JPH0590683A - Discharge excitation laser device - Google Patents

Abstract

(57) [Abstract] [Purpose] Pre-ionization is strongly carried out and the number of pre-ionization electrons is increased to achieve high output, high efficiency and high repetition rate of the discharge excitation laser device. [Structure] One main electrode is composed of an aperture electrode 2
One main electrode 1, 2, a dielectric 3, which is arranged so as to be in close contact with the surface of the open electrode 2 opposite to the other main electrode 1, and the dielectric 3 is opposed to the open electrode with the dielectric interposed therebetween and the dielectric A high voltage pulse generation circuit 6 for charging the excitation capacitor 5 and a third electrode 4 arranged so as to be in close contact with the excitation electrode, two main electrodes and an excitation capacitor 5 connected in parallel to the dielectric. ,
A conductor 9 that is in close contact with the dielectric is provided on a portion other than the contact surface between the dielectric and the aperture electrode, and a conductor 10 that is in close contact with the dielectric is provided at a portion other than the contact surface between the dielectric and the third electrode. Then, the conductor provided on the side of the aperture electrode is connected to the aperture electrode, and the conductor provided on the side of the third electrode is connected to the third electrode.

Description

Detailed Description of the Invention

[0001]

This invention relates to a discharge pump laser device,
In particular, the present invention relates to the structure of a preionization part used for an excimer laser, a TEA-CO ₂ laser, or the like that generates laser light by pulsed discharge excitation among gas lasers.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a conventional typical discharge excitation laser device disclosed in, for example, Japanese Patent Laid-Open No. 61-90486, particularly a discharge corona preionization type discharge excitation laser device. In the figure, 1 and 2 are first and second main electrodes which are arranged so as to face each other in a laser gas, and the second main electrode is an aperture electrode in which a large number of through holes are provided in a metal plate. Is. 3 is a dielectric provided on the side opposite to the first main electrode of the apertured electrode 2 so as to be in contact with the apertured electrode, and 4 is disposed so as to face the apertured electrode 2 and sandwich the dielectric 3. The third electrode, 5 is an excitation capacitor connected in parallel to the first and second main electrodes, and 6 is a high voltage pulse generation circuit for performing pulse charging on the excitation capacitor 5. Further, 7 is a creeping corona discharge generated on the dielectric surface of the apertures provided in the aperture electrodes, and 8 is an ultraviolet ray generated by the creeping corona discharge.

Next, the operation of this device will be described. By the operation of the high voltage pulse generation circuit 6, the excitation capacitor 5
However, since the excitation capacitor 5 is connected in parallel with the main electrodes 1 and 2, the charging voltage of the excitation capacitor is also applied between the main electrodes 1 and 2, and this voltage is the main discharge. If the dielectric breakdown strength of the laser gas between the electrodes is exceeded,
A discharge is formed between the main discharges 1 and 2. However,
In order to form a uniform glow-like discharge for exciting the laser gas between the main discharge electrodes, pre-ionization is performed before the discharge is formed between the main discharge electrodes, so that the laser gas between the main discharge electrodes is evenly distributed. And it is necessary to generate abundant preionization electrons. By the way, in the creeping corona preionization type discharge excitation laser device shown here, the metal portion of the apertured electrode 2, the third electrode 4, and the dielectric 3 sandwiched between them.
Form a capacitor, and this capacitor is electrically connected in parallel with the exciting capacitor 5, so that this capacitor is also charged in parallel with the exciting capacitor. On the other hand, in the open portion of the open electrode 2, an electric field is generated on the dielectric surface by the voltage applied between the open electrode 2 and the third electrode 4. When the breakdown electric field strength of the corona discharge is exceeded, a creeping corona discharge occurs, and the ultraviolet rays generated from this creeping corona discharge preionize the laser gas between the main electrodes 1 and 2 prior to the main discharge, and evenly distribute in the laser gas. Since abundant preionization electrons are generated, a uniform glow discharge is formed between the main electrodes 1 and 2.

Now, in order to generate sufficient preionization electrons in the laser gas, it is necessary to generate a strong creeping corona discharge on the dielectric surface of the aperture of the aperture electrode. Fig. 7 shows the details of the creeping corona preionization part. It has already been mentioned that a large number of holes are formed in the hole of the hole electrode, and the creeping corona discharge occurs on the dielectric surface of the hole. However, an electric field is also generated on the surface of the dielectric that is not in contact with the apertured electrode or the third electrode, and the creeping corona discharge caused by this is experimentally confirmed. This happens on the back side of the apertured electrode, so
It does not contribute to preionization of the main discharge space at all. On the other hand, in the open part, the part where the hole is not open, and the metal part in which the conductive path parts for the main discharge current and the preionization current, which are provided on both sides of the open part, are in contact with the dielectric, A capacitor is formed between them.

FIG. 8 is an equivalent circuit diagram of a creeping corona preionization type discharge pump laser device. In the figure, C _E is the exciting capacitor 5, C ₁ is the capacitance of the capacitor formed by the metal part of the apertured electrode 2 and the third electrode 4 being in close contact with the dielectric 3, and C ₂ is the open capacitor. Capacitance of virtual capacitor generated by creeping corona discharge at the hole portion of the hole portion, C ₃ is a virtual capacitor formed by creeping corona discharge generated on the surface of the dielectric other than the hole of the opening portion Is the capacitance of. Here, G is a discharge gap for simulating a surface corona discharge,
L ₁ is the inductance between the excitation capacitor and the preionization unit, respectively. L ₂ is a stray inductance existing in a current transfer loop between the capacitor C ₁ existing between the aperture electrode and the third electrode and the virtual capacitors C ₂ and C ₃ created by the surface corona discharge. is there.

The operation of this circuit will be described. When the high voltage pulse generator starts charging the excitation capacitor C _E , it also charges the capacitor C _{1 of the} preionization unit connected in parallel with C _E, and the dielectric surface not adhered to the metal is exposed. An electric field is generated. This electric field is the discharge breakdown strength of G,
That is, when the breakdown strength of the creeping corona discharge is exceeded, the G switch is short-circuited, and the charges stored in C _E and C ₁ flow into C ₂ and C ₃ . However, the excitation capacitor C
_Since the inductance L ₁ of the circuit from _E to the preionization parts C ₁ , C ₂ and C ₃ is as large as several 100 nH, the charge inflow amount flowing from C _E to C ₂ or C ₃ to form a surface corona discharge is , C ₁ and C ₂ and C ₃ are smaller than the charge inflow amount and can be ignored. Therefore, according to this equivalent circuit, the current forming the creeping corona discharge, that is, the peak value I _{P0 of the} current flowing into C ₂ and C ₃ is expressed by the following equation. I _P0 = V ₀ * (C _T / L ₂ ) ^0.5 ... 1 where V ₀ is C ₁ at the time when the discharge gap G is destroyed.
Charging voltage, C _T is the combined capacity of C ₁ , C ₂ and C ₃ , and is represented by C _T = (C ₁ * (C ₂ + C ₃ )) / (C ₁ + C ₂ + C ₃ ) ... 2 To be done. By the way, as described above, the current flowing through C ₃ forms a creeping corona discharge generated on the back side of the aperture electrode, but the ultraviolet rays thereof do not reach the laser gas between the main discharge electrodes. After all, it is the current flowing to C _{2 of} I _P0 that contributes to preionization, and the peak value I _{PP of the} current is I _PP = I _P0 * C ₂ / (C ₂ + C ₃ ) ... 3 Desired. Since the aperture ratio of the aperture electrode used in a normal discharge excitation laser device is about 50%, C ₁ and C ₂
The capacitance of C is almost equal, while C ₃ is determined by the area and thickness of the surface corona discharge that spreads on the surface of the dielectric, and is approximately ten times that of C ₁ and C ₂ experimentally. , the _{10C 1 = 10C 2 = C 3} ··· 4. That is, it can be seen from Equations 3 and 4 that about 10% of the current flowing out of C ₁ flows into the creeping corona discharge at the opening, which is useful as a source of ultraviolet rays for preionizing the laser gas.

[0007]

Since the conventional discharge pumped laser device is constructed as described above, 10 minutes of the electric charge stored in the dielectric material sandwiched by the metal part of the apertured electrode and the third electrode. No. 1 contributes to the creeping corona discharge in the aperture that is useful for preionization, and the number of preionization electrons is small, leading to a decrease in laser output, efficiency, and limitation of repetition frequency.

The present invention has been made in order to solve the above-mentioned problems. It strongly performs preionization and increases the number of preionization electrons to increase the output, efficiency and efficiency of the discharge excitation laser device. The purpose is to make it repeatable.

[0009]

In the discharge excitation laser device according to the present invention, the dielectric used for the preionization part is covered with a conductor other than the part in contact with the aperture electrode and the third electrode.

[0010]

In the discharge-pumped laser device according to the present invention, the dielectric electrode used for the preionization portion is covered with the conductor except the portion in contact with the aperture electrode and the third electrode, so as to flow into the aperture portion of the aperture electrode. By increasing the creeping corona discharge current and generating strong ultraviolet rays, it is possible to increase the number of preionization electrons and to achieve high output, high efficiency, and high repetition of the discharge excitation laser device.

[0011]

EXAMPLES Example 1. FIG. 1 is a block diagram showing a discharge excitation laser device according to an embodiment of the present invention. In the figure,
The same reference numerals as those in FIG. 6 indicate the same or corresponding portions. In the figure, 9 is a conductor provided on the side of the aperture of the dielectric, 1
Reference numeral 0 is a conductor provided on the third electrode side.

Next, the operation of this embodiment will be described.
In order to form a uniform glow-like discharge required to excite the laser gas between the main discharge electrodes, pre-ionization is performed before the discharge is formed between the main discharge electrodes, and uniform discharge is performed over the entire laser gas between the main discharge electrodes. In addition, it is necessary to generate abundant preionization electrons, and in a discharge corona preionization type discharge excitation laser device, the ultraviolet rays generated from the creeping corona discharge generated on the dielectric surface at the opening of the opening electrode 2 are spared. Generating ionizing electrons, the metal part of the apertured electrode sandwiching the dielectric and the third
It has already been described that the current flowing out of the capacitor composed of the electrodes of (1) and (2) described above flows in to generate a creeping corona discharge in the opening portion of the opening electrode and becomes a source of ultraviolet rays for pre-ionizing the laser gas. In this invention,
A conductor is provided on the part of the dielectric other than the hole electrode on the side of the hole electrode and on the part of the dielectric other than the third electrode on the side of the third electrode so as to be in close contact with the dielectric. Is electrically connected to the aperture electrode and the third electrode to form a capacitor. Assuming that this capacitor is C ₄ , as shown in FIG. 2, the capacity of the capacitor, which is the source of the current flowing to generate the creeping corona discharge, is obtained by adding C ₄ to C ₁ described in the conventional example,
_It becomes ₁ + C ₄ , which can be increased as compared with the conventional discharge excitation laser device. On the other hand, as a result, the area C ₃ where the creeping corona discharge occurs other than the openings becomes smaller.
That is, the creeping corona discharge portion C ₃ other than the openings in the description of the conventional example is covered with a conductor and replaced by the capacitor C ₄ , and the region of the creeping corona discharge indicated by C ₃ is now shown to facilitate the calculation. Can be considered to be C ₃ + C ₄ = constant ... 5. Therefore, the peak value I _PP of the current to C ₂ which actually contributes to preionization is I _PP = V ₀ * (C _T '/ L ₂ ) ^0.5 * C ₂ / (C ₂ + C ₃ ) ... 6 Here, C _T 'is the combined capacity of C ₁ , C ₂ , C ₃ and C ₄ , and C _T ' = ((C ₁ + C ₄ ) * (C ₂ + C ₃ )) / (C ₁ + C ₂ + C ₃ + C ₄ ) ... 7 is obtained. Further, by substituting Equations 5 and 7 into Equation 6, I _PP = V ₀ * C ₂ * (L ₂ * (C ₁ + C ₂ + C ₃ + C ₄ )) ^−0.5 * ((C ₁ + C ₄ ) / (C ₂ + C ₃ )) ^0.5 ... 8 is an expression representing the peak value I _PP of the current to C ₂ that actually contributes to preionization.

FIG. 3 shows the calculation result of I _PP obtained by the equation (8), which is standardized with 1 in the case of C ₄ = 0 in the conventional example. Thus, according to the present invention,
The current I _PP that flows to generate the surface corona discharge in the aperture of the aperture electrode can be dramatically increased, and the number of preionization electrons in the laser gas is also greatly increased accordingly. In particular, by covering C ₄ / C ₂ of 5 or more, that is, by covering the area of the opening 5 times or more of the dielectric surface area with a conductor, this effect becomes extremely remarkable, and the output and efficiency of the discharge excitation laser device are improved. Moreover, the repetition frequency is also improved.

Example 2. FIG. 4 is a block diagram showing a discharge excitation laser device according to another embodiment of the present invention. FIG. 5 is a vertical cross-sectional configuration diagram showing a side surface of the discharge pumped laser device of FIG. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts. Although a U-shaped dielectric is used as the dielectric in the first embodiment, a cylindrical dielectric is used in the present embodiment. In this case, as shown in FIG. 5, in order to prevent a short circuit due to discharge between the open electrode side and the third electrode side, as in the U-shaped dielectric, at both ends of the cylindrical dielectric, Although there is a portion without a conductor, as shown in FIG.
In the circumferential direction of the dielectric, as shown, it is not necessary to provide a partial no conductor, it is possible to cover the inner wall surface and outer wall surface of the dielectric in all conductors, greater C _4, C
₃ can be smaller. As a result, the number of preliminary ionization electrons can be further increased, and the laser performance is further improved.

[0015]

As described above, according to the present invention, the portion of the dielectric other than the apertured electrode on the apertured electrode side, and the third portion.
Since a conductor is also provided on the electrode side other than the third electrode on the side of the electrode so as to be in close contact with the dielectric, and these conductors are electrically connected to the aperture electrode and the third electrode, respectively,
A strong creeping corona discharge is generated in the aperture of the aperture electrode, and the number of preionizing electrons in the laser gas is increased accordingly, so that the output and efficiency of the laser can be improved, and the repetition frequency can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a discharge excitation laser device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an equivalent circuit of a preionization section in the discharge excitation laser device according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a preionization part current in the discharge excitation laser device according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing a discharge excitation laser device according to a second embodiment of the present invention.

FIG. 5 is a vertical cross-sectional configuration diagram showing a side surface of a discharge pump laser device according to a second embodiment of the present invention with a part thereof cut away.

FIG. 6 is a configuration diagram showing a conventional discharge excitation laser device.

FIG. 7 is a perspective view showing a state of creeping corona discharge in a preionization part of a conventional discharge excitation laser device.

FIG. 8 is a circuit diagram showing an equivalent circuit of a preionization section in a conventional discharge excitation laser device.

[Explanation of symbols]

 1 First Main Electrode 2 Second Main Electrode 3 Dielectric 4 Third Electrode 5 Excitation Capacitor 6 High Voltage Pulse Generator 9 Conductor on Opening Electrode Side 10 Conductor on Third Electrode Side

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruhiko Nagai 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Central Research Laboratory

Claims (1)

[Claims] 1. A first main electrode and a second main electrode, which are arranged to face each other in a laser gas, and at least one main electrode is composed of an apertured electrode in which a large number of through holes are provided in a metal plate, A dielectric body disposed so as to be in close contact with the surface of the apertured electrode opposite to the other main electrode, so as to face the apertured electrode with the dielectric body sandwiched therebetween and to be in close contact with the dielectric body. A third electrode, a first and a second main electrode arranged on the substrate, an exciting capacitor connected in parallel with the dielectric, and a high-voltage pulse generation for pulse-wise charging the exciting capacitor. In a discharge excitation laser device including a circuit, a conductor that is in close contact with the dielectric is provided on a portion other than the contact surface between the dielectric and the aperture electrode and the contact surface between the dielectric and the third electrode. The conductor placed on the side of the open electrode with respect to the dielectric A discharge excitation laser device, characterized in that, in addition to being connected to the open electrode, a conductor provided on the third electrode side with respect to the dielectric is connected to the third electrode.