JPH04279777A - Cryo pump - Google Patents

Abstract

PURPOSE:To increase the exhausting speed of a cryo pump by disposing auxiliary cryo panels extended from cryo panels on the back side of each louver, and concurrently forming each auxiliary cryo panel into a strip shape in order to avoid making contact with a louver holder holding each louver. CONSTITUTION:In a cryo panel 22 which condenses and coagulates exhausted gas so as to be trapped, a fin 27 is brazed onto a flow path which is enclosed by respective metallic plates 23 and 24 and respective plates 25 and 26. In this case, each auxiliary metallic cryo panel 28 is integrated with the respective plate 23 and 24 by means of brazing and the like. And a louver holder 32 is combined with each metallic louver 29, and each front heat shielding plate 30 and 31 so as to be integrated by means of brazing and the like. Furthermore, the louver holder 32 is fixed onto a holder plate 35, and the holder plate 35 is supported in a space interspaced with a rear heat shielding plate 33. Each auxiliary cryo panel 28 is parted at a specified pitch in the longer direction of the cryo panel 22.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryopump that condenses and adsorbs gas molecules on a cryopanel surface cooled to an extremely low temperature and exhausts the gas molecules at high speed.

0002

[Prior Art] Conventional cryopanels are
As described in Japanese Patent No. 169682, a plurality of cryopanels with a single flat surface cooled to an extremely low temperature of 5.0 K or less with liquid helium or the like are arranged perpendicularly to the gas inlet surface of the cryopump. There is. Liquid helium evaporates with very little heat and is an expensive refrigerant. In order to reduce the amount of evaporation of liquid helium, the area around the cryopanel is covered with liquid nitrogen for approximately 80 minutes, so that the cryopanel is not directly heated by radiant heat from the room-temperature, high-temperature part outside the pump.
A heat shield plate cooled to a low temperature of K is placed.

[0003] The heat shield plates on both sides of the cryopump are of the louver blind type, and the exhausted gas molecules pass through the gaps between the louvers and collide with the extremely low temperature cryopanel, where they are condensed and adsorbed.

[0004] The surface of the louver is treated with a black color to absorb radiant heat, and external light rays reach the cryopanel after colliding with these heat shield plates at least once.

Gas molecules to be exhausted collide once or several times with the front heat shield plate adjacent to the front of the pump, while some gas molecules flow out from the pump inlet.
Certain molecules reach the cryopanel and are coagulated and adsorbed.

[0006]

[Problems to be Solved by the Invention] In the conventional technology described above, the cryopanels are arranged at a distance downstream of the louvers, so the number of gas molecules flowing out from the pump inlet during repeated collisions between the louvers is limited. There was a problem in that the probability of increase in gas molecules increased and the pumping speed of gas molecules decreased.

However, the neutral particle injection device used in recent large-scale nuclear fusion devices requires a cryopump that can pump out hydrogen and deuterium at a high rate. On the other hand, since the neutral particle injection device is constructed of a vacuum container, the beam-facing aperture area and volume of the cryopump installed inside are reduced. That is, it is important to reduce the manufacturing cost by making the vacuum container smaller by improving the performance and miniaturization of the cryopump.

An object of the present invention is to increase the pumping speed of a cryopump.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an auxiliary cryopanel extending from the cryopanel on the back side of the louver. The sub cryopanel is shaped like a strip to avoid contact with a louver holder holding a plurality of louvers.

Furthermore, in order to efficiently cool the louver, a cooling pipe is metallurgically integrated with the louver holder.

[0011]

[Operation] Gas molecules incident from the pump inlet face hit the heat shield plate or louvers, and are exhausted only when they enter the cryopanel at an incident angle that allows them to pass through the louvers while being reflected repeatedly. The gas molecules hit the surface of the louver at least once, and then either (1) collide with the cryopanel, (2) hit the back side of the upper louver, or (3) be returned to the outside of the louver. However, by arranging the sub-cryopanel on the back surface of the louver, the gas molecules (2) can be made to collide with the sub-cryopanel and this gas can be exhausted.

[0012] The sub-cryopanel is arranged so that it extends to the tip of the louver on the back side of the large louver within a range where it is not directly hit by the light beam, so that the probability of capturing gas molecules is increased.

Furthermore, since the louver holder is integrated with a cooling pipe through which a refrigerant for cooling the louver flows, the louver holder is cooled to a temperature close to that of the refrigerant. Therefore, the louver integrated with the louver holder by soldering or the like is efficiently cooled, and the temperature of the louver becomes close to the temperature of the refrigerant. Therefore, the amount of heat that enters the cryopanel and sub-cryopanel from the louver by radiant heat can be minimized.

[0014]

[Example] An example of the present invention will be described below in Figs. 1, 2, and 3.
This is explained by: Figure 1 shows an example of the configuration of a cryopump cooling system. The cryopump 1 is placed in a vacuum container 2 such as a neutral particle injection device or a space chamber of a nuclear fusion device. The cryopump 1 is composed of a single unit 3 or a plurality of unit groups 3. The upper part of each unit 3 communicates with the liquid helium upper tank 4 and the liquid nitrogen upper tank 5 via piping 6 and piping 7, and the lower part of each unit 3 communicates with the liquid helium lower tank 8 and liquid nitrogen upper tank 5 through piping 10 and piping 11. It communicates with the liquid nitrogen lower tank 9.

The liquid helium 12 is supplied to the helium liquefaction device 1.
3 and is supplied to the liquid helium upper tank 4 through a liquid helium supply pipe. The liquid helium upper tank and the liquid helium lower tank are connected to the liquid helium bypass pipe 15.
communicated via. The helium gas heated and evaporated by the cryopump 1 is transferred to the liquid helium upper tank 4.
The helium gas returns to the helium liquefaction device through the helium gas recovery pipe 16 and is liquefied again.

On the other hand, liquid nitrogen 17 is supplied into the liquid nitrogen upper tank 5 through a supply pipe 19 from a nitrogen liquefier or a nitrogen storage tank 18 . The liquid nitrogen upper tank and the liquid nitrogen lower tank are communicated via a liquid nitrogen bypass pipe 20. Louver and heat shield plate inside the cryopump (
The nitrogen gas heated and evaporated in the process (described in FIG. 2) returns to the nitrogen liquefaction device through the liquid nitrogen upper tank 5 and the nitrogen gas recovery pipe 21, and is either liquefied again or released into the atmosphere. The liquid helium and liquid nitrogen in the liquid helium upper tank and the liquid nitrogen upper tank are circulated by natural circulation to the liquid helium bus pass pipe 15 and the liquid nitrogen bypass pipe 2, respectively.
0 into the cryopump.

FIG. 2 is a cross-sectional view of the top of a cryopump that combines three units, and FIG. 3 is a perspective view of two units.

The cryopanel 22, which condenses and solidifies the exhaust gas and traps it, has fins in a flow path surrounded by metal plates 23, 24 and side plates 25, 26 made of stainless steel, copper, aluminum, etc. 27 are brazed, and these are metallurgically integrated. The plates 23 and 24 are metallurgically integrated with a sub-cryopanel 28 made of uneven stainless steel made by extrusion molding or a metal such as copper or aluminum by brazing or the like. Liquid helium flows through the cryopanel by natural circulation via piping 6 and piping 7, and the cryopanel flows through 4.
It is cooled to an extremely low temperature of 5K or less.

On the other hand, the louver 29 and front heat shield plate 30 are made of metal such as stainless steel, copper, or aluminum.
, 31 are combined with the louver holder 32 in a comb-like shape,
The combined parts are metallurgically integrated by brazing or the like. The louver holder 32 is cooled to a temperature of about 80 K with liquid nitrogen flowing through natural circulation in a pipe 7 that is metallurgically integrated with the holder by brazing or the like. The back heat shield plate 33 and side heat shield plate 34 made of metals such as stainless steel, copper, and aluminum are also liquid nitrogen flowing through natural circulation inside the piping 7, which is metallurgically integrated by brazing or the like. It is cooled to a temperature of about 80K. The louver holder 32 is fixed to a holder plate 35, and the holder plate 35 is supported at a predetermined position on the back heat shield plate 33 with bolts or the like.

As shown in FIG. 4, the cryopanel 22 is supported between the front heat shield plate 30 and the back heat shield plate 33 via spacers 36 and 37 made of a material with low thermal conductivity such as epoxy resin. has been done. A part of the sub cryopanel 22 at the location where the louver holder 32 is arranged is cut out so that it does not come into contact with the louver holder 32.
It is in the shape of a strip. The cryopanel 22 and sub-cryopanel 28, which are at an extremely low temperature of 4.5K or less, are directly connected to the louver 29, front heat shield plates 30, 31, louver holder 32, back heat shield plate 33, and side heat shield plate 34, which have a temperature of approximately 80K. placed so that they do not touch each other.

FIG. 5 is a cross-sectional perspective view of one cryopanel 22, and the sub-cryopanel 28 is divided at a predetermined pitch in the longitudinal direction of the cryopanel. A louver holder is placed between the divided intervals R. With this structure, the tip of the sub cryopanel 28 can be installed close to the end 29a of the louver 29 without coming into contact with the louver holder 32.

According to this embodiment, gas molecules incident from the pump inlet face hit the front heat shield plates 30, 31, the rear heat shield plate 33, the louver 29, and the louver holder 32, and can pass through the louver 29 while being repeatedly reflected. Gas molecules that entered the cryopanel at an angle of incidence are exhausted. Gas molecules hit the surface of the louver, heat shield plate, and louver holder at least once, and then (1) collide with the cryopanel and sub-cryopanel, (2) hit the back side of the upper louver, or (3) exit the louver. It depends on whether it will be returned or not. However, by arranging the sub cryopanel on the back side of the louver, the gas molecules (2) can collide with the sub cryopanel and this gas can be exhausted.

The sub-cryopanel 28 is arranged so that it extends to the tip 29a of the louver on the back side of the large louver 29 within a range where it is not directly hit by the light beam, so that the probability of capturing gas molecules is increased. That is, if the gas exhaust speed when there is no sub-cryopanel is 100, the gas exhaust speed when the sub-cryopanel is arranged on the back side of the louver is 130, which significantly increases the exhaust speed.

Furthermore, since the louver holder 32 is integrated with the cooling pipe 7 through which liquid nitrogen flows to cool the louver 29, the louver holder 32 is cooled to approximately 77K, which is the temperature of the refrigerant. Therefore, the louver 29 integrated with the louver holder 32 by soldering or the like is efficiently cooled, and the temperature of the louver 29 becomes approximately 80K. Therefore, the amount of heat that enters the cryopanel and sub-cryopanel from the louver by radiant heat can be minimized.

Furthermore, according to this embodiment, as shown in FIG. 2, one unit can be constructed by combining the cryopanel 22, two sets of louver blinds arranged on both sides thereof, and the back heat shield plate 33. Therefore, thermal deformation of one unit, which occurs due to temperature non-uniformity between each unit during cool-down of the cryopump, can be prevented from deforming other units, thereby preventing heat leakage due to contact between the louver and the cryopanel. or parts of the cryopump will not be destroyed. Additionally, the position and arrangement of the cryopanel and louvers can be adjusted for each unit, making assembly of the entire cryopump easier.

Another embodiment of the invention is shown in FIG. In this embodiment, the cooling pipe 7 is metallurgically integrated with the louver holder 32 deeper than the half position in the depth direction of the cryopump where the back heat shield plate 33 is located. Exhaust gas molecules colliding with the cooling pipe 7 have a high probability of being reflected and flowing out of the cryopump. This is because if there is no cooling pipe, the probability that gas molecules will collide with the cryopanel and the sub-cryopanel increases. Therefore, the pumping speed of the cryopump increases when there is no cooling pipe. However, the probability of gas molecules colliding with the cryopanel and sub-cryopanel also differs depending on the location of the cooling tubes. That is, the probability that gas molecules reflected by colliding with a louver or louver holder near the entrance of the cryopump will flow out of the cryopump is higher than that of gas molecules reflected deep inside the cryopump. On the other hand, since the louver holder needs to be cooled more uniformly by the cooling pipe, it is better to arrange the cooling pipe in the longitudinal center of the louver holder. Therefore, as in this embodiment, by arranging the cooling pipe on the back side of the cryopump from the central portion, there is an effect of increasing the pumping speed of the cryopump.

[0027]

According to the present invention, the sub cryopanel extended from the cryopanel is arranged on the back side of the louver, and the sub cryopanel is made into a strip in order to avoid contact with the louver holder holding a plurality of louvers. Because it is shaped like this, the secondary cryopanel can be placed on the back side of the louver, extending all the way to the tip of the louver without being directly hit by the light beam, increasing the probability of capturing gas molecules and increasing the pumping speed of the cryopump. In addition, the cryopump can be made smaller.

Furthermore, since the louver holder is integrated with a cooling pipe through which a refrigerant for cooling the louver flows, the louver holder is cooled to a temperature close to that of the refrigerant. Therefore, the louver integrated with the louver holder by soldering or the like is efficiently cooled, and the temperature of the louver becomes close to the temperature of the refrigerant. Therefore, the amount of heat that enters the cryopanel and sub-cryopanel from the louver by radiant heat can be minimized.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a cryopump cooling system according to an embodiment of the present invention.

FIG. 2 is a top cross-sectional view of a cryopump that is a combination of cryopump units according to an embodiment of the present invention.

FIG. 3 is a perspective view of a cryopump unit used in the present invention.

FIG. 4 is a sectional view for explaining a spacer mounting structure used in the present invention.

FIG. 5 is a perspective view of a cryopanel used in the present invention.

FIG. 6 is a top sectional view of a cryopump unit according to another embodiment of the present invention.

[Explanation of symbols]

1... Cryopump, 3... Cryopump unit, 2
2... Cryopanel, 28... Deputy cryopanel, 29...
Louver, 32...louver holder.

Claims (5)

[Claims] 1. A cryopump consisting of a cryopanel cooled to an extremely low temperature that solidifies and adsorbs gas molecules, and a radiant heat shield plate cooled to a low temperature that protects the cryopanel from radiant heat from high temperatures. A cryopump characterized in that a sub cryopanel integrated with the cryopanel arranged parallel to the arrangement of the louvers of the shield is disposed on the back side of the louver, and the sub cryopanel is divided in the longitudinal direction of the cryopanel. . 2. A cryopump comprising a cryopanel cooled to an extremely low temperature that solidifies and adsorbs gas molecules, and a radiant heat shield plate cooled to a low temperature that protects the cryopanel from radiant heat from high temperatures. A louver holder that holds the louver by disposing a sub cryopanel integrated with the cryopanel arranged parallel to the arrangement of the louvers of the shield on the back side of the louver, and dividing the sub cryopanel in the longitudinal direction of the cryopanel. A cryopump that is characterized by being placed in a divided part. 3. A cryopump comprising a cryopanel cooled to an extremely low temperature that solidifies and adsorbs gas molecules, and a radiant heat shield plate cooled to a low temperature that protects the cryopanel from radiant heat from high temperatures. A louver holder that holds the louver by disposing a sub cryopanel integrated with the cryopanel arranged parallel to the arrangement of the louvers of the shield on the back side of the louver, and dividing the sub cryopanel in the longitudinal direction of the cryopanel. A cryopump characterized in that a cooling pipe is metallurgically integrated with the louver holder, and a cooling pipe is metallurgically integrated with the louver holder. 4. The cryopump according to claim 3, wherein a cooling pipe is metallurgically integrated at a deeper part of the louver holder than a half position in the depth direction of the cryopump. 5. A cryopump comprising a cryopanel cooled to an extremely low temperature for coagulating and adsorbing gas molecules, and a radiant heat shield plate cooled to a low temperature protecting the cryopanel from radiant heat from high temperatures, one or two cryopanels. A single cryopanel including a louver blind type radiant heat shield and a sub-cryopanel is placed in a predetermined position, and a fixing means for holding them constitutes one unit, and multiple units are assembled without being connected together in the longitudinal direction. A cryopump is characterized in that the pump is constructed by arranging the units in parallel and combining this unit group with another heat shield plate.