JPS61215471A - Exhaust face structure of cryo adsorption pump - Google Patents

Abstract

PURPOSE:To cool the adsorbing material quickly and to hold firmly by providing a supporting rod along the metal face to be cooled cryogenically through refrigerant and penetrating many adsorbing members through the supporting rod while contacting tightly against the metal face. CONSTITUTION:Frame-like fixing section 14 is projected from the circumferential section of the underface or the cryo face 5 of a metal sump 12 for storing the refrigerant 11 then a supporting rod 15 is brazed in parallel to the cryo face 5 with predetermined interval. Plural number of supporting rods 15 are juxtaposed in parallel in the direction normal to the plane of drawing to be distributed entirely over the cryo face 5 while a tubular adsorbing member 17 having a through-hole 16 is inserted into respective supporting rod 15 to be contacted tightly against the cryo face 5. Consequently, droppage of the adsorbing member 17 from the supporting rod 15 can be prevented reliably resulting in prevention of droppage of discharging speed and damage of an auxiliary vacuum pump caused through droppage of the adsorbing material 17.

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) Figure 3 shows vacuum evacuation i using a conventional cryo-adsorption pump.
** Indicates that an object 1 to be evacuated, such as a vacuum vessel of a nuclear fusion device, is connected to a cryopump 3 via an exhaust pipe 2.
It is connected to the. This room 3
The cryo-adsorption pump 4 housed in the cryo-adsorption pump 4 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 an adhesive such as epoxy resin on the cryo-surface 5. An adsorbent 6 such as activated carbon or molecular sieve attached by an agent, a chevron baffle 7 placed in front of the cryo surface 5 and cooled by a cooling liquid such as liquid nitrogen, and a chevron baffle 7 surrounding the cryo surface 5 and the adsorbent 6. , and a radiation shield plate 8 cooled by the cooling liquid. The cryopump chamber 3 is connected to an auxiliary vacuum pump 10 via another exhaust pipe 9. As this auxiliary vacuum pump 10, a mechanical pump such as a turbo molecular pump or an oil rotary pump is generally 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 concentration of the cryosurface 5 and the adsorbent 6 is increased, the adsorbed gas molecules are separated from the adsorbent 6, and the auxiliary vacuum pump 10 exhausts them to the outside.

FIG. 4 is an enlarged view of the joint 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.
Adsorbent material 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, so it is exposed to radiation. Adhesives made of organic materials such as epoxy resins whose performance deteriorates when exposed to irradiation 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.
5science and technology
Vol 1 8, N113^pril198
It is proposed in the middle paragraph of the left column on page 1133 of 1. However, this method has the drawback of poor workability because the alloy is heated and melted for adhesion, and in addition, the adsorbent has a weak adhesion force and is easily peeled off by some vibration or shock.

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, the adsorbent is cooled from the cryoplane through them, so there is a problem that cooling takes a long time.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an exhaust surface structure for a cryo-adsorption pump that can rapidly cool and firmly hold an adsorbent without deteriorating its performance even when exposed to radiation. .

[Summary of the invention]

To achieve this objective, the present invention includes a metal surface that is cooled to a cryogenic temperature by a refrigerant liquid, a support rod that is provided along the metal surface and at a predetermined distance from the metal surface, and a through hole. A large number of small granular adsorbents are fitted onto the outer periphery of the support rod through the through holes, and these adsorbents are fitted into the support rod so as to be in close contact with the metal surface. It is characterized by this.

[Embodiments of the invention]

An embodiment of the exhaust surface structure of a cryo-adsorption pump according to the present invention will be described below with reference to FIGS. 1 and 2, in which the same parts as in FIGS. 3 and 4 are given the same reference numerals. .

In FIG. 1, the cryo surface 50m is the lower surface of the metal refrigerant reservoir 12 that stores the refrigerant 11 such as liquid nitrogen.
A frame mounting portion 14 is provided protruding from the portion. A braze is fixed to this mounting portion 14 so that a support rod 15 is parallel to the cryoplane 5 and at a predetermined distance therefrom. A plurality of such support rods 15 are arranged parallel to each other in a direction perpendicular to the plane of the paper, and are distributed over the entire surface of the cryoplane 5. A large number of cylindrical adsorbents 17 having through-holes 16 shown in FIG.

This adsorption material 17 is brought into close contact with the cryosurface 5, for example, in the following manner. That is, the mounting through-holes drilled in the mounting portion 14 are made into oval shapes extending in the vertical direction, the support rods 15 are passed through these mounting through-holes, and the adsorbent material 17 is inserted into the support rods 15 within the oval mounting holes. After moving upward until it comes into close contact with the cryo surface 5, the support rod 15 is fixed to the mounting portion 14 by brazing 18. In addition, the central through hole 1 of the adsorbent 17
In order to maximize the contact area between the through hole 16 and the support rod 15, the diameter of the support rod 6 is set to be approximately the same as or slightly larger than the outer diameter of the support rod 15.

A cryo-adsorption pump is constructed by surrounding such an exhaust surface structure with a chevron baffle and a radiation shield plate as shown in FIG.

After the cryo-adsorption pump is vacuum-insulated, the chevron baffle and radiation shield plate are cooled with liquid nitrogen, and then the refrigerant reservoir 12 is filled with the refrigerant liquid 11 to cool the cryo surface 5 to an extremely low temperature. As a result, the adsorbent 17 is directly cooled by the cryo-surface 5 that is in close contact with it, and at the same time is also cooled by the support rod 15 via the mounting portion 14 and brazing portion 18 of the cryo-surface 5, and adsorbs the exhaust gas molecules. Exhaust.

In the above embodiment, the adsorbent 17 has a circular outer shape, but the outer shape is not limited to this, and may be rectangular, square, semicircular, triangular, or the like. Furthermore, the support rod 15 may be fixed to the mounting portion 14 of the cryo surface 5 not only by brazing but also by welding, bolting, or the like.

〔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 rod, it is reliably and firmly supported by the support rod, and the adsorbent can be prevented from falling off. Therefore, it is possible to avoid a decrease in pumping speed and damage to the auxiliary vacuum pump due to adsorbent falling off. 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, since the adsorbent is in close contact with the cryo-surface, it is directly cooled by the cryo-surface and also cooled through the support rod, so that the cooling time can be significantly shortened.

[Brief explanation of drawings]

Fig. 1 is a vertical 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 of Fig. 1, and Fig. 3 is a conventional cryo-adsorption pump. FIG. 4 is an enlarged sectional view showing the evacuation surface structure of the cryo-adsorption pump shown in FIG. 3. 5... Metal surface (cryo surface), 11... Refrigerant liquid, 1
4... Attachment part, 15... Support rod, 16... Through hole, 17... Adsorbent.

Claims (1)

[Claims] 1. A metal surface cooled to an extremely low temperature by a refrigerant liquid, a support rod provided along the metal surface at a predetermined distance from the metal surface, and a through hole, A large number of small granular adsorbents are fitted onto the outer periphery of the support rod through holes, and these adsorbents are fitted into the support rod so as to be in close contact with the metal surface. Characteristic cryo-adsorption pump exhaust surface structure. 2. The support rod is fixed at both ends to a pair of attachment parts protruding from the metal surface, and the plurality of adsorbents are cylinders having the same shape.
Exhaust surface structure of the cryo-adsorption pump described in Section 1.