阅读说明：本技术 一种储存式离子源 (Storage type ion source ) 是由 张虎忠 李得天 成永军 习振华 裴晓强 董猛 侯颖杰 魏建平 范栋 陈会颖 郭睿 于 2020-12-14 设计创作，主要内容包括：本申请涉及真空电子学技术领域,具体而言,涉及一种储存式离子源,包括阴极、电子聚焦系统、电离室以及电子收集极,其中：电子聚焦系统设置在阴极的上方,阴极产生的电子通过电子聚焦系统形成电子束流；电离室设置在电子聚焦系统与电子收集极之间,电离室的两侧设置有栅网,电离室与栅网之间形成均匀电场；电子束流通过均匀电场电离后,被电子收集极接收。本申请利用电子的空间电荷效应囚禁储存离子,使得离子的初始状态具有良好一致性,在引出离子源时,离子束的稳定性和均匀性得到很大提升。(The application relates to the technical field of vacuum electronics, in particular to a storage type ion source, which comprises a cathode, an electron focusing system, an ionization chamber and an electron collector, wherein: the electron focusing system is arranged above the cathode, and electrons generated by the cathode form an electron beam flow through the electron focusing system; the ionization chamber is arranged between the electron focusing system and the electron collector, grid meshes are arranged on two sides of the ionization chamber, and a uniform electric field is formed between the ionization chamber and the grid meshes; the electron beam is ionized by the uniform electric field and then received by the electron collector. This application utilizes the space charge effect imprison of electron to store the ion for the initial condition of ion has good uniformity, and when drawing forth the ion source, the stability and the homogeneity of ion beam obtain very big promotion.)

1. A storage ion source comprising a cathode, an electron focusing system, an ionization chamber, and an electron collector, wherein:

the electron focusing system is arranged above the cathode, and electrons generated by the cathode form an electron beam current through the electron focusing system;

the ionization chamber is arranged between the electron focusing system and the electron collector, grid meshes are arranged on two sides of the ionization chamber, and a uniform electric field is formed between the ionization chamber and the grid meshes;

and the electron beam current is ionized by the uniform electric field and then received by the electron collector.

2. The storage ion source of claim 1, wherein the cathode surface is provided with a gate mounted parallel to the cathode surface.

3. The storage ion source of claim 2, wherein said electron focusing system comprises a deceleration electrode disposed above said gate electrode and a focusing electrode disposed above said deceleration electrode, said focusing electrode being of a tapered configuration.

4. The storage ion source of claim 3, wherein the ionization chamber is disposed above the focusing electrode, the ionization chamber has a square frame structure, and the upper and lower ends of the ionization chamber are provided with through holes.

5. The storage ion source of claim 4, wherein the grid comprises a repulsion grid and an extraction grid.

6. The storage ion source of claim 5, wherein the repulsion grid is a single layer grid disposed on one side of the ionization chamber frame and the extraction grid is a double layer grid disposed on the other side of the ionization chamber frame.

7. The storage ion source of claim 4, wherein the electron collector is disposed above the ionization chamber, and wherein a potential of the electron collector is higher than a potential of the cathode.

8. The storage ion source of claim 1, wherein the cathode is a point cathode and an array of carbon nanotubes is used.

Technical Field

The application relates to the technical field of vacuum electronics, in particular to a storage type ion source.

Background

The ion source is widely applied to the fields of mass spectrometers, surface coating, ion thrusters and the like, and the improvement of the stability and uniformity of ion beam current becomes an important trend of technical development, for example, for a time-of-flight mass spectrometer, the ion energy and the spatial uniformity directly influence the performance parameters of the resolution capability, the sensitivity and the like of the instrument.

The ion source has many kinds, the traditional electron impact ion source is usually applied to the ionization of gas molecules, the electron energy usually reaches about 70eV, electrons oscillate in an ionization chamber under the action of an electric field, a magnetic field and the like, and finally generate ionization through the collision with the molecules, ions generated by ionization are uniformly distributed in the whole ionization space, and when an introduction voltage is applied or a repulsion voltage is increased, the ions are pulled out of the ionization chamber to form an ion beam current for a mass spectrometer, a surface coating film, an ion thruster and the like. The storage type ion source traps low-energy ions in the ionization chamber by utilizing a space charge effect, can ensure a good initial state of the ions, and solves the state difference of various ion sources in the process of instantaneous ionization and instantaneous extraction.

The traditional electron impact type ion source has poor controllability of a track introduced by focusing an electron beam, the initial position of initial ions generated by electron impact has high dispersibility, and when the ions are led out of an ionization chamber, the energy difference of the ions is large and large space and time difference exists. These problems limit the ion source technologyThe development of the technique also limits the application of the technique in the field of high-end measuring instruments or analytical instruments. As shown in FIG. 1, S.Sheridan et al propose a carbon nanotube cathode impact type ion source for Space mass spectrometer (see "S.Sheridan, M.W.Bardwell, A.D.Morse et al.A carbon n nanotubel electron impact source for low-power electron source, compact Space mass spectrometry. Advances in Space Research, 2012; 49: 1245), the emergent electron energy of which reaches hundreds of electron volts, and the area of the carbon nanotube cathode is 0.5mm²The ionization efficiency is relatively low, electrons randomly collide and ionize gas molecules after being led out, ions are directly led into the mass analyzer, and the uniformity and the stability of ion beam current are poor.

Disclosure of Invention

Aiming at the problems in the background technology, the invention provides a storage type ion source, which overcomes the problem of divergence of electron beams and ion beams, improves the focusing characteristic of the electron beams, can limit the generation area of electron impact ionization, and improves the stability and uniformity of ion beam current.

The storage type ion source provided by the application comprises a cathode, an electron focusing system, an ionization chamber and an electron collector, wherein: the electron focusing system is arranged above the cathode, and electrons generated by the cathode form an electron beam flow through the electron focusing system; the ionization chamber is arranged between the electron focusing system and the electron collector, grid meshes are arranged on two sides of the ionization chamber, and a uniform electric field is formed between the ionization chamber and the grid meshes; the electron beam is ionized by the uniform electric field and then received by the electron collector.

Further, the cathode surface is provided with a gate electrode, which is mounted in parallel on the cathode surface.

Furthermore, the electronic focusing system comprises a decelerating electrode and a focusing electrode, wherein the decelerating electrode is arranged above the gate pole, the focusing electrode is arranged above the decelerating electrode, and the focusing electrode is in a conical structure.

Furthermore, the ionization chamber is arranged above the focusing electrode, the ionization chamber is of a square frame structure, and the upper end and the lower end of the ionization chamber are provided with through holes.

Further, the grid mesh comprises a repulsion grid mesh and an extraction grid mesh.

Furthermore, the repulsion grid is a single-layer grid and is arranged on one side of the ionization chamber frame, and the extraction grid is a double-layer grid and is arranged on the other side of the ionization chamber frame.

Further, an electron collector is arranged above the ionization chamber, and the electric potential of the electron collector is higher than that of the cathode.

Furthermore, the cathode is a dot cathode, and a carbon nano tube array is adopted.

The storage type ion source provided by the invention has the following beneficial effects:

(1) the carbon nanotube cathode is used as an electron emission source, so that the carbon nanotube cathode has a smaller emission area, the angle dispersibility and the energy dispersibility of emitted electrons are smaller, the power consumption is lower, and the response time is superior to that of the traditional thermionic emission cathode.

(2) The carbon nanotube array cathode is prepared by adopting a vapor chemical deposition technology, so that the erect type and the uniformity of the carbon nanotube bundle are effectively ensured, better field emission performance is maintained, and larger emission current can be realized by matching with a gate pole, thereby being beneficial to the miniaturization of an ion source.

(3) The ion source is sequentially provided with the electron focusing system, the ionization chamber, the grid mesh and the electron collector, and ions are imprisoned and stored by utilizing the space charge effect of electrons, so that the initial state of the ions has good consistency, and the stability and uniformity of the ion beam are greatly improved when the ion source is led out.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, serve to provide a further understanding of the application and to enable other features, objects, and advantages of the application to be more apparent. The drawings and their description illustrate the embodiments of the invention and do not limit it. In the drawings:

FIG. 1 is a schematic diagram of a carbon nanotube cathode impact ion source applied to a spatial mass spectrometer in the prior art;

FIG. 2 is a schematic view of a storage ion source according to the present application;

FIG. 3 is a schematic diagram of an electron focusing system for a storage ion source according to the present application;

FIG. 4 is a schematic diagram of a trajectory of electrons emitted by a storage ion source according to the present application;

in the figure: the device comprises an a-glass substrate, a b-gate grid support, a c-CNT cathode, a d-gate grid, a 1-cathode, a 2-electronic focusing system, a 21-deceleration electrode, a 22-focusing electrode, a 3-ionization chamber, a 4-electronic collector, a 5-gate, a 6-repulsion grid, a 7-extraction grid and an 8-electronic motion track.

Detailed Description

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

As shown in fig. 2 to 4, the storage type ion source provided by the present application includes a cathode 1, an electron focusing system 2, an ionization chamber 3, and an electron collector 4, wherein: the electron focusing system 2 is arranged above the cathode 1, and electrons generated by the cathode 1 form an electron beam current through the electron focusing system 2; the ionization chamber 3 is arranged between the electron focusing system 2 and the electron collector 4, grid meshes are arranged on two sides of the ionization chamber 3, and a uniform electric field is formed between the ionization chamber 3 and the grid meshes; the electron beam is ionized by the uniform electric field and received by the electron collector 4.

Specifically, the embodiment of the present invention provides a storage type ion source, which mainly uses the space charge effect of electrons to trap and store low-energy ions in the ionization chamber 3, so that the initial state of the ions has good consistency, and the stability and uniformity of the ion beam can be greatly improved when the ion source is extracted. The cathode 1 is an electron source of a monolithic structure, and is mainly used for emitting electrons. The electron focusing system 2 is mainly used for focusing the electrons emitted from the cathode 1, so that a large number of electrons form a parallel electron beam. The ionization chamber 3 is mainly used for ionization of electrons, a semi-closed ionization region is formed by the ionization chamber and the grid meshes on two sides, a uniform electric field is formed, the electron beams can be ionized when passing through the uniform electric field, and ions generated by ionization can be introduced into the ionization chamber 3 to be stored, so that an ion source or the ion beams are formed. The electron collector 4 is used for collecting the electron beam ionized by the ionization chamber 3. The electron focusing system 2 and the ionization chamber 3 are insulated by ceramic and clamped and fixed by means of threaded connection. In the embodiment of the invention, the relative nominal distance between all the electrodes needs to be accurately measured by auxiliary equipment, and then all the electrodes are connected with the flange by welding leads.

Further, the surface of the cathode 1 is provided with a gate 5, and the gate 5 is arranged on the surface of the cathode 1 in parallel. The gate 5 is mainly used for providing an electric field for leading out electrons, leading out the electrons emitted by the cathode 1 into the electron focusing system 2, the gate 5 is preferably a grid structure made of electron-resistant and ion-bombardment-resistant materials such as stainless steel, molybdenum, tungsten and the like, the grid structure is processed by processes such as chemical etching, electroplating, weaving and the like, the transmittance is between 50 and 80 percent, the leading-out voltage of the gate 5 is preferably set between 400 and 1000V, and the specific voltage is determined according to the emission performance of the cathode 1. The relative position of the gate 5 is parallel to the surface of the cathode 1, the gate 5 and the cathode 1 are fixed by adopting a mica sheet bonding mode, and the mica sheets can be respectively bonded and fixed with the substrate of the cathode 1 and the outer edge of the gate 5 grid mesh by adopting silver glue or other adhesives.

Further, the electron focusing system 2 includes a deceleration electrode 21 and a focusing electrode 22, the deceleration electrode 21 is disposed above the gate 5, the focusing electrode 22 is disposed above the deceleration electrode 21, and the focusing electrode 22 has a tapered structure. The electron focusing system 2 is an electron optical system, the decelerating electrode 21 is preferably a stainless steel, molybdenum or tungsten mesh, the focusing electrode 22 is set to be a conical structure, the lower end is narrow, the upper end is wide, different structures and materials of the focusing electrode 22 can be selected according to different types of cathodes 1, the decelerating electrode 21 and the focusing electrode 22 jointly form the electron focusing system 2, and the electron focusing system is used for focusing electrons led out from the gate 5 to enable the electrons to be focused to form collimated and parallel electron beams.

Further, the ionization chamber 3 is arranged above the focusing electrode 22, the ionization chamber 3 is in a square frame structure, and the upper end and the lower end of the ionization chamber are provided with through holes. The ionization chamber 3 is mainly used for ionization of electrons, and stores ions generated by ionization. Ionization chamber 3 is preferably the frame construction that metal material such as stainless steel made, the through-hole that both ends set up about the frame mainly used the business turn over of electron, the electron beam gets into ionization chamber 3 through the through-hole of lower extreme, the electron can collide the ionization with gas molecule at the in-process through ionization chamber 3, the ion that the ionization produced can be introduced through the electric field that ionization chamber 3 both sides grid formed and stored in ionization chamber 3, form ion beam and ion source, make the initial condition of ion have good uniformity, when subsequent ion source of drawing forth, the stability and the homogeneity of ion beam can obtain very big promotion, and the electron jets out through the through-hole of upper end after the ionization, get into subsequent electron collector 4 and be collected and handled.

Further, the grid includes a repulsion grid 6 and an extraction grid 7. The repulsion grid 6 and the extraction grid 7 are arranged and mainly used for guaranteeing the uniformity of an electric field in an ionization region, the grids are preferably prepared in a chemical etching or physical weaving mode and the like, and have certain physical transmittance, so that gas molecules can be guaranteed to enter the ionization chamber 3, and ions generated by electron ionization are also guaranteed to be introduced into the ionization chamber 3 for storage at high efficiency.

Further, the repulsion grid 6 is a single-layer grid and is arranged on one side of the framework of the ionization chamber 3, and the extraction grid 7 is a double-layer grid and is arranged on the other side of the framework of the ionization chamber 3. The repulsion grid 6 is fixed on the left side of the ionization chamber 3 in a welding mode, the leading-out grid 7 is fixed on the right side of the ionization chamber 3 in a welding mode, uniform electric fields are formed among the ionization chamber 3, the repulsion grid 6 and the leading-out grid 7 and jointly form a semi-closed ionization region, an electron beam can drift through the ionization region to be ionized, ions generated by ionization can be led into the ionization chamber 3 to be stored, and the ionized electron beam leaves the ionization region and is finally received by the electron collector 4.

Further, an electron collector 4 is disposed above the ionization chamber 3, and the potential of the electron collector 4 is higher than that of the cathode 1. The electron collector 4 is mainly used to receive the electron beam passing through the ionization chamber 3, and is preferably a metal electrode having a potential slightly higher than that of the cathode 1.

Furthermore, the cathode 1 is a dot cathode 1, and a carbon nanotube array is adopted. The cathode 1 preferably adopts a carbon nanotube array prepared by direct growth by a thermal vapor chemical deposition method, has an emission area of about 1mm, is set as a point electron source, and is mainly used for providing electrons.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art without departing from the spirit and principle of the present application, and any modifications, equivalents, improvements, etc. made therein are intended to be included within the scope of the present application.