JPS6122158A - Superfluid helium generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a superfluid helium generator, and more particularly to an improvement in a superfluid helium generator for cooling a large superconducting magnet.

[Prior art and its problems] As is well known, liquid helium is at the lambda point (2°17k)
At the following temperatures, there is a transition from a normal liquid, that is, a normal fluid liquid, to a superfluid liquid. Such superfluid helium is widely used as a coolant for superconducting magnets.

By the way, superfluid helium as a coolant for superconducting magnets can be divided into two types. One is saturated superfluid helium, which is obtained by reducing the pressure of liquid helium with a vacuum pump, and the other is unsaturated superfluid, which is produced by heat exchange with this saturated superfluid helium and is pressurized by one atmosphere. Helium (pressurized superfluid helium). The former is easy to generate, but the latter is relatively difficult to generate. However, the latter has much better heat transfer characteristics such as criticality and heat flux.

Therefore, pressurized superfluid helium gas is often used as the coolant for superconducting magnets.

A pressurized superfluid helium generator is generally constructed as shown in FIG. That is, a normal flow helium tank 1 containing 4.2k of l\thulium and a superfluid helium tank 2 are connected via a connecting pipe 3 which is normally closed with a valve 3'. The valve 3' is manufactured to such an extent that superfluid helium leaks even when the valve is closed.

A heat exchanger 4 for cooling the tank 2 to below the lambda point is arranged in the superfluid helium tank 2, and one end side of the heat exchanger 4 is connected to the Gicol 1 to Mouson valve (hereinafter referred to as J
It is abbreviated as T-valve. ) 5. Connect to the suction port of the vacuum pump 7 via the secondary side of the JT heat exchanger 6. The above-mentioned cryo-liquefaction machine 9 supplies liquid l\thulium to the helium tank 1.
, helium tank 1, helium tank 2, J T heat exchanger 6, J
1 valve 5 is housed in a heat insulating container 10.

Therefore, this device makes the liquid helium A in the superfluid helium tank 2 superfluid in the following manner. First, the valve 3- in the connecting pipe 3 is opened, and after introducing 4.2K of normal-flow liquid helium H into the superfluid helium tank 2 and the normal-flow helium tank 1, the valve 3- is closed.

In this state, the vacuum pump 7, compressor 8, and refrigeration liquefaction machine 9 are operated. When the vacuum pump operates, a portion of the 4.2k liquid helium 1 in the helium tank 1 is transferred to the primary side of the JT heat exchanger 6, the JTT valve, the heat exchanger 4, and the secondary side of the JT heat exchanger 6. flows. Assuming that the inside of the heat exchanger 4 is evacuated to a saturated vapor pressure corresponding to a temperature TS lower than the temperature Tb in the superfluid helium tank 2, the helium leaving the helium tank 1 is discharged into the JT heat exchanger 6. While passing through the primary side, it is precooled to, for example, 2°2K, and becomes gas and liquid at a temperature Ts.

This liquid evaporates while passing through the heat exchanger 4, thereby
The helium A in the superfluid helium tank 1 is cooled.

The superconducting magnet 12 is housed in the superfluid helium tank 2, and is excited by a power lead 13 passed through an insulating filler 11.

By the way, in this type of device, if the superconducting magnet is large, the superfluid helium tank becomes large and the amount of helium used increases. In addition, there is a problem in that extra refrigeration power is required to cool down the spill.

Also, during initial cooling from 4.2k to magnetic 6+11 degrees below the lambda point, temperature Tb and temperature Ts must be controlled to a constant relationship, and initial cooling is not always easy. Ta.

[Objective of the Invention 1 The present invention has been made in view of the above circumstances, and its purpose is to reduce the amount of superfluid helium necessary as a refrigerant for superconducting magnets and to facilitate the first 1ull freezing process. The purpose of this invention is to provide a superfluid helium generator.

[Summary of the Invention] The present invention utilizes a mist of saturated helium generated by Joule-Thomson expansion using a JT valve when initially cooling a superconducting magnet having an internal cooling channel to a magnet operating temperature below the lambda point. is passed through the cooling channel of the superconducting magnet to cool it down, and when the magnet reaches the operating temperature, the cooling channel of the superconducting magnet is filled with pressurized superfluid helium to maintain a steady state, and in this state the superconducting It is characterized by exciting a magnet.

Further, the present invention is characterized in that an initial cooling pipe is provided that bypasses the cooling flow path midway.

[Effects of the Invention] If the initial cooling from 4.2K is performed by passing mist-like helium through the cooling channel of the superconducting magnet as in the device of the present invention, it is easy to adjust the opening of the JT valve. Yes, it is only necessary to adjust the opening degree of the JT valve so that the temperature of the Joule-Thompson expanded mist is slightly lower than the temperature of the magnet.

In addition, when exciting the superconducting magnet, there is a heat transfer of 3f in the cooling channel.
Since it is filled with pressurized superfluid helium with good fi characteristics, stable excitation and demagnetization are possible. In particular, when a superconducting magnet is constructed from a bundle conductor, the thin superconducting wires that make up the bundle conductor are directly cooled, so even if the superconducting state is partially broken, a high cooling effect is expected to prevent the superconducting state from being restored. can.

Additionally, the amount of superfluid helium required for construction, refrigerant, etc. can be kept to a minimum.

[Embodiments of the Invention] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the main parts of a superfluid helium generator according to an embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. 2.) Duplicate explanations will be omitted.

The main difference between this embodiment and that shown in FIG. 1 is that in FIG. The superconducting magnet 14 with cooling channels is placed in an adiabatic vacuum.

One end of the internal cooling channel of the superconducting magnet 14 is connected to an insulating joint 15
The thin end of the internal cooling channel of the superconducting magnet 14 is connected to one end of the C heat exchanger 4 via a valve 16, and is also connected to the superfluid helium bath 2 via a valve 17. 18 to the secondary side of the JT heat exchanger 6. In addition, there is a valve 19 for bypassing the internal cooling channel of the superconducting magnet 14, and a valve 20 for bypassing a part of the internal cooling channel when precooling the superconducting magnet 14, and a valve 21 for bypassing the vacuum pump 7. has been established.

This system cools the superconducting magnet 14 to below the lambda point in the following manner. First, the valve 3' of the connecting pipe 3 is opened, and the valves 19, 20" and 18 are closed. The compressor 8 and the refrigerating liquefier 9 are operated with the JTT valve 5 valves 16, 17, 20, and 21 in between, and the superconducting magnet 14
Pre-cool. Super electric>? ; Ita stone 1/I valve 15, valve 1
When the internal cooling passage between the valves 20 and 20' has cooled down and the pressure loss is small, open the valve 20 and close the valve 20. When the internal cooling passage between the valves 20 and 20' has also cooled down, the 18 is opened, the valve 20''' is closed, and the whole is cooled to below 10%. Thereafter, the JT valve 5 and the valve 17 are closed, and the refrigeration liquefaction machine 9 is switched to liquefaction mode. helium tank 1,
Superfluid helium tank 2k Stores liquid helium.

Next, valve 21, valve 19, valve 18, valve 17, and valve 3 are closed. n'+'r
Operate the i+ liquefier 9 and start cooling to a temperature below 4.2K. If the opening degree of the JT valve 5 is adjusted to a temperature Tsh<slightly lower than the temperature of the superconducting magnet 14<'C, the saturation of the mist that occurs due to Joule 1-Mousson expansion will be reduced. Helium is heat exchanger 4 and superconducting magnet 1
The superfluid helium tank 2 and the superconducting magnet 14 are cooled by 7Jl (in the internal cooling channel 4). Once the superconducting magnet 14 has cooled down and the pressure loss in the first flow path becomes small, the helium return flow path is sequentially switched from valve 20 to valve 20' to valve 18. The superconducting magnet 14 is operated as a magnet if+X.
If +U is reached and it is IJ, the helium flow path is switched to valve 19, and valves 16, 20, 20'', and 18 are closed. I11
Introduce 1-1-super (71 co-moving helium) into the internal cooling channel of 4. In this state, the heat entering the superelectric 39 magnet 14'\ is transferred to the superfluid I\lium Δ through the heat exchanger 1. removed,
Stable excitation, 1""+L, capable of sharpening.

[Brief explanation of drawings]

FIG. 1 is a basic block diagram of a superfluid helium generator showing a typical embodiment of the present invention, and FIG. 2 is a basic block diagram of a conventional superfluid helium generator. 1... Constant flow helium tank (first helium tank), 2...
・Superfluid helium tank (second helium tank), 3...
Communication pipe, 4... Heat exchanger, 5... JT valve, 6...
JT heat exchanger, 14...super with internal cooling channel? 1f magnet. Representative F Patent Attorney Nearby Kenhata (and 1 other person) 1 year old

Claims (5)

[Claims] (1) A first helium tank containing normal-flow helium inside, a second helium tank located below the first helium tank, and provided on the upper wall of the second helium tank,
A normally closed communication pipe connecting the inside of the second helium tank and the inside of the first helium tank, and liquid helium in the first helium tank are used to pump helium in the second helium tank. A cooling section that utilizes the Joule-Thomson expansion effect to cool the temperature below the lambda point, an insulating jig, and the first and second
a superconducting magnet having an internal cooling channel connected to the cooling unit via an on-off valve; a third valve for opening and closing the channel between the superconducting magnet and the second helium tank; In a superfluid helium generator comprising a fourth valve that bypasses the internal cooling flow path of the magnet, during initial cooling from 4.2k, the third and fourth valves are closed and the first and second valves are closed. is opened, and a mist of saturated helium is flowed through the superconducting magnet having the internal flow path to cool it down to the magnet operating temperature of 2.2K or less, and when the operating temperature is reached, the first and second valves are closed and the second valve is opened. 3. A superfluid helium generator characterized by opening a fourth valve and cooling a superconducting magnet with pressurized superfluid helium. (2) The superfluid helium generator according to claim 1, wherein the superconducting magnet having an internal cooling channel is a bundle conductor. (3) The superfluid helium generator according to claim 1, wherein the superconducting magnet having an internal cooling channel is a hollow conductor. (4) Superfluid helium generation according to claim 1, characterized in that the internal cooling channel of the superconducting magnet is a metal pipe with good thermal conductivity that maintains good thermal contact between the coils. Device. (5) 1 in the middle of the flow path of a superconducting magnet with an internal cooling flow path.
2. The superfluid helium generator according to claim 1, further comprising at least one bypass pipe.