JPS6119986A - Cryopump - Google Patents

Abstract

PURPOSE:To prevent a flooding phenomenon from occurring as well as to aim at improvements in cooling capacity ever so better, by forming a connecting pipe line between a vessel inside a panel in a vacuum vessel and a dewer into a double pipe structure, while separating a gaseous phase stream and a liquid phase stream of the present pump, which exhausts the inside of the vacuum vessel to a superhigh vacuum, to the full. CONSTITUTION:An updraft flowing from a vessel 7 inside a panel to a dewer 3 is being cooled in time of passing through liquid helium 6 whereby in time of passing through a connecting pipe line 10, its heat exchange with an outer surface of an inner tube 12 is almost nothing, and furthermore such an effect as seeding the inner pipe 12 from ambient radiant heat is secured. In consequence, a portion for evaporation of the liquid helium inside the inner pipe 12 is almost nothing there, whereby a circulating circuit of a liquid helium storage part 16 a liquid phase inflow port 13 the inner pipe 12 the panel inside vessel 7 a vapored position outlet 14 the connecting pipe line 10 a helium space 15 in an interval between the panel inside vessel 7 of a panel heat receiving plate 2 and the dewer 3 by the connecting pipe line 10 and the inner pipe 12, therefore no flooding happens there so that the state is stabilized and a loss of heat is very little whereby replenishment of the liquid helium and exhaust of vapored gas take place so smoothly, thus cooling capacity is improved.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a vacuum container for a nuclear fusion device, etc., and in particular to a gas-liquid phase cryopump used to evacuate the inside of a vacuum container for a nuclear fusion device to an ultra-high vacuum. It concerns the flow separation structure.

[Background of the invention]

To evacuate vacuum containers such as nuclear fusion devices to ultra-high vacuum,
A cryopump is used that has an ultra-high capacity pumping speed equivalent to tens to hundreds of liters per second. A cryopump consists of a pressure vessel filled with a cryogenic liquefied gas (usually liquid helium) inside a vacuum vessel, and the pressure vessel is heated to a temperature of liquid helium (usually liquid helium).
-269 tll'), gas molecules in the vacuum container are adsorbed and solidified on the surface of the container, and then evacuated.

The mixed heat of vaporization of liquid helium used here is zo, 9J/
Because it is extremely small (gU), it vaporizes with a small amount of heat. A conventional method for dealing with this will be explained with reference to FIGS. 2 and 3.

FIG. 2A is a schematic diagram of the main parts of a cryopump placed in a vacuum vessel and filled with liquid helium. In the figure, 2 is a panel heat receiving plate for filling liquid helium and cooling the inside of the vacuum container, 4 is a liquid helium supply pipe, and 6
1 is an inlet for liquid helium, 7 is an inner panel container filled with liquid helium within the panel heat receiving plate 2, and 11 is an exhaust port for vaporized gas.

Since the gas vaporized by a small amount of heat exits from the exhaust port 11 at a tremendous speed, it is necessary to replenish liquid helium in an amount corresponding to that amount. There is also a method of refilling directly from the supply pipe 4 as shown in Figure 2B, but since it is not possible to respond precisely to load fluctuations, as shown in Figure 2B, the dewar 3 is used as a storage tank.
It is common to provide Inside the dewar 3, there are vaporized helium gas 15 and a liquid helium portion 16. When the liquid helium in the panel inner container 7 is about to run out, liquid helium 16 is poured into the panel inner container 7 through the connecting pipe 1o. It becomes a liquid phase flow and flows into the trap to compensate.

However, the liquid helicum liquid phase flow descending from the connecting pipe 1o to the panel inner container 7 may be blocked by the upward gas phase flow of vaporized gas generated within the container 7. This is the so-called flooding phenomenon.

When a flooding phenomenon occurs, the liquid phase flow becomes difficult to descend, the load increases, and vaporized gas further increases.T1
It progresses to a stable state.

Three examples of methods for supplying and replenishing liquefied gas as a refrigerant are shown in FIG. In the example shown in FIG. 2B, the liquefied gas is supplied from the inlet 6 at the lower end of the container 7, and the replenishment amount of liquefied gas flows against the gas phase flow rising through the connecting pipe 10. It must descend into the container 7. FIG. 3B shows an example in which valve 5A is opened to supply liquefied gas, while valve 5B is opened to replenish the shortage of liquefied gas.
The fact that the gas phase flow and the liquid phase flow flow in opposite directions is the same as in the example of Figure 3, and the flooding phenomenon cannot be prevented. Furthermore, FIG. 3C shows that the supply of liquefied gas is
This is an example in which the connecting pipe 10 is divided into two to separate the gas phase flow and the liquid phase flow. However, since the upper and lower ends of the two 1° connecting pipes are both at the same height and the same shape, which one is used for the liquid phase flow depends on the ratio and pressure of the gas phase flow and liquid phase flow at that time. changes,
Furthermore, the possibility of a gas-liquid mixed flow still remains, and the fundamental prevention of shaving and flooding phenomena has not been achieved.

[Purpose of the invention]

An object of the present invention is to provide a connection piping that completely separates the gas phase flow and liquid phase flow of a cryopump that evacuates the inside of a vacuum vessel such as a nuclear fusion device to an ultra-high vacuum, and prevents flooding phenomenon. The goal is to increase the cooling capacity of the pump.

[Summary of the invention]

In the present invention, the connecting piping between the panel inner container and the dewar in the vacuum container has a double pipe structure, the inner pipe is a liquid refrigerant supply pipe, and the space between the inner pipe and the outer pipe is separated into a vaporized gas exhaust path. At the same time, the flow path for the gas phase flow was extended to the helium gas area inside the dewar, while the inner pipe for the liquid phase flow was lengthened into the container inside the panel and further curved upward to avoid the intrusion of the gas phase flow. It proposes a structure.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described in more detail with reference to FIG. In the figure, 1 is a vacuum container whose inside is to be made into an ultra-high vacuum by the cryopump, 2 is a panel heat receiving plate which is the main part of the cryopump, and 3 is a panel heat receiving plate 2.
A dewar 1 serves as a liquid storage tank for separating the gas consumed and vaporized into gas and liquid and replenishing the consumed amount to the heat receiving plate 2.
4 is a supply pipe for supplying liquefied helium gas from outside the vacuum container, 5 is a flow rate control valve thereof, 6 is an inlet at the bottom of the panel heat receiving plate 2, 7 is a container inside the panel filled with liquefied gas, 8 is a heat receiving plate A shield plate provided for heat shielding 2, 9
10 is a chevron-type baffle that traps particles to be exhausted; 10 is a connecting pipe between the dewar 3 and the panel inner container 7; 1
F is the exhaust pipe for the vaporized helium gas, 15 is the vaporized helium gas, 16 is the storage liquid helium, 17 is the liquid helium flow direction, and 18 is the vaporized helium flow direction.With the structure so far, the liquefied helium is transferred to the vacuum container. When liquid helium is injected from the outside via the supply pipe 4 and the flow rate regulating valve 5, the liquid helium flows from the inlet 6 of the funnel heat receiving plate 2 into the panel inner container 7. (The flannel heat receiving plate 2 receives thermal radiation from the wall surface of the vacuum vessel 1, a shield plate 8 that heat-shields the heat receiving plate 2, or a chevron type) (Tuffle 9, etc.). When the latent heat of vaporization is less than the amount of heat received by the heat receiving plate 2, all the liquid helium that enters the tunnel inner container 7 from the inlet 6 is vaporized, enters the dewar 3 through the connecting pipe 10, and exits the exhaust pipe 11. On the other hand, if the amount of refrigerant supplied by the inflowing liquid helium is larger, the inner vessel 7, the connecting pipe 10, and the dewar 3 are gradually filled with liquid helium.

When load operation is performed in this state and the thermal load on the cryonnel heat receiving plate 2 increases, the liquid helium in the cryonnel inner container 7 is vaporized and moved from the connecting pipe 10 to the dewar 3. At this time, if the load is large and the speed of the gas phase flow rising inside the connecting pipe 10 exceeds a certain range, a flooding phenomenon will occur, and the descent of the liquid phase flow from the dewar 3 to the panel inner container 7 will be inhibited. The liquid helium stored in the panel inner container 7 quickly vaporizes.

In order to prevent the occurrence of this flooding phenomenon, the present invention provides an inner pipe 12 coaxially within the connecting pipe 10 to ensure that liquid helium is replenished from the dewar 3 to the panel inner container 7. The inlet of the liquid phase flow is located at the position 13 at the bottom of the dewar 3, and the outlet to the container 7 inside the panel is slightly protruded inward, and the outlet is shaped so that it does not face downward in order to prevent the gas phase flow from entering. It's Nishide.

On the other hand, in order to prevent the helium gas vaporized by the panel heat receiving plate 2 from disturbing the flow of liquid helium near the liquid phase light inlet 13, the outlet for vaporized helium is extended to the helium gas space 15 above the dewar 3. .

With this structure, the helium gas vaporized by heat received by the panel heat receiving plate 2 passes through the liquid helium of the panel inner container 7 and is exhausted to the dewar 3 from the outlet 14 provided at the top of the container. At this time, the discharged gas flows through the inlet 13
Do not disturb the flow of nearby liquid helium. Also, dewar
The descending liquid phase flow from 3 to the panel inner container 7 passes through the inner tube 12, and the discharge port of the inner tube 12 is curved upward so as not to receive the intrusion of the gas phase flow. Therefore, replenishment of liquid helium is ensured, and the gas phase flow and the liquid phase flow are completely separated, so that no flooding phenomenon occurs.

In addition, if you just want to completely separate the gas phase flow and liquid phase flow,
If the pipe 12 is not passed through the connecting pipe 10, but the two pipes are installed separately, and the positions and shapes of both discharge ports are formed according to the main points of the present invention, the purpose can be achieved.

However, in the double tube structure described above, the ascending gas phase flow from the panel inner vessel 7 to the dewar 3 is cooled when passing through the liquid helium, so it is mostly at the liquefaction temperature of 4.
The temperature is slightly higher than 2°K. Therefore, when passing through the connecting pipe 10, the heat exchange with the outer surface of the inner pipe 12 is negligible, and the effect of thermally shielding the inner pipe 12 from surrounding radiant heat is obtained. There is almost no vaporization of liquid helium in the inner tube 12, and there is no connection pipe 10 and inner tube between the panel inner container 7 of the panel heat receiving plate 2 of the cryopump housed in the vacuum container 1 and the dewar 3. The pipe 12 forms a circulation circuit of liquid helium storage section 16 -> liquid phase flow chamber 13 -> inner pipe 12 -> panel inner container 7 -> vaporization drawer 14 -> connection pipe 10 -> gas helium space 15, and flooding is eliminated. As a result, conditions are stabilized, heat loss is small, and liquid helium can be replenished and vaporized gas can be exhausted smoothly.

〔Effect of the invention〕

According to the present invention, the gas phase flow and liquid phase flow of a cryopump that evacuates the inside of a vacuum container such as a nuclear fusion device to an ultra-high vacuum are completely separated, the flooding phenomenon is eliminated, and the cooling effect of the cryopump is enhanced. .

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the cryopump according to the present invention, Fig. 2 is a schematic diagram of the main parts of the conventional Nori-2 Iopump, and Fig. 3 shows the liquefied gas supply and replenishment method of the conventional cryopump. It is a schematic diagram. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... Panel heat receiving plate, 3... Dewar-14... Supply piping, 5... Flow rate adjustment valve, 6...
...Liquefied gas inlet, 730. Burl inner container, 8...
Shield plate, 9...Chevron type baffle, 10...
・Connection M, wiring L 11...exhaust pipe, 12...inner pipe,
13...Liquid phase mud inlet, 14...Vaporization outlet, 15
... Gas helium space, 16... Liquefied helium storage section, 17... Liquid helium flow direction, 18... Vaporized helium flow direction.

Claims (1)

[Claims] 1. In order to evacuate the inside of the vacuum container to an ultra-high vacuum, a panel heat receiving plate housed within the vacuum container and supply piping that supplies cryogenic liquid refrigerant to the panel inner container formed within the panel heat receiving plate. A dewar that separates the refrigerant gas that has been consumed and vaporized in the panel inner container and stores the liquid refrigerant to replenish the liquid refrigerant that is insufficient due to vaporization, a connecting pipe that connects the panel inner container and the dewar, and In a cryopump that consists of a dewar and an exhaust pipe that exhausts the air outside the vacuum container, the connecting pipe is provided with an internal pipe for liquid phase flow, the liquid refrigerant inlet is formed at the bottom of the dewar, and the liquid refrigerant outlet is extended into the panel container and upwards. At the same time, the connection pipe is used for vapor phase flow of vaporized gas, and its discharge port is extended to the gas storage part within the dewar, and a circulation circuit is formed by the panel inner container, the connection pipe, the dewar, and the inner pipe. Characteristic cryopump.