JP3099905B2 - Charged particle generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the Invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle generator for accelerating charged particles such as ions and electrons by an electric field and using the accelerated particles as a high energy beam.

[0003]

2. Description of the Related Art FIG. 5 shows a conventional charged particle generator 1. In FIG. 1, a charged particle generation device 1 includes a charged particle generation unit 3 that generates charged particles (eg, ions) and an acceleration unit 5 that accelerates the charged particles formed by the charged particle generation unit 3. ing. The charged particle generator 3 is provided with a discharge chamber 4. In this discharge chamber 4,
An electrode (not shown) is provided. A discharge gas is supplied into the discharge chamber 4 by supply means (not shown), and a voltage is applied between the electrode and the inner wall of the discharge chamber 4 to discharge the gas in the gas. Is generated in the discharge chamber 4.

In the accelerating unit 5, electrodes 7, 9, 11, 13, 15 are connected in sequence to the discharge chamber 4, and are arranged in this order.
Insulating materials 17, 19, 21, 23, and 25 are provided between the acceleration electrodes 7, 9, 11, 13, and 15, respectively. These insulating materials 17, 19, 21, 2
Reference numerals 3 and 25 denote a discharge chamber 4 and case electrodes 7, 9, 11, 13,
15 are insulated from each other. An accelerating voltage is applied between the accelerating electrodes 7 and 15 by a power source (not shown) by the power supply (not shown).
Reference numeral 3 divides and applies the voltage applied between the acceleration electrodes 7 and 15. The number of these acceleration electrodes 7, 9, 11, 13, 15 increases or decreases depending on the method of use. Further, a large number of circular ion passage holes 27 are formed in the accelerating electrodes 7, 9, 11, 13 and 15, and these ion passage holes 2 are formed.
7 are accelerated while ions i (see FIG. 6) are drawn in the direction of arrow a (the traveling direction of the ions).

However, in the charged particle generator 1, when a high voltage is applied between the acceleration electrodes 7 and 15 in order to accelerate the ions i at a high speed (high energy), the voltage applied between the acceleration electrodes 7 and 15 is increased. , The dielectric breakdown between the accelerating electrodes 7, 9, 11, 13 and 15 is more likely to occur.

Hereinafter, the aforementioned accelerating electrodes 7, 9, 11, 1
The dielectric breakdown between 3 and 15 will be described with reference to FIG.
The dielectric breakdown between the accelerating electrodes 7, 9, 11, 13, 15 may be induced by electrons emitted together with the ions from the accelerating electrodes 9, 11, 13, 15.

That is, the ions i extracted from the charged particle generator 3 are accelerated by the electric fields created by the accelerating electrodes 7, 9, 11, 13 and 15, and move through the ion passage holes 27 of each accelerating electrode in the direction of arrow a. pass. Each electrode 9, 11,
When passing through the respective ion passage holes 27 of the electrodes 13 and 15, the ions are converted into gas molecules between the accelerating electrodes (from the discharge chamber 4 to the ion passage holes
Secondary gas, which collide with the gas flowing out through 7)
Generate electrons.

The ions and electrons emitted secondarily are accelerated by the electric field formed by the accelerating electrodes 7, 9, 11, 13, and 15 and collide with one of the accelerating electrodes, thereby causing the accelerating electrodes 7, 9, and Electrons are further emitted from 11, 13, and 15. When the charged particles colliding with the accelerating electrodes 9, 11, 13, 15 are secondary ions, the accelerating electrodes 7, 9, 11,.
The number of electrons emitted from 13 and 15 becomes several times to several tens times the number of ions, and the electron e emitted from any one of the acceleration electrodes 7, 9, 11, 13 and 15 is transferred to another acceleration electrode. Collision is one of the causes of dielectric breakdown between the accelerating electrodes.

For example, in FIG. 6, ions i collide with gas molecules to generate secondary ions i 2 _and electrons e 2, and these ions i 2 and electrons e 2 are accelerated by an electric field and collide with the accelerating electrode 11. , Further electrons e from the accelerating electrode 11
Release. The emitted electrons e are stored in the accelerating electrode 11
Collides with the accelerating electrode 13 adjacent to. As a result, the insulating state between the acceleration electrode 11 and the acceleration electrode 13 is broken.

Therefore, the acceleration electrodes 7, 9, 11, 13, 1
When a high voltage is applied to 5, the accelerating electrodes 7, 9, 11, 1
3, 15 and the power supply may be destroyed. For this reason, dielectric breakdown between the accelerating electrodes 7, 9, 11, 13, and 15 was one of the causes of inhibiting the increase in energy and current of the ion source.

[0011]

As described above, in the conventional charged particle generator, when a high voltage is applied, electrons generated by collision of secondary ions and electrons with the accelerating electrodes cause a gap between the accelerating electrodes. There was a problem of dielectric breakdown.

Accordingly, an object of the present invention is to provide a charged particle generator capable of reducing the frequency of occurrence of dielectric breakdown between acceleration electrodes even when a high voltage is applied between the acceleration electrodes.

[Structure of the Invention]

[0014]

According to the present invention, there is provided a charged particle generating section for generating charged particles , and a plurality of charged particles generated by the charged particle generating section passing therethrough.
Through holes are formed respectively, and the charged particles are
The charged particle generating apparatus comprising a acceleration unit having a plurality of accelerating electrodes for accelerating, between the passage hole of the acceleration electrode
Embedded in the area of
Form magnetic lines of force from one side of the area between the holes to the other.
Thus, magnetic field forming means for forming a magnetic field around the region between the passage holes of the acceleration electrode is provided.

[0015]

According to the present invention, charged particles such as ions generated in the charged particle generating section are extracted from the charged particle generating section by the acceleration electrode of the accelerating section and then accelerated while passing through the passage hole. The extracted charged particles collide with the gas between the accelerating electrodes and generate secondary charged particles. The secondary charged particles collide with the accelerating electrode and emit electrons from the accelerating electrode. The electrons emitted from the accelerating electrode again collide with the accelerating electrode due to a magnetic field in which the lines of magnetic force travel from one side of the region between the passage holes to the other side by the magnetic field forming means. In other words, the electrons emitted from the accelerating electrodes return to the accelerating electrodes again due to the magnetic field, so that the emission of the electrons from the accelerating electrodes is suppressed, and the electrons do not collide with other accelerating electrodes. Frequency can be reduced.

[0016]

Next, an embodiment of a charged particle generator according to the present invention will be described with reference to FIGS. The same components as those of the charged particle generator shown in FIG. 6 are denoted by the same reference numerals in the drawings, and redundant description will be omitted. The charged particle generator according to the present embodiment is an ion beam generator for accelerating ions as charged particles. FIG. 2 is an enlarged view of a part of FIG. 1, and FIG. 3 is an enlarged view of a part of FIG.

As shown in FIGS. 1 and 2, the acceleration electrodes 9, 11, 1 provided in the acceleration unit 5 of the charged particle generator 31 are provided.
Each of the permanent magnets 3 and 15 has a plurality of permanent magnets 33 so that the same poles (S-pole and S-pole and N-pole and N-pole) face each other through a circular ion passage hole 27.

As shown in FIG. 3, the permanent magnets 33 are magnetized in a direction substantially perpendicular to the traveling direction (the direction of arrow a) of ions as charged particles.
The magnetic field lines 3 form a magnetic field around the acceleration electrodes 9, 11, 13, and 15 so as to surround the acceleration electrodes 9, 11, 13, and 15.

The ions i generated by the charged particle generator 3
Are extracted by the accelerating electrode 7, and then
It is accelerated and emitted while passing through the ion passage holes 27 of 11, 13, and 15. While passing between the accelerating electrodes 9, 11, 13, and 15, the ion i collides with gas molecules flowing out of the charged particle generation unit between the accelerating electrodes, and generates secondary ions i and electrons e. . This secondary ion i, electron e
Collide with the accelerating electrodes 9, 11, 13, 15. Then, electrons e are emitted from the acceleration electrodes 9, 11, 13 and 15. The electrons e emitted from the acceleration electrode return to the emitted acceleration electrode without colliding with other acceleration electrodes due to the magnetic field formed by the permanent magnet 33 around the acceleration electrodes 9, 11, 13, 15.

Therefore, since the electrons emitted from any one of the acceleration electrodes 9, 11, 13, 15 do not collide with the other electrodes, the frequency of dielectric breakdown between the acceleration electrodes 7, 9, 11, 13, 15 is reduced. Can be reduced.

Hereinafter, the function of the magnetic field formed by the permanent magnet 33 will be described.

As shown in FIG. 3, the acceleration electrodes 7, 9, 11,
In the vicinity of 13 and 15, the accelerating electrodes 7, 9, 11, 13,
The direction of the electric field formed by 15 and the direction of the magnetic field formed by the permanent magnet 33 are orthogonal to each other. Acceleration electrodes 7, 9, 11, 13, 15
The initial velocity when the electrons emitted from the electron depart from the accelerating electrode is substantially zero, and when the electric field and the magnetic field are orthogonal, the electron e drifts while making a circular motion in the direction orthogonal to the magnetic field.
When the radius of the circular motion is smaller than that between the accelerating electrodes, the electrons e return to the original accelerating electrode 11 again, and do not cause dielectric breakdown of the accelerating electrode.

Here, for example, the magnetic flux density B required for suppressing the emission of the electrons e emitted from the acceleration electrode 11 is estimated. The radius a of the circular motion of the electron e is expressed by the following equation.

A = (E / B) / ω _{e In the} above equation, E is the magnitude of the electric field, B is the magnetic flux density, ω
_e is the electron cyclotron frequency. Taking an ion source as an example, the magnitude E of the electric field is approximately 5 KV / mm, and the allowable radius a is approximately 5 mm. The required magnetic flux density B is 7
It is about 50 Gauss. This level of magnetic flux density B is a value that can be realized by using a rare earth magnet or a neodymium / iron magnet. Further, the magnetic field formed by the permanent magnet 33 has almost no effect on the movement of the accelerated ions, and the influence on the charged particle generator 31 can be ignored.

Therefore, the surface of the accelerating electrode 11 is
3 and the electrons e from the accelerating electrode 11
Release can be suppressed. As a result, a high voltage is applied between the accelerating electrodes 7 and 15 to accelerate the ions at high speed (high energy), thereby obtaining a high energy beam.

Next, another embodiment in which the magnetization directions of the permanent magnets 33 are different will be described with reference to FIG.

The permanent magnet 33 shown in FIG. 4 is built in the accelerating electrodes 9, 11, 13 and 15 via the ion passage holes 27 so that the magnets face different polarities. The magnetic field lines 37 of the permanent magnet 33 form a magnetic field around the acceleration electrodes 9, 11, 13, and 15 so as to surround the acceleration electrodes 9, 11, 13, and 15.

In this embodiment, the emission of electrons from the accelerating electrodes 9, 11, 13 and 15 can be suppressed in the same manner as in the above embodiment, and the dielectric breakdown between the accelerating electrodes 9, 11, 13 and 15 can be suppressed. Frequency can be reduced. In the present embodiment, as shown in FIG. 4, the permanent magnets 33 approaching through the ion passage holes 27 are arranged so that different poles face each other. May exist, but the presence of magnetic field lines in a direction crossing the ion passage direction does not affect the ion passage.

[0029]

[0030]

In each of the above embodiments, the ion passage hole 2
Although the shape of the hole 7 is a round hole, the shape is not limited to this, and the shape of the ion passage hole 27 may be another shape. The operation of the present invention does not depend on the shape of the hole.

In the above embodiment, the direction of the lines of magnetic force of the permanent magnet 33 is set to a direction orthogonal to the traveling direction of ions. However, the present invention is not limited to this. A similar effect can be expected. Further, as long as a magnetic field can be formed around the acceleration electrode so as to enclose the acceleration electrode, the position where the permanent magnet 33 is incorporated may be any position.

Further, in each of the above embodiments, the example in which the permanent magnet 33 is built in the acceleration electrodes 9, 11, 13 and 15 as the magnetic field forming means has been described. 13 and 15 may be incorporated.

[0034]

[0035]

As described above, according to the charged particle generator of the present invention, when a high voltage is applied between the accelerating electrodes, the frequency of occurrence of dielectric breakdown between the accelerating electrodes can be reduced. Thus, an excellent effect that a high voltage can be applied to the acceleration electrode and a high energy beam can be obtained can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a charged particle generator according to the present invention.

FIG. 2 is a cross-sectional view showing a relationship between an accelerating electrode and a permanent magnet in which a part of FIG. 1 is enlarged.

FIG. 3 is a cross-sectional view schematically illustrating magnetic lines of force of a permanent magnet and an enlarged part of FIG. 2;

FIG. 4 is an explanatory diagram showing another example showing the arrangement of permanent magnets.

FIG. 5 is a cross-sectional view showing a configuration of a conventional charged particle generator.

FIG. 6 is an explanatory diagram showing a conventional relationship between an accelerating electrode and a traveling direction of a charged particle.

[Explanation of symbols]

 3 Charged particle generator 5 Accelerator 7, 9, 11, 13, 15 Acceleration electrode 27 Ion passage hole 31 Charged particle generator 33 Permanent magnet 35, 37 Magnetic field lines

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 27/00-27/26 H01J 37/06-37/077 H01J 37/08

Claims (1)

(57) [Claims] 1. A charged particle generation unit for generating charged particles,
A large number of charged particles generated by this charged particle generator
Are formed respectively, and the charged particles are
A charged particle generator comprising: a plurality of accelerating electrodes having a plurality of accelerating electrodes for accelerating the accelerating electrodes.
From one side of the region between the passage holes of the acceleration electrode to the other side.
By forming the magnetic field lines heading toward the
A charged particle generating apparatus, further comprising magnetic field forming means for forming a magnetic field around the region between the passage holes .