JPS63217607A - Superconducting magnet - Google Patents

Abstract

PURPOSE:To prevent the generation of thermal oscillation as well as to contrive reduction in the quantity of evaporation of helium by a method wherein a current lead tube and a pressure-releasing tube are connected with a pressure-equalizing tube. CONSTITUTION:Current lead tubes 5a and 5b are connected by pressure-equalizing tubes 11a and 11b. In the piping constituted as above, a hand-operated valves 7a and 7b are closed, another hand-operated valve 9 is opened and a check valve 12 is opened in the normal state (permanent current mode). To be more precise, the evaporated helium gas is gathered in a hand-operated valve 9 by passing through the current lead tubes 5a and 5b and the pressure-equalizing tubes 11a and 11b, it passes through a check valve 12, released into atmospheric air, and the gas pressure at the normal temperature part of the current lead tubes 5a and 5b is made equal to the gas pressure in the helium container 2 by the equalizing tubes 11a and 11b. Accordingly, the gas pressure of the current lead tubes 5a and 5b is made equal in a cryogenic temperature part and the normal temperature part, and the gas is not circulated in the current lead tubes. As a result, the thermal oscillation phenomenon in the current lead tube is removed, the quantity of heat penetrated into the liquid helium is reduced, and the quantity of evaporated helium becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a superconducting magnet used in MHI, magnetic levitation trains, etc.

(Conventional technology) FIG. 3 shows an example of a conventional superconducting magnet.

1 is a vacuum container, and the helium container 2 inside is vacuum-insulated. A coil 3 is contained in the helium container 2,
It is cooled to a cryogenic temperature of about 4 by liquid helium 4. Reference numerals 5a and 5b are current lead tubes that guide current to the coil, and have a structure in which helium gas passes through metal pipes. 1! When the coil is energized from the source 6, the manual valves 7a and 7b are opened to cool the pipe by passing helium gas, and the current lead pipe 5a due to Joule heat generation.
5b is prevented from burning out. 8 is a pressure relief pipe that releases evaporated helium gas to the atmosphere, and 9 is a manual valve.

When energizing the current lead, the manual valve 9 is closed and gas is allowed to flow only through the current lead to cool it. Also, when a persistent current is flowing through the coil, the manual valve 7a.

7b is closed and opened using a manual valve 9 to prevent the internal gas pressure from increasing. 10 is a rupture disc, which is structured to prevent excessive internal pressure from being applied to the helium container 2.

The opening/closing pattern of the manual valve depending on the operation mode of the superconducting magnet is summarized as follows.

Generally, the normal state of a superconducting magnet is the persistent current mode, and this time is the longest than other modes.The resting mode, where no current flows in the coil or current lead, is also the same as the persistent current mode. It has an opening and closing pattern.

That is, the amount of evaporation of liquid helium when 7a and 7b are closed and 9 is open is important, and it is necessary to reduce the amount of evaporation at this time as much as possible.

(Problems to be Solved by the Invention) However, in conventional piping, a thermal oscillation phenomenon occurs, especially when the manual valves 7a and 7b of the current lead pipe are closed, and the amount of evaporation increases. Ta. Thermal oscillation occurs in particularly thin and long cryogenic piping that connects the normal temperature part and the cryogenic part, and the normal temperature part is closed.The cryogenic gas expands its volume in the normal temperature part, and the pressure increases. This phenomenon repeats the cycle of pushing the gas back to the low-temperature area, and as the helium gas circulates inside the pipe, it causes a large amount of heat to enter the liquid helium from the room-temperature area.

Furthermore, if the valves are opened or closed incorrectly, especially if 7a and 7b are left open, air will flow backwards and freeze, resulting in no gas coming out.

An object of the present invention is to provide a superconducting magnet that does not cause thermal oscillation and has a small amount of helium evaporated.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, the current lead pipe and the pressure relief pipe are connected by a pressure equalizing pipe.

(Function) In this way, even if the valve of the current lead tube is closed, the room temperature section of the tube is open, so even if the low temperature He gas expands in the room temperature section, its pressure is released to the atmosphere and thermal No oscillation occurs.

(Example) FIG. 1 is a diagram of a superconducting magnet according to an example of the present invention.

Current lead pipes 5a and 5b are connected by pressure equalizing pipes 11a and 11b.

12 is a check valve.

In the piping configured as described above, in the normal state (persistent current mode), manual valves 7a and 7b are closed, manual valve 9 is open, and check valve 12 is open. That is, the evaporated helium gas passes through the current lead pipes 5a and 5b and the pressure equalization pipes 11a and llb, collects in the manual valve 9, and is discharged to the atmosphere through the check valve 12. In such a state, the gas pressure at the normal temperature portion of the current lead tubes 5a, 5b becomes equal to the gas pressure in the helium container 2 by the pressure equalizing tubes 11a, llb. Therefore, current lead tubes 5a, 5b
The gas pressure is the same in the cryogenic temperature section and the normal temperature section. Therefore, there is no gas circulation within the current lead tube.

The manual valves 7a, 7b, and 9 may be replaced with electromagnetic valves, etc., but by using electromagnetic valves, the valve operations in each operation mode can be automated and facilitated, and there is no erroneous operation, increasing safety.

FIG. 2 also shows another embodiment of the present invention. 5a.

5b, 8, lla, and llb are the same as in FIG. 1, and their explanation will be omitted.

12 is a check valve, and 20a, 20b, and 21 are electromagnetic valves. The opening and closing pattern of answers is the same as in the conventional method.

The evaporated helium is finally released to the atmosphere through the check valve 12.

In this embodiment, the number of valves is smaller than that in FIG. 1, making operation easier, improving reliability, and being advantageous in terms of cost.

〔Effect of the invention〕

According to the present invention, the thermal oscillation phenomenon of the current lead tube is eliminated, the amount of heat entering liquid helium is reduced, and the amount of helium evaporation is reduced.

Also, since there is a check valve, air does not get inside the pipe, so
No more ice on the tube.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a superconducting magnet according to one embodiment of the present invention, FIG. 2 is a piping diagram showing main parts of another embodiment of the present invention, and FIG. 3 is a diagram showing a conventional superconducting magnet. 1... Vacuum container 2... Helium container 3...
・Coil 5a, 5b...Current lead tube 8
...Relief pipe 11a, llb...Pressure equalization pipe agent Patent attorney Noriyuki Chika Ken Yudo Hirofumi MitsumataFigure 1 Figure 2 Figure 3

Claims (1)

[Claims] A superconducting magnet having a current lead tube cooled by helium gas and a pressure relief tube that releases helium gas to the atmosphere, characterized in that the current lead tube and the pressure relief tube are connected by a pressure equalizing tube.