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CN118231201B - Electromagnetic induction heating starting self-sustaining compact hollow cathode source - Google Patents

Electromagnetic induction heating starting self-sustaining compact hollow cathode source Download PDF

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Publication number
CN118231201B
CN118231201B CN202410653090.8A CN202410653090A CN118231201B CN 118231201 B CN118231201 B CN 118231201B CN 202410653090 A CN202410653090 A CN 202410653090A CN 118231201 B CN118231201 B CN 118231201B
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graphite
induction heating
cavity
cathode
water
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CN118231201A (en
Inventor
胡广海
王彦博
徐国盛
王亮
陈冉
单峦峦
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Hefei Institutes of Physical Science of CAS
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Hefei Institutes of Physical Science of CAS
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02Main electrodes
    • H01J1/13Solid thermionic cathodes
    • H01J1/20Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02Main electrodes
    • H01J1/13Solid thermionic cathodes
    • H01J1/14Solid thermionic cathodes characterised by the material
    • H01J1/148Solid thermionic cathodes characterised by the material with compounds having metallic conductive properties, e.g. lanthanum boride, as an emissive material
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02Details
    • H01J37/04Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/08Ion sources; Ion guns
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02Details
    • H01J37/16Vessels; Containers
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00Heating by electric, magnetic or electromagnetic fields
    • H05B6/02Induction heating
    • H05B6/10Induction heating apparatus, other than furnaces, for specific applications

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Plasma Technology (AREA)

Abstract

The invention discloses a compact hollow cathode source capable of self-sustaining operation started by electromagnetic induction heating, which belongs to the technical field of application and electric propulsion of plasma sources and comprises the following structures: the high-frequency induction heating coil can rapidly heat a large-size graphite cavity and a lanthanum hexaboride cathode tube, and can apply an external steady-state magnetic field under the self-sustaining heating working condition; a water-cooled cathode electrode is arranged in the center of the insulating flange and is connected with a graphite connecting pipe, a graphite heating cavity and a lanthanum hexaboride cathode tube; the outer wall of the graphite heating cavity is fixed with the boron nitride ceramic cavity through threads, a graphite anode is arranged at the front end of the boron nitride ceramic cavity, and the graphite anode is connected with a water-cooled anode electrode through a graphite rod. The plasma source of the invention can rapidly heat the lanthanum hexaboride cathode tube to extremely high temperature, and maintains self-sustaining operation by utilizing discharge power, and has the advantages of light weight, strong emission capability, high working temperature, stability, reliability, compact structure and the like, and can be used as an ultra-high density plasma source and a space propeller.

Description

Electromagnetic induction heating starting self-sustaining compact hollow cathode source
Technical Field
The invention belongs to the technical field of application of plasma sources and electric propulsion, and particularly relates to a compact hollow cathode source capable of self-sustaining operation started by electromagnetic induction heating.
Background
With the development of magnetically confined fusion devices, the first wall material facing the plasma faces a great challenge, being a major thermal load problem in addition to plasma sputtering. For example, the plasma density near the divertor is extremely high, the thermal load reaches 10 MW/m 2, and the divertor plasma parameters are simulated under the laboratory conditions, so that the problems of the thermal load and the service life of the first wall material are solved. The discharge parameters of the developed novel high-density hollow cathode plasma source can reach 10 19-1022 m-3, the electron temperature is less than 10 eV, the generated heat load can reach 20-10 MW/m 2, and various parameters are similar to those of the divertor plasma. The interaction between the plasma of the divertor and the first wall is simulated under the laboratory condition, so that the generated problems can be better solved, the testing cost is lower, and a feasible solution is provided for the practical problems encountered by the magnetic confinement fusion device.
The Hall propeller is a middle-impulse aerospace propulsion device, is considered to be the main technical direction in the electric propulsion technology of a spacecraft, and has very high propulsion efficiency (the highest efficiency at present can reach about 75%). Compared with the traditional chemical energy rocket propeller, the Hall propeller can generate the total thrust with a gap of several orders of magnitude, but has larger specific impulse, and is more suitable for long-time space missions and spacecraft position adjustment. Compared with another mainstream electric propulsion technology, the grid ion propeller and the Hall propeller can operate under a quasi-neutral plasma working condition so as to avoid space charge saturation effect, thereby having higher thrust density and larger thrust-weight ratio. Finally, the Hall thruster can also use more kinds of propellants, and inert gases xenon Xe and krypton Kr are common, and even gaseous metal elements such as magnesium Mg, zinc Zn, iodine I and the like can be used, and the principle of the propellant is generally that the propellant has higher atomic weight and lower ionization potential so as to achieve the best propelling effect.
The existing mainstream compact Hall thruster has the defect that the heating scheme of the cathode source has an optimization space. The problems of low heating efficiency and easy degradation of insulating materials under the working condition of high temperature and long pulse are mainly embodied. For example, the main flow compact Hall propeller uses armored heating wires, so that the problems of lower maximum passing current, continuous heating and the like exist, and the thrust is limited. To further enhance performance, an external magnetic field needs to be applied through a coil or permanent magnet.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a compact hollow cathode source which is started by electromagnetic induction heating and can work in a self-sustaining mode, the cathode can be quickly heated to extremely high temperature by high-frequency induction heating, and the self-sustaining mode of the cathode is maintained by using discharge power. When the high-frequency heating power supply is turned off, the inductance coil applies steady-state current to generate an externally applied magnetic field, so that the emission capability of the lanthanum hexaboride cathode tube is further improved, the lanthanum hexaboride cathode tube is further heated by the increase of the emission current, and positive feedback is formed by the increase of the emission current and the increase of the temperature of the lanthanum hexaboride cathode tube. The newly developed electromagnetic induction heating starting self-sustained working compact hollow cathode source has the advantages of high emission capability, quick starting, light weight, compact structure, low cost, long-time stable working and perfect compatibility with large current and long service life.
In order to achieve the above purpose, the invention adopts the following technical scheme:
A compact hollow cathode source capable of self-sustaining operation is started by electromagnetic induction heating, and comprises a lanthanum hexaboride cathode tube, a graphite gasket, a graphite heating cavity, a boron nitride ceramic cavity, a graphite anode, a high-frequency induction heating coil, a graphite connecting pipe, an epoxy resin threaded pipe, a water-cooled cathode electrode, an anode graphite rod connecting bolt, a graphite connecting rod, a water-cooled anode electrode, an insulating flange and an air inlet hole. The lanthanum hexaboride cathode tube and the graphite gasket form a cathode inner assembly, the cathode inner assembly is integrally nested into a graphite heating cavity, the periphery of the graphite heating cavity is fixed and kept coaxial with a boron nitride ceramic cavity through threads, and the graphite anode is mounted in a fitting way and kept coaxial with a concave cavity structure at the front end of the boron nitride ceramic cavity; the high-frequency induction heating coil is coaxially sleeved on the periphery of the boron nitride ceramic cavity, and the boron nitride ceramic cavity is not contacted with the high-frequency induction heating coil; the rear end of the graphite connecting pipe is coaxially connected with the front end of the hollow double-layer water-cooled cathode electrode through threads, and the water-cooled cathode electrode penetrates through the epoxy resin threaded pipe to be fixed on the insulating flange and is kept coaxial; the front end of the graphite connecting pipe is coaxially connected with the graphite heating cavity through threads in the graphite heating cavity, and the end part of the graphite connecting pipe is attached to the graphite gasket; the rear end screw hole of the graphite connecting rod and the front end screw thread of the water-cooled anode electrode form a fixed structure, and the front end of the graphite connecting rod is fixed by an anode graphite rod connecting bolt through an extending structure of the graphite anode; the water-cooled anode electrode is fixed on a screw hole of the insulating flange through external threads, and two ends of the high-frequency induction heating coil respectively penetrate through the open holes of the insulating flange to be fixed; discharge gas is injected from the air inlet hole, enters the lanthanum hexaboride cathode tube after passing through the hollow tube structure in the water-cooled cathode electrode and the graphite connecting tube, is ionized and becomes plasma, and is sprayed out from the middle hole of the graphite anode.
Further, the insulating flange may be an epoxy flange. The epoxy resin has the advantages of high mechanical strength, corrosion resistance and insulation.
Further, the lanthanum hexaboride cathode tube is a hollow cathode tube, and the material is lanthanum hexaboride (LaB 6) with the melting point as high as 2715 ℃; the inner ring of the graphite gasket is a hollow tube, the outer ring is of a gear-shaped structure, and the graphite gasket is attached to the lanthanum hexaboride cathode tube for installation, so that heat conduction with a graphite heat conduction cavity can be effectively reduced. The lanthanum hexaboride cathode tube and the graphite gasket are coaxially attached and installed.
Further, the lanthanum hexaboride cathode tube and the graphite gasket are coaxially nested with a graphite heating cavity, and the graphite heating cavity is made of high-hardness graphite with the wall thickness of 2mm and is used for conducting electricity and heating the lanthanum hexaboride cathode tube. The graphite has extremely high melting point (3660 ℃), and is suitable for long-time working at high temperature. The graphite heating cavity is of a three-ring structure, the inner ring is a hollow pipe, the middle ring is used for limiting and fixing, and threads are arranged at the outer part of the rear end of the middle ring.
Further, the Boron Nitride (BN) ceramic cavity is coaxially fixed outside the graphite heating cavity through threads, and the boron nitride ceramic cavity and the graphite heating cavity are not contacted except for a rear end thread section. The boron nitride ceramic cavity has the functions of insulation, arc discharge prevention, support, heat shielding and reflection, and has good thermal stability and durability. The boron nitride ceramic cavity is of a double-ring structure, and the front end of the boron nitride ceramic cavity is of a concave cavity structure.
Further, the concave cavity structure of the boron nitride ceramic cavity is fitted with a graphite anode, and the graphite anode and the concave cavity structure are fitted and coaxially installed. The graphite anode extends radially out of the elongated structure and is provided with openings.
Further, the outermost periphery of the boron nitride ceramic cavity is sleeved with a water-cooled high-frequency induction heating coil, and the high-frequency induction heating coil is coaxial with but not attached to the boron nitride ceramic cavity. The high-frequency induction heating coil is formed by winding copper pipes, cooling water is filled in the high-frequency induction heating coil, and the high-frequency induction heating coil is connected with a high-frequency (80 kHz) high-current (> 50A) power supply, so that the high-frequency induction heating coil has the advantages of quick starting, long service life, reusability, high heating temperature and the like compared with an armored heating wire, and can heat the lanthanum hexaboride cathode tube to more than 1750 ℃ within 1-5 minutes. The lanthanum hexaboride cathode tube can be turned off for induction heating after being heated to more than 1750 ℃, and self-sustaining heating is realized by utilizing plasma current. The high-frequency induction heating coil can apply steady-state current to generate an external steady-state magnetic field during self-sustaining heating, so that the electron emission capability and the particle flow density of the lanthanum hexaboride cathode are further improved.
Further, the rear end of the graphite heating cavity is provided with a graphite connecting pipe coaxially, and the graphite connecting pipe is connected with the inner cavity of the graphite heating cavity through front end threads and is attached to the graphite gasket. The graphite has the characteristics of high melting point and low density, and avoids sintering sputtering phenomenon caused by the condition that different materials are mutually contacted under the high-temperature long-pulse working condition. The graphite connecting pipe is of a hollow structure, and the front end of the graphite connecting pipe is provided with threads connected with the graphite heating cavity.
Further, the rear end of the graphite connecting pipe is connected with the water-cooled cathode electrode, and the water-cooled cathode electrode is connected with the graphite connecting pipe through threads so as to achieve better heat conduction and cooling effects and avoid heat transfer to the insulating flange. When the discharge gas flows through the graphite connecting pipe, the temperature can be greatly increased, the ionization energy of the high-temperature gas is reduced, and the discharge gas is easier to ionize.
Further, the graphite connecting rod is attached to the extending structure of the graphite anode, and the graphite anode and the graphite connecting rod are fixed through the anode graphite rod connecting bolt.
Further, the rear end of the graphite connecting rod is connected with a water-cooled anode electrode, and the water-cooled anode electrode is connected with the graphite connecting rod through threads so as to achieve better heat conduction and cooling effects.
Further, the water-cooled cathode electrode and the water-cooled anode electrode are respectively provided with a main water inlet hole, a main water outlet hole and an internal cooling water cavity. The water-cooling cathode electrode and the water-cooling anode electrode can effectively avoid melting of all parts at high temperature, and ensure the vacuum degree and equipment safety of the device under the working condition of high temperature long pulse.
Further, the lanthanum hexaboride cathode tube is fixed and supported by an insulating flange. The water-cooled cathode electrode is coaxially arranged to an opening in the center of the insulating flange through an epoxy resin threaded pipe during installation; the high-frequency induction heating coil penetrates through openings in the three-point and nine-point directions in the center of the insulating flange and is fixed; the water-cooled anode electrode connected with the anode part passes through the six-point openings of the insulating flange and is fixed.
Further, the discharge gas is injected from the hollow tube structure inside the water-cooled cathode electrode, enters the inside of the lanthanum hexaboride cathode tube through the graphite connecting tube, is ionized and then is sprayed out from the middle hole of the graphite anode, and the discharge gas can be non-oxidizing gas such as He, ar, xe, kr, N 2 and the like.
Furthermore, the high-frequency induction heating coil can rapidly heat the graphite heating cavity to extremely high temperature, and can supply direct current when heating is not needed, so that a lanthanum hexaboride cathode tube coaxial magnetic field is provided.
The invention applies high-frequency current signals by using the high-frequency induction heating coil, can rapidly heat the graphite heating cavity to extremely high temperature and conduct the graphite heating cavity to the lanthanum hexaboride cathode tube to enable the graphite heating cavity to reach the working temperature, and cooling water can be communicated into the high-frequency induction heating coil, so that the system safety is ensured.
Further, the boron nitride ceramic cavity is located between the graphite heating cavity and the high-frequency induction heating coil, arc discharge between high-current work of the high-frequency induction heating coil and the graphite heating cavity can be avoided, an insulating effect is achieved, meanwhile, only the boron nitride ceramic cavity and the graphite heating cavity are in contact at a threaded connection part, a heat shielding effect can be achieved, and heating efficiency is improved. The front end of the boron nitride ceramic cavity is provided with a concave cavity structure for installing a graphite anode, so that the boron nitride ceramic cavity between the cathode and the anode plays an insulating role, ensures that the cathode and the anode are coaxial and simultaneously protects the cathode and the anode, and prevents breakdown arcing between the cathode and the anode.
Further, the lanthanum hexaboride cathode tube is positioned in the graphite heating cavity, and good electrical contact is maintained, so that after the temperature of the graphite cavity is raised, heat can be quickly conducted to the lanthanum hexaboride cathode tube, and the heating speed is far higher than that of heat radiation.
Furthermore, the graphite heating cavity heats the lanthanum hexaboride cathode tube, and meanwhile, the lanthanum hexaboride cathode tube is a conductor, and is connected with the water-cooled cathode electrode through a hollow graphite connecting pipe in threaded connection, so that good electric contact and coaxiality of all parts are ensured.
Further, the water-cooled cathode electrode is of a hollow structure, the center of the water-cooled cathode electrode is provided with an air inlet pipe, discharge gas is injected from the air inlet hole, and enters a cathode discharge area to be ionized after passing through the water-cooled cathode electrode and the hollow graphite connecting pipe, so that an additional air inlet pipe is not needed. The discharge gas is slowly heated during the injection flow, reducing ionization energy, so that the gas is more easily ionized.
All parts of the invention are integrated on the insulating flange, the insulating flange with high mechanical strength can well pass high-frequency heating current, and the flange temperature is not too high and the energy loss is not caused. The invention adopts graphite, boron nitride, epoxy resin and the like with high temperature resistance and low density, and greatly reduces the quality of the material.
The invention can generate high density plasma, can be used for various plasma physical researches, such as simulating plasma discharge of a divertor, interaction of plasma and a wall, and the like, and can also be used for space propulsion technology, and no additional heating is needed under the condition because the highest discharge current is more than 300A, so that the invention can stably work for a long time and has very high propulsion force.
Advantageous effects
(1) The invention adopts the high-frequency induction heating coil to realize the characteristic of heating the cathode to extremely high temperature in a short time, the cathode can be heated to more than 1750 ℃ within 1-5 minutes, and the maximum current emissivity reaches 80A/cm 2. When the cathode is heated to the required temperature (> 1750 ℃), the inductive heating can be turned off, and the self-sustaining heating of the lanthanum hexaboride cathode tube is realized by utilizing the plasma current. The high-frequency induction heating coil can apply steady-state current to generate steady-state magnetic field coaxial with the cathode during self-sustaining heating, so that the electron emission capability of the lanthanum hexaboride cathode tube is further improved.
(2) The cathode made of lanthanum hexaboride material and the boron nitride ceramic cavity have long service life, and the vacuum degree and impurity pollution tolerance of the invention are high because no chemical reaction occurs. Because the diffusion property of boron in metal makes it unfavorable for direct contact with metal material, graphite material is used in the present invention to make electric conduction, isolation, heat conduction and support.
(3) According to the invention, through simplifying the design, welding operation is avoided in the assembly process, so that the risk of welding seam off-welding damage at high temperature is avoided. The device has the advantages of simple assembly, long durability and high design freedom.
(4) The invention has compact integral structure, convenient assembly, good durability and excellent performance. Compared with the prior art, the developed induction heating method has the advantages of high heating temperature and short starting time, and can generate ultra-high density plasma on the premise of not increasing the structural volume and the mass because most of used light materials such as boron nitride, graphite, epoxy resin and the like. Can be used as an ultra-high density plasma source and a space propeller in the fields of physical research and engineering.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic view of a compact hollow cathode source capable of self-sustaining operation for electromagnetic induction heating start in accordance with the present invention;
FIG. 2 is a cross-sectional view of a self-sustaining hollow cathode source for electromagnetic induction heating start-up in accordance with the present invention;
Fig. 3 is an exploded view of a compact hollow cathode source of the present invention that is self-sustaining operation activated by electromagnetic induction heating.
The reference numerals in the drawings mean: 1. lanthanum hexaboride cathode tube; 2. a graphite gasket; 3. a graphite heating chamber; 4. a boron nitride ceramic cavity; 5. a graphite anode; 6. a high-frequency induction heating coil; 7. a graphite connecting pipe; 8. an epoxy threaded tube; 9. a water-cooled cathode electrode; 10. an anode graphite rod connecting bolt; 11. a graphite connecting rod; 12. a water-cooled anode electrode; 13. an insulating flange; 14. an air inlet hole.
Detailed Description
In order to enable those skilled in the art to better understand the present invention, the following description will make clear and complete descriptions of the technical solutions according to the embodiments of the present invention with reference to the accompanying drawings. It will be apparent that the embodiments described below are only some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by a person skilled in the art without any inventive effort, based on the embodiments described in the invention are within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
The following detailed description of specific embodiments of the invention refers to the accompanying drawings:
As shown in fig. 1-3, the electromagnetic induction heating starting self-sustained working compact hollow cathode source comprises a lanthanum hexaboride cathode tube 1, a graphite gasket 2, a graphite heating cavity 3, a boron nitride ceramic cavity 4, a graphite anode 5, a high-frequency induction heating coil 6, a graphite connecting tube 7, an epoxy resin threaded tube 8, a water-cooled cathode electrode 9, an anode graphite rod connecting bolt 10, a graphite connecting rod 11, a water-cooled anode electrode 12, an insulating flange 13 and an air inlet hole 14.
The rear end of the lanthanum hexaboride cathode tube 1 is attached to the graphite gasket 2 to form a cathode inner assembly, the cathode inner assembly is in threaded connection and compaction with the interior of the graphite heating cavity 3 through the graphite connecting pipe 7, the cathode inner assembly is integrally nested into the graphite heating cavity 3, the periphery of the rear end of the graphite heating cavity 3 is fixed with the boron nitride ceramic cavity 4 through threads, and the graphite anode 5 is attached to the concave cavity structure of the front end of the boron nitride ceramic cavity 4. The high-frequency induction heating coil 6 is coaxially sleeved on the periphery of the boron nitride ceramic cavity 4 and is fixed through an insulating flange 13. The radius of the high-frequency induction heating coil 6 is larger than that of the boron nitride ceramic cavity 4, and the high-frequency induction heating coil 6 is not contacted with the boron nitride ceramic cavity 4, and is connected with a high-frequency heating power supply (not shown in the figure).
Preferably, the graphite gasket 2 has a gear-like structure, so as to reduce the contact area with the graphite heating cavity 3, thereby reducing the heat transfer to the graphite gasket 2 under the ultra-high temperature long pulse working condition.
The main bodies of the lanthanum hexaboride cathode tube 1, the graphite heating cavity 3, the boron nitride ceramic cavity 4 and the graphite anode 5 are hollow annular structures. The rear end of the main body of the graphite anode 5 with the two-pole step shape is of an annular structure, the front end of the graphite anode 5 is nested into the boron nitride ceramic cavity 4, the front end of the graphite anode 5 is of a funnel-shaped structure, the front end of the graphite anode is of an extension structure, and the extension structure is of an open pore structure which extends out radially.
The boron nitride ceramic cavity 4 serves as an insulating part between the cathode and the anode, and plays roles of preventing breakdown and arc discharge and supporting the anode. The boron nitride ceramic chamber 4 also plays a role in preventing arcing between the graphite heating chamber 3 and the high-frequency induction heating coil 6 during heating. The boron nitride ceramic cavity 4 and the graphite heating cavity 3 are not contacted except the thread fixing part, so that the heat shielding and reflecting effects are achieved, and the heating efficiency of the graphite heating cavity 3 and the lanthanum hexaboride cathode tube 1 can be improved.
The lanthanum hexaboride cathode tube 1 can be heated to more than 1750 ℃ and then is turned off for induction heating, at the moment, a large amount of electrons are emitted by the lanthanum hexaboride cathode tube 1 and are subjected to ion bombardment, and the emitted electron current and the graphite anode 5 form an electric loop, so that the effect of heating the lanthanum hexaboride cathode tube 1 is achieved, and self-sustaining heating is realized.
The rear end of the graphite connecting pipe 7 is coaxial with the water-cooled cathode electrode 9 and is tightly connected with the water-cooled cathode electrode 9 through threads, and then the water-cooled cathode electrode 9 passes through the epoxy resin threaded pipe 8 to be fixed on the insulating flange 13. The graphite connecting pipe 7 and the graphite heating cavity 3 are coaxially connected through threads inside the graphite heating cavity 3, and the front end of the graphite connecting pipe 7 is attached to the graphite gasket 2.
The inner cavity of the water-cooled cathode electrode 9 is provided with an annular water-cooling groove and a water inlet and outlet hole which are respectively positioned at two radial sides, and a cavity is axially formed for injecting and passing discharge gas. The axis of the graphite connecting pipe 7 is also provided with a cavity for passing the discharge gas.
The discharge gas is a non-oxidizing gas such as He, ar, xe, kr, N 2, or a mixture of the above discharge gases. The discharge gas does not need to be additionally provided with an air inlet pipe, but is injected from an air inlet 14 and enters the cathode region through the water-cooled cathode electrode 9 and the cavity in the axial direction of the graphite connecting pipe 7, and preferably, the discharge gas can be preheated in the process so as to reduce ionization energy, so that the discharge gas is ionized more easily in the cathode region.
The rear end of the graphite connecting rod 11 and the water-cooled anode electrode 12 are fixed through threads. The front end of the graphite connecting rod 11 is fixed by an anode graphite rod connecting bolt 10 through the extension structure of the graphite anode 5.
The elongated structure of the graphite anode 5 is provided with holes, and the anode graphite rod connecting bolts 10, the connecting holes on two sides of the graphite connecting rod 11 and the water-cooled anode electrode 12 are coaxial.
The inner cavity of the water-cooled anode electrode 12 is provided with a water-cooled cavity and a water inlet and outlet hole, which are respectively positioned in the axial direction and the radial direction.
The insulating flange 13 may be an epoxy resin flange, and plays roles in supporting and fixing the components and insulation, wherein the water-cooled cathode electrode 9 is fixed on the insulating flange 13 through the central opening of the insulating flange 13 by the epoxy resin threaded pipe 8, the water-cooled anode electrode 12 is fixed on the insulating flange 13 through the opening of the insulating flange 13 in the six-point direction, and two ends of the high-frequency induction heating coil 6 respectively pass through the openings of the insulating flange 13 in the three-point and nine-point directions to be fixed.
The assembly does not need welding, and ensures the stability and reliability under the working condition of high temperature long pulse.
The working process of the invention is as follows: discharge gas such as helium is injected from an air inlet hole 14, is injected into the lanthanum hexaboride cathode tube 1 through a water-cooled cathode electrode 9 and a cavity of the axis of a graphite connecting pipe 7, a high-frequency induction heating coil 6 is connected with a high-frequency heating power supply, the graphite heating cavity 3 and the lanthanum hexaboride cathode tube 1 are rapidly heated within 5 minutes, the lanthanum hexaboride cathode tube 1 is heated to more than 1750 ℃, the power supply is switched to be direct current, a self-sustaining heating mode is started through plasma current, and the maximum current emissivity of the lanthanum hexaboride cathode tube 1 reaches 80A/cm 2. Electrons emitted from the lanthanum hexaboride cathode tube 1 collide with the discharge gas sufficiently to ionize the discharge gas, and are ejected from the graphite anode 5 at a high speed. The water-cooled cathode electrode 9 and the water-cooled anode electrode 12 were continuously cooled by 3 atmospheres of cooling water to avoid sintering and melting of the parts. The ionized discharge gas ejected from the graphite anode 5 is neutralized with a part of electrons generated by the lanthanum hexaboride cathode tube 1, and the electric neutrality of the plume is maintained.
Although the present invention has been described in terms of the preferred embodiments, it is not intended to be limited to the embodiments, and any person skilled in the art can make any possible variations and modifications to the technical solution of the present invention by using the methods and technical matters disclosed above without departing from the spirit and scope of the present invention, so any simple modifications, equivalent variations and modifications to the embodiments described above according to the technical matters of the present invention are within the scope of the technical matters of the present invention.

Claims (10)

1. The electromagnetic induction heating starting self-sustaining compact hollow cathode source is characterized by comprising a lanthanum hexaboride cathode tube, a graphite gasket, a graphite heating cavity, a boron nitride ceramic cavity, a graphite anode, a high-frequency induction heating coil, a graphite connecting pipe, an epoxy resin threaded pipe, a water-cooled cathode electrode, an anode graphite rod connecting bolt, a graphite connecting rod, a water-cooled anode electrode, an insulating flange and an air inlet hole; the lanthanum hexaboride cathode tube and the graphite gasket form a cathode inner assembly, the cathode inner assembly is integrally nested into a graphite heating cavity, the periphery of the graphite heating cavity is fixed and kept coaxial with a boron nitride ceramic cavity through threads, and the graphite anode is mounted in a fitting way and kept coaxial with a concave cavity structure at the front end of the boron nitride ceramic cavity; the high-frequency induction heating coil is coaxially sleeved on the periphery of the boron nitride ceramic cavity, and the boron nitride ceramic cavity is not contacted with the high-frequency induction heating coil; the rear end of the graphite connecting pipe is coaxially connected with the front end of the hollow double-layer water-cooled cathode electrode through threads, and the water-cooled cathode electrode penetrates through the epoxy resin threaded pipe to be fixed on the insulating flange and is kept coaxial; the front end of the graphite connecting pipe is coaxially connected with the graphite heating cavity through threads in the graphite heating cavity, and the end part of the graphite connecting pipe is attached to the graphite gasket; the rear end screw hole of the graphite connecting rod and the front end screw thread of the water-cooled anode electrode form a fixed structure, and the front end of the graphite connecting rod is fixed by an anode graphite rod connecting bolt through an extending structure of the graphite anode; the water-cooled anode electrode is fixed on a screw hole of the insulating flange through external threads, and two ends of the high-frequency induction heating coil respectively penetrate through the open holes of the insulating flange to be fixed; discharge gas is injected from the air inlet hole, enters the lanthanum hexaboride cathode tube after passing through the hollow tube structure in the water-cooled cathode electrode and the graphite connecting tube, is ionized and becomes plasma, and is sprayed out from the middle hole of the graphite anode.
2. The electromagnetic induction heating activated self-sustaining compact hollow cathode source of claim 1, wherein said lanthanum hexaboride cathode tube is a hollow cathode tube and is made of lanthanum hexaboride having a melting point of 2715 ℃.
3. The electromagnetic induction heating starting self-sustaining compact hollow cathode source according to claim 1, wherein the graphite heating cavity is made of high-hardness graphite with a wall thickness of 2mm, a hollow tube is arranged in the graphite heating cavity and used for installing a lanthanum hexaboride cathode tube, the tube wall of the hollow tube is used for being coupled with a high-frequency induction heating coil to realize induction heating, external threads of the hollow tube are used for fixing a boron nitride ceramic cavity, and internal threads at the rear end of the hollow tube are used for being connected with a graphite connecting tube.
4. An electromagnetic induction heating start-up self-sustaining compact hollow cathode source as claimed in claim 1, wherein said high frequency induction heating coil effects heating while internally creating a magnetic field coaxial with the lanthanum hexaboride cathode tube.
5. The electromagnetic induction heating starting self-sustaining compact hollow cathode source according to claim 1, wherein the high-frequency induction heating coil is formed by winding copper tubes, cooling water is filled in the high-frequency induction heating coil, the high-frequency induction heating coil heats the lanthanum hexaboride cathode tube to more than 1750 ℃ within 1-5 minutes, then the high-frequency induction heating coil is turned off, and self-sustaining heating is realized by utilizing plasma current; during self-sustaining heating, the high frequency induction heating coil applies a steady-state current to generate an externally applied steady-state magnetic field.
6. The electromagnetic induction heating start self-sustaining compact hollow cathode source as recited in claim 1, wherein said graphite connecting tube is hollow, and one end of said graphite connecting tube remote from said graphite heating chamber is connected with a water-cooled cathode electrode.
7. The electromagnetic induction heating activated self-sustaining compact hollow cathode source of claim 1, wherein said graphite anode elongate structure is fitted with a graphite connecting rod.
8. The electromagnetic induction heating starting self-sustaining compact hollow cathode source as recited in claim 1, wherein the external graphite heating chamber of the lanthanum hexaboride cathode tube is coupled with a high frequency induction heating coil to apply 80 kHz high current, the graphite heating chamber is heated to the working temperature by induction, and heat is uniformly conducted to the lanthanum hexaboride cathode tube, and the graphite heating chamber is in close contact with the lanthanum hexaboride cathode tube; the operating temperature is >1750 ℃.
9. The electromagnetic induction heating start-up self-sustaining compact hollow cathode source of claim 1, wherein said water cooled cathode electrode and water cooled anode electrode are each provided with a main water inlet, a main water outlet and an internal cooling water cavity.
10. An electromagnetic induction heating start-up self-sustaining compact hollow cathode source as claimed in claim 1, wherein said discharge gas is He, ar, xe, kr or N 2.
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CN113660759A (en) * 2021-08-12 2021-11-16 合肥综合性国家科学中心能源研究院(安徽省能源实验室) A plasma source with large size and high emission current density

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