JPH07226179A - Electron gun - Google Patents

Abstract

PURPOSE:To take out a highly intense electron beam or X-ray beam in a small cross-sectional area by outputting a secondary electron emitted from a negative electrode outside from an electron beam taking-out window as an electron beam. CONSTITUTION:In the case where an electron gun is actuated, when pulse voltage is impressed on a positive electrode wire 20, discharge is caused in an ionization chamber 10, and plasma is generated in the ionization chamber 10. A negative electrode 40 and a grid-shaped negative electrode 50 housed in a high voltage chamber 60 pull out ions from this plasma through an extraction grid 30. The ions are accelerated toward the negative electrode 40 by passing through the extraction grid 30 and the grid-shaped negative electrode 50. Here, the accelerated ions collide with the negative electrode 40, and a secondary elecrtron emitted from a surface of the negative electrode 40 passes through a cavity surrounded by the ionization chamber 10 along the electric potential distribution between the negative electrode 40 and the grid-shaped negative electrode 50. This secondary electron is accelerated toward an electron beam taking-out window 70, and is outputted as an electron beam from the window 70 without passing through the ionization chamber 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun which uses plasma to generate an electron beam.

[0002]

2. Description of the Related Art In recent years, high-intensity electron beams have been used in the field of many advanced materials such as flue gas treatment, chemical reaction, processing, welding, laser gas excitation, and X-ray equipment. Guns are used. The conventional electron gun will be described below.

As shown in FIG. 10, an extraction grid 3 is arranged in an ionization chamber 2 containing an anode wire 1 for ionizing the introduced gas, and a high voltage chamber communicating with the ionization chamber 2 through the extraction grid 3. 4 are provided. An electron beam extraction window 5 which is transparent to electrons is formed on the surface of the ionization chamber 2 facing the extraction grid 3.
A cathode 6 facing the extraction grid 3 is housed in the high voltage chamber 4, and the cathode 6 is connected to a high voltage introducing terminal 7 and is drawn out of the high voltage chamber 4. An exhaust port (not shown) is formed in the high voltage chamber 4, and the pressure in the ionization chamber 2 and the high voltage chamber 4 is controlled by the exhaust device through the exhaust port. Usually, in order to efficiently carry out positive ionization of the introduced gas, the pressures of the ionization chamber 2 and the high voltage chamber 4 are kept as low as 10 to 30 mTorr. Helium, which has a good ion bombardment secondary electron emission ratio at the cathode 6, is used as the gas. The cases of the ionization chamber 2 and the high voltage chamber 4 are grounded, and the extraction grid 3 is in the same voltage state as the electron beam extraction window 5. The cathode 6 is connected to a high voltage supply source (not shown) via a high voltage introduction terminal 7 and is maintained at a negative bias voltage as high as -150 kV. On the other hand, the electron beam extraction window 5 is made of a sheet of aluminum or polymer having a thickness of about 10 μm, which is transparent to high-energy electrons. The window width changes depending on the application of the electron gun.

When operating the electron gun, a pulse voltage or a DC voltage of about 3 kV is applied to the anode wire 1.
When a voltage is applied, a discharge occurs between the anode wire 1 and the case of the ionization chamber 2 at ground potential, and plasma is generated in the ionization chamber 2. On the other hand, the cathode 6 housed in the high voltage chamber 4 extracts ions from this plasma through the extraction grid 3. This ion is generated in the ionization chamber 2
Through the extraction grid 3 disposed between the high voltage chamber 4 and the high voltage chamber 4, the high voltage chamber 4 is accelerated to high energy and collides with the cathode 6. When the ions collide with the cathode 6, secondary electrons are emitted from the surface of the cathode 6. The secondary electrons thus emitted travel in the direction opposite to the ions, are accelerated toward the extraction grid 3, and further pass through the ionization chamber 2 to reach the electron beam extraction window 5, where high-energy electrons are emitted. It is output as a beam. Here, ignoring the initial energy in the vicinity of the extraction grid 3, and assuming that the negative bias voltage is V _ht and the charge amount of the ions is e, it is kept in mind that they are related to a single charged ion. It is considered that the cathode 6 is reached with energy equal to e · V _ht . The secondary electrons emitted by the ions extracted from the extraction grid 3 colliding with the cathode 6 are accelerated toward the extraction grid 3 and reach the energy of e · V _ht . In these states, one ion,
The electrons emitted by these ions have substantially overlapping orbits corresponding to the same electric field line.

The electron gun as described above is an electron gun for flue gas treatment, chemical reaction, processing, welding, and laser gas excitation, and by replacing the electron beam extraction window 5 with a target for X-ray generation, X-ray generation is performed. It is applicable to a device.

By the way, in the conventional electron gun, high-energy electrons emitted from the cathode 6 pass through the ionization chamber 2 in which plasma exists, so that the interaction between electrons and plasma causes energy monochromaticity and divergence angle of the electron beam. Was out of control and bad. Therefore, conventionally, as a countermeasure against this, the voltage applied to the anode wire 1 is decreased to reduce the plasma density in the ionization chamber 2. However, when the plasma density in the ionization chamber 2 is reduced, the number of ions extracted into the high voltage chamber 4 decreases, and it is difficult to improve the obtained electron beam intensity.

In the conventional electron gun, the trajectory of high-energy electrons emitted from the cathode 6 is affected by the potential distribution due to the shape of the cathode 6. In this case, the potential distribution in the vicinity of the cathode 6 is shown in FIG.
As shown in, the electron orbit goes in the direction of large divergence. Since the divergence of the electron beam becomes large, it is very difficult to take out the electron beam having the necessary cross-sectional area. Further, when the electron beam is converged by using an electron lens, the convergence ability is limited due to the large divergence angle. On the other hand, an aperture 8 having the same cross-sectional area as the beam cross-sectional area required conventionally is disposed between the ionization chamber 2 and the electron beam extraction window 5, and the cross-sectional area of the electron beam is mechanically deleted. The method of doing was taken. However, when the cross-sectional area of the electron beam is mechanically deleted by the aperture 8, there is a problem that the intensity of the electron beam obtained is reduced by the amount of the deletion and the efficiency of the apparatus is reduced. Further, there have been simultaneously problems of abnormal overheating of the aperture 8 due to mechanical removal, size increase of the device due to mounting of a cooling device corresponding thereto, and complication.

[0008]

As described above, in the conventional electron gun, the electrons emitted from the cathode cannot reach the electron beam extraction window unless they pass through the plasma. Therefore, there is a problem that it is difficult to improve the intensity of the electron beam,
Further, there is a problem that the generated electron beam is largely diverged by the cathode having a large occupation ratio of the horizontal plane, and it is very difficult to take out the electron beam having a required cross-sectional area and intensity.

Therefore, an object of the present invention is to provide an electron gun which can extract a high-intensity electron beam or X-ray beam with a small cross-sectional area.

[0010]

In order to solve the above-mentioned problems, the present invention is, first, that the outer shape is formed in a ring shape and the introduced gas is ionized by the anode to generate plasma, and the inner peripheral wall is formed. An ionization chamber provided with an extraction grid for extracting ions from the plasma, and a secondary electron in a direction substantially orthogonal to the extraction direction of the ions due to collision of the ions extracted from the ionization chamber with an ion collision surface formed in a conical shape. Emitting a cathode, a grid-shaped cathode disposed between the cathode and the extraction grid and held at the same potential as the cathode, and outputting secondary electrons emitted from the cathode to the outside as an electron beam. The gist is to have an electron beam extraction window.

Secondly, a separation type ionization is provided in which the gas formed by being separated into two parts is ionized at the anode to generate a plasma, and an extraction grid for extracting ions from the plasma in the same direction is provided. The secondary electron is emitted to pass between the chamber and the ionization chamber separated into the two by collision of the ion extracted from the ionization chamber with the ion collision surface formed on the inner peripheral surface of the cylinder. The gist is to have a cathode and an electron beam extraction window for outputting secondary electrons emitted from the cathode as an electron beam to the outside.

Thirdly, an outer shape is formed in an annular shape and the introduced gas is ionized by the anode to generate plasma, and an end face is provided with an extraction grid for extracting ions from the plasma in a direction parallel to the annular center line. And a cathode that emits secondary electrons so as to pass through the central space of the annular ionization chamber due to the collision of ions extracted from the ionization chamber, the ion collision surface being formed into a bowl-shaped concave curved surface. And an electron beam extraction window for outputting secondary electrons emitted from the cathode as an electron beam to the outside.

Fourthly, an ionization chamber provided with an extraction grid for ionizing the introduced gas at the anode to generate plasma and extracting ions from the plasma, and an ion collision surface formed in a flat surface from the ionization chamber A cathode that emits secondary electrons in a direction of passing through the ionization chamber due to collision of the extracted ions, and an ion collision surface that is arranged so as to surround the ion collision surface of the cathode and is held at the same potential as the cathode. A torus converging means for converging the emitted secondary electrons by causing distortion of the potential distribution above, and an electron beam extraction window for outputting the secondary electrons converged by the converging means to the outside as an electron beam. Having it is the gist.

Fifth, in any one of the first to fourth configurations, the gist is that a magnetic field lens for converging the electron beam is arranged in front of the electron beam extraction window.

Sixth, in any one of the first to fifth configurations, the gist is that a metal foil target for generating an X-ray beam by the secondary electrons is attached to the electron beam extraction window.

[0016]

In the above structure, firstly, the ions extracted from the annular ionization chamber through the extraction grid and the lattice-shaped cathode collide with the conical cathode. The trajectories of secondary electrons emitted from the cathode due to the collision of the ions are determined by the potential distribution between the cathode and the lattice-shaped cathode, which is controlled by the inclination angle of the cathode surface with respect to the central axis. Then, the secondary electrons pass through the cavity in the center of the annular ionization chamber. Then, the secondary electrons that have passed through the cavity are output to the outside as an electron beam from the electron beam extraction window. Therefore, the secondary electrons are output to the outside as an electron beam without passing through the ionization chamber where plasma exists, and the electron beam intensity is improved.

Secondly, the ions extracted from the two separated ionization chambers in the same direction through the extraction grids collide with the cathode. Secondary electrons emitted from the cathode due to the collision of the ions pass between the two ionization chambers along the line of electric force formed by the curved surface of the inner peripheral surface of the cylinder of the cathode, and the electron beam is extracted from the electron beam extraction window. Is output as. Therefore, the electron beam can be taken out without the secondary electrons passing through the ionization chamber where the plasma exists.

Thirdly, the ions extracted from the annular ionization chamber through the extraction grid in the direction parallel to the annular center line collide with the cathode. The secondary electrons emitted from the cathode due to the collision of the ions pass through the central space of the annular ionization chamber along the lines of electric force formed by the bowl-shaped concave curved surface of the cathode, and as an electron beam from the electron beam extraction window. Is output. Therefore, the secondary electrons emitted from the cathode do not pass through the ionization chamber where the plasma exists, and the beam profile is circular, so that the intensity of the output electron beam is further improved.

Fourth, the ions extracted from the ionization chamber through the extraction grid strike the cathode. The secondary electrons emitted from the cathode due to the collision of the ions have a converging orbit toward the ionization chamber and the electron beam extraction window due to the distortion of the potential distribution by the torus-shaped converging means on the cathode surface. This convergence rate is controlled by the torus diameter of the converging means. Due to the convergent orbit, the cross-sectional area of the electron beam near the electron beam extraction window becomes much smaller than the cross-sectional area near the cathode surface, and at the same time the divergence of the electron beam also disappears. Therefore, it is possible to obtain a high-intensity electron beam with a small cross-sectional area without mechanical reduction.

Fifth, by arranging a magnetic field lens in front of the electron beam extraction window, it is possible to control the output electron beam trajectory and further focus the electron beam, thereby further increasing the electron beam intensity. It is possible to improve.

Sixth, it is possible to extract a high-intensity X-ray beam by attaching a metal foil target which generates an X-ray beam by secondary electrons to the electron beam extraction window.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are views showing a first embodiment of the present invention. First, the structure of the electron gun will be described. An annular ionization chamber 10 accommodating an anode wire 20 for ionizing the introduced gas is disposed, and an extraction grid 30 is disposed on the inner peripheral wall of the ionization chamber 10. There is. The cathode 40 arranged via the extraction grid 30 is formed into a conical surface, and a grid-shaped cathode 50 to which a negative bias of the same potential as the cathode 40 is applied is provided between the extraction grid 30 and the cathode 40. It is arranged around the cathode 40. Cathode 40
The grid-shaped cathode 50 is connected to the high-voltage introduction terminal 90 and is drawn out of the high-voltage chamber 60. An electron beam extraction window 70, which is transparent to electrons, is formed above the high voltage chamber 60. The cases of the ionization chamber 10 and the high voltage chamber 60 are grounded, and the cathode 40 is connected to the cathode 40 via a high voltage introduction terminal 90 by a high voltage supply source (not shown).
A high negative bias voltage of about 150 kV is applied.

Next, referring to FIG. 2, the operation of the present embodiment configured as described above will be described. When operating the electron gun, a pulse voltage or DC voltage of about 3 kV is applied to the anode wire 20. When a voltage is applied, electric discharge occurs in the ionization chamber 10 and plasma is generated in the ionization chamber 10. On the other hand, the cathode 4 housed in the high voltage chamber 60
0 and the grid cathode 50 extract ions from this plasma through the extraction grid 30. The ions are accelerated toward the cathode 40 through the extraction grid 30 and the lattice-shaped cathode 50, and the ions accelerated to high energy collide with the cathode 40. The secondary electrons emitted from the surface of the cathode 40 by the collision of the ions pass through the cavity surrounded by the ionization chamber 10 along the potential distribution between the cathode 40 and the lattice-shaped cathode 50 as shown in FIG. The potential distribution in this case is controlled by the inclination angle of the surface of the cathode 40 with respect to the central axis. The secondary electrons that have passed through the cavity are accelerated toward the electron beam extraction window 70 and output as an electron beam from the electron beam extraction window 70.

According to this embodiment, the electron beam is output without passing through the ionization chamber 10 in which the plasma exists, so that it is not necessary to control the voltage applied to the anode wire 20 to be low, and the intensity of the electron beam is improved. Can be made.
Further, since the interaction between electrons and plasma is eliminated, an electron beam that is energetically monochromatic can be obtained. Further, by changing the inclination angle of the surface of the cathode 40 with respect to the central axis to change the potential distribution, it is possible to control the trajectory of the electron beam from a parallel beam to a convergent beam.

In FIG. 3, a magnetic field lens 80 for controlling the electron beam trajectory is arranged between the high voltage chamber 60 and the electron beam extraction window 70 in the first embodiment. The magnetic field lens 80 introduces a magnetic field from an external magnetic field generator (not shown) to converge the electron beam diameter. Therefore, if the magnetic lens 80 is used, the electron beam intensity can be further increased. In FIG. 3, 91 is a supporting insulator. Further, in this embodiment, a metal foil target capable of generating X-rays by secondary electrons is attached instead of the electron beam extraction window 70 shown in FIGS. It is also applicable to devices.

FIG. 4 shows a second embodiment of the present invention. As shown in the figure, in this embodiment, the ionization chambers 11 and 12 are formed separately. Anode wires 21 and 22 are housed in the ionization chambers 11 and 12, respectively, and extraction grids 31 and 32 are arranged. A cathode 41 is housed in a high voltage chamber 60 that communicates with the ionization chambers 11 and 12 via the extraction grids 31 and 32.
Is formed into a curved surface having an inner peripheral surface of a cylinder. Cathode 41
Is connected to the high voltage introduction terminal 90 and is drawn out of the high voltage chamber 60. An electron beam extraction window 71, which is transparent to electrons, is formed above the ionization chambers 11 and 12 facing the high voltage chamber 60.

Next, the operation of this embodiment configured as described above will be described. When operating the electron gun, a pulse voltage or a DC voltage of about 3 kV is applied to each of the anode wires 21 and 22. When a voltage is applied, electric discharge occurs in the ionization chambers 11 and 12, and plasma is generated in the ionization chambers 11 and 12. On the other hand, the cathode 41 housed in the high voltage chamber 60 extracts ions from this plasma through the extraction grids 31 and 32. The ions enter the high voltage chamber 60 through the extraction grids 31, 32 arranged between the ionization chambers 11 and 12 and the high voltage chamber 60,
The ions accelerated toward the cathode 41 and accelerated to high energy collide with the cathode 41. The secondary electrons emitted from the surface of the cathode 41 due to the collision of the ions pass between the two ionization chambers 11 and 12 along the line of electric force formed by the cathode 41 having a cylindrical inner peripheral surface curved surface, The electron beam is accelerated toward the electron beam extraction window 71, and is output as an electron beam from the electron beam extraction window 71.

According to this embodiment, as in the first embodiment, the electron beam is used in the ionization chamber 11, where the plasma exists.
Since it is output without passing through 12, the anode wires 21, 2
It is not necessary to control the voltage applied to 2 to be low, and the intensity of the electron beam can be improved. Further, since the interaction between electrons and plasma is eliminated, an electron beam that is energetically monochromatic can be obtained. Here, assuming that the incident angle of the ions with respect to the cathode 41 is θ, the amount of secondary electrons emitted by the collision of the ions is proportional to 1 / cos θ, so that compared with the conventional electron gun in which the incident angle is zero. Even if the applied voltage is the same, the intensity of the electron beam can be increased.

FIG. 5 shows a third embodiment of the present invention. As shown in the figure, the extraction grid 3 is provided on the lower end surface of the annular ionization chamber 13 containing the anode wire 23 for ionizing gas.
3 is provided, and the ionization chamber 1 is connected via the extraction grid 33.
A high voltage chamber 60 that communicates with the vehicle 3 is provided. The high-voltage chamber 60 accommodates the cathode 42 having a bowl-shaped concave curved surface. At the upper part of the ionization chamber 13 facing the high voltage chamber 60, an electron beam extraction window 72 having electron transparency is provided.
Are formed.

Next, the operation of this embodiment configured as described above will be described. The ions derived from the plasma generated in the ionization chamber 13 are extracted by the cathode 42, pass through the extraction grid 33 and enter the high voltage chamber 60, and enter the cathode 42.
The ions that are accelerated toward and collide with the high energy collide with the cathode 42. This collision of ions causes the cathode 4
The secondary electrons emitted from the surface of No. 2 pass through the center of the annular ionization chamber 13 along the line of electric force formed by the bowl-shaped cathode 42, and are accelerated toward the electron beam extraction window 72 to accelerate the electron beam. Is output as.

According to this embodiment, the same effect as the second embodiment can be obtained, and since the cathode 42 is formed in a bowl shape having a concave curved surface, the electron beam profile becomes circular and the electron beam profile is further increased. The strength of can be improved.

In FIG. 6, as in the case of FIG. 3, a magnetic field lens 81 is arranged between the ionization chamber 13 and the electron beam extraction window 72 in the third embodiment.
The operation is the same as in the case of FIG. In any of FIGS. 4, 5 and 6, the electron gun of each embodiment can be applied to the X-ray apparatus by attaching an X-ray generating metal foil target instead of the electron beam extraction window. Is.

7 and 8 show a fourth embodiment of the present invention. As shown in FIG. 7, an extraction grid 34 is disposed on the lower surface of the ionization chamber 14 accommodating the anode wire 24 for ionizing the introduced gas, and a high voltage chamber 60 communicating with the ionization chamber 14 via the extraction grid 34. Is provided. A cathode 43 having a flat ion collision surface is housed in the high-voltage chamber 60, and a torus-shaped converging means 44 that is held at the same potential as the cathode 43 is attached on the horizontal surface of the cathode 43. The cathode 43 and the converging means 44 are connected to the high voltage introduction terminal 7 and are drawn out of the high voltage chamber 60. An electron beam extraction window 73 that is transparent to electrons is formed above the ionization chamber 14 facing the high voltage chamber 60.

Next, the operation of the present embodiment configured as described above will be described. When operating the electron gun, a pulse voltage or a DC voltage of about 3 kV is applied to the anode wire 24. When a voltage is applied, a discharge occurs in the ionization chamber 14 and plasma is generated in the ionization chamber 14. On the other hand, the cathode 43 and the toroidal converging means 44 housed in the high voltage chamber 60 extract ions from this plasma through the extraction grid 34. This ion is the extraction grid 3
4 enters the high voltage chamber 60 and is accelerated toward the cathode 43, and the ions accelerated to high energy are
Clash with. The secondary electrons emitted from the surface of the cathode 43 due to the collision of the ions take a converging orbit along the potential distribution near the cathode 43 distorted by the torus-shaped converging means 44 as shown in FIG. After passing through 14, the electron beam is accelerated toward the electron beam extraction window 73 and is output as an electron beam from the electron beam extraction window 73.

According to this embodiment, the secondary electrons emitted from the cathode enter the extraction grid 34, the ionization chamber 14 and the electron beam extraction window 73 due to the distortion of the potential distribution due to the torus-shaped converging means 44 on the surface of the cathode 43. Has a convergent orbit. Due to this convergent trajectory, the cross-sectional area of the electron beam near the electron beam extraction window 73 becomes much smaller than the cross-sectional area of the electron beam near the surface of the cathode 43, and at the same time, the divergence of the electron beam disappears. Therefore, a high-intensity electron beam with a small cross-sectional area can be obtained without mechanical reduction. Moreover, since it is not necessary to mechanically reduce the required electron beam cross-sectional area, the efficiency of the entire apparatus is increased. Then, by changing the diameter of the cross section of the torus in the converging means 44, the cross-sectional area of the electron beam can be changed as necessary while maintaining the strength. When a higher focusing rate is required for the electron beam focusing by the torus focusing means 44, a magnetic field lens 82 is provided between the high voltage chamber 60 and the electron beam extraction window 73 as shown in FIG. To do. The magnetic field lens 82 introduces a magnetic field from an external magnetic field generator (not shown) to converge the electron beam diameter. Therefore, if the magnetic field lens 82 is used, the convergence rate can be further increased while maintaining the electron beam intensity. Further, in the present embodiment as well, it is applicable to an X-ray generator by attaching a metal foil target capable of generating X-rays instead of the electron beam extraction window 73 shown in FIGS.

[0037]

As described above, according to the present invention,
First, the ionization chamber for generating plasma has an annular outer shape, and an extraction grid for extracting ions from the plasma is provided on the inner peripheral wall of the ionization chamber. The cathode has a conical surface for ion collision and is extracted from the ionization chamber. Secondary electrons are emitted between the cathode and the extraction grid by causing secondary electrons to be emitted in a direction substantially orthogonal to the extraction direction of the ions by the collision of the ions, and the secondary cathode is held at the same potential as the cathode. Does not pass through the ionization chamber where plasma exists, but passes through the cavity in the center of the ionization chamber and is output as an electron beam from the electron beam extraction window, so that the intensity of the electron beam can be improved.

Secondly, the ionization chamber for generating plasma is provided with an extraction grid which is separated into two and draws out ions from the plasma in the same direction, and the cathode has an ion collision surface formed on a curved surface of an inner peripheral surface of a cylinder. Since the secondary electrons are emitted in a direction of passing between the two ionization chambers separated by the collision of the ions extracted from the ionization chamber,
The secondary electron can output the electron beam without passing through the ionization chamber where the plasma exists, and the intensity of the electron beam can be improved.

Thirdly, the ionization chamber for generating plasma is formed in an annular shape, the end face is provided with an extraction grid for extracting ions from the plasma in a direction parallel to the annular center line, and the cathode has a bowl-shaped concave curved surface on the ion collision surface. The secondary electrons discharged from the cathode do not pass through the ionization chamber in which plasma is present because the secondary electrons are formed so as to pass through the central space of the annular ionization chamber due to the collision of ions.
Moreover, since the beam profile is circular, the intensity of the output electron beam can be further improved.

Fourthly, the cathode has a flat ion collision surface and emits secondary electrons in the direction of passing through the ionization chamber due to the collision of the ions extracted from the ionization chamber. Since a torus-shaped converging means for converging the emitted secondary electrons by generating a distortion of the potential distribution on the ion collision surface by being held at the electric potential is provided, the converging action of the converging means causes the electron beam near the electron beam extraction window. The cross-sectional area is much smaller than the cross-sectional area near the cathode surface, and at the same time, there is no divergence of the electron beam, and a high-intensity electron beam can be obtained with a small cross-sectional area without mechanical reduction.

Fifth, since a magnetic field lens is provided in front of the electron beam extraction window, the output electron beam trajectory can be controlled and the electron beam can be further converged to further improve the electron beam intensity. You can

Sixth, since a metal foil target for generating an X-ray beam by secondary electrons is attached to the electron beam extraction window, a high intensity X-ray beam can be extracted.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an electron gun according to the present invention with a part cut away.

FIG. 2 is a diagram for explaining the operation of the first embodiment.

FIG. 3 is a diagram showing a configuration example in which a magnetic lens is attached to the first embodiment.

FIG. 4 is a configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram showing a third embodiment of the present invention with a part cut away.

FIG. 6 is a diagram showing a configuration example in which a magnetic lens is attached to the third embodiment.

FIG. 7 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 8 is a diagram for explaining the operation of the fourth embodiment.

FIG. 9 is a diagram showing a configuration example in which a magnetic lens is attached to the fourth embodiment.

FIG. 10 is a configuration diagram of a conventional electron gun.

FIG. 11 is a diagram for explaining the operation of the conventional example.

[Explanation of symbols]

 10, 11, 12, 13, 14 Ionization chamber 20, 21, 22, 23, 24 Anode wire 30, 31, 32, 33, 34 Extraction grid 40, 41, 42, 43 Cathode 44 Focusing means 50 Lattice cathode 60 High Voltage chamber 70, 71, 72, 73 Electron beam extraction window 80, 81, 82 Magnetic field lens

Claims (6)

[Claims] 1. An ionization chamber provided with an extraction grid for extracting ions from the plasma is formed on the inner peripheral wall of the inner peripheral wall of which an outer shape is formed into a ring to ionize the introduced gas to generate plasma, and an ion collision surface is formed. A cathode that is formed in a conical surface and that emits secondary electrons in a direction substantially orthogonal to the extraction direction of the ions due to collision of the ions extracted from the ionization chamber, and is disposed between the cathode and the extraction grid. A grid cathode held at the same potential as the cathode,
An electron gun having an electron beam extraction window for outputting secondary electrons emitted from the cathode as an electron beam to the outside. 2. A separation type ionization chamber provided with an extraction grid for ionizing the gas, which is separately formed into two and introduced respectively, with an anode to generate plasma and extracting ions from the plasma in the same direction. A cathode for emitting secondary electrons so that an ion collision surface is formed on a curved surface of an inner peripheral surface of a cylinder and is passed between the two ionization chambers separated by the collision of ions extracted from the ionization chamber; And an electron beam extraction window for outputting secondary electrons emitted from the cathode as an electron beam to the outside. 3. An outer shape is formed in an annular shape to ionize the introduced gas with an anode to generate plasma, and an end face is provided with an extraction grid for extracting ions from the plasma in a direction parallel to the annular center line. An ionization chamber,
A cathode that emits secondary electrons so that the ion collision surface is formed into a bowl-shaped concave curved surface and passes through the central space portion of the annular ionization chamber due to the collision of ions extracted from the ionization chamber, and is emitted from the cathode. An electron gun having an electron beam extraction window for outputting secondary electrons as an electron beam to the outside. 4. An ionization chamber provided with an extraction grid for ionizing the introduced gas at the anode to generate plasma and extracting ions from the plasma, and an ion collision surface formed on a flat surface to be extracted from the ionization chamber. A cathode that emits secondary electrons in the direction of passing through the ionization chamber due to collision of ions, and is arranged so as to surround the ion collision surface of the cathode, and is held at the same potential as the cathode, and on the ion collision surface. A torus converging means for converging the emitted secondary electrons by causing a distortion of the potential distribution, and an electron beam extraction window for outputting the secondary electrons converged by the converging means to the outside as an electron beam An electron gun characterized by. 5. The electron gun according to claim 1, wherein a magnetic lens for converging the electron beam is arranged in front of the electron beam extraction window. 6. The electron gun according to claim 1, wherein a metal foil target for generating an X-ray beam by the secondary electrons is attached to the electron beam extraction window.