JP2001144348A - High-voltage pulse generator for laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser high-voltage pulse generator, where the difference between its outputs, when it starts operating and at the other time when it is in usual operation is small, and a laser output can always be efficiently taken out. SOLUTION: A laser high-voltage pulse generator is equipped with at least a magnetic pulse compression circuit 20, composed of a saturable inductor and a capacitor and dipped into an insulating cooling medium 22, where a temperature detector 26 which detects the temperature of the cooling medium 22, a heater 27 which heats the cooling medium 22 direct or through the intermediary of a heat exchanger medium, and a temperature control means 28 which keeps the cooling medium 22 in a prescribed range of temperature by controlling the operation of the heater 27 or the flow rate of the heat exchange medium, based on the detection result of the temperature detector 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage pulse generator for a laser, and more particularly to temperature control of a high-voltage pulse generator for exciting a laser medium in a gas laser such as an excimer laser. .

[0002]

2. Description of the Related Art For example, a gas laser device such as an excimer laser device is provided with a high voltage pulse generator for exciting a laser medium. Normally, it is necessary to perform cooling in such a high-voltage generating section of the gas laser device in order to suppress heat generation during continuous operation (for example, Japanese Patent Laid-Open No. 10-80157). As this cooling method, 20
Normally, cooling water of about ° C. is flowed at a constant rate of several liters / minute through fins immersed in insulating refrigerant in a tank. In this method, immediately after the start of operation, the temperature of the circuit components (capacitor, saturable inductance) is around 20 ° C., which is the same as that of the cooling water, and rises rapidly with the start of the operation. A steady state is reached at about ° C. As described above, in the conventional high-voltage pulse generator for a gas laser device, before and after the operation starts, the temperature is increased from 20 ° C. to 30 ° C.
Temperature difference. As a result, the constants of the circuit components change, and the voltage output from the solid-state pulse power supply changes, resulting in a change in the laser output.

FIG. 7 illustrates the relationship between the temperature and the laser output of an ArF excimer laser device. As shown in FIG.
Compared to the case of 20 ° C. immediately after the start of operation,
When the temperature is from 50 ° C. to 50 ° C., an output rise of about 3 mJ occurs. This is because the output voltage and the output energy change as a result of the change in the circuit constant due to the temperature change. for that reason,
In the case of the constant charging voltage operation, a sharp output fluctuation is caused as shown in FIG.

In the case of the operation shown in FIGS. 7 and 8, when the temperature of the above-mentioned circuit component is 40.degree. C. to 50.degree. C., the laser output reaches a peak. However, if the laser output peaks when the temperature of the circuit component is 20 ° C. by adjusting the circuit constants, the output will suddenly decrease sharply.

A case is considered in which a conventional gas laser device such as an excimer laser device is used in an operation (burst operation) in which the laser device is operated for a fixed time while performing constant output control, and then paused for a certain time. The constant output control means that the laser output, which decreases with the deterioration of the laser gas, is maintained at a constant value by controlling the charging voltage of the high-voltage pulse generator and gradually increasing the charging voltage. When the upper limit is reached, the laser gas is partially or entirely replaced.

Here, it is assumed that the circuit constant is adjusted so that the laser output reaches a peak in a temperature range higher than the temperature immediately after the operation of the circuit component starts.

In this case, since the temperature of the circuit components is low immediately after the start of the laser operation, the charging voltage of the high-voltage pulse generator becomes high in order to set the laser output to a certain value.
Then, as the temperature of the circuit components increases, the laser output becomes larger than a certain value if the charging voltage is maintained immediately after the start of the operation, so that the charging voltage is reduced.

That is, in the burst operation,
Since the temperature of the circuit components decreases during the suspension period, the constant output control is always started with the charging voltage being high when the laser operation is restarted.

Here, immediately after the laser gas exchange,
Since the laser gas has not deteriorated, the charging voltage may be increased only in accordance with the decrease in the temperature of the circuit component, and there is a sufficient margin up to the upper limit of the charging voltage. However, with the deterioration of the laser gas, it is necessary to increase the charging voltage not only for the temperature of the circuit components but also for the deterioration of the laser gas, and there is no room for the upper limit of the charging voltage. come.

That is, in the conventional output control in the gas laser apparatus, the control of the charging voltage of the high-voltage pulse generator is performed not only by the influence of the deterioration of the laser gas but also by the influence of the temperature change of the circuit parts. In general, there has been a situation where the gas life is shortened by the effect of the temperature change of the circuit components.

[0011]

As described above, the conventional gas laser device such as an excimer laser device has a problem that the output difference between the time immediately after the start of the operation after the restart or after the suspension period and the time of the steady operation is large. The reason is that the temperature difference between the high-voltage pulse generator immediately after the start of the operation and during the steady operation is large.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has as its object to reduce the output difference between immediately after the start of operation and during steady-state operation, and to always efficiently extract laser output. To provide a high-voltage pulse generator for use.

[0013]

According to the present invention, there is provided a high voltage pulse generator for a laser according to the present invention, wherein at least a saturable inductance and a capacitor constituting a magnetic pulse compression circuit are immersed in an insulating refrigerant. In the voltage pulse generator, a temperature detecting means for detecting the temperature of the refrigerant, a heat exchange medium for exchanging heat with the refrigerant, a heating means for heating the refrigerant directly or via the heat exchange medium, Temperature control means for controlling the operation of the heating means or the flow rate of the heat exchange medium based on the detection result of the means to control the temperature of the refrigerant within a predetermined temperature range. Things.

In this case, the temperature control means is configured so that the temperature of the refrigerant is controlled to be within a predetermined temperature range by the heating means before the laser oscillation operation is started or during the pause period. Is desirable.

Further, the heating means may be constituted by a fan for forcibly circulating the refrigerant.

In the present invention, a temperature detecting means for detecting the temperature of the refrigerant, a heat exchange medium for exchanging heat with the refrigerant, a heating means for heating the refrigerant directly or via the heat exchange medium,
Temperature control means for controlling the operation of the heating means or the flow rate of the heat exchange medium based on the detection result of the temperature detection means to thereby control the temperature of the refrigerant within a predetermined temperature range. At about the same time, the temperature of the device sharply rises to near the operating temperature, at which point the laser oscillation operation starts, and after the operation starts, it is possible to extract the maximum laser output. In addition, even during a pause period between burst operations in which the operation is paused for a predetermined time after the operation for a predetermined time, the temperature of the device is maintained at the temperature at the time of steady operation, and the inherent laser characteristics are sufficiently maintained in the next burst operation. Can be withdrawn.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A high voltage pulse generator for a laser according to the present invention will be described below with reference to embodiments.

First, an example of an ArF excimer laser device to which the high voltage pulse generator for a laser according to the present invention is applied and an example of an excitation circuit thereof will be described.

FIG. 5 is a cross-sectional view perpendicular to the laser oscillation direction of the ArF excimer laser device. A laser cavity 1 is filled with a laser gas 2 (a mixed gas of Ar gas, F ₂ gas and Ne gas). Main discharge electrodes 3 and 4 for exciting the laser gas 2 are arranged facing each other in a direction perpendicular to the laser oscillation direction. The opposed main discharge electrodes 3, 4
The laser gas 2 is circulated by a fan (not shown) so as to form a gas flow 2 ′ therebetween. A corona preionization unit 10 is disposed upstream and downstream of the flow 2 ′ of the laser gas 2 in parallel along one main discharge electrode 4.
A corona discharge operation is performed immediately before a pulse voltage causing a main discharge is applied between the main discharge electrodes 4, and the laser beam 2 between the main discharge electrodes 3 and 4 is irradiated to weakly ionize the laser gas 2. Promote.

In this example, the corona preionization unit 10
A first electrode 11 is configured by inserting a cylindrical electrode into a tube 12 made of a dielectric material such as high-purity alumina ceramics and opened on one side; a second electrode 13 is configured by a rectangular plate-like electrode; The plate-like body of the second electrode 13 is bent in the vicinity of the one linear edge 13 ′, and the edge 1
At 3 ', the first electrode 11 is in line contact with the outer surface of the dielectric tube 12 in parallel. The second electrode 13 is formed by providing a plurality of openings in at least a portion other than the edge 13 ′ of the rectangular plate. The dielectric tube 12 around the first electrode 11 at the edge 13 ′ of the second electrode 13
Is set at a position where the laser excitation space between the main discharge electrodes 3 and 4 can be seen.

The main discharge voltage is applied between the main discharge electrodes 3 and 4 of such an ArF excimer laser device by an excitation circuit as shown in FIG. 6, and between the first electrodes 11 and 13 of the corona preionization section 10. Is applied with a preliminary discharge voltage.

The excitation circuit shown in FIG. 6 has three magnetic switches SL composed of a saturable reactor (saturable inductance).
It comprises a two-stage magnetic pulse compression circuit (MPC) using 0, SL1, and SL2. The magnetic switch SL0 is for protecting the solid state switch SW, and the first magnetic switch SL1
And the second magnetic switch SL2 constitute a two-stage magnetic pulse compression circuit (MPC).

The configuration and operation of the circuit will be described below with reference to FIG. First, the voltage of the high-voltage power supply HV is adjusted to a predetermined value, and the main capacitor C0 is charged via the magnetic switch SL0 and the inductance L1. At this time, the solid state switch SW is off. When the charging of the main capacitor C0 is completed and the solid state switch SW is turned on, the voltage applied to both ends of the solid state switch SW is shifted so as to be applied to both ends of the magnetic switch SL0, thereby protecting the solid state switch SW.
When the time integral of the charging voltage V0 of the main capacitor C0 applied to both ends of the magnetic switch SL0 reaches a limit value determined by the characteristics of the magnetic switch SL0, the magnetic switch SL0 is saturated and the magnetic switch is turned on, and the main capacitor C0 and the magnetic switch A current flows through the loop of SL0, the solid-state switch SW, and the capacitor C1, and the electric charge stored in the main capacitor C0 moves to charge the capacitor C1.

Thereafter, the voltage V1 across the capacitor C1
When the time integral of the magnetic switch SL1 reaches a limit value determined by the characteristics of the magnetic switch SL1, the magnetic switch SL1 is saturated and the magnetic switch is turned on, and a current flows through the loop of the capacitor C1, the capacitor C2, and the magnetic switch SL1, and is stored in the capacitor C1. The transferred electric charge is transferred to the capacitor C2.

Thereafter, when the time integral of the voltage V2 at the capacitor C2 reaches a limit value determined by the characteristics of the magnetic switch SL2, the magnetic switch SL2 is saturated and the magnetic switch is turned on, and the capacitor C2, the peaking capacitor Cp, and the magnetic switch SL2 are turned on. A current flows through the loop of the switch SL2,
The electric charge stored in the capacitor C2 shifts, and the peaking capacitor Cp is charged.

As apparent from the description of FIG. 5, the corona discharge for the preionization occurs on the outer peripheral surface of the dielectric tube 12 from the point where the dielectric tube 12 and the second electrode 13 are in contact. However, as the charging of the peaking capacitor Cp in FIG.
When 3 reaches a predetermined voltage, corona discharge occurs on the surface of the dielectric tube 12 in the corona preionization section. Ultraviolet rays 6 are generated on the surface of the dielectric tube 12 by the corona discharge, and the laser gas 2 as a laser medium between the main discharge electrodes 3 and 4 is preionized.

As the charging of the peaking capacitor Cp further proceeds, the voltage V3 of the peaking capacitor Cp increases, and this voltage V3 has a certain value (breakdown voltage).
When the voltage reaches Vb, the laser gas 2 between the main discharge electrodes 3 and 4 is broken down, and a main discharge is started. The main discharge excites a laser medium and generates a laser beam.

Thereafter, the voltage of the peaking capacitor Cp rapidly drops due to the main discharge, and eventually returns to the state before the start of charging.

Such a discharging operation is repeatedly performed by the switching operation of the solid state switch SW, so that pulse laser oscillation is performed at a predetermined repetition frequency.

Here, by setting the inductance of the capacitance transition type circuit of each stage composed of the magnetic switches SL1 and SL2 and the capacitors C1 and C2 so as to become smaller toward the subsequent stage, the current pulse flowing through each stage is reduced. A pulse compression operation is performed so that the pulse width gradually decreases,
A strong short-pulse discharge is realized between the main discharge electrodes 3 and 4.

Here, in the excitation circuit of FIG. 6, the magnetic pulse compression circuit (MPC) includes the magnetic switches SL1 and SL2 each composed of a saturable inductance having a non-linear characteristic, so that a large amount of heat is generated. It is necessary to perform cooling in order to suppress the generation.

Therefore, in the first embodiment of the present invention, as shown in FIG.
C) A configuration in which a portion 20 is immersed in a tank 21 filled with insulating oil 22 which is an insulating refrigerant. And this insulating oil 2
In order to cool 2, fins 25 for heat exchange connected to a cooling water injection side pipe 23 and a drainage side pipe 24 are arranged in the tank 21. Then, the temperature rise due to the heat generated from the magnetic pulse compression circuit 20 during the continuous operation is insulated through the fin 25 provided between the cooling water as the heat exchange medium flowing from the injection side pipe 23 to the drain side pipe 24. It is suppressed by cooling the oil 22. This configuration is the same as the conventional one.

In the present invention, a thermocouple 26 is disposed as a temperature detecting means at a position in contact with the insulating oil 22 in the tank 21 so that a temperature signal from the thermocouple 26 is inputted to the temperature controller 28 and the cooling water A heater 27 as heating means is provided in the middle of the injection side pipe 23, and the on / off operation of the heater 27 is controlled by a temperature controller 28 as temperature control means.

Since the embodiment shown in FIG. 1 has such a configuration, when the power of the excimer laser device having the excitation circuit as shown in FIG. Since the temperature is lower than the temperature at the time of operation, the temperature detected by the thermocouple 26 is a predetermined temperature (the temperature at the time of steady operation).
Lower than the range. Therefore, the temperature controller 28 determines that such is the case and turns on the heater 27. Heater 2
7 operates, the cooling water flowing from the injection side pipe 23 to the drain side pipe 24 via the fins 25 is warmed. As a result, the insulating oil 22 is also warmed, and the temperature of the magnetic pulse compression circuit 20 rises. FIG. 2 is a diagram showing the relationship between the temperature of the apparatus and the laser output at this time. The heater 27 is turned on almost at the same time when the power of the apparatus is turned on, and the temperature of the apparatus rapidly rises to near the operating temperature. Oscillation operation starts, and after the operation starts, it is possible to extract the maximum laser output.

In this configuration, in the burst operation in which the operation of stopping for a certain period of time after the operation for a certain period of time is repeated, the temperature of the insulating oil 22 tends to decrease because no heat is generated from the magnetic pulse compression circuit 20 during the stop period. However, when the temperature of the insulating oil 22 decreases, the heater 27 is turned on in the same manner as described above, so that the temperature of the device is kept within the temperature range of the steady operation, and the next burst operation starts from a high charging voltage. There is no necessity, and the inherent characteristics of the laser can be sufficiently brought out.

FIG. 3 is a diagram showing the configuration of a second embodiment of the present invention. In this embodiment, the magnetic pulse compression circuit (MPC) 20 shown in FIG. Immersed in the tank 21 filled with. In order to cool the insulating oil 22, heat exchange fins 25 connected to the cooling water injection side pipe 23 and the drainage side pipe 24 are arranged in the tank 21. And
The temperature rise due to heat generation from the magnetic pulse compression circuit 20 during continuous operation is controlled by flowing cooling water from the injection side pipe 23 to the drain side pipe 24 and cooling the insulating oil 22 through the fins 25 provided therebetween. Suppress. This configuration is the same as the conventional one.

In this embodiment, a proportional valve 31 is disposed in the middle of the cooling water injection pipe 23, and the flow rate thereof is controlled by the temperature controller 28. Also,
A fan 29 for forcibly circulating the insulating oil 22 in the tank 21 is provided, and the fan 29 is rotated by a motor 30. Further, a thermocouple 26 as a temperature detecting means is arranged at a position in contact with the insulating oil 22 in the tank 21 so that a temperature signal from the thermocouple 26 is inputted to the temperature controller 28.

With such a configuration, after the power of the excimer laser device having the excitation circuit as shown in FIG.
A certain amount of heat is given to the insulating oil 22 (the fan 29 is a heat source). When the power is turned on, the normal tank 2
Since the temperature of the insulating oil 22 in 1 is lower than the temperature in the steady operation, the temperature detected by the thermocouple 26 becomes lower than a predetermined temperature (temperature in the steady operation) range, and the proportional valve 31 is closed by the temperature regulator 28. . Then, the cooling water does not flow to the fins 25, the insulating oil 22 is warmed by the heating action of the fan 29, and the temperature of the magnetic pulse compression circuit 20 rises. Therefore, as in the case of FIG. 1, the temperature of the device rises to near the operating temperature, at which point the laser oscillation operation starts, and it is possible to extract the maximum laser output after the operation starts. When the temperature detected by the thermocouple 26 falls within the temperature range of the steady operation, the proportional valve 31 is opened by the temperature controller 28, cooling is performed as in the conventional case, and the steady operation is continued.

In this configuration, in the burst operation in which the operation of stopping for a certain time after the operation for a certain time is repeated,
During the idle period, the temperature of the insulating oil 22 tends to decrease because there is no heat generated from the magnetic pulse compression circuit 20. However, when the temperature of the insulating oil 22 decreases, the proportional valve 31 is closed as described above. Is maintained in the temperature range during steady operation,
In the next burst operation, it is not necessary to start from a high charging voltage, and the inherent characteristics of the laser can be sufficiently brought out.

In this embodiment, since the insulating oil 22 is forcibly circulated by the fan 29, heat exchange is performed by natural convection while the cooling water is flowing. More efficient heat exchange can be realized as compared with the embodiment. In this embodiment, the rotational speed of the motor 30 can be switched between two stages, and when the fan 29 is used as a heating device, the speed is increased, and when the heat exchange is promoted, the temperature controller 28 is decreased.
The control may be performed by using.

FIG. 4 is a diagram showing the configuration of the third embodiment of the present invention, which is a modification of the first embodiment. Also in this embodiment, a tank 21 in which the magnetic pulse compression circuit (MPC) 20 of FIG. 6 is filled with insulating oil 22 as an insulating refrigerant.
It is soaked inside. Then, in order to cool the insulating oil 22, the cooling water injection side pipe 23 and the drain side pipe 24
And a fin 25 for heat exchange connected to the tank 21. Then, the temperature rise due to the heat generated from the magnetic pulse compression circuit 20 during the continuous operation is controlled by flowing cooling water from the injection pipe 23 to the drain pipe 24 to cool the insulating oil 22 through the fins 25 provided therebetween. It suppresses by doing. This configuration is the same as the conventional one.

In this embodiment, a heater 27 is arranged on the upstream side of the cooling water injection pipe 23 and a proportional valve 31 is arranged on the downstream side.
A thermocouple 26 as a temperature detecting means is disposed at a position in contact with 2, and a temperature signal from the thermocouple 26 is input to a temperature regulator 28, which controls the opening of the proportional valve 31.

In this embodiment, after turning on the power of the excimer laser device having the excitation circuit as shown in FIG.
The heater 27 is always on. When the power is turned on, the temperature of the insulating oil 22 in the normal tank 21 is lower than the temperature during normal operation, so the temperature detected by the thermocouple 26 becomes lower than a predetermined temperature (temperature during normal operation) range, and the temperature controller 28 , The proportional valve 31 is throttled, and the amount of cooling water flowing from the injection side pipe 23 to the fins 25 is reduced. Therefore, the temperature of the cooling water is increased by heating the heater 27, the insulating oil 22 is warmed, and the magnetic pulse compression circuit The temperature of 20 rises. Therefore, as in the case of FIG. 1, the temperature of the device rapidly rises to near the operating temperature, at which point the laser oscillation operation starts, and after the operation starts, it is possible to extract the maximum laser output. Become. When the temperature detected by the thermocouple 26 falls within the temperature range during the steady operation, the proportional valve 31 is widely opened by the temperature controller 28, and the amount of cooling water flowing from the injection pipe 23 to the fins 25 increases. Is lowered, cooling is performed as before, and the steady operation is continued.

In this configuration, in a burst operation in which the operation of stopping for a certain time after the operation for a certain time is repeated,
The temperature of the insulating oil 22 tends to decrease because there is no heat generated from the magnetic pulse compression circuit 20 during the suspension period. However, when the temperature of the insulating oil 22 decreases, the proportional valve 31 is throttled in the same manner as described above. Is maintained in the temperature range during the steady operation, and it is not necessary to start from a high charging voltage in the next burst operation, and the inherent characteristics of the laser can be sufficiently brought out.

Although the high voltage pulse generator for laser according to the present invention has been described based on several embodiments, the present invention is not limited to these embodiments, and various modifications are possible.

[0046]

As is apparent from the above description, according to the high voltage pulse generator for laser of the present invention, the temperature detecting means for detecting the temperature of the refrigerant, the heat exchange medium for exchanging heat with the refrigerant, Heating means for heating directly or via a heat exchange medium, and controlling the operation of the heating means or the flow rate of the heat exchange medium based on the detection result of the temperature detection means to control the temperature of the refrigerant within a predetermined temperature range. Temperature control means, so that the temperature of the device rapidly rises to near the operating temperature substantially at the same time when the power of the device is turned on, at which point the laser oscillation operation starts, and after the operation starts, the maximum laser The output can be extracted. In addition, even during a pause period between burst operations in which the operation is paused for a predetermined time after the operation for a predetermined time, the temperature of the device is maintained at the temperature at the time of steady operation, and the inherent laser characteristics are sufficiently maintained in the next burst operation. Can be withdrawn.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a main part of a high voltage pulse generator for a laser according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the relationship between temperature and laser output for explaining the operation of the apparatus in FIG. 1;

FIG. 3 is a diagram showing a configuration of a main part of a high-voltage pulse generator for laser according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a main part of a high voltage pulse generator for laser according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view perpendicular to the laser oscillation direction of an example of an ArF excimer laser device.

6 is a circuit diagram of an example of an excitation circuit of the ArF excimer laser device of FIG.

FIG. 7 is a diagram illustrating the relationship between the temperature and the laser output of the ArF excimer laser device.

8 is a diagram showing a change in temperature and a change in laser output in the case of a constant charging voltage operation of the ArF excimer laser device of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser cavity 2 ... Laser gas 2 '... Laser gas flow 3, 4 ... Main discharge electrode 6 ... Ultraviolet light 10 ... Corona preliminary ionization part 11 ... Corona preliminary ionization part 1st electrode 12 ... Dielectric tube 13 ... Corona preliminary ionization part 2nd Electrode 13 '... Edge 20 ... Magnetic pulse compression circuit (MPC) 21 ... Tank 22 ... Insulating oil 23 ... Cooling water injection pipe 24 ... Drainage pipe 25 ... Fin 26 ... Thermocouple 27 ... Heater 28 ... Temperature controller 29 ... Fan 30 Motor 31 Proportional valve SL0 Solid state switch protection magnetic switch SL1 First magnetic switch SL2 Second magnetic switch HV High voltage power supply L1 Inductance SW Solid state switch C0 Main capacitor C1 First C2: second capacitor Cp: peaking capacitor

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hidenori Watanabe 1-90 Komamon, Gotemba-shi, Shizuoka Fushio Research Institute, Inc. F-term (reference) 5F071 AA06 CC01 CC03 CC05 EE04 GG03 GG04 GG05 GG08 HH02 HH07 JJ05 JJ08 5F072 AA06 GG03 GG04 GG05 GG08 HH02 HH07 JJ05 JJ08 SS06 TT01 TT25 TT28

Claims (3)

[Claims] 1. A high voltage pulse generator for laser comprising at least a saturable inductance and a capacitor constituting a magnetic pulse compression circuit, which is immersed in an insulating refrigerant, wherein: a temperature detecting means for detecting a temperature of the refrigerant; A heat exchange medium for exchanging heat; a heating unit for heating the refrigerant directly or via the heat exchange medium; and controlling an operation of the heating unit or a flow rate of the heat exchange medium based on a detection result of the temperature detection unit. And a temperature controller for controlling the temperature of the refrigerant to a predetermined temperature range. 2. The temperature control unit is configured to control and prepare the temperature of the refrigerant within a predetermined temperature range by the heating unit before starting the laser oscillation operation or during a suspension period. 2. The method according to claim 1, wherein
The high voltage pulse generator for a laser according to the above. 3. The heating device according to claim 1, wherein said heating means comprises a fan for forcibly circulating said refrigerant.
The high voltage pulse generator for a laser according to the above.