power lead piping 4 as shown in FIG. ．． [Problem to be Solved by the Invention] However, the gas of the cryogenic refrigerant evaporated in the cryogenic refrigerant tank l flows into the power lead through the gap existing between the connectors IOA, IOB and the cryogenic refrigerant tank l. Piping 4
Since a gas atmosphere of the cryogenic refrigerant is formed within the superconducting magnet 3 and convection of the cryogenic refrigerant gas occurs, the former method shown in FIG. , external heat enters from the outside of the vacuum chamber 2 (normal temperature part) by heat conduction via the power leads 5A and 5B, and this is transferred to the cryogenic refrigerant tank 1 by convection in the power lead piping 4, resulting in heat loss. In addition, there was also heat loss due to radiant heat that could not be blocked by the heat shield plate.
There was a drawback that the stored cryogenic refrigerant evaporated and the retention time became shorter. In addition, in the latter method shown in FIG. 7, it is necessary to arrange a convection prevention plate in the power lead piping 4, and it is troublesome to take the power leads 5A and 5B in and out, insert them, and open and close the opening. The drawback was that it was difficult to automate the energization work.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned problem in a type of cryostrist in which the power lead is kept in the pipe after the connector is disconnected, and its purpose is to significantly reduce heat intrusion into the cryogenic refrigerant tank. do.

[Means for solving the problem]

As shown in FIGS. 1 to 4, the cryostat of the present invention has a pair of connectors IO and
A, IOB is provided, and the connector IOA is installed in the power lead piping 4 that connects the vacuum chamber 2 and the cryogenic refrigerant tank 1.
, a pair of removable power leads 5A and 5B are provided on the IOB, and a vacuum pump 14 connected to the inside of the power lead piping 4 or absorption tubes 15a and 15b filled with gas adsorbent is provided, and a connector is provided. IOA, 10B
The cryogenic refrigerant tank l is provided with a communication hole 22 that communicates with the power lead piping 4, and the communication hole 22 is connected to the power lead 5A, A valve body 19 that can be biased toward the communication hole 22 and sealed by contacting with the periphery of the communication hole 22 so as to close when the valve 5B retreats.
vff! k, and this configuration achieves the above-mentioned goal.

[For production]

When the power leads 5A and 5B are engaged with the connectors IOA and IOB to complete the persistent current mode of the superconducting magnet 3, the valve body l9 separates from the peripheral edge of the communication hole 22 of the cryogenic refrigerant tank l, and the communication hole 22 closes. The cryogenic refrigerant gas flows from the cryogenic refrigerant tank 1 into the power lead piping 4, and the power leads 5A and 5B are cooled. When the power leads 5A and 5B are disconnected from the connectors IOA and IOB after the persistent current mode of the superconducting magnet 3 is completed, the valve body 19 contacts and seals the peripheral edge of the communication hole 22 of the cryogenic refrigerant tank l, and the communication hole is closed. 22 is closed, the inflow of cryogenic refrigerant gas from inside the cryogenic refrigerant tank l is stopped, and the inside of the power lead piping 4 is sealed. Next, the vacuum pump l4 or absorption tube 15a or 1
The gas adsorbent in 5b removes the cryogenic refrigerant gas in the power lead pipe 4, and maintains the power lead pipe 4 at a vacuum or low pressure, eliminating heat loss due to convection.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In the figure, reference numeral 1 denotes a cryogenic refrigerant tank that stores a cryogenic refrigerant (for example, liquid helium), which is placed in a vacuum tank 2 and covered with a heat shield plate (not shown) to prevent radiant heat to the cryogenic refrigerant tank 1. There is.

A superconducting magnet 3 is immersed in the cryogenic refrigerant stored in the cryogenic refrigerant tank 1 .

Reference numeral 4 denotes a power lead pipe that connects the cryogenic refrigerant tank 1 and the vacuum tank 2, and is provided to penetrate the vacuum tank 2 and the heat shield plate.

5A and 5B are a pair of power leads, and the power lead 5
The upper and lower ends of A and 5B are connected via connecting members 6 and 7, respectively, the lower ends are inserted into the power lead piping 4, and the upper ends are arranged outside the vacuum chamber 2,
It can be integrally inserted into and removed from the cryogenic refrigerant tank l by a moving device (not shown).

Conductors 8A and 8B for energizing the superconducting magnet 3 are housed inside each of the power leads 5A and 5B, and a removable portion 9A connected to the conductors 8A and 8B is provided at the tip of each of the power leads 5A and 5B.
9B is provided.

10A and IOB are a pair of connectors to which the power leads 5A and 5B can be attached and detached, and are connected to the cryogenic refrigerant tank so as to face inside the power lead piping 4 so as not to create a gap between them and the cryogenic refrigerant tank l. It is provided in l.

These connectors IOA and IOB have one end connected to a superconducting magnet 3.
The other ends of the lead wires 12A and 12B are connected to each other, and the lead wires 12A and 12B are connected to each other via the persistent current switch 11 at an intermediate portion.

13 is an elastic seal cylinder such as a bellows, which is connected to the periphery of the plate-shaped upper connecting member 6 and the periphery of the through hole 9 formed in the upper part of the vacuum chamber 2 so as to face the inside of the power lead piping 4. It is located between the department. The inside of the power lead piping 4 is kept airtight by this elastic seal cylinder l3 regardless of the movement of the power leads 5A, 5B.

Reference numeral 14 denotes a vacuum pump, which is connected to the inside of the power lead pipe 4 via the upper connecting member 6 and a connecting pipe 15.

It should be noted that, as shown in FIG. 4, in place of the vacuum pump 14, an absorption pipe filled with a gas adsorbent such as activated carbon may be connected to the connecting pipe 15 with almost the same effect. Absorption pipe 15 to connection pipe 15
The reason why a and 15b are branched and connected is to enable the gas adsorbent in the absorption tube to be kept activated at all times. A heater 16 for regeneration is attached, and switching valves l7 and l8 are installed before and after the adsorbent filling part so that the absorption pipe 15a or 15b on the regeneration side can be disconnected from the connecting pipe l5.
is provided.

Reference numeral 19 denotes a valve body, which is movably fitted into a valve box 20 attached to the inner surface of the upper part of the cryogenic refrigerant tank 1. The valve body 19 and the valve box 20
It is urged toward the piping 4 side by a compression spring 21 interposed between the end wall and the end wall on the side opposite to the piping 4.

Reference numerals 22 and 23 are communicating holes that communicate the inside of the cryogenic refrigerant tank l and the inside of the pipe 4. The communicating hole 22 is opened at the upper part of the cryogenic refrigerant tank l so as to be opened and closed by the valve body 19, and the communicating hole 23 is connected to the inside of the cryogenic refrigerant tank l. It is provided on the side wall of box 20.

Reference numeral 24 denotes a sealing member such as an O-ring, which is attached to one of the valve bodies 19 and the peripheral edge of the communication hole 22 of the cryogenic refrigerant tank l so as to be able to contact and seal between the valve body 19 and the peripheral edge of the communication hole 22 of the cryogenic refrigerant tank l.

Reference numeral 25 denotes a passive iron that passes through the through hole 22 provided in a protruding manner in the valve body l9. Reference numeral 26 denotes an actuating piece protruding from the cryogenic refrigerant tank l side of the lower connecting member 7, which is provided so as to push down the tip of the driven rod 25 when the power leads 5A and 5B move forward, and to separate from the driven rod 25 when the power leads 5A and 5B move backward. There is.

In the above configuration, when completing the persistent current mode of the superconducting magnet 3, the power leads 5A, 5 are
B toward the cryogenic refrigerant tank l and move it forward to remove the attachment/detachment part 9 at the tip.
Connectoku IOA with A and 9B installed on top of cryogenic refrigerant tank 1
, IOB and the conductors 8A and 8B in the power leads 5A and 5B are connected to the lead wires 12A and 12B, and then the superconducting magnet 3 is energized by the power supply 27 connected to the conductors 8A and 8B to reach a predetermined current. After that, the persistent current switch 11
@Close and make the power supply current zero. After that, by reversing the above procedure, attach/detach the power leads 5A, 5B to the detachable parts 9A,
Disconnect 9B from connectors IOA and IOB.

When the power leads 5A, 5B are engaged with the connectors IOA, 10B to complete the persistent current mode of the superconducting magnet 3, the actuating piece 26 provided at the tip of the power leads 5A, 5B via the lower connecting member 7 is connected to the passive rod. 25 is pushed by overcoming the biased spring force, and the valve body l9 is pushed down toward the anti-power lead pipe 4 side, so that the valve body l9 is separated from the peripheral edge of the communication hole 22 of the cryogenic refrigerant tank l, and the communication hole 22 is pushed down. When opened, the inside of the power lead piping 4 and the inside of the valve box 20 are communicated. Since the inside of the cryogenic refrigerant tank 1 is in communication with the inside of the valve box 20 through the communication hole 23, the cryogenic refrigerant gas in the cryogenic refrigerant tank 1 passes through the inside of the valve box 20 and enters the power lead piping 4. Since the cryogenic refrigerant gas flows in, the inside of the power lead pipe 4 and the power leads 5A and 5B are cooled by this cryogenic refrigerant gas.

Also, after completing the persistent current mode of superconducting magnet 3,
The power leads 5A and 5B are moved back, and the valve body 19 is automatically returned to the power lead pipe 4 side by the biased spring force and is applied to the periphery of the communication hole 22 of the cryogenic refrigerant tank 1 via the seal member 24. The communication hole 22 is closed and the communication between the inside of the power lead piping 4 and the inside of the valve box 20 is cut off.
The inside of the power lead piping 4 is kept airtight. Thereafter, after the communication hole 22 is closed, the inside of the power lead pipe 4 is evacuated by the vacuum pump 14 via the connecting pipe 15, and the cryogenic refrigerant gas inside the power lead pipe 4 is removed and maintained in a vacuum. Therefore, heat loss due to convection is eliminated. Or, after the communication hole 22 is closed, the upstream switching valves l7 and l8 of the absorption pipe 15a (or 15b) on the side to be used
is opened, and the cryogenic refrigerant gas in the power lead piping is removed and depressurized by the gas adsorbent in the absorption tube 15a (or 15b), thereby reducing heat loss due to convection. [Effects of the Invention] As described above, according to the present invention, in a cryostat of a type in which the power lead is retained in the power lead piping after the connector is disconnected, the valve mechanism causes the power lead piping to be closed at the same time as the connector is disconnected. Keep it airtight,
In addition, since the cryogenic refrigerant gas in the power lead piping can be removed by evacuation or gas adsorption to maintain a vacuum or low pressure, convection does not occur or is difficult to occur in the power lead piping. Therefore, it is possible to significantly reduce heat invasion and reduce evaporation loss of the cryogenic refrigerant stored in the cryogenic refrigerant tank, while retaining the advantage that it is easy to automate the process of energizing the superconducting magnet. In addition, it can be easily applied to existing cryostat.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention, and FIG.
3 is an explanatory view of the operation, FIG. 4 is a schematic sectional view showing another embodiment of the present invention, FIG. 5 is a schematic sectional view showing a conventional example, and FIGS. 6 and 7 are FIG. 7 is a conceptual diagram showing a second method for disconnecting the power lead connector. ■... Cryogenic refrigerant tank, 2... Vacuum tank,
3...Superconducting magnet, 4...Power lead piping, 5A, 5B...Power lead, 6,
7... Connecting member, 8A, 8B... Conductor, 9A, 9B old... Detachable part, 10AS IOB...
... Connector, l1 ... Persistent current switch,
12AS 12B・Old・Lead wire, l3・・・・・・
Stretchable seal cylinder, l4...Vacuum pump, l5...
...Connection piping, 15a, 15b...Absorption pipe, l6...Heater, l7, l8...Switching valve, l9...Valve body, 20...Bent box,
2l...Compression spring, 22, 23...Communication hole, 24...Seal member, 25...
Passive rod, 26... Actuating piece, 27...
·power supply.

Claims (2)

[Claims] (1) A pair of connectors are provided in the cryogenic refrigerant tank in the vacuum chamber, and a pair of power leads that can be attached and detached from the connector in forward and backward movement are installed in the power lead piping that connects the vacuum chamber and the cryogenic refrigerant tank. In a cryostat equipped with a power lead, a vacuum pump connected to the inside of the power lead piping is provided, and the connector is installed so that there is no gap between the power lead and the cryogenic refrigerant tank, and the power lead is connected to the cryogenic refrigerant tank. A communication hole that communicates with the inside of the power lead, and a valve body that can be biased toward the communication hole and sealed against the periphery of the communication hole so that the communication hole is closed when the power lead is retreated. Characteristic cryostat. (2) The cryostat according to claim 1, characterized in that, in place of the vacuum pump, an absorption tube filled with a gas adsorbent is connected to the inside of the power lead piping.