A cascade plasma generator

Abstract

The invention relates to the field of plasma technology, and discloses a cascade plasma generator, which comprises a cathode assembly, a cathode seat, a cascade assembly and an anode, wherein the cathode assembly comprises an arc-starting needle, an electron emission needle and an elastic connector, wherein the arc-starting needle is elastically connected to the electron emission needle through the elastic connector and is slidably arranged in a sliding channel; the elastic connector is compressed so that the bottom end of the arc-starting needle protrudes from the bottom end of the electron emission needle, and when arcing, the tip of the arc-starting needle discharges to realize ionization of working gas to generate plasma; the elastic compression member is released so that the bottom end of the electron emission needle protrudes from the bottom end of the arc-starting needle, and the electron emission needle emits electrons, thereby preventing the arc-starting needle from being always in a chamber where gas ionization occurs, and then preventing the arc-starting needle from having a large amount of impurities accumulated and the needle tip from melting, thereby reducing the replacement frequency of the arc-starting needle, reducing the maintenance cost of the device and ensuring the normal progress of the experiment.

Description

Technical Field

[0001] The invention relates to the field of plasma technology, in particular to a cascade plasma generator. Background Art

[0002] A plasma generator is a device that uses artificial methods to obtain plasma. With the deepening of research on plasma technology in new materials, material modification, coating, chemical processes and new energy, there is an urgent need for a plasma generator that can provide high-power and high-density plasma.

[0003] Among various types of plasma generators, cascade plasma generators have the characteristics of large beam current, high density, and high radiation flux. They are widely used in basic problems of the interaction between plasma and materials, such as physical sputtering and chemical etching of materials, hydrogen and helium retention / bubbling problems in materials, and simulation of the impact of plasma rupture on materials.

[0004] Cascade plasma generators usually apply high voltage between the cathode and anode to break down the gas between the electrodes and generate an arc. When the arc passes through the gas, the atoms and molecules in the gas are ionized to form charged particles and plasma. In order to facilitate gas breakdown to generate an arc, the end of the cathode is usually made into a tip using the tip discharge principle, or a pointed arc-starting needle is fixed on the cathode to induce arc discharge; however, in the process of the plasma generator, the cathode tip or the arc-starting needle must not only induce arc discharge, but also act as an electron emitter in the plasma generation process, which requires the arc-starting needle to be always in the chamber where the gas is ionized; however, after a period of time, a large amount of material will accumulate at the tip of the arc-starting needle, forming hard impurities that wrap around the tip, and because the tip is frequently bombarded by plasma, the fragile tip will be melted, forming a "tumor" accumulated at the tip position, which will make it impossible to generate tip discharge during the next operation, thereby making the cascade plasma generator unable to work; the existing solution is to replace the arc-starting needle regularly, but this method requires multiple components to be disassembled and assembled, and frequent disassembly and assembly will affect the assembly gap between components and delay the experimental process, and increase the maintenance cost of the device. Summary of the invention

[0005] The purpose of the present invention is to provide a cascade plasma generator to solve the problems that a large amount of impurities are accumulated on the tip of the existing arc-starting needle and the tip is easy to melt.

[0006] In order to achieve the above object, the present invention provides a cascade plasma generator, which includes a cathode assembly, a cathode holder, a cascade assembly and an anode;

[0007] The anode is spaced below the cathode seat; the cascade assembly is disposed between the cathode seat and the anode, and connects the anode and the cathode seat;

[0008] The cathode seat is provided with a connecting channel, the connecting channel is arranged along the axial direction of the cathode seat and passes through the upper and lower surfaces of the cathode seat; the anode is provided with an emission channel, the emission channel is arranged along the axial direction of the anode and passes through the upper and lower surfaces of the anode; the cascade assembly is provided with a cascade channel passing through the upper and lower surfaces thereof; the connecting channel, the cascade channel and the emission channel are connected in sequence;

[0009] The cathode seat is also provided with a gas channel, one end of which is provided on the outer peripheral surface of the cathode seat, and the other end of which is connected with the connecting channel;

[0010] The cathode assembly comprises an arc-starting needle, an electron-emitting needle and an elastic connector; the electron-emitting needle is inserted into the connecting channel, and the bottom end of the electron-emitting needle is located in the connecting channel, and the outer periphery of the electron-emitting needle is sealed and insulated with the cathode seat;

[0011] A sliding channel is provided in the electron emission needle, and the sliding channel is extended along the axial direction of the electron emission needle and passes through the upper and lower surfaces of the electron emission needle;

[0012] The arc-starting needle is slidably arranged in the sliding channel, and the arc-starting needle is sealed and connected to the electron emission needle. The top of the arc-starting needle is elastically connected to the electron emission needle through the elastic connecting piece. When the elastic connecting piece is compressed, the bottom end of the arc-starting needle protrudes from the bottom end of the electron emission needle. When the elastic connecting piece is reset, the bottom end of the electron emission needle protrudes from the bottom end of the arc-starting needle.

[0013] Furthermore, the bottom end surface area of ​​the arc starting needle is smaller than the bottom end surface area of ​​the electron emission needle.

[0014] Furthermore, the diameter of the bottom of the electron emission needle gradually decreases from top to bottom, and the bottom end surface of the electron emission needle is a plane, and the plane is perpendicular to the axis of the electron emission needle.

[0015] Furthermore, a first cooling channel is provided in the electron emission needle, the first cooling channel is arranged around the outer periphery of the sliding channel, and extends along the axial direction of the electron emission needle;

[0016] A cooling inlet and a cooling outlet are respectively provided on both sides of the outer peripheral surface of the electron emission needle, and the cooling inlet and the cooling outlet are respectively communicated with the first cooling channel.

[0017] Furthermore, the cathode assembly also includes an insulating tube;

[0018] The insulating tube is sleeved on the outer periphery of the electron emission needle, and a portion of the insulating tube is inserted into the connecting channel, so that the electron emission needle is insulated from the cathode seat.

[0019] Furthermore, the locking assembly further includes an insulating pad;

[0020] The insulating pad comprises a sleeve portion and a pressing portion, wherein the sleeve portion is sleeved on the outer periphery of the electron emission needle, and the pressing portion is arranged around the outer periphery of the sleeve portion and extends radially outward;

[0021] The outer peripheral surface of the sleeve portion is in close contact with the inner wall of the opening, the diameter of the pressing portion is larger than the diameter of the opening, and the bottom surface of the pressing portion is in close contact with the top surface of the sealing ring.

[0022] Furthermore, the top opening of the sealing stud has a tapered surface with an outer diameter gradually decreasing from top to bottom;

[0023] The outer peripheral surface of the sealing ring is a conical surface that is matched with the top opening of the sealing stud.

[0024] Furthermore, the sealing stud and the sealing nut are made of different materials respectively.

[0025] Further, the elastic connecting member includes a bellows and a bellows flange fixed to the top of the bellows;

[0026] The bellows flange is fixedly connected to the top of the arc-starting needle, and the arc-starting needle is inserted into the bellows;

[0027] The bellows is sealingly connected to the top of the electron emitting needle.

[0028] Compared with the prior art, the cascade plasma generator provided by the present invention has the following beneficial effects:

[0029] The present invention provides a cascade plasma generator, which comprises a cathode assembly, a cathode seat, a cascade assembly and an anode; the cascade plasma generator is composed of the cathode assembly, the cascade assembly and the anode, a high voltage is applied between the cathode assembly and the anode, and a tip discharge is achieved by sliding an arcing needle inserted into the electron emission needle, thereby breaking down the working gas introduced from the gas channel to generate an arc, ionizing the working gas to generate plasma, and the plasma is emitted from the connecting channel and through the cascade channel and the emission channel to the outside of the cascade plasma generator, thereby achieving the purpose of providing plasma; because when the elastic connecting piece is compressed, the bottom end of the arcing needle protrudes from the bottom end of the electron emission needle, and when the elastic connecting piece is reset, the electron The bottom end of the emission needle protrudes from the bottom end of the arc-starting needle, so that the bottom end of the arc-starting needle is located in the sliding channel; therefore, when the cascade plasma generator is started, the elastic connecting piece is compressed so that the bottom end of the arc-starting needle protrudes from the bottom end of the electron emission needle, and the tip discharge is induced by the arc-starting needle to break through the working gas. After arcing, the elastic connecting piece is reset, so that the bottom end of the arc-starting needle is located in the sliding channel, that is, the arc-starting needle is retracted into the sliding channel, and the electron emission needle acts as an electron emitter, thereby avoiding the arc-starting needle from being always in the chamber where gas ionization occurs, and then the needle tip of the arc-starting needle will not have the problem of large amount of impurities accumulation and needle tip melting, thereby reducing the replacement frequency of the arc-starting needle, reducing the maintenance cost of the device and ensuring the normal progress of the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic cross-sectional structure diagram of a cascade plasma generator according to an embodiment of the present invention;

[0031] Figure 2 yes Figure 1 A magnified schematic diagram of the middle A area;

[0032] Figure 3 yes Figure 1 A magnified schematic diagram of the middle B area;

[0033] Figure 4 yes Figure 1 Enlarged schematic diagram of area C in the middle.

[0034] In the figure, 100, cascade plasma generator; 1, cathode assembly; 11, arc-starting needle; 12, electron emission needle; 120, sliding channel; 121, first cooling channel; 122, cooling inlet; 123, cooling outlet; 13, elastic connector; 131, bellows; 132, bellows flange; 14, insulating tube; 2, cathode seat; 20, connecting channel; 201, sealing part; 202, connecting part; 21, gas channel; 3, cascade assembly; 30, cascade channel; 31, cascade sheet; 310, cooling port; 311, second cooling channel; 32, cascade cooling tube; 4, anode; 40, emission channel; 5, locking assembly; 51, sealing stud; 52, sealing nut; 520, sealing cavity; 521, opening; 53, sealing ring; 54, insulating pad; 541, fitting part; 542, pressing part. DETAILED DESCRIPTION

[0035] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0036] like Figure 1~Figure 4As shown, a cascade plasma generator 100 according to an embodiment of the present invention comprises a cathode assembly 1, a cathode seat 2, a cascade assembly 3 and an anode 4; the anode 4 is arranged below the cathode seat 2 at intervals; the cascade assembly 3 is arranged between the cathode seat 2 and the anode 4, and connects the anode 4 and the cathode seat 2; a connecting channel 20 is provided in the cathode seat 2, the connecting channel 20 is extended along the axial direction of the cathode seat 2 and passes through the upper and lower surfaces of the cathode seat 2; an emission channel 40 is provided in the anode 4, the emission channel 40 is extended along the axial direction of the anode 4 and passes through the upper and lower surfaces of the anode 4; a cascade channel 30 is provided on the cascade assembly 3 and passes through the upper and lower surfaces thereof; the connecting channel 20, the cascade channel 30 and the emission channel 40 are connected in sequence; the cathode seat 2 is also provided with a gas channel 21, one end of the gas channel 21 is provided on the outer peripheral surface of the cathode seat 2, and the other end is connected to the connecting channel 20; the cathode assembly Component 1 includes an arc-starting needle 11, an electron emission needle 12 and an elastic connecting piece 13; the electron emission needle 12 is inserted into the connecting channel 20, and the bottom end of the electron emission needle 12 is located in the connecting channel 20, and the outer periphery of the electron emission needle 12 is sealed and insulated with the cathode seat 2; a sliding channel 120 is provided in the electron emission needle 12, and the sliding channel 120 is extended along the axial direction of the electron emission needle 12 and passes through the upper and lower surfaces of the electron emission needle 12; the arc-starting needle 11 is slidably penetrated in the sliding channel 120, and the arc-starting needle 11 is sealed and connected to the electron emission needle 12, the top of the arc-starting needle 11 is elastically connected to the electron emission needle 12 through the elastic connecting piece 13, when the elastic connecting piece 13 is compressed, the bottom end of the arc-starting needle 11 protrudes from the bottom end of the electron emission needle 12, and when the elastic connecting piece 13 is reset, the bottom end of the electron emission needle 12 protrudes from the bottom end of the arc-starting needle 11.

[0037] Based on the above technical solution, the cathode assembly 1 is installed through the cathode seat 2, and the cathode assembly 1, the cascade assembly 3 and the anode 4 form a cascade plasma generator 100. A high voltage is applied between the cathode assembly 1 and the anode 4, and the tip discharge is achieved by sliding the arc needle 11 through the electron emission needle 12, thereby breaking down the working gas introduced from the gas channel 21 to generate an arc, and the working gas is ionized to generate plasma. The plasma starts from the connecting channel 20 and is emitted to the outside of the cascade plasma generator 100 through the cascade channel 30 and the emission channel 40, thereby achieving the purpose of providing plasma; because when the elastic connecting member 13 is compressed, the bottom end of the arc needle 11 protrudes from the bottom end of the electron emission needle 12, and when the elastic connecting member 13 is reset, the electron emission needle 12 The bottom end of the arc-starting needle 11 protrudes from the bottom end of the electron emission needle 12; therefore, when the cascade plasma generator 100 is started, the elastic connecting piece 13 is compressed so that the bottom end of the arc-starting needle 11 protrudes from the bottom end of the electron emission needle 12, and the tip discharge is induced by the arc-starting needle 11 to break through the working gas. When the arc is generated, the elastic connecting piece 13 is reset so that the bottom end of the electron emission needle 12 protrudes from the bottom end of the arc-starting needle 11, that is, the arc-starting needle 11 is retracted into the sliding channel 120 of the electron emission needle 12, and the electron emission needle 12 acts as an electron emitter, thereby avoiding the arc-starting needle 11 from being always in the chamber where the gas is ionized, and then the needle tip of the arc-starting needle 11 will not have the problem of a large amount of impurities accumulating and the needle tip melting, thereby reducing the replacement frequency of the arc-starting needle 11, reducing the maintenance cost of the device and ensuring the normal progress of the experiment.

[0038] Preferably, if Figure 1 As shown, in this embodiment, the cascade assembly 3 includes a plurality of cascade sheets 31 stacked in sequence from top to bottom, each of the cascade sheets 31 is provided with a channel running through the upper and lower surfaces thereof, and the channels are connected in sequence to form the cascade channel 30 .

[0039] Preferably, if Figure 1 and Figure 4 As shown, in order to facilitate the cooling of the cascade plate 31, the cascade assembly 3 also includes a number of cascade cooling tubes 32, the number of which is the same as the cascade plate 31; cooling ports 310 are provided on the outer peripheral surface of each cascade plate 31, and a second cooling channel 311 is opened in each cascade plate, the cooling ports 310 are connected to the second cooling channel 311, and each cascade cooling tube 32 is connected to the cooling port 310 one by one; thereby, each cascade plate 31 is cooled individually, the cooling efficiency is improved, and the cascade plate 31 is easily replaced individually.

[0040] Furthermore, if Figure 1As shown, the bottom end surface area of ​​the arc starting needle 11 is smaller than the bottom end surface area of ​​the electron emission needle 12. Since the arc starting needle 11 plays a role in initiating tip discharge, the bottom end surface area of ​​the arc starting needle 11 should be as small as possible to facilitate tip discharge, while the bottom end surface area of ​​the electron emission needle 12 does not need to be as small as the bottom end surface area of ​​the arc starting needle 11. A larger bottom end surface area can increase the electron emission degree and improve the density of the plasma source.

[0041] Furthermore, if Figure 1 As shown, the diameter of the bottom of the electron emission needle 12 gradually decreases from top to bottom. This structural design facilitates the processing of the sliding channel 120 in the electron emission needle 12. The bottom end face of the electron emission needle 12 is a plane, and the plane is perpendicular to the axis of the electron emission needle 12. Since electron emission mainly occurs at the bottom end face of the electron emission needle 12, by making the bottom end face a plane and the plane perpendicular to the axis of the electron emission needle 12, on the one hand, it is convenient to process the bottom end face, and on the other hand, it can more accurately control the emission direction of the electrons, thereby controlling the direction of the generated plasma.

[0042] Furthermore, if Figure 1 and Figure 2 As shown, a first cooling channel 121 is provided in the electron emission needle 12, and the first cooling channel 121 is arranged around the outer periphery of the sliding channel 120 and extends along the axial direction of the electron emission needle 12; a cooling inlet 122 and a cooling outlet 123 are respectively provided on both sides of the outer peripheral surface of the electron emission needle 12, and the cooling inlet 122 and the cooling outlet 123 are respectively connected to the first cooling channel 121; a coolant, such as common water, is introduced into the cooling channel 121 through the cooling inlet 122, and the coolant is then made to flow out from the cooling outlet 123, so as to cool the electron emission needle 12 to prevent the electron emission needle 12 from overheating, thereby ensuring the normal operation of the cascade plasma generator 100.

[0043] Furthermore, if Figure 1 As shown, in order to achieve the insulated connection between the electron emission needle 12 and the cathode seat 2, the cathode assembly 1 also includes an insulating tube 14; the insulating tube 14 is sleeved on the outer periphery of the electron emission needle 12, and the insulating tube 14 is partially inserted into the connecting channel 20, so that the electron emission needle 12 is insulated from the cathode seat 2.

[0044] Preferably, in this embodiment, the insulating tube 14 is made of ceramic.

[0045] Furthermore, if Figure 1 and Figure 2As shown, the cascade plasma generator 100 also includes a locking assembly 5; the locking assembly 5 includes a sealing stud 51, a sealing nut 52 and a sealing ring 53; the sealing stud 51 is sleeved on the top of the outer periphery of the insulating tube 14, the bottom of the sealing stud 51 is sealed and connected to the connecting channel 20, and the outer periphery of the sealing stud 51 is provided with a threaded portion; the sealing ring 53 is sleeved on the electron emission needle 12; the sealing nut 52 has a sealing cavity 520, and the top of the sealing nut 52 is provided with an opening 521 connected to the sealing cavity; the sealing nut 52 is sleeved on the electron emission needle 12 and is threadedly connected to the sealing stud 51, and the sealing ring 53 is pressed between the sealing stud 51 and the electron emission needle 12, thereby realizing a sealed connection between the electron emission needle 12 and the cathode seat 2.

[0046] Preferably, if Figure 1 and Figure 2 As shown, the connecting channel 20 includes a sealing portion 201 and a connecting portion 202 arranged in sequence from top to bottom, and the diameter of the sealing portion 201 is larger than the diameter of the connecting portion 202; the bottom of the sealing stud 51 is sealed and connected to the sealing portion 201 to facilitate the installation, connection and positioning of the sealing stud 51.

[0047] Furthermore, if Figure 1 and Figure 2 As shown, the locking assembly 5 also includes an insulating pad 54; the insulating pad 54 includes a fitting portion 541 and a pressing portion 542, the fitting portion 541 is sleeved on the outer periphery of the electron emission needle 12, and the pressing portion 542 is arranged around the outer periphery of the fitting portion 541 and extends radially outward; the outer peripheral surface of the fitting portion 541 is tightly against the inner wall of the opening 521, the diameter of the pressing portion 542 is larger than the diameter of the opening 521, and the bottom surface of the pressing portion 542 is tightly against the top surface of the sealing ring 53, so that when the sealing nut 52 is screwed and tightened with the sealing stud 51, the pressing portion 542 squeezes the sealing ring 53, and further presses the sealing ring 53 between the sealing stud 51 and the electron emission needle 12.

[0048] Furthermore, if Figure 1 and Figure 2 As shown, the top opening of the sealing stud 51 has a conical surface with an outer diameter gradually decreasing from top to bottom; the outer peripheral surface of the sealing ring 53 is a conical surface that cooperates with the top opening of the sealing stud, and the conical sealing ring 53 and the conical surface at the top opening of the sealing stud 51 cooperate with each other, so that when the sealing nut 52 and the sealing stud 51 are screwed and tightened, the sealing ring 53 is pressed between the sealing stud 51 and the electron emission needle 12, so as to ensure the reliability of the sealed connection between the electron emission needle 12 and the cathode seat 2.

[0049] Furthermore, the sealing stud 51 and the sealing nut 52 are made of different materials respectively; in this embodiment, the sealing stud 51 is made of stainless steel, and the sealing nut 52 is made of brass, so that the threads of different materials will not be "bite-tightened" when tightened, facilitating subsequent disassembly and maintenance.

[0050] Furthermore, if Figure 1 and Figure 3 As shown, the elastic connecting member 13 includes a bellows 131 and a bellows flange 132 fixedly arranged on the top of the bellows 131; the bellows flange 132 is fixedly connected to the top of the arc-starting needle 11, and the arc-starting needle 11 is inserted into the bellows 131; the bellows 131 is sealingly connected to the top of the electron emitting needle 12; and the elastic connection between the arc-starting needle 11 and the electron emitting needle 12 is realized through the bellows 131.

[0051] The working process of the present invention is as follows: compressing the bellows 131 so that the bottom end of the arcing needle 11 protrudes from the bottom end of the electron emission needle 12, energizing the arcing needle 11 and the anode 4, forming a potential difference between the arcing needle 11 and the anode 4, causing tip discharge by the needle tip of the arcing needle 11, thereby ionizing the working gas entering from the gas channel 21, and then forming plasma; after a stable plasma is formed, releasing the bellows 131 to automatically reset it, the bottom end of the electron emission needle 12 protrudes from the bottom end of the arcing needle 11, and electrons are continuously emitted from the front end of the electron emission needle 12 to continuously provide a stable plasma, and compared with the bottom end surface area of ​​the arcing needle 11, the bottom end surface area of ​​the electron emission needle 12 is larger, which can increase the electron emission degree to increase the density of the plasma.

[0052] In summary, the embodiment of the present invention provides a cascade plasma generator 100, which includes a cathode assembly 1, a cathode holder 2, a cascade assembly 3 and an anode 4; the cathode assembly 1 includes an arcing needle 11, an electron emission needle 12 and an elastic connecting member 13; the cathode assembly 1 is installed through the cathode holder 2, and the cascade plasma generator 100 is composed of the cathode assembly 1, the cascade assembly 3 and the anode 4, a high voltage is applied between the cathode assembly 1 and the anode 4, and the arcing needle 11 slidingly inserted in the electron emission needle 12 is used to achieve tip discharge, thereby breaking down the working gas introduced from the gas channel 21 to generate an arc, and the working gas is ionized to generate plasma, and the plasma starts from the connecting channel 20 and is emitted to the outside of the cascade plasma generator 100 via the cascade channel 30 and the emission channel 40, thereby achieving the purpose of providing plasma; because when the elastic connecting member 13 is compressed, the bottom end of the arcing needle 11 protrudes out of the The bottom end of the electron emission needle 12 is protruded from the bottom end of the arcing needle 11 when the elastic connecting piece 13 is reset; therefore, when the cascade plasma generator 100 is started, the elastic connecting piece 13 is compressed so that the bottom end of the arcing needle 11 protrudes from the bottom end of the electron emission needle 12, and the tip discharge is induced by the arcing needle 11 to break through the working gas. When the arc is generated, the elastic connecting piece 13 is reset so that the bottom end of the electron emission needle 12 protrudes from the bottom end of the arcing needle 11, that is, the arcing needle 11 is retracted into the sliding channel 120 of the electron emission needle 12, and the electron emission needle 12 acts as an electron emitter, thereby avoiding the arcing needle 11 from being always in the chamber where the gas is ionized, and then the needle tip of the arcing needle 11 will not have the problem of a large amount of impurities accumulating and the needle tip melting, thereby reducing the replacement frequency of the arcing needle 11, reducing the maintenance cost of the device and ensuring the normal progress of the experiment.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A cascade plasma generator, characterized in that: It includes a cathode assembly, a cathode holder, a cascade assembly and an anode; The anode is spaced below the cathode seat; the cascade assembly is disposed between the cathode seat and the anode, and connects the anode and the cathode seat; The cathode seat is provided with a connecting channel, the connecting channel is arranged along the axial direction of the cathode seat and passes through the upper and lower surfaces of the cathode seat; the anode is provided with an emission channel, the emission channel is arranged along the axial direction of the anode and passes through the upper and lower surfaces of the anode; the cascade assembly is provided with a cascade channel passing through the upper and lower surfaces thereof; the connecting channel, the cascade channel and the emission channel are connected in sequence; The cathode seat is also provided with a gas channel, one end of which is provided on the outer peripheral surface of the cathode seat, and the other end of which is connected with the connecting channel; The cathode assembly comprises an arc-starting needle, an electron-emitting needle and an elastic connector; the electron-emitting needle is inserted into the connecting channel, and the bottom end of the electron-emitting needle is located in the connecting channel, and the outer periphery of the electron-emitting needle is sealed and insulated with the cathode seat; A sliding channel is provided in the electron emission needle, and the sliding channel is extended along the axial direction of the electron emission needle and passes through the upper and lower surfaces of the electron emission needle; The arc-starting needle is slidably arranged in the sliding channel, and the arc-starting needle is sealed and connected to the electron emission needle. The top of the arc-starting needle is elastically connected to the electron emission needle through the elastic connecting piece. When the elastic connecting piece is compressed, the bottom end of the arc-starting needle protrudes from the bottom end of the electron emission needle. When the elastic connecting piece is reset, the bottom end of the electron emission needle protrudes from the bottom end of the arc-starting needle. The bottom end surface area of ​​the arc-starting needle is smaller than the bottom end surface area of ​​the electron emission needle; The diameter of the bottom of the electron emission needle gradually decreases from top to bottom, and the bottom end surface of the electron emission needle is a plane, and the plane is perpendicular to the axis of the electron emission needle.

2. The cascade plasma generator according to claim 1, characterized in that: A first cooling channel is provided in the electron emission needle, the first cooling channel is arranged around the outer periphery of the sliding channel and extends along the axial direction of the electron emission needle; A cooling inlet and a cooling outlet are respectively provided on both sides of the outer peripheral surface of the electron emission needle, and the cooling inlet and the cooling outlet are respectively communicated with the first cooling channel.

3. The cascade plasma generator according to claim 1, characterized in that: The cathode assembly also includes an insulating tube; The insulating tube is sleeved on the outer periphery of the electron emission needle, and a portion of the insulating tube is inserted into the connecting channel, so that the electron emission needle is insulated from the cathode seat.

4. The cascade plasma generator according to claim 3, characterized in that: Also included is a locking assembly; The locking assembly comprises a sealing stud, a sealing nut and a sealing ring; The sealing stud is sleeved on the top of the outer circumference of the insulating tube, the bottom of the sealing stud is sealed and connected to the connecting channel, and the outer circumference of the sealing stud is provided with a threaded portion; The sealing ring is sleeved on the electron emitting needle; The sealing nut has a sealing cavity, and an opening communicating with the sealing cavity is provided on the top of the sealing nut; the sealing nut is sleeved on the electron emission needle and threadedly connected with the sealing stud, and the sealing ring is pressed between the sealing stud and the electron emission needle.

5. The cascade plasma generator according to claim 4, characterized in that: The locking assembly also includes an insulating pad; The insulating pad comprises a sleeve portion and a pressing portion, wherein the sleeve portion is sleeved on the outer periphery of the electron emission needle, and the pressing portion is arranged around the outer periphery of the sleeve portion and extends radially outward; The outer peripheral surface of the sleeve portion is in close contact with the inner wall of the opening, the diameter of the pressing portion is larger than the diameter of the opening, and the bottom surface of the pressing portion is in close contact with the top surface of the sealing ring.

6. The cascade plasma generator according to claim 5, characterized in that: The top opening of the sealing stud has a tapered surface with an outer diameter gradually decreasing from top to bottom; The outer peripheral surface of the sealing ring is a conical surface that is matched with the top opening of the sealing stud.

7. The cascade plasma generator according to claim 4, characterized in that: The sealing stud and the sealing nut are made of different materials respectively.

8. The cascade plasma generator according to any one of claims 1 to 7, characterized in that: The elastic connecting member comprises a bellows and a bellows flange fixed on the top of the bellows; The bellows flange is fixedly connected to the top of the arc-starting needle, and the arc-starting needle is inserted into the bellows; The bellows is sealingly connected to the top of the electron emitting needle.

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