JPH0122996B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode structure in a silent discharge excited gas laser device.

FIG. 1 is a block diagram showing the principle of a silent discharge excited carbon dioxide laser device. In the figure, 1 is a housing, 2A and 2B are a pair of dielectric electrodes made by coating a metal surface with a dielectric material such as glass, 3 is a discharge gap, and 4 is a gas such as CO ₂ , CO, N ₂ , He gas, etc. 5 is a blower, 6 and 7 are total reflection mirrors and partial reflection mirrors for oscillating and amplifying laser light, and 8 is a power source that supplies high frequency and high voltage between the pair of dielectric electrodes 2A and 2B. It is.

In the silent discharge excited carbon dioxide laser device having the above configuration, when a high frequency high voltage is applied from the power supply 8 between the pair of dielectric electrodes 2A and 2B, the discharge current is locally concentrated due to the capacitance ballast effect of the dielectric. A spatially uniform silent discharge with a limited amount of noise occurs. This silent discharge excites the laser medium gas 4 present in the discharge gap 3, causing laser oscillation. The laser light generated by laser oscillation is amplified while traveling back and forth between the total reflection mirror 6 and the partial reflection mirror 7.
A portion of the laser beam is extracted from the partial reflecting mirror 7 as a laser output L. The laser medium gas 4 whose temperature has increased due to the silent discharge is sent to a heat exchanger (not shown) and cooled, and then supplied to the discharge gap 3 again by the blower 5.

FIGS. 2A and 2B are a partial front sectional view and a partial side sectional view showing the structure of a dielectric electrode in a conventional silent discharge excited gas laser device. In each of the above figures, 9 is a metal tube, 10 is a dielectric coated on the surface of the metal tube 9, and the metal tube 9 and the dielectric 10 constitute a dielectric electrode 11. 12 is cooling water that cools the dielectric electrode 11 from inside; 13 and 14 are the inlet and outlet of the cooling water 12, respectively; 15 is a high-frequency, high-voltage supply terminal; This discharge limiting material 16 is made of, for example, an organic insulator and is used to generate a silent discharge in one part and limit the occurrence of silent discharge in other parts.
At the same time, a support portion for the dielectric electrode 11 is also formed. 17 is a filler, and more than half of the upper part of the dielectric electrode 11 is embedded in the discharge limiting material 16;
They are tightly bonded by a filler 17. The dielectric constant of the discharge limiting material 16 is approximately the same as that of the dielectric 10, and the portion of the dielectric electrode 11 covered with the discharge limiting material 16 has a capacitance equal to the thickness of the discharge limiting material 16. Silent discharge is not covered by the discharge limiting material 16 because it is added in series to the capacitance of the dielectric 10 and the capacitance is equivalently smaller than that of the portion of the dielectric electrode 11 that is not covered by the discharge limiting material 16. Dielectric electrode 11
occurs concentrated on the surface of Reference numeral 18 indicates a silent discharge situation. Strictly speaking, weak silent discharge is also generated from the surface of the discharge limiting material 16, and this becomes more noticeable as the applied voltage is increased.

In the structure of the dielectric electrode 11 according to the above-described conventional method, the discharge limiting material 16 that covers the non-discharge portion of the dielectric electrode 11 and limits silent discharge is easy to machine and inexpensive. Organic insulators are usually used. However, since organic insulators have poor discharge resistance, silent discharges that occur from the surface of the dielectric electrode 11 and wrap around to the discharge limiting material 16 and silent discharges that occur from the surface of the discharge limiting material 16 cause heat and electron impact. , discharge limiting material 16
In the process or after the generation of organic gases such as CO, CO ₂ and hydrocarbons through thermal decomposition or combustion reactions of organic compounds contained in the laser medium gas, CO ₂ , CO, N ₂ and trace amounts of O ₂ present in ,
It reacts in a complex manner with O ₃ , NO _{x ,} etc., and the chemical equilibrium state between these gases is disturbed, resulting in a change in the mixed composition of the laser medium gas. In addition, when using silicone rubber for the filling material 17, the filling material 17
However, due to the heat and electron impact of silent discharge, the filling material 17
The Si contained in the laser gas reacts with trace amounts of O ₂ , O _3, etc. present in the laser medium gas, and the O component is consumed in the process of generating SiO _{2 .} Because the chemical equilibrium of CO is disturbed,
The mixed composition of the laser medium gas changes. in general,
The mixed composition of the laser medium gas is set to the optimum value that allows the highest laser output to be obtained in the silent discharge excited carbon dioxide laser device.
As described above, there is a drawback that the laser output naturally decreases due to a change in the mixture composition of the laser medium gas from the optimum value due to the mixing of decomposed gases. Furthermore, in order to compensate for the decrease in laser output due to the contamination of the decomposed gases mentioned above, it is necessary to increase the discharge power or frequently replace the deteriorated laser medium gas with new laser medium gas. There were drawbacks such as a decrease in efficiency due to an increase in discharge power and an increase in running costs due to replacement of the laser medium gas.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it is a discharge limiting material that limits discharge by covering the non-discharging part between a pair of electrodes, which are made by covering a metal electrode with a dielectric material. The surface is coated with an inorganic insulating material that does not generate harmful gases that change the mixed composition of the laser medium gas, which prevents the generation of harmful gases, suppresses the decrease in laser output, and provides long-term stability. The object of the present invention is to provide a silent discharge excited gas laser device that can obtain laser output.

An embodiment of the present invention will be described below with reference to the drawings. 3A and 3B are a partial front sectional view and a partial side sectional view showing the structure of a dielectric electrode in a silent discharge excited gas laser device which is an embodiment of the present invention, and FIGS. Identical parts are indicated using the same reference numerals, and detailed explanation thereof will be omitted.
In each of the above figures, 19 is an inorganic insulator that does not generate harmful gas that changes the mixed composition of the laser medium gas, and this inorganic insulator 19 is the discharge limiting material 16.
The entire surface of the filler 17 and the exposed surface of the filler 17 are covered. The rest of the structure is almost the same as the conventional one shown in FIGS. 2A and 2B.

In the structure of the dielectric electrode 11 according to the present invention described above, when a high frequency high voltage is applied to the pair of dielectric electrodes 11, the discharge limiting material 16, the filler material 17
A strong silent discharge occurs from the surface of the dielectric electrode 11 that is not covered with the inorganic insulator 19, and this strong silent discharge causes the inorganic insulator 1 in the vicinity of the dielectric electrode 11 to
9 surfaces are exposed. In addition, since the dielectric constant of the inorganic insulator 19 is approximately the same as that of the dielectric 10 and the discharge limiting material 16, when a high applied voltage is applied, a weak silent discharge also occurs from the surface of the inorganic insulator 19. do. However, since the discharge limiting material 16 and the filler 17 are coated with the inorganic insulator 19,
There is no exposure to silent discharge. By the way, in the structure of the dielectric electrode 11 of the present invention, inorganic insulation that does not generate harmful gases even when exposed to silent discharge is used as a means to prevent the generation of harmful gases that change the mixed composition of the laser medium gas. Thing 1
9 is coated on each surface of the discharge limiting material 16 and the filling material 17, which are the sources of harmful gases, thereby protecting the discharge limiting material 16 and the filling material 17 from the heat and electron impact of silent discharge. Therefore, no harmful gas is generated, and as a result, the mixed composition of the laser medium gas does not change. The reason why the coated inorganic insulator 19 does not generate harmful gases like organic insulators even when exposed to silent discharge is that inorganic insulators have extremely superior discharge resistance compared to organic insulators, and the heat generated by silent discharge This is because it is very strong against electron bombardment, generates almost no decomposition gas, and does not contain organic gases such as CO, CO ₂ and hydrocarbons that are harmful to the laser medium gas. In addition, inorganic insulator 19
uses an inorganic insulator that does not contain silicon or its compounds, so even when exposed to silent discharge, SiO ₂
Therefore, the mixed composition of the laser medium gas is not changed. As mentioned above,
Since the dielectric electrode 11 of the present invention has a structure that prevents the generation of harmful gases that would change the mixed composition of the laser medium gas, the laser medium gas remains at the optimum mixed composition for the silent discharge excited gas laser device. Therefore, it has the advantage that stable laser output can be obtained without decreasing the laser output. In addition, by preventing the generation of harmful gases, the laser medium gas once sealed can be used for a long period of time without having to be converted to a new laser medium gas or replenished, which reduces the running cost of the laser medium gas. In addition, the effort required to replace the laser medium gas can be saved. Furthermore, since the laser output does not decrease, there is no need to increase the discharge power to compensate for the decrease in laser output, resulting in higher efficiency than conventional devices of this type. In addition, in the dielectric electrode 11 of the present invention, since the surface of the discharge limiting material 17 is coated with an inorganic insulator 19 having excellent discharge resistance, it is possible that the dielectric electrode 11 may be damaged due to manufacturing defects of the dielectric electrode 11 or abnormal circumstances. It has sufficient durability even against locally concentrated high-temperature arc discharge caused by damage to the parts 11 and 11. In addition, the dielectric electrode 11 of the present invention is made of an organic insulator that has poor discharge resistance but is easy to machine and has low material and processing costs, and is fixed to the housing by cutting a groove for embedding the dielectric electrode. It is constructed by drilling screw holes, etc., and coating only the surface exposed to silent discharge with a thin layer of inorganic insulator 19, which has excellent discharge resistance but is difficult to machine, and has high material and processing costs. Therefore, it has the advantage of being inexpensive and easy to manufacture.
That is, it can be said that the dielectric electrode 11 of the present invention makes use of the respective advantages of inorganic insulators and organic insulators at the same time.

FIGS. 4A and 4B are a partial front sectional view and a partial side sectional view showing the structure of a dielectric electrode in a silent discharge excited gas laser device according to another embodiment of the present invention. Dielectric electrode 1 shown in FIGS. 3A and B above
1, the entire surface of the discharge limiting material 16 and filler 17 is coated with an inorganic insulating material 19 that does not generate harmful gases that change the mixed composition of the laser medium gas. The body electrode 11 is configured to cover only the surface near the dielectric electrode 11 that is most exposed to silent discharge, and even with this, the various effects described above can be sufficiently achieved.

Note that as the inorganic insulator 19 that does not generate harmful gases that change the mixed composition of the laser medium gas, it is best to use mica, glass, ceramic, or a composite material thereof that does not contain silicon or its compounds. be.

In addition, the inorganic insulator 19 does not generate harmful gases that change the mixed composition of the laser medium gas.
may be formed into a thin plate and bonded and coated on the entire surface of the discharge limiting material 16 and the filler 17 or on the surface near the dielectric electrode 11 with an adhesive or the like. In addition, a low melting point glass material etc. are used as the discharge limiting material 16 and the filler material 17.
The entire surface of the dielectric electrode 11 or the surface near the dielectric electrode 11 may be melted and coated.

Further, in the above embodiment, a case has been described in which the discharge limiting material 16 is coated with an inorganic insulating material 19 that does not generate harmful gases that change the mixed composition of the laser medium gas. It may be formed by

Further, in the above embodiment, a case where the present invention is applied to a silent discharge excited type carbon dioxide laser device has been described, but the present invention can be sufficiently applied to other gas laser devices, and the same effects as in the above embodiment can be obtained.

As described above, according to the silent discharge excited gas laser device according to the present invention, as the structure of the dielectric electrode, an inorganic insulator that does not generate harmful gases that change the mixed composition of the laser medium gas is used on the surface of the discharge limiting material. In terms of performance, since the structure is coated with
It has various effects such as stabilizing the laser output, improving efficiency, and reducing the running cost of the laser medium gas, as well as being extremely inexpensive and extremely easy to manufacture.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the principle of a silent discharge excited carbon dioxide laser device, and Figures 2 A and B are a partial front cross-sectional view and a partial diagram showing the structure of a dielectric electrode in a conventional silent discharge excited gas laser device. A side sectional view, FIGS. 3A and 3B are a partially front sectional view and a partially side sectional view showing the structure of a dielectric electrode in a silent discharge excited gas laser device, which is an embodiment of the present invention.
Figures A and B are a partial front cross-sectional view and a partial side cross-sectional view showing the structure of a dielectric electrode in a silent discharge excited gas laser device according to another embodiment of the present invention. The smell in the figure is 1... Housing, 2A, 2B, 11...
...Dielectric electrode, 3...Discharge gap, 4...Laser medium gas, 5...Blower, 6...Total reflection mirror, 7...
Partial reflecting mirror, 8...Power supply, 9...Metal tube, 10...
...Dielectric, 12...Cooling water, 13...Inlet, 14
...Exit, 15... Supply terminal, 16... Discharge limiting material, 17... Filling material, 18... Silent discharge status,
19... Inorganic insulator, L... Laser output.
In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. By applying a high frequency and high voltage between a pair of electrodes made of a metal electrode covered with a dielectric material, a silent discharge is generated in the discharge gap between the two electrodes, and a laser medium gas is excited. In a silent discharge excited gas laser device that performs laser oscillation, the surface of the discharge limiting material that limits discharge by covering the non-discharge portions of both electrodes is made of an inorganic material that does not generate harmful gases that change the mixed composition of the laser medium gas. A silent discharge excited gas laser device characterized by being coated with an insulating material. 2. The silent discharge excited gas laser device according to claim 1, wherein the inorganic insulator is formed into a thin plate shape and coated on the surface of the discharge limiting material. 3. The silent discharge excited gas laser device according to claim 1, wherein the discharge limiting material is entirely formed of an inorganic insulating material that does not generate harmful gases that change the mixed composition of the laser medium. . 4. The silent device according to claim 1, characterized in that mica, glass, ceramic, or a composite material thereof is used as the inorganic insulator that does not generate harmful gases that change the mixed composition of the laser medium gas. Discharge excited gas laser device.