阅读说明：本技术 一种能够模拟电离层等离子体环境的试验装置 (Test device capable of simulating ionized layer plasma environment ) 是由 杜清府 王传安 郭怀龙 王进 张清和 李延辉 郭新 邢赞扬 孙琪 于 2020-06-15 设计创作，主要内容包括：本发明涉及一种能够模拟电离层等离子体环境的试验装置,包括仓筒,仓筒内部固定有加速栅网,加速栅网上方设置有等离子体源,加速栅网与第一电源的正极连接,第一电源的负极与第二电源的正极连接,第二电源的正、负极分别与等离子体源连接,仓筒还连接有抽真空机构,本发明的试验装置能够产生所需电子密度的等离子体环境,为下一步实验奠定基础。(The invention relates to a test device capable of simulating an ionized layer plasma environment, which comprises a bin, wherein an accelerating grid is fixed in the bin, a plasma source is arranged above the accelerating grid, the accelerating grid is connected with the anode of a first power supply, the cathode of the first power supply is connected with the anode of a second power supply, the anode and the cathode of the second power supply are respectively connected with the plasma source, and the bin is also connected with a vacuumizing mechanism.)

1. The utility model provides a can simulate test device of ionosphere plasma environment which characterized in that, includes the silo, and silo inside is fixed with the grid with higher speed, and grid with higher speed top is provided with the plasma source, and the grid with higher speed is connected with the positive pole of first power, and the negative pole of first power is connected with the positive pole of second power, and the positive pole of second power, negative pole are connected with the plasma source respectively, and the silo still is connected with evacuation mechanism.

2. The experimental device for simulating the ionized layer plasma environment as claimed in claim 1, wherein the chamber is connected with a water cooling mechanism, and the water cooling mechanism is used for cooling the chamber.

3. A test rig capable of simulating an ionospheric plasma environment according to claim 1, wherein the first power supply is a regulated power supply for providing a regulated voltage between the plasma source and the acceleration grid, and the second power supply is a programmable current source for exciting electrons to the plasma source.

4. A test rig capable of simulating an ionospheric plasma environment according to claim 1, wherein the plasma source comprises a stationary disk on which wires are provided, the wires being capable of functioning as a metal cathode, the stationary disk being bridged over an acceleration grid.

5. The test device according to claim 1, wherein the two ends of the plasma source are respectively connected to a first electrode column and a second electrode column, the first electrode column and the second electrode column are respectively connected to the positive electrode and the negative electrode of a second power source, the accelerating grid is connected to a third electrode column and a fourth electrode column, the third electrode column is connected to the positive electrode of the first power source, and the negative electrode of the first power source is connected to the first electrode column.

6. The test device for simulating the plasma environment in the ionized layer of claim 1, wherein the first electrode column, the second electrode column and the third electrode column are all connected with a water cooling mechanism.

7. A test device capable of simulating an ionospheric plasma environment according to claim 1, wherein the vacuum pumping mechanism comprises a mechanical pump and a molecular pump, an inlet of the molecular pump is connected to the chamber body, an outlet of the molecular pump is connected to an inlet of the mechanical pump, and another inlet of the mechanical pump is connected to the chamber body.

8. The testing apparatus capable of simulating an ionospheric plasma environment of claim 1, wherein said chamber is connected to an inlet tube and an outlet tube, said inlet tube and outlet tube being in communication with an interior space of the chamber.

9. The experimental device for simulating the plasma environment in the ionized layer according to claim 1, wherein the plasma detector is disposed in the chamber, and the plasma detector is connected to a telescopic mechanism disposed outside the chamber, and the telescopic mechanism can drive the plasma detector to move along a direction perpendicular to the axis of the chamber.

10. A test rig capable of simulating an ionospheric plasma environment as in claim 1, wherein said cartridge is further fitted with an ionization gauge and a resistance gauge.

Technical Field

The invention relates to the technical field of experimental equipment, in particular to a test device capable of simulating an ionized layer plasma environment.

Background

The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.

The ionosphere is an important ring in the daily energy transmission chain, is an important component of space weather, and is the geospatial region closest to the space physical application level. The state and change of the ionosphere have important influence on communication satellite, navigation, rocket operation, remote sensing positioning, beyond-the-horizon radar detection and the like. The inventor finds that the space environment is complex, when the satellite-borne detector is lifted off, the detector does not work or the working state is not ideal, which is fatal to the project, therefore, a large number of experiments need to be carried out in the experimental environment before the satellite, the rocket and the satellite-borne detector are lifted off formally, and how to simulate the plasma environment of the ionized layer is particularly important. The satellite-loaded plasma detector operating in the ionized layer can directly detect the electron density, the measurement result is most direct and real, and how to verify the accuracy of the load detector needs a vacuum chamber capable of simulating the ionized layer plasma environment, so that a test device capable of simulating the ionized layer plasma environment is urgently needed to be designed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a test device capable of simulating an ionized layer plasma environment, which can generate a plasma environment, can realize the adjustment of electron density, generates a plasma environment similar to the space electron density of an ionized layer, and is convenient for subsequent experiments.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, an embodiment of the present invention provides a test apparatus capable of simulating an ionosphere plasma environment, including a bin, wherein an acceleration grid is fixed inside the bin, a plasma source is disposed above the acceleration grid, the acceleration grid is connected to an anode of a first power supply, a cathode of the first power supply is connected to an anode of a second power supply, an anode and a cathode of the second power supply are respectively connected to the plasma source, the bin is further connected to a vacuum pumping mechanism, and the vacuum pumping mechanism is capable of vacuumizing an inner space of the bin.

With reference to the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, where the bin is connected to a water cooling mechanism, and the water cooling mechanism is configured to cool the bin.

In combination with the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, where the first power supply is a regulated power supply for providing a stable voltage between the plasma source and the acceleration grid, and the second power supply is a programmable current source for exciting electrons to the plasma source.

In combination with the first aspect, embodiments of the present invention provide a possible implementation manner of the first aspect, wherein the plasma source comprises a fixed disk on which a metal wire is arranged, the metal wire being capable of being used as a metal cathode, and the fixed disk is erected on an acceleration grid.

In combination with the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, two ends of the plasma source are respectively connected to a first electrode column and a second electrode column that are fixedly disposed, the first electrode column and the second electrode column are respectively connected to an anode and a cathode of a second power supply, the acceleration grid is connected to a third electrode column and a fourth electrode column, the third electrode column is connected to an anode of the first power supply, and a cathode of the first power supply is connected to the first electrode column.

With reference to the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, and the first electrode column, the second electrode column, and the third electrode column are all connected to a water cooling mechanism.

In combination with the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, wherein the vacuum pumping mechanism includes a mechanical pump and a molecular pump, an inlet of the molecular pump is connected to the cartridge body, an outlet of the molecular pump is connected to an inlet of the mechanical pump, and another inlet of the mechanical pump is connected to the cartridge body.

With reference to the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, wherein the cartridge is connected to an air inlet pipe and an air outlet pipe, and the air inlet pipe and the air outlet pipe are communicated with an inner space of the cartridge.

In combination with the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, a plasma detector is disposed in the bin, the plasma detector is connected to a telescopic mechanism disposed outside the bin, and the telescopic mechanism can drive the plasma detector to move along a direction perpendicular to an axis of the bin.

In combination with the first aspect, an embodiment of the present invention provides a possible implementation manner of the first aspect, and the cartridge is further provided with an ionization gauge and a resistance gauge.

The invention has the beneficial effects that:

the experimental device is provided with the plasma source and the accelerating grid which are connected with the first power supply and the second power supply, electrons of the plasma source can be excited by the second power supply and collide with neutral particles in the bin body under the action of an accelerating electric field generated by the first power supply to generate plasma, and the plasma with required electron density is generated through adjustment of the first power supply and the second power supply, so that the required plasma environment is created for the next experiment, and the foundation is laid for the next experiment.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 is a schematic view of the overall structure of embodiment 1 of the present invention;

fig. 2 is a schematic diagram of a second power output constant power control principle of embodiment 1 of the present invention;

FIG. 3 is a schematic diagram of the connection of a plasma source and an accelerating grid with a first power supply and a second power supply in accordance with embodiment 1 of the present invention;

FIG. 4 is a schematic diagram of collision between electrons and target particles according to example 1 of the present invention;

FIG. 5 is a structural diagram of electron density influencing factors in example 1 of the present invention;

FIG. 6 is a schematic diagram of a source stability test curve in example 1 of the present invention;

FIG. 7 is a longitudinal distribution diagram of electron density in the bin under the condition of a tungsten filament power of 303W in accordance with embodiment 1 of the present invention;

FIG. 8 shows an acceleration field of 1.25X 10 in example 1 of the present invention³The electron density of the bin body is transversely distributed under the condition of V/m;

FIG. 9 is a transverse distribution diagram of electron density in the bin under the condition of 303W tungsten filament power in accordance with embodiment 1 of the present invention;

the plasma power generation device comprises an acceleration grid 1, a plasma source 2, a cabin body 3, a cabin cover 4, a first cooling water inlet pipe 5, a first cooling water outlet pipe 6, a first electrode column 7, a second electrode column 8, a third electrode column 9, a cabin inner wiring part 9-1, a cabin outer wiring part 9-2, a cabin outer wiring part 9-3, a cabin outer wiring terminal 10, a fourth electrode column 11, a second power supply 12, a first power supply 13, a second cooling water inlet pipe 14, a second cooling water outlet pipe 15, a mechanical pump 16, a molecular pump 17, a plasma detector 18, a connecting rod 19, an air inlet pipe 20, an air outlet pipe 21, an ionization gauge 22, a resistance gauge 23 and an observation window.

Detailed Description

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.

For convenience of description, the words "up", "down", "left" and "right" in the present invention, if any, merely indicate correspondence with up, down, left and right directions of the drawings themselves, and do not limit the structure, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the invention.

As described in the background art, there is a need to provide a testing apparatus for simulating an ionospheric plasma environment, which facilitates the performance of subsequent related experiments.

In embodiment 1 of an exemplary embodiment of the present application, a test apparatus capable of simulating an ionospheric plasma environment, as shown in fig. 1, includes a bin, an acceleration grid 1 is fixed inside the bin, a plasma source 2 is disposed above the acceleration grid, the acceleration grid is connected to a positive electrode of a first power source, a negative electrode of the first power source is connected to a positive electrode of a second power source, the positive and negative electrodes of the second power source are respectively connected to the plasma source, the first power source enables a positive bias voltage to be provided between the acceleration grid and the plasma source, an acceleration electric field is formed, electrons of the plasma source can be excited by the second power source, neutral ions in the bin are touched under the effect of the acceleration electric field, plasma is generated in the bin, and a vacuumizing mechanism is further connected to the bin, and the vacuumizing mechanism can vacuumize an inner space of the bin.

The bin adopts cylinder type structure or cube structure, and is preferred, in this embodiment, the bin adopts cylinder type structure, the bin includes the open storehouse body 3 that sets up in top, the open be connected with cang gai 4 of dismantling in storehouse body top.

The plasma source comprises a fixed disc, a metal wire is arranged on the fixed disc and can be used as a metal cathode, two ends of the metal wire are respectively connected with a positive electrode and a negative electrode of a second power supply, electrons are excited by the second power supply, the fixed disc is erected on an accelerating grid, so that the metal wire and the accelerating grid have a set distance, the set distance can be set according to actual needs, and is preferred and 8 mm.

The materials used as metal cathodes should meet the following requirements: (1) the overflow work is low, the melting point is high, the evaporation rate is low, and the emission is stable; (2) the alloy has good mechanical properties, particularly high-temperature properties, and can prevent the metal from sagging, deforming, embrittling and cracking in the working process; (3) it should have good chemical stability and not react with oxygen, water vapor, carbon dioxide, etc. The metals meeting the above requirements are tungsten, molybdenum, tantalum, niobium, rhenium.

Preferably, the metal wire is a tungsten wire, which has good metal properties in all respects and is the most used pure metal cathode in production. Since pure metal tungsten recrystallizes at high temperatures, the fibrous crystals break and form granular crystals which have a very small crystal energy and cause sagging and brittle fracture of the tungsten wire. In order to overcome the defect, in the embodiment, the tungsten wire containing the addition agent such as silicon oxide, aluminum oxide, potassium oxide and the like is selected, and under the action of the addition agent, coarse particles which are mutually intercrossed are formed when the tungsten wire is recrystallized, so that the heated brittleness of the tungsten wire is greatly improved.

The temperature of the tungsten filament is related to the radiation electrons, and in order to obtain uniform and stable radiation electrons to generate stable plasma, the temperature of the tungsten filament must be controlled to a stable value, and the temperature of the tungsten filament is determined by the power of the tungsten filament. The tungsten resistance wire has a temperature coefficient, the resistivity increases along with the temperature increase, and when the temperature is more than 1240K, the resistivity and the temperature change are related as follows:

ρ＝-194.101+0.467T+(4.06×10^-5)T²(1)

where ρ is the resistivity of the tungsten filament and T is the temperature of the tungsten filament

The tungsten filament resistance is:

wherein R is the resistance of the tungsten filament, rho is the resistivity of the tungsten filament, l is the length of the tungsten filament, and s is the cross-sectional area of the tungsten filament.

When a certain constant current source current is passed through the tungsten filament, P is I²R(3)

P is the power of the tungsten filament, I is the current in the tungsten filament, and R is the resistance of the tungsten filament.

The power consumed by the tungsten wire resistor is firstly to generate heat to raise the temperature of the tungsten wire resistor and secondly to radiate electrons and energy to the periphery, when the generated heat is a main part, the resistance value of the tungsten wire is increased, the power of the tungsten wire is increased, and therefore the temperature of the tungsten wire is increased, and a positive feedback system which cannot obtain stable temperature is formed. The quantity of electrons radiated by the tungsten filament is related to the temperature of the tungsten filament, so that to obtain a stable radiation source, the temperature of the tungsten filament must be controlled to be stable, namely the resistance of the tungsten filament is constant, the power applied to the resistance of the tungsten filament is mainly used for generating radiation electrons and radiation energy, and if the constant current source supplies power, the resistance is ensured to be constant (the temperature is constant), namely the power is constant. Therefore, in the embodiment, the second power supply adopts a programmable current source, and the current of the programmable current source is adjusted by programming, so that the purpose of constant power of the tungsten filament is achieved. The adjustment process is shown in fig. 2.

Because the electron excitation quantity of the plasma source is greatly influenced by the temperature, the tungsten filament is heated to generate a large amount of heat to influence the concentration of electrons emitted by the tungsten filament, and further the concentration of the plasma is required to generate a stable plasma source, the temperature of the peripheral environment of the plasma source needs to be controlled to be stable, and therefore the bin body of the bin is connected with a water cooling mechanism for cooling the peripheral environment of the plasma source.

The water cooling mechanism comprises a cooling water flow channel, a first cooling water inlet pipe 5 and a first cooling water outlet pipe 6, wherein the cooling water flow channel which is distributed in a surrounding mode is arranged in the bin wall of the bin body, the first cooling water inlet pipe and the first cooling water outlet pipe are arranged on the bin wall of the bin body, the first cooling water inlet pipe and the first cooling water outlet pipe are respectively communicated with two ends of the cooling water flow channel, the first cooling water inlet pipe is connected with the water cooling cabinet, the water cooling cabinet can introduce cooling water into the cooling water flow channel through the first cooling water inlet pipe, and the cooling water after heat exchange flows out through the first cooling water outlet pipe.

In this embodiment, the first power supply is a regulated power supply capable of outputting 0 to 64V, and a stable accelerating electric field can be formed between the accelerating grid and the plasma source.

Preferably, the accelerating grid mesh is a molybdenum mesh.

In this embodiment, the specific connection mode between the plasma source and the accelerating grid and the first power supply and the second power supply is as follows:

the bin cover is provided with four electrode columns, the electrode columns penetrate through the bin cover, an insulating material is arranged between the electrode columns and the bin cover, the four electrode columns are respectively a first electrode column 7, a second electrode column 8, a third electrode column 9 and a fourth electrode column 10, the electrode columns are copper columns and comprise a bin inner wiring part 9-1 and a bin outer wiring part 9-2, the bin inner wiring part is in conductive connection with the bin outer wiring part, the bin outer wiring part is provided with a bin outer wiring terminal 9-3, the bin outer wiring terminal is in conductive connection with the bin outer wiring part, and the bin inner wiring part serves as a bin inner wiring terminal.

As shown in fig. 3, two ends of the tungsten filament are respectively connected with the in-bin connecting portions of the first electrode column 7 and the second electrode column 8 in an electrically conductive manner, and the out-bin connecting portions of the first electrode column and the second electrode column are connected with the positive electrode and the negative electrode of the second power supply 11 through the out-bin connecting terminal and the lead.

The accelerating grid is connected with the in-bin connecting parts of the third electrode column and the fourth electrode column, and the in-bin connecting parts of the third electrode column and the fourth electrode column are fixed in the bin body.

And the outside bin wiring terminal of the third electrode column 9 is connected with the positive electrode of the first power supply 12, and the negative electrode of the first power supply is connected with the outside bin wiring part of the first electrode column through a wire.

The first electrode column, the second electrode column, the third electrode column and the fourth electrode column are all connected with a water cooling mechanism and used for cooling the four electrode columns, cooling water flow channels are arranged in the electrode columns, a second cooling water inlet pipe 13 and a second cooling water outlet pipe 14 which are communicated with the cooling water flow channels are arranged on the electrode columns, cooling pipes enter the cooling water flow channels of one electrode column through the second cooling water inlet pipe and penetrate out through the second cooling water outlet pipe and enter the cooling water flow channels of the other electrode column through the second cooling water inlet pipe of the other electrode column, the cooling pipes are sequentially wound and distributed inside the cooling water flow channels of the four electrode columns, and the end parts of the cooling pipes are connected with a water cooling cabinet.

The vacuum-pumping mechanism is connected to the bottom of the bin wall of the bin body, the vacuum-pumping mechanism adopts a mechanical pump 15 and a molecular pump 16, an inlet of the molecular pump is connected with the bin body through a vacuum pipeline, an outlet of the molecular pump is connected with an inlet of the mechanical pump through a vacuum pipeline, and the other inlet of the mechanical pump is connected with the bin body through a vacuum pipeline. And valves are arranged on the vacuum pipeline between the molecular pump and the bin body, the vacuum pipeline between the molecular pump and the mechanical pump and the vacuum pipeline between the mechanical pump and the bin body, and are used for controlling the pipeline to be switched on and off.

The stable rotation speed of the mechanical pump reaches 1420r/min, and the vacuum pumping can only reach 10^-1Pa is about; can not meet the demand (as low as 10)^-4Pa below), therefore, the vacuumizing mechanism adopts a two-stage vacuumizing mode of a molecular pump and a mechanical pump, the pumping quantity of the molecular pump is 600L/s, and the limiting pressure can reach 10^-5Pa。

The plasma detector 17 is further arranged in the bin body, in the embodiment, the plasma detector adopts a Langmuir probe and is used for detecting the density of plasma, the plasma detector is connected with a telescopic mechanism, and the telescopic mechanism can drive the plasma detector to move in the bin body along the direction vertical to the axis of the bin body.

The telescopic mechanism adopts a lead screw transmission mechanism, the lead screw transmission mechanism adopts the existing structure and comprises a lead screw, a sliding block and the like, the sliding block is connected with a connecting rod 18 extending into the bin body, the connecting rod is connected with a plasma detector, the lead screw is connected with a handle, and a worker can drive the lead screw to rotate through the handle.

In other embodiments, the telescopic mechanism may also adopt a linear motor or an electric push rod, etc., as long as it can output linear motion.

An air inlet pipe 19 is arranged at the upper part of the bin body, an air outlet pipe 20 is arranged at the lower part of the bin body, the air inlet pipe and the air outlet pipe are both connected with the inner space of the bin body, valves are arranged on the air inlet pipe and the air outlet pipe, and the air inlet pipe is used for injecting inert gas into the bin body and generating plasma through ionization.

The lateral bin wall of the bin body is also provided with an ionization gauge 21, a resistance gauge 22 is arranged on the bottom bin wall, and when the air pressure of the bin body is 10⁵When the pressure is below 1Pa, a resistance gauge pressure gauge is adopted for measuring the vacuum degree of the bin body; when the pressure of the bin body is lower than 1Pa, the pressure gauge with the resistance gauge is not in accordance with the requirement, and the vacuum degree of the bin body is measured by the pressure gauge with the ionization gauge, wherein the measurement range is 10-10^-5Pa, the pressure monitoring of the cavity can be ensured under the condition of lower pressure.

And the side wall of the bin body is also provided with an observation window 23 for a worker to observe the experimental condition in the bin.

In this embodiment, the plasma detector, the ionization gauge and the resistance gauge are all connected with the control cabinet, and can transmit the detected information to the control cabinet, and the control cabinet is connected with the first power supply and the second power supply and can control the work of the first power supply and the second power supply.

When the testing device works, firstly, the internal space of the bin body is vacuumized to a set pressure intensity by using the mechanical pump and the molecular pump, then the first power supply and the second power supply work, the second power supply is electrified to the tungsten filament to excite the tungsten filament to release electrons, the first power supply applies positive bias between the accelerating grid and the tungsten filament to form an accelerating electric field, the released electrons are accelerated, the electrons collide with neutral ions in the bin body to generate plasma in the bin body, the plasma electron density can be adjusted by adjusting the current generated by the first power supply and the voltage applied by the second power supply, the plasma electron density is detected by using the plasma detector in real time until the set plasma electron density is reached, and a required plasma environment is provided for the next step of experiment.

The working principle of the embodiment is as follows:

according to the heat effect of the current, the temperature of the tungsten filament is increased along with the increase of the current after the tungsten filament is electrified. According to the Rich Zeeman-Schmidd formula, the relationship between the emission current density and the tungsten filament temperature is as follows:

wherein A represents an emission constant and T represents a tungsten filamentSource temperature, w₀Denotes the work function of the tungsten filament at absolute zero degrees, k being the boltzmann constant.

From the formula (4), the intensity of the emission current can be changed along with the change of the temperature of the tungsten filament, and the amount of the excited electrons can be controlled by adjusting the current flowing through the tungsten filament in combination with the heat effect of the current.

In the acceleration field, regardless of the complexity such as electron collision and E × B drift, there are:

eEd＝E_k-E₀(5)

e represents the charge amount of the element charge, E represents the field strength between the tungsten filament source and the acceleration grid, d represents the distance between the tungsten filament source and the acceleration grid, Ek represents the kinetic energy of the accelerated electrons, and E0 represents the initial kinetic energy of the electrons. The formula (5) shows that the electron kinetic energy Ek after acceleration is determined by the voltage between the tungsten filament source and the acceleration grid, i.e. the electron temperature is determined by the voltage between the tungsten filament source and the acceleration grid.

The accelerated electrons collide with neutral particles in the bin body, and momentum and energy transfer between the accelerated electrons and the neutral particles is achieved. As shown in fig. 4, the number of incident particles per unit volume at coordinate x at the time of collision interacts with the target particles within width dx, then:

dn_e＝-σn_en_gdx (6)

σ represents the cross-sectional data, ne represents the electron density incident on the target particle, and ng represents the target particle density.

Multiplying both sides of the equation by the velocity v to obtain the flux

v is the incident electron velocity, then:

the ratio of collisions of incident electrons with target particles per unit area can be expressed as:

therefore, it is

WhereinIn order to be the initial flux,calculating collision frequency v according to the relation between the mean free path lambda of the incident electrons and the velocity v of the incident electrons_cComprises the following steps:

the greater the particle impact frequency, the greater the number of impacts per unit time, the greater the density of plasma produced. As shown in the above formulas (4), (5) and (10), the ionization degree of the measurement region is related to the tungsten filament current, the accelerating electric field intensity and the target particle density, and the structure of the effect on the electron density in the bin body is shown in FIG. 5.

According to the structure diagram of the electronic influence factors, the stability of the adjusting parameters is considered, and for the selected tungsten filament structure parameters, the electron density of the plasma is controlled by adjusting the current flowing through the tungsten filament source and the intensity of the accelerating electric field under the condition of keeping the pressure in the cavity stable.

The working principle is tested:

the experiment will be measured from the longitudinal and transverse directions of the cavity, the electron density of each point is measured by adjusting the current flowing through the tungsten filament and the accelerating electric field intensity, and the experimental parameters are set as shown in table 1.

Table 1 experimental parameter settings

According to the principle of thermionic emission, when a tungsten filament is heated to a certain temperature, electrons in the tungsten filament have enough energy to overcome potential barriers on the surface of metal, the electrons can overflow the tungsten filament, the overflowing electrons can generate directional movement of the electrons under the acceleration of an electric field, a certain current is generated when part of the electrons touch an acceleration grid, and the stability of the current determines the stability of plasma in a cavity environment. While keeping the tungsten filament source current at 12A, according to Kirchhoff's Current Law (KCL), different electric field intensities were applied to measure the current between the tungsten filament source and the accelerating grid, and the data change curve is shown in FIG. 6. In the whole test process, because the airflow of the bin body is in a dynamic balance state, the detection current has small fluctuation under the corresponding electric field intensity, the maximum range is less than 5uA, and the current source has good stability.

Longitudinally distributing 5 Langmuir probes at intervals of 4cm in the cavity, and respectively applying an electric field strength of 1.5 × 10 under the condition of keeping the tungsten filament power 303W³V/m、1.75×10³V/m and 2X 10³V/m, the longitudinal distribution of the cavity plasma is diagnosed, the electron density distribution is shown in figure 7, and in figure 7, the horizontal axis represents the distance between the probe and the molybdenum net along the axis direction of the cabin body. The axial direction of the bin body is defined as a longitudinal direction, and the direction vertical to the longitudinal direction is defined as a transverse direction.

The electron density of each test point is mainly distributed in 10¹⁰/m³-10¹¹/m³The electron density in the cavity is gradually increased along with the increase of the field intensity as can be seen from a single test point; under the condition of equal field intensity, the electron density at the test point of each probe has the same descending trend; the ideal electron density can be obtained by reasonably selecting the probe position according to the longitudinal electron density distribution curve.

While maintaining the accelerating electric field at 1.25X 10³Under the condition of V/m, a probe 12cm away from a molybdenum net is adopted, the electrifying current of the tungsten filament is changed, the quantity of electrons excited by the tungsten filament is related to the electrifying current of the tungsten filament according to the thermionic emission theory, and the quantity of electrons excited by the tungsten filament determines the electron density in a measuring area. The current is increased from 11.8A to 12.2A, and the electron density detected by the transverse electron density diagnostic probe is also 4.0 multiplied by 10⁹/m³-1.12×10¹⁰/m³Increase to 1.0X 10¹⁰/m³-1.2×10¹¹/m³. According to the variation trend of fixed points, the lower electron density can be obtained only by properly reducing the electrifying current of the tungsten filament; for obtaining higher electron density, the method of increasing tungsten filament current is not used any more to increase the electron density, because the tungsten filament generates a large amount of heat while increasing the tungsten filament current, and the overhigh temperature is a severe test for the test equipment, so that the electron density in the measurement area is continuously increased by increasing the accelerating electric field intensity under the condition of keeping the tungsten filament current unchanged, the test result is shown in fig. 8, and the horizontal axis in fig. 8 represents the transverse moving distance of the probe.

As shown in FIG. 9, the electric field intensity was adjusted to 2.5X 10³At V/m, the electron density can reach 9 x 10¹¹/m 3; as can be seen from the analysis of FIG. 8 and FIG. 9, the electron density of the space plasma layer can be fully achieved by adjusting the equipment parameters, and the horizontal axis in FIG. 9 represents the lateral movement distance of the probe.

Experiments prove that under the condition of keeping the bin pressure unchanged, the range of the electron density in the bin body and the space electron density can be close by adjusting the electrifying current of the tungsten filament source and accelerating the electric field intensity. Compared with the density of plasma generated by glow discharge, the density range of the plasma generated by the method is more consistent with the density range of space plasma. The device structure principle is simple relatively, has the laboratory that requires to low plasma density and establishes more easily and builds. At present, the device is applied to a Langmuir probe diagnosis system, and plasma in a chamber has good stability through the analysis of parameters of the detection of the plasma environment by the probe.

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.