JPH08273899A - High-frequency quadrupole accelerator - Google Patents

Abstract

PURPOSE: To provide an RFQ accelerator constituting a resonance frequency variable structure by changing the inductance of an resonance circuit formed in a resonance cavity. CONSTITUTION: An L adjustment conductor 7 is provided in a space forming the inductance of a high frequency quadrupole accelerator 10 equipped with the internal resonance circuit of the inductance and a capacitance formed in a resonance cavity 16. The length or the position of the L adjustment conductor 7 is disposed in the center axis direction of the resonance cavity 16 so as to be adjustable. When a conductive body exists in the space forming the inductance in the resonance cavity 16, the cross-sectional area of the coil forming the inductance becomes small so that the inductance becomes small. Therefore, when the length of the L adjustment conductor 7 is changed, the degree of effect on the inductance change is changed so that the resonance frequency of the internal resonance circuit can be changed. Accordingly, the resonance frequency of the high frequency quadrupole accelerator 10 is changed so as to be adapted to the kind of accelerated charged particles, and at the same time the acceleration energy can be changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle accelerator used in the fields of semiconductor processing, medical treatment, biotechnology and the like, and more specifically, it accelerates charged particles into a high energy beam by a high frequency quadrupole electrode. , Ion implantation, composition analysis,
The present invention relates to a high-frequency quadrupole accelerator used for surface modification and the like.

[0002]

2. Description of the Related Art The high frequency quadrupole accelerator is configured to accelerate charged particles, which are injected between four vane electrodes (quadrupole electrodes) which generate a high frequency electric field, by the high frequency electric field. It is an accelerator. This high frequency quadrupole (Radi
A conventional technique of a frequency quadrupole (according to an RFQ accelerator) will be described below. FIG.
In the RFQ accelerator 50 shown in FIG. 0, electrodes 1, 2, 3, 4 forming a quadrupole electrode are arranged in the central axis direction of an acceleration cavity 5 formed by a cylindrical metal housing. 2, 3,
Reference numeral 4 indicates that the surfaces facing each other are corrugated in an uneven shape, and the electrodes facing each other have the uneven shapes formed in the same phase, and the electrodes adjacent to each other have the uneven shapes formed in the opposite phase. . When a high-frequency voltage of the same phase is applied to the electrodes facing each other and the opposite phase is applied to the electrodes adjacent to each other, the four electrodes 1, 2, 3, 4 face each other. A quadrupole electric field is generated near the central axis. Furthermore, since the concavo-convex shapes of the electrodes 1, 2, 3 and 4 are vertically and horizontally shifted by 180 degrees, for example, when the electrodes 1 and 3 are positive and the electrodes 2 and 4 are negative, on the central axis. An electric field is generated in the axial direction. When the voltage polarities of the electrodes 1, 2, 3, 4 are reversed, the direction of this electric field is also reversed. The RFQ accelerator 50
Considering the case of accelerating an ion, which is a type of charged particle, due to , The energy is monotonically increased each time the electrodes 1, 2, 3 and 4 pass through the uneven portions. On the other hand, the ions that first enter the phase that undergoes deceleration are gradually bunched into the subsequent ions at the time of the next acceleration electric field, and are then monotonically accelerated. In addition, since the strong high-frequency electric field existing in the plane orthogonal to the axis produces a strong focusing force in the vertical and horizontal directions, the ions can be accelerated with a very high transmittance.

However, in the RFQ accelerator 50 configured as described above, since the resonance frequency of the acceleration cavity 5 is fixed, the ion species that can be accelerated are limited and the acceleration energy is also determined. Therefore, when such an RFQ accelerator is used for ion implantation into a semiconductor, it is necessary to provide a structure capable of changing the resonance frequency according to the ion species and the acquired energy. As a variable structure of this resonance frequency, there is known a method of providing a resonance circuit 48 outside the acceleration cavity 47 as shown in FIG. 11 (Japanese Patent Laid-Open No. 60-11).
5199, JP-A-3-245499, etc.). By changing the inductance or capacitance of the external resonance circuit, these realize an RFQ accelerator with variable resonance frequency. However, since the external resonance circuit is highly susceptible to a decrease in Q value and external disturbance, various methods of forming a resonance circuit in the acceleration cavity have been proposed to solve this. In order to configure a resonance circuit in the acceleration cavity and realize a configuration in which the resonance frequency can be changed, it is necessary to change the inductance and / or the capacitance of the internal resonance circuit. For example, as the prior arts in which the inductance of the internal resonance circuit is variable, the configurations shown in JP-A-63-228598, JP-A-5-21199, and JP-A-5-82298 are known.
For example, as shown in FIG. 12, the configuration disclosed in Japanese Patent Laid-Open No. 5-211199 has electrodes 1 and 3 and electrodes 2 and 4 constituting a quadrupole electrode arranged in a vacuum container 43, respectively. A one-turn coil (inductance) is formed by the connected parallel conductors 40 and 41 and the short-circuit conductor 42 that short-circuits the parallel conductors 40 and 41. By moving the position of the short-circuit conductor 42, the cross-sectional area of the one-turn coil changes and the inductance can be changed. Further, the configuration disclosed in Japanese Patent Laid-Open No. 63-228598 has a quadrupole electrode 1 as shown in FIG.
The resonance cavity 44 itself in which 2, 3, 4 are arranged has a deformable structure. The diameter of the resonance cavity 44 is changed by driving the moving rods 45, 45 ... Attached to the resonance cavity 44, so that the inductance formed by the quadrupole electrodes 1, 2, 3, 4 and the resonance cavity 44 is changed. .

[0004]

It is not easy to implement the resonance frequency of the internal resonance circuit in the RFQ accelerator with a stable structure without lowering the Q value. Impractical due to deterioration and structural defects. More specifically, in the configuration shown in FIG. 12, the high frequency resistance increases and the Q value decreases at the contact point between the short-circuit conductor 42 and the parallel conductors 40 and 41, and the parallel conductors formed in a large number of rods are used. There is a problem that the movement of the short-circuit conductor 42 is likely to be hindered by the slight distortion of either 40 or 41. Further, in the configuration shown in FIG. 13, it is not possible to make the resonant cavity 44 to be evacuated into a deformable structure in terms of strength, and the corrugated structure for deforming leads to an increase in high-frequency resistance and a Q value There is a problem that it decreases. By constructing the internal resonant circuit in the RFQ accelerator and making the resonant frequency variable as described above, it can be effectively used for ion implantation etc. using the RFQ accelerator, but the performance is degraded. In order to realize without, there were many problems in the prior art. Therefore, an object of the present invention is to provide an RFQ accelerating device having a variable resonance frequency structure by a structure that can change the inductance of a resonance circuit formed in a resonance cavity without lowering the Q value. .

[0005]

In order to achieve the above object, the means adopted by the present invention is to arrange a quadrupole electrode in the direction of the central axis of a resonance cavity formed in a cylindrical shape, and A charged particle beam incident on the central axis of the quadrupole electrode by forming an internal resonance circuit by forming an inductance and a capacitance therein and introducing high frequency power into the resonance cavity to resonate the resonance cavity. In a high-frequency quadrupole accelerator for accelerating a magnetic field, a conductor whose length or position in the central axis direction of the resonant cavity can be adjusted is arranged in a space forming the inductance in the resonant cavity. It is configured as a high frequency quadrupole accelerator.
In the above structure, a plurality of the conductors may be arranged in the resonance cavity.

[0006]

According to the present invention, the conductor is arranged in the space for forming the inductance of the high-frequency quadrupole accelerator having the internal resonance circuit in which the inductance and the capacitance are formed in the resonance cavity. The length or position of the conductor is arranged so as to be adjustable in the central axis direction of the resonance cavity. When a conductor is present in the space that forms the inductance in the resonance cavity, the cross-sectional area of the coil that forms the inductance equivalently becomes smaller and the inductance becomes smaller. When the length of this conductor is changed, the degree of influence on the change in inductance is changed, so that the resonance frequency of the internal resonance circuit can be changed, and the resonance frequency of the high-frequency quadrupole accelerator can be changed to accelerate the acceleration of charged particles. The acceleration energy can be changed at the same time as the type is adapted. Also, by changing the arrangement position of the conductors, the conductors are arranged at different magnetic flux densities in the space forming the inductance, and the degree of influence on the inductance change can be changed. It is possible to give the same effect as changing the length. The above conductor does not form the inductance component of the internal resonance circuit, but changes the degree of influence on the formation of the inductance component.
An increase in high-frequency resistance is suppressed, and a high-frequency quadrupole accelerator capable of adjusting the resonance frequency without reducing the Q value is realized. A number of conductors corresponding to the range of resonance frequency change can be arranged in the resonance cavity.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. still,
The following example is an example embodying the present invention and does not limit the technical scope of the present invention. Figure 1
1 is a side view showing a structure of an RFQ accelerator according to a first embodiment of the present invention (a) and a sectional view taken along the line AA of FIG. 3 and 4 are perspective views of the L adjusting conductor according to the first embodiment, FIGS.
FIG. 6 is a side view (a) showing another aspect of the configuration of the first embodiment and a sectional view (b) taken along the line AA of FIG. 7, and FIG. 7 shows the configuration of the RFQ accelerator according to the second embodiment of the present invention. A side view (a) and a sectional view taken along the line AA (b) of FIG.
FIG. 9 is a perspective view showing the configuration of the adjusting conductor, and FIG. 9 is a side view (a) showing another aspect of the configuration of the second embodiment and a sectional view (b) taken along the line AA of FIG. In FIG. 1, an RFQ accelerator 10 according to an embodiment is configured as an ion accelerator, and electrodes 11, 13 forming a quadrupole electrode are arranged in the central axis direction of a cylindrical metal casing 16 forming a resonance cavity. And electrodes 12 and 14 are arranged to face each other in a cross direction. Each electrode 1
Electrodes 11, 13 and electrode fixtures 21 are provided on electrode fixtures 21a alternately arranged in the central axis direction.
The electrodes 12 and 14 are respectively supported by b. As shown in FIG. 2, the electrode supporting members 21a and 21b are provided with a metal housing 16a.
Are supported by bifurcated plate electrodes 22a and 22b fixed above and below, respectively, and the plate electrode 22a is provided in the central space formed by the bifurcated shape of the plate electrodes 22a and 22b.
The intermediate electrode 23a is arranged from the side, and the intermediate electrode 23b is arranged from the plate electrode 22b side.

With the above structure, the flat plate electrode 22a and the intermediate electrode 23b, and the flat plate electrode 22b and the intermediate electrode 2 are provided inside the metal casing 16 forming the resonance cavity as shown in FIG. 1 (b).
A capacitance is formed due to the close contact with 3a, and an inductance is formed due to the two left and right one-turn coils formed by the plate electrode 22a, the metal casing 16, and the plate electrode 22b, and internal resonance occurs in the resonance cavity. The circuit is constructed. By changing the inductance of the internal resonance circuit in the above configuration, the RFQ
The resonance frequency of the accelerator 10 can be changed and adapted to the accelerating ion species to accelerate to an arbitrary energy. An example configuration for changing the inductance will be described below. As shown in FIG. 1B, the configuration of the first embodiment of the above-mentioned inductance change is such that the L adjusting conductor (conductor) 7 is placed in the inductance forming space L ₁ L ₂ in the resonance cavity.
a and 7b are arranged. The L adjustment conductor 7
The a and 7b are formed as shown in the perspective view of FIG. As shown in FIG.
The entire length can be expanded / contracted by inserting / removing 9 and 19. The L adjusting conductor 7 is made of oxygen-free copper in order to suppress an increase in high frequency resistance, but aluminum or the like can be used. As shown in FIG. 1, the L adjusting conductor 7 is electrically insulated from the inductance forming material (the metal casing 16 and the plate electrode 22b) by the insulator 15 at the center position of the metal casing 16 in the central axis direction. Fixed. Although the structure for moving the movable conductors 19, 19 in and out to adjust the length is omitted, it can be operated by equipping the inside of the cylindrical body with a motor or the like for driving the movable conductors 19, 19.

By disposing the L adjusting conductors 7a and 7b in the inductance forming spaces L ₁ and L ₂ as described above, the cross-sectional area of the _one- turn coil formed by each of the inductance forming spaces L ₁ and L ₂ is reduced. Change. The inductance L of the one-turn coil is L = μS, where μ is the permeability of the vacuum and S is the cross-sectional area of the one-turn coil.
Indicated by. When the L adjusting conductor 7 is arranged in this one-turn coil, the cross-sectional area S is equivalently reduced and the inductance L changes. When the length of the L adjusting conductor 7 is changed, the cross-sectional area S is changed, so that the inductance L can be changed. Therefore, by adjusting the length of the L adjusting conductor 7, the inductance of the internal resonance circuit can be changed, and the resonance frequency of the RFQ accelerator 10 can be changed. Therefore, the ion species to be accelerated can be accelerated with arbitrary energy. You can The RFQ accelerator 1
The resonance frequency of 0 is adjusted by arranging a plurality of L adjustment conductors 7 in the inductance forming spaces L ₁ and L ₂ according to the adjustment range, as shown in FIGS. 4, 5 and 6. can do. In the configuration shown in FIG. 4, the L adjustment conductors 7 are arranged above and below the inductance forming spaces L ₁ and L ₂ , respectively, and a total of four L adjustment conductors 7a, 7b, 7c,
7d is used. Further, in the configuration shown in FIG. 5, the L adjustment conductors 7 are symmetrically arranged in the central axis direction of the inductance forming spaces L ₁ and L ₂ , and a total of four L adjustment conductors 7a and 7 are provided.
b, 7c, 7d are used. Further, in the configuration shown in FIG. 6, the L adjustment conductor 7 has the inductance forming space L ₁ ,
They are symmetrically arranged up and down and the center axis of the L _2, a total of eight L adjusting conductor 7a~7h is used. As shown in FIG. 7B, the configuration of the second embodiment of the above-mentioned inductance change is such that the inductance forming space L ₁ L ₂ in the resonance cavity is
The L adjusting conductors (conductors) 8a and 8b are arranged. The L adjusting conductor 8 is a cylindrical body made of oxygen-free copper as shown in the perspective view of FIG. 8, and is arranged in the central axis direction of the metal casing 16 as shown in FIG. 7A. The position can be freely moved. The L adjusting conductor 8 is electrically insulated from the inductance forming material (the metal casing 16 and the plate electrode 22b) by the insulator 15 by the insulator 15, and is arranged so as to be movable in the predetermined distance range in the central axis direction. It Although the structure for moving the L adjusting conductor 8 is omitted, it is possible to move the L adjusting conductor 8 on a rail (not shown) by installing a motor or the like inside the tubular body.

With the above configuration, the inductance L can be changed by changing the cross-sectional area of the one-turn coil formed by the inductance forming spaces L ₁ and L ₂ . Since the magnetic flux density is higher toward both ends of the metal housing 16 shown in FIG. 7A, the degree of change in the inductance increases as the L adjustment conductors 8a and 8b are moved toward the ends. Therefore, by adjusting the position of the L adjusting conductor 8, the inductance of the internal resonance circuit can be changed, and the resonance frequency of the RFQ accelerator 10 can be changed. Therefore, the ion species to be accelerated can be accelerated with arbitrary energy. You can The arrangement for adjusting the resonance frequency of the RFQ accelerator 10 by changing the arrangement position of the L adjustment conductor 8 in the metal housing 16 can be configured as shown in FIG. 9 according to the adjustment range. In the configuration shown in FIG. 9, the L adjusting conductors 8 are symmetrically arranged on the left and right sides of the inductance forming spaces L ₁ and L ₂ , and a total of four L adjusting conductors 8a, 8b, 8 are provided.
The positions c and 8d can be moved. In the configurations of the respective embodiments described above, the L adjusting conductor 7 or 8 does not form the inductance component of the internal resonance circuit but changes the degree of influence on the formation of the inductance component. The inductance of the internal resonant circuit can be changed without causing a decrease in the value.

[0011]

As described above, according to the present invention, in the space for forming the inductance of the high frequency quadrupole accelerator having the internal resonance circuit having the inductance and the capacitance formed in the resonance cavity. A conductor is disposed on the. The length or position of the conductor is arranged so as to be adjustable in the central axis direction of the resonance cavity. When a conductor is present in the space that forms the inductance in the resonant cavity,
The cross-sectional area of the coil that equivalently forms the inductance becomes smaller, and the inductance becomes smaller. When the length of this conductor is changed, the degree of influence on the change in inductance is changed, so that the resonance frequency of the internal resonance circuit can be changed, and the resonance frequency of the high-frequency quadrupole accelerator can be changed to accelerate the acceleration of charged particles. The acceleration energy can be changed at the same time as the type is adapted. Also, by changing the arrangement position of the conductors, the conductors are arranged at different magnetic flux densities in the space forming the inductance, and the degree of influence on the inductance change can be changed. It is possible to give the same effect as changing the length. Since the conductor does not form the inductance component of the internal resonance circuit but changes the degree of influence on the formation of the inductance component, the increase of the high frequency resistance is suppressed, and the resonance frequency can be adjusted without decreasing the Q value. A heavy pole accelerator is realized.

[Brief description of drawings]

FIG. 1 is a side view (a) showing a structure of an RFQ accelerator according to a first embodiment of the present invention and a sectional view (b) taken along the line AA.

FIG. 2 is a perspective view showing an electrode structure of an RFQ accelerator according to an embodiment.

FIG. 3 is a perspective view showing a configuration of an L adjustment conductor according to the first embodiment.

FIG. 4 is a side view (a) showing a variation of the structure of the first embodiment and a sectional view (b) taken along the line AA of FIG.

[FIG. 5] Same as above

FIG. 6 Same as above

FIG. 7 is a side view (a) showing a structure of an RFQ accelerator according to a second embodiment of the present invention and a sectional view (b) taken along the line AA.

FIG. 8 is a perspective view showing a configuration of an L adjustment conductor according to a second embodiment.

FIG. 9 is a side view (a) showing a variation of the structure of the second embodiment and a sectional view (b) taken along the line AA of FIG.

FIG. 10 is a perspective view showing a basic configuration of an RFQ accelerator.

FIG. 11 is a circuit diagram showing a configuration in which a resonance frequency is variable by an external resonance circuit.

FIG. 12 is a perspective view showing the configuration of a conventional example of an RFQ accelerator having a variable resonance frequency.

FIG. 13 Same as above

[Explanation of symbols]

7, 8 ... L adjusting conductor (conductor) 10, 30-34 ... RFQ accelerator (high-frequency quadrupole accelerator) 11, 12, 13, 14 ... Quadrupole electrode 16 ... Metal casing (resonant cavity) L ₁ , L ₂ ... Inductance forming space

Claims (2)

[Claims] 1. An internal resonance circuit is formed by arranging a quadrupole electrode in a central axis direction of a cylindrical resonance cavity and forming an inductance and a capacitance in the resonance cavity to form an internal resonance circuit. In a high-frequency quadrupole accelerator that resonates the resonant cavity by introducing high-frequency power into the cavity and accelerates the charged particle beam incident on the central axis of the quadrupole electrode, the inductance in the resonant cavity is A high-frequency quadrupole accelerator characterized in that a conductor whose length or position in the central axis direction of the resonance cavity can be adjusted is provided in the space formed. 2. The high frequency quadrupole accelerator according to claim 1, wherein a plurality of said conductors are arranged in a resonance cavity.