Integrated radio frequency inductive coupling cathode

Abstract

The invention relates to the technical field of electric propulsion, in particular to an integrated radio frequency inductive coupling cathode which comprises a gas circuit connector, gas circuit insulation ceramic, pulse electrode isolation ceramic, a plasma discharge cavity, an ion collecting electrode and a cathode top, and a transition device is arranged between the gas circuit connector and the gas circuit insulation ceramic; a pulse ignition negative electrode is arranged between the gas path insulation ceramic and the pulse electrode isolation ceramic; a pulse ignition positive electrode is arranged between the pulse electrode isolation ceramic and the plasma discharge cavity; the ion collecting electrode is buckled above the plasma discharge cavity in a sleeving manner; and the cathode top is fixed above the ion collecting electrode. The problem that the service life of a discharge electrode arranged in a plasma discharge cavity is short is solved, small-flow and low-radio-frequency power coupling discharge can be achieved, the requirement for complexity of a radio-frequency power supply system is lowered, and the design targets of light weight and integration of the radio-frequency inductive coupling cathode are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of electric propulsion, and more particularly, to an integrated radio frequency inductively coupled cathode. Background Art

[0002] As one of the important research directions of electric propulsion technology, radio frequency ion electric propulsion has small coupling of discharge performance adjustment parameters, which is convenient for formulating performance adjustment control algorithms. At the same time, radio frequency ion electric propulsion has a simple structure, is easy to scale down, and is easy to integrate, showing obvious advantages in terms of lightweight and integration.

[0003] The radio frequency cathode is an important component of radio frequency ion electric propulsion and is the primary link for radio frequency ion electric propulsion to achieve its functions. The main principle of radio frequency ion electric propulsion is that under the action of radio frequency excitation, a magnetic field along the axial direction of the discharge cavity and an angular vortex electric field are inductively coupled in the discharge cavity of the radio frequency thruster. Further, by applying a pulsed voltage to the grid, the electrons emitted from the radio frequency cathode are attracted into the discharge cavity of the radio frequency thruster. These free electrons move under the action of the induced vortex electric field and then collide with the neutral atoms in the discharge cavity of the radio frequency thruster to form a continuous and stable plasma discharge. Finally, the ions are focused and accelerated through the electrostatic grid system and ejected to form thrust.

[0004] Currently, there are mainly three structures and working modes of radio frequency cathodes: 1. The discharge electrode is placed inside the plasma discharge cavity of the radio frequency cathode, and primary electrons are produced through breakdown discharge inside the discharge cavity, and then the working gas is ionized under the coupling of the radio frequency induction electromagnetic field. However, in this structure and working mode, the internal electrode is in a state of radio frequency induction heating for a long time, and the ions in the discharge cavity will strongly sputter and corrode the internal electrode, seriously reducing the application reliability and service life of the discharge electrode; 2. Radio frequency coupled discharge under large flow rate and high radio frequency power impact. In this mode, the discharge electrode is cancelled, but a large flow rate of air pressure impact needs to be formed inside the discharge cavity, and then the gas is directly ionized under the condition of high-power radio frequency energy feeding. However, in this structure and working mode, the application strategy is relatively cumbersome, requiring a storage and supply valve adjustment system and a wide-range radio frequency power supply to cooperate, and the working reliability is low; 3. Radio frequency coupled discharge in the intake duct. This mode is similar to the radio frequency coupled discharge under large flow rate and high radio frequency power impact. The difference is that radio frequency energy is fed into the intake duct with a relatively small diameter to ionize the gas inside the intake duct, reducing the need for large flow rate and high radio frequency power. However, the coil structure required by this method is complex, adding a set of radio frequency power supply systems, greatly reducing the advantages of lightweight and integration of radio frequency ion electric propulsion. Summary of the Invention

[0005] The present application provides an integrated radio frequency inductively coupled cathode, achieving the design goals of lightweight and integration of the radio frequency inductively coupled cathode and solving the problem of application reliability of the radio frequency inductively coupled cathode.

[0006] To achieve the above object, the present application provides an integrated radio frequency inductive coupling cathode, including a gas path connector, a gas path insulating ceramic, a pulse electrode isolation ceramic, a plasma discharge chamber, an ion collection electrode, and a cathode top. Among them: a transition device is provided between the gas path connector and the gas path insulating ceramic; a pulse ignition negative electrode is provided between the gas path insulating ceramic and the pulse electrode isolation ceramic; a pulse ignition positive electrode is provided between the pulse electrode isolation ceramic and the plasma discharge chamber; the ion collection electrode is sleeved above the plasma discharge chamber; the cathode top is fixed above the ion collection electrode.

[0007] Further, the transition device is fixed to the gas path connector by arc welding or laser welding.

[0008] Further, the transition device and the gas path insulating ceramic are fixed by vacuum brazing; the pulse ignition negative electrode is fixed between the gas path insulating ceramic and the pulse electrode isolation ceramic by vacuum brazing; the pulse ignition positive electrode is fixed between the pulse electrode isolation ceramic and the plasma discharge chamber by vacuum brazing; the ion collection electrode is fixed above the plasma discharge chamber by vacuum brazing; the cathode top is fixed above the ion collection electrode by vacuum brazing.

[0009] Further, the material of the transition device is kovar alloy; the materials of the gas path insulating ceramic, the pulse electrode isolation ceramic, the plasma discharge chamber, and the cathode top are alumina ceramics; the materials of the pulse ignition negative electrode, the pulse ignition positive electrode, and the ion collection electrode are tungsten, molybdenum, or graphite.

[0010] Further, a radio frequency coil is fixedly arranged on the outer wall surface inside the plasma discharge chamber, and the radio frequency coil is arranged in a fixed pitch helix.

[0011] Further, it also includes a radio frequency cathode electrical connection device, which includes a pulse power supply, an impedance matcher, a radio frequency power supply, and a collection power supply. Among them: the positive pole of the pulse power supply is connected to the pulse ignition positive electrode, and the negative pole of the pulse power supply is connected to the pulse ignition negative electrode; the impedance matcher is electrically connected to both ends of the radio frequency coil; the radio frequency power supply is connected to the impedance matcher through a coaxial radio frequency cable; the negative pole of the collection power supply is connected to the ion collection electrode; the negative poles of the pulse power supply, the radio frequency power supply, and the positive pole of the collection power supply are all grounded.

[0012] Further, the axial length of the pulse ignition negative electrode is greater than the axial length of the pulse ignition positive electrode.

[0013] Further, the discharge end of the pulse ignition negative electrode is in the shape of an inclined sharp angle; the discharge end of the pulse ignition positive electrode is in the shape of a plane.

[0014] Further, an electron extraction port is provided at the center of the cathode top.

[0015] Further, the ion collection electrode is in the shape of an unclosed ring, and its outer diameter is smaller than the inner diameter of the plasma discharge chamber.

[0016] An integrated radio frequency inductively coupled cathode provided by the present application has the following beneficial effects:

[0017] In the present application, a discharge electrode is arranged inside the air inlet passage, so that the gas in the air inlet passage undergoes glow discharge to generate primary electrons, avoiding the problem of low service life of the discharge electrode arranged inside the plasma discharge chamber; meanwhile, the diameter of the air inlet passage is much smaller than the diameter of the plasma discharge chamber, and small-flow and low-radio-frequency-power coupled discharge can be realized. In addition, the pulse discharge mode is adopted, reducing the complexity requirements for the radio frequency power supply system. The overall integrated solution of one-piece dissimilar material arc or laser welding and vacuum brazing is adopted, achieving the design goals of lightweight and integration of the radio frequency inductively coupled cathode, and significantly improving the reliability of the application of the radio frequency inductively coupled cathode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present application, making other features, objectives, and advantages of the present application more obvious. The schematic embodiments and descriptions thereof of the present application are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0019] Figure 1 is a schematic diagram of an integrated radio frequency inductively coupled cathode provided by an embodiment of the present application;

[0020] Figure 2 is a schematic diagram of the electrical connection relationship of the integrated radio frequency inductively coupled cathode provided by an embodiment of the present application;

[0021] Figure 3 is a schematic diagram of a pulse ignition system provided by an embodiment of the present application;

[0022] Figure 4 is a schematic diagram of the ion collection electrode provided by an embodiment of the present application;

[0023] In the figure: 1 - gas path joint, 2 - gas path insulating ceramic, 3 - pulse electrode isolation ceramic, 4 - plasma discharge chamber, 5 - ion collection electrode, 6 - cathode top, 7 - transition device, 8 - pulse ignition negative electrode, 9 - pulse ignition positive electrode, 10 - radio frequency coil, 11 - pulse power supply, 12 - impedance matcher, 13 - radio frequency power supply, 14 - collection power supply. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0025] It should be noted that the terms "first", "second", etc. in the specification, claims and above-mentioned drawings of this application are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances for the embodiments of this application described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] In this application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation or be constructed and operated in a specific orientation.

[0027] Moreover, in addition to being able to represent an orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0028] In addition, the meaning of the term "plurality" should be two or more.

[0029] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will detail this application with reference to the drawings and in combination with the embodiments.

[0030] Such as Figure 1As shown in the figure, the present application provides an integrated radio frequency inductively coupled cathode, which includes a gas path connector 1, a gas path insulating ceramic 2, a pulse electrode isolation ceramic 3, a plasma discharge chamber 4, an ion collection electrode 5, and a cathode top 6. Among them: a transition device 7 is arranged between the gas path connector 1 and the gas path insulating ceramic 2; a pulse ignition negative electrode 8 is arranged between the gas path insulating ceramic 2 and the pulse electrode isolation ceramic 3; a pulse ignition positive electrode 9 is arranged between the pulse electrode isolation ceramic 3 and the plasma discharge chamber 4; the ion collection electrode 5 is sleeved above the plasma discharge chamber 4; the cathode top 6 is fixed above the ion collection electrode 5.

[0031] Specifically, the integrated radio frequency inductively coupled cathode provided by the embodiment of the present application gives full play to the advantages of the existing three radio frequency cathode structures and working modes. By adopting a discharge electrode built into the air inlet passage, gas glow discharge occurs in the air inlet passage to generate primary electrons, avoiding the problem of low life of the discharge electrode built into the plasma discharge chamber 4. At the same time, the diameter of the air inlet passage is much smaller than that of the plasma discharge chamber, enabling small-flow and low-radio-frequency-power coupled discharge. And the overall pulse discharge mode is adopted, reducing the complexity requirements for the radio frequency power supply 13 system. Among them, the gas path connector 1 is used to connect with the gas supply device for the entry of working medium gas; the gas path insulating ceramic 2 and the pulse electrode isolation ceramic 3 are respectively used to fix the pulse ignition negative electrode 8 and the positive electrode; the plasma discharge chamber 4 is used to ionize the working medium gas; the ion collection electrode 5 is used to collect ions; the cathode top 6 is used for the extraction of electrons.

[0032] Furthermore, the transition device 7 is fixed on the gas path connector 1 by arc welding or laser welding. The transition device 7 is mainly used for the fixed connection between the gas path connector 1 and the gas path insulating ceramic 2. Since the materials of the gas path connector 1 and the insulating ceramic are different, arc welding or laser welding is adopted between the transition device 7 and the gas path connector 1, and vacuum brazing is adopted between the transition device 7 and the gas path insulating ceramic 2 to realize the welding and fixing of dissimilar materials.

[0033] Furthermore, the transition device 7 is fixed to the gas path insulating ceramic 2 by vacuum brazing; the pulse ignition negative electrode 8 is fixed between the gas path insulating ceramic 2 and the pulse electrode isolation ceramic 3 by vacuum brazing; the pulse ignition positive electrode 9 is fixed between the pulse electrode isolation ceramic 3 and the plasma discharge chamber 4 by vacuum brazing; the ion collection electrode 5 is fixed above the plasma discharge chamber 4 by vacuum brazing; the cathode top 6 is fixed above the ion collection electrode 5 by vacuum brazing. In the embodiment of the present application, the overall integrated vacuum brazing method is adopted to fix each structure in sequence, achieving the design goals of light weight and integration of the radio frequency inductively coupled cathode, and significantly improving the reliability of the application of the radio frequency inductively coupled cathode.

[0034] Further, the material of the transition device 7 is Kovar alloy; the materials of the gas path insulating ceramic 2, the pulse electrode isolation ceramic 3, the plasma discharge chamber 4, and the cathode top 6 are alumina ceramics; the materials of the pulse ignition negative electrode 8, the pulse ignition positive electrode 9, and the ion collection electrode 5 are tungsten, molybdenum, or graphite.

[0035] Further, a radio frequency coil 10 is fixedly arranged on the outer wall surface inside the plasma discharge chamber 4, and the radio frequency coil 10 is arranged in a spiral shape at a fixed pitch. The radio frequency coil 10 is fixedly arranged in a spiral shape at a fixed pitch on the outer wall surface inside the plasma discharge chamber 4, and is used to form an alternating magnetic field and a high-frequency vortex circumferential electric field, so that the gas entering the inside of the plasma discharge chamber 4 is ionized.

[0036] Further, as Figure 2 shown, it further includes a radio frequency cathode electrical connection device, and the radio frequency cathode electrical connection device includes a pulse power supply 11, an impedance matcher 12, a radio frequency power supply 13, and a collection power supply 14, wherein: the positive electrode of the pulse power supply 11 is connected to the pulse ignition positive electrode 9, and the negative electrode of the pulse power supply 11 is connected to the pulse ignition negative electrode 8; the impedance matcher 12 is electrically connected to both ends of the radio frequency coil 10 respectively; the radio frequency power supply 13 is connected to the impedance matcher 12 through a coaxial radio frequency cable; the negative electrode of the collection power supply 14 is connected to the ion collection electrode 5; the negative electrodes of the pulse power supply 11, the radio frequency power supply 13, and the positive electrode of the collection power supply 14 are all grounded.

[0037] Specifically, the radio frequency cathode electrical connection device is used to supply power to each electrode. Among them, the pulse ignition negative electrode 8, the pulse electrode isolation ceramic 3, the pulse ignition positive electrode 9, and the pulse power supply 11 form a pulse ignition system, as Figure 3 shown, to generate radio frequency inductive coupling ionization primary electrons. During operation, start the radio frequency power supply 13, adjust the impedance matcher 12, when the radio frequency cathode impedance is equal to the impedance of the radio frequency power supply 13, the radio frequency energy feeding is maximized; introduce the working medium gas, start the collection power supply 14; start the pulse power supply 11, monitor the current value of the collection power supply 14, and ignition can be achieved.

[0038] Further, the axial length of the pulse ignition negative electrode 8 is greater than the axial length of the pulse ignition positive electrode 9. The combination of the pulse ignition negative electrode 8 and the pulse ignition positive electrode 9 is closer to the upstream of the plasma discharge chamber 4, so that the primary electrons can move to the plasma discharge chamber 4 under the combined action of the air flow and the radio frequency inductive electromagnetic field, which is helpful for radio frequency inductive coupling ionization.

[0039] Furthermore, the discharge end of the pulse ignition negative electrode 8 is in the shape of an inclined sharp angle; the discharge end of the pulse ignition positive electrode 9 is in the shape of a plane. The shape of the discharge end of the pulse ignition negative electrode 8 is preferably an inclined sharp angle, where the sharp angle end is close to the cathode axis to avoid the generation of redundant substances during the pulse discharge process and reduce the relative electrical insulation between the pulse ignition electrodes; the shape of the discharge end of the pulse ignition positive electrode 9 is preferably a plane shape, which forms a tip discharge structure in combination with the pulse ignition negative electrode 8.

[0040] Furthermore, an electron extraction port is provided at the center of the cathode top 6. An electron extraction small hole is designed at the center of the cathode top 6, and the ion collection electrode 5 is placed at the electron extraction port of the cathode top 6, which can cause the anode spot to form near the electron outlet, contributing to the efficient extraction of electrons.

[0041] Furthermore, as Figure 4 shown, the ion collection electrode 5 is in the shape of an unclosed ring, and its outer diameter is smaller than the inner diameter of the plasma discharge chamber 4. The ion collection electrode 5 is integrally in the shape of an unclosed ring to avoid the formation of a vortex electric field by the radio frequency signal and reduce the radio frequency energy feeding; moreover, the outer diameter of the ion collection electrode 5 is smaller than the inner diameter of the plasma discharge chamber 4, and it is integrally sleeved inside the end of the plasma discharge chamber 4, increasing the ion collection area.

[0042] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An integrated radio frequency inductively coupled cathode, characterized in that: It includes a gas path connector, a gas path insulating ceramic, a pulse electrode isolating ceramic, a plasma discharge chamber, an ion collecting electrode and a cathode top, wherein: A transition device is provided between the gas path joint and the gas path insulating ceramic; A pulse ignition negative electrode is provided between the gas path insulating ceramic and the pulse electrode isolating ceramic; A pulse ignition positive electrode is arranged between the pulse electrode isolation ceramic and the plasma discharge chamber; The ion collecting electrode is buckled above the plasma discharge chamber; The cathode top is fixed above the ion collecting electrode.

2. The one-piece integrated radio frequency inductively coupled cathode according to claim 1, characterized in that: The transition device is fixed on the gas path joint by arc welding or laser welding.

3. The one-piece integrated radio frequency inductively coupled cathode according to claim 2, characterized in that: The transition device and the gas path insulating ceramic are fixed by vacuum brazing; The pulse ignition negative electrode is fixed between the gas path insulating ceramic and the pulse electrode isolating ceramic by vacuum brazing; The pulse ignition positive electrode is fixed between the pulse electrode isolation ceramic and the plasma discharge chamber by vacuum brazing; The ion collecting electrode is fixed on the top of the plasma discharge chamber by vacuum brazing; The cathode top is fixed on the top of the ion collecting electrode by vacuum brazing.

4. The one-piece integrated radio frequency inductively coupled cathode according to claim 3, characterized in that: The material of the transition device is Kovar alloy; the material of the gas path insulating ceramic, the pulse electrode isolation ceramic, the plasma discharge chamber and the cathode top is alumina ceramic; the material of the pulse ignition negative electrode, the pulse ignition positive electrode and the ion collecting electrode is tungsten, molybdenum or graphite.

5. The one-piece integrated radio frequency inductively coupled cathode according to claim 4, characterized in that: A radio frequency coil is fixedly arranged on the outer wall surface inside the plasma discharge chamber, and the radio frequency coil is spirally arranged with a fixed pitch.

6. The one-piece integrated radio frequency inductively coupled cathode according to claim 5, characterized in that: It also includes a radio frequency cathode electrical connection device, which includes a pulse power supply, an impedance matcher, a radio frequency power supply, and a collection power supply, wherein: The positive electrode of the pulse power supply is connected to the pulse ignition positive electrode, and the negative electrode of the pulse power supply is connected to the pulse ignition negative electrode; The impedance matcher is electrically connected to two ends of the radio frequency coil respectively; The radio frequency power supply is connected to the impedance matcher via a coaxial radio frequency cable; The negative electrode of the collection power supply is connected to the ion collection electrode; The negative electrode of the pulse power supply, the negative electrode of the radio frequency power supply and the positive electrode of the collection power supply are all grounded.

7. The one-piece integrated radio frequency inductively coupled cathode according to claim 6, characterized in that: The axial length of the pulse ignition negative electrode is greater than the axial length of the pulse ignition positive electrode.

8. The one-piece integrated radio frequency inductively coupled cathode according to claim 7, characterized in that: The discharge end of the pulse ignition negative electrode is in an oblique sharp angle shape; the discharge end of the pulse ignition positive electrode is in a flat shape.

9. The one-piece integrated radio frequency inductively coupled cathode according to claim 8, characterized in that: An electron outlet is arranged at the center of the cathode top.

10. The one-piece integrated radio frequency inductively coupled cathode according to claim 9, characterized in that: The ion collecting electrode is in the shape of a non-closed circular ring, and its outer diameter is smaller than the inner diameter of the plasma discharge chamber.

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