JP3063327B2 - Strongly focused charged particle acceleration / deceleration tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strongly focused charged particle acceleration / deceleration tube for accelerating or decelerating charged particles such as ions and electrons by a DC voltage, and more particularly to a high current ion beam generator. The present invention relates to an acceleration / deceleration tube suitable for being configured.

[0002]

2. Description of the Related Art In order to accelerate or decelerate charged particles using a DC voltage, an apparatus having a structure as shown in FIG. 4 has been used. This device generates an ion beam, and an ion source a, an extraction electrode b, and an acceleration / deceleration tube c are sequentially arranged along a z-axis direction that is an ion passage axis. In the example, it is constituted by _three hollow cylindrical electrodes c ₁ , c ₂ and c ₃ . Each of the electrodes c ₁ , c ₂ and c ₃ is provided with a DC power supply circuit H for applying a DC voltage having a potential difference in a predetermined direction in accordance with the arrangement order. E and a voltage-dividing resistor R ₁ , which divides the DC voltage from now on to a predetermined value.
R ₂ .

In the above configuration, for example, when positive ions are accelerated as charged particles, each electrode c ₁ ,
The voltage applied to c ₂ and c ₃ is set to be lower from the electrode c ₁ on the extraction electrode b side to the electrode c ₃ on the final stage. In this state, the positive ions generated in the ion source a are extracted by the potential difference between the ion source a and the extraction electrode b, and then sequentially pass through the inside of each of the electrodes c ₁ , c ₂ , c ₃ , and then z
It is gradually accelerated along the axial direction.

[0004] In the case of decelerating the positive ions is to reverse the positive and negative electrode of the DC power source E, is higher DC voltage directed from electrode c ₁ of the lead electrode side b on the electrode c ₃ of the final stage is applied It is set as follows.

Incidentally, in the accelerating / decelerating tube c having the conventional configuration, the electrodes c ₁ , c ₂ , and c ₃ have a hollow cylindrical shape.
The focusing force on the charged particles is weak, and therefore, the charged particle beam tends to diverge along the x-axis direction and the y-axis direction orthogonal to the z-axis due to the Coulomb force acting between the charged particles.
In particular, there is a problem that efficiency is low when accelerating or decelerating a large current ion beam.

Accordingly, the present inventors have provided a strongly focused type charged particle acceleration / deceleration tube having the structure shown in FIG.

In the strongly focused type charged particle acceleration / deceleration tube g, the central axes of the two cylindrical electrodes g ₁ a and g ₁ b, g ₂ a and g ₂ b,... Electrode pairs g ₁ , g ₂ ,..., Which are arranged in parallel with the respective axes, and in which both electrodes g ₁ a and g ₁ b, g ₂ a and g ₂ b,. (In this example, five pairs), and the electrode pairs g ₁ , g ₂ ,... Are arranged along the z-axis direction so as to have a portion overlapping on a plane orthogonal to the z-axis. Further, a DC power supply circuit H is provided for applying a DC voltage having a potential difference in a predetermined direction according to the arrangement order to each of the electrode pairs g ₁ , g ₂ , g ₃ ,.
This DC power supply circuit H is composed of a high-voltage DC power supply E and a DC voltage to be divided into predetermined voltage values so that each electrode pair
It consists of voltage dividing resistors R _{1 to} R ₄ to be applied to g _{1 to} g ₅ .

[0008] In this configuration, when accelerating as charged particles for example the positive ions, the voltage to be applied in advance to each pair of electrodes g ₁ to g _5, of the lead electrode b side from the electrode pair g ₁ of the last stage It is set to be lower as toward the electrode pair g _5.

In this state, positive ions generated by the ion source a are extracted by the potential difference between the ion source a and the extraction electrode b, and then pass between the electrode pairs g ₁ to g ₅ .
It is gradually accelerated along the z-axis direction.

Moreover, in this case, an electrode having a substantially quadrupole structure is formed in the overlapping portion of each of the electrode pairs g ₁ to g ₅ . For example, in the overlapping portion of the electrode pair g ₁ and g _{2 in} the first and second stages (the cross-sectional position along the line AA in FIG. 5), the potential of the ions is equal to the potential of each of the electrode pairs g ₁ and g ₂ It has an intermediate value. Therefore, in this overlapping part, as shown in FIG.
If relative to the potential of the ions, the potential of one electrode pair g ₁ is relatively high, the potential of the other electrode pair g ₂ is relatively low. As a result, a focusing force acts on this ion along the x-axis direction. Similarly, in the overlapping portion of the second and third electrode pairs g ₂ and g ₃ , when the potential of the ion is used as a reference, the potential of one electrode pair g ₂ is relatively high and the other electrode pair g 2 _Since the potential of ₃ becomes relatively low, a focusing force acts along the y-axis direction. As a result, this ion as a whole
while it is accelerated along the z-axis direction, so that the divergence of the ion is suppressed by the overlapping portion of each electrode pair g ₁ to g _5.

When decelerating the positive ions, the positive and negative electrodes of the DC power source E are reversed, and the pair of electrodes g on the side of the ion extraction electrode b are set.
High DC voltage as it goes from ₁ to the electrode pair g ₅ in the final stage side is set to be applied.

[0012]

The strongly focused type charged particle accelerating / decelerating tube shown in FIG. 5 has a structure different from that of the structure shown in FIG.
The focusing power on the charged particles is large, and the divergence can be suppressed.

However, as a result of further intensive studies, the present inventors have found that the structure shown in FIG. 5 has the following problems.

That is, the electrodes constituting each of the electrode pairs g ₁ to g ₅
g ₁ a, g ₁ b, g ₂ a, g ₂ b,... are all of the same length l ₀ and of the same diameter d ₀ , and on the same circle with a constant radius R ₀ about the z-axis. Since all are arranged, the degree of freedom in efficiently accelerating and decelerating charged particles is small, and it is particularly difficult to accelerate and decelerate a high-current ion beam.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has a large focusing force in the process of accelerating and decelerating a charged particle so that a large current charged particle beam can be formed. This is to accelerate and decelerate efficiently.

Therefore, according to the present invention, the two cylindrical electrodes are arranged such that their respective central axes are parallel to the charged particle passing axis, respectively, and both electrodes are arranged to face each other around the charged particle passing axis. With a plurality of electrode pairs, each electrode pair is a strongly focused type charged particle accelerating / decelerating tube arranged along the charged particle passing axis direction so as to have a portion overlapping on a plane orthogonal to the charged particle passing axis, The following configuration is adopted.

That is, in the present invention, the diameter of the electrodes constituting at least one electrode pair, the distance from the charged particle passing axis, or the length in the charged particle passing axis direction is determined by the electrodes constituting the remaining electrode pairs. , The distance from the charged particle passing axis, or the length in the charged particle passing axis direction.

[0018]

In the above configuration, the focusing force is adjusted by increasing (or weakening) the electric field formed between the electrode pairs. Alternatively, the focusing power is adjusted by lengthening (shortering) the duration of the focusing action.

[0019]

EXAMPLE 1 intensity focused charged particle acceleration tube structure of this first embodiment is basically the same as in the conventional example shown in FIG. 5, it is different in the following points.

[0020] That is, in the conventional example, as shown in FIG. 6, the cylindrical electrode g ₁ a constituting the g ₁ to g ₅ each electrode pair, g ₁ b,
g ₂ a, g ₂ b,... are all of the same length l ₀ and the same diameter d ₀ , and are all arranged on a circle with a constant radius R ₀ about the z-axis. Te, in the first embodiment, as shown in FIG. 1, each electrode pair g _1, g _2, electrodes g ₁ a constituting the ..., g
The diameters d ₁ , d ₂ ,... Of ₁ b, g ₂ a, g ₂ b,.

For example, the first-stage electrode pair g on the extraction electrode b side
The diameter of the electrodes g ₁ a and g ₁ b that constitute ₁ is d ₁ , and the electrode pair g in the second stage
Electrodes g ₂ a constituting the _two, when the diameter of g ₂ b and d _2, d _1> d ₂
Is set to be However, any of the electrodes g ₁ a, g
₁ b, in g ₂ a, g ₂ b also identical length along the z-axis l, and are arranged on a circle of constant radius R ₀ around the z axis.

In this structure, when positive ions are accelerated as charged particles, for example, the first and second electrode pairs are accelerated.
In the overlapping portion of g ₁ and g ₂ , the potential of the ion is the pair of electrodes g ₁ and g ₂
Becomes an intermediate value between the respective potentials. Therefore, in this overlapped portion, when relative to the potential of the ions, the potential of one electrode pair g ₁ is relatively high, the potential of the other electrode pair g ₂ is relatively low. Moreover, in this case, the two electrodes g ₁ a and g ₁ b constituting _one electrode pair g ₁ having a higher potential with respect to the ions are the two electrodes g constituting the other electrode pair g ₂ having a lower potential.
₂ a, short mutual distance of the electrode pair than g ₂ b, since the electric field formed between the electrodes acts strongly, it will act stronger focusing force along the x-axis direction with respect to the ion .

Similarly, for example, for the fourth and fifth electrode pairs g ₄ and g ₅ , the diameter of the _fourth electrode g ₄ a and g ₄ b is set to d.
_1, by setting the fifth stage of the electrodes g ₅ a, the diameter of the g ₅ b to d _2, with overlapped portions of both electrode pairs g _4, g _5, when relative to the potential of the ions, whereas the potential of the electrode pair g ₄ is relatively high,
The potential of the other electrode pair g ₅ is relatively low and, the electrodes g ₄ a constituting one electrode pair g ₄ high potential with respect to ions, is more of g ₄ b, a low potential and the other electrode is short mutual distance than pair g ₅ both electrodes g ₅ a constituting, g ₅ b, a strong focusing force is applied along the y-axis direction.

As a result, while the ions are accelerated as a whole along the z-axis direction, the divergence of the ions is suppressed by the overlapping portions of the electrode pairs g ₁ to g ₅ .

Embodiment 2 In this embodiment 2, as shown in FIG. 2, each electrode pair g ₁ ,
g _2, are made different ... electrodes g ₁ a _{constituting, g 1 b, g 2 a} , g 2 b, the distance from ... z axis in accordance with the arrangement order of.

For example, the first-stage electrode pair g on the extraction electrode b side
_The electrodes g ₁ a and g ₁ b constituting the _{first 1 have} a radius R ₁ around the z-axis.
Disposed on the circle, electrodes g ₂ constituting the second stage of the electrode pair g ₂
a, g ₂ b are arranged on a circle of radius R ₂ around the z-axis,
It is set so that R ₁ <R ₂ . However, any of the electrodes g ₁ a, in _{g 1 b, g 2 a,} g 2 b also identical length l ₀ along the z-axis, and is of the same diameter d _0.

In the second embodiment, as in the _first embodiment, both electrodes g ₁ a and g ₁ b constituting _one electrode pair g ₁ having a higher potential with respect to ions are connected to the other electrode g ₁ a having a lower potential. The distance between the electrodes is shorter than that of both electrodes g ₂ a and g ₂ b constituting the electrode pair g _2, and a strong electric field is formed. Therefore, a strong focusing force is applied to these ions along the x-axis direction. Will work.

Similarly, for example, with respect to the fourth and fifth electrode pairs g ₄ and g ₅ , the fourth-stage electrodes g ₄ a and g ₄ b are positioned on a circle having a radius R ₁ about the z-axis. placed, 5-stage electrodes g ₅ a, g ₅
b, if placed on a circle of radius R ₂ about the z axis, a strong focusing force is applied along the y-axis direction.

As a result, while the ions are accelerated as a whole along the z-axis direction, the divergence of the ions is suppressed by the overlapping portions of the electrode pairs g ₁ to g ₅ .

[0030] Example 3 strongly focused charged particle acceleration tube g of this third embodiment, two cylindrical electrodes g ₁ a and g ₁ b, g ₂ a and g ₂ b, ... are each a central axis of In a state parallel to the z-axis, respectively, and both electrodes g ₁ a and g
₁ b, g ₂ a and g ₂ b, the electrode pair g ₁ formed by arranging facing the ... around the z-axis, g _2, ... with a comprises a plurality of (six pairs in this example),
The electrode pairs g ₁ , g ₂ ,... Are arranged along the z-axis direction so as to overlap each other on a plane orthogonal to the z-axis. Then, each electrode pair g ₁ to g _6, the length of the z-axis direction is set to be different alternately along the z-axis direction. For example, as shown in FIG. 3, for each of the electrode pairs g ₁ , g ₃ , and g ₅ , l ₁ , l ₂ , l
₁ (where l ₁ > l ₂ ), and the electrode pairs g ₂ , g ₄ , and g ₆ are set so as to satisfy l ₂ , l ₁ , and l ₂ , respectively. However, any of the electrodes g ₁ a, g ₁ b, g ₂ a, g ₂ b,
... also have the same diameter d ₀ and a constant radius R ₀ about the z-axis.
Are arranged on a circle. Incidentally, H is relative to each pair of electrodes g ₁ to g _6, a DC power supply circuit for applying a DC voltage marked a potential difference of a predetermined direction in accordance with the arrangement order, and the DC power source E of a high pressure, from which the DC voltage partial pressure for applying a divide each electrode pair g ₁ to g ₅ each predetermined voltage value resistor R ₁
Consisting of ~R ₅ Metropolitan.

In the strongly focused charged particle acceleration / deceleration tube g having the above structure, for example, when a positive ion beam is obtained, an electrode having a substantially quadrupole structure is formed at an overlapping portion of each of the electrode pairs g ₁ to g _6. Therefore, positive ions are gradually accelerated along the z-axis direction.

At this time, when the potential of the ion is used as a reference,
Both electrodes constituting _one electrode pair g1 having a higher potential than this
g ₁ a and g ₁ b have a longer length in the z-axis direction (l ₁ > l ₂ ) than both electrodes g ₂ a and g ₂ b forming the other electrode pair g ₂ having a lower potential. Then, a focusing force acts on the ions in the x-axis direction for a time corresponding to the difference in the distance for a long time.

[0033] Similarly, for example, the electrode pair g ₃ and g _4, since the direction of the electrode pairs of g ₄ is longer in length than the electrode pair g _3, a strong focusing force along the y-axis direction Works.

As a result, while the ions are accelerated as a whole along the z-axis direction, the divergence of the ions is suppressed by the overlapping portions of the electrode pairs g ₁ to g ₆ .

It is needless to say that a charged particle accelerating / decelerating tube having a strong converging power can similarly be constructed by combining the above-described embodiments 1-3.

In the first to third embodiments, the acceleration / deceleration pipe
The case where positive ions are accelerated by g has been described, but negative ions have a deceleration effect. By reversing the direction of the potential difference applied to the electrode pairs g ₁ , g ₂ ,... Constituting the accelerating / decelerating tube g, it is possible to decelerate positive ions and accelerate negative ions, and also to reduce electrons. Needless to say, acceleration and deceleration can be performed in the same manner.

[0037]

According to the present invention, since the charged particles have a large focusing force in the process of accelerating and decelerating the charged particles, a charged particle beam having a large current can be efficiently generated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a strongly focused type charged particle acceleration / deceleration tube according to an embodiment of the first invention, as viewed from a charged particle passing axis (z-axis) direction.

FIG. 2 is a cross-sectional view of a strongly focused type charged particle acceleration / deceleration tube according to an example of the second invention as viewed from a charged particle passing axis (z-axis) direction.

FIG. 3 is a schematic configuration diagram of a strongly focused type charged particle acceleration / deceleration tube according to an example of the third invention when viewed from an x-axis direction orthogonal to a charged particle passing axis (z-axis).

FIG. 4 is a schematic configuration diagram when an arrangement state of an ion beam generator including a conventional acceleration / deceleration tube is viewed from an x-axis direction orthogonal to a charged particle passing axis (z-axis).

FIG. 5 is a schematic configuration diagram of an arrangement state of an ion beam generator including a conventional acceleration / deceleration tube when viewed from an x-axis direction orthogonal to a charged particle passing axis (z-axis).

FIG. 6 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

a ... ion source, b ... lead electrodes, g ₁ to g ₆ ... electrode pair, g ... strongly focused charged particle acceleration _{tube, g 1 a, g 1 b} , g 2 a, g 3 b ... electrode,
d ₀ , d ₁ , d ₂ ... diameter of the electrode, R ₀ , R ₁ , R ₂ ... distance from the passing axis of charged particles, l ₀ , l ₁ , l ₂ ... length of the electrode.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05H 5/03 H05H 5/00

Claims (1)

(57) [Claims] 1. A plurality of electrode pairs each having a central axis of two cylindrical electrodes parallel to a charged particle passing axis, and having both electrodes disposed around the charged particle passing axis. A strong focusing type charged particle acceleration / deceleration tube, which is arranged along the charged particle passing axis direction so as to have a portion overlapping on a plane orthogonal to the charged particle passing axis, wherein at least one electrode is provided. The diameter of the electrode constituting the pair, the distance from the charged particle passing axis, or the length in the charged particle passing axis direction, the diameter of the electrode constituting the remaining electrode pair, the distance from the charged particle passing axis, or A strongly focused charged particle acceleration / deceleration tube, wherein the length is set to be different from the length of the charged particle passing axis direction.