Heater-free hollow cathode with built-in tungsten filament electrode
By using a hollow cathode structure with built-in tungsten wire electrodes, the problem of miniaturizing heated cathodes is solved. The initial plasma is formed by the thermal emission effect of the built-in tungsten wire electrodes, thus realizing the miniaturization and self-sustaining discharge of the cathode.
Patent Information
- Application Number
- CN202511620132.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-06
- Publication Date
- 2026-02-27
AI Technical Summary
Miniaturization of existing thermal cathodes is difficult, as the large size of the external heating structure makes miniaturization challenging.
The aothermal hollow cathode structure with built-in tungsten filament electrodes optimizes the external heating structure of traditional cathodes by utilizing the thermal emission effect of the built-in tungsten filament electrodes. The built-in tungsten filament electrodes are heated to a high temperature under the action of current to form initial plasma and heat the emitter, thus achieving self-sustaining discharge.
The cathode has been miniaturized, and the cathode start-up process relies on the thermal emission of the internal tungsten filament, which optimizes the traditional external heating structure and meets the miniaturization requirements of the electron source.
Smart Images
Figure CN121583841A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a hollow cathode without a heating sub-cathode with a built-in tungsten wire electrode and belongs to the technical field of aerospace equipment manufacturing. BACKGROUND
[0002] With the wide application of electric thrusters in space missions such as micro-nano satellites, miniaturization of Hall thrusters has become an important development direction, and the cathode as an electron source also faces the development demand of miniaturization.
[0003] A common hot sub-cathode has a heating structure outside the emitter, and the working principle is that the heating structure outside the emitter heats the emitter, and then the emitter surface emits electrons when the temperature reaches the working temperature of the emitter, thereby realizing ignition of the cathode and providing sufficient electrons for the Hall thruster to realize operation of the thruster. Since the heating structure outside the emitter is large, it directly leads to the difficulty of miniaturization of the hot sub-cathode. SUMMARY
[0004] The purpose of the application is to solve the problem of the difficulty of miniaturization of the hot sub-cathode in the prior art, and the application provides a hollow cathode structure without a heating sub-cathode with a built-in tungsten wire electrode to achieve the purpose of miniaturization.
[0005] The purpose of the application is achieved by the following technical scheme:
[0006] A hollow cathode without a heating sub-cathode with a built-in tungsten wire electrode, comprising: a cathode tube, an emitter, a throttling top, a holding electrode, a built-in tungsten wire electrode, a ceramic base, a ceramic insulating layer, a conductive column and a flow channel three;
[0007] The cathode tube is a cylindrical structure, the emitter is arranged on the upper part of the inner wall of the cathode tube and closely adheres to the cathode tube, the top outlet end of the cathode tube is sealingly connected to the throttling top, the throttling top is provided with a flow channel one in the center, the flow channel one is provided through the cathode tube and the emitter cavity, the holding electrode is coaxially sleeved on the outside of the cathode tube, the bottom end of the cathode tube is fixedly connected to the top end surface of the ceramic base, the center of the ceramic base is provided with a flow channel two, the bottom end of the built-in tungsten wire electrode is coaxially fixed in the flow channel two of the ceramic base, and the two poles of the built-in tungsten wire electrode are led out from the flow channel two of the ceramic base, the top end of the built-in tungsten wire electrode is arranged in the emitter cavity and does not contact the surface of the emitter, the bottom end surface of the ceramic base is provided with a through hole one, the through hole one of the ceramic base is in communication with and sealed to the flow channel three, the working medium xenon gas enters the cathode tube from the flow channel three, the bottom end surface of the holding electrode is provided with a ceramic insulating layer, two through holes two are formed in the ceramic insulating layer, and the two conductive columns pass through the two through holes two of the ceramic insulating layer and are fixedly connected to the holding electrode.
[0008] Preferably, a preset interval is formed between the bottom end surface of the throttling top and the top end of the built-in tungsten wire electrode, and the preset interval is 1-3mm.
[0009] Preferably, a gap of 1-1.5 mm exists between the inner top surface of the holding electrode and the top end surface of the throttle top.
[0010] Preferably, a ceramic tube is coaxially sleeved between the holding electrode and the cathode tube.
[0011] Preferably, the built-in tungsten electrode, the cathode tube and the holding electrode are electrically isolated by the ceramic tube.
[0012] Preferably, the ceramic base is made of alumina toughened oxide ceramic material.
[0013] Preferably, one path of the positive electrode of the power supply is connected to the holding electrode, and the other path is connected to a DC-DC voltage reduction module; a low voltage from the DC-DC voltage reduction module is connected to an RC circuit in one path and to one pole of the built-in tungsten electrode in the other path; the DC-DC voltage reduction module, the power supply, the RC circuit, the other pole of the built-in tungsten electrode and the cathode tube are grounded.
[0014] Compared with the prior art, the present application has the following advantages:
[0015] The cathode starting process of the present application relies on the thermal emission of the internal tungsten electrode, and can optimize the external heating structure of the traditional cathode, thereby realizing the miniaturization of the cathode.
[0016] In the present application, the working medium xenon gas enters the cathode tube from the ceramic base; under the action of the current, the built-in tungsten electrode is heated to a high temperature, so that the electrons on the surface of the built-in tungsten electrode obtain high energy; at the same time, the work function of the material is low enough; when the kinetic energy of the electron perpendicular to the surface is greater than the work function of the tungsten electrode, the surface escape work restriction can be overcome, and the electron can escape from the surface of the tungsten electrode in the form of a hot electron; the initial electron is formed in the gas. Since the holding electrode has a high potential, an electric field is formed between the built-in tungsten electrode and the holding electrode; under the action of the electric field, the free electron is accelerated by the electric field, and the electron obtains sufficient kinetic energy and collides with the neutral atom, thereby generating a large number of new electrons and ions, and forming the initial plasma. The initial plasma collides with the emitter to heat the surface emitter to emit electrons, and finally transits to the self-sustaining discharge state. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 It is a plan view of the hollow cathode without a heating element and with a built-in tungsten electrode of the present application.
[0018] Figure 2 It is a plan view of the ceramic base structure of the present application.
[0019] Figure 3 It is a simulation result diagram of the potential distribution of the cathode after discharge stabilization in Example 1.
[0020] Figure 4Figure for the simulation result of the plasma density distribution after the cathode discharge is stabilized in Example 1.
[0021] Figure 5 Figure for the simulation result of the cathode discharge current and the ignition time in Example 1.
[0022] Figure 6 Figure for the schematic diagram of the circuit of the present application.
[0023] In the figure, 1 is a cathode tube, 2 is an emitter, 3 is a throttle top, 4 is a contact pole, 5 is an embedded tungsten wire electrode, 6 is a ceramic base, 7 is an insulating layer, 8 is a conductive column, 9 is a flow channel three, and 10 is a ceramic tube. DETAILED DESCRIPTION
[0024] The present application will be further described in detail below in combination with the accompanying drawings: The present embodiment is implemented on the premise of the technical solution of the present application, and a detailed implementation manner is given, but the protection scope of the present application is not limited to the following examples.
[0025] As shown in Figure 1 and Figure 2 , the non-thermal sub hollow cathode with embedded tungsten wire electrode involved in the present embodiment comprises: a cathode tube 1, an emitter 2, a throttle top 3, a contact pole 4, an embedded tungsten wire electrode 5, a ceramic base 6, an insulating layer 7, a conductive column 8, a flow channel three 9, and a ceramic tube 10.
[0026] The cathode tube 1 is a cylindrical structure, the emitter 2 is arranged on the upper part of the inner wall of the cathode tube 1 and closely adheres, the top outlet end of the cathode tube 1 is sealingly connected with the throttle top 3, the center of the throttle top 3 is provided with a flow channel one, the flow channel one is provided through the cavity of the cathode tube 1 and the emitter 2, the holding electrode 4 is coaxially sleeved on the outside of the cathode tube 1, the bottom end of the cathode tube 1 is fixedly connected with the top end surface of the ceramic base 6, the center of the ceramic base 6 is provided with a flow channel two, the bottom end of the built-in tungsten filament electrode 5 is coaxially fixed in the flow channel two of the ceramic base 6, the built-in tungsten filament electrode 5 and the ceramic base 6 are connected by welding, and the two poles of the built-in tungsten filament electrode 5 are led out from the flow channel two of the ceramic base 6 to facilitate wiring, the top end of the built-in tungsten filament electrode 5 is arranged in the cavity of the emitter 2 and does not contact the surface of the emitter 2, the bottom end surface of the ceramic base 6 is provided with a through hole one, the through hole one of the ceramic base 6 is communicated with the flow channel three 9 and is sealed, the working medium xenon gas enters the cathode tube 1 from the flow channel three 9 through the through hole one of the ceramic base 6, the bottom end surface of the holding electrode 4 is provided with a ceramic insulation layer, two through holes two are formed in the ceramic insulation layer 7, and two conductive columns 8 are fixedly connected with the holding electrode 4 by penetrating the two through holes two of the ceramic insulation layer 7. The ceramic insulation layer 7 realizes electrical isolation of the holding electrode 4 and other components. A preset interval is formed between the bottom end surface of the throttle top 3 and the top end (tip end) of the built-in tungsten filament electrode 5, and the preset interval is 1-3 mm. There is a gap of 1-1.5 mm between the inner top surface of the holding electrode 4 and the top end surface of the throttle top 3 and the top end of the cathode tube 1.
[0027] The electrode of the built-in tungsten filament electrode 5 is made of tungsten material, so that the electrode can meet the requirements of high-temperature stability, corrosion resistance and good electrical conductivity.
[0028] The ceramic base 6 is made of alumina toughened oxide ceramic material, can resist high-temperature plasma environment, has good thermal expansion coefficient matching and good thermal shock resistance performance, and a sleeve is additionally arranged at the connection between the built-in tungsten filament electrode and the ceramic base, the sleeve is made of niobium-tungsten alloy bellows to compensate thermal expansion, so that the dynamic sealing performance can be maintained at high temperature, and the interface peeling risk caused by electrode-ceramic thermal mismatch can be eliminated.
[0029] There is a gap of 1-1.5 mm between the holding electrode 4 and the top of the throttle top 3. The holding electrode 4 is installed at a position 1-1.5 mm above the cathode tube 1, the ceramic tube 10 is coaxially sleeved between the holding electrode 4 and the cathode tube 1, so that the holding electrode 4 and the cathode tube 1 are electrically isolated. In addition, the built-in tungsten filament electrode 5, the cathode tube 1 and the holding electrode 4 are electrically isolated through the ceramic tube 10. A preset interval is formed between the bottom end of the throttle top 3 and the tip end of the built-in tungsten filament electrode 5, and the preset interval is 1-3 mm, so as to form initial electrons in the cathode.
[0030] The assembly process of the hollow cathode without heat sub of the application with the built-in tungsten filament electrode follows the principle of precise positioning: the assembly steps are as follows:
[0031] First, the built-in tungsten wire electrode 5 is fixed coaxially in the center channel of the high-performance ceramic base 6 by high-energy beam welding; then the barium-tungsten emitter 2 is precisely assembled into the inner cavity of the cathode tube 1, and the throttle top 3 is sealed at the outlet end of the cathode tube 1 by a high-temperature connection process, and a preset interval is formed between the bottom end of the throttle top 3 and the tip of the built-in tungsten wire electrode 5, and the preset interval is 1-3 mm; a gradually expanding conical flow channel one is provided in the center of the throttle top 3 and is arranged through the cavities of the cathode tube 1 and the emitter 2; finally, the contact electrode 4 is coaxially sleeved outside the cathode tube 1, and a ceramic tube 10 is coaxially sleeved between the contact electrode 4 and the cathode tube 1, and the potential isolation of the contact electrode 4 and the cathode tube 1 is realized through the insulating structure ceramic tube 10, and the contact electrode 4 is installed at a distance of 1-2 mm from the outlet of the throttle top 3.
[0032] When the cathode works, the working medium xenon gas enters the cathode tube 1 through the through hole one of the ceramic base 6 from the flow channel three 9, the built-in tungsten wire electrode 5 inside is heated to a high temperature under the action of current, so that the electrons on the surface of the built-in tungsten wire electrode 5 obtain high energy; at the same time, because the work function of the tungsten wire is low enough, when the kinetic energy of the electron perpendicular to the surface is greater than the work function of the tungsten wire, the surface escape work restriction can be overcome, and the electron is separated from the surface of the tungsten wire in the form of a hot electron, and an initial electron is formed in the gas. Because the contact electrode 4 has a high potential, an electric field is formed between the built-in tungsten wire electrode 5 and the contact electrode 4, and the initial free electron is accelerated under the action of the electric field, and the electron obtains sufficient kinetic energy and collides with a neutral atom, thereby generating a large number of new electrons and ions, and thus forming an initial plasma. This part of the initial plasma collides with the emitter 2 to heat the surface of the emitter 2 and promote electron emission, and finally transits to a self-sustaining discharge state. Compared with the traditional cathode, the starting process of the cathode of the application can optimize the heating structure of the traditional cathode under the action of the tungsten wire, so as to realize the miniaturization of the cathode.
[0033] As shown in Figure 6 When the cathode ignites, the positive pole of the power supply is connected to the contact electrode 4 in one way, and the other way is connected to the DC-DC voltage reduction module; the low voltage from the DC-DC voltage reduction module is connected to the RC circuit in one way to realize the functions of time delay and filtering, and is connected to one pole of the built-in tungsten wire electrode 5 in the other way; the DC-DC voltage reduction module, the power supply, the RC circuit, the other pole of the built-in tungsten wire electrode 5 and the cathode tube 1 are grounded.
[0034] The following is an example to further illustrate the discharge effect of the heat-free hollow cathode with a built-in tungsten wire electrode.
[0035] Example 1
[0036] The simulation of the discharge process is carried out with a typical small-size cathode structure. The simulation conditions are as follows: the inner diameter of the emitter 2 is 5 mm, the length of the emitter 2 is 6.5 mm, the throttle top 3 is a tungsten top, the aperture of the tungsten top is 2 mm, the anode potential is 100 V, and the total flow rate of the neutral gas is 3.5 sccm. In the simulation, the built-in tungsten wire electrode 5 is simplified as a boundary condition, which is located at the position of the symmetry axis 3 mm away from the bottom of the cathode, and the emission current of the tungsten wire is 0.1 mA. The variation of the cathode current is shown in Figure 5 The results shown in Figure 5 indicate that the ignition of the cathode can be effectively realized by using the built-in tungsten wire electrode 5. Figure 3 and Figure 4 are the spatial distribution diagrams of the potential and the plasma density, respectively. The results shown in Figure 3 and Figure 4 indicate that the peak value of the plasma density can reach 10 20 / m 3 , which meets the requirements of the cathode. It can be seen that the ignition of the cathode can be effectively realized by using the built-in tungsten wire electrode 5.
[0037] The above description is only the preferred embodiments of the present application, which are different implementations based on the overall concept of the present application. The protection scope of the present application is not limited to this, and any changes or replacements within the technical scope disclosed by the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims
1. A heatless hollow cathode with an internal tungsten wire electrode, characterized in that, include: Cathode tube (1), emitter (2), throttling top (3), contact electrode (4), built-in tungsten wire electrode (5), ceramic base (6), ceramic insulating layer (7), conductive pillar (8) and flow channel three (9); The cathode tube (1) is a cylindrical structure. The emitter (2) is located on the upper part of the inner wall of the cathode tube (1) and fits tightly. The top outlet end of the cathode tube (1) is sealed and connected to the throttling top (3). The center of the throttling top (3) has a flow channel one, which is connected to the cavity of the cathode tube (1) and the emitter (2). The contact electrode (4) is coaxially fitted to the outside of the cathode tube (1). The bottom end of the cathode tube (1) is fixedly connected to the top surface of the ceramic base (6). The center of the ceramic base (6) has a flow channel two. The bottom end of the built-in tungsten wire electrode (5) is coaxially fixed in the flow channel two of the ceramic base (6), and the built-in tungsten wire electrode (5) is placed inside the flow channel two of the ceramic base (6). The two poles of the tungsten wire electrode (5) are led out from the second flow channel of the ceramic base (6). The top of the built-in tungsten wire electrode (5) is set in the cavity of the emitter (2) and does not contact the surface of the emitter (2). The bottom end face of the ceramic base (6) is provided with a through hole one. The through hole one of the ceramic base (6) is connected to the third flow channel (9) and sealed. The working propellant xenon gas enters the cathode tube (1) from the third flow channel (9). The bottom end face of the contact electrode (4) is provided with a ceramic insulating layer (7). Two through holes two are opened on the ceramic insulating layer (7). Two conductive pillars (8) pass through the two through holes two of the ceramic insulating layer (7) and are fixedly connected to the contact electrode (4).
2. The insulated hollow cathode with a built-in tungsten wire electrode according to claim 1, characterized in that, A preset distance of 1-3 mm is formed between the bottom surface of the throttling top (3) and the top surface of the built-in tungsten wire electrode (5).
3. The insulated hollow cathode with an internal tungsten wire electrode according to claim 1, characterized in that, There is a 1-1.5mm gap between the inner top surface of the contact electrode (4) and the top surface of the throttling top (3).
4. The insulated hollow cathode with a built-in tungsten wire electrode according to claim 1, characterized in that, A ceramic tube (10) is coaxially fitted between the contact electrode (4) and the cathode tube (1).
5. A heatless hollow cathode with an internal tungsten wire electrode according to claim 4, characterized in that, The built-in tungsten wire electrode (5), cathode tube (1) and contact electrode (4) are electrically isolated through a ceramic tube (10).
6. A heatless hollow cathode with an internal tungsten wire electrode according to claim 1, characterized in that, The ceramic base (6) is made of alumina-toughened oxide ceramic material.
7. A heatless hollow cathode with an internal tungsten wire electrode according to claim 1, characterized in that, One path of the positive terminal of the power supply is connected to the contact electrode (4), and the other path is connected to the DC-DC step-down module. One path of the low voltage from the DC-DC step-down module is connected to the RC circuit, and the other path is connected to one pole of the built-in tungsten wire electrode (5). The DC-DC step-down module, the power supply, the RC circuit, the other pole of the built-in tungsten wire electrode (5) and the cathode tube (1) are all grounded.