JPS6314875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas laser oscillator, and particularly to the structure of its dielectric electrode.

A typical example of this type of laser is a three-axis orthogonal CO ₂ laser in which the laser optical axis, DC glow discharge path, and gas flow direction are substantially perpendicular to each other, so a conventional example will be described. Figure 1 is a vertical cross-sectional view of a 3-axis orthogonal laser, and Figure 2 is a vertical cross-sectional view of the 3-axis orthogonal laser.
Figure - A cross-sectional view taken along the line, 1 is an anode, 2 is a cathode, 3 is a cathode substrate, 4 is a stabilizing resistor, 5 is a DC high voltage power supply, 6 is a discharge excitation part, 7 is a total reflection mirror, 8
is a partially reflective mirror.

Next, the operation will be explained. When a laser gas consisting of a mixed gas of CO ₂ , N ₂ , and He is flowed between the anode 1 and the cathode 2 at a flow rate of several tens of meters per second and a high DC voltage is applied, a discharge occurs between the electrodes, but the stabilizing resistor 4
Because current flows through the discharge, the discharge does not turn into an arc, and a gentle glow discharge is maintained. In the discharge excitation part 6 generated by the glow discharge, a population inversion occurs between specific vibrational levels of CO ₂ molecules in the laser gas, and between the discharge excitation part 6 a total reflection mirror 7 and a partial reflection mirror having an appropriate reflectance are connected. 8 are placed facing each other, laser oscillation occurs and a laser beam is emitted from the partially reflecting mirror 8. The laser output increases as the discharge power increases; for example, in the case shown in Figure 1, the cathode 2
Assuming that the number of lines is constant, an increase in discharge power is equivalent to an increase in discharge density. Making the device more compact;
From the viewpoint of cost reduction, it is desirable to increase the discharge density, but if the discharge power is increased beyond a certain level, a high temperature area will occur locally in the discharge area, and even if the stabilizing resistor 4 is present, the discharge will move to arc. When the discharge shifts to an arc, laser output can no longer be obtained and the deterioration of the laser gas increases significantly. Therefore, with the configuration of the discharge electrode as shown in FIG. 1, the discharge density cannot be increased beyond a certain level.

In order to solve these difficulties, attempts have been made to increase the discharge density while maintaining the glow discharge by performing preliminary ionization near the glow discharge to help the glow of the main discharge become uniform and stable. ing. Pre-ionization methods include electron beam, ultraviolet irradiation by pulse discharge, and silent discharge.

Since this invention is based on the conventional preliminary ionization method using silent discharge, a conventional example of this method will be explained first.

Figure 3 is a longitudinal cross-sectional view of a horizontally pumped gas laser oscillator using a pre-ionization method using silent discharge, and Figure 4 is a cross-sectional view taken from the line in Figure 3, where 9 is a dielectric electrode, and 10 is a cooling electrode. 11 is a cooling water inlet, 11 is a cooling water outlet, 12 is a high voltage terminal, 13 is an AC high voltage power source for producing silent discharge, 14 is a fuse, and FIG. 5 is a cross-sectional view of the dielectric electrode 9. , 9-1 is an iron pipe, 9-2
is a dielectric layer (for example, glass) formed in close contact with the iron pipe, and is a so-called "enameled" glass-lined electrode.

Next, the operation will be explained. When an AC high voltage is applied to the dielectric electrode 9, a silent discharge occurs between the cathode 2 and the anode 1. When a DC high voltage is applied in this state, a main discharge glow occurs and a discharge excitation part 6 is formed, which increases the power density by 2 to 3 times in a stable glow discharge state compared to when preliminary ionization of silent discharge is not performed. can be input.

Experiments have shown that the power for silent discharge is approximately 1/20 of the power for main discharge (glow).

In such an electrode configuration, since the current supplying electrode of the dielectric electrode 9 is the iron tube 9-1, silent discharge occurs on the entire electrode surface. When a discharge occurs, heat is generated, but the dielectric 9-2's dielectric strength drops rapidly when the temperature exceeds 100°C, so the temperature must be kept below this. Since the dielectric electrode 9 facing the anode 1 and cathode 2 is placed in a high-speed gas flow of several tens of meters per second,
The heat generated by the silent discharge is effectively carried away by the gas flow and cooled, and the temperature of the dielectric 9-2 does not rise more than several tens of degrees. However, since the laser gas flow remains at the end of the dielectric electrode 9 (near the terminal part), the heat generated by the discharge in that part is not carried away by the laser gas. Therefore, if the dielectric electrode 9 is not forcibly cooled in such a state, the temperature of the dielectric 9-2 at the end of the dielectric electrode 9 will rise, and the withstand voltage will drop, causing the dielectric 9 to cool down. -2 will be destroyed. For this reason, conventionally,
As shown in Figure 3, it is necessary to have a structure in which cooling water flows into the dielectric electrode 9, which may cause stress or surge voltage to be applied to the dielectric, causing the dielectric to deteriorate. In order to prevent water leakage, a dielectric electrode with a glass-lined iron pipe structure, as shown in Figure 5, is used to ensure mechanical strength. was used.

However, since the glass lining of iron pipes is manufactured by baking glass powder onto the iron pipe, there is always residual stress in the glass, and during annealing, residual stress is generated due to the difference in thermal expansion coefficient between glass and iron. It is difficult to make dielectric electrodes with small diameters, and the minimum diameter is 10 to 15 mm. Furthermore, it is expensive because there are many manufacturing steps.

By the way, the gap length of the main discharge of the laser oscillator, that is, the distance between the anode 1 and the cathode 2, is 20 mm to 50 mm.
mm, and as shown in Figure 3, when the dielectric electrode 9 is placed inside the gap, the dielectric electrode 9 occupies about 1/2 to 1/5 of the length of the gap. Become. As is well known, in order for the glow discharge to be stable, it is preferable that the laser gas flows at high speed and in a rectified manner.From this point of view, the dielectric electrode 9 is an obstacle that causes disturbance in the flow of the laser gas. It has become a thing. However, conventionally, a glow discharge excitation method using silent discharge as pre-ionization has been adopted because the effect of pre-ionization of silent discharge is greater than the instability of the discharge due to disturbance of the laser gas. This is because a large discharge density can be obtained.

Therefore, if the dielectric electrode is shaped to have a low flow path resistance, for example by making the diameter thinner, the disturbance in the laser gas flow will be reduced, the discharge density will be increased, and the laser oscillator can be made more compact, but as mentioned above, , in the case of a conventional steel pipe with a glass lining,
It was not possible to make the diameter smaller than a certain point.

This invention was made to eliminate these conventional drawbacks, and has a simple structure and does not require forced cooling. It is an object of the present invention to provide a laterally pumped gas laser oscillator equipped with a dielectric electrode.

FIG. 6 is a vertical sectional view of one embodiment of the present invention, and FIG.
The figure is a longitudinal cross-sectional view of the dielectric electrode, where 9-3 is a dielectric tube made of glass, etc., 9-4 is a dielectric tube, and a conductive material such as a vapor-deposited metal film is provided in close contact with the inner surface of 9-3. Section 9-5 is a high voltage power supply line. Next, the operation will be explained. The conductive part 9-4 includes an anode 1 and a cathode 2.
Since only the portion facing the is formed, silent discharge occurs only in this portion. Heat is generated in this portion by silent discharge, but since the laser gas flow is flowing at several tens of meters per second, all of the heat is carried away by the gas flow and the temperature of the dielectric tube 9-3 does not rise. On the other hand, near the high voltage terminal 12 where the laser gas is not flowing or at the other end, the conductive part 9-4 is not formed, so silent discharge does not occur, and therefore no heat is generated, so the dielectric tube 9 -3 temperature does not rise. Therefore, there is no need to water-cool the dielectric electrode 9, which simplifies the structure.

Furthermore, if a glass tube is used as the dielectric tube 9-3, and the conductive portion 9-4 is formed on the inner surface by plating, etc., even a very thin tube can be freely manufactured, so the diameter can be as small as 5 mm. For example, turbulence in the flow of laser gas is extremely reduced. Therefore, by applying this dielectric electrode, it is possible to stably increase the power of silent discharge as preliminary ionization and at least the discharge density of glow discharge (main discharge) compared to the conventional method. If the silent discharge requires less power, the temperature rise in the dielectric tube 9-3 will also be reduced, and this synergistic effect will further improve reliability.

FIG. 8 is a vertical cross-sectional view of another embodiment of the dielectric electrode according to the present invention, and 9-6 is a fibrous metal such as steel wool filled only in the portion facing the anode 1 and cathode 2, and the high voltage It serves as a conductive part that is connected to the power supply line 9-5 and supplies silent discharge current.

In this way, the power supply portion can be formed with an extremely simple structure of simply stuffing the wool-like metal 9-6 into the dielectric tube 9-3.
Note that since the steel wool shown in this example serves as a power supply, metal grains,
It is easy to understand that any conductive material such as wire mesh can be used.

FIG. 9 is a longitudinal sectional view of another embodiment of the dielectric electrode, where 9-7 is an insulator filled with glass beads, glass wool, etc., for example. By filling both ends of the wool-like metal 9-6 with the insulator 9-7, the electric field at the electrode end of the steel wool 9-6 is weakened and end discharge from the ends is prevented, resulting in a silent discharge. The applied voltage for generating can be increased, and therefore the discharge density of glow discharge can also be further increased. Further, since the high voltage power supply line 9-5 is covered with the insulator 9-3, there is an advantage that the power supply line 9-5 can be insulated at the same time.

FIG. 10 is a longitudinal sectional view of still another embodiment, 9-
8 is a cylinder through which the high-voltage power supply line 9-5 is passed through the center hole.
For example, glass tubes and ceramic tubes. When such an insulating tube 9-8 is used, the high-voltage feeder line 9-5 can be placed in the center of the dielectric tube 9-3, which ensures more reliable insulation of the feeder line and reduces the trouble of centering the line. It has the characteristic that it does not cost much.

The present invention provides a gas laser oscillator equipped with a dielectric electrode that generates a silent discharge between an anode and a cathode that are arranged to sandwich a laser gas airflow and face each other, in which the dielectric electrode is made of a dielectric material. A conductive portion formed only in a portion of the tube that is exposed to the laser gas flow and cooled, and a high-voltage power supply line that supplies power to the conductive portion from outside the tube through the inside of the tube. Since the dielectric electrode can be made small in diameter with low flow path resistance, the oscillator can be made smaller and have higher output.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional horizontally pumped gas laser device, Figure 2 is a cross-sectional view taken from the line in Figure 1, and Figure 3 is a vertical cross-sectional view of a conventional gas laser device equipped with dielectric electrodes. , FIG. 4 is a cross-sectional view taken along the line of FIG. 3, FIG. 5 is a cross-sectional view of a conventional dielectric electrode, and FIG. 6 is a vertical cross-sectional view of an embodiment of the present invention.
FIG. 7 is a longitudinal cross-sectional view of a dielectric electrode according to the present invention;
FIG. 8, FIG. 9, and FIG. 10 are longitudinal sectional views of other embodiments of the dielectric electrode according to the present invention. In the figure, 1 is an anode, 2 is a cathode, 5 is a high voltage DC power supply, 6 is a discharge excitation part, 9 is a dielectric electrode, 9 -
1 is an iron pipe, 9-2 is a dielectric pipe, 9-3 is a dielectric pipe, 9-4 is a conductive part, 9-5 is a high-voltage feeder line, 9-
6 is glass wool, 9-7 is an insulator, 9-8 is an insulating tube, and 13 is an AC high-voltage power source. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. In a gas laser oscillator equipped with a dielectric electrode that generates a silent discharge between an anode and a cathode that are arranged to sandwich a laser gas airflow and face each other, the dielectric electrode is , a tube made of a dielectric material, a conductive part formed only in a portion of the tube that is exposed to the laser gas flow and cooled, and power is supplied to the conductive part from outside the tube through the inside of the tube. A gas laser oscillator comprising a high-voltage power supply line. 2. The gas laser oscillator according to claim 1, comprising a granular or wool-like insulator filling both ends of a conductive portion formed inside the tube. 3. The gas laser oscillator according to claim 1 or 2, comprising an insulating tube through which a high-voltage power supply line is passed. 4 Claim 1 in which the conductive part is a metal vapor deposited film, granular or wool-like metal, or wire mesh
The gas laser oscillator according to any one of Items 1 to 3.