JPH07297472A - Pulsed gas laser device - Google Patents

Abstract

PURPOSE:To make a primary capacitor to generate strong arc discharging during the period of uniform pre-ionization and in the initial stage of pre- ionization by making the voltage applied across a gap for pre-ionization from the primary capacitor to steeply rise by eliminating the influence of a stray capacitance on the cable connecting the primary capacitor to a secondary capacitor. CONSTITUTION:A magnetic switch 12 is connected between the tip of a cable 15, one end of which is connected to a primary capacitor 13, and a feeder conductor 6 connected to a secondary capacitor 5 in a laser chamber l and the charging coil 14 of the primary capacitor is connected to the conductor 6. Since the primary capacitor is charged with a stray capacitance between the period from the turning on of a switching element 11 to the saturation of the switch 12, the cable 15 is not affected by the stray capacitance when the capacitance of the primary capacitor is transferred to the secondary capacitor 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse gas laser device, and more particularly to a pulse gas laser device of the ultraviolet automatic preionization capacity transfer type.

[0002]

2. Description of the Related Art As is well known, a pulse gas laser device of this type is provided with a plurality of pairs of preionization gaps in the vicinity of a main electrode which generates a discharge for exciting a laser gas so that a primary capacitor is connected to a secondary capacitor. At the time of capacity shift, ultraviolet light is generated by arc discharge between the preionization gaps, and this ultraviolet light irradiates the laser gas in the laser gap to perform preionization.

FIG. 3 shows the conventional configuration. Reference numeral 1 denotes a laser chamber, which is filled with laser gas,
2 and 3 are main electrodes, 4 is a plurality of gaps for pre-ionization arranged in the vicinity of the main electrodes 2 and 3 and arranged along the longitudinal direction thereof, and 5 is connected in series to each gap 4. The next capacitor. Reference numeral 6 denotes a feeding conductor, to which the main electrode 2 and one end of each secondary capacitor 5 are connected. Reference numeral 7 denotes a substrate, to which the main electrode 3 and one end of each gap 4 are connected. Reference numeral 8 is an insulator that insulates the power supply conductor 6 from the laser chamber 1.

Reference numeral 10 denotes a primary circuit box in which a high-speed switching element 11 such as a thyratron, a magnetic switch 12 composed of a saturable reactor, a primary capacitor 13 and a charging coil 14 are housed. The primary capacitor 13 is connected to the power feeding conductor 6 via the power feeding cable 15. The primary circuit box 10 is grounded like the laser chamber 1. The configuration example in the figure is a system in which power is supplied to the secondary capacitor 5 and the main electrodes 2 and 3 from both ends of the power supply conductor 6.

FIG. 4 is a circuit diagram of the configuration of FIG. The operation will be described with reference to FIG. 1. The DC high voltage power supply 16 charges the primary capacitor 13 via the charging coil 14. After this charging, the switch element 11 is turned on to start the operation for laser generation. Here, the magnetic switch 12 is used for stable switching operation of the switch element 11, protection of the switch element, and prolongation of life, and this is connected in series to the switch element 11.

That is, during a few 10 ns in a relatively high impedance state (a state in which the switch element 11 is not completely turned on) immediately after the switch element 11 is turned on, a large current is prevented from flowing through the switch element 11. The magnetic switch 12 blocks for several tens of ns.

After the switch element 11 is turned on and the magnetic switch 12 is saturated and turned on, the voltage of the primary capacitor 13 is applied to the gap 4 via the power feeding cable 15. L represents the inductance of the circuit from the primary capacitor 13 to the secondary capacitor 5 and the gap 4.

By applying a voltage to the gearups 4 in this way, dielectric breakdown occurs between the gearups 4 and preionization is started, and the secondary capacitor 5 is pulse-charged by the primary capacitor 13 to the secondary capacitor 5. And capacity transfer is started. At the time when this capacitance transfer is almost completed, the voltage between the main electrodes 2 and 3 causes a dielectric breakdown due to the voltage of the secondary capacitor 5, and the discharge for laser excitation is started between the main electrodes 2 and 3. Then, laser oscillation occurs.

However, in this structure, the stray capacitance CS1 exists in the circuit from the primary capacitor 13 to the secondary capacitor 5, and the stray capacitance CS2 also exists in the circuit of the gap 4. In this case stray capacitance CS
Since the capacity of the secondary capacitor 5 is sufficiently larger than that of 1,
When the switch element 11 and the magnetic switch 12 are turned on, before the secondary capacitor 5 is charged, the stray capacitance C
S1 and CS2 will be charged.

Therefore, the voltage of the primary capacitor 13 is applied due to the time constant due to both stray capacitances and the circuit inductance L, and the rise of the voltage becomes blunt. The time constant τ at that time is τ1≈π√ {L (C
S1 + CS2)}, which is about several tens to 100 ns. Since the voltage applied to the gaps 4 is dulled in this manner, the lighting times among the gaps 4 vary, and temporally uniform preionization cannot be obtained.

Further, in order to enhance the preionization effect, it is important to increase the breakdown voltage of the gap 4 and generate a strong arc discharge at the initial lighting of the gap 4 to obtain a strong ultraviolet light. When the voltage applied to the gap 4 is blunt, a strong arc discharge cannot be generated at the beginning of lighting of the gap 4.

[0012]

SUMMARY OF THE INVENTION According to the present invention, even when there is a stray capacitance in the circuit from the primary capacitor to the secondary capacitor, the voltage applied to the gap for preionization from the primary capacitor rises sharply. The purpose is to generate a uniform preionization and a strong arc discharge at the initial stage of preionization.

[0013]

According to the present invention, a magnetic switch is connected between a tip of a cable, one end of which is connected to a primary capacitor, and a feeding conductor, to which a secondary capacitor in a laser chamber is connected. In addition, a charging coil for the primary capacitor is connected to the feeding conductor.

[0014]

In this structure, the stray capacitance including the primary capacitor and the cable is not insulated by the magnetic switch. Therefore, after the primary capacitor is charged, the stray capacitance including the cable is charged in advance during the time from when the switching element is turned on to when the magnetic switch is saturated due to the capacitance transfer from the primary capacitor.

After that, the primary capacitor is discharged so as to charge the secondary capacitor when the switching element is turned on, but the stray capacitance is not affected during this discharge. This makes it possible to make the rise of the voltage to the gap for preionization steep.

[0016]

Embodiments of the present invention will be described with reference to FIGS. In addition, the portions denoted by the same reference numerals as those in FIGS. 3 and 4 indicate the same or corresponding portions. According to the invention, the magnetic switch 12 is connected outside the laser chamber 1 between the end of the feed cable 15 and the feed conductor 6. The charging coil 14 is also connected to the power supply conductor 6.

FIG. 2 is a circuit diagram of FIG. 1, in which a DC high voltage power source 16 is connected to a primary capacitor 13 and a power feeding cable 1.
The circuit inductance L of 5, the magnetic switch 12 and the charging coil 14 are connected in series. A series circuit including the gap 4 and the secondary capacitor 5 is connected in parallel to the charging coil 14. Connecting the main electrodes 1 and 2 in parallel to this series circuit is the same as the conventional configuration.

After the primary capacitor 13 is charged by the DC high voltage power supply 16, the switch element 11 is turned on. In this configuration, the primary capacitor 13 and the stray capacitance CS1
There is no magnetic switch 12 between the two, and therefore the magnetic switch 12 is in a conductive state even when it is not saturated. As described above, after the switching element 11 is turned on, when the magnetic switch 12 is not saturated, the capacitance transfer from the primary capacitor 13 to the stray capacitance CS1 is started, and the stray capacitance CS1 is charged. After the stray capacitance CS1 is charged, the magnetic switch 12 is saturated by the voltage applied to the stray capacitance CS1. Charging of the secondary capacitor 5 is started after the magnetic switch 12 is saturated, but the stray capacitance CS1 is already charged at this point due to the above operation.

In this case, there is no influence of the stray capacitance CS1 and the voltage of the gap 4 rises sharply. The time constant τ2 at this time is τ2≈π√ (L · CS2). The circuit constants in the circuit examples shown in FIG. 4 and FIG.
The capacitance of the primary capacitor 13 = 40 nF, the capacitance of the secondary capacitor 5 = 30 nF, the inductance of the charging coil 14 = 600 nH, the stray capacitance CS1 = 100 pF, and the stray capacitance CS2 = 50 pF. In the configurations shown in FIGS. 3 and 4, the time constant τ1 of the voltage rise of the gap 4 is about 30.
nS, but with the configuration shown in FIGS. 1 and 2, the time constant τ2
Becomes about 17 nS, and the rise of the voltage can be steep to nearly double as compared with the conventional configuration.

[0020]

As described above, according to the present invention, the rising of the voltage from the primary capacitor applied to the gap for preionization can be made steeper than that of the conventional configuration, and the preliminary It is possible to reduce the temporal variation of lighting in the ionization gap, and to improve the breakdown voltage of the gap, and thus to obtain a strong preliminary ionization.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of FIG.

FIG. 3 is a sectional view of a conventional example.

FIG. 4 is a circuit diagram of FIG.

[Explanation of symbols]

 1 Laser Chamber 2 Main Electrode 3 Main Electrode 4 Gap for Preionization 5 Secondary Capacitor 6 Feeding Conductor 11 Switch Element 12 Magnetic Switch 13 Primary Capacitor 14 Charging Coil 15 Feeding Cable 16 DC High Voltage Power Supply

Claims (1)

[Claims] 1. A main electrode for generating a discharge for exciting a laser gas, a plurality of gaps for pre-ionization arranged near the main electrode, and a series connection to each of the gaps inside the laser chamber. A secondary capacitor, and a power supply conductor to which a series circuit of the main electrode and the gap and the secondary capacitor is connected, the primary circuit box, a primary capacitor charged by a DC high voltage power supply, and a power supply A switch element for starting pulse charging of the secondary capacitor by the primary capacitor via a cable is provided, and between the power supply cable and the power supply conductor, for protecting the switch element, from a saturable reactor. A pulse switch with a magnetic switch, and a charging coil for the primary capacitor connected to the feeding conductor. User equipment.