JPS6328517B2 - - Google Patents

Description

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

FIG. 1 is a vertical cross-sectional view showing the configuration of a discharge section of a so-called triaxial orthogonal type CO ₂ laser oscillator, which is a typical conventional type of this type of CO 2 laser oscillator, in which the optical axis, discharge, and gas flow directions are orthogonal to each other. Figure 2 is a cross-sectional view taken along the line in Figure 1, where 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, and 6
1 is a dielectric electrode, 7 is a power supply line, 8 is deionized water flowing through the dielectric electrode 6 to cool it, 9 is an AC high-voltage power supply, 10 is a discharge excitation unit, 11 is a laser gas, 12
13 is a total reflection mirror, 13 is a partial reflection mirror, and 20 is a laser beam.

Next, the operation will be explained.

CO ₂ , N ₂ ,
While flowing the laser gas 11 made of He in the direction of the arrow, the dielectric electrode 6 disposed upstream of the cathode 2 is heated.
When the AC high voltage from the AC high voltage power supply 9 is applied, the dielectric electrode 6 and the cathode 2, and the dielectric electrode 6 and the anode 1
A silent discharge is generated between the Here, when a DC high voltage from the DC high voltage power supply 5 is applied via the stabilizing resistor 4, a homogeneous and stable glow discharge is generated between the anode 1 and the cathode 2 due to the preliminary ionization effect of the silent discharge. In the discharge excitation section 10 formed by this discharge, a population inversion is formed between specific vibration levels in the laser gas 11. Laser oscillation is generated by an optical resonator made up of a total reflection mirror 12 and a partial reflection mirror 13 which are arranged to face each other with the discharge excitation part 10 in between, and a laser beam 20 is emitted from the partial reflection mirror 13.

Here, the discharge area of the divided cathode 2 and the voltage-current characteristic (V-characteristic) of the discharge will be explained. FIG. 3 is a typical VI characteristic diagram in gas discharge. Until the current reaches a certain value, constant voltage characteristics are maintained regardless of the current value. The discharge at this time is called a regular glow discharge. In this region, electrons are supplied by secondary electron emission due to collisions between electrons and gas atoms and molecules (α effect), and electron emission due to collisions between positive ions and the cathode surface (γ effect). The gamma effect is maintained by the voltage drop Vc present across the cathode surface. The value of Vc remains constant as long as the cathode surface is larger than the area where discharge is actually occurring on the cathode surface. A normal glow discharge is a discharge that satisfies this, the current density is always constant, the increase in current is compensated for by the increase in cathode discharge area, and the discharge sustaining voltage is kept constant.

When the current increases until all dischargeable cathode surfaces are covered by the discharge, the current is compensated for by the increase in Vc, ie, the discharge sustaining voltage increases. The discharge at this time is called an abnormal glow discharge.

As the current increases further, the temperature of the cathode surface rises, and thermionic emission becomes dominant, causing a rapid increase in current density and, conversely, a decrease in Vc. The discharge at this time is called arc discharge. Regular glow discharge is required to efficiently excite the laser medium.

By the way, in the electrode structure shown above, the discharge that has been generally used conventionally has no silent discharge as an auxiliary discharge, and glow discharge has been obtained simply by direct current discharge. At this time, as a cathode,
A metal rod of about 6φ with a sharpened tip.
Many were used side by side. The conventional electrode shape is the fourth
As shown in the figure. In the case of direct current discharge only, even if such a cathode is used, charge concentration occurs in the discharge space and arc discharge occurs before all possible discharge surfaces are covered. However, as shown in the previous example, when a silent discharge as an auxiliary discharge is superimposed, the concentration of charge is alleviated due to its preliminary ionization effect, and the input current can be increased by 2 to 3 times. Discharge gap length 75mm, CO ₂
FIG. 5 shows the VI characteristic A of the normal glow discharge region when the silent discharge is superimposed at a laser gas pressure of 100 torr, and the VI characteristic B of the normal glow discharge region when the silent discharge is not superimposed. When the current increases due to the silent discharge superposition, the conventional cathode shape has the problem of transitioning to arc discharge due to insufficient discharge area. This prevents the necessary high power discharge.

This invention was made to eliminate the above-mentioned drawbacks of the conventional technology. By increasing the discharge area of the cathode, it prevents the transition to arc discharge. with high output,
The purpose is to provide a highly efficient laser device.

An embodiment of the present invention will be described below.
FIG. 6 is a perspective view of a cathode according to the present invention, and FIG. 7 is a longitudinal cross-sectional view of a laser oscillator equipped with the cathode.
FIG. 8 is a cross-sectional view of the cathode taken along the line, and 14 is an improved cathode whose width _W1 is, for example, 10 to 50 mm.
Each cathode has 4 resistors for stabilizing the discharge as before.
is connected.

The improved cathode 14 has a discharge portion in the shape of a triangular prism, and in this example is arranged so as to extend in the gas flow direction. Therefore, the cathode area is expanded in the gas flow direction, and the transition to arc discharge due to insufficient discharge area, as in the conventional case, is eliminated. In this case, as shown in Fig. 7, the cathode spacing in the optical axis direction is the same as before, but as shown in Fig. 8, the discharge area in the gas flow direction increases, and the unit in the optical axis direction increases. Input power per length increases. This results in
Compared to the case of needle-shaped cathodes, fewer cathodes are required to input the same discharge power, and the device can be made smaller. The reason why the tip of the cathode 14 is shaped like an edge is to define the discharge starting point and stabilize the discharge.

FIG. 9 is a perspective view of another embodiment of the cathode according to the present invention, FIG. 10 is a vertical cross-sectional view of a laser oscillator equipped with the electrode, and FIG. 11 is a cross-sectional view taken from the line XI--XI in FIG. shows. In this example, the area of the cathode 14 is expanded in the optical axis direction, and the width W ₂ of the cathode is 8 mm.
30mm or less, and the discharge surface should be 30mm to 30mm relative to the gas flow in order to reduce fluctuations in the discharge relative to the gas flow.
It has an inclination θ of 60 degrees, and its tip is formed into an edge shape. In this example, since the width of the electrode is widened in the optical axis direction, it is possible to input only the same amount of power as in the case where the conventional cathode pin 2 as shown in FIG. 5 is used. However, as shown in FIG. 10, the number of cathode pins can be reduced to about 1/2 to 1/5, which has the advantage of making the device easier to manufacture and to perform maintenance and inspection.

Figures 12 and 13 are perspective views showing other examples in which the width of the cathode is widened in the optical axis direction.
W ₂ is 8 mm or more and 30 mm or less, and an edge is formed to stabilize the discharge at the start of discharge, and it functions similarly to the example shown in FIG. 9.

The above embodiments have all been applied to three-axis orthogonal type laser oscillators; It goes without saying that similar effects can be obtained when applied to lasers.

As described above, according to the present invention, AC discharge exists as an auxiliary discharge, and by widening the width of the cathode in the gas flow direction or optical axis direction, arc discharge caused by insufficient cathode discharge area can be prevented. The transfer can be prevented, the discharge power can be increased, the device can be made smaller, or the number of cathodes can be reduced, and the performance of the laser can be improved.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional gas laser oscillator.
Figure 2 is a cross-sectional view taken from Figure 1 - line, Figure 3
The figure shows typical voltage-current characteristics in gas discharge, Figure 4 is a needle view of a conventional cathode, and Figure 5 shows normal conditions with and without silent discharge as an auxiliary discharge. 6 is a perspective view of an embodiment of the cathode according to the present invention; FIG. 7 is a vertical sectional view of a gas laser oscillator to which the cathode shown in FIG. 6 is applied; 8 is a cross-sectional view taken along the line of FIG. 7, FIG. 9 is a perspective view of another embodiment of the cathode according to the present invention, and FIG. 10 is a longitudinal cross-section of a gas laser oscillator to which the cathode shown in FIG. 9 is applied. 11 is a cross-sectional view taken along the line XI--XI in FIG. 10, and FIGS. 12 and 13 are perspective views of other embodiments of the cathode according to the present invention. In the figure, 1 is an anode, 2 and 14 are cathodes, 5 is a DC high-voltage power supply, 6 is a dielectric electrode, 7 is a power supply line, and 9
10 is an AC high-voltage power supply, 10 is a discharge excitation unit, 11 is a laser gas, 12 is a total reflection mirror, 13 is a partial reflection mirror, 2
0 is a laser beam. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. An anode and a cathode that are arranged to face each other across the laser gas airflow and to which a DC high voltage is applied to generate a glow discharge, and an anode and a cathode which are arranged in the laser gas airflow and to which an AC high voltage is applied. and a dielectric electrode that generates a silent discharge between the cathode and both of the electrodes, wherein the cathode has an edge extending in the direction of the laser gas flow, and the cathode is arranged along the laser optical axis. A gas laser oscillator characterized by having a configuration in which a plurality of laser oscillators can be installed. 2. The gas laser oscillator according to claim 1, wherein the width _W1 of the edge of the cathode is within a range of 10 to 50 mm. 3. The gas laser oscillator according to claim 1, wherein the width _W2 of the cathode in the optical axis direction is within the range of 8 to 30 mm.