WO2007142419A1

WO2007142419A1 - Klystron oscillator using cold cathode electron gun, and oscillation method

Info

Publication number: WO2007142419A1
Application number: PCT/KR2007/002579
Authority: WO
Inventors: Seok Gy Jeon; Yun Sik Jin; Sun Shin Jung; Young Wook Choi; Min Sup Hur
Original assignee: Korea Electro Technology Research Institute
Priority date: 2006-06-02
Filing date: 2007-05-29
Publication date: 2007-12-13
Also published as: KR20070115404A

Abstract

Disclosed is a cold cathode klystron oscillator and the oscillation method thereof. The cold cathode klystron oscillator according to the present invention comprises an electron source by a cold cathode that emits a primary electron; a first grid that focuses and accelerates an electron beam emitted in the electron source; a second grid that focuses and accelerates the electron beam passing through the first grid, and includes a resonator that converts a part of the mechanical energy of the electron beam passing through the first grid into an electromagnetic wave energy; and a secondary electron cold cathode that generates a secondary electron by colliding the electron beam passing through the second grid. Here, the focusing and the acceleration of the electron beam passing through the first grid and the second grid are made through a DC power supply.

Description

[DESCRIPTION] [invention Title]

KLYSTRON OSCILLATOR USING COLD CATHODE ELECTRON GUN, AND OSCILLATION METHOD

[Technical Field]

The present invention relates to a klystron oscillator and oscillation method thereof, particularly, to a klystron oscillator using a cold cathode electron gun and the oscillation method thereof, which is capable of stably emitting a linear electron beam having a high current density by adding the electron amplification phenomenon due to the secondary electron emission.

[Background Art]

The electron beam that focuses electrons in a space is widely used for various industries and research equipments such as a RF oscillator and amplifier, a display, an accelerator, an electron microscope, a sensor, and all kinds of processing tools. The method for making the electron beam is various, but the currently using method is the mode in which a thermoelectron emitted from a metal surface in heating the metal is used by accelerating the thermoelectron. Contrary to the hot cathode electron gun, a cold cathode electron gun in which electrons can be obtained through the field emission by just applying a voltage without heating.

Fig. 1 is a drawing showing the structure of a cold cathode electron gun of the related art . Here, Field Emitter Arrays (hereinafter, FEAs) 110 are laminated onto a cathode 100, while the voltage Vl is applied to a grid 130 as an anode to emit the electron beam to be focused and accelerated. This cold cathode electron gun has the advantage that it requires a small consumable power as it does not need the process of heating up a cathode like the hot cathode electron gun and the structure is simple.

Particularly, the FEAs cold cathode electron gun in Fig. 1 has the advantage in that a protrusion 110 in which the field emission of the micrometer or the nano meter scale is facilitated, and the electrode of the micro meter scale can be utilized, thereby, the size of all kinds of the devices using the electron gun can be conspicuously reduced and the pre-modulated electron beam can be obtained with a small voltage of several volts . In addition, recently, it succeeded to process the cold cathode electron gun using the carbon nanotube and the vacuum triode of the micro meter scale using the MEMS (Micro Electro-Mechanical System) on the silicon wafer. Further, the research for developing the micro type vacuum microelectronic device in the tera-herts (THz) band progresses by using such technology.

However, in a part of microwave band, such technology has very much problems which have not yet solved in spite of the experimental success. Particularly, in the vacuum microelectronic device of the micro meter scale, the electric current density of the electron beam for the electromagnetic wave oscillation is more higher than the current density value which can be stably obtained through the FEAs cold cathode electron gun. This problem is one of the most difficult problems that have not yet solved in spite of the long research.

Additionally, the effort of replacing the conventional hot cathode electron gun has been actively progressed in various technical fields such as the conventional CRT, the FED (Field Emission Display) which has the advantage of the high luminous efficiency and the broad viewing angle as it is operated by the cathode luminescence like the Braun tube and of implementing with the thin flat board form. However, like the vacuum microelectronic device which mostly uses the cold cathode, the physical property of the electron beam which is obtained through the cold cathode is not so much sufficient that it can not be replaced with the conventional hot cathode . At present, the electron beam which has the energy of several hundreds keV can be made by using the hot cathode electron gun, while the current reaches several hundreds ampere. The current density of the electron beam emitted from the surface of the hot cathode reaches, approximately, 1O A / cm2. In the meantime, FEAs cold cathode electron gun can emit the electron beam which has the physical quantity of the same level as or higher level than cold cathode in some restricted conditions. However, mostly, it has critical problems in the performance condition required for specified applications .

For example, in case of the vacuum microelectronic device which transforms the energy of the electron beam into the electromagnetic wave energy, in order to manufacture the device having a high efficiency, the electron gun capable of emitting the electron beam having the current density of 1 A/cm2, is required in the microwave band, 1000A/cm2 in the THz band. Further, in case of the carbon nanotube which is a typical material using for FEAs cold cathode, 3OnA can be obtained in the tube section having the diameter of several nanometers scale. It is very big value much more than the current density which is can be obtained in the conventional hot cathode. However, it is a value that can be obtained through one carbon nanotube. Generally, the cold cathode using the carbon nanotube uses cold cathodes consisted of multiple tubes so as to enhance the total current. In this condition, the current density rapidly decreases.

As shown in the Fowle-Nordheim relation which is the basic theory of the field emission, the voltage between the anode and the cold cathode is to be increased so as to obtain many current. However, in case the voltage is increased, it has the problem that a breakdown occurs or the electron beam current extremely changes according to the time and, in general, the lifetime of the cold cathode is seriously reduced.

Accordingly, the current or the current density of the electron beam is, in general, very small in comparison with the conventional hot cathode electron gun which can be obtained through the FEAs cold cathode electron gun emitting the stable electron beam. Therefore, although the many advantage of the miniaturization, the light weight, and the efficiency enhancement is expected, the vacuum microelectronic device which uses the cold cathode is still stayed in research.

[Disclosure] [Technical Problem] Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art. As to the present invention, the electron beam is emitted in the condition in which the FEAs cold cathode electron gun of the internal of the oscillator can steadily operate for a long time. By inducing the electron amplification phenomenon including the cold cathode for the secondary electron emission using this electron beam as the primary electron, the total current amount is amplified. Further, the klystron oscillator according to the present invention serves the structure of simultaneously controlling the current amplification of the electron beam by the secondary electron and the oscillation of a resonator.

[Technical Solution]

In order to accomplish the object, an embodiment of the present invention provides a cold cathode klystron oscillator and the oscillation method thereof. The cold cathode klystron oscillator according to the present invention comprises an electron source by a cold cathode that emits a primary electron; a first grid that focuses and accelerates an electron beam emitted in the electron source; a second grid that focuses and accelerates the electron beam passing through the first grid, and includes a resonator that converts a part of the mechanical energy of the electron beam passing through the first grid into an electromagnetic wave energy; and a secondary electron cold cathode that generates a secondary electron by colliding the electron beam passing through the second grid. Here, the focusing and the acceleration of the electron beam passing through the first grid and the second grid are made through a DC power supply. Here, it is preferable that the electron source is formed by Field Emitter Arrays (FEAs) . Here, it is preferable that the first grid and the second grid include an electromagnet or a permanent magnet for the focusing of the passing electron beam.

[Advantageous Effects] According to the present invention, the cold cathode klystron oscillator and the oscillation method can steadily emit the linear electron beam that has the high current density by adding the electron amplification phenomenon due to the second electron emission.

[Brief Description of the Drawings]

Fig. 1 is a drawing showing the structure of the conventional cold cathode electron gun. Fig. 2 is a schematic diagram showing the internal structure of a klystron oscillator including a vacuum microelectronic device and a cold cathode adhering an electron amplifying circuit according to the present invention.

Fig. 3 is a drawing showing the flowchart of the electromagnetic wave oscillation method by the klystron oscillator of Fig. 2.

Fig. 4 is a drawing showing the field emission of the primary electron and the progressing of electron beam in each section and the internal structure of an oscillator.

Fig. 5 is a drawing showing the electron beam emission by the field emission in a cold cathode for the emission of the secondary electron absorbing the primary electron and the progressing in Region 2 and Region 3 of electron beam and the internal structure of the whole oscillator according to the present invention.

Hereinafter, referring to the attached drawings, a cold cathode klystron oscillator and the oscillation method thereof according to the present invention will be illustrated in detail.

[Best Mode] Fig. 2 is a drawing showing the internal structure of a cold cathode electron gun according to the present invention.

As shown in Fig. 2, the cold cathode electron gun according to the present invention is comprised of an electron source 11 generating electrons, a first grid 20 focusing and accelerating the electron beam, a second grid 30 including a resonator 35, and a secondary electron cold cathode 40 which generates the secondary electron and amplifies the electron beam.

The generated primary electron and the secondary electron are accelerated and controlled by the voltage applied to the electron source 11, the first grid 20, the second grid 30, and the secondary electron cold cathode 40. Here, the electron source 11 is formed by laminating FEAs on the electrode substrate 10, while the electrons are emitted by a first voltage 50 which is applied between the first grid 20 and the electron source 11. Moreover, it is preferable that the electron source 11 is formed by the FEAs. The theoretical background of the field emission will be illustrated.

It was already predicted in the quantum mechanics that the cold electron performs tunneling from the flat plate metal and the semiconductor surface to a vacuum when a strong electric field is applied. This can be explained as the sum of the image potential of the electron and the potential energy by the applied electric field.

Particularly, in case the strong electric field more than 5 kV /μm is applied to the surface, the whole potential changes and the electron are capable of tunneling. However, in case of the application of the plane emitter to FED (Field Emission Display) , most metals has the problem of vacuum breakdown due to the formation of whisker in the electrical field less than 5 kV/μm. Therefore, the research of the tip structure which is acute has been processed, in which the electric field is high focused.

The current density by the electron emitted by the electric field applied to the emitter of such form is described, in general, by the Fowler-Nordheim equation. That is, it can be known that the length and permeability of electron tunneling has a close relationship with the work function of the emitter and the applied electric field.

Like this, as to the relation between the emission current and the applied electric field which is described with the Fowler-Nordheim equation, generally, the radius of curvature of the emitter, the gate hole radius, and the work function of the emitter material become smaller, while the anode current is enlarged as the gate voltage is more enlarged.

The elements except the work function which is the inherent characteristic of a material can be improved through the process development and the deformation of the architectural component. Consequently, the emitter tip of the high efficiency can be manufactured with the low work function material and the large area minute lithography technology development. Like this, as an electron source, the efficient electron source of the electron gun can become through the development of the emitter tip. It has the advantage that the efficient control is possible through the structural change of the electron gun and the variety of the DC power supply.

[Mode for Invention]

Fig. 3 is a drawing showing the flowchart of the electromagnetic wave oscillation method by the klystron oscillator according to the present invention. Hereinafter, referring to Fig. 2 and Fig. 3, the electromagnetic wave oscillation method by the klystron oscillator according to the present invention is illustrated.

The electron beam which is emitted from the electron source 11 SlOO and passes through the first grid 20 is focused and accelerated S200 by a second voltage 60 which is applied between the first grid 20 and the second grid 30 to pass through the second grid 30. The passed electron beam collides into the secondary electron cold cathode 40. A material 45 having a high yield of the secondary electron emission is laminated on the surface of the secondary electron cold cathode 40. Thus, it acts as one cold cathode to induce the emission of the secondary electron.

The electron beam amplification phenomenon that the density of the electron beam increases occurs by the emitted secondary electron and the primary electron emitted from the electron source 11 S300. That is, the secondary electron generated in Region 3 is accelerated to Region 2. However, it is hindered by the second voltage 60 having the opposite polarity to a third voltage 70 applied in Region 3, and forms again the amplified electron beam with the primary electron. A part of the kinetic energy of this electron beam is converted into the electromagnetic wave energy in the second grid 30 including the resonator 35 to oscillate the electromagnetic wave S400.

As shown in Fig. 2, the cold cathode klystron oscillator according to the present invention has the structure in which the resonator is added to the FEAs cold cathode electron gun that has an amplified structure through the secondary electron.

Region 2 and Region 3 are the characteristic of the present invention. In Fig. 2, each measurement of a structure of the present invention plays the role of controlling the electromagnetic wave oscillation including a resonator and the control of the electron amplification phenomenon. The structure of the first grid 20 and the second grid 30 including the resonator 35 is the element deciding the penetration efficiency of the electron beam. The electron beam penetration efficiency of the second grid 30 is the important element which directly affects the electron amplification phenomenon by the secondary electron and decides the amplification factor of the electron beam in the whole electron gun.

As to the grid lattice structure, various structures can be implemented, and the object of the present invention can be achieved through all grid structures in principle. Further, the second grid 30 corresponds to a part of the resonator 35, thereby, affecting the oscillation characteristic of the vacuum microelectronic device. The grid structure of the second grid also can achieve the object of the present invention through all grid structures used for the vacuum microelectronic device in principle. As shown, in Fig. 2, the second grid consists of the double grid structure. The resonator 35 including the oscillator tube is connected to both sides of a lattice. Through this structure, the structure of klystron oscillation form in which a part of the kinetic energy of the electron beam passing through the second grid 30, in particular, amplified by the secondary electron is absorbed in the resonator, and converted into the electromagnetic wave energy is implemented. Here, while the resonator has a rotation axis of symmetry, the shape of the resonator has no limit, for example, a cylindrical type or a polyhedron type, and has no limit in the number of resonator. It is preferable that all types of patterns that the electron beam can pass can be used for the first grid and the second grid, while it is a proper pattern that can serve as an oscillator and perform the function of the focusing and acceleration of the electron beam.

Further, the second grid 30 including the resonator 35 serves as an electrode, and the resonator has an electrode structure protruded from the lattice of the second grid. This structure has two kinds of function. One function is that, in Region 2 and Region 3, the electron beam is appropriately focused such that the electron amplification phenomenon by the secondary electron emission is smoothly performed. Additionally, the physical characteristic is controlled in order that the electron beam that oscillates the resonator has the condition that is suitable for the oscillating condition.

In Fig. 2, one-side of the secondary electron cold cathode is the cold cathode emitting the secondary electron. In general, as the material having a great maximum secondary electron emission coefficient δmax is used, the electron amplification phenomenon greatly occurs. However, an optimum secondary electron emission coefficient δop can be changed in consideration of each measurement, voltage and the repulsive power by Screening Effect or the space charge of the oscillator structure. Here, the principle of the generation of the secondary electron is that the energy of an incident electron (primary electron) irradiated on the surface of a sample interacts with the electron in the orbit of the atom forming the sample to delivers the energy to the orbital electron, while the orbital electron is emitted to the outside. That is, it is generated due to the inelastic scattering between the incident electron beam and the sample. The amount of the emitted secondary electron is different according to the degree of curvature of the surface of the sample. Additionally, it has the information of a shape of two measurement of the surface.

Therefore, it is preferable that the cold cathode for the emission of the secondary electron is one of MgO, GaP, GaAs, MgF2, CaF2, LiF, A12O3, ZnO, CaO, SrO, Si02 and La2O3 which have a high emission coefficient. In addition, it can be manufactured by laminating various materials on various substrates such as Si wafer in which a metal or an electrode is formed. As shown in Fig. 2, as to the klystron oscillator according to the present invention, at least, three voltage set up is required. The second voltage V2 60 and the third voltage V3 70 are the voltage applied to Region 2 and Region 3 respectively. The second voltage V2 60 continuously accelerates the electron beam which is accelerated by the first voltage Vl 50 to the same direction. The third voltage V3 70 decelerates the electron beam.

The first voltage Vl 50 is the voltage deciding the final energy that the electron gets in Region 1. When entering into Region 2, the electron has the energy of eVl.

Like this, it is preferable that DC power supply is used for the power source which is applied in order to control the electron beam. In case of the AC power supply, there can be a disadvantage that the configuration of a circuit is complicated and only the pulse type electron beam can be formed. In case of using the DC power supply, there can be an advantage that the configuration of circuit is simple, the control is facilitated, and that both of the pulse type and the successive type electron beam can be selectively formed. In case the yield of the secondary electron by the primary electron is a maximum when the electron is absorbed into the secondary electron material with eVδmax, the relation among Vl 50, V2 60, V3 70 for maximizing the secondary electron emission in the cold cathode 45 satisfies equation Vδmax = Vl + V2 - V3. Further, it is preferable that V2 60 is always greater than V3 70.

Hereinafter, Figs. 4 and 5 will illustrate the configuration and principles of the present invention through the conceptual diagram showing the generation of the primary electron and the secondary electron and the progressing in Region 1 - 3. Fig. 4 is a drawing showing the field emission of the primary electron, the progressing in each Region of electron beam and the internal structure of the oscillator. In Region 2, after the primary electron beam generated in the FEAs cold cathode electron source of an oscillator is continuously accelerated, it is decelerated in Region 3. A part 90 of the primary electron beam collides with the secondary electron emission material, and being absorbed to emit the secondary electron. Here, the energy that the primary electron beam absorbed into the second electron emission material has is eVl + V2 - V3 and this value is approximately eVδmax. The structure of each flat board including the first grid 20 and the second grid 30 is set up so that the electron beam might be absorbed into the secondary electron material while maintaining the state where the electron beam is appropriately focused. Additionally, it is preferable that the electromagnet or the permanent magnet for smoothening the focusing of the linear electron beam is further included. There can be an advantage that it can play much role in the uniform focusing and the control for steering as it is positioned in the side or in a proper location of an oscillator (not shown).

Fig. 5 is a drawing showing the progressing of the electron beam emission by the field emission in the cold cathode for the secondary electron emission absorbing the primary electron and the electron beam in Region 2 and Region 3, and the internal structure of the whole oscillator according to the present invention.

In Region 3, the secondary electron 95 generated in the position of the secondary electron cold cathode 40 is accelerated by the voltage V3 70 in Region 3 to enter Region 2. In Region 2, it is decelerated by V2 60. After stopping in Region 2, it changes the progressive direction, and enters again Region 3. Always, V2 is greater than V3. At this time, each measurement value of the internal structure of the electron gun, especially, the structure of the flat board including the first grid 20 and the second grid 30 has to be set up in order to appropriately focus the electron beam. All geometry structures including Vl, V2, V3 value and the current value of the electron beam have an effect. The electron beam passes through the second grid 30 including the resonator 35 before entering Region 3 from Region 2. In case a proper condition is satisfied, the kinetic energy of the electron beam is transformed to the electro magnetic wave 37 energy to oscillate the resonator. This oscillation process is like the oscillation principles of the conventional reflex klystron. That is, a part of the mechanical energy of the electron beam which is reflected in Region 2 and passes again the resonator is converted into the electro magnetic wave 37 energy. As shown in Fig. 4, the structure of the site which connects the resonator 35 to the external load is omitted, while some electro magnetic wave 37 is generated in the resonator and is connected to the external load(not shown) . Additionally, the electron beam passing through the second grid 30 is decelerate again in Region 3, and nearly loses all kinetic energies around the secondary electron cold cathode 40. In detail, when some electronics reached the surface of the secondary electron cold cathode, they have the kinetic energy more than 0. Other electronics do not have enough kinetic energy when entering in Region 3 such that they are unable to reach the secondary electron cold cathode 40. The deviation of the energy distribution as described above is much more enlarged than in the energy distribution of the initial secondary electron generated in the secondary electron cold cathode 40. It is determined by various factors including screening effect, the spreading by the space-charge force, the focusing by each electrode 20, 30, 40, and the energy exchange with the resonator 35.

Like this, the secondary electron which is absorbed again into some secondary electron emission material due to the increasing of the deviation of the energy distribution can have the energy which can produce other secondary electrons much enough. Like this, some secondary electrons can become the primary electron producing a new secondary electron. In principle, this chain reaction is boundlessly repeated to continuously increase the number of electron within Region 2 and Region. After all, it converges to a fixed value according to the condition of the given circuit.

All electrons that enter again the second grid 30 after passing through Region 3 and the second grid 30 and entering Region 2 have the possibility to contribute to the oscillation of a resonator. However, in case of the reflex klystron which is an example of the vacuum microelectronic device presented in the present invention, the electron beam supplied through Region 1 nearly does not have an effect on the oscillation of a resonator. These electrons only act on the secondary electron cold cathode 40 as a primary electron.

The number of secondary electron generated by a proper condition is bigger than the number of primary electrons over several times ~ several tens times, between Region 2, Region 3 and the second grid 30, thereby, the screening effect or the phenomenon by space charge force is dominantly affected by the secondary electron.

As to the electro magnetic energy transformed from the electron beam, while some are accumulated in the resonator, some can be disappeared in the resonator and some can be used up in the velocity modulation of the electron beam and some can be delivered to the external load. In this way, the structure for connecting the resonator to the external load is identical with the structure of the resonator 35 shown in Fig. 3. As to this structure, all general modes that are used for the resonator of the vacuum microelectronic device can be used.

In addition, as another embodiment of the present invention, in case different electron guns using the structure of Fig. 2 as a basic structure are parallely connected, the amplified Multi-Electron Beam is formed, therefrom, an electromagnetic wave oscillating device can be made. In this way, the parallely connected multiple klystron oscillator is identical with an example of the present invention shown in Fig. 2. Various beam is formed with the measurement setting of each structure and the change of the power source, thereby, electromagnetic waves of various frequency can oscillate (not shown) . That is, the multiple electromagnetic wave oscillation method of high efficiency capable of oscillating the various electromagnetic waves by generating multi-electron beam having a various characteristic is provided and a cold cathode multiple klystron oscillator can be provided by using the method.

It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents .

[industrial Applicability]

In case the klystron oscillator of the present invention and the oscillation method thereof are provided, the cold cathode electron gun as one element of the oscillator can stably emit the linear electron beam having the current density higher than the conventional cold cathode electron gun as much as several tens ~ several hundreds times by adding the electronic amplification phenomenon due to the secondary electron to the conventional cold cathode electron gun. Further, in case the electronic amplifier circuit that the present invention provides is used, the current density in the FEAs cold cathode which provides the primary electron becomes low and the current density of the final electron beam can be enhanced. Accordingly, it has the effect that the time when the cold cathode vacuum microelectronic device stably operates is extended.

In this way, the frequency band capable of outputting or oscillating can be enhanced by using the amplified secondary electron in the oscillation of the vacuum microelectronic device. Additionally, the resonator performs, at the same time, the role of the circuit of the electrode and the vacuum microelectronic device comprising the electron gun. Accordingly, the number of electrode necessary for the whole circuit composition is minimized, and the size of a device is minimized. Additionally, the whole efficiency of a device is increased by minimizing the movement route of the electron beam to reduce the loss of the electron beam.

Claims

[The Scope of Claim] [Claim l]

A cold cathode klystron oscillator comprising: an electron source by a cold cathode that emits a primary electron; a first grid that focuses and accelerates an electron beam emitted in the electron source; a second grid that focuses and accelerates the electron beam passing through the first grid, and includes a resonator that converts a part of the mechanical energy of the electron beam passing through the first grid into an electromagnetic wave energy; and a secondary electron cold cathode that generates a secondary electron by colliding the electron beam passing through the second grid, wherein the focusing and the acceleration of the electron beam passing through the first grid and the second grid are made through a DC power supply.

[Claim 2]

The cold cathode klystron oscillator of claim 1, wherein the electron source is formed by Field Emitter Arrays (FEAs) .

[Claim 3 ]

The cold cathode klystron oscillator of claim 1, wherein the DC power supply applies a first voltage between the electron source and the first grid; a second voltage between the first grid and the second grid; and a third voltage between the second grid and the secondary electron cold cathode.

[Claim 4] The cold cathode klystron oscillator of claim 3 , wherein the polarity of the third voltage is opposite to the polarity of the second voltage; and the magnitude of the third voltage is smaller than the magnitude of the second voltage.

[Claim 5]

The cold cathode klystron oscillator of claim 1, wherein one of MgO, GaP, GaAs, MgF2, CaF2, LiF, A12O3, ZnO,

CaO, SrO, Si02 and La2O3 forms a layer in the region in which the primary electron collides with the secondary electron cold cathode.

[Claim 6] The cold cathode klystron oscillator of claim 1, wherein the first grid and the second grid include an electromagnet or a permanent magnet for the focusing of the passing electron beam.

[Claim 7]

A multiple cold cathode klystron oscillator that further connects the structure of the cold cathode klystron oscillator of claim 1 parallely at least one or more.

[Claim 8]

A method for oscillating an electromagnetic wave through an electron beam, the method comprising: emitting a primary electron by a cold cathode electron source; focusing and accelerating the electron beam of the emitted primary electron by the first grid and the second grid; amplifying the electron beam passing through the second grid by colliding the electron beam that passed through the second grid with the secondary electron cold cathode to generate the secondary electron; and oscillating the electromagnetic wave by converting a part of the mechanical energy of the amplified electron beam into an electromagnetic wave energy by a resonator included in the second grid.

[Claim 9] A method for multiple electromagnetic wave oscillation that further connects the structure using the method for oscillating an electromagnetic wave of claim 8 parallely at least two or more.