JPH0716050B2 - Gas laser equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a gas laser device for generating a laser beam by exciting a gas laser medium with a main electrode composed of a cathode and an anode.

(Prior Art) For example, a gas laser device such as a TEACO ₂ laser or an excimer laser in which laser light is emitted in a direction orthogonal to the discharge direction is configured as shown in FIG. That is, reference numeral 1 in the figure denotes a laser tube having a gas laser medium accommodated therein. In the laser tube 1, a cathode 2 and an anode 3 which form a main electrode are arranged so as to face each other with a space in the vertical direction. Upper pin electrodes 5 are provided on both sides of the cathode 2 via peaking capacitors 4, and lower pin electrodes 6 are provided on both sides of the anode 3 so as to face the upper pin electrodes 5.

The cathode 2, anode 3, upper pin electrode 5 and lower pin electrode 6 are each connected to a high voltage power supply 7. When this high-voltage power supply 7 is turned on and electric energy is supplied between the cathode 2 and the anode 3, first, a discharge is generated between the upper pin electrode 5 and the lower pin electrode 6, and the cathode 2 and the anode 3 are discharged. The discharge space between the two is preionized. When the preliminary ionization in the discharge space portion is sufficiently advanced, the main discharge (glow discharge) is ignited between the cathode 2 and the anode 3 to excite the gas laser medium, and the laser light of the laser tube 1 orthogonal to the discharge direction. It is radiated along the axial direction.

Although not shown, a high-reflecting mirror and an output mirror that form an optical resonator are arranged at both ends of the laser tube 1 in the axial direction. Therefore, when the laser light emitted between the cathode 2 and the anode 3 is amplified by the optical resonator and reaches a predetermined intensity, it is oscillated from the output mirror.
Further, in the laser tube 1, a blower 9 for circulating the gas laser medium and a heat exchanger 8 for keeping the temperature of the gas laser medium constant are provided.

Conventionally, as the cathode 2 and the anode 3, Chang-shaped electrodes as shown in FIGS. 5 and 6 have been used so as to form an equal electric field for stably generating a main discharge. . That is, when the width direction of the electrodes 2 and 3 is X, the longitudinal direction is Y, and the height direction is Z, the cross-sectional shape is X = u + k · cos v · sinhu (1) Formula Z = v + k · sin v · coshu It is determined by the equation (2), and a uniform electric field can be obtained in the X direction. In the above equations,
u is the value of the line of electric force, k is the parameter that determines the shape, v
Is a value determined by k, and can be calculated by the equation: v = cos ⁻¹ (−k) (3).

On the other hand, if the Chang-type formula is applied also to the Y direction, which is the longitudinal direction of the electrodes 2 and 3, the value in the Z direction gradually decreases from the central portion in the longitudinal direction toward both ends.
The main discharge is ignited only at the central portions of the electrodes 2 and 3 in the longitudinal direction. Therefore, normally, as shown in FIG. 5, the value of Z is made constant in a wide area with respect to the Y direction, and "D" is set.
The range of the end portion indicated by is set to the Chan-shaped shape defined by the equations (1) and (2). That is, "D"
Is the width of the electrodes 2 and 3 along the X direction.
The curvature m was set to 1/2 and the end of the curvature m along the Y direction was set to be the same as the curvature m ′ along the X direction.

However, in such electrodes 2 and 3, since the dimension of "D" is very small with respect to the entire length in the Y direction, the electric field is concentrated and stabilized at the point d ₀ where the dimension in the Z direction changes rapidly. There were times when glow discharge could not be obtained. For example, in the standard value, the size of “D” is as small as about 20 mm in an electrode with a total length of 600 mm, and the size change in the Z direction at the point d ₀ is rapid, so that a large electric field concentration occurs at the point d _0. It was easy.

When the laser operation is performed using the electrodes 2 and 3 as described above, when the voltage applied to the electrodes 2 and 3 is low, the operation is relatively stable, but the applied voltage is increased and injected into the discharge space. Increasing the applied energy causes the laser energy to decrease above a certain value as shown by curve a in FIG. This is because, as described above, the electric field concentrates at the point d ₀ at the ends of the electrodes 2 and 3, and arc discharge occurs.

(Problems to be Solved by the Invention) As described above, since the electrodes of the conventional gas laser device employ the chan shape also in the widthwise direction at the ends in the longitudinal direction, the height dimension at that end is measured. In some cases, the electric field concentration suddenly changes, which causes arc discharge due to electric field concentration.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a gas laser device in which arc discharge due to electric field concentration is less likely to occur at the longitudinal ends of electrodes. .

[Structure of the Invention] (Means and Actions for Solving the Problems) In order to solve the above problems, the invention is directed to a laser tube in which a gas laser medium is housed, and a width which is provided in the laser tube so as to face each other with a space therebetween. To excite the gas laser medium by supplying a main electrode composed of a cathode and an anode, the main electrode of which is formed in a shape whose cross-sectional shape along the direction makes the separated and opposed spaces into a substantially even electric field, and by supplying electric energy to the main electrode. A high-voltage power supply for generating a main discharge of, at least one of the cathode and the anode, the cross-sectional shape along the longitudinal direction at the longitudinal end is a curved surface gentler than the cross-sectional shape along the width direction. It is characterized by being formed.

According to the electrode having such a structure, the change in the height dimension at the longitudinal end portion becomes gentler than that in the width direction, so that the arc discharge due to the electric field concentration occurs at the longitudinal end portion. It gets harder.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The overall structure of the gas laser device is the same as that shown in FIG.
Since the shapes of and are different from the conventional ones, only the shape will be described.

That is, although the cathode 2 and the anode 3 of the present invention have the same cross-sectional shape along the X direction, which is the width direction, as in the conventional case, the shape of the end portion 10 in the Y direction, which is the longitudinal direction, is: The curvature M along the Y direction is set smaller than the curvature m ′ along the width direction. That is, the curved surface along the longitudinal direction of the end portion 10 is set to be a gentle curve as compared with the curved surface along the width direction. As a result, the height dimension Z
The length E in the Y direction of the end portion 10 in which the dimension in the direction changes can be made longer than the length D in the case where a Chang-shaped curvature similar to that in the X direction is applied to the end portion as in the conventional case. .

The shapes of the ends 10 of the cathode 2 and the anode 3 are set as follows. That is, the length E of the end portion 10 is set within the range of 5 to 10% of the total length of the electrodes 2 and 3. Then, assuming that the coordinates of the point E ₀ where the dimension in the Z direction starts to change in the Y direction and the Z direction are (0, 0), the length E is divided into _four, and the respective points at that time are designated E _{0 to} E ₄ . To do. Also, the electrodes 2, 3 at point E ₀
If the height (height at the location other than the end portion 10) as a Z _0, the height of the E ₁ is The height of E ₂ is The height of E ₃ is The height of E ₄ is Z ₀ . Therefore, the coordinates in the Y and Z directions at the points E _{0 to} E ₄ are E ₀ (0,0), It becomes E ₄ (E, Z ₀ ).

The above-mentioned five points E _{0 to} E ₄ are approximated to a polynomial of a second degree or higher by the method of least squares. For example, in an electrode with a total length (Y dimension) of 720 mm and a height (Z direction) of 20 mm, if "E" is 10% of the total length, the coordinates of each point are E ₀ (0,0), E ₁ ( 18,1), E ₂ (36,
3.3), E ₃ (54,8) and E ₄ (72,20). When this is approximated by the cubic method using the least squares method, Z = −5.42 × 10 ⁻² ＋ 0.113Y−3.88 × 10 ⁻³ Y ² ＋ 8.573 × 10
^-5 Y ³ … Equation (3). Therefore, if the cross-sectional shape at E _{0 to} E ₄ is determined by the above formula (3), the end portions 10 of the electrodes 2 and 3 can be formed to have a curved surface along the Y direction that is gentler than that of the Chang type. .

Thus, if the end portions 10 of the electrodes 2 and 3 are formed in a curved surface having a gentler curve than in the width direction, the change in the Z direction at the E ₀ point also becomes gentle, so that the E ₀ point of the end portion 10 is set. It becomes difficult for the electric field to concentrate. As a result, it is possible to obtain a higher laser energy as compared with the curve a as shown by the curve b in FIG. That is, it is possible to form the electrodes 2 and 3 in which arc discharge is unlikely to occur even when the applied voltage is increased.

The present invention is not limited to the above-mentioned one embodiment and can be variously modified. For example, in the above-described one embodiment, both ends of the pair of electrodes have a curvature larger than that of the Chan type, but the present invention may be applied to only one of the electrodes.

Further, the electrode may have a cross-sectional shape along the width direction not only in a Chang shape, but also in a cylindrical shape, a Rogowski shape, an Ernst shape, or the like. Good.

EFFECTS OF THE INVENTION As described above, according to the present invention, the cross-sectional shape along the longitudinal direction at the longitudinal end portion of at least one of the cathode and the anode is a curved surface gentler than the cross-sectional shape along the width direction. Formed. Therefore, the change in shape along the longitudinal direction of the end portion of the electrode becomes gentler than in the conventional case.
Arc discharge due to electric field concentration is less likely to occur.

[Brief description of drawings]

FIG. 1 is a side view of an end portion of an electrode showing an embodiment of the present invention, FIG. 2 is a perspective view of the same, FIG. 3 is a configuration diagram of a general gas laser device, and FIG. 4 is a voltage applied to the electrode. And FIG. 5 is a side view of a conventional electrode, and FIG. 6 is a sectional view along the width direction. 1 ... Laser tube, 2 ... Cathode, 3 ... Anode, 7 ... High-voltage power supply, 10 ... End of electrode.

Claims (1)

[Claims] 1. A laser tube in which a gas laser medium is housed, and a cross-sectional shape along the width direction, which is arranged in the laser tube so as to be opposed to each other with a space therebetween, are formed into a shape in which an electric field having a substantially uniform electric field is formed. At least one of the cathode and the anode, and a high-voltage power source for supplying electric energy to the main electrode to generate a main discharge for exciting the gas laser medium. The gas laser device is characterized in that the cross-sectional shape along the longitudinal direction at the end portion in the longitudinal direction is formed into a curved surface with a gentler curve than the cross-sectional shape along the width direction.