JPH05251200A - High frequency quadrupole accelerator - Google Patents

Abstract

PURPOSE:To provide a high frequency quadrupole accelerator capable of restraining an electric power loss by forming an inner wall of a casing of a material having a low specific electric resistance while keeping, the strength by the use of a material excellent in strength. CONSTITUTION:A cylindrical casing 12 constituting a resonant cavity of a high frequency quadrupole accelerator 10 is formed of a clad material consisted of a material having a low specific electric resistance at the inner surface thereof and of a material excellent in mechanical strength at the outer surface thereof. Consequently, the inner surface of the casing can be made of a material capable of restraining an electric power loss having a specific electric resistance lower than a surface current flowing in an inner wall and excellent in mechanical strength and the like at most of the material thickness, so that the material thickness for obtaining the same strength can be reduced and weight reduction of the accelerator can be realized. The weight can reduce strength limitation and facilitate incorporation with an ion implanter or the like, thus contributing to weight reduction of the ion implanter or the like. Additionally, the outer surface of the casing is formed of the same material as that of a flange or port, thereby facilitating welding work and so on for joining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency charged particle accelerator using a quadrupole electrode, and more specifically, ion implantation using a high energy charged particle beam in semiconductor processes, medical care, biotechnology, etc., physical property / composition analysis, and surface. The present invention relates to a high frequency quadrupole accelerator that can be used for reforming and the like.

[0002]

2. Description of the Related Art For example, in order to obtain a high-energy ion beam for performing ion implantation, material analysis, etc., it is composed of four vane electrodes (quadrupole electrodes) as an accelerator utilizing a high frequency electric field. A high-frequency quadrupole accelerator is used, in which the vacuum container itself that also serves as a resonance cavity. This high frequency quadrupole (RFQ: Radio Frequency Quad)
A conventional example of a rupole accelerator is shown in FIG. 3 as a perspective view in a partially broken state. As shown in the figure, the electrodes 1, 2, 3 and 4 forming a quadrupole electrode are arranged in the central axis direction of the casing 5, and the facing surfaces of the electrodes 1, 2, 3 and 4 are uneven. The electrodes are formed in a wavy shape, and the concavo-convex shapes are formed in the same phase in the electrodes facing each other, and the concavo-convex shapes are formed in the opposite phase in the electrodes adjacent to each other. When high frequency power of a predetermined frequency is applied from the input coupler 9 provided in the housing 5 to the cavity formed inside the housing 5 containing the quadrupole electrode thus formed, as shown in FIG. A resonant frequency of TE ₂₁₀ mode is excited in the cavity. At this time,
The same potential is generated at the electrodes facing each other, and the opposite potential is generated at the electrodes adjacent to each other. Therefore, the four electrodes 1,
A quadrupole electric field is generated near the central axis where 2, 3, 4 face each other. In the figure, 6 indicates an electric field and 7 indicates a magnetic field. By forming the electrode structure as described above, the radial electric field strength increases with the displacement from the central axis,
A focusing effect is generated for ions that are accelerated in the central axis position in the axial direction, and the corrugated electrode structure generates an electric field in the axial direction to effectively accelerate the ions. Therefore,
The injected ions are accelerated with a very high efficiency while receiving the focusing force. In the high frequency quadrupole accelerator as shown above, the accelerating tube constitutes a high frequency cavity resonator together with the electrodes 1, 2, 3 and 4, and its resonance frequency (TE ₂₁₀ mode) is in the inner diameter of the housing. Therefore, the strength is required to prevent distortion of the housing. For this reason, the allowable value of the external pressure exerted on the vacuum-exhausted housing and the distortion due to the weight of the accelerator itself must be maintained within ten and several μm. Further, as shown in FIG. 4, the surface current 8 flows on the inner wall of the housing, so that it is necessary to use a material having a small specific electric resistance in order to minimize the energy consumed. In order to meet such requirements, a housing is made of a copper material having a large material thickness or a material obtained by plating copper on carbon steel or the like to reduce power loss while maintaining strength.

[0003]

However, when the housing is made of only copper material, the weight is extremely large when the material thickness is such that strength can be maintained, and it becomes difficult to incorporate it in an ion implantation apparatus or the like. was there. For example, in order to suppress the distortion of the casing within 25 μm, the inner diameter 600 mm × length 1
In the case of a 200 mm case, a wall thickness of 24 mm is required and the weight is about 120 kg. Also, stainless steel, aluminum, etc. are used as general-purpose products for the ports and flanges for attaching the power supply coupler, tuner, etc. to the housing, and in order to join to the housing, they should be vacuum sealed with dissimilar material welding. Therefore, it is required to use a special welding method such as electron beam welding, and there is a problem that labor and cost increase. On the other hand, in order to eliminate the problems of constructing the housing with only copper material as described above, copper is plated on the inner surface of carbon steel or the like, which has excellent strength, to obtain strength with a thin material thickness and the inner wall. The configuration of the plating material that suppresses the power loss due to the surface current makes it difficult for the local projections to be generated by the plating, so the cost and work required to finish the plated surface with high smoothness (about 1 to 2 s),
There was a problem that time was an obstacle. The present invention has been made in view of the conventional problems as described above, and uses a material having excellent strength as a main constituent material of the housing to maintain the strength, while the inner wall portion of the housing has a small specific electric resistance. An object of the present invention is to provide a high frequency quadrupole accelerator that can suppress power loss by using materials.

[0004]

In order to achieve the above-mentioned object, the means adopted by the present invention is to arrange a quadrupole electrode in the central axis direction inside a cylindrical casing forming a resonance cavity, A high-frequency quadrupole that accelerates charged particles injected between the quadrupole electrodes by an electric field generated between the quadrupole electrodes by supplying and exciting high-frequency power having a resonance frequency of the housing into the housing. In the accelerator, the tubular body forming the casing is
A high-frequency quadrupole accelerator characterized in that it is composed of a clad material composed of a material having a low specific electric resistance on the inner surface and a material having excellent mechanical strength on the outer surface. The joint welding line of the tubular body formed of the clad material is formed in parallel with the central axis direction of the housing, and is formed on the supporting central axis line of the quadrupole electrode in which the joint welding line is arranged in the orthogonal direction. To be done.

[0005]

According to the present invention, the cylindrical body forming the housing is made of a clad material such as explosive deposition so that the inner surface can be made of a material having low specific electric resistance and the outer surface can be made of a material having excellent mechanical strength. To do. By using a clad material made of such a heterogeneous material, the inner surface of the housing is made of a material (copper, etc.) with a thin material thickness and a low thickness required for the surface current flowing through the inner wall. Since most of the material thickness can be formed of a material with excellent mechanical strength (stainless steel, etc.), it is possible to reduce the material thickness to obtain the same strength and to reduce the weight of the accelerator. it can. For example, under the same conditions as in the case of using only the copper material shown above, the weight becomes about 1/2 when formed by the explosive cladding material of the copper material and the stainless steel material. This weight reduction reduces the strength constraint and facilitates the incorporation into an ion implanter or the like, which also contributes to weight reduction of the ion implanter itself.
In addition, the cost can be reduced to about 1/2. Further, since the outer surface of the housing is formed of the same material as the flange and the port, welding for joining can be easily performed.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. still,
The following examples are examples of embodying the present invention and do not limit the technical scope of the present invention. Figure 1
2A is a side view and FIG. 2B is a side view of the high frequency quadrupole accelerator according to the first embodiment of the present invention. FIG. 2 is a side view of the high frequency quadrupole accelerator according to the second embodiment of the present invention. It is (a) and sectional drawing (b). In FIG. 1 (a), a cylindrical casing 12 forming a resonance cavity of the high frequency quadrupole accelerator 10 has a lid 13 on flanges 12a and 12b provided at both ends thereof.
The inside of the housing 12 can be vacuum-sealed by attaching the housing 14. As shown in FIG. 1B, the quadrupole electrode 1 in which the electrodes facing each other in the housing 12 are arranged in the orthogonal direction 1,
2, 3, 4 are arranged in the direction of the central axis 11. In order to make the high-frequency quadrupole accelerator 10 function, the lid 13 includes an ion source 15 for injecting an ion beam in the direction of the central axis 11 of the housing 12, and a vacuum pump for evacuating the inside of the housing 12. A vacuum exhaust port 16 for connection is provided, and the housing 12
A power input port 19 having an input coupler for supplying high frequency power, a monitor port 17 for monitoring the resonance frequency, and a tuning port 18 to which a frequency adjusting device for adjusting the resonance frequency is connected. Is provided. As shown in FIG. 1B, the housing 12 is formed of a clad material made of stainless steel s on the outer surface and copper c on the inner surface. In this embodiment, in order to form the housing 12 having an inner diameter of 600 mm and a length of 1200 mm, a stainless steel material (SUS3
04) s and copper (OFHC) c having a material thickness of 2 mm are used as the explosive cladding material. The total weight at this time is about 60 kg, which is about 1/2 of the total weight compared with the case where only a copper material having a material thickness for obtaining equivalent strength is formed. In order to form the cylindrical casing 12 with the clad material formed in this way, the clad material is formed into a cylindrical shape with the copper material surface inside, and the joining line 20 is welded in the direction of the central axis 11. Quadrupole electrodes 1, 2,
When attaching 3 and 4, the welding line position welded as shown in FIG. 1 (b) is used as the supporting position for any one of the quadrupole electrodes 1 to 4. By arranging the quadrupole electrodes 1 to 4 in this manner, the surface current 8 flowing through the inner wall of the housing 12
Since the joining line 20 does not intervene in the flow path (see FIG. 4), the welding current does not cause a loss in the surface current flowing through the copper c portion having a low specific electric resistance, and efficient acceleration performance can be maintained. ..

As described above, the housing 12 is provided with the monitor port 17, the tuning port 18, the power input port 19, and the flanges 12a and 12b for attaching the lids 13 and 14, however, it is a general-purpose product. Even if each port or flange made of stainless steel is used, the material can be matched with the stainless steel s that is the outer surface material of the housing 12, and the vacuum sealing can be easily performed without using a special welding method such as welding of dissimilar materials. Welding can be performed. Next, a second embodiment of the present invention shown in FIG. 2 will be described. The present embodiment is a high frequency quadrupole accelerator having a rectangular cross section. The same parts as those of the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. The housing 21 according to the present embodiment is formed in a rectangular cross-sectional shape as shown in a cross-sectional view in FIG. 2B, and has a copper material (OFHC-2 mm) c on the inner surface and a stainless steel material (SUS304) on the outer surface. -10 mm) s is used as an adhering clad material at four bonding lines 22, 22, 2 parallel to the central axis 11.
It is formed by welding 2 and 22. Each of the joining lines 22
Are all quadrupole electrodes 1, 2, 3, as shown in the figure.
4 is the same as the support position. Therefore, the joining line does not intervene in the flow path of the surface current flowing through the copper material c portion of the inner wall of the housing 21, the surface current is not given a loss due to the welded portion, and efficient acceleration performance can be maintained. .. 2 above
By configuring as shown in the example of the example, the distortion of the casing due to the external pressure (1 kgf / cm ² ) applied to the evacuated casing and the weight of the accelerator itself is suppressed to within a dozen μm. Has been. In addition, the total weight (about 60
(kg) has reduced the restrictions on incorporation into an ion implanter, etc., and has made the ion implanter itself lighter.
In addition, the manufacturing cost of the housing has been reduced to about half that of copper only.

[0008]

As described above, according to the present invention, the tubular body forming the housing is clad so that it can be formed of a material having a low specific electric resistance on the inner surface and a material having excellent mechanical strength on the outer surface. By using a material, the power loss can be suppressed by a copper material that has a low specific electric resistance against the surface current flowing on the inner wall of the housing, and most of the material thickness is excellent in mechanical strength. Since it can be made of (stainless steel),
The material thickness can be kept low to obtain the same strength,
The weight of the accelerator is significantly reduced. This weight reduction reduces the strength constraint and facilitates the incorporation into an ion implanter or the like, which also contributes to weight reduction of the ion implanter itself. Also, in terms of cost, it can be reduced to about half that in the case where only copper material is used. Furthermore, since the outer surface of the housing is made of the same material as the flange and port,
There is an effect that welding or the like for joining is easily performed.

[Brief description of drawings]

FIG. 1 is a side view (a) and a sectional view (b) showing a configuration of a high frequency quadrupole accelerator according to a first embodiment of the present invention.

FIG. 2 is a side view (a) and a sectional view (b) showing a configuration of a high frequency quadrupole accelerator according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration of a high frequency quadrupole accelerator.

FIG. 4 TE ₂₁₀ in an accelerating cavity with a quadrupole electrode.
Explanatory drawing which shows the mode of excitation of the resonant frequency of a mode.

[Explanation of symbols]

 1, 2, 3, 4--Quadrupole electrode 10,23-High-frequency quadrupole accelerator 11-Center axis 12,21-Housing 20,22-Joint line (welding line) c-- Copper material of clad material s─Stainless steel material of clad material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Suzuki 1-1-1, Migatadai, Nishi-ku, Kobe (72) Inventor Hirofumi Imanaka 1-1-1, Migatadai, Nishi-ku, Kobe

Claims (2)

[Claims] 1. A quadrupole electrode is arranged in a central axis direction inside a cylindrical casing forming a resonance cavity, and high-frequency power having a resonance frequency of the casing is supplied into the casing for excitation. In a high-frequency quadrupole accelerator for accelerating charged particles injected between the quadrupole electrodes by an electric field generated between the quadrupole electrodes, the cylindrical body forming the casing is A high-frequency quadrupole accelerator, which is composed of a clad material composed of a material having low resistance and a material having excellent mechanical strength on the outer surface side. 2. A joint welding line of a tubular body formed of the clad material is formed parallel to the central axis direction of the casing, and
The high frequency quadrupole accelerator according to claim 1, wherein the high frequency quadrupole accelerator is formed on a support center axis of the quadrupole electrodes arranged in the orthogonal direction.