JPS6339618A - Automatic liquid helium supplying device - Google Patents

Abstract

PURPOSE:To automatically supply helium while avoiding loss of residual liquid helium in a cryostat, by controlling the operations of a pressure-raising means, an on-off valve and a discharge valve according to signals from a liquid level sensor and a temperature sensor. CONSTITUTION:When the amount of liquid helium in a cryostat 4 decreases, it is detected by a liquid level sensor 19, and a detection signal is fed to a controlling part 11, whereby a discharge valve 13 is opened. A heater 16 is operated, the pressure in a liquid helium storing container 2 is raised, and a helium gas generated by evaporation in a feeding pipe is discharged to the exterior as indicated by an arrow B. When the temperature of the helium gas thus discharged lowers to a predetermined temperature, a signal from a temperature sensor 4 is sent to the controlling part 11, whereby the discharge valve 13 is closed, whereas an on-off valve 10 is opened, so that liquid helium is permitted to flow from the container 2 into the cryostat 4 as indicated by an arrow A. Thus, it is possible to automatically supply liquid helium without needlessly increasing the consumption of liquid helium.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is used to transfer liquid from a liquid helium storage container into a cooling device for cryogenic tests (cryostat) in order to perform various cryogenic tests using liquid helium as a cooling medium. This relates to a device that automatically supplies helium.

BACKGROUND OF THE INVENTION The development of cryogenic engineering in recent years has been remarkable, and the cost of conducting various cryogenic tests has increased significantly recently. Cryogenic tests often use liquid helium as a cooling medium. In this case, liquid helium is injected into a cooling container called a cryostat, and the test object or test equipment is heated directly or indirectly with liquid helium. It is usual to cool the material and perform cryogenic tests. Therefore, in cryogenic tests, it is necessary to supply liquid helium into the cryostat from a liquid helium storage container (referred to as a dewar).

Generally, to supply such liquid helium, an insulated double-tube transfer pipe called a transfer tube is usually used, and one end of the transfer pipe 1 is connected as shown in Fig. 2. is immersed in the liquid helium 3 in the liquid helium storage container 2, the other end of the transfer tube 1 is inserted into the cryostat 4, the inside of the liquid helium storage container 2 is pressurized, and the liquid in the storage container 2 is immersed. Helium is pumped into the cryostat 4 through the transfer pipe 1.
ζ Normal. Here, pressurization for pumping liquid helium is performed by supplying helium gas under pressure to the upper space of the liquid helium storage container 2, or by immersing a heater in the liquid helium in the liquid helium storage container 2. This is done by heating and increasing the pressure using the heater.

Note that the tip of the transfer tube 1 inside the cryostat 4 is normally left open in a state close to the bottom surface inside the cryostat 4. That is, when liquid helium is first started to be supplied into the cryostat 4, the liquid helium usually vaporizes at the open end of the transfer tube 1; If the end is close to the bottom of the cryostat 4, the temperature of the bottom of the bottom will drop quickly due to the sensible heat of the vaporized helium gas, which will eventually prevent the liquid helium from vaporizing and turn it into a liquid helium state. Liquid helium will be injected into the cryostat, but if the tip of the transfer tube 1 is far from the bottom of the cryostat, vaporization of liquid helium at the tip of the transfer tube will not be prevented forever, and liquid helium will not be injected into the cryostat. This is because there are many things that cannot be done.

By the way, during the cryogenic test, the liquid helium in the cryostat gradually decreases due to gasification, so in order to continue the cryogenic test, it is necessary to replenish the liquid helium once it has decreased to a certain extent. . Therefore, conventionally, as shown in FIG. 2, a level sensor 5 for detecting the level of liquid helium is provided in the cryostat, and the level sensor 5 is monitored to determine the level of liquid helium in advance. Once the robot has descended to the determined position, the replenishment operation is carried out in the same way as the initial replenishment operation. Note that the transfer tube may remain inserted into the cryostat even after the first supply operation, or it may be removed from the cryostat after the first supply operation and reinserted in the next replenishment operation.

However, during actual cryogenic tests, monitoring the level of liquid helium, which is the cooling medium, and replenishing liquid helium are secondary tasks for the test personnel, and the test personnel are responsible for operating the main body and conducting the original experiment. Because they are often busy monitoring data, cryogenic tests may be interrupted without noticing the decrease in liquid helium until it runs out, or unnecessary loss of liquid helium may occur due to poor replenishment operations. There were many things. Therefore, it is desired to develop a device that can automatically replenish liquid helium. If such a device is developed,
This not only eliminates the above-mentioned inconveniences, but also reduces the burden on test personnel who were required to monitor the liquid level and replenish the liquid, allowing them to concentrate on the primary purpose of cryogenic testing, which is considered to be of great benefit.

As mentioned above, in order to automate the replenishment of liquid helium during cryogenic tests, the tip of the transfer tube is kept immersed in the cryostat at all times during cryogenic tests, and the liquid helium level in the cryostat is kept constant. is automatically detected, and in response to the detection signal, automatically starts pressurizing the liquid helium storage container (for example, heating and pressurizing with a heater as described above or pressurizing with helium gas), and It is conceivable that by automatically opening the valve 6, liquid helium is automatically replenished from the storage container into the cryostat via the transfer pipe. However, this type of replenishment system actually has problems as described in the next section, making it difficult to put it into practical use.

Problems to be Solved by the Invention In actual cryogenic experiments, the length of the transfer tube for transferring liquid helium from the liquid helium storage container to the cryostat is usually several meters, and the initial liquid From one helium supply operation to the next,
Ordinarily, a considerable amount of time has passed between the previous replenishment operation and the next replenishment operation. On the other hand, although the transfer pipe has an insulated double pipe structure, complete insulation is not possible, so as mentioned above, if time has passed since the first liquid helium supply operation or the previous liquid helium supply operation, In the intermediate portion of the transfer tube, liquid helium is gasified, and the temperature of the gasified helium and the inner wall of the transfer tube rises to near room temperature. If replenishment work is started in such a state, the helium gas inside the transfer tube, which is close to room temperature, and the gas warmed by the inner wall of the transfer tube will be pumped into the cryostat. Since the length of the transfer pipe is quite large, it reaches a considerable maximum.

If a considerable amount of helium gas close to room temperature is pumped into the cryostat in this way, the gas will raise the temperature of the liquid helium remaining in the Taliostat and turn it into gas, resulting in the liquid helium being wasted. become. In other words, in a cryostat, as mentioned above, the open end of the transfer tube is usually kept close to the internal bottom surface of the cryostat, and in this state, a considerable amount of water close to room temperature is discharged from the tip of the transfer tube. If helium gas is injected, a considerable amount of the liquid helium left over from the previous time in the cryostat will quickly vaporize. Therefore, with this method, there is a problem that the loss of liquid helium is extremely large, the consumption of expensive liquid helium increases, and the cost of cryogenic testing becomes extremely high.
Practical implementation was difficult.

This invention was made against the background of the above circumstances, and it is possible to automatically replenish liquid helium to a cryostat without incurring loss due to vaporization of residual liquid helium in the taliostat during replenishment work. The purpose is to provide a device.

Means for Solving the Problems This invention provides an apparatus for supplying liquid helium from a liquid helium storage container into a cryostat, in which one end is immersed in liquid helium in the liquid helium storage container and the other end is immersed in the cryostat. a transfer pipe having an adiabatic structure inserted into the cryostat, a pressure increasing means for increasing the pressure in the liquid helium storage container, a liquid level detector for detecting the liquid level of liquid helium in the cryostat, and a cryostat in the transfer pipe. A discharge pipe branching from the transfer pipe at a nearby location and communicating with the outside, a discharge valve opening and closing the discharge pipe, a temperature detector detecting the temperature within the discharge pipe, and a branch position of the discharge pipe. an on-off valve that opens and closes the transfer pipe at a position closer to the cryostat, and a control section that controls the release valve, the on-off valve, and the pressure increase means in accordance with signals from the liquid level detector and the temperature sensor. It is characterized by the fact that

Function: In the apparatus of the present invention, when liquid helium is initially supplied into the cryostat, one end of the transfer tube is inserted into the liquid helium in the liquid helium storage container, and the other end is inserted into the cryostat, and the pressure is increased. The means is actuated to raise the pressure inside the storage container and open the on-off valve. However, the discharge valve should be kept closed. In this way, the liquid helium in the liquid helium storage container is transferred and supplied into the cryostat via the transfer pipe by the pressure.

When the level of liquid helium in the cryostat reaches a predetermined level, the liquid level detector detects this, and in response to the detection signal, the on-off valve is closed by a control signal from the control unit, and the pressure increases. the means are deactivated;
This stops the supply of liquid helium to the cryostat.

After a predetermined amount of liquid helium is stored in the cryostat in this way, various cryogenic tests are usually started, during which time the skin helium (in the cryostat) gradually evaporates and gradually That lead is decreasing. During this time, the liquid helium in the transfer tube exposed to the atmosphere vaporizes, and the temperature of the vaporized helium scum and the inner wall of the transfer tube rises to near room temperature.

As mentioned above, when the amount of liquid helium in the cryostat decreases and the level decreases to a predetermined level, the liquid level detector detects this, and in response to the detection signal, a control signal from the control unit is sent. The pressure increase means is started to operate and the release valve is opened. However, in this state, the on-off valve is closed. Therefore, the helium gas that has been vaporized in the transfer pipe and whose temperature has risen to near room temperature after the previous supply is discharged to the outside via the discharge pipe and the discharge valve by the pressure applied by the pressure increasing means. When the temperature sensor detects that the temperature of the released gas has dropped to a predetermined temperature, in other words, the helium gas near room temperature that was present in the transfer tube has been almost completely exhausted and When it is confirmed that the wall is completely cooled, the discharge valve is closed and the on-off valve is opened by a control signal from the controller in response to a signal from the temperature sensor. Note that the pressure increasing means continues to operate as is. Therefore, as in the first supply, the liquid helium in the storage container is supplied into the cryostat via the transfer pipe. When the level of liquid helium in the cryostat reaches a certain level, the on-off valve is closed by a command from the control unit in response to a signal from the liquid level detector, and the operation of the pressure increase means is stopped, and the liquid helium is supply will be suspended.

After this, when the liquid helium in the cryostat decreases to the level again, liquid helium is replenished in the same manner as described above.

As mentioned above, during replenishment, the helium gas near room temperature that initially existed in the transfer pipe is released to the outside via the release pipe and release valve, and then the temperature of the released gas reaches a certain temperature. Supply of liquid helium gas into the cryostat is started only when the temperature sensor detects that the temperature has dropped. Therefore, the helium gas vaporized in the transfer tube and heated to near room temperature and the helium gas heated to near room temperature on the inner wall of the transfer tube will not be blown into the cryostat. Therefore, by blowing helium gas near room temperature into the cryostat, liquid helium remaining in the cryostat is effectively prevented from being vaporized and lost.

In this manner, the apparatus of the present invention can automatically replenish liquid helium without losing the liquid helium remaining in the cryostat at the time of replenishment.

Example FIG. 1 shows an example of the apparatus of the present invention.

In FIG. 1, liquid helium 3 is stored in a liquid helium storage container 2, and one end 1A of a transfer tube 1 is immersed in this liquid helium 3. The transfer tube 1 is generally referred to as a transfer tube, and
Usually has an insulated double pipe structure. The other end 1B of the transfer tube 1 is inserted into the cooling hole 4A of the cryostat 4, and its tip is close to the bottom surface of the cooling hole 4A.

An on-off valve 10 for opening and closing the pipeline of the transfer pipe 1 is provided at a position as close as possible to the cryostat 4 in the transfer pipe 1, and this on-off valve 10 is controlled by a control unit consisting of a microprocessor or the like. 11. The on-off valve 10 in the rough transfer pipe 1
A discharge pipe 12 that communicates with the outside is branched from a position close to the on-off valve 10 (a position closer to the liquid helium storage container 2 than the on-off valve 10) A discharge valve 13 and a temperature sensor 14 are provided for the purpose of this. The discharge valve 13 is controlled by the control section 11, and the temperature detector 14 is arranged so that its detection signal is given to the control section 11.

Furthermore, a liquid level detector 15 for detecting the liquid level of the liquid helium 3 is disposed inside the liquid helium storage container 2, and a heater is provided as a pressure increasing means for increasing the pressure inside the storage container 2. 16 are arranged. This heater 16 is controlled by the control section 11, and a detection signal from the liquid level detector 15 is supplied to the control section 11. Further, the liquid helium storage container 2 is connected to a pressure detector 17 and a gas release valve 18 for detecting the internal pressure of the storage container 2 (pressure of vaporized helium gas). On the other hand, a liquid level detector 19 for detecting the level of the supplied liquid helium is disposed inside the taliostat 4, and a detection signal of this liquid level detector 19 is transmitted to the control unit 1.
It is designed to be given to 1.

The operation of the above embodiment will be explained next.

First, when liquid helium is supplied to the empty cryostat 4, the heater 16 is activated to heat the liquid helium 3 in the liquid helium storage container 2 and increase the vapor pressure in the storage container 2. Further, while the discharge valve 13 remains closed, the on-off valve 10 is opened. In this way, the pressure increase in the storage container 2 causes the liquid helium 3 in the storage container 2 to be sent into the transfer pipe 1, roughly in the direction of the solid line arrow A in FIG.
The cryostat 4 passes through the on-off valve 10 as shown in
flow inward. At this time, the pressure inside the storage container 2 is detected by the pressure detector 17 connected to the storage container 2, and the signal is given to the control section 11 to feedback-control the heat generation of the heater 16, thereby controlling the temperature of the storage container 2. Maintains constant internal pressure. In this way, when liquid helium is supplied into the cryostat 4 and its level reaches a predetermined level, it is detected by one liquid level detector, and the detection signal is given to the control unit 11 to control the A control signal from the section 11 causes the heater 16 to stop operating, the on-off valve 10 to be closed, and the discharge valve 18 to be opened. This completes the first liquid helium supply operation.

After that, when the liquid helium in the cryostat 4 falls to a decreasing level, it is detected by the liquid level detector 1.
9 is detected, the detection signal is given to the control section 11, and the control signal from the control section 11 starts the operation of the heater 16, and at the same time, the discharge valve 13 is opened. Heater 1
6, the liquid helium storage container 2 is opened as described above.
As the pressure inside rises, the vaporized helium gas near room temperature between the position of the storage container 2 in the transfer pipe 1 and the branch position of the discharge pipe 12 is discharged as shown by the broken line arrow B in FIG. It is discharged to the outside through the pipe line 12 and the discharge valve 13. The temperature of this released helium gas is detected by a temperature detector 14. This detected temperature rapidly decreases when the helium gas near room temperature that has remained in the transfer tube 1 is almost completely exhausted and the inner wall of the transfer tube 1 is sufficiently cooled. Therefore, when the temperature drops to a predetermined liquid helium temperature or a temperature close to it, the control section 11 controls the release valve 13 by a signal from the temperature detector 14.
It generates a control signal to close the on-off valve 10, and simultaneously or subsequently generates a control signal to open the on-off valve 10. As a result, the discharge valve 13 is closed, while the on-off valve 10 is opened, so that the pressure causes the liquid helium storage container 2 to
The liquid helium sent into the transfer pipe 1 passes through the on-off valve 10 and flows into the cryostat 4 as shown by the solid arrow A in FIG. In this way, when the level of liquid helium in the cryostat 4 is reached, the opening/closing valve 10 is closed by the detection signal from the liquid level detector 19 and the heater is 16 is stopped, and the discharge valve 1
8 is released.

In the above embodiment, a heater is used as a pressure increasing means, but in some cases, the heater is not used and helium gas is supplied under pressure from the outside into the storage container 2 to increase the pressure. You may do so.

Effects of the Invention As is clear from the above explanation, the device of this invention has the following effects:
When replenishing liquid helium from the liquid helium storage container through the transfer pipe into the Talaiosta l~, there must be a gap between the first supply and the replenishment, or between the previous replenishment and the next replenishment. It is possible to effectively prevent the helium gas that has vaporized in the transfer pipe and whose temperature has risen to near room temperature and the helium gas warmed by the inner wall of the transfer pipe whose temperature has risen to near room temperature from being blown into the cryostat. Since residual liquid helium in the cryostat is prevented from being lost, liquid helium can be automatically replenished without unnecessarily increasing the amount of liquid helium consumed. As a result, it becomes possible to automatically replenish liquid helium to the taliostat at a low cost and in practice, thereby preventing forgetting to replenish liquid helium during cryogenic tests and hindering the execution of the test. It is possible to achieve various effects such as preventing this and reducing the burden on test personnel.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an automatic liquid helium supply system of the present invention, and FIG. 2 is a schematic diagram showing an example of a conventional liquid helium supply system. 1...Transfer pipe, 2...Liquid helium storage container, 3
...liquid helium, 4...thaliostat, 1
0... Opening/closing valve, 11... Control unit, 12... Discharge pipe line, 13... Discharge valve, 14... Temperature detector, 16... Heater as pressure increasing means, 19.・
・Liquid level detector. Figure 2

Claims (1)

[Claims] A device for supplying liquid helium from a liquid helium storage container into a cryostat, comprising: a transfer tube having an insulated structure, one end of which is immersed in liquid helium in the liquid helium storage container, and the other end of which is inserted into the cryostat; a pressure increasing means for increasing the pressure within the liquid helium storage container; a liquid level detector for detecting the liquid helium level within the cryostat; and a portion of the transfer tube near the cryostat that is branched from the transfer tube and communicates with the outside. a discharge pipe to open and close the discharge pipe, a discharge valve to open and close the discharge pipe, a temperature detector to detect the temperature in the discharge pipe, and a transfer pipe to open and close at a position closer to the cryostat than a branch position of the discharge pipe. An automatic liquid helium supply device comprising: an on-off valve; and a control section that controls the release valve, the on-off valve, and pressure increase means in accordance with signals from the liquid level detector and temperature detector. .