JPH05175581A - High repetition pulse laser electrode - Google Patents

Abstract

PURPOSE:To enhance a cooling efficiency by preventing a temperature rise of a high repetition pulse laser electrode. CONSTITUTION:A capillary 12 having about several mm of a diameter is formed longitudinally as a cooling member in a first main electrode 2, and both ends are extended from an opposite surface to the surface opposed to a discharge region main electrode out of the main electrode. Both ends of the capillary 12 extended out of the main electrode are connected to a circulator 14 arranged out of a laser chamber 1 through a tube 13 to form one closed circuit. Insulating fluid to become cooling medium is filled in the capillary 12. The fluid in the capillary 12 is always circulated in the closed circuit by the operation of the circulator 14. The fluid includes, for example, fluorocarbon, insulating oil, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-repetition pulse laser device for oscillating a laser by forcibly circulating a laser gas, and more particularly to a high-repetition pulse laser electrode having an improved discharge part structure. is there.

[0002]

2. Description of the Related Art In general, a high repetition pulse laser device for forcibly circulating a laser gas to oscillate a laser is a position where a pair of main electrodes forming an anode and a cathode face each other in a hermetically sealed container at regular intervals. The laser gas is forcibly circulated between the main electrodes in a direction orthogonal to the laser oscillation direction. Then, the laser gas is generally excited by a glow discharge generated between the pair of main electrodes to oscillate laser light.

FIG. 4 shows an example of a conventional high repetition pulse laser device, and schematically shows a cross section in the direction perpendicular to the optical axis.

That is, the second main electrode 3 (anode) is arranged at a position facing the first main electrode 2 (cathode) arranged in the laser medium in the laser chamber 1 which is a closed container. A plurality of pairs of preionization electrodes 4 and 5 are connected in parallel on both sides of the first main electrode in the longitudinal direction. Further, a plurality of peaking capacitors 6 for charging the main electrode space are arranged outside the closed container, and the two main electrodes 2 and 3 are the peaking capacitors 6 described above.
Is electrically connected via a current return 8 composed of a plurality of rod-shaped metals. Furthermore, the second main electrode 3 is connected to the ground potential outside the laser chamber 1 through the current return 8.

Further, between the two main electrodes 2 and 3 facing each other, the laser gas after the discharge is promptly exchanged, and the laser gas is forced to remove the residual gas mixed with the impurities generated by the laser discharge. Means 9 to circulate mechanically
Due to this, a laser gas flow 10 is generated in the direction of the arrow.

An outline of the operation of the conventional high repetition pulse laser device configured as described above will be described. That is, when the HV pulse is applied from the high repetition pulse power supply 7 to the inside of the laser chamber 1 filled with the laser gas, first,
A current flows through the circuit of HV pulse → preliminary ionization electrode 4 → preliminary ionization electrode 5 → peaking capacitor 6, and the peaking capacitor 6 is charged. At this time, spark discharge occurs in the small gap between the preionization electrodes 4 and 5, and the ultraviolet light generated thereby sparks the space sandwiched between the two main electrodes 2 and 3 as the preelectrode. Then, when the voltage applied to the peaking capacitor 6 reaches the discharge breakdown voltage between the main electrodes 2 and 3, the main discharge starts and laser light is generated in the direction perpendicular to the paper surface.

By the way, in the pulse laser device, H
The energy E injected into the main discharge space when the V pulse is applied between the main discharge electrodes is expressed by the following equation.

E = 1/2 CpV ² Cp: Peaking capacitor capacity V: Charging voltage Since this energy is applied to the main discharge electrode in a short time of several tens of nanoseconds, the energy injected into the discharge part reaches several MW / cc. ..

However, the energy efficiency (output energy / injection energy) of such a discharge excitation type pulse laser is generally as low as about several percent.
That is, most of the injected energy is lost as circuit loss or Joule heat. The heat loss of the implantation energy is transferred to the laser gas through the electrode, and as a result, the temperature of the electrode and the laser gas is rapidly increased.

Such a rise in the temperature of the laser gas causes the gas in the discharge region, which has become high in temperature, to be supplied to the heat exchanger 1 by the gas supply means 9.
The problem is solved by cooling through 1 and feeding fresh laser gas into the discharge area. However, for the locally heated electrode surface, the contact with the gas flow 10 generated by the gas supply means 9 provides the greatest opportunity for heat exchange, so that the cooling effect is very small and the cooling effect is small. Takes time.

[0011]

As described above, in the conventional high repetition pulse laser electrode, the temperature rise of the main discharge electrode caused by the high energy at the time of discharge is several hundred μ Since it is difficult to recover by a few msec, heat is accumulated inside the electrode,
The electrode metal reaches an extremely high temperature state by stacking the number of shots.

Under such a condition, the laser main discharge becomes very unstable due to fluctuations in gas density, scattering of electrode materials, deviation of injection energy, etc., and uniform and stable glow discharge should be ignited. Becomes difficult. Therefore, it is impossible to continuously ignite a stable main discharge during high repetition operation, and as a result, the laser output becomes unstable. Further, when the temperature of the electrode surface becomes high, the consumption of the electrode material and the deterioration of the laser gas are promoted, which also hinders the life extension of the laser.

The present invention has been proposed in order to solve the above-mentioned drawbacks of the prior art, and its purpose is to prevent the temperature rise of the main electrode and to enhance the cooling efficiency of the main electrode to stabilize the temperature. An object of the present invention is to provide an excellent highly repetitive pulse laser electrode capable of obtaining the desired laser output.

[0014]

SUMMARY OF THE INVENTION The present invention is a pair of main electrodes, which are opposed to each other in a closed container, in which a laser gas is circulated between them. Among these, at least one of the main electrodes is provided with a cooling member capable of circulating a cooling medium.

[0015]

In the highly repetitive pulse laser electrode of the present invention having the above-mentioned structure, the main electrode body is always positively cooled by the effect of the cooling medium circulating in the main electrode. The electrode temperature raised by the implantation energy can be promptly lowered, and the temperature rise can be suppressed to the minimum. As a result, stable glow discharge can be obtained even during high repetition operation.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIGS. The same members as those of the conventional type shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, as shown in FIG.
Inside the first main electrode 2 made of a metal such as nickel or aluminum, a thin tube 12 having a diameter of several mm is formed in the longitudinal direction as a cooling member, and both ends thereof face the discharge area of the main electrode. It is drawn out of the main electrode from the surface opposite to the surface. In addition, the thin tube 1 drawn out of the main electrode
Both ends of 2 are connected to a circulator 14 arranged outside the laser chamber 1 via a pipe 13 to form one closed circuit.

The inside of the thin tube 12 is filled with an insulating fluid which serves as a cooling medium. The insulating fluid in the thin tube 12 is constantly circulated in the closed circuit by the action of the circulator 14.

As the insulating fluid, CFC, insulating oil or the like can be used. Further, FIG. 2 is a perspective view showing only the main electrode and its periphery by simplifying the structure of the discharge part of the present embodiment.

The high repetition pulse laser electrode of this embodiment having such a structure operates as described below. That is, when a high pulse voltage (HV pulse) is applied from the high repetition pulse power source 7, the peaking capacitor 6 is charged through the preionization electrodes 4 and 5, and discharge breakdown occurs in the laser gas between the main electrodes 2 and 3. Most of the enormous energy injected into the discharge part is converted into the amount of heat, propagated and emitted to the surroundings.

In this case, in this embodiment, the main electrode 2
Due to the cooling action of the cooling medium flowing inside, the heat is quickly exchanged in the electrode metal part. Thereby, the temperature rise of the main body of the main electrode 2 is suppressed, and even when high repetition operation is continuously performed for a long time, the metal forming the main electrode can maintain a relatively low temperature state. Furthermore, since the temperature rise on the surface of the main electrode is also suppressed, the amount of accumulated heat is less released to the laser gas flow flowing in contact with the surface of the main electrode.

Further, cooling the main electrode body also has a function of suppressing melting, evaporation, sputtering, etc. of the electrode metal generated at a locally high temperature portion of the surface of the main electrode, so that deterioration of the electrode and further metal The contamination of the laser gas due to the scattering can be greatly reduced. This not only contributes to stable ignition of the glow discharge but also extends the life of the laser gas, so that stable laser oscillation can be maintained for a long time.

The present invention is not limited to the above-described embodiment, and for example, a thin tube may be opened inside the main electrode 3 to allow an insulative fluid to flow in, or both the main electrodes 2 and 3 may be introduced. By providing the cooling function, it is possible to further improve the cooling efficiency.

Further, as shown in FIG. 3, two or more thin tubes are passed through the inside of the main electrode to increase the contact area between the cooling medium and the electrode metal, so that a wider area can be efficiently used. Can be cooled. Furthermore, various methods can be selected for the preionization method, the air supply means, the power supply method, the excitation circuit, and the like.

[0025]

As described above, according to the present invention, by providing a cooling member capable of circulating a cooling medium inside at least one of the pair of main electrodes, It is possible to provide an excellent highly repetitive pulsed laser electrode capable of preventing the temperature rise of the main electrode, enhancing the cooling efficiency of the main electrode, and obtaining a stable laser output.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a high repetition pulse laser electrode according to the present invention.

FIG. 2 is a perspective view of a main electrode portion of the embodiment shown in FIG.

FIG. 3 is a perspective view showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the configuration of a conventional high repetition pulse laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser chamber 2 ... 1st main electrode 3 ... 2nd main electrode 4, 5 ... Pre-ionization electrode 6 ... Peaking capacitor 7 ... High repetition pulse power supply 8 ... Current return 9 ... Gas supply means 10 ... Gas flow 11 ... Heat exchanger 12 ... Thin tube 13 ... Piping 14 ... Circulator

Claims (1)

[Claims] 1. A high repetition pulse laser electrode in which a pair of main electrodes are arranged to face each other in a hermetically sealed container, and a laser gas is circulated between the main electrodes, and at least one of the pair of main electrodes is used. A high repetition pulse laser electrode, characterized in that a cooling member capable of circulating a cooling medium is provided inside the main electrode.