JPH10223957A - Excimer laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the compactness, reliability, and oscillating efficiency of an excimer laser device which utilizes corona discharge for the preliminary ionization of a laser gas. SOLUTION: In an excimer laser device provided with a corona discharge generating electrode, the corona discharge generating electrode has an auxiliary electrode 16 inserted into a dielectric pipe 15, and a corona electrode 8 which is formed on the external surface of the pipe 15, in such a way that the electrode 8 is faced oppositely to the electrode 16 and the pipe 15 is extended from each electrode and airtightly fixed to the wall 1 of a laser tube through a shield ring 17. Then, the dielectric strength of a voltage introducing section is improved by covering a conductor 18 which is connected to the auxiliary electrode 16 through the pipe 15 with an insulating coating film 19 having a high dielectric strength against feed-through voltage and not forming a creeping section in the laser tube having a low dielectric strength, but in an air section having a high dielectric strength. Therefore, a high voltage can be impressed upon the auxiliary electrode 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an excimer laser device for performing preionization by corona discharge.

[0002]

2. Description of the Related Art As shown in a schematic sectional view of FIG.
A pair of main discharge electrodes 2 and 3 are arranged in parallel with each other in the oscillation optical axis direction (perpendicular to the plane of the drawing). A pulse voltage is applied to generate a main discharge in a discharge region d between the main discharge electrodes 2 and 3, thereby performing laser excitation.

In order to pre-ionize the laser gas in the discharge region d prior to the main discharge, a pre-ionization is performed along one main discharge electrode 3 (electrode on the ground potential side in the figure) of the pair of main discharge electrodes 2 and 3. An ionizing discharge generating means is provided.
In the illustrated example, the preliminary ionization discharge generating means is a hollow pipe (hereinafter, referred to as a “dielectric pipe”) 5 formed of a dielectric.
A rod-shaped body 7 in which a first electrode (hereinafter, referred to as “auxiliary electrode”) 6 made of a conductor is inserted into a hollow portion of the rod-shaped body, and a conductor arranged in contact with the outer surface of the rod-shaped body 7 and extending in the axial direction. A second electrode (hereinafter, referred to as “corona electrode”) 8 constitutes a corona discharge generating electrode, and is arranged along the main discharge electrode 3.

[0005] As shown in FIG. 5, the auxiliary electrode 6 has an end protruding beyond the dielectric pipe 5, and the protruding end is connected to the conductor 1.
2 is connected to a conductor 11 of a voltage supply terminal 9 having a bushing structure composed of a normal conductor 11 penetrating the inside of an insulator 10 on the end face of the laser tube 1 or the like. It is connected to, for example, the high voltage side of the pulse voltage source 4 via the terminal 9. On the other hand, the dielectric pipe 5
Is connected to the low voltage side (ground potential side) of the pulse voltage source 4 having the same potential as the main discharge electrode 3.

When a high-voltage pulse voltage is applied between the auxiliary electrode 6 and the corona electrode 8, a corona discharge is generated at a contact point between the corona electrode 8 and the outer surface of the dielectric pipe 5, and the corona discharge is generated. The generated ultraviolet light is applied to the discharge region d as shown by an arrow A, and the laser gas in the discharge region d is pre-ionized.

[0006]

By the way, the laser gas has a very low electric insulation strength (1/4) as compared with air.
Degree), an end of a corona electrode 8 formed on the outer surface of the dielectric pipe 5 and an auxiliary electrode 6 protruding from the hollow pipe 5.
Creepage discharge along the outer surface of the dielectric pipe 5 easily occurs between the dielectric pipe 5 and the insulation between the conductor 11 protruding from the insulator 10 inside the laser tube 1 of the voltage supply terminal 9 and the end face of the laser tube 1. Creepage discharge along the outer surface of the body 10 is likely to occur.
Therefore, a high voltage cannot be applied, and sufficient preliminary ionization cannot be performed.

In order to avoid the creeping discharge, the length of the dielectric pipe 5 is increased, and the end of the corona electrode 8 is connected to the dielectric pipe 5.
If the distance between the auxiliary electrodes 6 protruding from the electrode is increased and the length of the insulator 10 of the voltage supply terminal 9 inside the laser tube 1 is increased to make the creepage length very long, this can be avoided to some extent. Increasing the length not only increases the size of the device, but also increases the length of the resonator of the laser light, resulting in a significant decrease in oscillation efficiency. (Generally, in a laser oscillator having the same gain length, the length of the resonator increases. It is known that the oscillation efficiency is reduced.)

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a compact, highly reliable excimer laser device having high oscillation efficiency, which utilizes corona discharge for preliminary ionization of a laser gas. Aim.

[0009]

The object of the present invention is to provide an excimer laser device comprising a pair of main discharge electrodes in a laser tube and a corona discharge generating electrode arranged along the main discharge electrodes. The corona discharge generating electrode has an auxiliary electrode inserted inside the dielectric pipe and a corona electrode formed on the outer surface of the dielectric pipe facing the auxiliary electrode, and the dielectric pipe is connected to each of the electrodes. Extending from the laser tube wall and hermetically fixed to the laser tube wall, and a conductive wire passing through the dielectric pipe and connected to the auxiliary electrode is coated with an insulating coating having a high penetration dielectric strength. The excimer laser device is characterized in that the creepage distance is sufficiently increased in the dielectric strength with respect to the applied voltage.

According to the above aspect of the present invention, the auxiliary electrode includes:
The whole is surrounded by the dielectric pipe, and the dielectric pipe is airtightly fixed to the laser tube wall apart from the corona electrode and the auxiliary electrode, so that the creepage insulating portion is not formed in the laser tube with low electric insulation strength and the dielectric strength is high. Formed in the atmosphere. Therefore, creeping discharge is prevented at the short creeping portion. The conductor that applies the high-voltage pulse to the auxiliary electrode is inserted into the dielectric pipe, and the surroundings are coated with insulation that has a high dielectric strength, so a high voltage can be applied by the auxiliary electrode. become.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the configuration of the embodiment according to the present invention. The same parts as those in FIGS. 4 and 5 are denoted by the same reference numerals, and redundant description will be omitted.

The corona discharge generating electrode of the gas laser device according to the present invention shown in FIG. 1 has an auxiliary electrode 16 made of a conductor inserted into a hollow portion of a dielectric pipe 15 made of a dielectric material of alumina ceramics. And a corona electrode 8 made of a conductor arranged in the axial direction in contact with the outer surface of the dielectric pipe 15 facing the main discharge electrode 3.
It is arranged along.

The dielectric pipe 15 is formed to extend longer than the auxiliary electrode 16, and its end face is air-tightly fixed to the side wall of the laser tube 1 via a shield ring 17 such as an O-ring or rubber packing. The auxiliary electrode 16 inserted in the hollow portion of the dielectric pipe 15 is entirely surrounded by the dielectric pipe 15, and a pulse 18 as shown in FIG. A high voltage is applied from the voltage source 4. The conductive wire 18 has an insulating coating 19 having a sufficiently high penetration dielectric strength against an applied voltage.
Is given.

The auxiliary electrode 16 to which a high voltage is applied is stopped at a required length, and the creepage formed between the dielectric pipe 15 extending therefrom and the end face is sufficiently high with respect to the applied voltage. It has a creepage withstand voltage. Therefore, a high voltage can be applied by the auxiliary electrode 16 to enhance the preliminary ionization effect.

A dielectric pipe 1 according to the embodiment shown in FIG.
5 is formed in a straight line and the end face thereof is fixed to the side wall of the laser tube 1. However, when the laser emission window or the like cannot be formed linearly due to an obstacle, as shown in FIG. Dielectric pipe 25 made of ceramic dielectric
Is bent to avoid obstacles.

That is, in the corona discharge generating electrode of the embodiment shown in FIG. 2, an auxiliary electrode 26 made of a conductor is inserted into a hollow portion of a dielectric pipe 25 formed of a dielectric material of alumina ceramics. A corona electrode 8 made of a conductor is provided extending in the axial direction in contact with the outer surface of the opposed dielectric pipe 25, and is arranged along the main discharge electrode 3.

The dielectric pipe 25 is formed so as to extend longer than the auxiliary electrode 16 and is formed by bending the extension. The end face is provided with a shield ring 17 such as an O-ring or rubber packing on the side wall of the laser tube 1. The airtight is fixed through.

Also in this embodiment, the dielectric pipe 2
The entire surface of the auxiliary electrode 16 inserted into the hollow portion of the dielectric pipe 25 is surrounded by a dielectric pipe 25.
A high voltage is applied from a pulse voltage source 4 as shown in FIG. Conductor 18
Is provided with an insulating garment 19 having sufficiently high penetration dielectric strength with respect to the applied voltage. The corona discharge generating electrode configured as described above can enjoy the same function and effect as the corona discharge generating electrode shown in FIG.

In the embodiment shown in FIG. 3, a gap between the dielectric pipe 15 (or 25) and the conductive wire 18 provided with the insulating coating 19 is filled with an insulator 20 such as silicon rubber. A partial discharge is prevented from occurring in a gap between the pipe 15 (or 25) and the conductor 18 provided with the insulating coating 19. With this configuration, the reliability and the life of the voltage introducing unit are improved.

It should be noted that the corona discharge generating electrode may be arranged along any side of the pair of main discharge electrodes, and the polarity of the high voltage is also arbitrary. Although the present invention has a structure of a voltage supply unit for generating corona discharge, a similar effect can be obtained in a voltage supply unit of silent discharge by adopting a similar structure. In the above embodiment, alumina ceramics is used as the dielectric, but any material having a withstand voltage against corrosive laser gas and discharge may be used. Further, the wall surface for hermetically fixing the dielectric pipe is usually made of metal, but may be converted to an insulator.

[0021]

As described in detail above, according to the present invention,
Creepage insulation is not formed in the laser tube with low electrical insulation strength, and it is formed in the atmosphere part with high dielectric strength, so creeping discharge can be prevented with a short creepage distance, and high voltage can be applied by the auxiliary electrode. In addition, it is possible to obtain a compact and highly reliable excimer laser device with enhanced preliminary ionization effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a corona discharge generating electrode according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another configuration of the corona discharge generating electrode according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing still another configuration of the corona discharge generating electrode according to the embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a configuration of a main part of an excimer laser device having a corona discharge generating electrode.

FIG. 5 is a cross-sectional view showing a configuration of a conventional corona discharge generating electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser tube 2, 3 Main discharge electrode 4 Pulse power supply 8 Corona electrode 15, 25 Dielectric pipe 16 Auxiliary electrode 17 Shield ring 18 Conductive wire 19 Insulation clothing 20 Insulator

Claims (1)

[Claims] 1. An excimer laser device comprising: a pair of main discharge electrodes in a laser tube; and a corona discharge generation electrode disposed along the main discharge electrodes, wherein the corona discharge generation electrode is provided inside a dielectric pipe. And a corona electrode formed on the outer surface of the dielectric pipe facing the auxiliary electrode, extending the dielectric pipe from each of the electrodes and hermetically fixing the laser pipe wall. In addition, a conductor passing through the dielectric pipe and connected to the auxiliary electrode is coated with an insulating coating having a high penetration dielectric strength, and the creepage distance between the auxiliary electrode and the laser tube wall is set to a dielectric strength with respect to an applied voltage. An excimer laser device characterized by sufficiently increasing the value.