JPS5853460B2 - Hollow cathode discharge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a hollow cathode discharge device that facilitates discharge starting.

Technical Background of the Invention As is well known, a hollow cathode discharge device generates plasma by causing arc discharge between a hollow cathode (hollow cathode) placed in a discharge chamber and an anode. It is widely used as a plasma generator.

Such a hollow cathode discharge device is usually constructed as shown in FIG.

That is, a cylindrical hollow cathode 1 made of a material that easily emits thermoelectrons is provided in a discharge chamber (not shown), and an anode 2 is provided coaxially with the hollow cathode 1 and facing the hollow cathode 1 at a distance. ing.

A solenoid-shaped heater 3 is installed outside the hollow cathode 1 without contacting the hollow cathode 1, and the input end of the heater 3 is connected to a heating power source 5 via a lead wire 4. ing.

Further, a heat shield cylinder 6 is installed outside the heater 3, and the heat shield cylinder 6 is connected to the hollow cathode 1 through an insulating ring 7 fixed to the anode 2 side end of the hollow cathode 1. It is supported by cathode 1.

Further, a disk-shaped starting electrode 9 having a small diameter hole 8 in the center is fixed to the end surface of the insulating ring 7 on the anode 2 side through a part of the heat shield cylinder 6.

Inside the twisted hollow cathode 1, an internal electrode 11 is installed in a relationship opposite to the starting electrode 9.

This internal electrode 11 is electrically connected to the hollow cathode 1 .

Then, a discharge limiting resistor 13A and a switch 14 are connected between the conductive cylinder 12 fitted on the side opposite to the anode of the hollow cathode 10 and the heat shield cylinder 6 electrically connected to the starting electrode 9. A power source 15 is connected.

Further, an arc power source 18 is connected between the internal electrode 11 and the anode 2 via a current limiting resistor 16 and a switch 17.

By the way, 19 in the figure shows the gas supply pipe.

In a hollow cathode discharge device having such a configuration, at startup, the heater 3 is first energized to heat the hollow cathode 1 and cause the hollow cathode 1 to emit thermoelectrons.

When the hollow cathode 1 is sufficiently heated, a working gas necessary for discharge is supplied into the hollow cathode 1 through the gas supply pipe 19, and at the same time, the switch 14 is turned on to close the starting electrode 9.
A starting voltage is applied between the internal electrode 11 and the internal electrode 11 to cause a glow discharge between the two electrodes.

When the amount of plasma required to start the arc discharge between the hollow cathode 1 and the anode 2 is generated in the hollow cathode 1 by this glow discharge, the switch 17 is turned on and the hollow cathode 1 and the anode 2 are connected. An arc starting voltage is applied during this period, thereby causing a transition to arc discharge.

Once the arc discharge starts, the arc discharge continues even if the switch 14 is opened and the starting voltage is removed.

FIG. 2 is also a sectional view showing a conventional hollow cathode discharge device, and the same parts as in FIG. 1 are designated by the same symbols.

In this hollow cathode discharge device, glow discharge is facilitated by fixing an electrode member 20 that easily emits thermoelectrons, that is, has a small work function, to the side of the internal electrode 11 facing the starting electrode 9. .

Problems with the Background Art However, these discharge devices have the following problems.

That is, in the conventional device, a method is adopted in which thermionic electrons are emitted from the hollow cathode 1 in order to create a trigger for starting, and for this purpose, a solenoid-shaped heater 3 is installed outside the hollow cathode 1. I try to do that.

With this configuration, there is a problem that when the heater 3 is energized, the heater 3 tends to undergo thermal deformation and come into contact with the hollow cathode 1 or the outer heat shield tube 6, and is likely to break down.

In addition, if sufficient space is provided between the heater 3, the hollow cathode 1A, and the heat shield tube 6 to prevent contact,
There was an unavoidable problem as the device became larger.

Furthermore, due to the complicated structure, maintenance and inspection were also difficult.

When using such a hollow cathode discharge device as an ion generation source, it is necessary to supply working gas at a low flow rate as much as possible in order to improve gas efficiency during ion generation. Although it is desirable to be able to proceed to arc discharge even when the inside of the hollow cathode 1 is under a sufficiently low gas pressure state, it has been difficult to start up under low gas pressure conditions in conventional discharge devices.

Purpose of the Invention The present invention has been made in view of the above circumstances.The purpose of the present invention is to provide a compact and lightweight device that is less likely to malfunction, and that allows for easy discharge starting even under low gas pressure. An object of the present invention is to provide a hollow cathode discharge device that consumes less power and can contribute to improving the efficiency of ion plasma generation.

Summary of the Invention The present invention aims to reduce the size and simplicity of a heater for emitting thermoelectrons by emitting thermoelectrons that trigger activation from an internal electrode provided insulated from a hollow cathode. 1.
It is characterized in that the discharge is made to proceed to arc discharge through a two-stage discharge between the internal electrode and the starting electrode and between the starting electrode and the hollow cathode.

Examples of the invention Embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a sectional view showing a schematic configuration of a hollow cathode discharge device according to the present invention, and the same parts as in FIG. 1 are indicated by the same symbols.

Therefore, the explanation of the overlapping parts will be omitted.

In this embodiment, a plurality of inlets 21 for inflowing the working gas are provided in the wall of the hollow cathode 1 in the radial direction, and the space between the hollow cathode 1 and the heat shield cylinder 6 is used as the gas introduction path 22. .

In addition, a disk-shaped internal electrode 11 is disposed within the hollow cathode 1 at a position opposite to the anode so as to face the starting electrode 9. ) is fixed to the inner surface of the hollow cathode 1 via a support 23 formed of a material.

The internal electrode 11 is made of an electrode material with a small work function, and is electrically connected to the hollow cathode 1 via a switch 24.

Furthermore, a heater 25 for heating the internal electrode 11 is arranged near the end surface of the internal electrode 110 opposite to the anode, and the heater 25 is mounted on a disc-shaped heat-resistant support plate 26 fixed within the hollow cathode 1. I support it.

Therefore, in the device of the present invention, there is no heater for heating the hollow cathode, which is found in conventional devices.

To start the discharge of the hollow cathode discharge device configured as described above, proceed as follows.

A current is applied to the heater 25 by the heating power source 5 without switching, and the internal electrode 11 is sufficiently heated to a state 1 in which thermionic electrons can be emitted.

Then, a working gas is introduced into the hollow cathode 1 through the gas introduction path 22 from a working gas supply source (not shown).

At the same time, the switch 14 is turned on, and the output voltage of the starting power source 15 is applied between the starting electrode 9 electrically connected to the heat shield cylinder 6 and the internal electrode 11.

At this time, the switch 24 is opened to electrically insulate the hollow cathode 1 and the internal electrode 11.

When the switch 14 is turned on as described above, a glow discharge occurs between the two flat electrodes, the starting electrode 9 and the internal electrode 11, and as a result, plasma is generated within the hollow cathode 1.

After the plasma is sufficiently generated, the switch 24 is closed to make the internal electrode 11 and the hollow cathode 1 have the same potential.

Since sufficient plasma exists within the hollow cathode 1, glow discharge is easily generated between the hollow cathode 1 and the starting electrode 9.

The inner wall of the hollow cathode 1 is sufficiently heated by this glow discharge, and initial thermoelectrons and plasma necessary for arc discharge between the hollow cathode 1 and the anode 2 are supplied into the hollow cathode 1.

Next, the switch 17 is turned on, and the output voltage of the arc power source 18, ie, the arc voltage, is applied between the hollow cathode 1 and the anode 2.

As a result, an arc discharge, that is, a hollow cathode discharge is started between the hollow cathode 1 and the anode 2.

After starting p1, arc discharge continues even if the switch 14 is opened to remove the starting voltage.

In this way, the internal electrode is used as a source of thermionic electrons that triggers startup.

Therefore, unlike conventional devices, there is no need for a large heater to heat the hollow cathode 1, so that the heat shield cylinder 6 is not affected by the damage to the hollow cathode 1a and the heat shield tube 6, which tends to occur when the heater 3 for heating the hollow cathode is provided. Concerns about failure due to contact are eliminated,
Moreover, the device can be made smaller and lighter.

Further, according to the present invention, since it is sufficient for the heater 25 to heat only the internal electrode 11, the power consumption by the heater can be reduced compared to a conventional hollow cathode heating heater, and the device can be operated efficiently. is possible.

In addition, the internal electrode 1 is
Since the discharge occurs in two stages: between the hollow cathode 1 and the starting electrode 9, and between the hollow cathode 1 and the starting electrode 9, the discharge can be started easily and reliably at a low working gas pressure.

Therefore, it is possible to obtain a device that can obtain sufficiently high gas efficiency and has a high ion and plasma generation rate.

Further, by forming the internal electrode 11 with an electrode member having a small work function as in the embodiment, the initial glow discharge can be performed more easily.

The button and internal electrode are not necessarily limited to a disk shape.

As described in detail, according to the present invention, thermionic electrons that trigger the discharge start are emitted from the internal electrode, so the heater for emitting thermionic electrons can be miniaturized and simplified. , it is possible to improve the reliability of the device, and in addition, arc discharge is achieved through two stages of discharge: opening between the internal electrode and the starting electrode, and between the starting electrode and the hollow cathode. Therefore, it is possible to facilitate the discharge start-up under low gas pressure, and it is possible to improve the generation efficiency of ions and plasma.

[Brief explanation of drawings]

1A and 2 are sectional views showing the schematic structure of a conventional hollow cathode discharge device, respectively, and FIG. 3 is a sectional view showing the schematic structure of a hollow cathode discharge device according to an embodiment of the present invention. 1...Hollow cathode, 2...
... Anode, 3... Heater, 6...
・Heat shield tube, 9...Starting electrode, 11...
...Internal electrode, 21...Inflow port, 23...
... Support body, 25 ... Heater, 26 ...
...Heat-resistant support plate.

Claims (1)

[Claims] 1. Arc discharge is performed between the hollow cathode and the anode in a state where the hollow cathode and the anode are arranged facing each other in a spaced manner in a discharge chamber, and working gas is flowing through the hollow cathode toward the anode side. In the hollow cathode discharge device, a starting electrode having a gas flow rate limiting function is provided in an opening located on the anode side of the hollow cathode and is insulated from the hollow cathode; an internal electrode that is insulated from the hollow cathode and provided opposite to the starting electrode; and a heater that heats the internal electrode; After a glow discharge is caused between the internal electrode and the starting electrode under heating conditions, a glow discharge is caused between the hollow cathode and the starting electrode, and then a glow discharge is caused between the hollow cathode and the starting electrode. A hollow cathode discharge device characterized in that it is configured to cause arc discharge between an anode and an anode.