阅读说明：本技术 电容器的冷却构造和激光装置 (Cooling structure of capacitor and laser device ) 是由 胜海久和 藤本准一 田中智史 于 2017-08-07 设计创作，主要内容包括：为了对具有第1电极和第2电极的电容器进行冷却,电容器的冷却构造包含：导电部,其与第1电极电连接；绝缘部,其具有包含第1位置的第1面和包含第2位置的第2面,在第1位置处与导电部连接；第1紧固部,其对导电部和绝缘部进行紧固；以及冷却部,其与和第1位置对置的第2位置连接,导电部和冷却部通过绝缘部而电绝缘。(In order to cool a capacitor having a 1 st electrode and a 2 nd electrode, a cooling structure of the capacitor includes: a conductive portion electrically connected to the 1 st electrode; an insulating section having a 1 st surface including a 1 st position and a 2 nd surface including a 2 nd position, the insulating section being connected to the conductive section at the 1 st position; a first fastening section for fastening the conductive section and the insulating section; and a cooling section connected to a 2 nd position opposite to the 1 st position, the conductive section and the cooling section being electrically insulated by an insulating section.)

1. A cooling configuration for a capacitor having a 1 st electrode and a 2 nd electrode, wherein the cooling configuration for the capacitor comprises:

a conductive portion electrically connected to the 1 st electrode;

an insulating section having a 1 st surface including a 1 st position and a 2 nd surface including a 2 nd position, the insulating section being connected to the conductive section at the 1 st position;

a first fastening portion 1 that fastens the conductive portion and the insulating portion; and

a cooling unit connected to the 2 nd position opposite to the 1 st position,

the conductive portion and the cooling portion are electrically insulated by the insulating portion.

2. The cooling structure of a capacitor as claimed in claim 1,

the conductive portion and the insulating portion are in contact via a metal sheet.

3. The cooling structure of a capacitor as claimed in claim 1,

the conductive portion and the insulating portion are in contact via a resin sheet.

4. The cooling structure of a capacitor as claimed in claim 1,

the insulating portion is configured to cover one end of the conductive portion.

5. The cooling structure of a capacitor as claimed in claim 1,

the insulating portion is configured to cover one end of the cooling portion.

6. The cooling structure of a capacitor as claimed in claim 1,

the insulating portion comprises aluminum oxide and is formed by coating aluminum oxide,

the 1 st fastening portion comprises an alloy comprising nickel and cobalt.

7. The cooling structure of a capacitor as claimed in claim 1,

a portion of the 1 st fastening part is welded to the insulating part.

8. The cooling structure of a capacitor as claimed in claim 1,

the conductive portion has a 1 st bolt hole formed with an internal thread,

the 1 st fastening part has a 1 st portion welded to the insulating part, and a 2 nd portion formed with an external thread screwed into the 1 st bolt hole.

9. The cooling structure of a capacitor as claimed in claim 8,

the 1 st bolt hole has a 1 st large diameter portion that receives the 1 st portion and a 1 st small diameter portion that receives the 2 nd portion.

10. The cooling structure of a capacitor as claimed in claim 1,

the cooling structure of the capacitor further includes a 2 nd fastening portion that fastens the cooling portion and the insulating portion.

11. The cooling structure of a capacitor as claimed in claim 10,

the insulating portion comprises aluminum oxide and is formed by coating aluminum oxide,

the 2 nd fastening portion comprises an alloy comprising nickel and cobalt.

12. The cooling structure of a capacitor as claimed in claim 10,

a portion of the 2 nd fastening part is welded to the insulating part.

13. The cooling structure of a capacitor as claimed in claim 10,

the cooling portion has a 2 nd bolt hole formed with an internal thread,

the 2 nd fastening part has a 3 rd portion welded to the insulating part and a 4 th portion formed with an external thread screwed into the 2 nd bolt hole.

14. The cooling structure of a capacitor as claimed in claim 13,

the 2 nd bolt hole has a 2 nd large diameter portion that accommodates the 3 rd portion and a 2 nd small diameter portion that accommodates the 4 th portion.

15. The cooling structure of a capacitor as claimed in claim 1,

the 1 st electrode is electrically connected to an output terminal of a power supply device, the 2 nd electrode is electrically connected to a 3 rd electrode, and the 3 rd electrode has a potential between a potential of the output terminal and a reference potential.

16. The cooling structure of a capacitor as claimed in claim 15,

the cooling portion is electrically connected to the reference potential.

17. The cooling structure of a capacitor as claimed in claim 1,

the conductive portion has a through-hole,

the 1 st tightening part has a 5 th part welded to the insulating part and positioned on one side in the penetrating direction of the through hole, a 6 th part positioned on the other side in the penetrating direction of the through hole, and a 7 th part attached to the 6 th part and fixing the conductive part to the insulating part.

18. The cooling structure of a capacitor as claimed in claim 1,

the 2 nd electrode is electrically connected to an output terminal of a power supply device, the 1 st electrode is electrically connected to a 3 rd electrode, and the 3 rd electrode has a potential between a potential of the output terminal and a reference potential.

19. The cooling structure of a capacitor as claimed in claim 18,

the cooling portion is electrically connected to the reference potential.

20. A laser device, comprising:

a laser cavity;

a pair of discharge electrodes disposed in the laser cavity;

a pulse power module having a peaking capacitor and configured to apply a pulse voltage between the pair of discharge electrodes;

a pre-ionization mechanism including a pre-ionization capacitor having a 1 st electrode and a 2 nd electrode, and configured to ionize a part of gas inside the laser cavity;

a conductive portion electrically connected to the 1 st electrode;

an insulating section having a 1 st surface including a 1 st position and a 2 nd surface including a 2 nd position, the insulating section being connected to the conductive section at the 1 st position;

a first fastening portion 1 that fastens the conductive portion and the insulating portion; and

a cooling unit connected to the 2 nd position opposite to the 1 st position,

the conductive portion and the cooling portion are electrically insulated by the insulating portion.

Technical Field

The present disclosure relates to a cooling structure of a capacitor and a laser device.

Background

In recent years, in a semiconductor exposure apparatus (hereinafter referred to as "exposure apparatus"), with the miniaturization and high integration of a semiconductor integrated circuit, improvement in resolution has been demanded. Therefore, the wavelength of light emitted from the exposure light source has been reduced. In general, a gas laser device is used as an exposure light source instead of a conventional mercury lamp. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs an ultraviolet laser beam having a wavelength of 248nm and an ArF excimer laser device that outputs an ultraviolet laser beam having a wavelength of 193nm are used.

Disclosure of Invention

A cooling structure of a capacitor according to an aspect of the present disclosure cools a capacitor having a 1 st electrode and a 2 nd electrode, wherein the cooling structure of the capacitor includes: a conductive portion electrically connected to the 1 st electrode; an insulating section having a 1 st surface including a 1 st position and a 2 nd surface including a 2 nd position, the insulating section being connected to the conductive section at the 1 st position; a first fastening section for fastening the conductive section and the insulating section; and a cooling section connected to a 2 nd position opposite to the 1 st position, the conductive section and the cooling section being electrically insulated by an insulating section.

A laser device according to another aspect of the present disclosure includes: a laser cavity; a pair of discharge electrodes disposed in the laser cavity; a pulse power module having a peaking capacitor and configured to apply a pulse voltage between a pair of discharge electrodes; a pre-ionization mechanism which is provided with a pre-ionization capacitor having a 1 st electrode and a 2 nd electrode and is configured to ionize a part of gas in the laser cavity; a conductive portion electrically connected to the 1 st electrode; an insulating section having a 1 st surface including a 1 st position and a 2 nd surface including a 2 nd position, the insulating section being connected to the conductive section at the 1 st position; a first fastening section for fastening the conductive section and the insulating section; and a cooling section connected to a 2 nd position opposite to the 1 st position, the conductive section and the cooling section being electrically insulated by an insulating section.

Drawings

Several embodiments of the present disclosure will be described below as simple examples with reference to the drawings.

Fig. 1 schematically shows the structure of a laser device of a comparative example.

Fig. 2 schematically shows the structure of a laser device of a comparative example.

Fig. 3 is a circuit diagram of a pulse power module and a pre-ionization mechanism.

Fig. 4A is a plan view showing the arrangement of the peaking capacitor and the pre-ionization capacitor in the laser device of embodiment 1.

Fig. 4B is a cross-sectional view taken along line IVB-IVB of fig. 4A.

Fig. 5A is a plan view showing the arrangement of the peaking capacitor and the pre-ionization capacitor in the laser device of embodiment 2.

Fig. 5B is a sectional view taken along line VB-VB of fig. 5A.

Fig. 5C is a cross-sectional view at line VC-VC of fig. 5A.

Fig. 6A is a plan view showing the arrangement of the peaking capacitor and the pre-ionization capacitor in the laser device of the reference example.

Fig. 6B is a cross-sectional view at line VIB-VIB of fig. 6A.

Detailed Description

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1. Comparative example

1.1 Structure of laser device

1.2 operation of the laser device

1.3 details of the pulse Power Module and Pre-ionization mechanism

1.3.1 Structure

1.3.2 actions

1.4 problems

2. Cooling structure for fastening conductive part and insulating part

2.1 Structure

2.2 actions and effects

3. Cooling structure provided in preionization wiring section

3.1 Structure

3.2 actions and effects

4. Others

4.1 Structure of reference example

4.2 actions and effects of reference example

4.3 supplement

Embodiments of the present disclosure will be described in detail below with reference to the drawings. The embodiments described below are merely examples of the present disclosure, and do not limit the present disclosure. Note that the structures and operations described in the embodiments are not necessarily all necessary for the structures and operations of the present disclosure. The same components are denoted by the same reference numerals, and redundant description thereof is omitted.

1. Comparative example

1.1 Structure of laser device

Fig. 1 and 2 schematically show the structure of a laser device of a comparative example. Fig. 1 shows an internal structure of the laser device as viewed from a direction substantially perpendicular to a discharge direction between the pair of discharge electrodes 11a and 11b and substantially perpendicular to a traveling direction of the laser light output from the output coupling mirror 15. Fig. 2 shows an internal configuration of the laser device as viewed from a direction substantially parallel to a traveling direction of the laser light output from the output coupling mirror 15. The traveling direction of the laser light output from the output coupling mirror 15 is assumed to be the Z direction. Let the discharge direction between the pair of discharge electrodes 11a and 11b be the V direction. The direction perpendicular to both of these is defined as the H direction. the-V direction substantially coincides with the direction of gravity.

As shown in fig. 1, a laser apparatus is used with an exposure apparatus 100. The laser light output from the laser device is incident on the exposure device 100. The exposure apparatus 100 includes an exposure apparatus control unit 110. The exposure device control unit 110 is configured to control the exposure device 100. The exposure apparatus control unit 110 is configured to transmit setting data of a target pulse energy or a light emission trigger signal to the laser control unit 30 included in the laser apparatus.

The laser device includes a laser cavity 10, a charger 12, a pulse power module 13, a narrowband module 14, an output coupling mirror 15, an energy monitor 17, a cross flow fan 21, a motor 22, and a laser control unit 30. The laser control unit 30 performs overall control of the entire laser device.

The laser cavity 10 is disposed on the optical path of a laser resonator including a narrowing-band module 14 and an output coupling mirror 15. In the laser cavity 10, 2 windows 10a and 10b are provided. The laser cavity 10 accommodates a pair of discharge electrodes 11a and 11 b. The laser cavity 10 accommodates a laser gas as a laser medium.

The laser cavity 10 has an opening which is blocked by an electrically insulating part 20. The electrical insulating portion 20 supports the discharge electrode 11 a. A plurality of conductive portions 20a are embedded in the electrical insulating portion 20. The conductive portions 20a are electrically connected to the discharge electrodes 11a, respectively.

A return plate 10c is disposed inside the laser cavity 10. The laser cavity 10 and the return board 10c are electrically connected by a wiring portion 10d and a wiring portion 10e shown in fig. 2. The reflow plate 10c supports the discharge electrode 11 b. The return plate 10c is electrically connected to the discharge electrode 11 b.

The return plate 10c does not completely separate the inside of the laser cavity 10. As shown in fig. 2, the reflow plate 10c has gaps for passing the laser gas on the back side and the front side of the sheet of fig. 1.

The cross flow fan 21 is disposed inside the laser cavity 10. A motor 22 is connected to a rotary shaft of the cross flow fan 21, and the motor 22 is disposed outside the laser cavity 10. The cross flow fan 21 is rotated by the motor 22. Thereby, the laser gas circulates inside the laser cavity 10 as indicated by the arrow a in fig. 2. The heat exchanger 23 is configured to discharge thermal energy of the laser gas having a high temperature due to the discharge to the outside of the laser cavity 10.

The charger 12 holds electric power for supplying to the pulse power module 13.

The pulse power module 13 includes a plurality of peaking capacitors C3. The pulse power module 13 corresponds to a power supply device in the present disclosure. The peaking capacitors C3 each include 2 electrodes. One of the 2 electrodes is electrically connected to the connection plate 20b, and the other electrode is electrically connected to the connection plate 10f or 10g shown in fig. 2. The connection plate 20b is electrically connected to the discharge electrode 11a via the conductive portion 20 a. The connection plates 10f and 10g are electrically connected to the discharge electrode 11b via the laser cavity 10, the wiring portions 10d and 10e, and the return plate 10 c. The laser cavity 10 is electrically connected to a reference potential. The reference potential is a potential that is a reference of the pulse-like high voltage generated by the pulse power module 13, and is, for example, a ground potential.

The cooling mechanism 27f is in contact with the connecting plate 10f and fixed thereto, and the cooling mechanism 27g is in contact with the connecting plate 10g and fixed thereto. The cooling mechanisms 27f and 27g include, for example, cooling pipes, not shown, through which a cooling medium such as water passes. The cooling mechanisms 27f and 27g are each made of a metal having a high thermal conductivity. The cooling mechanisms 27f and 27g are at the same potential as the connecting plates 10f and 10 g.

The laser apparatus also includes a pre-ionization mechanism. The pre-ionization mechanism includes pre-ionization capacitor C11 shown in fig. 1, pre-ionization wiring portion 35, dielectric tube 24, pre-ionization inner electrode 25 shown in fig. 2, and plurality of pre-ionization outer electrodes 26. The pre-ionization capacitors C11 each include 2 electrodes. One of the 2 electrodes is electrically connected to the connection plate 20b, and the other electrode is electrically connected to the preionization internal electrode 25 via the preionization wiring portion 35. The pre-ionization inner electrode 25 corresponds to the 3 rd electrode in the present disclosure. The preionization wiring portion 35 is covered with an insulator not shown. The pre-ionization inner electrode 25 is covered by a dielectric tube 24.

The pre-ionization outer electrodes 26 are electrically connected to the discharge electrode 11b at respective one ends thereof and are in contact with the surface of the dielectric tube 24 at the other ends thereof. The preionization internal electrode 25 and the plurality of preionization external electrodes 26 are arranged on the upstream side in the circulation direction of the laser gas from the position of the discharge electrode 11b along the longitudinal direction of the discharge electrode 11 b.

The narrowing module 14 includes wavelength selective elements such as a prism 14a and a grating 14 b. Instead of the narrow-banded module 14, a high-reflection mirror may be used.

The output coupling mirror 15 is constituted by a partially reflecting mirror.

The energy monitor 17 includes a beam splitter 17a, a condenser lens 17b, and a light sensor 17 c. The beam splitter 17a is disposed on the optical path of the laser light output from the output coupling mirror 15. The beam splitter 17a is configured to transmit a part of the laser light output from the output coupling mirror 15 toward the exposure apparatus 100 with high transmittance and to reflect the other part. The condenser lens 17b and the optical sensor 17c are disposed on the optical path of the laser light reflected by the beam splitter 17 a.

1.2 operation of the laser device

The laser control section 30 receives setting data of a target pulse energy and a light emission trigger signal from the exposure device control section 110. The laser control unit 30 transmits the setting data of the charging voltage to the charger 12 based on the setting data of the target pulse energy received from the exposure device control unit 110. The laser control unit 30 also transmits a trigger signal to the pulse power module 13 in response to the light emission trigger signal received from the exposure device control unit 110.

The pulse power module 13 receives the trigger signal from the laser control unit 30, generates a pulse-like high voltage from the electric energy charged by the charger 12, and applies the high voltage between the pair of discharge electrodes 11a and 11 b.

When a high voltage is applied between the pair of discharge electrodes 11a and 11b, a discharge is caused between the pair of discharge electrodes 11a and 11 b. This discharge is referred to as a main discharge. The laser gas in the laser cavity 10 is excited to transition to a high energy level by the energy of the main discharge. When the excited laser gas then transitions to a low level, light of a wavelength corresponding to the level difference is emitted.

Light generated in the laser cavity 10 is emitted to the outside of the laser cavity 10 via the windows 10a and 10 b. The light emitted from the window 10a of the laser cavity 10 is expanded in beam width by the prism 14a and enters the grating 14 b. The light incident on the grating 14b from the prism 14a is reflected by the plurality of grooves of the grating 14b, and is diffracted in a direction corresponding to the wavelength of the light. The grating 14b is configured by littrow so that the incident angle of light incident on the grating 14b from the prism 14a coincides with the diffraction angle of diffracted light of a desired wavelength. Thereby, light near the desired wavelength is returned to the laser cavity 10 via the prism 14 a.

The output coupling mirror 15 transmits a part of the light emitted from the window 10b of the laser cavity 10 to output the light, and reflects the other part of the light to return to the laser cavity 10.

In this way, the light exiting the laser cavity 10 reciprocates between the narrowband module 14 and the output coupling mirror 15. This light is amplified each time it passes through the discharge space between the pair of discharge electrodes 11a and 11 b. Each time the narrowing module 14 is turned back, the light is narrowed. The light thus oscillated and narrowed is output as laser light from the output coupling mirror 15.

The condenser lens 17b included in the energy monitor 17 condenses the laser light reflected by the beam splitter 17a on the optical sensor 17 c. The optical sensor 17c transmits an electric signal corresponding to the pulse energy of the laser beam condensed by the condenser lens 17b to the laser control unit 30 as measurement data.

The laser controller 30 receives measurement data from the energy monitor 17. The laser control unit 30 feedback-controls the charging voltage set by the charger 12 based on the measurement data of the pulse energy received from the energy monitor 17 and the setting data of the target pulse energy received from the exposure device control unit 110.

1.3 details of the pulse Power Module and Pre-ionization mechanism

1.3.1 Structure

Fig. 3 is a circuit diagram of a pulse power module and a pre-ionization mechanism. The pulse power module 13 includes a charging capacitor C0, a switch 13a, a step-up transformer TC1, a plurality of magnetic switches Sr1 to Sr3, capacitors C1 and C2, and a peaking capacitor C3.

The magnetic switches Sr1 to Sr3 each include a saturable reactor. Each of the magnetic switches Sr1 to Sr3 is configured to have a low impedance when the time integral value of the voltage applied across the switch reaches a predetermined value determined by the characteristics of the respective magnetic switches.

A pre-ionization capacitor C11 and an inductor L0 are electrically connected between the above-indicated one electrode of the peaking capacitor C3 electrically connected to the discharge electrode 11a and the pre-ionization inner electrode 25. The preionization wiring portion 35 is configured as an inductor L0.

A capacitor C12 is electrically connected between the pre-ionization inner electrode 25 and the plurality of pre-ionization outer electrodes 26 electrically connected to the discharge electrode 11 b. The dielectric tube 24 is configured as a capacitor C12.

The pre-ionization capacitor C11 and the capacitor C12 are configured to divide the pulse-like high voltage supplied from the pulse power module 13. For example, the capacitance ratio of the pre-ionization capacitor C11 to the capacitor C12 is set so that the voltage applied to the capacitor C12 is in the range of 25% to 75% of the voltage supplied from the pulse power module 13.

The timing of the application of voltage between pre-ionization outer electrode 26 and pre-ionization inner electrode 25 is adjusted by selecting the capacitance of pre-ionization capacitor C11, the capacitance of capacitor C12, and the inductance of inductor L0. The combined capacitance of the pre-ionization capacitor C11 and the capacitor C12 may be 10% or less of the capacitance of the peaking capacitor C3.

1.3.2 actions

The charger 12 charges the charging capacitor C0 in accordance with the charging voltage set by the laser control unit 30.

The laser control unit 30 inputs a trigger signal to the switch 13a of the pulse power module 13. When the trigger signal is input to the switch 13a, the switch 13a is turned on. When the switch 13a is turned on, a current flows from the charging capacitor C0 to the 1 st side of the step-up transformer TC 1.

When a current flows through the 1 st side of the step-up transformer TC1, a current flows in the opposite direction to the 2 nd side of the step-up transformer TC1 due to electromagnetic induction. After the current flows on the 2 nd side of the step-up transformer TC1, the time-integrated value of the voltage applied to the magnetic switch Sr1 reaches the threshold value.

When the time integral value of the voltage applied to the magnetic switch Sr1 reaches the threshold value, the magnetic switch Sr1 is in a magnetically saturated state, and the magnetic switch Sr1 is closed.

When the magnetic switch Sr1 is closed, a current flows from the secondary side 2 of the step-up transformer TC1 to the capacitor C1, and the capacitor C1 is charged.

Since the capacitor C1 is charged, the magnetic switch Sr2 is in a magnetically saturated state and the magnetic switch Sr2 is closed.

When the magnetic switch Sr2 is closed, a current flows from the capacitor C1 to the capacitor C2, and the capacitor C2 is charged. At this time, the capacitor C2 is charged with a pulse width shorter than the pulse width of the current when the capacitor C1 is charged.

Since the capacitor C2 is charged, the magnetic switch Sr3 is in a magnetically saturated state and the magnetic switch Sr3 is closed.

When the magnetic switch Sr3 is closed, a current flows from the capacitor C2 to the peaking capacitor C3, and the peaking capacitor C3 is charged. At this time, the peaking capacitor C3 is charged with a pulse width shorter than that of the current when the capacitor C2 is charged.

As described above, the current flows from the capacitor C1 to the capacitor C2 and from the capacitor C2 to the peaking capacitor C3 in this order, and the pulse width of the current is compressed to a high voltage.

When the voltage of the peaking capacitor C3 reaches the breakdown voltage of the laser gas, a main discharge is generated between the pair of discharge electrodes 11a and 11 b. Thereby, the laser gas is excited and laser oscillation is performed. The main discharge is repeated by the switching operation of the switch 13a, and thereby, the pulse laser is output at a predetermined repetition frequency.

At the periphery of the dielectric tube 24, an electric field is generated by applying a voltage between the pre-ionization outer electrode 26 and the pre-ionization inner electrode 25. The electric field creates a corona discharge at the periphery of the dielectric tube 24. Light of short wavelength is generated by corona discharge. The short-wavelength light ionizes a part of the laser gas between the pair of discharge electrodes 11a and 11b to generate charged particles. Ionizing a portion of the lasing gas prior to the main discharge is referred to as pre-ionization. The capacitance of the pre-ionization capacitor C11, the capacitance of the capacitor C12, and the inductance of the inductor L0 are selected so that the main discharge is generated at a prescribed timing after pre-ionization. This can generate a main discharge with little displacement in the longitudinal direction of the pair of discharge electrodes 11a and 11b, and can perform stable laser output.

1.4 problems

An electrical loss is generated in the peaking capacitor C3, and the electrical loss becomes heat. When the temperature of the peaking capacitor C3 changes due to the heat, the capacitance of the peaking capacitor C3 changes, the timing of main discharge shifts, or the stability of laser output decreases in some cases. Therefore, the peaking capacitor C3 is cooled by the cooling mechanism 27f connected via the connection board 10f or the cooling mechanism 27g connected via the connection board 10 g.

Heat is also generated in the pre-ionization capacitor C11, the capacitance of the pre-ionization capacitor C11 changes, the timing of pre-ionization shifts, or the stability of laser output decreases in some cases. However, the pre-ionization capacitor C11 has a potential different from the potentials of the cooling mechanisms 27f and 27g, and it may be difficult to cool by the cooling mechanisms 27f and 27 g. In order to cool pre-ionization capacitor C11, it is conceivable that an air flow is generated by a cooling fan, not shown, but the cooling effect may be insufficient in cooling by the air flow.

Fig. 4 of jp 2009-: a conductive member for preionization electrically connected to a preionization capacitor is brought into contact with a ceramic member having a high thermal conductivity, and the ceramic member is brought into contact with a water jacket as a cooling member. However, in this configuration, the contact force between the conductive member for preionization and the ceramic member may vary for each product. When the contact force between the conductive member for preionization and the ceramic member is weak, heat conduction from the conductive member for preionization to the ceramic member is insufficient, and the preionization capacitor may not be sufficiently cooled.

In the embodiment described below, the conductive portion electrically connected to the preionization capacitor and the insulating portion connected to the cooling portion are fastened by the 1 st fastening portion, thereby cooling the preionization capacitor.

2. Cooling structure for fastening conductive part and insulating part

2.1 Structure

Fig. 4A is a plan view showing the arrangement of the peaking capacitor and the pre-ionization capacitor in the laser device of embodiment 1. Fig. 4B is a cross-sectional view taken along line IVB-IVB of fig. 4A.

The connection plate 20b is disposed on the electrical insulating portion 20 shown in fig. 1 and 2. The connection plate 20b is disposed such that the longitudinal direction of the pair of discharge electrodes 11a and 11b and the longitudinal direction of the connection plate 20b are substantially parallel. The connection plate 20b is electrically connected to an output terminal of a pulse-like high voltage outputted from the pulse power module 13. A plurality of peaking capacitors C3 are arranged in parallel on the H direction side and the-H direction side of the connection board 20b, respectively.

The connection plates 10f and 10g are arranged substantially parallel to the connection plate 20b with the connection plate 20b therebetween. The connection plates 10f and 10g are electrically connected to a reference potential. The cooling mechanism 27f is in contact with the connecting plate 10f and fixed thereto, and the cooling mechanism 27g is in contact with the connecting plate 10g and fixed thereto.

As shown in fig. 4B, the pre-ionization capacitor C11 includes a capacitor main body 31a, a 1 st electrode 31B, a 2 nd electrode 31C, and a covering 31d, respectively. The capacitor body 31a is sandwiched between the 1 st electrode 31b and the 2 nd electrode 31c, and the capacitance between the 1 st electrode 31b and the 2 nd electrode 31c is set to a predetermined capacitance. The covering portion 31d covers the capacitor main body 31a, a part of the 1 st electrode 31b, and a part of the 2 nd electrode 31 c.

The 2 nd electrode 31c is electrically connected to the pre-ionization wiring portion 35 a. In order to fix the preionization wiring portion 35a to the 2 nd electrode 31c, a bolt 35d penetrating the preionization wiring portion 35a is screwed into a bolt hole 31f formed in the 2 nd electrode 31 c.

Pre-ionization wiring 35a is introduced into the interior of laser cavity 10 via feed-through 36. The pre-ionization wiring portion 35a is electrically connected to the pre-ionization internal electrode 25 inside the laser cavity 10. Thereby, the 2 nd electrode 31c is electrically connected to the pre-ionization inner electrode 25. The potential of the preionization internal electrode 25 is a potential between the potential of the pulse-like high voltage outputted from the pulse power module 13 and the reference potential.

The 1 st electrode 31b is connected to a cooling structure including a conductive portion 32, an insulating portion 33, and a cooling portion 34.

The conductive portion 32 includes a 1 st bolt hole having a 1 st large diameter portion 32a and a 1 st small diameter portion 32b formed with an internal thread, and an externally threaded portion 32 c. The 1 st bolt hole and the male screw portion 32c are located on the surfaces of the conductive portion 32 opposite to each other. The male screw portion 32c is screwed into the bolt hole 31e of the 1 st electrode 31b, whereby the conductive portion 32 and the 1 st electrode 31b are electrically connected. The conductive portion 32 is made of a material having high conductivity, such as copper.

One end of the conductive member 28a is in contact with and fixed to the conductive portion 32. The other end of the conductive member 28a is in contact with the connecting plate 20b and fixed thereto. Thus, the 1 st electrode 31b of the preionization capacitor C11 is electrically connected to the output terminal of the pulse-like high voltage output from the pulse power module 13 via the conductive portion 32, the conductive member 28a, and the connection plate 20 b.

The insulating portion 33 has a 1 st surface including a 1 st position 33a and a 2 nd surface including a 2 nd position 33 b. The 1 st surface and the 2 nd surface are surfaces opposite to each other. The 1 st position 33a and the 2 nd position 33b are positions opposed to each other. The insulating portion 33 further includes a 1 st projecting portion 33c projecting from the approximate center of the 1 st position 33a in the approximate normal direction of the 1 st surface, and a 2 nd projecting portion 33d projecting from the approximate center of the 2 nd position 33b in the approximate normal direction of the 2 nd surface. The insulating portion 33 further includes a 1 st cover 33e protruding in a direction substantially normal to the 1 st surface around the 1 st position 33a, and a 2 nd cover 33f protruding in a direction substantially normal to the 2 nd surface around the 2 nd position 33 b.

The insulating portion 33 is preferably made of a material having a low dielectric constant. The dielectric constant of the insulating portion 33 is preferably 10 or less. For example, the insulating portion 33 is made of alumina having a dielectric constant of 8.4 or more and 9.9 or less or aluminum nitride having a dielectric constant of 8.5 or more and 8.6 or less.

The 1 st projection 33c of the insulating portion 33 is fixed with the 1 st tightening portion 37. The 1 st fastening portion 37 has a 1 st part 37a fixed to the 1 st protrusion 33c, and a 2 nd part 37b formed with a male screw screwed into the 1 st small diameter portion 32b of the 1 st bolt hole. The 1 st portion 37a is wrapped around the 1 st projection 33c and welded to the 1 st projection 33c, thereby being firmly fixed to the 1 st projection 33 c. Further, the 2 nd portion 37b is screwed into the 1 st small diameter portion 32b, whereby the conductive portion 32 and the insulating portion 33 are fastened.

At this time, the conductive portion 32 is closely attached to and fixed to the 1 st position 33a of the insulating portion 33. The 1 st cover 33e surrounds the periphery of the conductive portion 32 so as to cover one end of the conductive portion 32. The 1 st portion 37a is accommodated in the 1 st large diameter portion 32a, and the 2 nd portion 37b is accommodated in the 1 st small diameter portion 32 b.

In the case where the insulating portion 33 is a ceramic containing alumina, the 1 st fastening portion 37 preferably includes an alloy containing nickel and cobalt. Accordingly, the insulating portion 33 and the 1 st fastening portion 37 are formed of materials having similar thermal expansion coefficients, and the effect of temperature change on the fixation of the insulating portion 33 and the 1 st fastening portion 37 by welding can be suppressed.

In order to sufficiently adhere the conductive portion 32 and the insulating portion 33, the surface roughness Ra of the contact surface between the conductive portion 32 and the insulating portion 33 is preferably 6.3 μm or less. For example, it is preferably 3.2 μm. Further, the area of the contact surface between the conductive portion 32 and the insulating portion 33 is preferably 110mm²The above. For example, it is preferably set to 150mm²。

The 1 st position 33a of the conductive portion 32 and the insulating portion 33 may be contacted via a metal sheet. The metal sheet may be, for example, a sheet of aluminum, copper or tin. The thickness of the metal sheet may be 10 μm or more and 30 μm or less. More preferably 10 μm or more and 20 μm or less.

Alternatively, the 1 st position 33a of the conductive portion 32 and the insulating portion 33 may be contacted via a resin sheet. The resin sheet may be a sheet of silicone rubber or acrylic rubber, for example. The thickness of the resin sheet may be 10 μm or more and 1000 μm or less. For example, it may be 500 μm.

By using the metal sheet or the resin sheet, the air layer between the conductive portion 32 and the insulating portion 33 is reduced, and heat conduction from the conductive portion 32 to the insulating portion 33 is efficiently performed.

The cooling portion 34 includes a 2 nd bolt hole having a 2 nd large diameter portion 34a and a 2 nd small diameter portion 34b formed with an internal thread. The cooling portion 34 is made of a material having high electrical conductivity, such as copper.

The cooling portion 34 is connected to the cooling mechanism 27g at a portion different from the 2 nd bolt hole. This enables heat conduction from the cooling unit 34 to the cooling mechanism 27 g. The cooling unit 34 is electrically connected to a reference potential via the cooling mechanism 27g and the connection plate 10 g.

A 2 nd tightening portion 38 is fixed to the 2 nd protrusion 33d of the insulating portion 33. The 2 nd fastening portion 38 has a 3 rd portion 38a fixed to the 2 nd protrusion 33d and a 4 th portion 38b formed with a male screw screwed into the 2 nd small diameter portion 34b of the 2 nd bolt hole. The 3 rd portion 38a is wrapped around the 2 nd projecting portion 33d and welded to the 2 nd projecting portion 33d, thereby being firmly fixed to the 2 nd projecting portion 33 d. Further, the 4 th portion 38b is screwed into the 2 nd small diameter portion 34b, whereby the cooling portion 34 and the insulating portion 33 are fastened.

At this time, the cooling portion 34 is closely attached to and fixed to the 2 nd position 33b of the insulating portion 33. The 2 nd cover 33f surrounds the periphery of the cooling portion 34 so as to cover one end of the cooling portion 34. The 3 rd portion 38a is accommodated in the 2 nd large diameter portion 34a, and the 4 th portion 38b is accommodated in the 2 nd small diameter portion 34 b.

In the case where the insulating portion 33 is a ceramic containing alumina, it is preferable that the 2 nd fastening portion 38 includes an alloy containing nickel and cobalt. Accordingly, the insulating portion 33 and the 2 nd fastening portion 38 are formed of materials having close thermal expansion coefficients, and the influence of temperature change on the fixation by welding of the insulating portion 33 and the 2 nd fastening portion 38 can be suppressed.

In order to sufficiently adhere cooling portion 34 and insulating portion 33, the surface roughness Ra of the contact surface between cooling portion 34 and insulating portion 33 is preferably 6.3 μm or less. For example, it is preferably 3.2 μm. Further, the area of the contact surface between the cooling portion 34 and the insulating portion 33 is preferably 110mm²The above. For example, it is preferably set to 150mm²。

The cooling part 34 and the 2 nd position 33b of the insulating part 33 may be contacted via a metal sheet. The metal sheet may be, for example, a sheet of aluminum, copper or tin. The thickness of the metal sheet may be 10 μm or more and 30 μm or less. More preferably 10 μm or more and 20 μm or less.

Alternatively, the cooling part 34 and the 2 nd position 33b of the insulating part 33 may be contacted via a resin sheet. The resin sheet may be a sheet of silicone rubber or acrylic rubber, for example. The thickness of the resin sheet may be 10 μm or more and 1000 μm or less. For example, it may be 500 μm.

By using the metal sheet or the resin sheet, the air layer between the cooling portion 34 and the insulating portion 33 is reduced, and heat conduction from the insulating portion 33 to the cooling portion 34 is efficiently performed.

2.2 actions and effects

The heat generated in the pre-ionization capacitor C11 is radiated to the cooling portion 34 by heat conduction via the conductive portion 32 and the insulating portion 33. The 1 st position 33a of the insulating portion 33 is fixed by the 1 st fastening portion 37 in close contact with the conductive portion 32, and therefore heat conduction from the conductive portion 32 to the insulating portion 33 is efficiently performed. The cooling portion 34 is closely fitted and fixed to the 2 nd position 33b of the insulating portion 33 by the 2 nd tightening portion 38, and therefore heat conduction from the insulating portion 33 to the cooling portion 34 is efficiently performed.

The 1 st position 33a and the 2 nd position 33b are located at positions opposed to each other. Accordingly, even when the thermal conductivity of the insulating portion 33 is lower than that of the conductive portion 32 or the cooling portion 34, heat is efficiently radiated from the conductive portion 32 to the cooling portion 34.

The conductive portion 32 is electrically connected to a potential of the pulse-like high voltage output from the pulse power module 13, and the cooling portion 34 is electrically connected to a reference potential. However, the conductive portion 32 and the cooling portion 34 are electrically insulated from each other by the insulating portion 33. Thus, even if the potential of the conductive portion 32 and the potential of the cooling portion 34 are different, the conductive portion 32 can be cooled by the cooling portion 34.

The 1 st cover 33e of the insulating portion 33 covers one end of the conductive portion 32, and the 2 nd cover 33f of the insulating portion 33 covers one end of the cooling portion 34. This can suppress discharge between the conductive part 32 and the cooling part 34.

The insulating portion 33 is made of a material having a low dielectric constant. This can reduce the capacitance of the insulating portion 33, and can prevent the insulating portion 33 from functioning as a capacitor.

The other points are the same as those of the comparative example described with reference to fig. 1 to 3.

3. Cooling structure provided in preionization wiring section

3.1 Structure

Fig. 5A is a plan view showing the arrangement of the peaking capacitor and the pre-ionization capacitor in the laser device of embodiment 2. Fig. 5B is a sectional view taken along line VB-VB of fig. 5A. Fig. 5C is a cross-sectional view at line VC-VC of fig. 5A.

As shown in fig. 5B, the pre-ionization capacitor C11 includes a capacitor main body 41a, a 1 st electrode 41B, a 2 nd electrode 41C, and a covering 41d, respectively. The capacitor body 41a is located between the 1 st electrode 41b and the 2 nd electrode 41c, and is configured to have a predetermined capacitance between the 1 st electrode 41b and the 2 nd electrode 41 c. The covering 41d covers the capacitor main body 41a, a part of the 1 st electrode 41b, and a part of the 2 nd electrode 41 c.

One end of the conductive member 28a is fixed to the 2 nd electrode 41 c. In order to fix the conductive member 28a to the 2 nd electrode 41c, a bolt 28d penetrating the conductive member 28a is screwed into a bolt hole 41f formed in the 2 nd electrode 41 c. The other end of the conductive member 28a is fixed to the connection plate 20 b.

Thus, the 2 nd electrode 41C of the preionization capacitor C11 is electrically connected to the output terminal of the pulse-like high voltage output from the pulse power module 13 via the conductive member 28 a.

The 1 st electrode 41b is connected to a cooling structure including the preionization wiring portion 35b, the insulating portion 43, and the cooling portion 44. The preionization wiring portion 35b corresponds to a conductive portion in the present disclosure.

The preionization wiring portion 35b includes an external thread portion 35 g. The external screw portion 35g is screwed into the bolt hole 41e of the 1 st electrode 41b, whereby the pre-ionization wiring portion 35b and the 1 st electrode 41b are electrically connected. The preionization wiring portion 35b is made of a material such as copper having high conductivity.

Pre-ionization wiring 35b is introduced into the interior of laser cavity 10 via feed-through 36. The pre-ionization wiring portion 35b is electrically connected to the pre-ionization internal electrode 25 inside the laser cavity 10. Thereby, the 1 st electrode 41b is electrically connected to the pre-ionization inner electrode 25. The preionization internal electrode 25 is set to a potential between the potential of the pulse-like high voltage outputted from the pulse power module 13 and the reference potential.

The preionization wiring portion 35b has a through hole 35f between the position of the external thread portion 35g and the position of the feed-through hole 36.

The insulating portion 43 has a 1 st surface including the 1 st position 43a and a 2 nd surface including the 2 nd position 43 b. The 1 st surface and the 2 nd surface are surfaces opposite to each other. The 1 st position 43a and the 2 nd position 43b are positions opposed to each other. As shown in fig. 5C, the insulating portion 43 further has 1 st covers 43C and 43d protruding in the substantially normal direction of the 1 st surface in the vicinity of the 1 st position 43 a. As shown in fig. 5B, the insulating portion 43 further has 2 nd covers 43e and 43f protruding in the substantially normal direction of the 2 nd surface in the vicinity of the 2 nd position 43B.

The insulating portion 43 is preferably made of a material having a low dielectric constant. The dielectric constant of the insulating portion 43 is preferably 10 or less. For example, the insulating portion 43 is made of alumina having a dielectric constant of 8.4 or more and 9.9 or less or aluminum nitride having a dielectric constant of 8.5 or more and 8.6 or less.

A 1 st fastening portion 47 is fixed to the 1 st position 43a of the insulating portion 43. The 1 st tightening portion 47 includes a 5 th portion 47a located on one side in the penetrating direction of the through hole 35f, and a 6 th portion 47b located on the other side in the penetrating direction of the through hole 35 f. The 5 th portion 47a is welded to the 1 st location 43 a. The 5 th and 6 th parts 47a and 47b are formed of an integral bolt.

The 1 st fastening portion 47 further includes a nut 47 c. When the nut 47c is attached to the 6 th part 47b and rotated, it moves in a direction approaching the 5 th part 47a in accordance with the thread groove of the 6 th part 47 b. Thereby, the preionization wiring portion 35b and the insulating portion 43 are fastened. At this time, the preionization wiring portion 35b is closely attached to and fixed to the 1 st position 43a of the insulating portion 43. Further, the 1 st covers 43c and 43d sandwich 2 side faces of the pre-ionization wiring portion 35b in such a manner as to cover a part of the pre-ionization wiring portion 35 b. The nut 47c corresponds to part 7 in the present disclosure.

In the case where the insulating portion 43 is a ceramic containing alumina, the 1 st fastening portion 47 preferably includes an alloy containing nickel and cobalt. Accordingly, the insulating portion 43 and the 1 st fastening portion 47 are formed of materials having similar thermal expansion coefficients, and the insulating portion 43 and the 1 st fastening portion 47 can be prevented from being affected by temperature changes due to welding.

In order to sufficiently adhere the preionization wiring portion 35b and the insulating portion 43 to each other, the surface roughness Ra of the contact surface between the preionization wiring portion 35b and the insulating portion 43 is preferably 6.3 μm or less. For example, it is preferably 3.2 μm. Further, the area of the contact surface between the preionization wiring portion 35b and the insulating portion 43 is preferably 110mm²The above. For example, it is preferably set to 150mm²。

The 1 st position 43a of the pre-ionization wiring portion 35b and the insulating portion 43 may be contacted via a metal sheet. Alternatively, the 1 st position 43a of the pre-ionization wiring portion 35b and the insulating portion 43 may be contacted via a resin sheet. The material and thickness of the metal sheet or the resin sheet may be the same as those described in embodiment 1. By using a metal sheet or a resin sheet, the air layer between the preionization wiring portion 35b and the insulating portion 43 is reduced, and heat conduction from the preionization wiring portion 35b to the insulating portion 43 is efficiently performed.

The cooling portion 44 includes bolt holes 44 a. The bolt 46 penetrating the insulating portion 43 is screwed into the bolt hole 44a, whereby the cooling portion 44 and the insulating portion 43 are fastened.

At this time, the cooling portion 44 is closely attached to and fixed to the 2 nd position 43b of the insulating portion 43. Further, the 2 nd covers 43e and 43f sandwich 2 side faces of the cooling portion 44 so as to cover a part of the cooling portion 44.

The cooling portion 44 is connected to the cooling mechanism 27f at a portion different from the portion fastened to the insulating portion 43. This enables heat conduction from the cooling unit 44 to the cooling mechanism 27 f. The cooling unit 44 is electrically connected to the reference potential via the cooling mechanism 27f and the connection plate 10 f.

In order to sufficiently adhere the cooling portion 44 and the insulating portion 43 to each other, the surface roughness Ra of the contact surface between the cooling portion 44 and the insulating portion 43 is preferably 6.3 μm or less. For example, it is preferably 3.2 μm. Further, the area of the contact surface between the cooling portion 44 and the insulating portion 43 is preferably 110mm²The above. For example, it is preferably set to 150mm²。

The cooling portion 44 and the 2 nd position 43b of the insulating portion 43 may be contacted via a metal sheet. Alternatively, the cooling portion 44 and the 2 nd position 43b of the insulating portion 43 may be contacted via a resin sheet. The material and thickness of the metal sheet or the resin sheet may be the same as those described in embodiment 1. By using the metal sheet or the resin sheet, the air layer between the cooling portion 44 and the insulating portion 43 is reduced, and heat conduction from the insulating portion 43 to the cooling portion 44 is efficiently performed.

3.2 actions and effects

The heat generated in the pre-ionization capacitor C11 is radiated to the cooling portion 44 by heat conduction via the pre-ionization wiring portion 35b and the insulating portion 43. The 1 st tightening portion 47 tightly fits and fixes the preionization wiring portion 35b to the 1 st position 43a of the insulating portion 43, and therefore, heat conduction from the preionization wiring portion 35b to the insulating portion 43 is efficiently performed. The bolt 46 causes the cooling portion 44 to be closely attached to and fixed to the 2 nd position 43b of the insulating portion 43, and therefore heat conduction from the insulating portion 43 to the cooling portion 44 is efficiently performed.

The 1 st position 43a and the 2 nd position 43b are located at positions opposed to each other. Accordingly, even when the thermal conductivity of the insulating portion 43 is lower than that of the preionization wiring portion 35b or the cooling portion 44, heat is efficiently radiated from the preionization wiring portion 35b to the cooling portion 44.

The preionization wiring portion 35b is electrically connected to the preionization internal electrode 25 having a potential capable of generating corona discharge for preionizing a part of the laser gas, and the cooling portion 44 is electrically connected to a reference potential. However, the preionization wiring portion 35b and the cooling portion 44 are electrically insulated from each other by the insulating portion 43. Thus, even if the potential of the preionization wiring portion 35b and the potential of the cooling portion 44 are different, the preionization wiring portion 35b can be cooled by the cooling portion 44

The 1 st covers 43c and 43d of the insulating section 43 cover a part of the pre-ionization wiring section 35b, and the 2 nd covers 43e and 43f of the insulating section 43 cover a part of the cooling section 44. This can suppress discharge between pre-ionization wiring portion 35b and cooling portion 44.

The insulating portion 43 is made of a material having a low dielectric constant. This can reduce the capacitance of the insulating portion 43, and can prevent the insulating portion 43 from functioning as a capacitor.

Otherwise, the same as embodiment 1 described with reference to fig. 4A and 4B.

In the above description, the case where the cooling portion 44 and the insulating portion 43 are fastened by the bolt 46 has been described, but the present disclosure is not limited thereto. Similarly to the fastening of the preionization wiring portion 35b and the insulating portion 43, the cooling portion 44 and the insulating portion 43 may be fastened by a fastening portion, not shown, which is welded to the 2 nd position 43b of the insulating portion 43 and penetrates through a through hole of the cooling portion 44.

4. Others

4.1 Structure of reference example

Fig. 6A is a plan view showing the arrangement of the peaking capacitor and the pre-ionization capacitor in the laser device of the reference example. Fig. 6B is a cross-sectional view at line VIB-VIB of fig. 6A.

In the reference example, the 1 st electrode 41B shown in fig. 6B is connected to a cooling structure including the preionization wiring portion 35c and the cooling device 50. The pre-ionization wiring portion 35c is electrically connected to the pre-ionization internal electrode 25 inside the laser cavity 10. The potential of the preionization internal electrode 25 is a potential between the potential of the pulse-like high voltage outputted from the pulse power module 13 and the reference potential.

The cooling device 50 includes a supply/discharge portion 50a, a cooling pipe portion 50b, an insulating sheet 50c, and a covering portion 50 d. The supply/discharge portion 50a and the cooling tube portion 50b are electrically connected to, for example, a reference potential.

The supply/discharge unit 50a is a pipe connected to a pump or the like, not shown. The supply/discharge unit 50a supplies the cooling medium such as water to the cooling pipe unit 50b and discharges the cooling medium passing through the cooling pipe unit 50 b.

The cooling pipe portion 50b is a pipe made of a material having high thermal conductivity and disposed around the preionization wiring portion 35 c. The cooling pipe portion 50b passes the cooling medium supplied from the supply/discharge portion 50 a. At this time, heat is conducted from pre-ionization wiring portion 35c to the cooling medium. The cooling medium having passed through the cooling pipe portion 50b is discharged through the supply/discharge portion 50 a.

The insulating sheet 50c is disposed between the preionization wiring portion 35c and the cooling tube portion 50 b. The insulating sheet 50c is preferably made of a material having high thermal conductivity while ensuring electrical insulation.

The covering portion 50d is made of an insulating resin, and covers a part of the supply/discharge portion 50a and the cooling pipe portion 50 b. The coating portion 50d is configured to suppress discharge between the supply/discharge portion 50a and the cooling tube portion 50b and the pre-ionization wiring portion 35 c.

4.2 actions and effects of reference example

The heat generated in the preionization capacitor C11 is radiated to the cooling tube portion 50b by heat conduction via the preionization wiring portion 35C and the insulation sheet 50C, and further radiated to the supply/discharge portion 50a by the cooling medium. By using the insulating sheet 50c having high thermal conductivity, heat conduction from the preionization wiring portion 35c to the cooling pipe portion 50b is efficiently performed.

The preionization wiring portion 35c is electrically connected to the preionization internal electrode 25 having a potential capable of generating corona discharge for preionizing a part of the laser gas, and the supply/discharge portion 50a and the cooling tube portion 50b are electrically connected to a reference potential. However, the preionization wiring portion 35c is electrically insulated from the supply/discharge portion 50a and the cooling pipe portion 50b by the insulating sheet 50c and the covering portion 50 d. Thus, even if the potential of the preionization wiring portion 35c is different from the potentials of the supply/discharge portion 50a and the cooling duct portion 50b, the preionization wiring portion 35c can be cooled by the cooling device 50.

The other points are the same as those of embodiment 2 described with reference to fig. 5A to 5C.

4.3 supplement

In embodiment 1, the case where the 1 st electrode 31b electrically connected to the output terminal of the pulse power module 13 is cooled is described. In embodiment 2 and the reference example, the case where the 1 st electrode 41b electrically connected to the preionization internal electrode 25 is cooled is described. However, the present disclosure is not limited thereto. Both the electrode electrically connected to the output terminal of the pulse power module 13 and the electrode electrically connected to the preionization internal electrode 25 may be cooled. Any 2 of the cooling configurations of embodiment 1, embodiment 2, and the reference example may be combined.

The above description is not limiting, but is simply illustrative. Accordingly, it will be apparent to those skilled in the art that modifications can be made to the embodiments of the disclosure without departing from the scope of the appended claims.

The terms used in the present specification and the appended claims should be construed as "non-limiting". For example, a term "comprising" or "includes" should be interpreted as "not being limited to the portion described as being included". The term "having" should be interpreted as "not limited to the portion described as having". Also, the modifier "a" or "an" recited in the specification and the appended claims should be construed to mean "at least one" or "one or more".