JP3019490B2 - Cryopump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryopump for exhausting gas at a high speed by condensing and adsorbing gas molecules on a cryopanel cooled at a very low temperature.

[0002]

2. Description of the Related Art A conventional cryopanel is disclosed in
As described in JP-A-968, 5.0K with liquid helium or the like
The following cryogenically cooled single flat cryopanel is perpendicular to the gas inlet face of the cryopump,
Multiple sheets are arranged. Liquid helium evaporates with little heat and is an expensive refrigerant. A heat shield cooled to about 80K with liquid nitrogen around the cryopanel so that this cryopanel is not directly heated by radiant heat from the normal temperature and high temperature area outside the pump in order to reduce the amount of liquid helium evaporated. Place the board.

The heat shield plates on both sides of the cryopump are louver blind type, and gas molecules to be exhausted pass through the gap of the louver and collide with a cryogenic panel at a very low temperature, where they are condensed and adsorbed.

[0004] The surface of the louver is blackened so as to absorb radiant heat, and an external light beam reaches the cryopanel after colliding with these heat shield plates at least once.

The gas molecules to be exhausted repeatedly strike the front heat shield plate adjacent to the front of the pump once or several times, while certain gas molecules flow away from the inlet of the pump,
Certain molecules reach the cryopanel and are coagulated and adsorbed.

[0006]

In the above prior art, since the cryopanel is arranged at a distance downstream of the louver, the gas molecules flowing away from the pump inlet during repeated collisions between the louvers are reduced. The probability of the number increasing increases. When this probability increases, there is a problem that the exhaust speed of gas molecules decreases.

However, a neutral particle injection device used in a recent large-scale fusion device requires a cryopump having a high pumping speed of hydrogen and deuterium. On the other hand, since the neutral particle injector is constituted by a vacuum vessel, the area and the volume of the beam facing surface of the cryopump installed inside are reduced. That is, it is important to reduce the manufacturing cost by reducing the size of the vacuum vessel by improving the performance and size of the cryopump.

It is an object of the present invention to optimize the structure of a cryopanel installed in a cryopump having the same volume to increase the pumping speed of the cryopump and minimize the amount of radiant heat entering the cryopanel cooled to a cryogenic temperature. The purpose of the present invention is to reduce the amount of evaporation of liquid helium by reducing the size.

[0009]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The first feature of the present invention is that an electrode for coagulating and adsorbing gas molecules
A cryopanel cooled to a low temperature, and the cryopanel
Radiant heat cooled to low temperature to protect the unit from radiant heat from high temperature
In a cryopump with a shield plate, a louver
Arrange the blind radiant heat shield in parallel with the louver arrangement.
Sub-cryopanel integrated with the placed cryopanel
On the back side of the louver, and turn on the cryopump.
The cross-sectional shape where the three sides of the Z-shape are perpendicular to each other
Place a louver with the L-shape in the back of the cryopump.
Or a louver having an I-shaped cross section,
Or a louver with an I-shaped cross section has two sides
Louver with a cross section perpendicular to the
The length of the side parallel to the tunnel is the length of the side perpendicular to the cryopanel.
Shorter side and parallel to the cryopanel.
Located on the IO panel side, the L-shaped or I-shaped cross section
The length of the side parallel to the cryopanel of the louver with
Parallel to the cryopanel of the Z-shaped louver and
The length of the side is shorter than the length of the side
The metal is metallurgically integrated with the louver holder and the cryopon
Cooling tube is metallurgically integrated with the louver holder at the front of the
It has become. A second feature of the present invention is that gas molecules are
A cryopanel cooled to an extremely low temperature to coagulate and adsorb,
Low temperature to protect the cryopanel from radiant heat from high temperature
Cooled radiant heat shield plate, louver blind radiant heat
Cryo with shield louver and louver holder
In the pump, the louver hole on the front of the cryopump
That the cooling pipe is metallurgically integrated with the heater.

[0010]

The gas molecules incident from the inlet face of the pump hit the heat shield plate and the louver, and are exhausted only when they enter the cryopanel at an angle of incidence that can pass through the louver while repeating reflection. The gas molecules hit the surface of the louver at least once, and then are divided into (1) hitting the cryopanel, (2) hitting the back surface of the upper louver, and (3) returning to the outside of the louver. Deputy cryopanel
Having the first feature described above, which is arranged on the back side of the server.
In the present invention the above (2) the gas molecules of claim collide with the sub Kupaiopaneru, it can <br/> Ru for exhausting the gas.

In the arrangement of the sub cryopanel, since the rear surface of the louver of each step extends to the tip of the louver within a range where direct light does not impinge, the probability of capturing gas molecules increases. On the other hand , in the vicinity of the entrance of the cryopump, a louver having a cross-sectional shape in which three sides of the Z-shape are perpendicular to each other is arranged, and an L-shape or an I-shape in which two sides are perpendicular to each other is provided at the back of the cryopump. A louver having the cross section of the mold is placed. Due to this louver arrangement, most of the gas molecules that have entered the inner part of the cryopump collide with and reflect on the louver having the L-shaped or I-shaped cross section, and collide with the louver having the Z-shaped cross section. , It reaches the cryopanel with a higher probability than when it is reflected and is exhausted.

Further, the sub cryopanel is arranged near the gas inlet of the cryopump and not at the back of the cryopump. This is because the flight trajectory of the gas molecules was obtained by numerical simulation, and as a result, most of the gas molecules were condensed and coagulated and exhausted to the sub cryopanel arranged near the entrance of the cryopump, and the sub cryopump arranged at the back of the cryopump Almost no gas molecules reach the cryopanel. Therefore, even if the sub cryopanel is not arranged at the back of the cryopump, the pumping speed hardly decreases, and by reducing the number of sub cryopanels cooled to extremely low temperatures and reducing the surface area of the entire sub cryopanel, The amount of radiant heat entering the cryogenic temperature is greatly reduced.

The present invention having the first and second features described above.
In the Ming, cooling pipes through which the refrigerant that cools the louvers flows
To the front of the louver holder in a metallurgical manner, such as by soldering.
The louver holder cools down to near the temperature of the refrigerant and is placed on the front of the louver holder.
Efficient cooling of louvers integrated by soldering etc.
Wear. On the other hand, the radiant heat from the room often entering the louver of the cryopump front portion. Therefore, according to the present invention
For example, from the louver to the cryopanel (or vice cryopanel)
) Can be suppressed to a small amount of heat entering by radiant heat.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a configuration example of a cryopump cooling system. The cryopump 1 is disposed in a vacuum vessel 2 such as a neutral particle injector or a space chamber of a fusion device. The cryopump 1 is a single unit 3 or
A plurality of unit groups 3 are configured together. Each unit 3
Communicates with the liquid helium upper tank 4 and the liquid nitrogen upper tank 5 through the pipes 6 and 7 and the unit 3
Is communicated with the liquid helium lower tank 8 and the liquid nitrogen lower tank 9 via the pipes 10 and 11.

The liquid helium 12 is a helium liquefier 1
3 and supplied to the liquid helium upper tank 4 by 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.
Are communicated through. The helium gas heated and evaporated by the cryopump 1 is supplied to the liquid helium upper tank 4.
And returns to the helium liquefaction apparatus through the helium gas recovery pipe 16 and is again liquefied.

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

FIG. 2 is a top sectional view of a cryopump in which three units are combined, and FIG. 3 is a bird's-eye view of the two units.

The cryopanel 22 for condensing and coagulating and trapping the exhaust gas is generally made of stainless steel , copper, or copper.
The metal plates 23, 24 such as aluminum, fins 27 in a flow path surrounded by the side plates 25 and 26 which was brazed, which are integrally metallurgically. The plates 23 and 24, manufacturing operation was uneven stainless steel extrusion molding, copper, or a metal secondary cryopanel 28 such aluminum near an entrance of the cryopump integrated metallurgically by brazing or the like I have. In the cryopanel, liquid helium flows through the pipes 6 and 7 by natural circulation, and the cryopanel and the sub cryopanel are cooled to an extremely low temperature of 4.5K or less.

On the other hand , it is made of metal such as stainless steel , copper or aluminum which is arranged near the entrance of the cryopump .
And louvers 29a having a cross-sectional shape three sides by Z-shape at right angles to each other, the louvers 29c having an L-shaped or I-shaped cross section disposed in the inner part of the cryopump, and Pong
The front heat shield plates 30, 31 arranged on the front surface of the loop are combined with the louver holder 32 in a comb shape, and the combined portion is metallurgically integrated by brazing or the like. L-or louvers 29c having an I-shaped cross section is a cross-sectional shape in which two sides at right angles to each other louver, the length of the sides parallel to the cryopanel of the two sides of the perpendicular edges to the cryopanel A side shorter than the length and parallel to the cryopanel is arranged on the cryopanel side. The length of the side parallel to the cryopanel of the louver 29c having the L-shaped or I-shaped cross-section is parallel to the cryopanel of the Z-shaped louver 29a and is disposed on the cryopanel side. Shorter than the side length.

The louver holder 32 is cooled to a temperature of about 80 K by liquid nitrogen flowing by natural circulation in a pipe 7 metallurgically integrated with the holder by brazing or the like. Similarly, the rear heat shield plate 33 and the side heat shield plate 34 made of metal such as stainless steel, copper, or aluminum are also made of liquid nitrogen flowing in the metallurgically integrated pipe 7 by brazing or the like by natural circulation. Cooled to a temperature of about 80K. Louver holder 32
Is fixed to a holder plate 35, and the holder plate 35 is supported by a bolt or the like at a predetermined position on the rear heat shield plate 33.

As shown in FIG. 4, the cryopanel 22 is supported between the front heat shield plate 30 and the rear heat shield plate 33 via spacers 36 and 37 made of a material having a low thermal conductivity such as epoxy resin. Have been. The sub cryopanel 22 at the position where the louver holder 32 is disposed has a strip shape in which a part of the panel is cut out so as not to contact the louver holder 32. The extremely low temperature cryopanel 22 and the sub cryopanel 28 having a temperature of 4.5K or less are composed of louvers 29a and 29c, front heat shield plates 30 and 31, louver holder 32 and rear heat shield plate 3 having a temperature of about 80K.
3, it is arranged so as not to directly contact the side heat shield plate 34.

FIG. 5 is a bird's-eye view of one section of the cryopanel 22. The sub cryopanel 28 is divided at a predetermined pitch in the longitudinal direction of the cryopanel. The louver holder is arranged between the divided intervals R. With this structure, the tip of the sub cryopanel 28 can be installed close to the end portion 29b of the louver 29a without contacting the louver holder 32. The entire surface of the louver facing the pump inlet is blackened, and the back surface is made of a material or aluminum to reduce the emissivity.

According to this embodiment, gas molecules incident from the inlet face of the pump strike the front heat shield plates 30 , 31 , the rear heat shield plate 33 , the louvers 29a, 29c, the louver holder 32, etc. , and are repeatedly reflected. Meanwhile, gas molecules that have entered the cryopanel at an incident angle that allows them to pass through the louvers 29a and 29c are exhausted. The gas molecules hit the surface of the louver, the heat shield plate, and the louver holder at least once, and then (1) collide with the cryopanel or the sub cryopanel, (2) hit the back surface of the upper louver, or (3) out of the louver. Divided back to. But,
By placing the louver rear surface side sub cryopanel, (2) the gas molecules of claim collide with the sub Kupaiopaneru, Ru can be evacuated this gas.

In the arrangement of the sub cryopanel 28, the rear surface of the louvers 29a and 29c in each step is extended to the louver tip 29b within a range where direct rays do not hit, so that the probability of capturing gas molecules increases.

The L-shaped or I-shaped louver 29c disposed at the back of the cryopump is a Z-shaped louver 2c.
9a, the opening surface in the direction perpendicular to the cryopanel surface is larger and the probability of gas molecules passing through the louver is higher. Therefore, the exhaust speed of the cryopump is higher than that of disposing the Z-shaped louver 29a to the inner part of the cryopump. That is, assuming that the gas exhaust speed in the case where the Z-shaped louver 29a is arranged to the back of the cryopump is 100, the gas exhaust speed in the case where the L- or I-shaped louver 29c is arranged in the back of the cryopump is At 140, the pumping speed is greatly increased.

The louver holder 32 holds the louver 29
Since the liquid nitrogen for cooling the cooling pipes a, 29b and 29c is integrated with the cooling pipe 7 flowing inside and the front surface of the louver holder 32 by soldering or the like, it is cooled to a temperature close to 77K of the temperature of the refrigerant. Therefore, the louver 29 integrated with the louver holder 32 is efficiently cooled and the louver 29
Is about 80K. Therefore, the amount of heat entering the cryopanel and the sub cryopanel from the louver into the cryopanel and the sub-cryopanel can be minimized.

Further, according to this embodiment, as shown in FIG. 2, one unit can be constituted by combining the cryopanel 22, two sets of louver blinds arranged on both sides thereof, and the rear heat shield plate 33. Therefore, when the cryopump cools down, it is possible to prevent the thermal deformation of one unit that occurs due to the temperature non-uniformity between the units from deforming other units. It does not occur, nor does part of the cryopump break. Further, since the positions and arrangements of the cryopanel and the louver can be adjusted for each unit, assembly of the entire cryopump becomes easy.

In this embodiment, the cooling pipe 7 is metallurgically integrated with the louver holder 32 at the front of the cryopump in the depth direction of the cryopump having the rear heat shield plate 33. When the cooling pipe 7 is disposed inside the cryopump, the probability that the exhaust gas molecules that have collided with the cooling pipe 7 are reflected and flow out of the cryopump is increased. If there is no cold却管is cryopanel, the probability that gas molecules colliding Ru heightened the sub cryopanel. Therefore, the pump speed of the cryopump increases when there is no cooling pipe inside the cryopump. On the other hand , the amount of heat that enters the louver from the room temperature part by radiant heat is
Front heat shielding plate 30, 31 area arranged in a wide cryopump front face and, and louver group arranged near the
Great in part . Since the front heat shield plate and the louver need to be more uniformly cooled by the cooling pipe integrated with the louver holder, it is better to arrange the cooling pipe on the front face in the longitudinal direction of the louver holder. Therefore, by disposing the cooling pipe in the front part as in the present embodiment, there is an effect of increasing the pumping speed of the cryopump.

[0029]

According to the present invention having the first feature, a louver having a sectional shape in which three sides of a Z-shape are perpendicular to each other is arranged near the entrance of the cryopump having the sub cryopanel, since two sides in the back part of the cryopump not including the sub cryopanel is disposed louvers having an L-shaped or I-shaped cross-sectional shape at right angles to each other,
Due to this louver arrangement, most of the gas molecules that have entered the inner part of the cryopump collide with and reflect on the louver having the L-shaped or I-shaped cross section, and collide with the louver having the Z-shaped cross section. , It reaches the cryopanel with a higher probability than when it is reflected and is exhausted . As a result, the pumping speed can be increased, and the cryopump can be downsized.

Further, since the sub cryopanel is disposed near the gas inlet of the cryopump and is not disposed at the back of the cryopump, the amount of radiant heat entering the cryogenic temperature can be greatly reduced without substantially lowering the exhaust speed. Therefore, the amount of evaporation of liquid helium for cooling the cryopanel can be greatly reduced.

According to the present invention having the first and second features,
For example, a cooling pipe through which the heat shield plate and the refrigerant for cooling the louver flow inside is connected to a loop located at the front of the cryopump.
Metallurgically integrated with the holder by soldering etc.
The heat shield plate and louver close to the refrigerant temperature.
And can be cooled efficiently. Therefore, from the louver to the cryopa
Heat entering the flannel (or sub-cryopanel) by radiant heat
Since the amount can be kept small, the amount of evaporation of liquid helium for cooling the cryopanel can be greatly reduced. Further, there is an effect that can increase the pumping speed of the cryopump by arranging the cooling pipe to the front part of the cryopump.

[Brief description of the drawings]

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

FIG. 2 is a top sectional view of a cryopump in which three cryopump units according to one embodiment of the present invention are combined.

FIG. 3 is a bird's-eye view of two cryopump units used in the present invention.

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

FIG. 5 is a bird's eye view of one cryopanel used in the present invention.

[Explanation of symbols]

1: Cryopump, 3: Cryopump unit, 7
... Cooling pipe, 22 ... Cryo panel, 28 ... Sub cryopanel, 29a, 29c ... Louver, 32 ... Louver holder.

Continuing from the front page (72) Inventor Yasuo Yamashita 1-1-1, Kokubuncho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Kokubu Plant (58) Field surveyed (Int. Cl. ⁷ , DB name) F04B 37 / 08

Claims (2)

(57) [Claims] And 1. A cryopanel cooled to cryogenic temperature to solidify and adsorption of gas molecules, and the radiant heat shield plate cooled to a low temperature to protect the cryopanel from radiant heat from the hot
In the cryopump provided with, the sub cryopanel integrated with the cryopanel arranged in parallel with the louver arrangement of the louver blind type radiant heat shield is arranged on the back side of the louver, and Z near the entrance of the cryopump.
A louver having a cross-sectional shape in which three sides of the character shape are perpendicular to each other is disposed, and a louver having an L-shaped or I-shaped cross-sectional shape is disposed at the back of the cryopump. A louver having a cross-sectional shape of is a louver having a cross-sectional shape in which two sides are perpendicular to each other. The length of a side parallel to the cryopanel is shorter than the length of a side perpendicular to the cryopanel. The side parallel to the panel is arranged on the cryopanel side, and the length of the side parallel to the cryopanel of the louver having the L-shaped or I-shaped cross-section is parallel to the cryopanel of the Z-shaped louver. The louver is shorter than the length of the side arranged on the cryopanel side, and the louver is metallurgically integrated with the louver holder, and the cooling pipe is metallurgically integrated with the louver holder on the front portion of the cryopump. Class that is characterized by Oponpu. 2. A cryopanel cooled to cryogenic temperature to solidify and adsorption of gas molecules, the radiant heat shield plate cooled to a low temperature to protect against radiation heat of the cryopanel from the hot, louvers and louver holder louver blind radiation heat shield A cryopump comprising: a cryopump, wherein a cooling pipe is metallurgically integrated with a louver holder at a front portion of the cryopump.