JPH07183594A - Discharge electrode for gas laser - Google Patents

Abstract

PURPOSE:To make an output of a laser large while making the scale of a device compact by a construction wherein a negative electrode for a DC glow discharge is formed in the shape of a sharpened cone, the fore end part of the negative electrode for the DC glow discharge is opposed to a positive electrode and the negative electrode for the DC glow discharge is embedded in a hole part provided in an electrically insulating plate. CONSTITUTION:On the lower side of an electrically insulating plate 1a, a plurality of hole parts 2 are provided linearly at equal intervals. In each hole part 2, a conical needle-shaped negative electrode 8 is installed with the fore end part directed downward. Under the electrically insulating plate 1a, an electrically insulating plate 1b is disposed oppositely to the insulating plate 1a in parallel thereto. On the upper side of the insulating plate 1b, a positive electrode 5 is disposed at a position corresponding to the negative electrode 8 of the electrically insulating plate 1a. Since the negative electrode 8 is embedded inside the electrically insulating plate 1a herein, a glow discharge is not affected by proximity actions of turbulence of a flow of a laser gas, fluctuation of temperature, etc. Accordingly, a stable glow discharge is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser discharge electrode suitable for a discharge excitation gas laser device.

[0002]

2. Description of the Related Art It is generally known that it is necessary to make a laser gas circulation system compact in order to make the scale of a gas laser device compact while increasing the output of the laser. The laser output ideally needs turbulence, a small temperature and flow velocity distribution, and low turbulence and thermo-fluid characteristics, but if the laser device is made compact,
These characteristics deteriorate. For example, removing the straight part of the wind tunnel,
If the device is made compact by reducing the contraction ratio, etc., the deterioration of the gas fluid characteristics will result in an increase in the degree of turbulence, the occurrence of drift, and the expansion of the temperature distribution. Due to such deterioration of the fluid characteristics, the glow discharge for exciting the laser medium (laser gas) is likely to shift to the arc discharge. In particular, regarding the fluid characteristics, the influence on the stability of the discharge appears remarkably, so that the flow sensitivity for evaluating the influence on the stability of the discharge becomes sensitive. That is, when the fluid characteristics are deteriorated, for example, the turbulence is increased, the input of the glow discharge discharge electrode is significantly reduced. Therefore, it becomes necessary to relax the thermofluid characteristic design allowable value. Therefore, when trying to increase the output of the laser,
The device was inevitably enlarged. Therefore, it has been difficult to reduce the size of the gas laser device while increasing the output of the laser.

Therefore, conventionally, there has been a long-felt need for a discharge electrode in which the amount of change in input is small and glow discharge does not transfer to arc discharge even if the thermal fluid characteristics are deteriorated. Next, a schematic configuration of a discharge electrode used in a conventional gas laser device is shown in FIG.
Shown in.

As shown in FIG. 2, the electrical insulating plate 1a includes
A plurality of cathodes 12 are arranged on a straight line in a direction perpendicular to the paper surface. Each cathode 12 is connected to a high voltage power source 4 via a discharge stabilizing resistor 3, respectively.

An anode 5 to which a high voltage is applied from a high voltage power source 4 is arranged parallel to and facing the insulating plate 1a.
The laser gas 6 flows between the cathode 12 and the anode 5.

The oscillation region 7 is a region where excited laser gas molecules oscillate. In the glow discharge generated by using the gas laser discharge electrode having such a structure, electrons are emitted mainly by the secondary electron emission action by the charged particles in the vicinity of the cathode 12 and the secondary electron emission action by the photons. The emitted electrons cause ionization, dissociation, excitation, etc. of the laser gas molecules, and the glow discharge is maintained when the balance of charged particles and photons is preserved.

Next, as an example of a conventional discharge electrode, an example in which a hollow cathode is applied is shown in FIG. The hollow cathode 9 is
For example, it has a structure in which one end of a cylinder is closed. At the time of discharge, a so-called hollow cathode effect appears by generating a negative glow on the inner surface of the cylindrical portion and combining the negative glow generated from the inner surface. By this hollow cathode effect, secondary electron emission by photons is promoted, and the electron emission capability is increased.

Further, as another example of the discharge electrode, there is one proposed by the applicant of the present application in a prior application (Japanese Patent Application No. 2-218542). In the discharge electrode of this prior application, a cathode with a V-shape having a conical portion at its tip and a columnar portion at its base is provided on the electrically insulating plate so that only the conical portion at its tip projects into the laser gas. It has a structure.

In this discharge electrode, the tip portion of the cathode serves as a high electric field concentration portion where a high electric field is generated. Therefore, at the time of discharge, a starting point for starting the discharge is formed at the tip portion, and the negative glow is fixed. When the discharge current is further increased, the negative glow part spreads from the tip of the cathode along its conical surface,
Negative glow is fixed near the conical portion of the cathode, and stable glow discharge can be maintained. Then, by reducing the angle of the tapered portion of the conical portion, the discharge area can be easily expanded, and a higher discharge current can be obtained.

[0010]

When the hollow cathode is used as the discharge electrode as described above, the hollow cathode 9 is embedded in the insulating plate 1a as shown in FIG. Since it is embedded in the plate 1a, densification of plasma in the vicinity of the cathode 9 does not occur due to turbulence of gas flow, temperature fluctuation, and the like. For this reason, the plasma starting point can be fixed without providing a high electric field concentration portion, but since the cathode 9 is embedded in the insulating plate 1a, there is a limit to the expansion of the cathode area, and a high current for high output is required. There was a limit to how much I could take out. As described above, the discharge electrode described above is not affected by the deterioration of the thermofluid characteristics such as the turbulence of the flow of the laser gas and the fluctuation of the temperature. Not suitable.

On the other hand, a prior application for the discharge electrode (Japanese Patent Application No. 2-218)
In the case of using the discharge electrode of No. 542), the pointed portion of the cathode serves as a high electric field concentration portion, so that the plasma starting point can be fixed in this high electric field concentration portion. However, since the cathode is projected from the lower surface of the electric insulating plate (the surface on the side facing the anode), the density of plasma is generated in the vicinity of the cathode due to the proximity effect such as the turbulence of the laser gas flow and the temperature fluctuation Due to the density of the plasma, the glow discharge sometimes shifts to the arc discharge.

As described above, since the glow discharge by the discharge electrode is affected by the deterioration of the thermofluid characteristics such as the disturbance of the flow of the laser gas and the fluctuation of the temperature, it is difficult to make the apparatus compact.

The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a discharge electrode for a gas laser capable of increasing the output of a laser while making the scale of the apparatus compact.

[0014]

SUMMARY OF THE INVENTION According to the present invention, a laser gas is provided at a predetermined flow velocity between a DC glow discharge cathode and an anode, which are respectively disposed on a pair of insulating plates placed in parallel and facing each other. In the discharge electrode for gas laser configured to flow in, the direct current glow discharge cathode is made into a conical shape having a fine pointed shape, and the tip of the direct current glow discharge cathode is opposed to the anode, and the direct current glow discharge is performed. It is characterized in that the cathode for use is installed so as to be buried in the hole provided in the electric insulating plate.

[0015]

According to the above structure, since the cathode is buried inside the electric insulating plate, even if the laser gas flows between the cathode and the anode, the sensitivity of the laser gas flow is alleviated.

Further, since the shape of the cathode is a pyramid, even when the cathode is buried in the insulating plate, the tip portion thereof becomes a high electric field concentrated portion, so that secondary electron emission due to charged particles near the cathode is maintained. , The plasma starting point is also fixed.

Further, since the cathode has a conical shape, the discharge area during glow discharge can be easily expanded even when the cathode is buried in the insulating plate. That is, the shape of the cathode is a pyramid, and the electrons at the time of discharge jump out perpendicularly to the surface of the cathode. Therefore, the discharge area can be easily expanded by reducing the angle of the tapered portion of the cone. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 (a) is a diagram showing a detailed configuration of a gas laser discharge electrode according to the embodiment, and FIG. 1 (b) is a diagram showing FIG.
It is an enlarged view of the part A of (a).

In FIG. 1 (a), a plurality of holes 2 are linearly provided at equal intervals on the lower surface of the electric insulating plate 1a in the paper surface direction. As shown in FIG. 1B, a conical acicular cathode 8 is installed in each hole 2 with its tip facing downward. Each cathode 8 is connected to the high-voltage power supply 4 via the discharge stabilization resistor 3, respectively.

Below the electrical insulating plate 1a, the insulating plate 1a is provided.
An electric insulating plate 1b is arranged in parallel to face with. An anode 5 is arranged on the upper surface of the insulating plate 1b at a position corresponding to the cathode 8 of the electric insulating plate 1a. The anode 5 is connected to the high voltage power supply 4.

A laser gas for exciting the laser flows between the cathode 8 and the anode 5 arranged in this way along the flow indicated by the arrow 6. The laser gas molecules excited between the cathode 8 and the anode 5 oscillate in the oscillation region 7.

The operation when the gas laser discharge electrode having the above structure is applied will be described. The laser gas for exciting the laser is directed in the direction of arrow 6 in the electric insulating plates 1a, 1b.
Flows in at a predetermined flow rate during. The laser gas also flows into each hole 2 provided on the lower surface of the electrical insulator 1a.

In this state, when a high voltage is applied from the high voltage power source 4 between the cathode 8 and the anode 5, a high electric field is generated at the tip of the cathode 8. Then, this tip portion becomes the starting point of the discharge start, and the negative glow is fixed. Further, when the discharge current is increased, the negative glow part spreads from the tip part of the cathode 8 along its conical surface.

Here, since the cathode 8 is buried inside the electric insulating plate 1a, the glow discharge is not affected by the proximity effect such as the disturbance of the flow of the laser gas and the temperature fluctuation. Therefore, the density of plasma is not generated in the vicinity of the cathode 8, and stable glow discharge is maintained.

[0025]

According to the present invention, since the cathode is embedded in the electric insulating plate, the flow sensitivity is alleviated.
The size of the gas laser device can be made compact. Further, according to the present invention, by making the shape of the cathode to be buried in the electric insulating plate into a pyramidal shape, the discharge area of the discharge current can be easily expanded, and a high discharge current can be obtained even in a compact device size. Therefore, the output of the laser can be increased while the size of the device is made compact.

According to the present invention, the conical cathode is embedded in the hole provided in the lower surface of the insulating plate so that the tip of the conical cathode faces the anode, so that the cathode is embedded in the electrical insulating plate. However, since the shape of the cathode is a pyramid, it is easy to increase the discharge area by reducing the taper angle, so that it is possible to easily achieve a large laser output.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a gas laser discharge electrode according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a conventional gas laser discharge electrode.

FIG. 3 is an enlarged view of a cathode portion of a conventional gas laser discharge electrode.

[Explanation of symbols]

1a, 1b ... Electrical insulating plate, 2 ... Cathode, 3 ... Stabilizing resistor for discharge, 4 ... High voltage power source, 5 ... Anode, 6 ... Laser gas flow, 7 ... Oscillation region,
8 ... Imbedded needle cathode.

Claims (1)

[Claims] 1. A laser gas flows at a predetermined flow velocity between a pair of DC glow discharge cathodes and an anode, which are respectively arranged on a pair of electric insulating plates that are arranged in parallel and face each other. In the discharge electrode for gas laser, the direct current glow discharge cathode is in the shape of a narrowed pyramid, the tip of the direct current glow discharge cathode is opposed to the anode,
A discharge electrode for a gas laser, wherein the cathode for DC glow discharge is installed so as to be buried in a hole provided on the lower surface of the electric insulating plate.