JP3051930B1 - Gas excitation device - Google Patents

Abstract

An object of the present invention is to provide a gas excitation device capable of directly injecting electrons from a ferroelectric cathode into a gas and capable of high output, high efficiency and high repetition operation. I have. A gas excitation device according to the present invention excites a gas by driving electrons emitted from an electron beam source into the gas. The electron beam source emits electrons by applying a pulse voltage to the ferroelectric. Thus, electrons can be directly injected into the gas from the ferroelectric cathode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas excitation device used in, for example, a gas laser device. A gas laser device excites a laser medium gas and installs an optical resonator or the like around the gas to convert the energy stored in the gas into laser light and extract it. In the semiconductor industry and the like, a high repetition rate laser device having an output energy of about joule per pulse has already been widely used. Gas laser devices are also promising candidates for future fusion laser drivers. In the field of high power lasers, high repetition functions are not yet provided, but large-diameter gas laser devices for research have already been developed and used for experiments. In addition, the present invention is very useful for improving the performance of an electron emission source in a vacuum or gas, such as a display, a chemical reaction device, various light sources, and an ozone source.

[0002]

2. Description of the Related Art The main conventional gas excitation method is to directly inject electric energy into a gas. Electrons were drawn from the cathode by an electric field between the cathode and the anode, accelerated to generate a high-energy electron beam, and the electron beam was injected into the gas to excite the gas. Based on this method, conventional gas laser devices are roughly classified into two types, an “electron beam excitation type” and a “discharge excitation type”. FIG. 6 shows a configuration example of the prior art “electron beam excitation type”, and FIG. 7 shows a configuration example of the conventional technology “discharge excitation type”.

In the conventional electron beam excitation type apparatus shown in FIG. 6, a mechanism for generating an electron beam is roughly divided into two stages. First, electron emission from the cathode surface and second
The acceleration of the emitted electrons. In electron emission, a large number of minute projections are provided on the cathode surface (electron emission surface 20) serving as an electron source, and a strong electric field is generated at the countless projection tips.
As a result, electrons are emitted from the tip of the projection by a strong electric field (several MV / cm or more) at the tip of the minute projection (field emission).

Next, plasma is formed on the cathode surface (electron emission surface 20) by the emitted electrons, and the entire surface is covered with the plasma. This plasma substantially serves as a cathode for electron emission. Electrons are easily extracted from the cathode surface plasma by the electric field between the opposing anode and the surface plasma. In FIG. 6, the gas retaining thin film 10 is grounded, and this thin film functions as an anode. That is, electrons are accelerated between the cathode 21 and the gas retaining thin film 10 in a vacuum (vacuum acceleration unit 9), and the high energy electron beam 4 is generated. The generated electron beam is injected into the laser gas 5 at about atmospheric pressure through the gas holding thin film 10. As a result, the laser gas molecules are excited by the collision of electrons.

In an electron beam excitation type device represented by FIG. 6, a typical cathode area (electron emission surface 20) has a length of 10 mm.
It is about 0cm and 10cm wide. The cathode 21 has an acceleration voltage source 11
And apply a negative high voltage pulse (-several hundreds to -1000 kV, pulse width: several tens to several hundred ns). A metal thin film is usually used for the anode (gas holding thin film 10), and separates a vacuum part from a laser gas at about atmospheric pressure. The dimensions of the anode thin film are usually
It is about 10 microns thick, 100 cm long and 30 cm wide. Actually, the diaphragm installed at the boundary between the vacuum and the gas is divided into two layers, a metal thin film for the anode and a thin film for maintaining the gas pressure.
They are often placed facing each other at intervals of about several centimeters, and both are grounded. In this case, the electron beam is transmitted through the two metal thin films from the vacuum and is injected into the gas. The volume of the gas to be excited reaches 1 m in diameter and 2 m in length in a large device.

On the other hand, in the prior art discharge excitation type apparatus shown in FIG. 7, a discharge tube is filled with a laser gas and the gas is excited by a discharge between the electrodes. In FIG. 7, a cathode 21 and an anode 12 are provided on both sides of a gas container 6, and the space between them is filled with a laser gas 5. The width and interval of the electrodes are both about several cm, and the length of the electrodes is about 50 to 100 cm. A high voltage (several tens of kV) is applied between the electrodes by connecting the accelerating voltage source 11 to the cathode 21, and the medium gas is excited by glow discharge between the electrodes. To obtain a stable glow discharge,
At the start of discharge, it is necessary to uniformly generate a sufficient amount of electric charge in the discharge region. For this purpose, preliminary ionization of the laser gas 5 is performed by X-ray irradiation or ultraviolet irradiation.

[0007]

In a conventional electron beam pumped gas laser apparatus, the thin film (gas holding thin film 10 in FIG. 6) separating the vacuum and the laser medium gas has a large electron accumulation / scattering loss, and this energy is high. Losses have severely limited the efficiency of the overall device. At the same time, when the laser device is operated for a long time, there are problems such as vacuum leakage at the thin film seal portion separating the gas and the vacuum, reduction in mechanical strength of the thin film, corrosion of the thin film by the laser gas, and contaminating the laser gas. In general, an electron beam excitation type device is easy to increase the diameter, and is suitable for generating a large output laser beam. However, since the gas retaining thin film 10 was used,
It has been impossible to continuously generate high-power laser light with high efficiency under a high repetition operation for a long time.

Further, in the conventional electron beam excitation type apparatus, generation of an electron beam is greatly restricted by the above-mentioned electron emission mechanism. In other words, since the amount of electrons emitted from the cathode surface depends on the shape, size, and number density of the microprojections,
If these geometrical conditions are insufficient, it takes time for the cathode surface plasma to be generated by the emitted electrons. Therefore, it was difficult to shorten the rise time of the electron beam current waveform (about 40 to 50 ns). Further, since the impedance of the electron beam generator depends on the electrode area / interval and the applied voltage, the amount of electron beam current is defined under these conditions, and it is difficult to freely expand the electron beam emission area. Further, since the cathode surface plasma evolves toward the anode with time, the substantial electrode spacing decreases with time, resulting in a temporal decrease in impedance. For this reason, it was difficult to keep the electron beam acceleration voltage and the current value constant during the voltage application time.

[0009] Even in a discharge excitation type apparatus, there is a difficulty in emitting electrons from the electrodes. In this type of gas laser device, it is necessary to apply a high electric field between the electrodes filled with gas in order to emit electrons from the cathode, which makes glow discharge in the gas unstable and shifts to arc discharge. There was a drawback that it was easy to do. Although the discharge excitation type apparatus is excellent in high repetition operation, the discharge instability makes it impossible to increase the diameter of the discharge tube, that is, to generate a large area and large output laser beam.

Therefore, the present invention solves the above-mentioned problems, and enables electrons to be directly injected into a gas from a ferroelectric cathode, thereby achieving a large-power, high-efficiency, high-repetition-rate gas excitation apparatus. It is intended to provide.

[0011]

According to the present invention, a ferroelectric or an element composed of a ferroelectric and an electrode is used as an electron beam generating source. However, the size and shape of the ferroelectric in the electron beam source and the method of forming the electrodes are not limited to one. Also, a mechanism for extracting electrons from the ferroelectric is not necessarily required at a location separated from the ferroelectric.

As one method for producing an electron emission source using a ferroelectric substance, an electron emission element is formed by sandwiching a ferroelectric plate between two electrode plates (FIGS. 1 to 5). The electron emission surface of the ferroelectric plate is covered with an electrode having a surface shape such as a slit so that a part of the ferroelectric is exposed to the outside, or a metal vapor-deposited film or a thin enough film through which electrons can pass. Is covered with a metal thin film or the like and grounded (slit electrode 2 in FIGS. 1 to 5). On the back side, the entire surface of the ferroelectric is completely covered with a uniform electrode (FIG. 1).
5 is connected to a power supply for applying a high voltage pulse described later (inversion voltage source 8).

First, a positive pulse is applied to the inversion electrode 3 on the back side, and electrons are accumulated on the slit-like electrode or metal thin film (slit electrode 2) on the front side. In the case of a slit-shaped electrode, electrons also accumulate on the ferroelectric surface between the slits. Next, the voltage polarity of the inversion electrode 3 is rapidly inverted to negative,
Invert the polarization in the dielectric. Due to this rapid polarization reversal, in the case of a slit-shaped electrode, the electrons accumulated on the ferroelectric surface in the gap between the slits are electrostatically ejected to the outside through the gap between the slits. In the case of an electrode composed of a metal deposition film or a metal thin film, the electrons accumulated in the thin film are ejected to the outside electrostatically directly from the thin film surface or through the thin film. The ejected electrons are directly injected into the gas and collide with gas molecules to excite the gas.

At the time of electron ejection, if conditions permit, only a negative pulse may be applied to the inversion electrode 3 from the beginning, and a similar effect may be produced without inverting the voltage on the way. If necessary, the electrons emitted from the ferroelectric may be accelerated by an external electric field (FIGS. 2, 3). Also, the trajectory, cross-sectional shape, or size of the emitted electron beam may be controlled at any location (FIGS. 4, 5).

In this way, it is possible to emit electrons directly from the ferroelectric into the gas while the ferroelectric is in contact with the gas. As a result, the following items or operations become possible.

(1) Since direct electron emission into the gas becomes possible, the gas holding thin film 10 used in the electron beam pumped gas laser apparatus is removed, and the electron beam is directly introduced into the gas without passing through a vacuum. A driving gas excitation method becomes possible. By adopting this method, various problems caused by the gas retaining thin film have been solved. (2) In the electron beam excitation type apparatus, generation of cathode surface plasma is not required when electrons are emitted from the cathode into a vacuum. Therefore, in the conventional apparatus, the rise time of the electron beam current can be greatly reduced. (3) In the electron beam excitation type device, the problem of plasma propagation from the cathode surface to the anode is eliminated. Therefore, in the conventional apparatus, the temporal fluctuation of the acceleration voltage and the current value of the electron beam is reduced. (4) In the electron beam excitation type and discharge excitation type devices, the existing specified conditions (electrode area, electrode spacing, electric field strength, etc.) for electron beam generation are greatly relaxed.
It becomes very easy to enlarge the cross section of the emitted electron beam. (5) In the discharge excitation type device, since a strong electric field for emitting electrons is not required, the voltage between the electrodes can be reduced, and the stability of glow discharge is improved. (6) Electron emission becomes very easy in the discharge excitation type device, and the pre-ionization of gas, which is essential in the conventional device, becomes unnecessary.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, according to the present invention, electrons are emitted from a ferroelectric element as shown in FIGS.
A gas laser device that generates an electron beam and excites a gas into the gas will be described in detail.

FIG. 1 shows a first configuration example in which a ferroelectric substance is brought into contact with a gas and electrons are emitted from the ferroelectric substance directly into the gas to excite the gas. Here, a plate-shaped ferroelectric 1
2 shows a configuration example in which both surfaces are sandwiched between two electrodes. The thickness of the ferroelectric can be used if it is several hundred microns to about 1 mm, but may be larger depending on the purpose and method of use.
The electron emission surface is covered with a slit-shaped electrode (slit electrode 2) so that a part of the ferroelectric is exposed and grounded. It is desirable that the width of the slit (the width of the exposed surface of the ferroelectric substance) be equal to or less than the thickness of the ferroelectric substance 1. However, if the slit width is zero, no electrons are emitted. Since it is more advantageous for the electron emission that the thickness of the slit electrode is sufficiently thinner than the thickness of the ferroelectric substance, the slit electrode may be formed by metal evaporation or a sufficiently thin metal mesh. Alternatively, without using a slit electrode or the like, the entire electron emission surface may be covered with a metal vapor-deposited film or a metal thin film that is thin enough to transmit electrons. On the other hand, on the opposite back surface, the entire surface of the ferroelectric is completely covered with the electrode (inversion electrode 3).

An inversion voltage source 8 is connected to the inversion electrode 3 on the back surface, and a bipolar wave as shown is applied to the inversion electrode.
The magnitude of the applied voltage is determined by the dielectric breakdown strength of the ferroelectric, and is about several kV per 1 mm of the thickness of the ferroelectric. The pulse width depends on the purpose of use, but several tens of ns for both positive and negative polarity
Or more.

First, when a positive voltage is applied to the inversion electrode 3, electric charges are accumulated on both surfaces of the ferroelectric 1 in the same manner as a normal capacitor is charged. On the side of the slit electrode 2 serving as an electron emission surface, electrons also accumulate on the ferroelectric surface in the gap between the slits.

Next, when the polarity of the inversion electrode 3 is rapidly inverted from positive to negative, the polarization inside the ferroelectric 1 is inverted, and a negative polarization charge is generated inside the ferroelectric near the slit electrode 2 side. As a result, the electrons accumulated on the ferroelectric surface on the side of the slit electrode are electrostatically ejected to the outside through the gap of the slit. When the electrode on the electron emission surface side is formed of a metal deposition film, a metal thin film, or the like, electrons are ejected directly from the thin film surface or through the thin film. The time during which electrons are ejected is approximately equal to the negative pulse width.
The ejected electrons are directly injected into the laser gas 5,
The laser gas is excited by colliding with gas molecules. As a result, the laser beam 7 can be extracted in the direction shown.

According to this example, the gas holding thin film used in the conventional electron beam excitation type device becomes unnecessary, and the electron beam can be directly injected into the gas without passing through a vacuum. By adopting this method, various problems caused by the gas retaining thin film are solved,
The energy transfer efficiency of the device is also greatly improved. Also in the conventional discharge excitation type device, electron emission becomes very easy, the stability of discharge is obtained, and the device can have a large diameter and a large output.

FIG. 2 shows a second configuration example in which electrons are once emitted from a ferroelectric into a vacuum and then injected into a gas through a thin film. The mechanism of emitting electrons from the ferroelectric is exactly the same as that shown in FIG. That is, an inversion voltage source 8 is connected to the inversion electrode 3 on the back surface, and a bipolar pulse as shown is applied to the inversion electrode 3 to electrostatically eject electrons from the slit electrode 2 on the front surface.

In the second configuration example, the acceleration voltage source 11 is connected to both the slit electrode 2 and the inversion electrode 3 on both sides of the ferroelectric 1.
And apply a negative high voltage (up to several hundred kV). Therefore, the ground gas holding thin film 10 (metal thin film) functions as an anode. Electrons emitted from the slit electrode side of the ferroelectric surface are accelerated by a vacuum accelerating unit 9 to become a high energy electron beam 4, which is injected into a laser gas 5 through a gas holding thin film 10. Since the gas retaining thin film is typically several tens of microns thick, the electron beam penetrates the thin film and enters the laser gas. When a high-energy electron beam is required, it is often advantageous to once discharge the electrons into a vacuum, accelerate them, and then drive them through a thin film into a gas, as in this example.

The present invention greatly contributes to the improvement of the characteristics of the electron beam generator in the conventional electron beam excitation type device.
In the conventional apparatus, there are disadvantages such as a delay in rising of an electron beam current waveform, a change in a voltage and a current value within an electron beam duration time (about several tens to several hundreds of ns), and difficulty in expanding an electron beam cross-sectional area. was there. These were all due to the difficulty of emitting electrons from the cathode. That is, in the electron beam excitation type device, a large number of minute protrusions (height, width, and height) are formed on the surface of the cathode (electron emission surface 20 in FIG. 6) installed in a vacuum.
An electric field is emphasized at the tip of the protrusion (several MV / cm or more) by providing a few tens to several hundreds of microns (electron emission), and electrons are emitted into vacuum from the local high electric field part (field emission). Accordingly, since the amount of electron emission depends on the shape, size, area density of the number of protrusions, etc. of the fine protrusions on the cathode surface, good electron emission characteristics can be obtained if the geometric conditions of the cathode surface are insufficient. Did not. In addition, a waiting time occurs when the plasma covers the cathode surface after the electrons are emitted from the microprojections, which makes it difficult to shorten the rising time of the electron beam waveform (about 40 to 50 ns). Further, as the cathode surface plasma progresses toward the anode, the impedance of the electron beam generator (between the cathode and the anode) decreases with time, and as a result, the electron beam voltage and current tend to decrease in the latter half of the pulse. . The difficulty in increasing the electrode area was also due to these restrictions.

In the second configuration example shown in FIG. 2, it is not necessary to generate a strong electric field on the surface of the cathode when emitting electrons, and the emission of electrons into a vacuum becomes very easy. In addition, since generation of cathode surface plasma is not required, various restrictions on electron beam generation in the conventional apparatus are greatly reduced. In other words, even when a gas-retaining thin film is used in an electron beam excitation type apparatus as before, it has been difficult to shorten the rising time of the electron beam current waveform, stabilize the electron beam voltage and current value, enlarge the electrode area, And so on, and the characteristics of the device can be greatly improved. By following this second configuration example,
Further, it is possible to design a high-performance electron beam excitation type apparatus having a large diameter and a large output.

FIG. 3 shows a third configuration example in which electrons are directly emitted into a gas and electrons are accelerated in the gas. The mechanism of emitting electrons from the ferroelectric is exactly the same as in the first and second configuration examples. As shown in FIG. 3, an electron emission source composed of a ferroelectric substance 1 is provided so as to face an anode 12, and the space between the two is filled with a laser gas 5. An acceleration voltage source 11 is connected to the anode 12 to apply a positive voltage of several tens of kV to the ferroelectric 1.
The electrons emitted from the gas are accelerated in the laser gas 5 and the laser gas 5 is excited. Laser light 7 is extracted in the direction shown.

The third configuration example corresponds to an improvement of the conventional discharge excitation type gas laser device. An advantage of this configuration example is that it is not necessary to generate a strong electric field on the cathode surface for electron emission. For this reason, the voltage between electrodes can be reduced in the discharge excitation type device, and the stability of glow discharge is significantly improved. Further, by facilitating the electron emission, the gas pre-ionization mechanism which has been indispensable in the discharge excitation type device can be eliminated, and the device can be greatly simplified. As a result, the electrode area and the electrode interval can be set relatively freely, and a large-diameter, large-power discharge-excited gas laser device excellent in discharge stability, which has been impossible so far, is realized.

FIG. 4 shows a fourth configuration example in which an electron beam is controlled by an electric field in the first configuration example. In FIG. 4, the electric field generating electrodes 13 are provided on the upper and lower surfaces of the gas container 6.
Is installed, and a high voltage is applied by an electric field generation voltage source 14 to generate an electric field 15 in the vertical direction. The trajectory, cross-sectional shape, and size of the electron beam 4 are controlled by the electric field 15.
The number of the electric field generating electrodes 13 is not limited to two. Electric field 15
Is not limited to the vertical direction. Further, it may be used in combination with the electron beam control (FIG. 5) using a magnetic field described later. This electron beam control method may be applied to not only the first configuration example but also other configuration examples.

FIG. 5 shows a fifth configuration example in which the electron beam is controlled by a magnetic field in the first configuration example. In FIG. 5, a magnetic field generating coil 18 is provided around the gas container 6 so as to surround the electron beam 4, and a large current is caused to flow by an exciting current source 17 to generate a magnetic field 16 in parallel with the electron beam 4. The trajectory, cross-sectional shape and size of the electron beam 4 are controlled by the magnetic field 16. The number of the magnetic field generating coils 18 is not limited to two. The direction of the magnetic field 16 is not limited to the direction of the electron beam 4. Further, it may be used in combination with the above-described electron beam control using an electric field (FIG. 4). This electron beam control method may be applied to not only the first configuration example but also other configuration examples.

[0031]

When the present invention is applied to an electron beam pumped gas laser apparatus, it is possible to remove a gas retaining thin film which has been indispensable in the same kind of apparatus, and a completely new gas pumped large diameter gas laser apparatus can be obtained. Realize. In this new system, the accumulation of electrons in the thin film
Problems such as scattering loss, thin film breakage, vacuum leak, thin film corrosion, gas contamination, etc. are eliminated at once. As a result, a high-efficiency, high-repetition operation of the high-output gas laser device over a long period of time becomes possible.

Even when the present invention is applied to a conventional electron beam excitation type device using a gas retaining thin film,
The rising time of the electron beam current can be reduced, the stability of the electron beam voltage and the current can be improved, and the electrode area can be very easily enlarged. As a result, it is possible to further enhance the performance, enlarge the diameter, and increase the output of the electron beam excitation type apparatus.

When the present invention is applied to a discharge-excited gas laser apparatus, the strong electric field on the cathode surface required for electron emission becomes unnecessary, and the electric field between the electrodes can be reduced. To improve. In addition, since it is very easy to increase the electrode area and interval, the gas volume can be greatly increased. Further, since a gas pre-ionization mechanism is not required, the apparatus can be greatly simplified. As a result of these,
A large-diameter and large-output discharge-excitation gas laser device, which has been difficult until now, is realized.

As described above, a completely new high-performance gas laser device capable of high output, high efficiency, and high repetition operation, which can compensate for the disadvantages of the conventional electron beam excitation type and discharge excitation type and combines the advantages, is realized. The present invention is intended to realize a high-output and high-efficiency gas laser driver for future fusion requiring high repetition operation, or to increase the power and diameter of a high-repetition laser device already widely used in industry. Contribute greatly.

[Brief description of the drawings]

FIG. 1 shows a first configuration example of the present invention, in which an electron is directly emitted from a ferroelectric substance into a gas to excite the gas.

FIG. 2 shows a second configuration example of the present invention, in which electrons are temporarily released from a ferroelectric substance into a vacuum, accelerated, and then passed through a thin film and injected into a gas.

FIG. 3 shows a third configuration example of the present invention, in which electrons emitted directly from a ferroelectric substance into a gas are accelerated in the gas.

FIG. 4 shows a fourth configuration example of the present invention, and shows an example in which the trajectory, cross-sectional shape, and size of an electron beam are controlled by an electric field in the first configuration example.

FIG. 5 illustrates a fifth configuration example of the present invention, and illustrates an example in which the trajectory, cross-sectional shape, and size of an electron beam are controlled by a magnetic field in the first configuration example.

FIG. 6 shows a conventional electron beam pumped gas laser device.

FIG. 7 shows a conventional discharge excitation type gas laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ferroelectric 2 Slit electrode 3 Inversion electrode 4 Electron beam 5 Laser gas 6 Gas container 7 Laser light 8 Inversion voltage source 9 Vacuum acceleration part 10 Gas holding thin film 11 Acceleration voltage source 12 Anode 13 Electric field generation electrode 14 Electric field generation voltage source 15 Electric field 16 Magnetic field 17 Excitation current source 18 Magnetic field generating coil 19 Insulating plate 20 Electron emission surface 21 Cathode

Claims (10)

(57) [Claims] 1. An electron emitted from an electron beam source
A gas excitation apparatus for injecting into a laser gas for excitation, wherein the electron beam generating source emits electrons by applying a pulse voltage to a ferroelectric substance. 2. The gas excitation according to claim 1, wherein the electron beam generating source has a ferroelectric plate sandwiched between two electrode plates, and a pulse voltage is applied to the two electrode plates. apparatus. 3. One of the two electrode plates is configured so that a part of the ferroelectric is exposed to the outside to emit electrons from the exposed surface, or to a degree that allows the electrons to pass therethrough. 3. An electron is emitted from a sufficiently thin metal deposition film or metal thin film, and electrons are emitted from the metal thin film.
3. The gas excitation device according to claim 1. 4. A bipolar pulse wave having a polarity reversed from a positive polarity to a negative polarity is applied to electrodes on the back surface side of the two electrode plates, and the electrode plate on the electron emission surface side is grounded. The gas excitation device according to claim 3, wherein 5. An bipolar bipolar pulse voltage that reverses from a positive polarity to a negative polarity is applied to electrodes on the back side of the two electrode plates, and the electrode plate on the electron emission surface side is grounded and accelerated. The gas excitation device according to claim 3, further comprising an anode connected to a voltage source. 6. The method according to claim 1, wherein electrons are extracted from the ferroelectric substance while the ferroelectric substance is in contact with the gas, and the electrons are directly injected from the ferroelectric substance into the gas. 3. The gas excitation device according to claim 1. 7. The gas excitation according to claim 1, wherein electrons are once released from the ferroelectric into a vacuum, and then the electrons are injected into the gas through a gas retaining thin film. apparatus. 8. A bipolar pulse wave voltage such that a back electrode is inverted from a positive polarity to a negative polarity with respect to a surface electrode on an electron emission side, between said two electrode plates, and an acceleration voltage source is provided. To the surface electrode to make both electrode plates negative high potential,
8. The gas excitation device according to claim 7, wherein the gas holding thin film is grounded to function as an anode. 9. A pair of electrodes for controlling the trajectory, cross-sectional shape, and size of the emitted electron beam by an electric field,
4. A voltage is applied between the electrodes.
9. The gas excitation device according to any one of 8. 10. The apparatus according to claim 1, further comprising a magnetic field generating coil for controlling the trajectory, cross-sectional shape, and size of the emitted electron beam by a magnetic field, and applying a current to the coil. A gas excitation device according to any one of the above.