JPS622677A - Superconductor device - Google Patents

Abstract

PURPOSE:To prevent the increase in amount of evaporation of liquid helium due to leaking, by attaching a heater to the flange of a vacuum container, and heating the flange and an O ring with said heater. CONSTITUTION:A heater 14 is formed as follows: a heater wire comprising Nichrom wire and the like is attached to a heater plate 15 made of copper and the like, which is molded in conformity with the outer surfaces of a vacuum container 2 and a flange 12 of the vacuum container and has excellent heat conductivity; and the wire 16 is surrounded by a heat insulating material 17 such as glass film. When liquid helium is supplied to a liquid helium container and a helium-gas recovering pipe 10 is excessively cooled, a flange 11 of the liquid helium container 11, the flange 12 of the vacuum container 12 and an O ring are cooled by heat conduction. This fact is detected by a temperature sensor 18, and the heater 14 is turned ON by a temperature controller 19. Thus, the O ring 13 is heated before it looses elasticity, and sealing performance is not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to prevention of overcooling of a vacuum seal portion of a superconducting device.

[Technical background of the invention and its problems]

A superconducting coil is placed in a liquid helicomb and has zero electrical resistance, allowing a large current to flow and a high magnetic field to be obtained.It can also be operated in persistent current mode, which is useful for nuclear fusion, MR, etc.
It has been widely used for I (nuclear magnetic resonance imaging diagnosis) and the like. Liquid helium has a very low latent heat of vaporization. Therefore, the liquid helium container is installed inside a vacuum container (==) to suppress the heat intrusion due to convection.Also, to prevent radiation, a liquid nitrogen shield is installed between the vacuum container and the liquid helium container, and to prevent radiation, a liquid nitrogen shield is installed between the vacuum container and the liquid helium container, A material with a small diameter is used to support the space between each container, suppressing the total heat intrusion.

The overall structure will be explained based on an example of a conventional superconducting device shown in FIG. 1 is a superconducting device, and 2 is a vacuum container made of stainless steel or the like for suppressing heat intrusion due to convection. Reference numeral 3 denotes a liquid nitrogen container made of stainless steel or the like, in which liquid nitrogen 4 is stored and used as a liquid nitrogen shield to suppress intrusion heat due to radiation and radiation. Further, a multilayer heat insulating material (not shown) is provided around the outer periphery of the liquid nitrogen container 3 to reduce radiant heat.

Reference numeral 5 denotes a liquid helium container made of stainless steel or the like, in which liquid helium 6 is stored and a superconducting coil 7 is provided. Reference numeral 8 denotes a heat insulating support made of epoxy resin or the like having low thermal conductivity and supporting between the containers. 9 is a liquid helium injection port, and 10 is a gas helium recovery pipe for recovering evaporated helium. 11 is a liquid helium container flange, 1
Reference numeral 2 denotes a vacuum vessel flange, which is attached by bolts (not shown) via O-rings 13 made of Piton or the like. Further, the liquid helium container 7 flange 11ζ is equipped with a safety valve, a breaker valve, a current lead, etc. (not shown).

When liquid helium 6 is supplied to the liquid helium container 5, a refrigerant transfer pipe called a transfer tube whose outside is vacuum insulated is inserted into the liquid helium injection port 9. However, due to the intrusion heat of the transfer tube itself and liquid feeding loss, it is sent in a partially vaporized state, and it also vaporizes in the liquid helium container, and the amount of gas recovered from the gas helium recovery tube 10 is fixed, taking MRI as an example. The value becomes more than 100 times the normal cut-off time, and the tube becomes supercooled.

By conduction, liquid helium container 7 flange 111 vacuum container flange 12. And Oringue 3 is also in a supercooled state. O-rings 13 made of Viton are used for assembly and cost reasons, but under supercooled conditions they harden and lose elasticity, resulting in poor sealing performance and leakage in the vacuum container. The degree of vacuum in the vacuum container is set to a high degree of vacuum (10 Torr level) where the thermal conduction of residual gas molecules can be ignored, and leakage: The degree of vacuum decreases and the amount of evaporation of liquid helium increases.

[Purpose of the invention]

The present invention enables even if the gas helium recovery pipe becomes supercooled,
O-Ring's objective is to provide a superconducting device that does not become overcooled.

[Summary of the invention]

In order to achieve the above object, in the superconducting device of the present invention, a heater is attached to the flange of the vacuum vessel.

This heater can heat the 7 lunge and O-ring.

[Embodiments of the invention]

Hereinafter, a non-inventive embodiment will be described based on FIG. 1st
In the figure (=, 1 is the superconducting device, 14 is the vacuum vessel 2
A heater wire 16 made of nichrome wire or the like is attached to a heat conductive heater plate 15 made of steel or the like which is formed to fit the outer periphery of the vacuum vessel flange 12, and a heat insulating material 1 such as glass fiber is attached.
This is the heater circled by 7.

Reference numeral 18 denotes a temperature sensor, such as a copper-constantan thermocouple, installed near the heater 14. Is 19 the temperature sensor? Turn on the heater 14 based on the temperature detected from -18.
, a temperature controller that can be turned off. 20 are bolts fixing each flange.

When supplying liquid helium to the liquid helium container, if the gas helium recovery pipe 1O becomes supercooled, the liquid helium container flange 11. The vacuum vessel flange 12 and O-ring 13 are getting cold.

The temperature sensor 18 detects this, and the temperature controller 19 turns on the heater 14. By doing this, the O-ring 13 is warmed up before it loses its elasticity, and its sealing performance does not deteriorate.

〔Effect of the invention〕

As described above, according to the present invention, even if the gas helium recovery pipe becomes supercooled, the O-ring is heated by the heater, so it does not lose its elasticity, and the amount of liquid helium evaporated due to leakage increases. will disappear.

[Brief explanation of drawings]

FIG. 1 is a sectional view of essential parts of a superconducting device according to an embodiment of the invention, and FIG. 2 is a sectional view of a conventional superconducting device. 2... Vacuum container 3... Liquid nitrogen container 4...
Liquid nitrogen 5...Liquid helicum container 6...Liquid helium 7...Superconducting coil 8...Insulating support
9... Liquid helium inlet 10... Gas helium recovery pipe 11... Liquid helium container flange 12... Vacuum container flange 13... O-ring 1
4... Heater 15... Heater plate 16.
... Heater wire 17 ... Peng Netsusho 18 ... Temperature sensor 19 ... Temperature controller representative Patent attorney Noriyuki Chika (and 1 other person) Figure 2

Claims (1)

[Claims] A superconducting device comprising a vacuum container, a liquid helium container therein, and a superconducting coil, characterized in that a heater is attached to a vacuum container flange near a helium gas recovery tube coming out of the liquid helium container.