A hot cathode combined with an air charging system

Abstract

A hot cathode combined with an inflation system includes an inflation system, a heating system and a cathode component. The hot cathode electron gun includes a design for direct current heating and indirect current heating of the hot cathode. The design integrates the cathode material, the heating system and the inflation system into an airtight whole, or inflates the cathode through an independent inflation pipe, so that the cathode surface becomes the inflation port of the device, thereby increasing the local neutral density on the cathode surface and suppressing the space charge effect, thereby achieving a higher electron emission capability. The design is particularly suitable for hot cathode devices made of cathode materials such as lanthanum hexaboride that are not easily processed into filaments, and can greatly improve their electron emission capability.

Description

Technical Field

[0001] The invention relates to the field of hot cathode electron sources, in particular to a hot cathode system design method applicable to electron guns and plasma high-energy electron sources, and more particularly to a hot cathode combined with a gas filling system. Background Art

[0002] The hot cathode is a widely used electron source device. It is the core component of the electron source in cathode ray tubes and other electron gun devices. Electron gun devices are still widely used in industrial fields such as atomic spectroscopy and material processing. Hot cathodes are still important devices in industrial fields such as atomic spectroscopy and material processing. In plasma research, hot cathode discharge provides a plasma environment free from radio frequency and microwave interference, providing a universal experimental platform for research in the fields of space plasma, basic plasma physics processes, tokamak divertor plasma, plasma diagnostic physics, etc., and supports important large scientific platforms abroad such as UCLA's LAPD large linear device and the increasingly popular tokamak divertor simulator. Therefore, improving the emission performance of hot cathode discharge will bring about a general empowerment improvement in related fields.

[0003] There are generally two types of cathode materials for hot cathode devices. One is that metal materials such as tungsten and tantalum are used as cathodes. Metal materials have very good plasticity and elasticity, and are easily processed into complex and delicate shapes such as strips, filaments, and spirals to make DC heating cathodes. However, metal materials generally have a higher work function, resulting in an emission temperature of about 2000C and a lower emission per unit area. Under high emission temperatures, the blackbody radiation luminescence of metal materials is also quite strong, which is particularly affected in plasma or atomic spectroscopy applications that require spectral diagnosis. With the advancement of compound material technology, compound cathodes represented by lanthanum hexaboride have begun to become new cathode materials in recent years. These cathode materials have a work function far lower than that of metals, resulting in an emission temperature that is nearly 1000 degrees lower than that of metal materials, and the emission per unit area has also been greatly improved. However, compound cathode materials are generally very fragile, making it difficult for them to be made into filaments. This results in compound cathodes generally being made into powder or cake form and installed in a filament heating system to become an indirect heating hot cathode device. Of course, with the popularization of high current power supplies and vacuum electrode technology, there are more specially designed DC-heated lanthanum hexaboride hot cathodes in recent years.

[0004] Whether it is indirect heating or DC heating, due to the increase in volume radius, the lanthanum hexaboride and other compound cathodes in the plasma they form are much larger than the Debye radius of the plasma itself, resulting in the emission current of these hot cathodes being limited by space charge. This is a phenomenon in which electrons accumulate near the cathode, resulting in a virtual cathode space potential structure that limits electron emission. On the contrary, very thin metal filaments can often form an amount of electrons that is not limited by the virtual cathode. Generally, hot cathodes that are limited by space charge must increase their cathode voltage to increase the amount of electron emission, which forms a considerable limitation in some applications that have precise requirements for electron energy. In addition, recent studies have found that if a DC-heated hot cathode is limited by space charge, it may be further limited by the surface magnetic field formed by the heating current, resulting in discharge quenching. In the automated control work of a DC-heated hot cathode discharge system, this phenomenon may cause the automatic system to be unable to identify whether the heating current is insufficient or excessive, resulting in system damage. In summary, a hot cathode design that can alleviate space charge limitation will have a considerable improvement in both increasing the emission performance of the hot cathode and increasing the safety of the device used in the system. Summary of the invention

[0005] In a series of studies related to hot cathodes, we found that as long as the critical dimensions of the hot cathode material are much larger than the plasma Debye radius, that is, the cathode material is a plate or a strip of >0.5 mm, its electron emission must be limited by the space charge effect. We further found that in this case, if the hot cathode is designed as a DC heated electron gun, the magnetic field formed by the DC heating itself on the cathode surface will bind the emitted electrons back to the cathode surface, thereby preventing emission. This phenomenon will cause the hot cathode discharge to be quenched from the space charge emission state, and then damage the cathode device due to overheating [1]. Space charge limitation and magnetic confinement phenomena limit the improvement in hot cathode efficiency that can be obtained by using compound cathode materials, and we know that both effects can be mitigated by increasing the neutral density and cathode bias. The increase in neutral density can increase neutral collisions on the cathode surface, increase the ions trapped by the space charge effect, fill the virtual cathode in the space charge effect, that is, the potential well in space, and thus reduce the space charge effect. In addition, the increase in local neutral density can increase the local plasma density, thereby enhancing the local electric field through the compression of the Debye radius, making electrons more effectively discharged, reducing electron accumulation and thus alleviating the space charge effect. The increase in cathode bias directly increases the electron discharge efficiency, and also reduces the electron accumulation near the cathode and alleviates the space charge effect.

[0006] However, the cathode bias also determines the energy of the emitted electrons, which limits applications that require precise control of electron energy. On the other hand, the neutral density also changes the neutral collision path. In some applications, there are also strict requirements for the neutral density of the device, which cannot be changed at will.

[0007] The present invention utilizes the phenomenon that the local gas pressure at the gas filling port in plasma devices and other electron gun applications is higher than that in other parts of the device, and combines the device gas filling with the hot cathode device, so that the gas in plasma and other electron gun device applications that require gas filling is filled into the device from the hot cathode surface, thereby greatly improving the neutral density of the hot cathode surface. This design can greatly alleviate the space charge phenomenon by increasing the local neutral density without changing the overall neutral density of the device, thereby greatly improving the electron emission performance of the hot cathode.

[0008] The present invention provides a hot cathode combined with an inflation system, and the technical solution adopted is: a hot cathode design that utilizes the increase of local collision to improve the electron emission capability, including an inflation system, a heating system and a cathode component. The design integrates the inflation system, the heating system and the cathode surface into a sealed whole with a one-way airflow, or converts the hot cathode into an inflation port through an independent inflation pipeline, so that the inflation gas is only output from the cathode surface into a plasma device using the hot cathode and other electron gun applications with inflation requirements.

[0009] The hot cathode design utilizes the principle that the neutral density of the gas filling port is greater than the overall density of the device, thereby increasing the neutral density of the hot cathode surface, thereby filling the virtual cathode through the increase of neutral collisions, and easing the limitation of the space charge effect on electron emission. By combining the hot cathode with the gas filling system of the device as a whole, the hot cathode design does not increase the neutral density of the device as a whole, thereby independently improving the electron emission performance of the hot cathode without affecting the overall operation of the device.

[0010] The hot cathode design can be made into a DC heating system or an indirect heating system. In the DC heating system, the heating electrode can be added with a water cooling design. Both different hot cathode systems can greatly increase the electron emission through the design of the present invention.

[0011] The present invention adopts the following technical solution:

[0012] A direct current heating hot cathode combined with an air filling system, comprising: a housing (1), a vacuum flange (2), a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), a second insulating layer (8), a cathode (10), and an air filling port (11);

[0013] A vacuum flange (2) is provided at one end of the shell (1), and a cathode (10) is provided at the other end of the shell (1); a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), and a second insulating layer (8) are located inside the shell (1);

[0014] The gas filling port (11) is located on the vacuum flange (2), and the gas filling port (11) is communicated with the interior of the housing (1);

[0015] A first heating wire (5) is arranged on one side inside the housing (1), the first heating wire (5) is wrapped with a first insulating layer (7), a cathode (10) is arranged at one end of the first heating wire (5), and the other end of the first heating wire (5) is connected to a first heating current electrode (3);

[0016] A second heating wire (6) is arranged on the other side of the interior of the housing (1), the second heating wire (6) is wrapped with a second insulating layer (8), a cathode (10) is arranged at one end of the second heating wire (6), and the other end of the second heating wire (6) is connected to a second heating current electrode (4).

[0017] Furthermore, the hot cathode further comprises an air filling pipe (9), the air filling pipe (9) being coaxially arranged with the outer shell (1), the air filling pipe (9) being located inside the outer shell (1), and the air filling pipe (9) being in communication with the inside of the outer shell (1).

[0018] Furthermore, the hot cathode further comprises a front shell sleeve (12), the front shell sleeve (12) being connected to the shell (1) in a threaded manner, and the front shell sleeve (12) pressing the cathode (10) onto the first heating current electrode (3) and the second heating current electrode (4).

[0019] Furthermore, the cathode (10) is in sheet shape, and a through hole is provided on the surface of the cathode (10), wherein the through hole communicates with the interior of the housing.

[0020] Furthermore, the material used for the cathode (10) is lanthanum hexaboride or barium oxide.

[0021] An indirect heating hot cathode combined with an air filling system, comprising: a housing (1), a vacuum flange (2), a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), a second insulating layer (8), a cathode (10), an air filling port (11), a heating coil (13), and a heating coil electrically insulating thermally conductive pad (14);

[0022] A vacuum flange (2) is provided at one end of the shell (1), and a cathode (10) is provided at the other end of the shell (1); a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), and a second insulating layer (8) are located inside the shell (1);

[0023] The gas filling port (11) is located on the vacuum flange (2), and the gas filling port (11) is communicated with the interior of the housing (1);

[0024] A first heating wire (5) is disposed on one side of the interior of the housing (1), the first heating wire (5) being wrapped with a first insulating layer (7), one end of the first heating wire (5) being connected to a heating coil (13), a heating coil electrically insulating thermally conductive pad (14) being disposed between the heating coil (13) and the cathode (10), and the other end of the first heating wire (5) being connected to a first heating current electrode (3).

[0025] A second heating wire (6) is arranged on the other side of the interior of the housing (1), the second heating wire (6) is wrapped with a second insulating layer (8), one end of the second heating wire (6) is connected to the heating coil (13), and the other end of the second heating wire (6) is connected to the second heating current electrode (4).

[0026] Furthermore, the hot cathode further comprises an air filling pipe (9), the air filling pipe (9) being coaxially arranged with the outer shell (1), the air filling pipe (9) being located inside the outer shell (1), and the air filling pipe (9) being in communication with the inside of the outer shell (1).

[0027] Preferably, the hot cathode further comprises a front shell sleeve (12), the front shell sleeve (12) being connected to the shell (1) in a threaded manner, and the front shell sleeve (12) pressing the cathode (10) onto the first heating current electrode (3) and the second heating current electrode (4).

[0028] Preferably, the cathode (10) is in sheet shape, and a through hole is provided on the surface of the cathode (10), wherein the through hole communicates with the interior of the housing.

[0029] Preferably, the material used for the cathode (10) is lanthanum hexaboride or barium oxide.

[0030] Furthermore, the through hole on the surface of the cathode (10) is consistent with the through hole on the heating coil electrically insulating thermally conductive gasket (14).

[0031] The present invention discloses a hot cathode combined with an inflation system, specifically an electron emission hot cathode system suitable for lanthanum hexaboride and other hot cathodes of materials that are difficult to make into filaments. The inflation system is integrated with the heating and cathode components and packaged into a sealed whole, thereby locally increasing the neutral density on the surface of the cathode material and suppressing the space charge effect on the cathode surface, thereby obtaining a larger electron emission current.

[0032] Furthermore, the hot cathode combined with the inflation system of the present invention integrates the inflation system with the heating and cathode components, so that the cathode target surface simultaneously becomes the gas inlet for the plasma source or electron gun inflation, thereby increasing the neutral collision property of the cathode surface and obtaining an increase in the cathode electron emission current.

[0033] The beneficial effects of the present invention are:

[0034] The present invention provides a hot cathode design that utilizes the increase in local collision to improve the electron emission capability, which is suitable for indirect heating and direct current heating hot cathode systems. By combining the hot cathode with the gas filling system of the entire device, the hot cathode design does not increase the neutral density of the entire device, thereby independently improving the electron emission performance of the hot cathode without affecting the overall operation of the device. The present invention is particularly effective in improving the performance of hot cathode systems using compound cathode materials, such as lanthanum hexaboride or barium oxide, or using plate-type cathodes in low-pressure vacuum plasma devices.

[0035] References:

[0036] 1. Yip, C.-S., et al., Extinguishment of hot cathode discharges by space-charge and surface magnetic effects. Plasma Sources Science and Technology, 2020. 29(11): p. 115021. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a DC heating hot cathode combined with an air charging system according to the present invention;

[0038] Figure 2 A schematic diagram of an indirect heating hot cathode combined with an air charging system according to the present invention;

[0039] Figure 3 Schematic diagram of the experimental setup for verification;

[0040] Figure 4 To verify the data of the increase of the hot cathode limit emission current by the present invention in the experiment;

[0041] Figure 5 The data are provided to verify the effect of increasing cathode current on plasma parameters in the experiment.

[0042] In the figure, 1-housing, 2-vacuum flange, 3-first heating current electrode, 4-second heating current electrode, 5-first heating wire, 6-second heating wire, 7-first insulating layer, 8-second insulating layer, 9-inflating pipe, 10-cathode, 11-inflating port, 12-housing front cover, 13-heating coil, 14-electrically insulating thermal conductive gasket of heating coil, 15-molecular pump, 16-air inlet A, 17-hot cathode, 18-air inlet B. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0044] According to one embodiment of the present invention, a DC heating hot cathode combined with an air charging system is provided. Figure 1 FIG. 1 is a schematic diagram of a DC heating hot cathode of the present invention. Figure 1 As shown, the DC heating type hot cathode includes: a shell 1, a vacuum flange 2, a first heating current electrode 3, a second heating current electrode 4, a first heating wire 5, a second heating wire 6, a first insulating layer 7, a second insulating layer 8, an inflation pipe 9, a cathode 10 and an inflation port 11. A vacuum flange 2 is provided at one end of the shell 1, and a cathode 10 is provided at the other end of the shell 1. The shell 1 is welded to the vacuum flange 2. The first heating current electrode 3 and the second heating current electrode 4 are located at the vacuum flange 2. The shell 1 is a pipeline. The first heating current electrode 3, the second heating current electrode 4, the first heating wire 5, the second heating wire 6, the first insulating layer 7, the second insulating layer 8, the inflation pipe 9 and the cathode 10 are provided in the internal cavity of the shell. An inflation pipe 9 is coaxially provided inside the shell 1. A first heating wire 5 is provided on one side between the inflation pipe 9 and the shell 1, and the first heating wire 5 is wrapped with a first insulating layer 7. One end of the first heating wire 5 is connected to the cathode 10, and the other end of the first heating wire 5 is connected to the first heating current electrode 3. A second heating wire 6 is provided on the other side between the gas filling pipe 9 and the shell 1, and the second heating wire 6 is wrapped with a second insulating layer 8. One end of the second heating wire 6 is connected to the cathode 10, and the other end of the second heating wire 6 is connected to the second heating current electrode 4. The front sleeve 12 of the shell is connected to the shell 1 in a threaded manner, and the cathode 10 is pressed on the first heating current electrode 3 and the second heating current electrode 4. The cathode 10 is processed into a sheet shape, and a through hole is drilled on the surface of the cathode 10 for the neutral gas to flow out. The through hole on the surface of the cathode 10 is connected to the gas filling pipe 9.

[0045] Among them, the first heating current electrode 3, the second heating current electrode 4, the first heating wire 5 extending from the first heating current electrode 3, the second heating wire 6 extending from the second heating current electrode 4, the first insulating layer 7, the second insulating layer 8, the charging pipe 9, and the back of the cathode 10 are all wrapped in a sealed shell 1. One end of the charging pipe 9 is connected to the vacuum flange 2, and the vacuum flange 2 is provided with a charging port 11, and the charging port 11 is connected to the charging pipe 9. The charging port 11 on the vacuum flange is connected to the gas supply system of traditional applications, such as a mass flow controller or a needle valve. The first heating current electrode 3 and the second heating current electrode 4 are vacuum electrodes. The charging port 11 is connected to the inside of the shell.

[0046] Due to insulation requirements, it is recommended that the shell 1 be made of ceramic, or the front end be welded with ceramic. Optionally, the cathode material can be made into a ring, a maze, or a ring with a gap, etc., so as to form a unidirectional current with the electrode. The first insulating layer 7 and the second insulating layer 8 inside the pipeline are two insulating layers for electrical isolation to prevent the heating electrode from leaking electricity to the inflation pipe 9. If the airtightness of the shell 1 is sufficient and there is no demand for airflow efficiency, the inflation pipe 9 can be omitted and the shell 1 itself can be used as an airtight pipe. The front sleeve 12 of the shell should be processed with ceramic parts and connected to the shell 1 in a threaded manner to press the cathode onto the heating electrode. The cathode 10 uses a compound cathode material, such as lanthanum hexaboride or barium oxide. The cathode 10 can be a plate-type cathode. Optionally, the material of the cathode 10 can be cylindrical or square columnar lanthanum hexaboride.

[0047] The inflation port 11 is communicated with the inner space of the shell 1. The inflation pipe 9 is communicated with the inner space of the shell 1.

[0048] The specific implementation of the present invention is as follows: A hot cathode that utilizes the increase of local collision to improve the electron emission capability includes a gas filling system, a heating system and a cathode component. The device is inflated by sealing a pipe confined inside the hot cathode, so that the cathode position becomes an outlet facing the vacuum of the device, thereby obtaining a local gas pressure and a neutral gas density far higher than the overall device near the surface of the cathode emitting electrons. The neutral gas improves the discharge of emitted electrons from the space charge potential well (i.e., the virtual cathode) by increasing the local plasma density, and at the same time produces a large number of trapped ions in the potential well through ion-neutral collision, thereby filling the space charge potential well. These effects will slow down the space charge effect, thereby increasing the electron emission amount of the hot cathode.

[0049] According to another embodiment of the present invention, an indirect heating type hot cathode combined with an air charging system is provided, which is arranged as follows: Figure 2 shown. Figure 2 A schematic diagram of an indirectly heated hot cathode. Figure 2 and Figure 1The difference is that the indirect heating type hot cathode also includes: a heating coil 13 and a heating coil electrically insulating and thermally conductive gasket 14. One end of the first heating wire 5 is connected to the heating coil 13, and a heating coil electrically insulating and thermally conductive gasket 14 is provided between the heating coil 13 and the cathode 10, and the other end of the first heating wire 5 is connected to the first heating current electrode 3. One end of the second heating wire 6 is connected to the heating coil 13, and an electrically insulating and thermally conductive gasket 14 is provided between the heating coil 13 and the cathode 10, and the other end of the second heating wire 6 is connected to the second heating current electrode 4. The cathode 10 is processed into a sheet shape, and a through hole is drilled on the surface of the cathode 10 for the outflow of neutral gas, and the through hole should be consistent with the through hole on the heating coil electrically insulating and thermally conductive gasket 14. The through hole on the surface of the cathode 10 is connected to the inflation pipe 9. The through hole on the heating coil electrically insulating and thermally conductive gasket 14 can be made into a single hole in the center, or multiple through holes can be drilled around the center. The latter is especially recommended in applications such as magnetized linear devices that require electron emission from the magnetic field axis. The first insulating layer 7 and the second insulating layer 8 inside the pipeline are electrically isolated to prevent the heating electrode from leaking to the shell. If the airtightness of the shell 1 is sufficient and there is no demand for airflow efficiency, the inflation pipe 9 can be omitted and the shell 1 itself can be used as an airtight pipe. The front sleeve 12 of the shell should be connected to the shell 1 in a threaded manner, and the cathode 10 is pressed on the first heating current electrode 3 and the second heating current electrode 4. Figure 2 In the compact design, the housing 1, the housing front cover 12 and the cathode 10 itself need to be uniformly electrically connected and insulated from the first heating wire 5 and the second heating wire 6, so metal materials are required. The heating system is electrically isolated by the first insulating layer 7 and the second insulating layer 8 (usually ceramic) inside the housing 1 to prevent leakage to the housing 1 and the inflation pipe 9. Compared with the direct current heating hot cathode system, the indirect heating hot cathode system is easier to implement using a center through hole design due to the coaxiality of the coil.

[0050] The specific implementation of the present invention is as follows: A hot cathode design that utilizes the increase of local collision to improve the electron emission capability includes a gas filling system, a heating system and a cathode component. The device is inflated by sealing a pipeline confined inside the hot cathode, so that the cathode position becomes an outlet facing the vacuum of the device, thereby obtaining a local gas pressure and neutral gas density far higher than the overall device near the surface where the cathode emits electrons. The neutral gas improves the discharge of emitted electrons from the space charge potential well (i.e., virtual cathode) by increasing the local plasma density, and at the same time produces a large number of trapped ions in the potential well through ion-neutral collision, thereby filling the space charge potential well. These effects will slow down the space charge effect, thereby increasing the electron emission amount of the hot cathode. Since the cathode is a flat plate, the cathode surface gas pressure and neutral gas density can be further controlled by the design of the through hole: under the same air intake, due to the flux conservation, the smaller the cross-section through which the gas passes, the higher the through density, so the fewer the number of holes and the finer the hole diameter, the greater the neutral gas density can be formed on a small part of the cathode surface. If, on the other hand, a more uniform emission over the entire hot cathode emitting surface is desired, multiple through holes may be drilled.

[0051] The use of the present invention is as follows:

[0052] Figure 1 The described method of using the directly heated hot cathode is as follows:

[0053] 1. First, you need to install the hot cathode into the device, directly from the vacuum flange 2 plus the ordinary vacuum gasket to the window of the device.

[0054] 2. Connect the first heating current electrode 3 and the second heating current electrode 4 to the positive and negative electrodes of a DC power supply for heating purposes, and connect one of them to the negative electrode of a bias power supply. This is the same as the operation method of general DC heating hot cathode.

[0055] 3. Connect an independent flow controller from the gas filling port 11. In the application of the inert gas plasma source below 0.5Pa, the hot cathode is also used as the only gas filling port. After ensuring that the device obtains the required gas pressure for work through filling, start the hot cathode, that is, apply a bias to the hot cathode, and heat it through a heating current until the required emission current is obtained. If increasing heating under any bias voltage cannot obtain a higher current, it is necessary to increase the bias voltage to obtain a higher emission current. The startup is now complete.

[0056] 4. In applications above 0.5Pa, you can first use other inflation ports of the device itself to inflate to obtain the required air pressure, start the hot cathode, and then increase the inflation volume of the hot cathode's inflation port to replace the device's inflation volume (i.e. reduce the inflation volume of the device's own inflation port) until the highest emission current is obtained, and then perform heating regulation for the required emission current.

[0057] Figure 2 The described indirect heated hot cathode is used as follows:

[0058] 1. Use Figure 2 When the indirect heating type hot cathode is described, the vacuum flange 2 should be added with an insulating vacuum gasket and installed on the window of the device.

[0059] 2. Connect the first heating current electrode 3 and the second heating current electrode 4 to the positive and negative electrodes of a DC power supply for heating purposes, and connect the negative electrode of the bias power supply to the vacuum flange 2. Note that the vacuum flange exposed outside the device has a negative bias voltage at this time, and attention should be paid to electric shock safety.

[0060] 3. Connect an independent flow controller from the gas filling port 11. In the application of the inert gas plasma source below 0.5Pa, the hot cathode is also used as the only gas filling port. After ensuring that the device obtains the required gas pressure for work through filling, start the hot cathode, that is, apply a bias to the hot cathode, and heat it through a heating current until the required emission current is obtained. If increasing heating under any bias voltage cannot obtain a higher current, it is necessary to increase the bias voltage to obtain a higher emission current. The startup is now complete.

[0061] 4. In applications above 0.5Pa, you can first use other inflation ports of the device itself to inflate to obtain the required air pressure, start the hot cathode, and then increase the inflation volume of the hot cathode's inflation port to replace the device's inflation volume (i.e. reduce the inflation volume of the device's own inflation port) until the highest emission current is obtained, and then perform heating regulation for the required emission current.

[0062] Figure 3 , 4 The validation results of an experiment demonstrating the proof-of-principle by changing the gas inlet in a multi-dipole hot cathode discharge device are presented. Figure 3-4 The hot cathode 17 used is Figure 1 One possible design of a directly heated hot cathode is shown, except that the cathode itself is not integrated into a sealed unit with the inflation system. Figure 3 The multi-dipole hot cathode plasma device test platform (DTS-II) for principle verification is one of the common scenarios of the present invention. The plasma is produced by hot cathode discharge. DTS-II is a multi-dipole confined discharge device with a vacuum chamber length of 800mm and a diameter of 500mm. Three sets of 16 permanent magnets are installed between the radial wall and the two axial walls of the cavity, respectively, to generate multi-dipole magnetic field confinement near the surface of the device wall, thereby obtaining a plasma with uniform center and no magnetic field influence. The device is evacuated by a molecular pump 15, and the background vacuum is about 10 -3Pa. In order to verify the beneficial effects of the present invention, we arranged the gas filling ports of the device at two different positions: the gas inlet A16 is located on a radial window at least 500mm away from the hot cathode 17, while the gas inlet B18 extends to within 5mm of the center of a 15cm long, 2mm diameter cylindrical lanthanum hexaboride DC-heated hot cathode 17. Since the high-density area near the gas filling port only lasts within 1cm of the gas filling port, the gas inlet A16 can be regarded as a conventional hot cathode discharge working mode, while the gas inlet B18 can be regarded as a simulation of the gas filling method of the present invention. This verification experiment uses argon gas with a gas filling volume of 2-6sccm and an air pressure of 0.03-0.09Pa. Regardless of which gas filling port is used for intake, the final overall gas pressure variation is within ±5%, which is within the error caused by factors such as measurement and vacuuming. In the experiment, the hot cathode bias voltage was uniformly set to -60V. The verification results of the emission current are shown in the figure. Figure 4 As shown, in a DC heated hot cathode discharge, the limiting emission current can be increased from 0.14 A to 0.25 A in the lowest gas pressure in the experimental range (about 0.03 Pa) simply by moving the gas filling port from far away from the hot cathode (gas inlet A16) to near the hot cathode (gas inlet B18). In an environment of 0.09 Pa, the limiting emission current is increased from 2.18 A to 5.56 A, an increase of more than two times.

[0063] In order to observe the influence of the present invention on the plasma parameters, we used the inlet A16 and the inlet B18 to obtain the same gas pressure of 0.12 Pa and scanned the cathode emission current obtained by using the two inlets respectively, and measured the obtained plasma parameters using a Langmuir probe. The results are as follows: Figure 5 As shown, at any same emission current, the plasma parameters obtained by changing the gas inlet from the gas inlet A16 far from the hot cathode to the gas inlet B18 5 mm near the hot cathode are the same. Therefore, using the present invention to improve the electron emission performance of the hot cathode does not affect the overall operation of the device.

[0064] Figure 3 , 4 The experiment shown in 5 is only a proof of principle demonstration. Since the cathode itself is not fully integrated with the gas filling system, and only a small part (about 1 / 10 of the total emission area) of the hot cathode material is immersed in the area where the neutral gas pressure increases, the actual electron emission enhancement effect is relatively poor. However, it has well demonstrated the gain of the hot cathode electron emission amount of the present invention. The actual effect of the present invention will be much better than the gain shown in the proof of principle.

[0065] Although the above describes the illustrative specific embodiments of the present invention to facilitate the understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A DC heated hot cathode combined with an air charging system, It is characterized in that include: A housing (1), a vacuum flange (2), a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), a second insulating layer (8), a cathode (10), and a gas filling port (11); A vacuum flange (2) is provided at one end of the shell (1), and a cathode (10) is provided at the other end of the shell (1); a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), and a second insulating layer (8) are located inside the shell (1); The gas filling port (11) is located on the vacuum flange (2), and the gas filling port (11) is communicated with the interior of the housing (1); A first heating wire (5) is arranged on one side inside the housing (1), the first heating wire (5) is wrapped with a first insulating layer (7), a cathode (10) is arranged at one end of the first heating wire (5), and the other end of the first heating wire (5) is connected to a first heating current electrode (3); A second heating wire (6) is arranged on the other side of the interior of the housing (1), the second heating wire (6) is wrapped with a second insulating layer (8), a cathode (10) is arranged at one end of the second heating wire (6), and the other end of the second heating wire (6) is connected to a second heating current electrode (4).

2. The hot cathode according to claim 1, It is characterized in that The hot cathode further comprises an air filling pipe (9), the air filling pipe (9) being coaxially arranged with the outer shell (1), the air filling pipe (9) being located inside the outer shell (1), and the air filling pipe (9) being in communication with the inside of the outer shell (1).

3. The hot cathode according to claim 1, It is characterized in that The hot cathode further comprises a front shell sleeve (12), the front shell sleeve (12) being connected to the shell (1) in a threaded manner, and the front shell sleeve (12) pressing the cathode (10) onto the first heating current electrode (3) and the second heating current electrode (4).

4. The hot cathode according to claim 1, It is characterized in that The cathode (10) is in sheet shape, and a through hole is provided on the surface of the cathode (10), wherein the through hole communicates with the interior of the shell.

5. The hot cathode according to claim 1, It is characterized in that The material used for the cathode (10) is lanthanum hexaboride or barium oxide.

6. An indirectly heated hot cathode combined with an air charging system, It is characterized in that include: A housing (1), a vacuum flange (2), a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), a second insulating layer (8), a cathode (10), an air filling port (11), a heating coil (13), and a heating coil electrically insulating thermally conductive gasket (14); A vacuum flange (2) is provided at one end of the shell (1), and a cathode (10) is provided at the other end of the shell (1); a first heating current electrode (3), a second heating current electrode (4), a first heating wire (5), a second heating wire (6), a first insulating layer (7), and a second insulating layer (8) are located inside the shell (1); The gas filling port (11) is located on the vacuum flange (2), and the gas filling port (11) is communicated with the interior of the housing (1); A first heating wire (5) is disposed on one side of the interior of the housing (1), the first heating wire (5) being wrapped with a first insulating layer (7), one end of the first heating wire (5) being connected to a heating coil (13), a heating coil electrically insulating thermally conductive pad (14) being disposed between the heating coil (13) and the cathode (10), and the other end of the first heating wire (5) being connected to a first heating current electrode (3). A second heating wire (6) is arranged on the other side of the interior of the housing (1), the second heating wire (6) is wrapped with a second insulating layer (8), one end of the second heating wire (6) is connected to the heating coil (13), and the other end of the second heating wire (6) is connected to the second heating current electrode (4).

7. The hot cathode according to claim 6, It is characterized in that The hot cathode further comprises an air filling pipe (9), the air filling pipe (9) and the outer shell (1) are arranged coaxially, the air filling pipe (9) is located inside the outer shell (1), and the air filling pipe (9) is communicated with the inside of the outer shell (1); The hot cathode further comprises a front shell (12), the front shell (12) being connected to the shell (1) in a threaded manner, and the front shell (12) pressing the cathode (10) onto the first heating current electrode (3) and the second heating current electrode (4); The cathode (10) is in sheet shape, and a through hole is provided on the surface of the cathode (10), wherein the through hole communicates with the interior of the shell; The material used for the cathode (10) is lanthanum hexaboride or barium oxide.

8. The hot cathode according to claim 7, It is characterized in that The through hole on the surface of the cathode (10) is consistent with the through hole on the electrically insulating thermally conductive gasket (14) of the heating coil.

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