CN114823274A

CN114823274A - Ion pump for preventing metal gas poisoning

Info

Publication number: CN114823274A
Application number: CN202210209536.9A
Authority: CN
Inventors: 黄名山; 汪斌; 唐爽
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2022-07-29

Abstract

The ion pump capable of preventing metal gas poisoning has one additional design for preventing ion pump pollution in the output connecting pipeline. The invention can not only greatly reduce the metal gas entering the pump body, but also has no obvious influence on the pumping speed of the ion pump, thereby achieving the effects of isolating and protecting the ion pump, prolonging the service life of the ion pump and reducing the ion flow background of the ion pump. On the other hand, impurity particles generated during the operation of the sputtering ion pump are reduced from entering the target vacuum system, so that the vacuum degree of the target area can be higher. The device has simple structure and easy realization, and can be used as an air-extracting ion pump device needing an ultrahigh vacuum degree experiment system.

Description

Ion pump for preventing metal gas poisoning

Technical Field

The invention relates to a vacuum technology, in particular to a novel ion pump for preventing metal gas poisoning.

Background

Along with the development of scientific experiments towards more precise direction of atomic field, the application of ultra-high vacuum in industry and scientific research is more and more increasing, and the ultra-high vacuum is used as an experimental platform for precise measurement, and is often applied to scientific experimental systems requiring high vacuum, especially in the field of atomic molecular physics experiments, and atomic substances used by the experimental platforms are mostly alkali metals, such as: alkali metals such as rubidium, potassium and cesium, the required vacuum degree is generally 10 ^-7 Pa-10 ^-9 Pa。

The sputtering ion pump is mainly based on the principle of ionizing gas molecules under high pressure. The ion pump mainly consists of positive ionsThe pump body is composed of four parts, namely a pole, a cathode, a permanent magnet and a pump body, molecules or atoms of a pumped body are ionized under high voltage to form charged ions, the gas ions are promoted to move towards the cathode under the action of an electric field and are conveyed to the cathode adsorption surface of the pump, the cathode plate is made of metal titanium, and after the metal titanium is impacted and sputtered, an active titanium film is continuously formed on the inner wall of the cavity and continuously reacts with the gas molecules, so that the exhaust is continuously carried out. The sputtering ion pump has no moving mechanism, is a true oil-free, vibration-free and noise-free ultra-clean vacuum pump, and the obtained limit pressure can reach 10 ^-7 Pa-10 ^-9 Pa。

Generally, the anode of the ion pump is a honeycomb structure formed by arranging a plurality of stainless steel cylinders, the cathode is two parallel titanium alloy plates, the anode is clamped between the two titanium alloy plates, and the anode, the cathode and the titanium alloy plates are mutually kept at a certain distance and connected through high-voltage insulating ceramics.

Ion current is directly proportional to gas pressure in each honeycomb structure of the ion pump, gaps exist between a cathode array and an anode array of the ion pump, when the ion pump works, metal impurity particles in the system can penetrate through the honeycomb structures through the gaps and impact the inside of the ion pump, if ion pump protection measures are not applied in a vacuum system, high-voltage insulating ceramic of the ion pump can be polluted by alkali metal gas in the system, the alkali metal gas entering the ion pump is increased, the metal gas is deposited on the insulating ceramic, cathode and anode conduction of the ion pump can be caused, the air suction performance of the ion pump can be reduced, the ion current background of the ion pump is increased, and meanwhile, the service life of the ion pump can be shortened due to pollution of the ion pump.

Generally, in order to protect the ion pump, there are two measures, namely, heating the ion pump to reduce the deposition of metal gas in the ion pump; and secondly, a gas blocking device is arranged in the ion pump to reduce the metal gas entering the ion pump. If a protection measure for heating the ion pump is adopted, the temperature rise of the ion pump can desorb the metal gas adsorbed by the titanium cathode, so that the vacuum degree cannot be effectively reduced, meanwhile, the heating can cause the interpolar glow discharge and the pressure of the system to rise, and the normal work of the pump can be influenced in serious cases. Since the blocking devices typically installed in ion pumps block light between the ion pump and the system, they are also referred to as optical shields, which, although reducing the flow of gas ions between the system and the ion pump, can also reduce the pumping rate of the ion pump, affecting the vacuum effect. It is therefore necessary to carefully evaluate the shape and position design of the shut-off device in order to achieve the best evacuation effect.

Disclosure of Invention

Compared with the scheme, the device not only can greatly reduce the metal gas flow entering the pump body, but also has no obvious influence on the pumping speed of the pump, thereby prolonging the service life of the ion pump, reducing the ion flow background of the ion pump and achieving the isolation protection effect on the ion pump. The device structure is succinct, easily welds the installation, can not produce extra burden to scientific experiment platform.

The technical solution of the invention is as follows:

the ion pump for preventing metal gas poisoning is characterized in that a structure for preventing the ion pump from being polluted is additionally arranged in an output connecting pipeline of the sputtering ion pump, two or more groups of porous structure blocking pieces are fixedly arranged in the connecting pipeline through a vacuum flange, a metal base and a metal ring, the porous structure blocking pieces are formed by digging a plurality of arc ladder-shaped holes or other shape holes in the radius direction of a circular porous structure, and when the two or more groups of porous structures are fixed, the positions of small holes of the porous structures are kept not to be directly aligned, and the porous structure blocking pieces are arranged in a staggered mode, so that alkali metal gas or other working substances cannot directly enter the interior of the ion pump through the small holes.

The distance between the two groups of porous structure metal sheets is determined by the length of the metal circular ring.

The pore sizes of the two groups of porous structures are determined by the working substances of the vacuum system, for example, for alkali metals, the pore sizes are generally between 1 and 100 um.

When the ion pump for preventing metal gas poisoning is used, the output port of the connecting pipeline is connected with the multi-channel through the pipeline connecting flange.

The porous structure designed in the invention is assembled in a connecting channel of a novel ion pump and a vacuum system.

The main structure of the sputtering ion pump comprises a getter cathode plate, an anode cylinder, a shell, an electric lead-in, insulating ceramics, a strong permanent magnet, a connecting pipe and other accessories. The basic principle of the ion pump is to generate positive ions of gas molecules by using cathode discharge, and the ions collide with the cathode to be captured by the cathode and generate a sputtering effect. When the ion pump is used, high voltage is applied between the cathode and the anode, gas molecules are ionized under the action of the high voltage, and gas ions are promoted to move to the cathode under the action of an electromagnetic field to bombard the cathode plate of the ion pump. The cathode plate material is metal titanium, after the metal titanium is impacted and sputtered, an active titanium film is continuously formed on the inner wall of the cavity and continuously reacts with gas molecules, so that exhaust is continuously carried out, and active gas is pumped out. Due to the presence of the magnetic field, the cathode discharge can be maintained at a very low pressure.

The shape and the length of the anode cylinder are not protected, and the pump body of the ion pump for preventing metal gas poisoning is a universal ion pump.

The ion pump for preventing metal gas poisoning adopts porous structure hole sheet as the blocking device, and the blocking device is installed in the pipeline connecting the pump body and the vacuum system and fixed with the metal ring and the metal base. The porous structure has smooth inner and outer pipe walls, uniform pores, stable shape, high strength, high temperature resistance, high corrosion resistance, high impact resistance and other excellent performances, and meanwhile, the porous structure has good air permeability and can be well applied to vacuum pipelines.

In the invention, in order to fixedly arrange the porous structure dislocation piece, a fixed base is welded in a vacuum pipeline, after the first porous piece is arranged, a metal ring is used for separating a designed distance, the base of the second porous piece is welded, the small holes of the two porous structure dislocation pieces need to be dislocated, and then the two porous structure dislocation pieces are welded and fixed.

Compared with the prior art, the invention has the technical effects that:

(1) the ion pump of the invention, fix the porous structure hole plate in the ion pump and system communicating pipe in a dislocation way, because its surface area is large, can absorb the metal gas, and have small holes, compared with the prior pipe blocking device, it can not influence the pumping rate of the ion pump obviously, the limit pressure can reach 10 ^-9 Pa or less.

(2) Meanwhile, due to the blocking effect of the porous structure pore piece with the staggered small holes, compared with the porous structure pore piece without installation, after the porous structure pore piece is installed, the metal gas entering the ion pump is greatly reduced, the ion flow can reach the pA magnitude, and the pollution of the pumped metal gas to the ion pump is obviously reduced.

The ion pump disclosed by the invention is small in volume and long in service life, can improve the vacuum degree of an experimental system, has the characteristics of simple structure, easiness in welding and installation and stable performance, and meets the requirement of a space atomic physical experiment task requiring high vacuum degree.

Drawings

Figure 1 is a cross-sectional view of an inventive ion pump protected from metal gas poisoning,

wherein the

serial numbers

1 and 2 are porous metal pore sheets; number 3 is a fixed metal ring;

serial numbers

4, 5 and 6 are fixed metal bases; serial number 7 is an anode cylinder; the serial number 8 is a cathode plate; no. 9 is an insulating ceramic.

FIG. 2 is a cross-sectional view and a staggered arrangement of two sets of porous metal sheets

FIG. 3 is a structural diagram of the ion pump for preventing metal gas poisoning according to the embodiment of the present invention after the ion pump is installed

Detailed Description

The invention is further illustrated with reference to the following examples and figures, without thereby limiting the scope of protection of the invention.

Example (b): ion pump with two groups of porous structure staggered metal sheets and capable of preventing metal gas poisoning

The vacuum pipeline has an inner diameter of phi 15.2mm, the selected porous structure sheet is made of stainless steel and is formed by digging a plurality of arc ladder-shaped holes or holes with other shapes in the radius direction of a circular porous structure, and the pores of the porous structure are 30 um. The diameter of the two groups of porous structure metal sheets is phi 15mm, the thickness of the two groups of porous structure metal sheets is 1.0mm, the distance between the two groups of porous structure metal sheets is 4mm, and the opening dislocation angle is 60 degrees. The ion pump is the metal gas poisoning prevention ion pump.

See fig. 1. Fig. 1 is a cross-sectional view of an ion pump for preventing metal gas poisoning according to the present invention, in an embodiment, two sets of porous metal sheets are fixedly disposed, a fixed metal ring 3 and a fixed metal base 6 are welded in a vacuum pipe, after a first porous metal sheet 2 is disposed, a fixed metal base 5 is welded to firmly fix the porous metal sheets, and then a second porous metal sheet 1 is disposed, taking note that the pores of 1 and 2 need to be dislocated, and finally, a fixed base 4 is welded to firmly fix the porous metal sheets 1. In this embodiment, the distance between the two porous metal sheets is 4mm, and the offset angle of the openings is 60 °, see fig. 2.

The connecting pipeline port of the ion pump for preventing metal gas poisoning disclosed by the invention is connected with a multi-channel through a flange, referring to fig. 3, a rubidium source, a heating band, a thermometer and the ion pump are installed, referring to fig. 3, wherein the serial number 10 is the ion pump disclosed by the invention, the serial number 11 is the rubidium source, and the serial number 12 is the heating band. Baking and pre-pumping the system and the rough pumping pipeline, and gradually pumping the molecular pump to the limit 10 of the molecular pump after the pipeline is cooled ^-6 Pa. The temperature of the system and the ion pump is kept, the rubidium source is broken, the vacuum is deteriorated, the molecular pump continues to pump, and the pumping is carried out to 10 ^-6 Pa. And then starting an ion pump, gradually reducing the temperature of the system and the ion pump to room temperature, and then baking the rubidium source to enable rubidium steam to enter the vacuum pipeline. And monitoring the ion flow, the temperature of the rubidium source and the temperature of a system of the ion pump.

The readings of the ion pump were observed during system baking. And then, under the condition that other devices except the porous metal dislocation piece are not changed, replacing the porous metal dislocation piece with a porous metal long through hole piece and a ceramic long through hole piece with the same size, respectively carrying out system baking at the same temperature, and observing the readings of the ion pump in three groups of tests. In a long-time observation, the protection state is started most quickly when the ceramic long through hole plate is connected with an ion pump for testing, namely the ion pump starts to be poisoned at the moment, and after the ceramic long through hole plate is baked for a period of time, the porous metal long through hole plate starts to be protected and starts to be poisoned.

The results show that the novel ion pump with the porous metal dislocation hole sheet has the best result, and the ion pump with the porous metal dislocation hole sheet has certain barrier effect on metal conductive gas entering the ion pump due to the effect of the added porous metal dislocation sheet, so that the metal gas entering a pump body can be greatly reduced, the pumping speed of the ion pump is not obviously influenced, the ion flow background of the ion pump is reduced, the vacuum effect of an experimental system is favorably improved, and the service life of the ion pump is prolonged.

Claims

1. The ion pump capable of preventing metal gas poisoning is characterized in that a structure for preventing the ion pump from being polluted is additionally arranged in an output connecting pipeline of the sputtering ion pump, two or more groups of porous structure blocking pieces are fixedly arranged in the connecting pipeline through a vacuum flange, a metal base and a metal ring, the porous structure blocking pieces are formed by digging a plurality of arc ladder-shaped holes or other shape holes in the radius direction of a circular porous structure, and when the two or more groups of porous structures are fixed, the positions of small holes of the porous structures are not directly aligned, and the porous structures are arranged in a staggered mode, so that alkali metal gas or other working substances cannot directly enter the interior of the ion pump through the small holes.

2. The ion pump of claim 1, wherein the distance between said two sets of porous structure plates is determined by the length of said ring.

3. The ion pump of claim 1, wherein the pore size of the two porous structures is determined by the vacuum system working substance, such as for alkali metals, the pore size is generally between 1-100 um.

4. The ion pump for preventing metal gas poisoning as claimed in claim 1, wherein the porous structure designed in the invention is assembled in a connecting passage of the novel ion pump and a vacuum system.