JPS6321885A - Discharge type gas laser - Google Patents

Abstract

PURPOSE:To form a wide uniform electric field region between discharge electrodes by forming the surface of one electrode distant from a peaking capacitor in a recess shape, and forming the surface of another electrode in a projecting shape to form the surface shape of both the electrodes asymmetrically. CONSTITUTION:The top surface of a discharge electrode 3 more distant from a peaking capacitor 4 than another discharge electrodes 2 is formed in a recess shape, and the top surface of the other electrode 2 is formed in a projecting shape. Accordingly, the surface shapes of the electrodes 2 and 3 are asymmetrical. Thus, equipotential lines near the surfaces of the electrodes are drawn to the electrodes as designated by broken lines. Thus, the central part along the lateral direction of the electrode is formed widely in parallel on the surface. Thus, the uniform electric field region on the surfaces of the electrodes becomes wider than the conventional configuration.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a discharge type gas laser device.

(Conventional technology) As is well known, this type of discharge type gas laser device.

For example, an excimer laser device is configured to fill a pair of discharge electrodes with laser gas and generate a glow discharge between the discharge electrodes to output a laser beam.

FIG. 2 shows a circuit diagram of a conventional device of this kind, in which a pair of discharge electrodes 2 and 3 are arranged inside the laser tube 1, and a series circuit of a peaking capacitor 4 and a pre-ionization electrode 5 is connected in parallel. They are arranged on both sides of the discharge electrodes 2 and 3. Further, the laser tube 1 is filled with laser gas.

Initially, the switch element 6 (eg, thyratron) is turned off, and in this state, the capacitor 8 is charged by the voltage from the power supply terminal 7 via the reactor 9. When the switching element 6 is turned on when charged to a predetermined voltage, the capacitor 8 is discharged via the peaking capacitor 4 and the pre-ionization electrode 5.

At this time, the discharge at the pre-ionization electrode 5 generates ultraviolet rays, which ionizes the laser gas between the discharge electrodes 2 and 3. Then peaking capacitor 4 is charged,
Radiation f$ between discharge electrodes 2 and 3! When the voltage is reached, a main discharge starts between the discharge electrodes 2 and 3. This discharge generates an ultraviolet laser.

FIG. 3 shows the internal structure of a conventional laser tube 1, which is composed of a large number of secondary electrodes on both sides of discharge electrodes 2 and 3, and a peaking capacitor 4 arranged in series with the electrodes.

By the way, for this kind of laser generation.

It is necessary that a uniform glow discharge be generated between the discharge electrodes 2 and 3. Therefore, normally 53cm is used as this kind of discharge electrode.
As shown in the figure, it is common to use one with a semicylindrical shape with a convex surface.

A Chang shape is usually used as this surface shape, and this shape is obtained based on an analytical solution to obtain an equal electric field distribution between the discharge electrodes 2 and 3.

However, this analytical solution is for the case where no other components exist around the discharge electrode. Actually, as mentioned above, there is a pre-ionization electrode 5. Because of the presence of the peaking capacitor 4, it is not possible to obtain a theoretically uniform electric field distribution with such a surface shape.

In particular, if there is a capacitor such as peaking capacitor 4 in the surrounding area, the equipotential line is likely to be drawn into the capacitor, as shown by the dotted line in Figure 9, because its electrodes have a certain potential. The electric field near both sides of the discharge electrode 3 becomes extremely weak.

Since the electric field distribution is strongly influenced by the surrounding components, the actual uniform electric field region is usually narrower than the theoretical value. If the uniform electric field region becomes narrow in this way, the discharge region becomes narrower and the laser oscillation pattern is also reduced.

(Problems to be Solved by the Invention) This invention solves the problem even if there are capacitors and other components around the discharge electrode that generates the discharge for laser generation.
The purpose is to avoid the influence of these and to form a wide uniform electric field region between the discharge electrodes.

(Means for Solving the Problems) This invention provides a surface discharge electrode with a concave surface on the side away from the peaking capacitor, and a convex surface on the other surface. It is characterized by having an asymmetrical shape, thereby forming a wide uniform electric field region between the discharge electrodes.

(Example) An embodiment of the invention will be described with reference to FIG.

Note that parts given the same reference numerals as in FIG. 3 indicate the same or corresponding parts. According to this invention, discharge electrodes 2, 3
The surface of the discharge electrode 3 on the side away from the peaking capacitor 4 has a concave shape. Also, the other discharge electrode 2
The surface has a convex shape.

This makes the surface shapes of the surface discharge electrodes 2 and 3 asymmetrical.

With this configuration, the equipotential lines near the surface of each discharge electrode are drawn into the discharge electrode, as shown by the dotted lines in the figure, and therefore, in the central part along the width direction of the discharge electrode, the equipotential lines near the surface of the discharge electrode are drawn broadly parallel to the surface. It becomes a shape. As a result, the uniform electric field area on the surface of the discharge electrode becomes wider than in the conventional configuration.

In this case, it is preferable that the specific surface curvature of the discharge electrodes be determined numerically by a computer, taking into account the spacing between the discharge electrodes, the positional relationship of surrounding components, and all other factors. Further, although the surface shape of the discharge electrode 2 is made convex, it does not have to be a chang shape, and it is preferable to numerically calculate this using a computer to obtain the optimum shape.

(Effects of the Invention) As detailed above, according to the present invention, the uniform electric field region on the surface of the discharge electrode can be made sufficiently wider than before, and therefore the laser oscillation pattern can be reliably expanded. Moreover, even with a compact discharge electrode, a large laser oscillation pattern can be obtained.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a discharge circuit diagram, and FIG. 3 is a front view showing a conventional example.

Claims (1)

[Claims] A pair of discharge electrodes for generating a glow discharge that excites the laser gas, a pre-ionization electrode placed on both sides of the discharge electrode, and a peaking capacitor connected in series to the pre-ionization electrode are placed inside the laser tube. A discharge type gas laser device is provided in which the surface of the discharge electrode on the side remote from the peaking capacitor has a concave shape, and the surface of the other side has a convex shape.