JPH0721952A - Electron beam source and X-ray generator applying the same - Google Patents

Abstract

(57) [Summary] [Object] The present invention prevents the diffusion of an electron beam, focuses the electron beam to reduce chromatic aberration, and prevents leakage due to ion diffusion. [Structure] A pulse voltage is applied to a wire (3) placed in a gas atmosphere to generate positive ions, and the positive ions are extracted and collided by a cathode electrode (4) having a negative voltage. When the secondary electrons are accelerated and emitted as an electron beam, the trajectories of positive ions that diffuse with the emission of the secondary electrons are changed and removed by the ion removing means (13). As a result, the positive ions are not emitted to the outside, but the secondary electrons are emitted as an electron beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam source for efficiently outputting a large current electron beam, and an X-ray generator to which the electron beam source is applied.

[0002]

2. Description of the Related Art As an electron beam source, development has been undertaken by applying a mechanism called WIP (wire ion plasma) that generates a plasma by applying a voltage to a wire. In addition to outputting an electron beam, this electron beam source outputs this electron beam to an X-ray such as tungsten.
It is intended to be used as an X-ray generator that irradiates a ray generation source to generate X-rays.

As shown in FIG. 3, the electron beam source having such a mechanism has a structure in which the ion source 1 and the accelerating unit 2 are integrated, and inside the ion source 1 and the accelerating unit 2,
He gas is injected at 10 ^-2 Torr.

In the ion source 1, a wire 3 is stretched linearly in an atmosphere of He gas. The wire 3 is made of tungsten, and a pulse power supply is connected to the outside to apply a DC voltage.

A cathode electrode 4 is arranged in the acceleration unit 2. A direct current accelerating power source is connected to the cathode electrode 4, and a negative voltage of, for example, several tens KV is applied.

Between the ion source 1 and the acceleration unit 2,
The grid 5 is provided, and an Al foil 6 is provided at the electron beam extraction port to prevent ions from leaking to the outside. Further, an aperture 7 is formed.

With such a configuration, when a DC voltage is applied to the wire 3 from the pulse power source, discharge is generated around the wire 3 in the He gas atmosphere and plasma is generated. When this plasma is generated, the positive ions in this plasma are extracted by the negative voltage of the cathode electrode 4 and collide with the cathode electrode 4. Due to this collision, a large amount of secondary electrons are emitted from the cathode electrode 4.

These secondary electrons are accelerated in the opposite direction by the negative voltage of the cathode electrode 4 and emitted to the outside as an electron beam. FIG. 4 shows the cathode voltage (negative voltage) of the cathode electrode 4.
The relationship between the beam current density JB and Vc is shown.

As a result, the secondary electrons are output to the outside as an electron beam through the Al foil 6. When outputting X-rays, the electron beam is converted into X-rays and output using a scintillator.

When the electron beam is output as described above, not only the electron beam but also the positive ions are diffused to the outside. Since this positive ion has energy, it must prevent its output to the outside. Therefore, the positive ions are prevented from leaking to the outside by disposing the Al foil 6 or the mesh.

However, although the Al foil 6 and the like are provided to prevent leakage of positive ions, the electron beam is diffused due to the Al foil 6 and the like. Therefore, energy dispersion, which is one of the characteristics of the electron beam source, is increased, and chromatic aberration is increased.

For example, in the case of an electron beam accelerated to 60 KeV, if the thickness of the Al film 6 is 2 μm, energy dispersion of 805 eV is caused by scattering. This causes a chromatic aberration of 1-2 microns. Therefore, it is impossible to form the electron beam diameter to 1 micron or less.

Further, since the electron beam is restricted by the aperture 7, the diameter of the emitted electron beam becomes wide. When a mesh is used instead of the Al foil 6,
Although the energy dispersion due to scattering is not as great as that of the Al foil 6, the passing area of the electron beam is reduced by the mesh, and as a result, the amount of current is reduced.

[0014]

As described above, the electron beam is diffused, the chromatic aberration is increased, and the diameter of the electron beam is expanded. Moreover, when a mesh is used, the amount of current is reduced.

It is therefore an object of the present invention to provide an electron beam source capable of preventing leakage due to ion diffusion, focusing an electron beam to improve chromatic aberration, and capable of outputting an electron beam having a large amount of current. .

It is another object of the present invention to provide an X-ray generator which can prevent leakage due to ion diffusion and can efficiently generate X-rays by an electron beam that focuses an electron beam and improves chromatic aberration. And

[0017]

According to a first aspect of the present invention, a voltage is applied to an electrode arranged in a gas atmosphere to generate ions, and the ions are attracted to and collided with a negative voltage electrode to generate secondary electrons. In an electron beam source for generating and accelerating this, an electron beam source for achieving the above object by providing an ion removing means for changing and removing the trajectory of ions that diffuse with the emission of secondary electrons is there.

According to the second aspect of the present invention, a voltage is applied to the electrode arranged in the gas atmosphere to generate ions, which ions are attracted to the negative voltage electrode to collide with them to generate secondary electrons. In an electron beam source that accelerates and emits,
An electron beam source that achieves the above object by including an ion removing unit that changes and removes the trajectory of ions that diffuse with the emission of secondary electrons and an electromagnetic lens that focuses and outputs secondary electrons.

According to a third aspect of the present invention, the ion removing means comprises an electric field lens that bends the trajectory of the ions to the outside, and an ion detection aperture that traps the ions bent by the electric field lens.

According to the present invention, a voltage is applied to the electrode arranged in the gas atmosphere to generate ions, and the ions are attracted to the negative voltage electrode to collide with them to generate secondary electrons. In an X-ray generator that irradiates an X-ray generation source with secondary electrons to generate X-rays, ion removal means for changing and removing the orbits of ions that diffuse with the emission of secondary electrons, and a secondary electron focusing device. And an electromagnetic lens for irradiating the X-ray generation source to achieve the above object.

According to a fifth aspect of the invention, the ion removing means in the fourth aspect comprises an electric field lens which bends the trajectory of ions outward similarly to the above, and an ion detection aperture which traps the ions bent by the electric field lens. ing.

[0022]

According to the first aspect of the present invention, a voltage is applied to the electrode arranged in the gas atmosphere to generate ions, the ions are extracted and collided by the negative voltage electrode, and the secondary electrons generated by the collision are generated. When accelerated and emitted, the trajectory of the ions that diffuse with the emission of the secondary electrons is changed and removed by the ion removing means. As a result, the ions are trapped without being emitted to the outside, and the secondary electrons are directly emitted as an electron beam. As a result, a large-current electron beam is output.

According to the second aspect, when the ions are extracted by the negative voltage electrode and collide with each other and the secondary electrons generated by the collision are accelerated and emitted, the ions diffuse with the emission of the secondary electrons. The trajectory of the ions is changed and removed by the ion removing means, and the secondary electrons from which the ions are removed are focused by the electromagnetic lens. As a result, the ions are not emitted to the outside, but the secondary electrons are focused and emitted as an electron beam.

According to the third aspect, the trajectory of the ions diffused together with the secondary electrons is bent outward by the electric field lens, and the bent ions are trapped by the ion detection aperture.

According to the fourth aspect, the secondary electrons from which the ions have been removed in the same manner as described above are focused by the electromagnetic lens and applied to the X-ray generation source. This irradiation causes X from the X-ray source.
Lines are generated. In this case, a large-current electron beam is focused and applied to the X-ray generation source, so that X-rays are efficiently generated. According to the fifth aspect, the ion removal is performed by the electric field lens and the ion detection aperture similarly to the above.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 1 is a block diagram of an electron beam source. The ion source 1 and the acceleration unit 2 are integrally formed, and a gas necessary for plasma generation, such as He gas, is contained in the inside of the ion source 1 and the acceleration unit 2.
-Injected at ² Torr. The ion source 1 and the acceleration unit 2 are grounded.

The ion source 1 is formed with a gas inlet 10 for introducing He gas. A pulse power source 11 is connected to the wire 3 stretched in a straight line, and a pulse voltage of, for example, about 5 KV is applied from the pulse power source 11.

Further, a high voltage DC power supply 12 provided outside is connected to the cathode electrode 4 of the accelerating section 2 so that a negative voltage of several tens KV is applied. Ion removing means 13 is provided in the secondary electron emission direction. The ion removing means 13 has a function of changing the trajectory of positive ions that diffuse with the emission of secondary electrons and removing them.

Specifically, the electric field lens 14 that bends the trajectory of positive ions outward, and the ion detection aperture 15 that traps the positive ions bent by the electric field lens 14.
And have.

Of these, the electric field lens 14 has three coils arranged side by side in the z direction, and a DC power supply 16 is connected to each of these coils. Therefore, when a DC voltage is applied to each coil of the electric field lens 14 from the DC power supply 16, an electric field is generated in the output path of the electron beam.

FIG. 2 shows the curvature r of positive ions in the z direction with respect to the electric field lens 14. As shown in the figure, it is found that the trajectories of positive ions are changed to the outside with respect to the path of the electron beam.

The ion detection aperture 15 traps positive ions bent by the electric field lens 14,
The other end is grounded. Further, an electromagnetic lens 17 is arranged in parallel with the ion removing means 13 in the path direction of the electron beam. This electromagnetic lens 17 is a lens power source 1
8 has a function of focusing the electron beam by generating a magnetic field in the output path of the electron beam by applying a voltage from the lens power source 18.

A beam outlet 19 is formed. Next, the operation of the electron beam source configured as described above will be described. When a DC voltage is applied to the wire 3 from the pulse power supply 11, discharge is generated in the wire 3 and plasma is generated around the wire 3. In this case, the DC voltage of the pulse power supply 11 varies depending on the type of gas and the gas pressure, but He. In the case of 30 mtorr, it is about 5 KV, and discharge starts at this voltage.

When the plasma is generated in this way, the positive ions in the plasma pass through the mesh 5 and are drawn to the negative voltage of the cathode electrode 4, accelerated and collide with the cathode electrode 4. Due to this collision, a large amount of secondary electrons are emitted from the cathode electrode 4.

Here, these secondary electrons are accelerated in the opposite direction this time by the negative voltage of the cathode electrode 4, pass through the plasma, and are emitted to the outside as an electron beam. At this time, positive ions also diffuse with the secondary electrons. Since this positive ion has some energy, it needs to be removed.

That is, the electric field lens 14 has a DC power source 1
A DC voltage is applied from 6 to generate an electric field. Due to this electric field, the trajectories of positive ions are largely bent outward. Then, these positive ions are trapped by the ion detection aperture 15.

On the other hand, the secondary electrons are slightly focused by the electric field of the electric field lens 14, are focused by the magnetic field generated by the next electromagnetic lens 17, and are emitted from the beam extraction port 19. As a result, all the secondary electrons generated at the cathode electrode 4 are output from the beam extraction port 19 as an electron beam.

As described above, in the above-mentioned one embodiment, He
A voltage is applied to the wire 3 arranged in the gas to generate positive ions, the positive ions are extracted by the cathode electrode 4 and collided to generate secondary electrons, and the secondary electrons are accelerated to form an electron beam. At the time of emission, the orbits of the positive ions that diffuse with the emission of the electron beam are bent by the electric field lens 14, so that the positive ions can be trapped without being emitted to the outside and only secondary electrons can be output as an electron beam. . Therefore, the positive ions can be removed without arranging Al or the like in the path through which the secondary electrons pass, all the generated secondary electrons can be output as an electron beam, and a high-current electron beam can be obtained.

Further, since the secondary electron is focused by the electromagnetic lens 17, the diameter of the electron beam can be made small, and it can be made narrower depending on the design of the electromagnetic lens 17. In particular, since the electron beam is not diffused by the Al foil 6 or the like, the energy dispersion, which is one of the characteristics of the electron beam source, can be reduced and the chromatic aberration can be reduced. For example, in the past, the energy dispersion of 805 eV caused the scattering of Al foil having a thickness of 2 μm to cause chromatic aberration of 1 to 2 μm. Becomes

Next, a second embodiment of the present invention will be described. An X-ray generator is configured by applying the above electron beam source. This X-ray generator can be realized by arranging tungsten, tantalum, or the like as an X-ray generation source at the beam extraction port 19 of the electron beam source shown in FIG.

When the X-ray generation source such as tungsten is arranged at the beam extraction port 19 as described above, the electron beam is focused by the electromagnetic lens 17 and is applied to the X-ray generation source. At this time, since the electron beam is extracted and focused as a large current, it is efficiently converted into X-rays by the X-ray generation source.

The present invention is not limited to the above-mentioned one embodiment, and can be modified within the scope of the invention.
For example, the electromagnetic lens 17 may or may not be provided depending on the application to which it is applied. That is, the electromagnetic lens 1
7 is necessary when it is necessary to focus the electron beam, and if not, it is possible to output an electron beam having a sufficiently large current amount without focusing the electron beam.

[0043]

As described in detail above, according to the present invention, an electron beam capable of preventing leakage due to ion diffusion, focusing an electron beam to improve chromatic aberration, and capable of outputting an electron beam having a large current amount. Can provide the source.

Further, according to the present invention, it is possible to prevent leakage due to ion diffusion, focus the electron beam, and efficiently generate X-rays by the electron beam with improved chromatic aberration.
A line generator can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an electron beam source according to the present invention.

FIG. 2 is a diagram showing the curvature of positive ions.

FIG. 3 is a configuration diagram of a conventional electron beam source.

FIG. 4 is a diagram showing a current density of an electron beam with respect to a voltage of a cathode electrode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion source, 2 ... Accelerator, 3 ... Wire, 4 ... Cathode electrode, 5 ... Mesh, 10 ... Gas inlet, 11 ... Pulse power supply, 12 ... High voltage DC power supply, 13 ... Ion trajectory changing means, 14 ... Electric field Lens, 15 ... Ion detection aperture,
16 ... DC power supply, 17 ... Electromagnetic lens, 18 ... Lens power supply, 19 ... Beam extraction port.

Claims (5)

[Claims] 1. A voltage is applied to an electrode arranged in a gas atmosphere to generate ions, which ions are attracted to and collide with a negative voltage electrode to generate secondary electrons, which are accelerated and emitted. An electron beam source, comprising an ion removing means for changing and removing the trajectory of ions that diffuse with the emission of the secondary electrons. 2. A voltage is applied to an electrode arranged in a gas atmosphere to generate ions, the ions are attracted to and collided with a negative voltage electrode to generate secondary electrons, which are accelerated and emitted. An electron beam source, comprising: an ion removing unit that changes and removes the trajectory of ions that diffuse with the emission of the secondary electrons, and an electromagnetic lens that focuses and outputs the secondary electrons. Beam source. 3. The ion removing means comprises an electric field lens that bends the trajectory of the ions outward, and an ion detection aperture that traps the ions bent by the electric field lens. Electron beam source. 4. A voltage is applied to an electrode arranged in a gas atmosphere to generate ions, and the ions are attracted to and collided with a negative voltage electrode to generate secondary electrons. In an X-ray generator that irradiates a generation source to generate X-rays, an ion removing unit that changes and removes orbits of ions that diffuse with the emission of the secondary electrons, and the X-ray that focuses the secondary electrons. An X-ray generation device, comprising: an electromagnetic lens for irradiating a ray generation source. 5. The X-ray according to claim 4, wherein the ion removing means comprises an electric field lens that bends the trajectory of the ion outward and an ion detection aperture that traps the ion bent by the electric field lens. Generator.