CN107694478B

CN107694478B - Ultrasonic gas beam device

Info

Publication number: CN107694478B
Application number: CN201710871975.5A
Authority: CN
Inventors: 魏宝仁; 路迪; 邹亚明
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2017-09-25
Filing date: 2017-09-25
Publication date: 2020-08-28
Anticipated expiration: 2037-09-25
Also published as: CN107694478A

Abstract

The invention belongs to the technical field of physical and chemical experiments, and particularly relates to an ultrasonic gas beam device. The device includes: the device comprises a five-dimensional adjustable gas nozzle, a three-stage differential diaphragm group, a five-stage all-titanium vacuum chamber, a turbo molecular pump and a vacuum gauge pipe; the five-dimensional adjustable gas nozzle is positioned in a vacuum chamber, X, Y, Z three-dimensional position adjustment and X, Y direction angle adjustment of the nozzle are realized through a five-dimensional adjusting platform, and a dead zone of gas collision is matched with the position of a subsequent differential diaphragm in the gas injection process; the five-stage all-titanium vacuum chamber is a main body for realizing vacuum. The invention injects high-pressure gas into the vacuum chamber through the small hole to enable the gas to freely expand in vacuum, a static area is formed near the nozzle, a differential diaphragm is used for selecting a gas beam moving directionally from the static area, then two differential diaphragms are used for limiting the gas beam, the transverse speed (namely the temperature) of the gas beam is further reduced, and finally the stable ultrasonic gas beam is obtained in the vacuum chamber.

Description

Ultrasonic gas beam device

Technical Field

The invention belongs to the technical field of physical and chemical experiments, and particularly relates to an experimental device capable of generating an ultrasonic gas beam, which is used for obtaining a low-temperature ultrasonic gas beam with directionality.

Background

In the field of physical and chemical research, it is often necessary to obtain supersonic gas beams as the object of laboratory research. If the temperature of the ultrasonic gas beam is low, the improvement of the experimental precision is facilitated. Therefore, how to obtain a stable, continuous and directional supersonic gas beam has important significance for physical and chemical experiments. Furthermore, ultrasonic gas beams are also the main way to obtain gas cluster sources. The main method for obtaining supersonic gas beam is to blow high pressure gas into vacuum chamber through a very small nozzle, and to convert the disordered thermal motion energy of molecules into the kinetic energy of directional motion through the adiabatic expansion of the gas. Then one or a group of differential diaphragms is used for taking out one supersonic gas beam with good directionality. Based on the basic principle, the scheme of the invention is that high-pressure gas is adopted to pass through a small hole (such as the diameter of 10 microns) and jet gas into a vacuum chamber, so that the gas is freely expanded in the vacuum chamber, a dead zone is formed near a nozzle, a differential diaphragm is used for selecting a directional moving gas beam from the dead zone, then two differential diaphragms are used for limiting the gas beam, the transverse speed (namely the temperature) of the gas beam is further reduced, and finally, the stable ultrasonic gas beam is obtained in the vacuum chamber.

Disclosure of Invention

The invention aims to provide a set of experimental device (ultrasonic gas beam device for short) capable of generating ultrasonic gas beams, which provides stable and continuous low-temperature ultrasonic gas beams for physical and chemical researches in laboratories.

The structure of the ultrasonic gas beam device provided by the invention is shown in figure 1, and the ultrasonic gas beam device specifically comprises: the device comprises a five-dimensional adjustable gas nozzle, a three-stage differential diaphragm group, a five-stage all-titanium vacuum chamber, a turbo molecular pump and a vacuum gauge pipe; wherein:

the five-dimensional adjustable gas nozzle comprises: the top end of the stainless steel pipe is provided with a nozzle, and the gas nozzle can be filled with 0.2-20 bar of air pressure. The other end of the stainless steel pipe is fixed on a flange; the flange is arranged on the five-dimensional adjusting platform and is connected with the five-stage all-titanium vacuum chamber through a section of corrugated pipe, so that the stainless steel pipe and the nozzle are positioned in the vacuum chamber. The X, Y, Z three-dimensional position adjustment and X, Y-direction angle adjustment of the nozzle are realized by adjusting the flange through the five-dimensional adjusting platform, so that the dead zone of gas collision is matched with the position of a subsequent differential diaphragm in the gas injection process;

the three-stage differential diaphragm group consists of three coaxial differential diaphragms (Skimmer, a diverter similar to a bell mouth), the diaphragms are used for isolating stray gas through gas beams, and the three diaphragms are respectively fixed on a diaphragm tower through three flanges (the mounting surface of the three diaphragms can be sealed by indium wires). The diaphragm tower is integrally processed, three diaphragm holes are coaxial and three planes are parallel, and the three planes are respectively connected with a vacuum chamber of the five-stage all-titanium vacuum chamber in a sealing way (each mounting surface of the five-stage all-titanium vacuum chamber is sealed); the side surface of the diaphragm tower is hollowed, so that the stray gas blocked by the diaphragm is ensured to be pumped away from the side surface, and the influence on the secondary vacuum chamber is reduced as much as possible. The integrated design of the diaphragm tower can effectively reduce the installation error of the assembly part, and the coaxiality of the three-stage differential diaphragm and the parallelism of the three installation surfaces are well realized.

The five-stage all-titanium vacuum chamber is a main body for realizing vacuum, wherein a gas nozzle is introduced into the first-stage vacuum chamber, and the three-stage differential diaphragm is used for separating the 2 nd to 4 th-stage vacuum chambers respectively; the 4 th-stage vacuum chamber is an experimental chamber for obtaining ultrasonic gas beams; the 5 th-stage vacuum chamber is a collection stage, namely the ultrasonic gas beam is collected and pumped away at the 5 th stage after passing through the 4 th-stage experimental chamber, so that the influence on the background vacuum of the 4 th-stage vacuum chamber is avoided.

Each vacuum cavity of the five-stage full titanium vacuum cavity is provided with a vacuum gauge pipe respectively, and the vacuum gauge pipe is connected with a vacuum gauge and used for monitoring the vacuum degree of each stage of cavity in real time.

The turbomolecular pump is used for generating high vacuum condition for the whole device to work.

The vacuum pipeline of the system adopts metal titanium, and a CF standard knife edge flange is matched with an oxygen-free copper sealing ring at the joint to ensure that no air leakage exists when the system works; and (4) vacuumizing the vacuum pipeline by using a molecular pump and a mechanical pump.

The invention adopts high-pressure gas to pass through a small hole to inject gas into a vacuum chamber, so that the gas freely expands in vacuum, a quiet zone is formed near a nozzle, a differential diaphragm is used for selecting a beam of gas moving directionally from the quiet zone, then two differential diaphragms are used for limiting the beam of gas, the transverse speed (namely the temperature) of the beam of gas is further reduced, and finally the stable ultrasonic gas beam is obtained in the vacuum chamber.

Drawings

FIG. 1 is a schematic view of an ultrasonic gas beam apparatus.

FIG. 2 is a schematic view of a five-dimensional adjustable gas nozzle.

Fig. 3 is a schematic structural diagram of a diaphragm tower.

FIG. 4 is a schematic view of a five-stage vacuum chamber.

FIG. 5 is an overview of an ultrasonic gas beam system.

Reference numbers in the figures: the device comprises a nozzle 1, a pipeline 2 connected with a gas steel cylinder, a connecting flange 3 of a five-dimensional adjusting table, a position adjusting guide rail 4 in X and Y directions, a corrugated pipe 5 for adjusting the Z direction 5, a screw 6 for adjusting the Z direction, a flange 7 connected with a vacuum chamber 8, a first-stage differential diaphragm 9, a flange surface for installing the first-stage differential diaphragm 10, a second-stage differential diaphragm 11, a flange surface for installing the second-stage differential diaphragm 12, a third-stage differential diaphragm 13, a flange surface for installing the third-stage differential diaphragm 14, a first-stage vacuum chamber 15, a second-stage vacuum chamber 16, a third-stage vacuum chamber 17, a fourth-stage vacuum chamber 18, a fifth-stage vacuum chamber 19, a vacuum gauge 19 and a diaphragm tower 20.

Detailed Description

The ultrasonic gas beam device established by the invention specifically comprises: the device comprises a five-dimensional adjustable gas nozzle, a three-stage differential diaphragm group, a five-stage all-titanium vacuum chamber, a turbo molecular pump and a vacuum gauge pipe. The ultrasonic gas beam device is schematically shown in figure 1. Wherein:

a schematic diagram of a five-dimensional adjustable gas nozzle is shown in fig. 2. A 10 micron (alternatively 20 microns and 30 microns) nozzle 1 was mounted on a vacuum tube and flange crimped and indium sealed. The vacuum line is welded to a flange and is connected to the gas cylinder via line 2. The pressure reducing valve on the gas steel cylinder is changed, so that the pressure in the vacuum pipeline can be changed within the range of 0.2-20 bar, and the air pressure is the internal pressure of the nozzle before gas injection. The gas injection pipeline and the nozzle pipeline are welded on the flange 3 and then are installed on a five-dimensional adjusting mechanism, and the five-dimensional adjusting mechanism is used for ensuring that a dead zone where gas collides is matched with the position of a subsequent differential diaphragm in the gas injection process. The position adjusting mechanisms in the X direction and the Y direction are linked by guide rails 4, the translation of the relative positions can be realized, and the maximum distance of movement in each direction is 20 mm. The Z-direction adjustment is realized through a mode that the corrugated pipe 5 and the screw 6 are supported, namely the length of the corrugated pipe can be changed by adjusting the length of the screw 5, so that the Z-direction position of the nozzle can be adjusted, and the adjustment range is 0-30 mm. The minor adjustment of the swing angles of the nozzles in the X direction and the Y direction can be realized by changing the relative lengths of the screw pitches on the four screw rods 5. The five-dimensional adjusting structure and the nozzle are connected with the vacuum chamber through a flange 7. Through the adjusting mechanism, the on-line adjustment of the position of the gas nozzle relative to the differential diaphragm can be realized, so that the differential diaphragm is positioned in the center of a dead zone formed by gas injection of the nozzle, and a straight line formed by the three stages of differential diaphragms is positioned in the center of the nozzle.

The three-stage differential diaphragm group is used for acquiring a directional ultrasonic gas beam, and the structure diagram is shown in figure 3. When the differential diaphragm is installed, the small holes of the three differential diaphragms are required to be concentric, namely the centers of the small holes of the three differential diaphragms are on the same straight line, and the line is positioned at the center of the nozzle. The first stage differential diaphragm 8 has an aperture of 100 microns diameter and is mounted on the flange face 9. The diameter of the second stage differential diaphragm 10 is 300 microns and is arranged on the flange surface 11, and the diameter of the third stage differential diaphragm 12 is 1 mm and is arranged on the flange surface 13. Three difference diaphragms are installed on the diaphragm tower, and in order to ensure the installation accuracy, the diaphragm tower adopts integrated processing, and the concentricity of tertiary diaphragm mounting groove and the parallelism of three sealed face of assurance that can be fine. The installation process adopts a telescope matched with laser centering to ensure that the three-stage diaphragm hole is concentric and vertical to the plane of the diaphragm tower. The side surface of the diaphragm tower is provided with a hole for discharging stray gas blocked by the diaphragm, and the size of the side opening is required to be increased as much as possible in the processing process of the diaphragm tower so as to be beneficial to air extraction. The three-stage differential diaphragm group is used for ensuring that the ultrasonic gas beam experiment chamber obtains ultrahigh vacuum. Generally, the gas blocked by the first stage diaphragm is much, the vacuum degree is relatively poor, the second stage vacuum degree is better than the first stage vacuum degree, the gas blocked by the diaphragm is gradually reduced along with the increase of the stage number, and the vacuum degree is gradually improved.

The five-stage all-titanium vacuum chamber is used to obtain vacuum, see FIG. 4. Pure titanium is an ideal ultrahigh vacuum material, has the characteristics of no outgas and no remanence, and is very suitable for being used as a material of an ultrahigh vacuum chamber without remanence. The first stage vacuum chamber 14 is used to install gas injection nozzles, and since high pressure gas enters the vacuum chamber through the nozzles during gas injection, a strong pumping load is created in the first stage, which requires a high pumping speed molecular pump. The second stage vacuum chamber 15, the third stage vacuum chamber 16 and the fourth stage vacuum chamber 17 are respectively hermetically mounted with three planes of the diaphragm tower 20, i.e. the second stage vacuum chamber 15 is followed by the first stage diaphragm; the second stage diaphragm is followed by a third stage vacuum chamber 16; the third stage diaphragm is followed by a fourth stage vacuum chamber 17, also a chamber for obtaining a supersonic gas beam; the fifth stage vacuum chamber 18 is a collection stage where the ultrasonic gas beam is finally pumped away by a molecular pump, and in order to increase the pumping speed, the molecular pump is generally eccentrically installed so that the ultrasonic gas beam hits the molecular pump blades instead of the center of the molecular pump. Each stage of vacuum chamber is connected with a molecular pump for pumping air, and a mechanical pump is connected behind the molecular pump for obtaining primary vacuum. Meanwhile, each stage of vacuum chamber is provided with a vacuum gauge 19 and is connected with a vacuum gauge, and the vacuum degree of each stage of vacuum chamber is monitored in real time. Table 1 shows the hole diameters of the vacuum chambers, nozzles and diaphragms, the corresponding pumping speeds of the molecular pumps, the static background vacuum of the vacuum chambers and the vacuum of the vacuum chambers with 4 bar nitrogen injection. As can be seen from the comparison of the vacuum changes before and after gas injection in the table, the vacuum degree of the fifth stage during gas injection is significantly deteriorated, indicating that an ultrasonic gas beam is formed and collected by the collection stage, while the vacuum degree of the fourth stage before and after gas injection is unchanged, indicating that an ultrasonic gas beam is formed and smoothly passes through the fourth stage experimental chamber.

TABLE 1 ultrasonic gas beam test data sheet, first column for vacuum chambers of various stages, second column for nozzle and differential diaphragm diameter, third column for molecular pump pumping speed connected to vacuum chambers of various stages, fourth column for background vacuum degree of vacuum chamber, and fifth column for vacuum degree of various stages when injecting 4 bar nitrogen gas

。

Claims

1. An ultrasonic gas beam apparatus, comprising: the device comprises a five-dimensional adjustable gas nozzle, a three-stage differential diaphragm group, a five-stage all-titanium vacuum chamber, a turbo molecular pump and a vacuum gauge pipe; wherein:

the five-dimensional adjustable gas nozzle comprises: the top end of the stainless steel pipe is provided with a nozzle, and the other end of the stainless steel pipe is fixed on a flange; the flange is arranged on a five-dimensional adjusting platform and is connected with a five-stage all-titanium vacuum chamber through a section of corrugated pipe, so that the stainless steel pipe and the nozzle are positioned in the vacuum chamber; the adjustment of the five-dimensional adjusting platform on the flange realizes the X, Y, Z three-dimensional position adjustment and X, Y direction angle adjustment of the nozzle, and ensures that the dead zone of gas collision is matched with the position of a subsequent differential diaphragm in the gas injection process;

the three-stage differential diaphragm group consists of three coaxial differential diaphragms, and the three diaphragms are respectively fixed on a diaphragm tower in a sealing manner through three flanges; the diaphragm tower is integrally processed, three diaphragm holes are coaxial and three planes are parallel, and the three planes are respectively connected with a vacuum chamber of the five-stage all-titanium vacuum chamber in a sealing way;

the five-stage all-titanium vacuum chamber is a main body for realizing vacuum, wherein the first-stage vacuum chamber (14) is used for installing a gas injection nozzle, and high-pressure gas enters the vacuum chamber through the nozzle during gas injection, so that a strong pumping load can be formed at the first stage, and a high-pumping-speed molecular pump is required to be matched for the first stage; the second-stage vacuum chamber (15), the third-stage vacuum chamber (16) and the fourth-stage vacuum chamber (17) are respectively hermetically installed with three planes of the diaphragm tower (20), namely the second-stage vacuum chamber (15) is arranged behind the first-stage diaphragm; the second stage diaphragm is followed by a third stage vacuum chamber (16); the third stage diaphragm is followed by a fourth stage vacuum chamber (17), also a chamber for obtaining a supersonic gas beam; the fifth-stage vacuum chamber (18) is a collection stage, and the ultrasonic gas beam is finally pumped away by a molecular pump at the collection stage, so that the influence on the background vacuum of the 4-stage vacuum chamber is avoided; in order to improve the pumping speed, the molecular pump is eccentrically arranged, so that ultrasonic gas beams are beaten on the molecular pump blades instead of the center of the molecular pump; each stage of vacuum chamber is connected with a molecular pump for pumping air, and a mechanical pump is connected behind the molecular pump for obtaining primary vacuum;

each vacuum cavity of the five-stage all-titanium vacuum cavity is respectively provided with a vacuum gauge, and the vacuum gauge is connected with a vacuum gauge and used for monitoring the vacuum degree of each stage of the cavity in real time;

2. The ultrasonic gas beam device according to claim 1, wherein in the five-dimensional adjustment platform, the position adjustment mechanisms in the X and Y directions are linked by guide rails to realize relative position translation, and the maximum distance of movement in each direction is 20 mm; the Z-direction adjustment is realized in a mode of supporting the corrugated pipe and the screw rod, namely the length of the screw rod is adjusted to change the length of the corrugated pipe, the Z-direction position of the nozzle is adjusted, and the adjustment range is 0-30 mm; the relative lengths of the screw pitches on the four screw rods are changed, so that the micro adjustment of the swing angles of the nozzle in the X direction and the Y direction is realized; the position of the gas nozzle relative to the differential diaphragm is adjusted on line through the five-dimensional adjusting platform, so that the differential diaphragm is positioned in the center of a dead zone formed by gas injection of the nozzle, and a straight line formed by the three-stage differential diaphragm is positioned in the center of the nozzle.