JPH02130978A - Pulse laser oscillator - Google Patents

Abstract

PURPOSE:To reduce the load of switches for enlarging the operational regions thereof by a method wherein a specified part of glow discharge energy is fed from a low rate pulse charged condenser while the residual part is fed from high rate pulse charged condenser. CONSTITUTION:A switch 7 is normally opened to charge a condenser (C) 5 through the channel of a high voltage power supply 9, a charge resistor 8, the condenser 5 and ground. The other C13, C14 are not charged to keep the main electrodes 1, 2 at the ground potential. When the switch 7 is closed, the auxiliary ionization electrodes 3b are impressed with the voltage of the C5 through shunt coils 12. The other electrodes 3a being kept at the ground potential, the gaps 4 are subjected to the spark discharge to auxiliary-ionize the laser gas between the main electrodes 1 and 2. On the contrary, when the switches 7, 17 are closed through the intermediary of a controller 18, the charges of respective C5 and C15 charge the C13 and the C14 respectively at high and low current charge rates to cause the glow discharge between the main electrodes 1 and 2 by the total voltage thereof so that the laser gas may be excited to emit laser beams.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a pulsed laser oscillation device, and particularly to its discharge section and power supply configuration.

(Prior art) In discharge excitation type gas lasers, laser oscillation is obtained by generating a spatially uniform glow discharge in the laser gas, but pulsed laser oscillations such as lateral excitation pulsed CO2 lasers and excimer lasers In the device, since the laser gas pressure is above atmospheric pressure and contains gas components with strong electron adhesion, it is difficult to ignite the glow discharge uniformly. It is common to perform ionization and apply a high-speed pulse voltage to the discharge portion to form a glow discharge.

FIG. 5 is an example showing a discharge section structure and an excitation power supply circuit of a conventional pulsed laser oscillation device. (For example, the method shown in Laser Research, Vol. 13, No. 10, p. 814 (198G), etc.) A pair of main electrodes 1.2 are arranged facing each other, and the space surrounded by the main electrodes 1.2 is is charged with laser gas. The main electrode 2 is grounded.

A preliminary ionization electrode 3a is connected to the main electrode 1 and is electrically at the same potential. The pre-ionization electrode 3a and the pre-ionization electrode 3b face each other with a gap 4 in between, and are placed in the laser gas. Pre@[The separating electrode 3b is insulated from the main electrode 1, drawn out from the laser gas, and connected to the capacitors C and 5. One end of the charging inductance 6 is commonly connected to the preliminary ionization electrode 3b and the capacitor C85, and the other end is grounded.

The capacitors C and 5 are grounded via a switch 7 and connected via a charging resistor 8 to a high voltage power supply HV9. A capacitor CblO is connected between the main electrodes 1 and 2. Capacitors and inductances of 0 or more are 1
It is constructed by connecting one or more in parallel. Further, an optical resonator (not shown) is arranged in a direction perpendicular to the plane of the paper.

The operation of the conventional pulsed laser oscillation device configured as described above will be explained. In the initial state, switch 7 is open,
The capacitors C and 5 are charged through the path of high voltage power supply HV9 - charging resistor 8 - capacitor C85 - charging inductance 6 - ground. Since the capacitor cbto is not charged, the main electrode 1 is at ground potential. switch 7
is closed.

Since the potential on the switch 7 side of the capacitor Cs5 becomes the ground potential, the potential on the pre-ionization electrode 3b side of the capacitor Cs5 is applied to the pre-ionization electrode 3b with a polarity opposite to that charged in the capacitor C85. Since the pre-ionization electrode 3b is at ground potential, a high voltage is applied across the gap 4, and a spark discharge occurs in the gap 4. The laser gas between the main electrodes 1.degree. 2 is pre-ionized by ultraviolet light generated by this spark discharge. The charge stored in the capacitor Cs5 is transferred from the switch 7 to the capacitor Cs5 to the pre-ionization electrode 3b to the gap 4.
The flow flows through the path of - secondary ionization electrode 3a - main electrode 1 - capacitor CblO, and the capacitor CblO is charged.The voltage of the capacitor cb10 rises, and the voltage applied between the main electrodes 1 and 2 exceeds the discharge breakdown voltage of the laser gas. When the laser beam reaches f!, a glow group W111 is formed between the main electrodes 1 and 2, the laser gas is excited, and the laser beam is emitted by the action of an optical resonator (not shown). It is emitted in the right direction.

(Problem to be solved by the invention) In such a conventional pulsed laser oscillation device,
It is necessary to set the charging voltage of the capacitor C85 to several tens of kV or higher, and to increase the rate of charging the capacitor Cb10 to shorten the time interval between the occurrence of the pre-ionization discharge formed in the gap 4 and the time interval between the formation of the glow discharge 11. It is. Therefore, the maximum value and time rate of change of the current flowing through the switch 7 are extremely large, which not only limits the types of switches that can be used, but also shortens the life of the switch 7.
Further, the charging voltage could not be increased above the maximum allowable current value and allowable current change rate determined by the characteristics of the switch 7. As described above, since the operational range and types of available switches are limited, it has been difficult to realize operational operations necessary for industrial applications, such as repeated operation and long-life operation.

Therefore, the present invention was proposed in order to eliminate the above-mentioned drawbacks, and its purpose is to provide a pulsed laser oscillation device that significantly reduces the operating duty of the switch, has a wide laser operating range, and has a long life. It's about doing.

[Structure of the invention]

(Means for Solving the Problems) The pulse laser oscillation device of the present invention has a first capacitor and a second capacitor connected in series between a pair of opposing main electrodes, and a connection point of these capacitors is grounded. A closed circuit is formed from one capacitor, a gap, a switch, and a capacitor, the capacitor is connected to a high-voltage power supply, a closed circuit is formed from the second capacitor, a switch, an inductance, and a capacitor, and the capacitor is connected to a high-voltage power source. The device is connected to a high-voltage power source having a polarity opposite to that of the high-voltage power source, and is configured to include a control device that controls the switch and the switch-on time.

(Function) According to the present invention configured as described above, a fixed portion of the total electrical energy supplied to the glow discharge is supplied from the second capacitor charged with a slow pulse.

The remaining energy can be supplied from the first capacitor, which is charged in fast pulses with pre-ionization.

Therefore, the operational responsibility of the switch element can be significantly reduced,
Furthermore, the operating conditions of the pulsed laser oscillation device can be freely selected.

(Example) An example of the present invention will be specifically described below with reference to FIG.

Figure 1 shows the discharge section and excitation power supply circuit. A pair of main electrodes 1
．． 2 are disposed facing each other in an airtight laser chamber filled with laser gas.

A preliminary ionization electrode 3a is connected to the main electrode 1 and is electrically at the same potential. Pre-ionization electrode 3a and pre-ionization electrode 3
b are opposed to each other with a gap 4 in between, and are placed in the laser gas. The pre-ionization electrode 3b is insulated from the main electrode 1 and drawn out from the laser gas, and the 0-shunt coil 12 connected to the shunt coil 12 is connected to the capacitor C, 5 via the switch 7, and one of the capacitors C, 5 is connected to a negative polarity high voltage power supply HV9 via a charging resistor 8, and the other end is grounded. Main electrodes 1 and 2 have capacitors C and 1
3 and a capacitor Cd14 are connected in series, and the connection point of both capacitors is grounded. Main electrode 2 is switch 17
and connected to capacitor Cd5 via inductance 16.

One end of the capacitor Ct15 is connected to a positive high voltage power supply HVA 19 via a charging resistor 8, and the other end is grounded. The main electrode 1.2 is grounded via a high resistance 20. Capacitor Cs5 - Switch 7 - Shunt coil 12 -
Preliminary ionization electrode 3b - gap 4 - secondary ionization electrode 3a - main electrode 1 - capacitor C, L-C-R of the circuit of the path 13
The current period τ that can be obtained is: capacitor C 15 - inductance 16 - switch 17 - main current 2 - capacitor Cd
This is set to be sufficiently short compared to the current cycle τd determined by the LCR of the circuit with 14 paths. High voltage power supply HVA 1
The voltage polarity of 9 is opposite to the voltage polarity of high voltage power supply HV9,
In this embodiment, the polarity is positive, but if the polarity of the high voltage power supply HV9 is negative, the high voltage power supply! 1VA The polarity of 19 is positive.Capacitors, resistances and inductances of 0 or more are 1
It is constructed by connecting one or more in parallel. Further, an optical resonator (not shown) is arranged in a direction perpendicular to the plane of the paper.

The operation of the pulsed laser oscillation device configured as above will be explained. In the initial state, the switch 7 is open, and the capacitor C85 is charged through the path of high voltage power supply HV9, charging resistor 8, capacitor Cs5, and ground. capacitor C,
13 and capacitor Cd14 are not charged, the main current 1.2 is at ground potential. Control unit 5! i
When the switch 17 is closed by the signal from the capacitor Ct15, the charge stored in the capacitor Ct15 is transferred to the capacitor Ct15.
is excited and a laser beam is emitted in a direction perpendicular to the plane of the paper by the action of an optical resonator (not shown). High resistance 20 is main current 1,
It has the effect of stabilizing the potential of 2.

The switching energy of the switch 7 and the switch 17 in the embodiment of the present invention will be described in detail below in comparison with the conventional example. For easy comparison with the conventional example, the capacitance value of capacitor CblO and the series capacitance value of capacitor C, 13 and capacitor Cd14 are equal, and the discharge breakdown voltage between main currents 1 and 2: vb is the minimum voltage of capacitor CP13. Value: vp and capacitor Cd14 (7) Voltage maximum value: Vd (73 The switching energy of the conventional method shown for the case where it is equal to the total value (= Vd - Vp) is Eb
= 1/2・CbVb". The switching energy of this method is shared by switch 7, which is EP = 17.
2・Cpvpz, and the switch 17 voltage distribution becomes Fla=1/2−CdVd”.E,,E
The relationship between d and El) is as shown in the formulas ■ and ■.

At knee, if the capacitance values of capacitor CP13 and capacitor Cd14 are equal, capacitor C, 5 - inductance 16 - switch 17 - main current 2 - capacitor Cd14
The flow capacitor Cd14 is charged through the path. - If the switch 7 is closed by a signal from the control device 18 after a certain period of time has elapsed, the voltage of the capacitor C35 changes to the shunt coil 1.
2 to the preionization electrode 3b.

Since the pre-ionization electrode 3a is at ground potential, a high voltage is applied across the gap 4, and a spark discharge occurs in the gap 4. Current is shunted into the plurality of gaps 4 by the action of the shunt coil 12, and all the gaps 4 generate spark discharge.

The main electrode 1.2 is exposed to the ultraviolet rays generated by this spark discharge.
The laser gas in between is pre-ionized. Furthermore, the charge stored in the capacitor C,15 at this time is the capacitor C85.
- Switch 7 - Shunt coil 12 - Preliminary ionization electrode 3b - Gap 4 - Secondary ionization electrode 3a - Main electrode 1 - Capacitor C
The flow capacitor CP13 is charged along the path P13. This situation is shown in FIG. 2. The time when the switch 17 is closed is t. Then, the voltage of capacitor Cd14:
Ved increases at a rate of change of 1-cos (2πt/τd) at time 0 t.

When switch 7 is closed at
) increases at the rate of change. Due to the action of the control device 1i18, Ved reaches a voltage vd close to the maximum value at time t2, and vcp
The turn-on times t0 and tl of the switch 7 and the switch 17 are adjusted so that VP reaches a value close to the minimum value. The total value of the voltages of capacitor CP13 and capacitor Cd14 (=
VdVp) is applied between the main electrodes 1 and 2, so when this total voltage reaches the discharge breakdown voltage (=Vb) between the main electrodes 1.2, a glow discharge 11 is formed between the main electrodes 1.2, and the laser gas Ep = Ea = 1 / 2 Eb, and the switching energy handled by switch 7 and switch 17 is reduced to 50% of the conventional one. Further, the operating voltage value V of the switch 7, which has a large current change rate, is 1 of the voltage Vb of the conventional method.
/2, and the operating voltage is also 1/2. In this way, the operational responsibility of the switch 7 is significantly reduced. The operable limit of a switch is generally defined by the rate of change of the current flowing under conditions of 0 or more.The period of the current flowing to the switch 17 side is long, so the current rate of change is low. This makes it possible to use semiconductor switches, etc., which have a low upper limit on the rate of current change.

Conversely, if the capacitor capacity on the switch 17 side is made larger than the capacitor capacity of the switch 7.

This is because the rate of change in current on the switch 7 side can be kept low.

In this method, the operating responsibilities of the switch can be set according to the switch being used, which not only expands the selection of usable switches, but also increases the operational efficiency. It is easy to change the voltage and operating energy, and the degree of freedom in circuit configuration is greater than in conventional systems.

The above embodiments are examples of application to ultraviolet pre-ionization type pulsed lasers, but it goes without saying that the application is not limited to ultraviolet pre-ionization type pulsed lasers, but can also be applied to X-ray pre-ionization type pulse lasers, corona pre-ionization type pulsed lasers, etc. .

Next, another embodiment of the present invention will be explained in detail based on FIG.

Figure 3 shows the discharge section and excitation power supply circuit, and the electrode configuration is
Same as figure. A capacitor C, 1 is connected between the main electrodes 1 and 2.
3 and a capacitor Cd14 are connected in series, and the connection point of both capacitors is grounded.The zero shunt coil 12 is connected to a capacitor C85 via a saturable reactor 23.
One end of the capacitor C,5 is connected to the first secondary winding 22-1 of the transformer 22, and the other end is grounded. Main electrode 2
is the second secondary winding 22 of the transformer 22 via the rectifier 21
-2 is connected. Also.

The main electrode 1.2 is grounded via a high resistance 20.

The primary winding of the transformer 22 forms a closed circuit with a capacitor Cd5 and a switch element 25, and the capacitor Ct15 is connected to a high voltage power supply HV9 via a charging resistor 8.

The polarities of the two secondary windings of the transformer 22 are configured such that the voltage polarity on the high voltage side is the opposite polarity.
One or more of the above capacitors, resistors, and inductances are connected in parallel. Also,
An optical resonator (not shown) is arranged in a direction perpendicular to the plane of the paper.

The operation of the pulsed laser oscillation device configured as above is explained below.
This will be explained with reference to FIG. 3 and 4vI4.

In FIG. 3, the switch cable 25 is open in the initial state, and the high voltage power supply HV9 - the charging resistor 8 - the capacitor Ct
The capacitor Ct15 is charged through the 15-ground path. Since the capacitors C and 13 and the capacitor Cd14 are not charged and are connected to the high resistance 20, the main electrodes 1 and 2 are at ground potential.

Control device i! When switch element 25 is closed by a signal from 1g, the charge stored in capacitor ctis is transferred from capacitor ctis - switch element 25 - 1 of transformer 22.
The voltage flows in the path of the secondary winding, and a voltage is generated in the secondary winding of the transformer 22. The positive voltage generated in the second secondary winding 22-2 of the transformer 22 charges the capacitor Cd14 to a positive polarity via the rectifier 21. The voltage Vcd between the terminals of the capacitor Cd14 decreases by 1/1 after the switch element 25 is turned on.
The maximum value is reached at time t after two cycles, and the action of the rectifier 21 prevents the current from flowing backward from the capacitor Cd14 to the transformer 22. However, Ved is the capacitor Cd
14 and the high resistance 20.

On the other hand, the negative voltage generated in the first secondary winding 22-1 of the transformer 22 charges the capacitor C,5, and the capacitor Cg5
The voltage vcg is 1/ after the switch element 25 is turned on.
The maximum value is reached at time t, two cycles later. If the saturation voltage of the saturable reactor 23 is set to the maximum value We'll of vcs, the saturable reactor 23 will be saturated at time t2,
The impedance drops rapidly and the voltage of capacitor C85 is applied to shunt coil 12. This voltage is applied to the pre-ionization electrode 3b, and since the pre-ionization type i3a is at ground potential,
A high voltage is applied across the gap 4, and a spark discharge occurs in the gap 4. Current is shunted into the plurality of gaps 4 by the action of the shunt coil 12, and all the gaps 4 generate spark discharge.

The main electrode 1.2 is exposed to the ultraviolet rays generated by this spark discharge.
The laser gas in between is pre-ionized. In this process, the charges stored in the capacitor C,5 are: capacitor Cs5 - saturable reactor 23 - shunt coil 12 - pre-ionization electrode 3b
- Gap 4 - Secondary ionization electrode 3a - Main electrode 1 - Capacitor CP13 is charged through the flow path, and this period is between capacitor Cs5 and capacitor C.
, 13 and the sum of the inductance of the saturable reactor 23 at saturation and the inductance of the shunt coil 12, and is significantly shortened compared to the change period of Vcd and VO2. Therefore, capacitor C,
The voltage VCp of 13 changes sharply as shown in FIG. Between the main electrodes 1 and 2 are capacitors C and 13 and capacitor Cd1.
4 is added, and when the total voltage reaches the discharge breakdown voltage between the main electrodes 1 and 2 at time t, a glow discharge 11 is formed between the main electrodes 1 and 2,
Vcd and ■. , becomes 0. A laser gas is excited by the glow discharge 11, and a laser beam is emitted in a direction perpendicular to the paper surface by the action of an optical resonator (not shown). The high resistance 20 also has the effect of stabilizing the potential of the main electrode 1.2.

The switching current frequency of the switching element 25 is Vcd
and ves, so the current change rate can be kept very low. Therefore, the switch element 25
The operational responsibility of 0 and above is significantly reduced, and it becomes possible to use semiconductor switches with low service limit current change rate.
In this case, the capacitance values of the capacitors 14 and 14 are almost the same, but by changing the capacitance value of each capacitor, the applied voltage waveform can be freely controlled, making it easy to change the operating voltage and operating energy of the circuit. It has a greater degree of freedom in circuit configuration than conventional methods, so it can be easily used in conditions where the discharge breakdown voltage is high or when it is desired to greatly increase the discharge input energy.

〔Effect of the invention〕

According to the present invention configured as described above, a certain part of the total electrical energy supplied to the glow discharge is supplied from a capacitor that has been charged with slow pulses, and the remaining energy is supplied from a capacitor that has been charged with fast pulses while performing pre-ionization. Because you can.

The switching energy of each switch can be significantly reduced, and the life of the switch can be significantly extended.

In addition, since the capacitor capacity and pulse charging voltage can be freely combined, the peak value and rate of change of the switching current can also be freely selected. It will also be possible to use it. Furthermore, since the degree of freedom in one circuit configuration is high, it is easy to provide a laser oscillation device with high output and long life.

4. Brief explanation of the 1i21 plane FIG. 1 is a circuit diagram showing an embodiment of the pulse laser oscillation device of the present invention, FIG. 2 is a waveform diagram explaining the present invention in detail, and FIG. 3 is a pulse FIG. 4 is a circuit diagram showing another embodiment of the laser oscillation device, FIG. 4 is a waveform diagram explaining the operation of another embodiment of the present invention, and FIG. 5 is a circuit diagram showing a conventional pulsed laser oscillation device.

DESCRIPTION OF SYMBOLS 1... Main current, 2... Main current, 3... Spark discharge pin, 3a... Pre-ionization electrode, 3b... Pre-ionization electrode, 4... Gap, 5... Capacitor C3 , 6... Charging inductance.

7...Switch, 8...Charging resistor, 9...High voltage power supply HV.

10... Capacitor Cb, 11... Glow discharge.

12... Shunt coil, 13... Capacitor CP.

14... Capacitor Cd, 15... Capacitor Ct, 16... Inductance, 17... Switch.

18...Control device, 19...High voltage power supply OVA.

20... High resistance, 21... Rectifier, 22...
transformer.

22-1...first secondary winding of transformer 22, 22-2
... Second secondary winding of transformer 22, 23... Saturable reactor, 24... Inductance.

25...Switch element.

Agent: Patent Attorney Noriyuki Chika Ken Daikomaru No. figure Vcd No. figure No. figure

Claims (1)

[Claims] In a pulsed laser oscillation device in which a capacitor is connected between a pair of opposing main electrodes, the capacitor is connected in series with a first capacitor and a second capacitor, and the first capacitor and the second capacitor are connected in series. The connection point of the capacitor is grounded, the first capacitor forms a closed circuit with the gap, the first switch, and the third capacitor, a DC power source is connected to the third capacitor, and the second capacitor is connected to the ground. The capacitor forms a closed circuit with a second switch, an inductance, and a fourth capacitor, and a DC power source with a polarity opposite to the DC power source is connected to the fourth capacitor. 1. A pulse laser oscillation device comprising a control device for turning on a switch.