阅读说明：本技术 一种热阴极组件、真空虚拟阴极自动测量装置及方法 (Hot cathode assembly, vacuum virtual cathode automatic measuring device and method ) 是由 李建泉 李书翰 张清和 邢赞扬 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种热阴极组件、真空虚拟阴极自动测量装置及方法,包括：电子收集极,所述电子收集极为中空的金属结构,所述金属结构上设有一开口,绝缘支架底端穿过所述开口并深入到电子收集极内部；所述绝缘支架底端连接热阴极灯丝；所述热阴极灯丝的两端分别与灯丝导线连接,所述灯丝导线穿过绝缘支架并引出到电子收集极外部；电子收集极的外部包围绝缘层,所述绝缘层和绝缘支架通过绝缘连接固件连接,能够使得电子收集极外部形成封闭的绝缘结构。本发明虚拟阴极由热阴极灯丝产生,而灯丝的加热电流由软件程序控制数据采集卡自动输出,因而该装置中的虚拟阴极是可控可变的。(The invention discloses a hot cathode assembly, a vacuum virtual cathode automatic measuring device and a method, comprising the following steps: the electron collector is a hollow metal structure, an opening is formed in the metal structure, and the bottom end of the insulating support penetrates through the opening and extends into the electron collector; the bottom end of the insulating support is connected with a hot cathode filament; two ends of the hot cathode filament are respectively connected with filament leads, and the filament leads penetrate through the insulating support and are led out of the electron collector; the outer part of the electron collector is surrounded by an insulating layer, and the insulating layer is connected with the insulating support through an insulating connecting fastener, so that a closed insulating structure can be formed outside the electron collector. The virtual cathode of the invention is generated by a hot cathode filament, and the heating current of the filament is automatically output by a data acquisition card controlled by a software program, so that the virtual cathode in the device is controllable and variable.)

1. A hot cathode assembly capable of producing a virtual cathode, comprising: the electron collector is a hollow metal structure, an opening is formed in the metal structure, and the bottom end of the insulating support penetrates through the opening and extends into the electron collector; the bottom end of the insulating support is connected with a hot cathode filament; two ends of the hot cathode filament are respectively connected with filament leads, and the filament leads penetrate through the insulating support and are led out of the electron collector;

the outer part of the electron collector is surrounded by an insulating layer, and the insulating layer is connected with the insulating support through an insulating connecting fastener, so that a closed insulating structure can be formed outside the electron collector.

2. A hot cathode assembly capable of creating a virtual cathode according to claim 1, wherein the metal casing of the electron collector is connected to an electron collector lead for applying a set bias voltage to the metal casing of the electron collector and collecting the electron current signal inside the electron collector.

3. A hot cathode assembly capable of producing a virtual cathode according to claim 1, wherein the electron collector is a hollow metal spherical shell structure.

4. A hot cathode assembly capable of producing a virtual cathode according to claim 1, wherein the hot cathode filament is a pure metal hot cathode electron emission material or a hot cathode electron emission material coated with lanthanum hexaboride powder or electron slurry on a metal filament.

5. A hot cathode assembly capable of producing a virtual cathode according to claim 1, wherein the insulating support is a single or double hole capillary glass or ceramic tube material.

6. An automatic measuring device for a vacuum virtual cathode, comprising: a main controller, a data acquisition device, the hot cathode assembly of any one of claims 1-5, a filament heating circuit, a filament scanning bias circuit, and an electron collector scanning bias circuit;

the main controller is connected with a data acquisition device, and the data acquisition device is respectively connected with the filament heating circuit, the filament scanning bias circuit and the electronic collector scanning bias circuit;

the hot cathode assembly is arranged in the vacuum cavity; the filament heating circuit and the filament scanning bias circuit are respectively connected with the filament lead, and the electronic collector scanning bias circuit is connected with the electronic collector through the electronic collector lead.

7. The vacuum virtual cathode automatic measuring device according to claim 6, wherein the data acquisition device is a data acquisition card, and the data acquisition card controls the outputs of the filament heating circuit, the filament scanning bias circuit and the electron collector scanning bias circuit through different analog output channels; the data acquisition card respectively receives an electronic current signal and a bias voltage signal of the electronic collector, a heating current signal and a scanning bias voltage signal of the hot cathode filament through different analog input channels.

8. The vacuum virtual cathode automatic measuring device according to claim 6, wherein the data acquisition device is connected with an isolated operational amplifier between the input end and the output end of the filament heating circuit.

9. A vacuum virtual cathode automatic measurement method is characterized by comprising the following steps:

the data acquisition device receives signals of the main controller and respectively controls output signals of the filament heating circuit, the filament scanning bias circuit and the electronic collector scanning bias circuit, so that set scanning bias and heating current are automatically applied to the hot cathode filament, and set bias voltage is automatically applied to the electronic collector;

the data acquisition device automatically collects current signals and bias voltage signals of the electron collector, heating current signals and scanning bias voltage signals of the hot cathode filament, and transmits the collected data to the main controller;

and the main controller calculates the depth and the space size of the potential well of the virtual cathode according to the received data.

10. The vacuum virtual cathode automatic measuring method according to claim 9, wherein the data collecting device automatically collects the current signal and the bias voltage signal of the electron collector, and the heating current signal and the scanning bias voltage signal of the hot cathode filament; the method specifically comprises the following steps:

under each filament scanning bias voltage and each filament heating current, the data acquisition device respectively acquires the scanning bias voltage and the heating current of the filament and the electronic current and the bias voltage of the electronic collector;

when the scanning bias voltage of the filament is equal to the lower limit voltage of the scanning bias voltage of the filament, the current signal output of the electron collector is saturated electron emission current; otherwise, the current signal of the electron collector is output as an electron collecting current.

Technical Field

The invention relates to the technical field of hot cathode electron emission, in particular to a hot cathode assembly, a vacuum virtual cathode automatic measuring device and a method.

Background

The emission probe is used as an effective means for measuring space potential, and plays an important role in plasma environment measurement and vacuum environment measurement. When the emission probe is used for measuring the space potential, on one hand, the filament needs to be heated by laser or direct current to enable the filament to emit thermal electrons, and meanwhile, scanning bias voltage needs to be applied to the filament of the emission probe, and finally, an I-V characteristic curve of the emission probe is obtained.

Under the ideal condition of not considering the initial velocity of the thermal electrons, the filament bias voltage corresponding to the starting position of the electron emission current in the I-V characteristic curve or the peak potential of a first derivative curve of the I-V characteristic curve is the space potential result to be measured. However, in practice, the thermionic electrons emitted by the filament of the emission probe must have some initial velocity, and their initial energy is not unique. The difference in the initial energies of the hot electrons causes the high energy electrons to move away from the filament and the low energy electrons to collect near the filament, eventually resulting in a negative potential well near the filament, the so-called "virtual cathode".

The existence of the virtual cathode inevitably causes the peak potential of a first derivative curve of an I-V characteristic curve of the emission probe or the bias voltage of a filament corresponding to the starting position of electron emission current in the I-V characteristic curve to deviate from the actual space potential, and finally causes the emission probe to give an incorrect measurement result. When the emission probe filament is in a weak emission state, the spatial potential measurement error caused by the virtual cathode may not be significant. However, as the electron emission intensity of the emission probe filament increases, the virtual cathode (depth of potential well and spatial size) formed in front of the filament increases, and the spatial potential measurement error caused by the virtual cathode cannot be ignored.

Although the physical mechanism of virtual cathode formation is not complex, it remains a serious challenge to experimentally accurately measure the virtual cathode. On one hand, because the space size of the virtual cathode is usually very small, the accurate measurement of the virtual cathode usually requires a high-precision measurement technology and a rigorous experimental design; on the other hand, accurate measurement of the virtual cathode also needs a reliable theoretical model to provide support, and none of the existing theoretical models related to the virtual cathode can provide an accurate virtual cathode expression.

In short, no device capable of measuring the virtual cathode is available at home and abroad, and no automatic measuring device capable of automatically completing the virtual cathode measurement, automatically analyzing data and rapidly giving a measuring result is available at present.

Disclosure of Invention

In view of this, the present invention provides a hot cathode assembly, a vacuum virtual cathode automatic measurement apparatus and a method thereof, which can automatically apply a scanning bias voltage and a heating current to a hot cathode filament, automatically apply a bias voltage to an electron collector, automatically collect a current signal of the electron collector, automatically analyze and process experimental data, and finally calculate parameters such as a depth of a potential well and a spatial dimension of a virtual cathode in a vacuum environment.

In order to achieve the above object, according to a first aspect of the present invention, the following technical solutions are adopted:

a hot cathode assembly capable of producing a virtual cathode, comprising: the electron collector is a hollow metal structure, an opening is formed in the metal structure, and the bottom end of the insulating support penetrates through the opening and extends into the electron collector; the bottom end of the insulating support is connected with a hot cathode filament; two ends of the hot cathode filament are respectively connected with filament leads, and the filament leads penetrate through the insulating support and are led out of the electron collector;

the outer part of the electron collector is surrounded by an insulating layer, and the insulating layer is connected with the insulating support through an insulating connecting fastener, so that a closed insulating structure can be formed outside the electron collector.

According to the second aspect of the invention, the following technical scheme is adopted:

an automatic measuring device for a vacuum virtual cathode, comprising: the device comprises a main controller, a data acquisition device, the hot cathode assembly, a filament heating circuit, a filament scanning bias circuit and an electron collector scanning bias circuit;

the main controller is connected with a data acquisition device, and the data acquisition device is respectively connected with the filament heating circuit, the filament scanning bias circuit and the electronic collector scanning bias circuit;

the hot cathode assembly is arranged in the vacuum cavity; the filament heating circuit and the filament scanning bias circuit are respectively connected with the filament lead, and the electronic collector scanning bias circuit is connected with the electronic collector through the electronic collector lead.

According to the third aspect of the invention, the following technical scheme is adopted:

a vacuum virtual cathode automatic measurement method, comprising:

the data acquisition device receives signals of the main controller and respectively controls output signals of the filament heating circuit, the filament scanning bias circuit and the electronic collector scanning bias circuit, so that set scanning bias and heating current are automatically applied to the hot cathode filament, and set bias voltage is automatically applied to the electronic collector;

the data acquisition device automatically collects current signals and bias voltage signals of the electron collector, heating current signals and scanning bias voltage signals of the hot cathode filament, and transmits the collected data to the main controller;

and the main controller calculates the depth and the space size of the potential well of the virtual cathode according to the received data.

The invention has the beneficial effects that:

the virtual cathode of the invention is generated by a hot cathode filament, and the heating current of the filament is automatically output by a data acquisition card under the control of a software program, so that the virtual cathode in the device is controllable and variable.

The design scheme can ensure that current signals on the electron collector are all from electron emission of the hot cathode filament on one hand, and can realize that electrons emitted by the hot cathode filament are all collected by the electron collector on the other hand, thereby providing accurate electron current data for calculation of the virtual cathode.

The invention can automatically apply scanning bias voltage and heating current to the hot cathode filament, automatically apply bias voltage to the electron collector, automatically collect current signals of the electron collector, and automatically analyze and process experimental data to finally provide characteristic parameters of the virtual cathode to be measured through setting measurement parameters in a software program.

The hot cathode filament in the invention is easy to manufacture and replace, thereby realizing the measurement of virtual cathodes formed by different hot cathode filament materials.

The device has a strict virtual cathode theoretical model as a support, and can ensure the reliability in the aspect of the measurement principle.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 is a schematic view of a hot cathode assembly;

FIG. 2 is a schematic diagram of the hardware configuration of an automatic virtual cathode measuring device;

FIG. 3 is a software flow diagram of an automated virtual cathode measurement apparatus;

FIG. 4 is a graph of experimental results obtained using an automated virtual cathode measurement device between filament temperature and filament heating current;

FIG. 5 is a graph showing experimental results of magnitude of virtual cathode potential and filament heating current obtained by an automatic virtual cathode measuring device;

FIG. 6 is a graph of experimental results obtained using an automated virtual cathode measurement device for virtual cathode spatial dimensions and filament heating current;

wherein, 1, filament lead; 2. an insulating support; 3. an insulated connection fastener; 4. an electron collector; 5. an insulating layer; 6. an electron collector wire; 7. a hot cathode filament; 8. a vacuum flange; 9. an electrode; 10. a vacuum chamber; 11. a hot cathode assembly; 12. a ground electrode; 13. a filament heating circuit; 14. an isolation operational amplifier; 15. a filament scanning bias circuit; 16. an electron collector scanning bias circuit; 17. an analog input channel a; 18. an analog input channel b; 19. an analog input channel c; 20. an analog input channel d; 21. an analog output channel a; 22. an analog output channel b; 23. an analog output channel c; 24. a data acquisition card; 25. and (4) a computer.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and specific embodiments.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

Example one

In one or more embodiments, a hot cathode assembly 11 capable of producing a virtual cathode is disclosed, with reference to fig. 1, comprising: the electron collector 4 is of a hollow metal structure, an opening is formed in the metal structure, and the bottom end of the insulating support 2 penetrates through the opening and extends into the electron collector 4; the bottom end of the insulating bracket 2 is connected with a hot cathode filament 7; two ends of the hot cathode filament 7 are respectively connected with the filament lead 1, and the filament lead 1 passes through the insulating support 2 and is led out of the electron collector 4;

the outer part of the electron collector 4 surrounds an insulating layer 5, and the insulating layer 5 and the insulating bracket 2 are connected through an insulating connecting fastener 3, so that a closed insulating structure can be formed outside the electron collector 4.

Specifically, the electron collector 4 is a hollow metal ball made of a conductive material such as copper, aluminum or stainless steel, and the top of the metal ball shell is provided with a slit, the size of the slit is slightly larger than that of the hot cathode filament 7, so that the hot cathode filament can be allowed to pass through and be placed in the center of the inside of the metal ball shell.

In this embodiment, the hot cathode filament 7 is disposed inside the electron collector 4, and the hot cathode filament 7 can emit thermal electrons and form a virtual cathode by direct current heating; the electron collector 4 surrounds the whole hot cathode filament 7 for collecting thermal electrons to obtain an accurate electron current signal.

The hot cathode filament 7 is fixed on the insulating support 2, and the insulating support 2 is made of single-hole or double-hole capillary glass tubes or ceramic tubes and the like; the filament lead 1 is connected to both ends of the hot cathode filament 7 through the insulating support 2 for applying a heating current and a scanning bias to the hot cathode filament 7.

In this embodiment, the hot cathode filament 7 is a pure metal hot cathode electron emission material such as a tungsten filament, a molybdenum filament, or a tantalum filament, or a common hot cathode electron emission material such as lanthanum hexaboride powder or electron slurry coated on a refractory metal filament such as a tungsten filament.

The metal spherical shell of the electronic collector 4 is connected with an electronic collector lead 6 and is used for applying bias voltage to the metal spherical shell and collecting an electronic current signal collected by the metal spherical shell; the electron collector 4 is surrounded by an insulating layer 5 made of common insulating materials such as oxide, nitride or high molecular polymer (plastic), the generation method can adopt a coating or spraying method, the insulating layer 5 is used for shielding electrons outside the metal spherical shell, and the current signals on the metal spherical shell are all from hot electrons emitted by the hot cathode filament 7.

The metal spherical shell, the insulating layer 5 and the insulating support 2 are fixedly connected together through an insulating connecting fixing piece 3, the insulating connecting fixing piece 3 is a thermoplastic plastic pipe such as polyethylene, and the insulating connecting fixing piece 3 is connected and fixed with the metal spherical shell and the insulating support 2 through heating, cooling or bonding and other modes.

Example two

In one or more embodiments, disclosed is a vacuum virtual cathode automatic measuring device, referring to fig. 2, including: a main controller, a data acquisition device, a hot cathode assembly 11, a filament heating circuit 13, a filament scanning bias circuit 15 and an electron collector scanning bias circuit 16 in the first embodiment;

the main controller is connected with a data acquisition device, and the data acquisition device is respectively connected with the filament heating circuit 13, the filament scanning bias circuit 15 and the electronic collector scanning bias circuit 16;

the hot cathode assembly 11 is disposed within the vacuum chamber 10; the filament heating circuit 13 and the filament scanning bias circuit 15 are respectively connected with the filament lead 1, and the electron collector scanning bias circuit 16 is connected with the electron collector 4 through the electron collector lead 6.

Specifically, the main controller is a computer 25, and the data acquisition device is a data acquisition card 24; the data acquisition card 24 is provided with at least three analog output channels and four analog input channels, the analog output channels of the data acquisition card 24 are respectively connected with the filament heating circuit 13, the filament scanning bias circuit 15 and the electronic collector scanning bias circuit 16, and simultaneously the respective circuits are controlled to respectively apply heating current of the hot cathode filament 7, scanning bias of the hot cathode filament 7 and bias voltage of the electronic collector 4; the analog input channel of the data acquisition card 24 respectively acquires a heating current signal of the hot cathode filament 7, a bias voltage signal of the electron collector 4 and an electron current signal acquired by the electron collector 4.

And an isolation operational amplifier 14 is respectively connected between the data acquisition device and the input end and the output end of the filament heating circuit 13. The isolation operational amplifier 14 is used to isolate the filament heating circuit 13 from the filament scanning bias circuit 15 and to prevent the filament heating circuit from interfering with the filament scanning bias circuit.

When the device is used for virtual cathode measurement, firstly, the hot cathode assembly 11 is required to be arranged in the vacuum cavity 10, and then the electrode 9 on the vacuum flange 8 is connected with the electronic collector lead 6 and the electronic collector scanning bias circuit 16; while the filament lead 1, the filament heating circuit 13, and the filament scanning bias circuit 15 are connected through electrodes on the other vacuum flange.

The heating current signal of the hot cathode filament 7 is automatically output by the filament heating circuit 13 under the control of the data acquisition card 24 through the analog output channel a 21; the scanning bias signal of the hot cathode filament 7 is automatically applied between the hot cathode filament 7 and the grounding electrode 12 of the vacuum chamber 10 by controlling the filament scanning bias circuit 15 through the analog output channel b22 by the data acquisition card 24; and the bias voltage signal of the electronic collector 4 is automatically applied between the electronic collector 4 and the grounding electrode 12 of the vacuum chamber 10 by controlling the electronic collector scanning bias circuit 16 through the analog output channel c23 by the data acquisition card 24.

The signal output of the analog output channels a, b and c on the data acquisition card 24 is automatically controlled and output by the computer 25. On the other hand, the data acquisition card 24 acquires the electron current signal of the electron collector 4, the bias voltage signal of the electron collector 4, the scanning bias signal of the hot cathode filament 7 and the heating current signal of the hot cathode filament 7 through the analog input channel a17, the analog input channel b18, the analog input channel c19 and the analog input channel d20, respectively.

The computer 25 automatically analyzes and processes the voltage and current signals collected by the data acquisition card 24, and finally calculates to obtain the depth and the space size of the potential well of the virtual cathode.

EXAMPLE III

In one or more embodiments, disclosed is a vacuum virtual cathode automatic measurement method, which specifically comprises the following processes:

(1) the data acquisition device receives signals of the main controller and respectively controls output signals of the filament heating circuit 13, the filament scanning bias circuit 15 and the electronic collector scanning bias circuit 16, so that set scanning bias voltage and heating current are automatically applied to the hot cathode filament 7, and set bias voltage is automatically applied to the electronic collector 4;

(2) the data acquisition device automatically collects a current signal and a bias voltage signal of the electronic collector 4, a heating current signal and a scanning bias voltage signal of the hot cathode filament 7, and transmits the collected data to the main controller;

(3) and the main controller calculates the depth and the space size of the potential well of the virtual cathode according to the received data.

In this embodiment, the main controller uses a computer 25, the software part of the automatic virtual cathode measurement device can be implemented by various ways such as LabVIEW, MATLAB, etc., and the flow diagram of the software operation is shown in fig. 3.

After starting the software, initial measurement parameters are firstly set, which mainly comprise the lower limit voltage, the upper limit voltage and the adjustment step length (V) of the filament scanning bias voltage_fL，V_fH，ΔV_f) Setting the lower limit current, the upper limit current and the adjusting step length (I) of the heating current of the filament_htL，I_htH，ΔI_ht)。

During the measurement, the program sets the bias voltage (V) of the electron collector 4 preferentially_s) Equal to the upper limit voltage (V) of the filament scanning bias_fH) Meanwhile, the data acquisition card 24 regulates the filament heating current from the lower current limit (I) by simulating the value of an output channel a21_htL) To the upper current limit (I)_htH) According to a set step length (delta I)_ht) And sequentially increased.

At each filament scanning bias (V)_f) And filament heating current (I)_ht) Next, the data acquisition card 24 acquires the scanning bias voltage (V) of the filament through four analog input channels respectively_f) Heating current (I) of the filament_ht) Electron current (I) of the electron collector_s) And a bias voltage (V)_s)。

When the filament is scanned by bias voltage (V)_f) Equal to the lower limit voltage (V) of the filament scanning bias_fL) When the hot cathode filament and the electron collector have the maximum potential difference, the thermal electrons emitted by the hot cathode filament can be collected by the electron collector, namely, the program automatically collects I at the moment_sElectron emission current (I) with output saturated_e)；

When V is_fIs not equal to V_fLWhen the electron current collected by the electron collector is partial hot electron capable of overcoming the virtual cathode, namely the program automatically converts the current I_sThe output is electron collecting current (I)_c) At the same time, the program will be the analog output channel b through the data acquisition card according to the set scanning bias step length (Δ V)_f) Automatically will V_fStepping to the next bias voltage (V)_f-ΔV_f) And finally, finishing all preset filament bias voltage scanning.

Wherein the saturated electron emission current (I)_e) And electron collecting current (I)_c) All are current signals formed by collecting thermoelectrons emitted by the filament by the electron collector, but the thermoelectron current signals flowing through the electron collector are different in magnitude due to different potentials of the electron collector, wherein I_eIs the maximum current signal, i.e. the saturated electron emission current.

At each saturated electron emission current (I)_e) Then, the program can calculate the filament temperature (T) through the preset parameters of the hot cathode filament (the filament area S, the electron work function phi of the filament and the actual electron emission coefficient A of the filament material)_e). Binding T_e、I_eAnd I_cThe program automatically calculates the potential of the virtual cathode to be measuredAnd a spatial dimension (x).

Wherein the filament temperature T_eCalculated by the formula of richardson-du shiman:

where k is the boltzmann constant. Potential of the virtual cathodeAnd the spatial dimension x are calculated by the following two equations, respectively:

wherein e is the elementary charge ε₀Is a vacuum dielectric constant, n₀For one-dimensional electron beam density, this parameter can be calculated from the following equation:

wherein j is_eRepresents the linear density of electron current in one dimension, m_eRepresenting the electron mass.

In addition, the device of the invention ensures that the hot cathode assembly operates in a vacuum environment with the air pressure not exceeding 40Pa in the use process, otherwise, the virtual cathode theoretical model adopted in the invention is not applicable, and the hot cathode filament is easy to damage. The filament temperature, virtual cathode potential and spatial dimension measurements obtained with the automated virtual cathode measurement apparatus are shown in fig. 4, 5 and 6, respectively.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.