JPH0586875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in the electrode structure of a silent discharge type gas laser device.

[Conventional technology]

An example of a silent discharge type gas laser device is a three-axis orthogonal CO ₂ laser device. Figures 1, 2, and 3 show the principle configuration and discharge state of the electrode section of a conventional three-axis orthogonal CO ₂ laser.
The figure shows the case where the dielectric electrode is used without being covered, and Figures 2 and 3 show the case where the parts other than the opposing surfaces of the dielectric electrode are covered with an insulating layer of silicone rubber and ceramic powder, respectively. be.

In FIG. 1, 1 and 2 are laser gases,
It is circulated perpendicularly to the discharge direction 7 via a heat exchanger and a blower (not shown). Reference numeral 3 denotes metal electrodes, each of which is covered with a thin dielectric material 4 all around. Reference numeral 5 indicates cooling water, and reference numeral 6 indicates the area of the main discharge portion that contributes to laser oscillation.

Next, the operation of FIG. 1 will be explained based on the above configuration. First, when an alternating current high voltage is applied between a pair of metal electrodes 3 disposed opposite to each other, a silent discharge is generated via the dielectric 4. CO ₂ molecules in the laser gas 1 introduced into this discharge section are excited, and an optical resonator space is formed by a pair of mirrors (not shown) installed perpendicular to both the gas flow direction and the discharge direction. Excited above within
The stimulated emission of CO ₂ molecules is amplified and laser oscillation begins. On the other hand, since the temperature of the electrode portion increases due to the discharge, cooling water 5 is supplied inside the metal electrode 3 in order to prevent the dielectric 4 from being destroyed. Here, since the AC voltage applied between the metal electrodes 3 is higher than the discharge starting voltage in the space between the dielectrics 4,
As shown by the dotted line in the figure, the discharge spreads to the outside of the surface of the other metal electrode 3 facing the dielectric 4 among the surfaces of the dielectric 4. Due to this discharge spreading outward (hereinafter referred to as creeping discharge), discharge energy is removed from the main discharge portion 6, and the oscillation efficiency is reduced by this amount. Further, since this creeping discharge is not a uniform glow discharge but a convergent discharge, it increases the laser gas temperature within the optical resonator and causes a significant decrease in oscillation efficiency. As a conventional countermeasure to compensate for this drawback, as shown in FIGS. 2 and 3, the surface of the dielectric 4 other than the surface facing the dielectric 4 of the other metal electrode 3 is covered with an insulating material. I had something to cover. In FIG. 2, numeral 8 represents a flexible silicone rubber insulator. The performance required of these insulating layers is that (a) the dielectric 4 itself and the insulating layer are not destroyed by distortion due to thermal expansion of the dielectric 4 due to electric discharge, that is, the insulating layer is highly flexible; thing. (b) Organic outgas and impurity gases such as hydrogen are not generated from the insulating layer due to discharge. For the above condition (b), inorganic cement is preferable, but these materials should not be used. cannot satisfy the condition (a) above.

FIG. 3 shows an example in which an inorganic material such as ceramic powder is used as the insulator. In the figure, 3, 4, 5, and 6 are the same parts as in the case of FIG. 2, 9 is ceramic powder, and 10 is a frame made of an insulating material. Since there is no power, a space is created between the two and creeping discharge occurs as shown in the figure.
It's not a perfect solution.

For these reasons, the electrodes currently in use have a structure in which the surfaces of the dielectric 4 other than the opposing surfaces are thickly covered with a silicone rubber insulator 8 as shown in FIG. However, since the silicone rubber insulator 8 is bombarded with electrons due to discharge, it generates a small amount of organic gas and hydrogen, etc., and these impurity gases can interfere with the gas-sealing operation of the CO ₂ laser described below. This can cause major problems.

First, the laser gas is supplied into the container as a mixed gas of CO ₂ −CO−N ₂ −He, and when the gas is shut off and the operation is performed, the laser gas in the discharge section is expressed as shown in equation (a) below.
Both the dissociation of CO ₂ and the production of CO ₂ shown in equation (b) proceed.

CO ₂ → CO + O…(a), CO + O → CO ₂ …(b) The concentration of each component reaches its steady value when the reaction rates shown in equations (a) and (b) above become equal. . Further, the reason why CO is initially added to the above-mentioned mixed gas is to speed up the reaction of equation (b) and maintain a high steady-state value of the CO ₂ concentration. However, if even a small amount of organic outgas is generated, O atoms are consumed in the oxidation of this outgas, and in an attempt to compensate for this, the dissociation of CO ₂ in equation (a) above proceeds unilaterally, causing the CO ₂ concentration to increase. It will continue to decrease. As a result, the laser output gradually decreases during a long gas shutoff operation.

Figure 4 is a diagram showing changes over time in the laser output and the concentration (mole fraction) of each component in the mixed gas composition.As time passes, CO ₂ decreases and CO increases. This shows that the laser output decreases as a result.

Since the electrodes of conventional silent discharge gas laser devices are constructed as described above, they have had the disadvantage that impurity gas is generated from the silicone rubber insulator, making it difficult to operate the laser gas in a sealed state.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and in a silent discharge type gas laser device, the surface of the dielectric material of each electrode other than the surface facing the dielectric material of the other electrode. By covering the outside of the first insulating layer made of a highly flexible silicone rubber insulating material with a second insulating layer made of an inorganic insulating material that does not generate impurity gas, the discharge energy can be reduced. It can be effectively focused on the main discharge area, enabling shut-off operation of the laser.
Furthermore, the present invention provides a gas laser device in which the dielectric itself and the insulating layer are prevented from being destroyed due to distortion due to thermal expansion of the dielectric due to discharge.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 5, 3, 4, 5, and 8 are the same parts as in the conventional example, and 11 is a frame formed of an inorganic insulator bonded to the silicone rubber insulator 8, which is the second insulator layer (outer layer part). It consists of Note that the silicone rubber insulator 8 is the first insulator layer (inner layer portion).
It consists of

The operation of the present invention based on the above configuration will be explained. As is clear from the figure, the silicone rubber insulator 8 is not exposed to the discharge part, and the frame 11 that partially contacts the discharge part is formed of an inorganic insulator.
There is no generation of impurity gas due to the influence of electric discharge as in the conventional example.

Figure 7 is a diagram showing the results of an experiment conducted using the above example and the changes over time in the laser output and each component in the mixed gas composition _. The mole fraction of remains steady,
Even after 100 hours, the laser output decreases only by 4
It was %.

In the above embodiment, the inorganic insulator 11 is bonded to the silicone rubber insulator 8 covering the dielectric 4, but as shown in FIG. After placing it inside,
A forming method in which the silicone rubber insulator 8 is poured and molded may be used, and the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the outer side of the first insulator layer made of a silicone rubber insulator covers a portion of the surface of the dielectric of each electrode that is at least the surface facing the dielectric of the other electrode. is coated with a second insulating layer made of an inorganic insulator, the discharge energy can be efficiently concentrated in the main discharge area, and the laser output does not decrease even during continuous long-term gas shut-off operation. There is an effect that a silent discharge type gas laser device can be obtained in which there is almost no damage to the dielectric material itself and the insulating layer due to distortion due to thermal expansion of the dielectric material due to discharge.

[Brief explanation of drawings]

Figures 1, 2, and 3 are configuration diagrams showing the electrode section of a conventional three-axis orthogonal CO ₂ laser, and Figure 4 shows the laser output and each gas in Figures 1, 2, and 3. FIG. 5 is a block diagram showing one embodiment of this invention, FIG. 6 is a block diagram showing another embodiment of this invention, and FIG. 7 is a block diagram showing changes in mole fraction of FIG. 3 is a characteristic diagram showing changes in laser output and mole fraction of each gas. In the figure, 1 and 2 are laser gas flows, 3 is a metal electrode, 4 is a dielectric, 5 is a cooling water, 6 is a main discharge part, 7 is a discharge direction, 8 is a silicone rubber insulator, 9 is a ceramic powder, 10 is an insulator, 11
is an inorganic insulator. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An alternating current voltage is applied between a pair of electrodes disposed facing each other, each coated with a dielectric material to generate a discharge in the discharge area between the two electrodes, and this discharge is generated by a laser beam. In a gas laser device as an excitation source, the outside of a first insulating layer made of a silicone rubber insulator that covers the surface of the dielectric of each electrode other than the surface facing the dielectric of the other electrode, A gas laser device characterized by being coated with a second insulating layer made of an inorganic insulating material.