JP3969500B2 - Cold trap using pulse tube refrigerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold trap using a pulse tube refrigerator. The cold trap is usually disposed between the vacuum vessel and the vacuum exhaust device, and is used for the purpose of solidifying and removing moisture contained in the exhausted gas.
[0002]
[Prior art]
FIG. 2 shows a cross-sectional view of a cold trap using a Gifford-McMahon type refrigerator (GM refrigerator).
[0003]
A vertical gas flow path 56 in the figure is defined by a cylindrical flow path outer wall 50 having flanges at both upper and lower ends. A refrigerator support pipe 51 extending in the radial direction is attached to the side wall of the flow path outer wall 50. The high temperature end 53 of the GM refrigerator 52 is attached to the tip of the refrigerator support tube 51 via a flange. The cylinder portion of the GM refrigerator 52 is disposed in the internal cavity of the refrigerator support pipe 51, and the low temperature end 54 is supported in the gas flow path 56. A cylindrical cooling plate 55 is fixed to the low temperature end 54. Thus, the cooling plate 55 is supported in the gas flow path 56 by the GM refrigerator 52.
[0004]
FIG. 3 shows a cross-sectional view of a cold trap using a pulse tube refrigerator.
A gas flow path 68 in a direction perpendicular to the drawing sheet is defined by the cylindrical flow path outer wall 60. The regenerator 61, the cold head 62 and the pulse tube 63 constitute a pulse tube refrigerator 70. The regenerator 61 and the pulse tube 63 are arranged substantially in parallel, and one end of each is connected to the cold head 62. The cold head 62 is disposed in the flow path 68, and the other ends of the regenerator 61 and the pulse tube 63 are fixed to the flow path outer wall 60 and thermally coupled to the radiator 64.
[0005]
A cylindrical cooling plate 66 is disposed in the flow path 68 substantially coaxially with the flow path outer wall 60. The cooling plate 66 is supported by a support arm 65 extending from the cold head 62 in the radial direction of the flow path outer wall 60, and is thermally coupled to the cold head 62. The regenerator 61 and the pulse tube 63 pass through a through hole 67 provided in the cooling plate 66.
[0006]
[Problems to be solved by the invention]
In the cold trap shown in FIG. 2, a GM refrigerator is used. Since the GM refrigerator has a displacer that reciprocally vibrates, it becomes a source of vibration. This vibration may adversely affect the vacuum system including the vacuum processing chamber and the vacuum exhaust device.
[0007]
Further, in the cold trap shown in FIGS. 2 and 3, the cooling plate is supported by a cantilever support structure including a cylinder portion of a GM refrigerator or a regenerator and a pulse tube of a pulse tube refrigerator. For this reason, support tends to become unstable. The tube walls constituting the cylinder, the regenerator, and the pulse tube are thinned to reduce the amount of heat penetration from the high temperature end to the low temperature end. Therefore, it is not preferable to increase the support strength by thickening the tube wall of these tubes.
[0008]
An object of the present invention is to provide a cold trap with low vibration and high support strength of a cooling plate.
[0009]
[Means for Solving the Problems]
According to one aspect of the present invention, there is provided a pulse tube refrigerator in which a flow path outer wall that defines a flow path through which a gas flows, a regenerator, a cold head, and a pulse tube are connected in this order. And the pulse tube are arranged on opposite sides of the cold head, and ends opposite to the cold head side of the regenerator and the pulse tube are respectively attached to different positions on the outer wall of the flow path. A cold having a pulse tube refrigerator having a head supported in the flow path by the regenerator and a pulse tube, and a cooling plate disposed in the flow path and thermally coupled to the cold head A trap is provided.
[0010]
The cooling plate is cooled by the pulse tube refrigerator. The gas flowing in the flow path is cooled, and the gas cooled below the liquefaction point is trapped on the cooling plate. The regenerator and the pulse tube are arranged on opposite sides of the cold head, and both ends of the pulse tube refrigerator are fixed to the outer wall of the flow path. For this reason, compared with the case where a refrigerator is supported by a cantilever structure, it becomes possible to support more stably.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic cross-sectional view of a cold trap according to an embodiment of the present invention. 1A corresponds to a cross-sectional view taken along one-dot chain line A1-A1 in FIG. 1B, and is a cross-sectional view perpendicular to the direction of gas flow. FIG. 1B corresponds to a cross-sectional view taken along one-dot chain line B1-B1 in FIG. 1A, and is a cross-sectional view parallel to the direction of gas flow.
[0012]
A flow path 2 is defined by a cylindrical flow path outer wall 1. The flange at one end of the flow path outer wall 1 is connected to a vacuum vessel (not shown), and the flange at the other end is connected to a vacuum exhaust device such as a turbo molecular pump.
[0013]
A pulse tube refrigerator 10 is configured including the refrigerant gas introduction unit 11, the regenerator 12, the cold head 13, the pulse tube 14, and the radiator 15. The regenerator 12 is configured by filling a regenerator material in a stainless steel hollow tube. As the cold storage material, for example, a disk-shaped stainless steel mesh or copper mesh is used. The pulse tube 14 is constituted by a hollow tube made of stainless steel, for example.
[0014]
A cold head 13 is connected to one end of the regenerator 12, and the refrigerant gas introduction part 11 is connected to the other end. A cold head 13 is connected to one end of the pulse tube 14, and a radiator 15 is attached to the other end. The regenerator 12 and the pulse tube 14 are disposed on opposite sides of the cold head 13 and along a substantially straight line.
[0015]
The cold head 13 is configured by a hollow box made of oxygen-free copper, for example, and distributes the working gas between the regenerator 12 and the pulse tube 14. The cold head 13 has fins or copper mesh inside, and can effectively exchange heat with the working gas flowing inside.
[0016]
An end of the regenerator 12 on the refrigerant gas introduction part 11 side and an end of the pulse tube 14 on the radiator 15 side are respectively attached and fixed at positions facing the flow path outer wall 1. The cold head 13 is supported by the flow path outer wall 1 via the regenerator 12 and the pulse tube 14, and is disposed on the central axis of the flow path 2.
[0017]
A cylindrical copper cooling plate 20 is disposed in the flow path 2 concentrically with the flow path outer wall 1. The cooling plate 20 is provided with through holes 22 and 23 at positions corresponding to the regenerator 12 and the pulse tube 14, respectively, so that the cooling plate 20 does not contact the regenerator 12 and the pulse tube 14. . The cooling plate 20 is thermally and mechanically coupled to the cold head 13 by a plurality of copper support plates 21 extending from the cold head 13 in the radial direction of the flow path outer wall 1, and is supported in the flow path 2. Yes. The support plate 21 is fixed to the cold head 13 by brazing.
[0018]
The refrigerant gas introduction unit 11 is connected to the compressor 30, and the compressor 30 repeatedly introduces and collects compressed gas such as helium. The refrigerant gas compressed in the regenerator 12 is supplied in a half cycle in which the compressed gas is supplied from the compressor 30.
[0019]
When a certain high-pressure gas is allowed to flow into the insulated pulse tube 14, the internal temperature rises. At this time, if the flow of the inflowing gas is a one-way flow, a temperature gradient is formed along the flow, and the temperature is highest at the high-temperature end of the pulse tube (end on the radiator 15 side). The gas initially in the regenerator 12 is adiabatically compressed and moves into the pulse tube 14 where it provides heat to the pulse tube wall. Further, the gas in the pulse tube 14 also moves to the high temperature end, where heat is applied to the radiator 15 and the gas itself is cooled.
[0020]
In the other half cycle, the refrigerant gas in the regenerator 12 is recovered by the compressor 30. The gas in the pulse tube 14 moves in the opposite direction to the compression process. At this time, cooling occurs due to adiabatic expansion, and the gas receives heat from the pulse tube wall. Some gas returns into the regenerator 12 and receives heat from the regenerator material. That is, the gas cools the regenerator material.
[0021]
Therefore, in the next compression process, the gas flowing into the pulse tube 14 is first pre-cooled by the cold storage material, so that a temperature lower than that in the first compression process is obtained. As described above, when the supply of the refrigerant gas from the compressor 30 into the regenerator 12 and the recovery of the refrigerant gas from the regenerator 12 to the compressor 30 are repeated, the refrigerant gas is kept at a low temperature end while maintaining a constant temperature gradient in the pulse tube. Part (cold head 13 parts) heat to the high temperature end. By forcibly removing the heat at the high temperature end with the radiator 15, a cooling effect can be obtained continuously at the low temperature end.
[0022]
The cold generated in the cold head 13 is transmitted to the cooling plate 20 through the support plate 21, and the cooling plate 20 is cooled. For example, a cold head can be cooled to 80-100K using a pulse tube refrigerator. A molecular flow flowing in the flow path 2 collides with the cooling plate 20, and water molecules and the like are trapped in the cooling plate 20.
[0023]
In FIG. 1, a straight tube type pulse tube refrigerator 10 having a cold head 13 at the center is used. Both ends of the pulse tube refrigerator 10 are fixed to the flow path outer wall 1 to support the cooling panel 20. Therefore, the cooling plate 20 can be supported more stably than in the case of the cantilever support structure shown in FIGS.
[0024]
In addition, the cold head 13 is disposed substantially on the central axis of the flow path 2. The cooling plate 20 and the support plate 21 are configured to be substantially rotationally symmetric with respect to the cold head 13. For this reason, it becomes possible to cool the whole cooling plate 20 substantially uniformly.
[0025]
Further, the pulse tube refrigerator 10 used in the above embodiment is a straight tube type, and has a different configuration from the U-shaped pulse tube refrigerator shown in FIG. By making the pulse tube refrigerator straight, the pressure loss and drift due to the bending of the refrigerant gas flow can be suppressed, and the cooling efficiency can be increased.
[0026]
In the above-described embodiment, the case where the straight tube type pulse tube refrigerator is arranged so as to intersect with the central axis of the flow path is described, but it is not always necessary to intersect with the central axis of the flow path. For example, if the diameter of the cross section of the flow path is longer than the length of the pulse tube refrigerator, support both ends of the pulse tube refrigerator at positions that are biased to one side, not at the opposite positions across the central axis. May be.
[0027]
Further, the cross section of the flow path is not necessarily circular, and may be any shape. In this case as well, stable support is possible by supporting the straight tube type pulse tube refrigerator at both ends thereof.
[0028]
In the above embodiment, the case where the pulse tube refrigerator is a straight pipe type has been described, but the shape thereof does not have to be strictly linear. For example, it is good also as a shape along the circumference which has a certain curvature, and it is good also as a shape along another curve. For this curve, it is preferable to select a suitable shape according to the cross-sectional shape of the flow path. In this case as well, stable support will be possible by fixing both ends of the pulse tube refrigerator at different positions on the outer wall of the flow path.
[0029]
In addition, the pulse tube refrigerator does not have a movable part like the displacer of the GM refrigerator. For this reason, generation | occurrence | production of the vibration from a cold trap can be suppressed.
[0030]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0031]
【The invention's effect】
As described above, according to the present invention, the cooling plate attached to the cold head of the pulse tube refrigerator can be stably supported by fixing both ends of the pulse tube refrigerator to the outer wall of the flow path. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a cold trap according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing a cold trap using a conventional GM refrigerator.
FIG. 3 is a cross-sectional view schematically showing a cold trap using a conventional pulse tube refrigerator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Flow path outer wall 2 Flow path 10 Pulse tube refrigerator 11 Refrigerant gas introduction part 12 Regenerator 13 Cold head 14 Pulse tube 15 Radiator 20 Cooling plate 21 Support plates 22, 23 Through hole 30 Compressor

Claims (3)

A channel outer wall defining a channel through which gas flows;
A pulse tube refrigerator in which a regenerator, a cold head, and a pulse tube are connected in this order, and the regenerator and the pulse tube are arranged on opposite sides of the cold head, and the regenerator and the pulse tube The end of the tube opposite to the cold head side is attached to each of the flow channel outer walls at different positions, and the cold head is supported in the flow channel by the regenerator and the pulse tube. A tube refrigerator,
A cold trap having a cooling plate disposed in the flow path and thermally coupled to the cold head. The cold trap according to claim 1, wherein the regenerator, the cold head, and the pulse tube are arranged along a certain straight line. The cold trap according to claim 1 or 2, wherein the flow path outer wall has a cylindrical inner peripheral surface, and the cold head is supported on a central axis of the inner peripheral surface.

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