JPH11210614A - Hollow cathode device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve power efficiency and to simplify a structure. SOLUTION: This hollow cathode device is provided with a cylindrical heating element 10 with an opening 101 to introduce operating gas G at one end, a bulkhead 56 with an orifice 561 installed at the other end of the cylindrical heating element 10, a hollow thermionic source 58 installed directly on the inner surface of the cylindrical heating element 10 to emit thermions, a heater power unit 60 to heat the cylindrical heating element 10 by energizing the cylindrical heating element 10, and a discharge unit 12 to plasmatize operating gas G in the cylindrical heating element 10 by discharging and to release the plasma P from the orifice 561. The heat loss can be reduced and the power efficiency can be improved by heating the thermionic source 58 directly by joule heat generated in the cylindrical heating element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow cathode apparatus used as an ion source for neutralizing ions of an ion engine mounted on an artificial satellite, for example.

[0002]

2. Description of the Related Art A hollow cathode device is used as an electron emission source in an ion source or a plasma generator. FIG. 3 is a schematic sectional view showing a conventional hollow cathode device. Hereinafter, description will be made based on this drawing.

[0003] A conventional hollow cathode device has a working gas G
A cylindrical body 52 having an opening 521 at one end for introducing
A heater 54 provided in contact with the outer peripheral surface of the cylindrical body 52
A partition wall 56 having an orifice 561 provided at the other end of the tubular body 52; a hollow thermoelectron source 58 provided in contact with the inner peripheral surface of the tubular body 52 to emit thermoelectrons;
The power supply 4 includes a heater power supply 60 that supplies electricity to the heater 4 and a discharge unit (not shown) that converts the operating gas G in the tubular body 52 into plasma by discharging and discharges the plasma P from the orifice 561. The heater 54 includes a heating wire 541 wound around the outer periphery of the tubular body 52, an insulating tube 542 for preventing a short circuit between the heating wires 541, a heating wire 541 and the insulating tube 54.
And a heater case 543 accommodating the two. When the thermoelectron source 58 is heated by the heater 54, thermoelectrons are generated from the thermoelectron source 58, so that the working gas G in the tubular body 52 can be easily discharged.

[0004]

However, the conventional hollow cathode device has the following problems because the heater 54 is used.

[0005] In the heater 54, the heat generated from the heating wire 541 is transmitted to the thermoelectron source 58 after passing through the insulating tube 542, the heater case 543, and the tubular body 52. Therefore, the rate at which the power supplied to the heater 54 is used to heat the thermoelectron source 58, that is, the power efficiency is low, and the temperature of the thermoelectron source 58 rises slowly.

[0006] Since the heater 54 is composed of the heating wire 541, the insulating tube 542, and the heater case 543, the heater 54 is complicated, and both the weight and the occupied volume are large.

[0007]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hollow cathode device which has good power efficiency, is simple in construction, and can be reduced in weight and size.

[0008]

According to the present invention, there is provided a hollow cathode device comprising: a tubular heating element having an opening for introducing a working gas at one end; and a partition having an orifice provided at the other end of the tubular heating element. A hollow thermoelectron source provided in contact with the inner peripheral surface of the tubular heating element and emitting thermoelectrons; and a heater power supply for generating heat by energizing the tubular heating element by energizing the tubular heating element. And a discharge unit that converts the working gas in the cylindrical heating element into plasma by discharge and discharges the plasma from the orifice. The material of the tubular heating element is most preferably graphite for the reason described below, but any material such as metal or ceramic may be used as long as it generates heat to a desired temperature by Joule heat.

[0009] Joule heat generated by the cylindrical heating element is directly transmitted to the thermionic source without any intervention. Therefore, the ratio of the power supplied to the cylindrical heating element used for heating the thermoelectron source, that is, the power efficiency is good, and the temperature of the thermoelectron source rises quickly. Further, since the heater which is conventionally required can be eliminated, the configuration can be simplified, and the weight and size can be reduced.

[0010]

FIG. 1 is a schematic sectional view showing a first embodiment of a hollow cathode device according to the present invention. Hereinafter, description will be made based on this drawing. However, the same parts as those in FIG.

The hollow cathode device of the present embodiment has a cylindrical heating element 10 having an opening 101 for introducing an operating gas G at one end, a partition wall 56 provided at the other end of the cylindrical heating element 10 and having an orifice 561. A hollow thermoelectron source 5 provided in contact with the inner peripheral surface of the cylindrical heating element and emitting thermoelectrons;
8, a heater power supply 60 for causing the tubular heating element 10 to generate heat by energizing the tubular heating element 10, an operating gas G in the tubular heating element 10 is turned into plasma by discharge, and the plasma P is discharged from the orifice 561. Discharge unit 1 to discharge
2 is provided.

The cylindrical heating element 10 is made of a general graphite material. The thermoelectron source 58 is made of a barium-based compound having a low thermoelectron emission work function, and has an overall cylindrical shape in which the outer peripheral surface is in contact with the inner peripheral surface of the cylindrical heating element 10. Partition wall 5
The orifice 6 and the orifice 561 are made of a material that can withstand high temperatures when the thermoelectron source 58 is heated, such as a molybdenum alloy or a tungsten alloy. In addition, the partition 56 and the orifice 561
May be made of a graphite material as in the case of the tubular heating element 10. The heater power supply 60 is a general DC power supply. The discharge unit 12 is connected in series to the cylindrical anode 121 facing the orifice 561 at a distance, a discharge power supply 122 for applying a voltage to the anode 121 and the cylindrical heating element 10, and a discharge power supply 122. And a discharge limiting resistor 123 for limiting overdischarge.

Next, the operation of the hollow cathode device of this embodiment will be described.

First, the cylindrical heating element 1 is heated by the heater power supply 60.
By passing a current to zero, the thermionic source 58 is heated to a temperature at which electrons can be emitted by Joule heat generated from the cylindrical heating element 10. Since the cylindrical heating element 10 is made of a graphite material, the heating temperature can be about 2500 ° C. or higher. After the thermoelectron source 58 is sufficiently heated, an appropriate flow rate of the working gas G is supplied into the cylindrical heating element 10. The operating gas G is generated by the cylindrical heating element 10 and the orifice 561.
The gas pressure suitable for arc discharge is maintained by closing the inside of the cylindrical heating element 10. Subsequently, the cylindrical heating element 10
By applying a voltage from a power supply 122 for discharge between the anode and the anode 121, an arc discharge is generated between the two and the working gas G is turned into plasma. At this time, by starting thermionic emission before generating the arc discharge, the initial electrons necessary for plasma generation are supplied abundantly, thereby facilitating plasma generation. The discharge limiting resistor 123 is
The amount of discharge current is limited to reduce the wear of the anode 121 and the cylindrical heating element 10 due to discharge. As the working gas G, hydrogen, nitrogen, argon, xenon, or the like, which has a low ionization voltage and easily generates plasma, is properly used depending on the intended use.

FIG. 2 is a schematic sectional view showing a second embodiment of the hollow cathode device according to the present invention. Hereinafter, description will be made based on this drawing. However, the same parts as those in FIG.

The hollow cathode device of the present embodiment uses a high-frequency discharge type discharge unit 14 instead of the DC discharge type discharge unit 12 (FIG. 1) in the first embodiment. The discharge unit 14 includes a high-frequency power source 141 that generates high-frequency power, a high-frequency line 142 that transmits the high-frequency power generated by the high-frequency power source 141, and the high-frequency power transmitted from the high-frequency line 142 as an electromagnetic wave. And a high-frequency introducing antenna 143 to be introduced into the inside.
The high-frequency electromagnetic field (for example, several hundred MHz to several GHz) introduced into the cylindrical heating element 10 causes thermoelectrons to vibrate. Plasma is generated when the vibrated thermoelectrons collide with atoms of the working gas G. An induction coil may be used instead of the high frequency introducing antenna 143.

It is needless to say that the present invention is not limited to the above embodiment. For example, in both the DC discharge type and the high-frequency discharge type, a magnetic field may be arranged in the plasma generation space for the purpose of increasing the plasma generation efficiency due to the discharge or reducing the wall loss of the generated plasma.

[0018]

According to the hollow cathode device of the present invention, the heat loss can be reduced by directly heating the thermionic source with the Joule heat generated by the cylindrical heating element, so that the power efficiency can be improved and the heat efficiency can be improved. Since the resistance can be reduced, the rate of temperature rise of the thermionic electron source can also be improved. In addition to this, the heater required in the related art can be dispensed with, so that the configuration can be simplified, thereby achieving a reduction in weight, size, and cost. In particular, it is possible to provide a hollow cathode device suitable for mounting on an artificial satellite that requires high power efficiency and a light weight and small size.

According to the hollow cathode device of the second aspect, since the tubular heating element is made of graphite, the following effects are obtained.
(1) Since graphite has excellent heat resistance, a large amount of thermoelectrons can be generated by heating at a higher temperature, thereby improving the electron generation efficiency and plasma generation efficiency of the thermoelectron source. Conventionally, the heating temperature is 1500 due to the problem of heat resistance of the heater itself.
Although limited to about 2000 ° C., heating to about 2500 ° C. or more is possible by using a graphite material. (2).
Graphite material is 1/5 of the conventional cylindrical molybdenum alloy material
Because of the following specific gravity, further weight reduction can be achieved.

According to the hollow cathode device of the third aspect, the partition walls are also made of the same graphite as the tubular heating element,
Since the partition and the tubular heating element can be integrated, the configuration can be further simplified.

According to the hollow cathode device of the fourth aspect, the thermoelectron source has a cylindrical shape in which the outer peripheral surface is in contact with the inner peripheral surface of the cylindrical heating element. More efficient transmission to the thermionic source.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a hollow cathode device according to the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the hollow cathode device according to the present invention.

FIG. 3 is a schematic sectional view showing a conventional hollow cathode device.

[Explanation of symbols]

Reference Signs List 10 cylindrical heating elements 12, 14 discharge section 56 partition wall 58
Thermionic source 60 Heater power supply 101 Opening 561 Orifice G Operating gas P Plasma

[Procedure amendment]

[Submission date] February 4, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Hollow cathode device

[Claims]

Also wherein said partition wall made of the same graphite as the tubular heating element, hollow cathode apparatus according to claim 1.

Claims3]Has an opening for introducing working gas at one end
A cylindrical heating element, and an orifice provided at the other end of the cylindrical heating element.
Contact the partition wall having the fiss and the inner peripheral surface of the cylindrical heating element
A hollow thermoelectron source for emitting thermoelectrons,
When the tubular heating element is energized, the tubular heating element is activated.
A heater power supply for heating, and the operating gas in the tubular heating element.
Of the plasma by discharge and the plasma
A discharge unit for discharging from the orifice,  The discharge unit is a high-frequency power source that generates high-frequency power
And transmit the high frequency power generated by this high frequency source
The high-frequency line and the high-frequency power transmitted from this high-frequency line
A high-frequency conductor for introducing a force into the cylindrical heating element as electromagnetic waves;
With input antennaTahoLow cathode device.

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow cathode apparatus used as an ion source for neutralizing ions of an ion engine mounted on an artificial satellite, for example.

[0002]

2. Description of the Related Art A hollow cathode device is used as an electron emission source in an ion source or a plasma generator. FIG. 3 is a schematic sectional view showing a conventional hollow cathode device. Hereinafter, description will be made based on this drawing.

[0003] A conventional hollow cathode device has a working gas G
A cylindrical body 52 having an opening 521 at one end for introducing
A heater 54 provided in contact with the outer peripheral surface of the cylindrical body 52
A partition 56 having an orifice 561 provided at the other end of the tubular body 52; a hollow thermoelectron source 58 provided in contact with the inner peripheral surface of the tubular body 52 to emit thermoelectrons;
The power supply 4 includes a heater power supply 60 that supplies electricity to the heater 4 and a discharge unit (not shown) that converts the operating gas G in the tubular body 52 into plasma by discharging and discharges the plasma P from the orifice 561. The heater 54 includes a heating wire 541 wound around the outer periphery of the tubular body 52, an insulating tube 542 for preventing a short circuit between the heating wires 541, a heating wire 541 and the insulating tube 54.
And a heater case 543 accommodating the two. When the thermoelectron source 58 is heated by the heater 54, thermoelectrons are generated from the thermoelectron source 58, so that the working gas G in the tubular body 52 can be easily discharged.

[0004]

However, the conventional hollow cathode device has the following problems because the heater 54 is used.

[0005] In the heater 54, the heat generated from the heating wire 541 is transmitted to the thermoelectron source 58 after passing through the insulating tube 542, the heater case 543, and the tubular body 52. Therefore, the rate at which the power supplied to the heater 54 is used to heat the thermoelectron source 58, that is, the power efficiency is low, and the temperature of the thermoelectron source 58 rises slowly.

[0006] Since the heater 54 is composed of the heating wire 541, the insulating tube 542, and the heater case 543, the heater 54 is complicated, and both the weight and the occupied volume are large.

[0007]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hollow cathode device which has good power efficiency, is simple in construction, and can be reduced in weight and size.

[0008]

According to the present invention, there is provided a hollow cathode device comprising: a tubular heating element having an opening for introducing a working gas at one end; and a partition having an orifice provided at the other end of the tubular heating element. A hollow thermoelectron source provided in contact with the inner peripheral surface of the tubular heating element and emitting thermoelectrons; and a heater power supply for generating heat by energizing the tubular heating element by energizing the tubular heating element. And a discharge unit that converts the working gas in the cylindrical heating element into plasma by discharge and discharges the plasma from the orifice. The material of the tubular heating element is most preferably graphite for the reason described below, but any material such as metal or ceramic may be used as long as it generates heat to a desired temperature by Joule heat.

[0009] Joule heat generated by the cylindrical heating element is directly transmitted to the thermionic source without any intervention. Therefore, the ratio of the power supplied to the cylindrical heating element used for heating the thermoelectron source, that is, the power efficiency is good, and the temperature of the thermoelectron source rises quickly. Further, since the heater which is conventionally required can be eliminated, the configuration can be simplified, and the weight and size can be reduced.

[0010]

FIG. 1 is a schematic sectional view showing a first embodiment of a hollow cathode device according to the present invention. Hereinafter, description will be made based on this drawing. However, the same parts as those in FIG.

The hollow cathode device of the present embodiment has a cylindrical heating element 10 having an opening 101 for introducing an operating gas G at one end, a partition wall 56 provided at the other end of the cylindrical heating element 10 and having an orifice 561. A hollow thermoelectron source 5 provided in contact with the inner peripheral surface of the cylindrical heating element and emitting thermoelectrons;
8, a heater power supply 60 for causing the tubular heating element 10 to generate heat by energizing the tubular heating element 10, an operating gas G in the tubular heating element 10 is turned into plasma by discharge, and the plasma P is discharged from the orifice 561. Discharge unit 1 to discharge
2 is provided.

The cylindrical heating element 10 is made of a general graphite material. The thermoelectron source 58 is made of a barium-based compound having a low thermoelectron emission work function, and has an overall cylindrical shape in which the outer peripheral surface is in contact with the inner peripheral surface of the cylindrical heating element 10. Partition wall 5
The orifice 6 and the orifice 561 are made of a material that can withstand high temperatures when the thermoelectron source 58 is heated, such as a molybdenum alloy or a tungsten alloy. In addition, the partition 56 and the orifice 561
May be made of a graphite material as in the case of the tubular heating element 10. The heater power supply 60 is a general DC power supply. The discharge unit 12 is connected in series to the cylindrical anode 121 facing the orifice 561 at a distance, a discharge power supply 122 for applying a voltage to the anode 121 and the cylindrical heating element 10, and a discharge power supply 122. And a discharge limiting resistor 123 for limiting overdischarge.

Next, the operation of the hollow cathode device of this embodiment will be described.

First, the cylindrical heating element 1 is heated by the heater power supply 60.
By passing a current to zero, the thermionic source 58 is heated to a temperature at which electrons can be emitted by Joule heat generated from the cylindrical heating element 10. Since the cylindrical heating element 10 is made of a graphite material, the heating temperature can be about 2500 ° C. or higher. After the thermoelectron source 58 is sufficiently heated, an appropriate flow rate of the working gas G is supplied into the cylindrical heating element 10. The operating gas G is generated by the cylindrical heating element 10 and the orifice 561.
The gas pressure suitable for arc discharge is maintained by closing the inside of the cylindrical heating element 10. Subsequently, the cylindrical heating element 10
By applying a voltage from a power supply 122 for discharge between the anode and the anode 121, an arc discharge is generated between the two and the working gas G is turned into plasma. At this time, by starting thermionic emission before generating the arc discharge, the initial electrons necessary for plasma generation are supplied abundantly, thereby facilitating plasma generation. The discharge limiting resistor 123 is
The amount of discharge current is limited to reduce the wear of the anode 121 and the cylindrical heating element 10 due to discharge. As the working gas G, hydrogen, nitrogen, argon, xenon, or the like, which has a low ionization voltage and easily generates plasma, is properly used depending on the intended use.

FIG. 2 is a schematic sectional view showing a second embodiment of the hollow cathode device according to the present invention. Hereinafter, description will be made based on this drawing. However, the same parts as those in FIG.

The hollow cathode device of the present embodiment uses a high-frequency discharge type discharge unit 14 instead of the DC discharge type discharge unit 12 (FIG. 1) in the first embodiment. The discharge unit 14 includes a high-frequency power source 141 that generates high-frequency power, a high-frequency line 142 that transmits the high-frequency power generated by the high-frequency power source 141, and the high-frequency power transmitted from the high-frequency line 142 as an electromagnetic wave. And a high-frequency introducing antenna 143 to be introduced into the inside.
The high-frequency electromagnetic field (for example, several hundred MHz to several GHz) introduced into the cylindrical heating element 10 causes thermoelectrons to vibrate. Plasma is generated when the vibrated thermoelectrons collide with atoms of the working gas G. An induction coil may be used instead of the high frequency introducing antenna 143.

It is needless to say that the present invention is not limited to the above embodiment. For example, in both the DC discharge type and the high-frequency discharge type, a magnetic field may be arranged in the plasma generation space for the purpose of increasing the plasma generation efficiency due to the discharge or reducing the wall loss of the generated plasma.

[0018]

According to the hollow cathode device of the present invention, the heat loss can be reduced by directly heating the thermionic source with the Joule heat generated by the cylindrical heating element, so that the power efficiency can be improved and the heat efficiency can be improved. Since the resistance can be reduced, the rate of temperature rise of the thermionic electron source can also be improved. In addition to this, the heater required in the related art can be dispensed with, so that the configuration can be simplified, thereby achieving a reduction in weight, size, and cost. In particular, it is possible to provide a hollow cathode device suitable for mounting on an artificial satellite that requires high power efficiency and a light weight and small size.

According to the hollow cathode device of the first aspect , since the tubular heating element is made of graphite, the following effects can be obtained.
(1) Since graphite has excellent heat resistance, a large amount of thermoelectrons can be generated by heating at a higher temperature, thereby improving the electron generation efficiency and plasma generation efficiency of the thermoelectron source. Conventionally, the heating temperature is 1500 due to the problem of heat resistance of the heater itself.
Although limited to about 2000 ° C., heating to about 2500 ° C. or more is possible by using a graphite material. (2).
Graphite material is 1/5 of the conventional cylindrical molybdenum alloy material
Because of the following specific gravity, further weight reduction can be achieved.

According to the hollow cathode device of the second aspect , the partition wall is also made of the same graphite as the tubular heating element,
Since the partition and the tubular heating element can be integrated, the configuration can be further simplified.

According to the hollow cathode device of the third aspect , a high-frequency supply source for generating high-frequency power,
High-frequency line that transmits high-frequency power generated by a wave source
And the high-frequency power transmitted from this high-frequency line
As a high-frequency antenna to be introduced into a cylindrical heating element
Since the discharge section is composed more,
The vibrator can be oscillated to generate a plasma.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a hollow cathode device according to the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the hollow cathode device according to the present invention.

FIG. 3 is a schematic sectional view showing a conventional hollow cathode device.

[Description of Signs] 10 Cylindrical heating element 12, 14 Discharge unit 56 Partition wall 58 Thermoelectron source 60 Heater power supply 101 Opening 561 Orifice G Working gas P Plasma

Claims (6)

[Claims] 1. A cylindrical heating element having an opening for introducing an operating gas at one end, a partition provided at the other end of the cylindrical heating element and having an orifice, and contacting an inner peripheral surface of the cylindrical heating element. A hollow thermoelectron source configured to emit thermoelectrons, a heater power supply for heating the cylindrical heating element by energizing the cylindrical heating element, and discharging the operating gas in the cylindrical heating element. And a discharge unit for generating plasma from the orifice and discharging the plasma from the orifice. 2. The hollow cathode device according to claim 1, wherein said tubular heating element is made of graphite. 3. The hollow cathode device according to claim 2, wherein said partition wall is also made of the same graphite as said tubular heating element. 4. The hollow cathode device according to claim 1, wherein the thermoelectron source has a cylindrical shape whose outer peripheral surface is in contact with the inner peripheral surface of the cylindrical heating element. 5. The discharge unit includes a cylindrical anode opposed to the orifice at a distance, a discharge power supply for applying a voltage to the anode and the cylindrical heating element, and a discharge power supply connected in series with the discharge power supply. 2. The hollow cathode device according to claim 1, further comprising: a discharge limiting resistor that is connected and limits overdischarge. 6. The high-frequency power source for generating high-frequency power, a high-frequency line for transmitting high-frequency power generated by the high-frequency power source, and the high-frequency power transmitted from the high-frequency line as electromagnetic waves. The hollow cathode device according to claim 1, further comprising: a high-frequency introducing antenna for introducing into the heating element.