JP2011074887A - Hollow cathode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow cathode for a spacecraft, facilitating starting (ignition) of discharge. <P>SOLUTION: Members have distal ends opposed to a keeper electrode plate 6. The distal ends have a nanocarbon fine projection group structure, a fine projection (group) structure by a microfabrication technology or a composite structure with an electric conductor and an electric insulator located adjacently to each other, or are composed of carbon material with a nanocarbon structure spontaneously formed and maintained by action such as discharge or carbon material having excellent thermionic emission characteristics. The members are mounted downstream of an orifice plate 4 as discharge initiation promoting plates A31, B32, C33, D34, E35. Or, the orifice plate 4 itself is so formed that the distal end opposed to the keeper electrode plate 6 is made to have the fine projection (group) structure or the composite structure with the electric conductor and the electric insulator located adjacently to each other or which is composed of carbon material with the nanocarbon structure spontaneously formed by action such as discharge or carbon material having excellent thermionic emission characteristics. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hollow cathode mounted on a spacecraft such as an artificial satellite, and more particularly to a spacecraft hollow cathode that facilitates the start (ignition) of discharge.

  There is a hollow cathode as a long-life electron source mounted on space structures such as satellites and space stations. For space applications, such as ion engines and hall thrusters used for orbit control and maintenance of the north-south position of satellites, etc. There are plasma contactors and the like used for preventing electrification of electron sources of electric propulsion devices, space stations and the like.

  The main part of such a hollow cathode is usually configured as shown in FIG. FIG. 9 is a diagram showing a partial cross-sectional view of the hollow cathode disclosed in Patent Document 1 and Patent Document 2 serving as the foundation (prior art) of the present invention, and is denoted by reference numeral 1 in the drawing. The member shown is a cathode insert that is the first electron emission source, and the cathode insert 1 has a cylindrical cavity 2 formed at the center thereof. The cathode insert 1 is made of porous tungsten impregnated with barium oxide, and the work function of the surface facing the cavity 2 after activation is lowered to about 2 eV. The cathode insert 1 is inserted into a cylindrical cathode tube 3 and pressed against an orifice plate 4 positioned at the tip of the cathode tube 3 by a cathode insert support portion 5. A keeper electrode plate 6 formed in a disk shape is disposed on the front surface of the orifice plate 4. For example, a hole-shaped orifice 7 having a diameter of about 0.3 to 1.5 mm is opened at the center of the orifice plate 4. A keeper hole 8 having a diameter of about 2 to 8 mm faces the orifice 7 on the keeper electrode plate 6. Is open.

  A heater 9 embedded in the ceramic sprayed layer is disposed outside the cathode tube 3, and a heat shield 10 surrounds the heater 9. The keeper electrode plate 6 is fixed by a keeper electrode support portion insulating cylinder 11, and the keeper electrode support portion insulating cylinder 11 is covered with a sputter shield 12. The cathode tube 3 and the keeper electrode support part insulating cylinder 11 are fixed to a base plate 13. In addition to these, the base plate 13 is also fixed with three current introduction terminals 14, 15, 16 for supplying current to the base plate 13, the heater 9 and the keeper electrode plate 6, and a gas introduction system 17. The heater 9 is connected to the current introduction terminal 15 and the cathode tube 3, the keeper electrode plate 6 is connected to the current introduction terminal 16, and the base plate 13 is connected to the current introduction terminal 14. The base plate 13 is usually fixed to the center of the canopy of the discharge vessel 18 and is kept at the cathode potential of the discharge power source. The discharge vessel 18 serves as an anode for the discharge power source.

  Conventionally, in order to operate such a hollow cathode, the following ignition procedure is required as an example. First, the temperature of the cathode insert 1 is raised to about 1000 ° C. by heating the heater 9. Next, when a propellant (for example, xenon) gas is introduced from the gas introduction system 17 into the cavity 2 of the cathode insert 1 with a voltage of +100 V or more applied to the keeper electrode plate 6, a gap between the cathode insert 1 and the keeper electrode plate 6 is obtained. Insulation breakdown occurs, and primary electrons emitted from the cathode insert 1 are accelerated. The primary electrons collide with the xenon gas in the cavity 2, and ionized plasma (internal plasma 20) shown in FIG. 10 is generated in the cavity 2 on the orifice plate 4 side. Here, the voltage notation will be supplemented. In this specification, the cathode potential which is the potential of the cathode insert 1, the cathode tube 3, the orifice plate 4, the cathode insert support 5 and the base plate 13 is used as a reference potential, and the voltage unless otherwise indicated is a potential difference with respect to the cathode potential. .

  When a discharge voltage +20 to +60 V is applied to the discharge power supply anode portion of the discharge vessel 18 in the above state, secondary electrons are newly extracted from the internal plasma 20 and collide with the xenon gas in the discharge vessel 18 together with the primary electrons. Two other ionized plasmas (keeper plasma 21 and external plasma 22) are generated. The keeper plasma 21 serves to connect the internal plasma 20 and the external plasma 22, and is formed in the discharge vessel 18 from the orifice 7 of the orifice plate 4 through the keeper hole 8 of the keeper electrode plate 6. Thus, the state in which the internal plasma 20, the keeper plasma 21, and the external plasma 22 are formed is a steady operation state of the hollow cathode. After shifting to the steady operation, the heater heating is normally stopped, the keeper power source is changed from constant voltage control to constant current control (about 0.5 to 2 A), and the voltage applied to the keeper electrode plate 6 is +8. It drops to about + 25V.

  Such a hollow cathode has a problem that it is necessary to apply a voltage of +100 V or more to the keeper electrode plate 6 in the ignition procedure. In other words, in the normal operation state of the hollow cathode, the voltage of the keeper electrode plate 6 is about +25 V at most, whereas in the ignition stage before the steady operation, the gap between the cathode insert 1 and the keeper electrode plate 6 is sufficient. In order to cause dielectric breakdown, a significantly higher voltage must be applied to the keeper electrode plate 6 as compared with the steady operation.

  One of the problems due to having to apply a significantly higher voltage to the keeper electrode plate 6 in the ignition procedure than during steady operation is an increase in the weight and volume of the keeper electrode power supply. That is, in order for the keeper electrode power supply to output a voltage of +100 V or more, an additional circuit for applying a high voltage is required, which increases the weight and volume of the keeper electrode power supply. In space use, the weight and volume that can be used are severely limited, so an increase in the size of the power supply is not desirable. Furthermore, the internal structure of the keeper electrode power supply is complicated by the increase in the voltage of the keeper electrode plate 6, and a voltage of +100 V or more is applied to each part along the wiring connecting the keeper electrode plate 6 from the keeper electrode power supply. Therefore, it may cause problems such as abnormal dielectric breakdown.

  Another problem due to the fact that a significantly higher voltage must be applied to the keeper electrode plate 6 in the ignition procedure as compared with that during steady operation is that a high voltage of +100 V or higher causes a gap between the cathode insert 1 and the keeper electrode plate 6. If the dielectric breakdown occurs, the cathode insert 1 or the orifice plate 4 or the keeper electrode plate 6 may be damaged. For example, on page 5 of Non-Patent Document 1, a minute solid is released from the vicinity of the orifice 7 when a dielectric breakdown occurs when a high voltage of +100 V or higher is applied to the keeper electrode plate 6 in the ignition procedure. It has been reported that damage may have occurred to the cathode insert 1 or the orifice plate 4 or the keeper electrode plate 6. Such damage can shorten the life of the hollow cathode and degrade its operating performance. Further, when a high voltage of +100 V or higher is continuously applied to the keeper electrode plate 6 in the ignition procedure, particularly when the orifice plate 4 is made of a carbon-based material, the time required for ignition and the load on the heater 9 The tendency to increase is also confirmed.

  In addition to Patent Documents 1 and 2, which are the basis of the present invention, as well-known documents regarding hollow cathodes, in terms of lowering the voltage, Patent Document 3 improves the shape of the cathode insert to operate even in a large current operation. A hollow cathode capable of reducing the voltage is shown, and regarding the suppression of abnormal discharge occurrence, Patent Document 4 discloses a hollow cathode that can stabilize the discharge state by covering the surface of the cathode insert. There is. However, in these documents, low voltage or suppression of abnormal discharge occurrence during steady operation of the hollow cathode is shown, and the present invention dealing with the problem at the time of ignition is based on problems, means, and a specific structure. Is different.

JP 2000-161201 A (Page 7, FIG. 7) JP 2004-169606 A (page 10, FIG. 7) JP 2000-130316 A JP 2004-115887 A Hayakawa, Y. et al, "Graphite Orificed Hollow Cathodes for Xenon Ion Thrusters," 43rd AIAA Joint Propulsion Conference, AIAA paper 2007-5173, July 2007. (page 5)

  The conventional hollow cathode has a problem to be solved in that it is necessary to apply a high voltage of +100 V or more to the keeper electrode plate in the ignition procedure before shifting to the steady operation.

  Accordingly, an object of the present invention is to reduce the voltage applied to the keeper electrode plate in the ignition procedure, thereby reducing the weight and volume of the power supply for the keeper electrode and preventing the power supply structure from becoming complicated. Due to the application of high voltage during ignition, such as preventing the life of the cathode insert or orifice plate or keeper electrode plate from damaging and preventing deterioration of discharge performance. An object of the present invention is to provide a hollow cathode capable of solving various problems.

  To achieve the above object, a hollow cathode according to the present invention has a hollow cathode tube having a heater, an orifice plate having an orifice attached to the tip of the cathode tube, and a keeper hole facing the orifice plate. In a hollow cathode having a keeper electrode plate, a cathode insert inserted into the cathode tube and having a hollow portion, and a gas introduction system for introducing a working gas into the cathode tube, discharge starts downstream of the orifice plate. A discharge start promoting plate that facilitates (ignition) is provided.

  According to this hollow cathode, since the discharge start acceleration plate that facilitates the start (ignition) of discharge is provided downstream of the orifice plate, the voltage applied to the keeper electrode plate in the hollow cathode ignition procedure is set. Thus, it is possible to reduce to +30 V or less, which is equivalent to that during the steady operation of the hollow cathode. That is, the keeper electrode plate voltage of +100 V or more required in the conventional hollow cathode ignition procedure can be greatly reduced.

  In the hollow cathode, as the discharge initiation promoting plate attached to the downstream side of the orifice plate, there is a carbon structural material containing nanocarbon such as carbon nanotubes. Since nanocarbon has nanometer-scale fine protrusions, the carbon structure material reaches a high temperature of about 1000 ° C due to the propagation of heat from the heater and emits thermoelectrons, and the electric field concentration at the tip of the fine protrusions. Electron emission is promoted by the effect and the heat concentration effect, and discharge can be started even when the voltage applied to the keeper electrode plate is a low value of about +30 V or less. In the conventional hollow cathode, only the mechanism in which the orifice plate becomes hot due to the propagation of heat from the heater and emits thermoelectrons is used, but in the present invention, a mechanism for inducing the electric field concentration effect and the heat concentration effect in addition thereto. This is the difference from the conventional hollow cathode.

  In the hollow cathode, as the discharge start promoting plate attached to the downstream side of the orifice plate, there is also a structural material having one or a plurality of nanometer-class micro protrusions by a microfabrication technique. Due to the nanometer-scale minute projections, discharge can be started even if the voltage applied to the keeper electrode plate is as low as about +30 V or less due to the same effect as described above.

  In the hollow cathode, as the discharge initiation promoting plate attached to the downstream side of the orifice plate, there is a structural material having a structure in which an electrical conductor and an electrical insulator are adjacent to each other. When the electrical insulator is charged up due to secondary electron emission and other reasons, an electric field concentration occurs at the boundary between the electrical conductor and the electrical insulator, and a strong electric field is formed. Is released. In addition to thermionic emission due to the high temperature of the structural material due to the propagation of heat from the heater, this field emission electron initiates discharge even when the voltage applied to the keeper electrode plate is as low as +30 V or less. It becomes possible to do.

  In this hollow cathode, a structural material made of a carbon-based material can be used as the discharge start promoting plate attached to the downstream side of the orifice plate. Due to the sustained action such as discharge during hollow cathode operation, nanocarbon structures such as carbon nanotubes are spontaneously generated and maintained on the discharge start promotion plate made of carbon-based material. In addition to the discharge initiation promoting plate reaching a high temperature of about 1000 ° C. due to propagation and emitting thermoelectrons, the electron emission is promoted by the electric field concentration effect and the heat concentration effect at the tip of the nanocarbon structure, and the keeper electrode plate Even if the applied voltage is a low value of about +30 V or less, the discharge can be started.

  In this hollow cathode, as the discharge start promoting plate attached to the downstream side of the orifice plate, a structural material made of a material having excellent thermionic emission characteristics can be applied. As an example, in this hollow cathode, when a discharge initiation promoting plate made of high-density carbon is applied, even when the voltage applied to the keeper electrode plate is +30 V or less, discharge is started by electron emission from the orifice plate, Experiments have confirmed that the hollow cathode shifts to steady operation. FIG. 8 shows an example of an experimental result obtained by measuring the electron emission characteristics of the discharge initiation promoting plate made of high-density carbon. When there is a discharge initiation promoting plate, there is no discharge initiation promoting plate (metal orifice plate). It can be seen that high electron emission performance can be obtained even in a low temperature region.

  In this hollow cathode, the shape of the discharge start promoting plate attached to the downstream side of the orifice plate may not be a plate shape. That is, it may be in the form of a mesh or a lattice. Furthermore, the orifice plate may be impregnated with a discharge initiation promoting material, the surface of the orifice plate may be coated with a discharge initiation promoting material, or one or more protruding materials may be formed on the surface of the orifice plate. good.

  In this hollow cathode, the functions described above may work in duplicate as the configuration of the discharge start promoting plate attached to the downstream side of the orifice plate. That is, whether the discharge initiation promoting plate has a nano-carbon structure, a micro-projection by a microfabrication technique, an electrical conductor and an electrical insulator are adjacent to each other, or is made of a carbon-based material. A plurality of functions may overlap.

  In this hollow cathode, there is no particular limitation on the size of the discharge start promoting plate that is beaten to the downstream side of the orifice plate. That is, the size of the discharge start promoting plate may be the same as the orifice plate, may be larger than the orifice plate, or may be smaller than the orifice plate. Further, the size of the discharge start promoting opening vacated in the discharge promoting plate corresponding to the orifice may be the same as the orifice, may be larger than the orifice, or smaller than the orifice.

  In this hollow cathode, an appropriate material may be selected for the orifice plate so that the orifice plate itself serves as the discharge start promoting plate. That is, the orifice plate itself has a nanocarbon structure, a microprojection (group) structure by microfabrication technology, an electrical conductor and an electrical insulator adjacent to each other, or is made of a carbon-based material. Or may have one or a plurality of structures. The present invention can be implemented with various modifications without departing from the gist of the present invention.

  According to the hollow cathode of the present invention, a hollow cathode tube having a heater, an orifice plate having an orifice attached to the tip of the cathode tube, a keeper electrode plate having a keeper hole facing the orifice plate, In a holo cathode having a cathode insert inserted into the cathode tube and having a hollow portion and a gas introduction system for introducing a working gas into the cathode tube, discharge start (ignition) can be easily performed on the downstream side of the orifice plate. By providing the discharge start promoting plate, discharge can be started even when the voltage applied to the keeper electrode plate is a low value of about +30 V or less. Therefore, according to this hollow cathode, by reducing the voltage applied to the keeper electrode plate at the time of ignition, the weight and volume of the power supply for the keeper electrode are reduced, the power supply structure is simplified, and abnormalities in the power supply and in the wiring section are reduced. Insulation breakdown can be prevented, and in addition, high voltage application at the start of discharge, such as a reduction in life and deterioration of discharge performance, can be prevented by preventing damage to the cathode insert or orifice plate or keeper electrode plate at the start of discharge. Various problems caused by it can be solved. With these effects, it becomes possible to design and manufacture a hollow cathode suitable for space use that requires miniaturization, weight reduction, simplification, high reliability, long life, and high performance of equipment.

It is explanatory drawing which shows the hollow cathode in connection with 1st Example of this invention. It is explanatory drawing which shows the hollow cathode concerning 2nd Example of this invention. It is explanatory drawing which shows the hollow cathode concerning 3rd Example of this invention. It is principal part sectional explanatory drawing which shows the hollow cathode in connection with 4th Example of this invention. It is explanatory drawing which shows the growth effect | action of the nanocarbon in 4th Example of FIG. It is principal part cross-section explanatory drawing which shows the hollow cathode concerning 5th Example of this invention. It is principal part explanatory drawing which shows the hollow cathode in connection with 6th Example of this invention. It is a figure which shows the experimental result which measured the thermoelectron emission characteristic from a discharge start promotion board. It is sectional drawing which cuts off and shows the conventional hollow cathode partially. It is a schematic diagram of the ionized plasma formed in the vicinity of a hollow cathode. It is principal part cross-sectional explanatory drawing which shows the conventional hollow cathode.

  The present invention can be implemented by appropriately selecting the structure, shape, material, and the like of the discharge start promoting plate attached downstream of the orifice plate of the conventional hollow cathode. Embodiments of a hollow cathode according to the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory view showing a hollow cathode 100 according to the first embodiment of the present invention. 1A is a cross-sectional view of the main part, and FIG. 1B is an enlarged view of the A part. Further, in order to clarify the features of the present invention, FIG. 11 is shown with reference to a cross-sectional explanatory diagram showing a part of the conventional hollow cathode shown in FIG. In FIG. 1 and FIG. 11, the same reference numerals are used for the same parts as those of the conventional hollow cathode shown in FIG.

  The hollow cathode according to the first embodiment shown in FIG. 1 is provided with a discharge start promoting plate A31 on the downstream side of the orifice plate 4 as seen in the plasma flow direction as compared with the conventional hollow cathode shown in FIG. Is different in that. The discharge start promoting plate A31 is a microprojection group structure containing nanocarbons such as carbon nanotubes, and has fine projections with a diameter of nanometer class. Therefore, heat is propagated from the heater 9 to the discharge start promoting plate A31. In addition to the electrons being emitted from the tips of the fine projections at high temperatures, electric field concentration and heat concentration occur at the tips of the fine projections, and the amount of emitted electrons is amplified. As a result, even when the voltage applied to the keeper electrode plate 6 is low, the hollow cathode can be ignited. In FIG. 1, the nanocarbon structure of the discharge initiation promoting plate A31 is typically a comb-like upright form, but the nanocarbon structure may be a form in which carbon nanotubes are randomly entangled. In FIG. 1, the size of the discharge start promoting plate opening 41 is larger than that of the orifice 7. However, in this embodiment and each of the embodiments described later, the size relationship between the discharge start promoting plate opening 41 and the orifice 7 is shown. There are no restrictions. The size of the discharge start promoting plate A31 shown in FIG. 1 is the same as that of the orifice plate 4. However, in this embodiment and each of the embodiments described later, the size relationship between the discharge start promoting plate and the orifice plate 4 is large. There is no particular restriction.

  As shown in FIG. 1B, as a method for fixing the carbon nanotubes 31a to the orifice plate 4, for example, the carbon nanotubes 31a are arranged in a comb-like upright form on a support plate 31b coated with an adhesive, or carbon nanotubes. It can be considered that 31a is attached in a disorderly entangled form. The carbon nanotubes 31a may be grown on the orifice plate 4 by a method such as chemical vapor deposition.

  FIG. 2 is an explanatory view showing a hollow cathode according to the second embodiment of the present invention. 2A is a cross-sectional view of the main part, and FIG. 2B is an enlarged view of the B part. In the hollow cathode shown in FIG. 2, the same reference numerals are used for the same parts as those in the first embodiment shown in FIG.

  The second embodiment shown in FIG. 2 differs from the conventional hollow cathode shown in FIG. 11 in that a discharge start promoting plate B32 is attached on the downstream side of the orifice plate 4. The discharge start promoting plate B32 has a microprojection (group) structure formed by a microfabrication technique, and the amount of electron emission from the discharge start promoting plate B32 is amplified as in the first embodiment. FIG. 2 shows the discharge start promoting plate B32 in which pyramidal microprojections are concentrically arranged, but the shape of these microprojections is not particularly limited.

  FIG. 3 is an explanatory view showing a hollow cathode according to a third embodiment of the present invention. 3A is a cross-sectional view of the main part, and FIG. 3B is an enlarged view of the C part. In the hollow cathode shown in FIG. 3, the same reference numerals are used for the same parts as those in the first embodiment shown in FIG.

  The third embodiment shown in FIG. 3 is different from the conventional hollow cathode shown in FIG. 11 in that a discharge start promoting plate C33 is attached to the downstream side of the orifice plate 4. The discharge start promoting plate C33 has an electric conductor portion 33a (for example, a refractory metal or carbon-based material such as tungsten or tantalum) and an electric insulator portion 33b (for example, a ceramic-based material such as alumina or zirconia). It has an adjacent structure, and the amount of electron emission from the discharge start promoting plate C33 is amplified by the electric field concentration at the boundary between the two. FIG. 3 shows an example of the discharge start promoting plate C33, but there is no particular limitation on the arrangement relationship and shape between the electric conductor portion 33a and the electric insulator portion 33b.

  FIG. 4 is a cross-sectional explanatory view of an essential part showing a hollow cathode according to a fourth embodiment of the present invention. In the hollow cathode shown in FIG. 4, the same reference numerals are used for the same parts as those in the first embodiment shown in FIG.

  The fourth embodiment shown in FIG. 4 differs from the conventional hollow cathode shown in FIG. 11 in that a discharge start promoting plate D34 is attached on the downstream side of the orifice plate 4. The discharge start promoting plate D34 is made of a carbon-based material, such as graphite or a carbon-carbon composite material, and a nanocarbon structure is spontaneously formed on the discharge start promoting plate D34 by an action such as discharge of a hollow cathode. Thus, the amount of electron emission from the discharge start promoting plate D34 is amplified as in the first embodiment.

  FIG. 5 is a diagram showing the formation of this spontaneous nanocarbon structure. By continuing the hollow cathode discharge or the like for a certain period of time, a discharge initiation promoting plate is obtained by an action similar to nanocarbon generation by the arc discharge method. This shows how the nanocarbon structure is spontaneously formed and maintained on D34.

  FIG. 6 is a cross-sectional explanatory view of an essential part showing a hollow cathode according to a fifth embodiment of the present invention. In the hollow cathode shown in FIG. 6, the same reference numerals are used for the same parts as those in the first embodiment shown in FIG.

  The fifth embodiment shown in FIG. 6 is different from the conventional hollow cathode shown in FIG. 11 in that a discharge start promoting plate E35 is attached on the downstream side of the orifice plate 4. The discharge initiation promoting plate E35 is made of a carbon-based material having excellent thermionic emission characteristics, such as graphite or a carbon-carbon composite material, and the electron emission from the discharge initiation promoting plate E35 due to the high electron emission characteristics of the material. The amount is amplified.

  FIG. 7 is a cross-sectional explanatory view of an essential part showing a hollow cathode according to a sixth embodiment of the present invention. In the hollow cathode shown in FIG. 7, the same parts as those in the first embodiment shown in FIG.

  The sixth embodiment shown in FIG. 7 is different from the hollow cathode according to the first to fifth embodiments in that the improved orifice plate 42 has a discharge start promoting function. That is, the improved orifice plate 42 has a nanocarbon microprojection group structure on its downstream surface (a surface facing the keeper electrode plate 6), or a microprojection (group) structure by microfabrication technology. Whether the conductor and the electrical insulator have a composite structure adjacent to each other, or are composed of a carbon-based material in which a nanocarbon structure is spontaneously generated and maintained, or a carbon-based material having excellent thermal electron emission characteristics. One or a combination of these has a structure, and the improved orifice plate 42 itself has a discharge start promoting function.

  The hollow cathode according to the present invention has the characteristics that the structure of the power source necessary for the hollow cathode operation is simplified, reduced in weight, reduced in size, prevented from abnormal dielectric breakdown, and has a longer life. It is expected to be applied to the space industry where miniaturization, weight reduction and simplification are required and high reliability is required. Applications in the space industry field include plasma generators and ion beam neutralizers for ion engines, electron emitters for hall thrusters, hollow cathode thrusters, electron emitters for conductive tether systems, satellites and space stations. A charge controller such as the above can be considered.

  It can also be used as a plasma generation source for the terrestrial industry, and has many applications such as a plasma generation device and ion beam neutralization device for sputtering ion sources, a plasma generation device for ion etching equipment, and a hollow cathode lamp. Conceivable.

DESCRIPTION OF SYMBOLS 1 Cathode insert 2 Cavity part 3 Cathode tube 4 Orifice plate 5 Cathode insert support part 6 Keeper electrode plate 7 Orifice 8 Keeper hole 9 Heater 10 Heat shield 11 Keeper electrode support part insulation cylinder 12 Sputter shield 13 Base plates 14, 15, 16 Current introduction terminal 17 Gas introduction system 18 Discharge vessel 20 Internal plasma 21 Keeper plasma 22 External plasma 31 Discharge start acceleration plate A
32 Discharge start acceleration plate B
33 Discharge start acceleration plate C
33a Electrical conductor portion 33b of the discharge start promoting plate C Electrical insulator portion 34 of the discharge start promoting plate C Discharge start promoting plate D
35 Discharge start promotion plate E
41 Opening 42 of Discharge Start Promotion Plates A to D Improved Orifice Plate

Claims (9)

A hollow cathode tube having a heater, an orifice plate having an orifice attached to the tip of the cathode tube, a keeper electrode plate having a keeper hole facing the orifice plate, and a hollow portion inserted into the cathode tube. In a hollow cathode having a cathode insert having a gas introduction system for introducing a working gas into the cathode tube,
A hollow cathode, wherein a discharge start promoting plate for facilitating discharge start (ignition) is provided at a downstream portion of the orifice plate.   2. The hollow cathode according to claim 1, wherein the discharge start promoting plate has a microprojection group structure made of nanocarbon such as carbon nanotubes.   The hollow cathode according to claim 1, wherein the discharge start promoting plate is composed of a plurality of microprojection group structures formed by a micromachining technique.   2. The hollow cathode according to claim 1, wherein the discharge initiation promoting plate is a composite plate having a structure in which a plurality of electrical conductors and a plurality of electrical insulators are adjacent to each other.   The hollow cathode according to claim 1, wherein the discharge initiation promoting plate is a plate made of a carbon-based material in which a nanocarbon structure is spontaneously generated and maintained.   The hollow cathode according to claim 1, wherein the discharge initiation promoting plate is a plate formed of a carbon-based material having excellent thermionic emission characteristics.   The hollow cathode according to claim 1, wherein the discharge start promoting plate is a plate having a mesh structure or a lattice structure. A hollow cathode tube having a heater, an orifice plate having an orifice attached to the tip of the cathode tube, a keeper electrode plate having a keeper hole facing the orifice plate, and a hollow portion inserted into the cathode tube. In a hollow cathode having a cathode insert having a gas introduction system for introducing a working gas into the cathode tube,
8. The hollow cathode according to claim 2, wherein the orifice plate itself has one or more of the functions of the discharge start promoting plate according to claim 2.   9. The hollow cathode according to claim 1, wherein it is not necessary to apply a high voltage of +100 V or more to the keeper electrode plate at the time of ignition.

Images