RU2219683C2 - Plasma source and its operating process - Google Patents

Abstract

FIELD: space engineering; taking off electrostatic potential of space vehicles and plasma contactor in electrodynamic cable systems. SUBSTANCE: plasma source has at least two hollow cathodes each incorporating emitter, starting heater, set of fire walls, and igniter rod, as well as filament power supplies connected to starter heaters and ignition discharge sources connected to emitters and igniter electrodes. Hollow cathodes are spaced maximum 0.2 m apart and their emitters are electrically interconnected. Operating process of plasma source incorporating at least two hollow cathodes includes plasma-forming gas supply to one of cathodes, start-up heating of the latter, ignition of discharge between emitter and igniter electrode followed by heater turn-off. Upon ignition of discharge in first cathode plasma-forming gas is fed to other cathode and ignition discharge is set up therein. As an alternative, operating algorithm of plasma source can be simplified by supplying plasma-forming gas to both cathodes at a time and upon start-up heating of one of cathodes power supplies of ignition discharges of both cathodes are turned on simultaneously. In addition after ignition discharges are set up in both cathodes that in first cathode can be turned off. EFFECT: enhanced ion current injected by plasma source. 4 cl, 2 dwg

Description

 The invention relates to plasma sources used in space technology, namely, plasma contactors for electrodynamic cable systems, cathode-compensators of electro-reactive plasma engines (ERE) and plasma sources for removing the electrostatic potential of the spacecraft.

 Known hollow cathode containing an emitter, a starting heater, a system of heat shields and an ignition electrode [1].

 There is a known method of operation of a hollow cathode, for which a working gas (for example, xenon) is supplied, start heating is performed and a discharge is ignited on the ignition electrode [1].

 A known plasma source, adopted by the authors as a prototype, containing primary and backup hollow cathodes, electrically isolated from each other, each of which contains an emitter, a starting heater, a system of heat shields and an ignition electrode. The glow power sources are connected to the corresponding starting heaters, and the ignition power sources are connected to the corresponding ignition electrodes and emitters of the main and backup cathode [2].

 A known method of operation of a plasma source, adopted as a prototype, comprising supplying a plasma-forming gas to one of the hollow cathodes, its starting heating and ignition of the discharge between the emitter and the ignition electrode, after which the starting heater is turned off. The second hollow cathode is designed for redundancy and does not turn on [2].

 A common drawback of the known analogue and prototype, as well as the methods of their operation, is the low ion current, which, depending on the size of the hollow cathode, is 0.5 ... 2.0 mA. Due to the low ion current, the concentration of the outflowing plasma is low, which, in turn, limits the injected electron current.

 In known devices, the ignition discharge organized inside the hollow cathode is limited by structural elements, on the surfaces of which plasma recombination occurs. In addition, the electric potential decreases from the ignition electrode to the emitter. Such an electric field directs low-energy ions toward the emitter, which prevents their outflow into space, limiting the ion current to a level of 0.5 ... 2 mA.

 When creating the invention, the problem was solved to increase the injected ion current of the plasma source.

 The problem is solved due to the fact that in the plasma source containing at least two hollow cathodes, each of which contains an emitter, a starting heater, a system of heat shields and an ignition electrode, as well as glow power sources connected to the starting heaters and ignition sources discharge connected to the emitters and ignition electrodes, according to the invention, the hollow cathodes are placed at a distance of not more than 0.2 m from each other, and their emitters are electrically connected.

направлено от поджигного электрода второго катода, что способствует эффективной инжекции ионов.This connection allows you to organize, in addition to the ignition discharge in one cathode, an additional discharge in volume in front of the ignition electrode of another cathode. The additional discharge is not limited by the walls of the structure of the first cathode, and the electric field

directed from the ignition electrode of the second cathode, which contributes to the effective injection of ions.

 When the distance between the cathodes is less than 0.2 m, losses in electron transport are significantly reduced, which leads to a decrease in the supply voltage of the ignition discharge of the second cathode, increasing the efficiency of the plasma source as a whole.

 The specified technical result is also achieved by the fact that in the method of operation of a plasma source containing at least two hollow cathodes, including supplying a plasma-forming gas to one of the cathodes, its starting heating, ignition of a discharge in it between the emitter and the ignition electrode, after which the starting heater is turned off , according to the invention, after ignition of the discharge in the first cathode, a plasma-forming gas is supplied to the other cathode and the ignition discharge is ignited therein.

при этом спадает по мере удаления от поджигного электрода другого катода, что благоприятствует стоку ионов в пространство.The supply of plasma-forming gas to both hollow cathodes whose emitters are electrically connected, followed by ignition of the ignition discharge on the ignition electrodes of both cathodes, makes it possible to increase the level of injected ion current due to the fact that in addition to the ignition discharge, an additional discharge arises in the first cathode from the outside of the ignition electrode of the other cathode . Electrons shorted to the ignition electrode of another cathode ionize the gas flowing out of it. The plasma formation that appeared in front of the other cathode is not limited to the walls. Electric field

in this case, decreases with the distance from the ignition electrode of the other cathode, which favors the drain of ions into space.

 According to another embodiment of the plasma source, to simplify the control algorithm, the plasma-forming gas can be simultaneously supplied to both cathodes and, after the start of heating of one of the cathodes, the ignition discharge sources of both cathodes are simultaneously turned on.

 After occurrence of ignition discharges in both cathodes, the ignition discharge in the first cathode can be turned off, which reduces the total energy consumption of the plasma source.

 Thus, the plasma source and the method of its operation will increase the injected ion current by 15 ... 20 times.

 The invention is illustrated by drawings.

 Figure 1 shows the electro-pneumatic diagram of a plasma source.

 In FIG. 2 shows the topology of electric fields and the direction of motion of charged particles.

 The plasma source consists of a gas supply system containing a gas source 1, electric valves 2 and 3, pipelines 4 of two hollow cathodes 5 and 6, and a power supply system. In turn, the cathodes consist of electrically connected emitters 7 and 8, electrical insulating tubes 9 and 10 for isolating the emitters from pipelines 4 and body parts, starting heaters 11 and 12, ignition electrodes 13 and 14, made in the form of cups with axial holes 15 and 16. The power supply system contains glow power sources 17 and 18, current sources 19 and 20, and power valves solenoid valves 21 and 22.

 The plasma source works as follows.

показана на фиг. 2, замыкается на поджигной электрод 14 катода 6. Перенос электронов сопровождается столкновениями с потоками нейтральных атомов 24, истекающих из отверстий 15 и 16, что приводит к их дополнительной ионизации. Перед поджигным электродом 14 вероятность ионизационных столкновений возрастает за счет увеличения концентрации нейтральных атомов, плотности электронного тока и энергии электронов, что приводит к возникновению дополнительной области плазмообразования 25, которая инжектирует ионный ток в 15...20 раз больше, чем ионный ток, истекающего из катода 5. Электрическое сопротивление вакуумного промежутка между катодами существенно выше электрического сопротивления плазмы, поэтому электронный ток замыкается преимущественно в потоках нейтральных атомов 24, формируя траекторию движения электронов 23.Turning on the power source 21, open the electric valve 2 and gas from the gas source 1 to the cathode 5. Turning on the power source 17, using the starting heater 11, the emitter 7 of the cathode 5 is heated to operating temperatures. Then turn on the ignition source 19. After the appearance of current in the circuit of the source 19 and the occurrence of the ignition discharge, the glow source 17 is turned off. Then turn on the power source 22 to supply gas to the cathode 6 and similarly ignite in it an ignition discharge. The plasma arising in the cathode 5 flows into space through the hole 15. Part of the injected electrons 23, the trajectory of which is in an electric field

shown in FIG. 2, closes on the ignition electrode 14 of the cathode 6. Electron transfer is accompanied by collisions with flows of neutral atoms 24 flowing out of holes 15 and 16, which leads to their additional ionization. Before the ignition electrode 14, the probability of ionization collisions increases due to an increase in the concentration of neutral atoms, electron current density and electron energy, which leads to the appearance of an additional plasma formation region 25, which injects an ion current 15 ... 20 times more than the ion current flowing out cathode 5. The electrical resistance of the vacuum gap between the cathodes is significantly higher than the electrical resistance of the plasma, therefore, the electron current closes mainly in neutral flows x atoms 24, forming the trajectory of the electrons 23.

 The plasma source control algorithm according to another embodiment is simplified by simultaneously turning on the sources 21 and 22, and after starting heating of the cathode 5 while turning on the sources 19 and 20.

 To reduce the power consumption of the plasma source after the appearance of the rated current in the source 20, the ignition source 19 can be turned off.

Sources of information
1. RF patent 2012946, cl. 5 H 01 J 37/077.

2. V. Gopanchuk, A. Koryakin, A. Nesterenko, V. Ageyew and V. Syromyatnikov Plasma Contactor for Tether System. 37 ^th AIAA / Asme / SAE / ASEE JPC, 8-11 July 2001, Salt Lake City, Utah. AIAA 2001 - 3916 - prototype.

Claims (5)

1. A plasma source containing at least two hollow cathodes, each of which contains an emitter, a start heater, a system of heat shields and an ignition electrode, as well as a glow power source connected to the start heater, and an ignition discharge source connected to the emitter and ignition electrode, characterized in that the hollow cathodes are placed at a distance of not more than 0.2 m from each other, and their emitters are electrically connected. 2. The method of operation of a plasma source containing at least two hollow cathodes, including the supply of a plasma-forming gas to one of the cathodes, its starting heating, ignition of a discharge in it between the emitter and the ignition electrode, after which the starting heater is turned off, characterized in that after ignition The discharge in the first cathode delivers a plasma-forming gas to another cathode and ignites an ignition discharge in it. 3. The method of operation of the plasma source according to claim 2, characterized in that after the occurrence of ignition discharges in both cathodes, the ignition discharge in the first cathode is turned off. 4. The method of operation of a plasma source containing at least two hollow cathodes, including supplying a plasma-forming gas to one of the cathodes, its starting heating, ignition of a discharge in it between the emitter and the ignition electrode, after which the starting heater is turned off, characterized in that the plasma-forming gas served simultaneously in both cathodes and after starting warming up one of the cathodes simultaneously turn on the ignition discharge power sources of both cathodes. 5. The method of operation of the plasma source according to claim 4, characterized in that after the occurrence of ignition discharges in both cathodes, the ignition discharge in the first cathode is turned off.

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