JPS61215472A - Exhaust face structure of cryo adsorption pump - Google Patents

Abstract

PURPOSE:To hold and cool the adsorbing member reliably by holding plural supporting tubes between upper and lower headers while fitting many adsorbing members into respective supporting tube then flowing the refrigerant from one of said header through the supporting tube and discharging through the other header. CONSTITUTION:A refrigerant injection tube 15 is coupled to the lower header 14 while a refrigerant discharge tube 17 is coupled to the upper header 16. A plurality of metal supporting tubes 18 are arranged while juxtaposing between said headers 14, 16 to be held by them 14, 16. Many granular adsorbing members 19 are fitted in respective supporting tube 18 to be contacted tightly each other. Furthermore, a shevron buffle 21 and a radiation shield 22 are arranged while surrounding respective adsorbing member 19. In other word, said buffle 21 is arranged to hold respective supporting tube 18 along the arranging direction of respective supporting tube 18 while said shield 22 is arranged around the supporting tubes 18 at the opposite ends.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a cryopump used in ultra-high vacuum equipment, nuclear fusion equipment, etc. This article relates to the exhaust surface structure of a cryo-adsorption pump.

[Technical background of the invention and its problems]

FIG. 4 shows a vacuum evacuation system using a conventional cryo-adsorption pump.
It is connected to the. The cryo-adsorption pump 4 housed in the cryopump chamber 3 has a metal surface 5 (hereinafter referred to as the cryo-surface) that is cooled to an extremely low temperature with a refrigerant liquid such as liquid helium, and a cryo-adsorption pump 4 that An adsorbent 6 such as activated carbon or molecular sheep attached with an adhesive such as epoxy resin, a Shearon baffle 7 placed in front of the cryo surface 5 and cooled with a cooling liquid such as liquid nitrogen, and a cryo surface 5 and an adsorbent 6, and a radiation shield plate 8 that is cooled by the cooling liquid 1. The cryopump chamber 3 is connected to an auxiliary vacuum pump 10 via another exhaust pipe 9. This auxiliary vacuum pump 10
Generally, mechanical pumps such as turbomolecular pumps and oil rotary pumps are used.

In advance, the inside of the cryopump chamber 3 is brought into a high vacuum state by the auxiliary vacuum pump 10 for vacuum insulation, and then the refrigerant liquid is supplied to the cryo-adsorption pump 4, and the molecules of the gas to be pumped from the object to be pumped 1 are absorbed by the adsorbent 6. Adsorb and exhaust. The cryo-adsorption pump is regenerated when the operation of the exhaust object 1 is stopped. That is, the supply of the refrigerant liquid is cut off, the temperature of the cryosurface 5 and the adsorbent 6 is increased, and the adsorbed gas molecules are separated from the adsorbent 6 and are exhausted to the outside by the auxiliary vacuum pump 10.

FIG. 5 is an enlarged view of the junction between the cryo surface 5 and the adsorbent 6 in FIG. An organic adhesive 13 such as epoxy resin is applied to the surface 5.
An adsorbent 6 is adhered.

However, when a cryo-adsorption pump is used in a nuclear fusion device, it receives high-energy neutrons generated by the fusion reaction, and the fuel gas it adsorbs and exhausts contains tritium, a radioactive substance. Adhesives made of organic materials such as epoxy resins whose performance deteriorates when exposed to radiation are unsuitable as adhesives for adsorbents.

Therefore, instead of the above-mentioned organic adhesive, an alloy of silver and tin, which are low melting point metals, is used, and an adsorbent is attached to this alloy by welding.
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This is proposed in the middle paragraph of the left column on page 1133 of 981.

However, this method has the drawback of poor workability since the alloy is heated and melted for adhesion, and also has the drawback that adsorption is weak and the adsorbent is easily peeled off by some vibration or impact.

In particular, this peeling of the adsorbent reduces the pumping speed of the pump due to a decrease in the surface area of the adsorbent on the cryo surface, and there is also a risk that the auxiliary vacuum pump may be damaged by suction of the peeled adsorbent.

Furthermore, even when the above-mentioned organic adhesive or low melting point metal is used, there is a problem in that the adsorbent is cooled from the cryoplane through them, so that cooling takes a long time.

[Purpose of the invention]

Therefore, an object of the present invention is to release tI4I! An object of the present invention is to provide an exhaust surface structure for a cryo-adsorption pump that can rapidly cool an adsorbent and firmly hold it without deteriorating its performance even when exposed to irradiation.

[Summary of the invention]

In order to achieve this object, the present invention includes a plurality of support tubes sandwiched between an upper header and a lower header, and a plurality of support tubes having a through hole and fitted onto the outer periphery of the support tubes through the through hole. The refrigerant liquid is provided with a small particulate adsorbent, and is characterized in that the refrigerant liquid flows in from one of the two headers and flows out from the other one of the headers through the support tube.

(Embodiment of the Invention) An embodiment of the exhaust surface structure of a cryo-adsorption pump according to the present invention will be explained below with reference to !!l1ii.

In FIG. 1, an injection pipe 15 for refrigerant such as liquid helium is connected to the lower header 14.
A refrigerant liquid discharge pipe 17 is connected to the upper header 16 facing the upper header 16 . Between the lower header 14 and the upper header 16 are a plurality of metal support tubes 18.18 juxtaposed with each other.
．． ... are arranged and held between both headers 14 and 16.

In FIG. 1, only the left end and right end support tubes are shown to avoid complication of the drawing. These support tubes 18
,18. . . are end portions that are fixed to the lower header 14 and the upper header 16 by brazing or the like, respectively, and communicate the inside of the lower header 14 and the inside of the upper header 16. A large number of small adsorbent particles 19 are fitted into each support tube 18 so as to be in close contact with each other. These adsorbents 19 have a cylindrical shape as shown in FIG. 2, and the diameter of the through hole 20 at the center of the cylinder is set to maximize the contact area between the inner circumferential surface of the cylinder and the outer circumferential surface of the support tube 18. Therefore, support tube 18
The diameter is set to be approximately the same as or slightly larger than the outer diameter of the

FIG. 3 is a cross-sectional view taken along the line ■-■ in FIG.
2 are arranged. chevron baffle 21.21
are arranged to sandwich the support tubes along the direction in which the support tubes 18° 18, . . . are lined up, and the radiation shields 22 are arranged around the support tubes at both ends.

The cryo-adsorption pump configured in this way is vacuum insulated and then fitted with chevron baffles 21, 21 and radiation shield 2.
2.22 is cooled with liquid nitrogen, and then the refrigerant liquid is injected into the lower header 14 from the injection pipe 15 as shown by the arrow in FIG. Emit more. Since the support tube 18 is directly cooled by the refrigerant liquid, it rapidly becomes extremely low temperature, and accordingly, the adsorbent 19 is also rapidly cooled to adsorb and exhaust gas molecules to be exhausted.

The outer shape of the adsorbent 19 is not limited to the circular shape shown in FIG. 2, but may be various shapes such as a rectangle, square, semicircle, or triangle. Similarly, the through holes 18 of the adsorbent 17 are not limited to a circular cross section, and various shapes can be selected, but it goes without saying that a shape that can increase the contact area with the support tube 16 is preferable.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, since the adsorbent is fitted onto the outer periphery of the support tube, it is reliably and firmly supported by the support tube, and the adsorbent can be prevented from falling off.

In this way, it is possible to avoid a decrease in the pumping speed due to the adsorbent falling off and a problem with the auxiliary vacuum pump.

Further, since the adsorbent can be supported without using an organic adhesive whose performance deteriorates due to radiation irradiation, problems caused by the use of such an adhesive do not occur. Furthermore, the refrigerant liquid flows through the support tube, and the adsorbent is directly cooled by the support tube.
Cooling time of adsorbent can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the exhaust surface structure of a cryo-adsorption pump according to the present invention, FIG. 2 is a perspective view showing the adsorbent shown in FIG. 1, and FIG. 3 is a Fig. 4 is a schematic diagram showing a vacuum evacuation device using a conventional cryo-adsorption pump, and Fig. 5 is an enlarged sectional view showing the evacuation surface structure of the cryo-adsorption pump shown in Fig. 4. . 14...Lower header, 16...Upper header, 18.
...Support tube, 19...Adsorbent.

Claims (1)

[Claims] 1. A plurality of support tubes sandwiched between an upper header and a lower header, and a large number of small particles having a through hole and fitted onto the outer periphery of the support tube through the through hole. and an adsorbent,
An exhaust surface structure for a cryo-adsorption pump, characterized in that a refrigerant liquid flows in from one of the two headers and flows out from the other one of the two headers through the support tube. 2. Pump exhaust surface structure according to claim 1, wherein the plurality of adsorbents have a cylindrical shape.