JP3356494B2 - High frequency multipole accelerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency multipole accelerator for accelerating an ion beam used in industrial applications such as research on elementary particles, atomic nuclei, physical properties and the like, material modification, medical irradiation and the like.

[0002]

2. Description of the Related Art As a high-frequency multipole accelerator, for example, there is a high-frequency quadrupole accelerator (hereinafter referred to as RFQ) having four electrodes as shown in FIG. In this high-frequency quadrupole linear accelerator, four electrodes 1 which are long in the axial direction are provided at 90 ° intervals in a cylindrical hollow tube 7 as shown in FIG. In this case, one edge of each electrode 1 is arranged toward the center of the cavity. In addition, a wavy curved surface is formed at the edge of each electrode 1 in the axial direction.

On the other hand, the ion beam 14 to be accelerated
Is incident on the center of the cavity of the cavity tube 7 and is accelerated in the axial direction. At this time, a quadrupole electric field 15 is generated at the center of the cavity by the four electrodes 1 as shown in FIG.
4 undergoes a contracting action. Since the electrode 1 forms a wave-shaped curved surface in the axial direction, the electric field 15 spreads in the axial direction and is accelerated in the axial direction at the same time.

FIG. 6 schematically shows how the ion beam is accelerated while being affected at each position of the electrode. In FIG. 6, no waveform is formed in the radial matching section 2 of the electrode 1, and the distance between the electrodes 1 gradually decreases. In this portion, the quadrupole electric field 15 is gradually increased, and the ion beam 14 is gradually focused and shaped so that the beam can be received after the radial matching section 2.

[0005] After passing through the radial matching section 2, the ion beam 14 shaped in the radial direction enters the bunching section 3. In this portion, the difference between the peaks and valleys of the waveform gradually increases, and the electric field component in the axial direction gradually increases accordingly. Due to the electric field component in the axial direction, the ion beam 14 which has been DC-like is gradually bunched and undergoes a slight acceleration. This batching section 3
Are sometimes referred to as shapers, pre-bunchers, and bunchers.

A well-bunched ion beam 14
Is accelerated to the target energy in the next acceleration unit (accelerator) 4. In this part, the peaks and valleys of the waveform of electrode 1
The difference is almost common that constant across, and stable ion motion. Usually, the length occupied by the accelerator 4 is the longest.

The RFQ has an excellent characteristic that it can accelerate with a beam transmittance close to 100% with respect to the ion beam incident as a direct current in this way. From the above, it is clear that the characteristics of the RFQ , the position and shape of the waveform curved surface of the electrode 1, greatly depend on the accuracy of the position and shape of the waveform curved surface of the electrode 1.

Next, the processing of the electrode curved surface will be described with reference to FIG. As the cross-sectional shape of the edge of the electrode 1, the radius R of this edge is equal to the distance X between the center 5 of the hollow tube and the edge of the electrode 1.
It is known that if processed so that the electric field between the electrodes 1 has a distribution close to the theoretical requirement, sufficient performance can be obtained. That is, the radius of the edge differs in each cross section of the electrode. In order to obtain such a shape, as shown in FIG. 7A, the processing is performed by moving the processing blade (end mill) 17 three-dimensionally.
Dimensional processing is required.

In such a machining method, unless the axially moving pitch of the end mill 17 is made sufficiently small, not only an accurate shape cannot be obtained, but also fine projections are formed on the machined surface, which may cause electric discharge. For this reason, a very long processing time is required, and the cost is high.

On the other hand, as shown in FIG. 7 (b), a method called two-dimensional processing is used in which the edge of the electrode 1 is processed by moving the stepping blade 18 along an axial waveform. There is also. In this case, the radius R of the edge of the electrode 1 is equal in each section of the electrode 1. Although the processing time is significantly shorter than that of the three-dimensional processing, it is inevitable that the error component of the electric field for convergence and acceleration increases.

In the radial matching section 2 in particular, the electric field distribution is significantly different from the originally required quadrupole electric field 15, and the formation of the ion beam 14 becomes insufficient, which may cause the ion beam 14 to be lost. In addition, the bunching section 3 is also a part that is apt to lose the ion beam 14 from the beginning, and the beam transmittance may be greatly reduced due to the influence of the error electric field.

Next, how to attach four electrodes will be described with reference to FIG. FIG. 8 shows an example of a mounting portion between the electrode 1 and the hollow tube 7. The electrode 1 is fixed to a mounting flange 19 mounted on the hollow tube 7. The mounting flange 19 is provided with a cooling water passage 23 to the electrode 1.

In this case, an O-ring 20 made of rubber or metal is inserted into the contact surface between the hollow tube 7 and the mounting flange 19 and the contact surface between the electrode 1 and the mounting flange 19 to maintain the inside of the hollow tube at a vacuum. I have.

A gap between the electrode 1 and the hollow tube 7 is R
An F contactor 21 is provided so that an RF current 16 between the electrode 1 and the hollow tube 7 flows without resistance. Further, a thin adjustment plate (shim) 22 is inserted between the contact surface between the hollow tube 7 and the mounting flange 19 to adjust the position of the edge of the electrode 1.

As described above, since a single RFQ has a plurality of complicated electrode mounting portions, there is a possibility that vacuum leakage, water leakage, defects such as electric discharge and heat generation due to RF contact failure may occur, and reliability may be reduced. There was a problem in terms. Adjustment plate 2
2, it is very difficult to set the position of the edge of the electrode 1 with the required accuracy (typically ± 50 μm), the required accuracy cannot be obtained, the error electric field increases, and the ion beam 1
4 caused a decrease in transmittance.

[0016]

There is a problem that the processing time carried out in three-dimensional processing To maximize INVENTION Problems to be Solved] above the electrode edge between waveform processing RFQ performance RFQ becomes very long. On the other hand, when the two-dimensional processing is performed, the processing time is shortened, but there is a possibility that the beam transmittance, which is a feature of the RFQ, is reduced. On the other hand, attempts have been made to adjust the waveform depth to prevent the beam transmittance from lowering, but it has not been sufficiently effective, and there has been no measure against the error electric field especially in the radial matching section. .

Further, since many flanges, O-rings, and RF contacts are used in the electrode mounting portion,
Lack of reliability has made it difficult to adjust the positions of the electrode edges. The present invention has been made in view of the above circumstances, and has a high beam transmittance that facilitates processing of an electrode, shortens a period required for manufacturing, and facilitates position adjustment of an electrode. It is an object of the present invention to provide a high-frequency multipole accelerator having high reliability.

[0018]

According to the present invention, in order to achieve the above object, a high-frequency multipole accelerator is constituted by the following means. (1) In a high-frequency multipole accelerator having a cylindrical hollow tube and a plurality of sets of electrodes for accelerating particles in the hollow tube having a tip shape formed in a waveform along the axial direction of the hollow tube, the empty one radial matching section or bunching section of the beam incident portion as a tip shape of the electrode, or by a three-dimensional processing all or part of the radial matching section and bunching section
Distance from center of sinus canal to electrode edge and radius of electrode edge
And the radial matching
Do not perform 3D machining in the section and bunching section.
Part and accelerator part by two-dimensional processing
The electrode is formed such that the radius of the edge is constant . (2) In the configuration of the above (1), the electrodes provided in the hollow tube are mounted via bellows on both edges of a plurality of axially extending openings provided in the hollow tube corresponding to the respective electrode mounting positions. . (3) In the configuration of the above (2), an electrode position adjusting mechanism capable of adjusting the position of the electrode in the horizontal direction, adjusting the position in the vertical direction, and adjusting the position in the beam axis direction is provided at the mounting end of the electrode.

[0019]

In the high-frequency multipole accelerator configured as described in the above (1), the radial matching section and the bunching section, which strongly affect the beam transmittance, can have a waveform with a small error electric field. Since the processing of the accelerating portion occupying most of the longitudinal direction of the electrode is performed by two-dimensional processing, the processing of the electrode is facilitated and the period required for manufacturing can be shortened.

Further, in the high-frequency multipole accelerator having the configuration (2), it is not necessary to mount components such as an O-ring and an RF contact in order to mount an electrode in the hollow tube. Problems such as discharge and heat generation due to water leakage and RF contact failure are eliminated.

Further, in the high-frequency multipole accelerator having the structure as described in (3) above, the electrode position adjusting function easily and accurately adjusts the position of the electrode tip, which strongly affects the beam transmittance. be able to.

[0022]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an RFQ similar to that of a conventional example as a high-frequency multipole accelerator according to the present invention. In FIG. 1, the radial matching section 2 and the bunching section 3 of the electrode 1 are three-dimensionally processed,
-In the A section, the BB section, the CC section, and the DD section, the distance x from the center 5 of the hollow tube 7 to the edge of the electrode 1 and the radius R of the edge of the electrode 1 become equal. I have.

On the other hand, since the accelerator 4 is processed two-dimensionally, the radius R of the edge of the electrode 1 in the EE section and the FF section becomes a certain constant value R ₀ . According to this embodiment, an ideal electric field distribution can be obtained in the radial matching section 2 and the bunching section 3 which strongly influence the transmittance of the ion beam 14, while the accelerator occupying a large part of the entire length of the electrode 1. The time required for manufacturing the four parts can be reduced.

As described above, in this embodiment, the ion beam 1
RFQ with a short production period while keeping the transmittance of 4 high
Can be obtained. In the above embodiment, the same effect can be expected even if the radial matching section 2 or only the bunching section 3 is configured to be three-dimensionally processed. It is also conceivable to partially process the bunching section 3 three-dimensionally.

Next, another embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2A, the hollow tube 7 is usually made of iron, and its inner surface is plated with copper. On the other hand, the electrode 1 is usually made of copper, and a stainless steel welding seat 8 is attached to its mounting end side by brazing or diffusion bonding.

A welding seat 8 attached to the electrode 1 is attached to a plurality of openings extending in the axial direction provided in the hollow tube 7 through a race track-shaped, for example, stainless steel bellows 6.

In this case, the portions of the bellows 6 and the welding seat 8 facing the inside of the hollow pipe 7 are each plated with copper, and the bellows 6 are attached to the opening side edge of the hollow pipe 7 and the welding seat 8, respectively. The electrode 1 is attached to the hollow tube 7 by welding.

On the other hand, an electrode position adjusting mechanism 9 as shown in FIG. 2B is provided at a plurality of locations (two locations in the axial direction in the figure) on the outer peripheral side of the hollow tube 7 corresponding to the mounting end of the electrode 1. ing. The electrode position adjusting mechanism 9 includes a push seat 10, a horizontal adjustment bolt 11 for adjusting the push seat 10 in the horizontal direction, an axial push bolt 12 for adjusting the axial direction, and a straddle extending in the width direction of the opening of the hollow tube 7. Up / Down Adjustment and Lock Bolt 1 for Adjusting the Electrode 1 Up and Down via a Contact Plate 24 Provided
3 is provided.

The operation of adjusting the position of the electrode in the horizontal and vertical directions using the electrode position adjusting mechanism 9 will be described in detail with reference to FIG. Adjustment of the horizontal direction and the mounting angle of the electrode 1 is performed as shown in FIG.
This is performed by pushing the push seat 10 attached to the attachment end of the above by welding or the like with a horizontal push bolt 11 from both sides thereof. Similarly, position adjustment in the beam axis direction is performed by pushing with an axial push bolt 12 shown in FIG.

The vertical position of the electrode 1 is adjusted by pressing the vertical adjustment and lock bolt 13. When all the position adjustments are completed, the electrode 1 is fixed by the lock bolt 13.

According to the present embodiment, the vacuum boundary between the mounting portion of the electrode 1 and the hollow tube 7 is completely sealed by welding without using an O-ring, so that the cooling water channel for cooling the electrode 1 contacts the vacuum boundary. Nothing.

Since the high-frequency current flowing in the hollow tube also flows on the bellows 6 plated with copper, the electrical contact between the electrode 1 and the hollow tube 7 can be completely maintained. Further, using the electrode position adjusting mechanism 9 and the elasticity of the bellows 6, while observing the position of the electrode 1 portion with, for example, a centering telescope, the position is adjusted with each bolt, so that the edge of the electrode 1 is in the correct position. Then, the ion beam 14 can be fixed in place, high positional accuracy can be easily obtained, and the disturbance of the electric field that accelerates and converges the ion beam 14 can be reduced.

As described above, in this embodiment, since the contact on the vacuum seal and the RF current path is perfect, the reliability is high and the position adjustment of the edge of the electrode 1 can be easily performed accurately. As a result, it is possible to obtain an RFQ having a small beam disturbance and a high beam transmittance with little disturbance of the focused electric field.

The electrode position adjusting mechanism 9 is not limited to the above-described embodiment, but can be easily adjusted for the position and the mounting angle of the electrode, and is provided within a range where the electrode can be fixed at that position. Various modifications can be made.

[0035]

As described above, according to the present invention, the portion of the electrode which strongly affects the beam transmittance has an electrode waveform formed by three-dimensional processing with a small error electric field, while a large portion of the electrode length is used. By making the electrode waveform by two-dimensional processing that can be processed in a short time in the other part occupied, the processing of the electrode is easy and the time required for manufacture is shortened, and the bellows is connected between the electrode and the hollow tube Since the electrode position can be adjusted by the electrode position adjusting mechanism, a highly reliable high-frequency multipole accelerator having high beam transmittance can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a high-frequency multipole accelerator according to the present invention.

FIG. 2 is a configuration explanatory view of an electrode position adjusting mechanism according to another embodiment of the present invention.

FIG. 3 is a diagram for explaining in detail electrode position adjustment in the embodiment.

FIG. 4 is a bird's-eye view for explaining the configuration of the RFQ.

FIG. 5 is a cross-sectional view of the RFQ.

FIG. 6 is a diagram schematically showing the behavior of an ion beam in the RFQ.

FIG. 7 is a diagram showing a state of electrode processing of the RFQ.

FIG. 8 is a cross-sectional view for explaining attachment of a conventional electrode and a hollow tube.

[Explanation of symbols]

1 ... electrode, 2 ... radial matching section, 3
…… Bunching section, 4 …… Accelerator, 5
...... Center between cavities, 6 ... bellows, 7 ... hollow tube, 8 ...
... weld seat, 9 ... electrode position adjustment mechanism, 10 ... push seat,
11 horizontal push bolt, 12 axial push bolt, 13 vertical adjustment bolt and lock bolt, 14
... ion beam, 15 ... quadrupole electric field.

Continuation of front page (56) References JP-A-61-107700 (JP, A) JP-A-63-228597 (JP, A) JP-A-6-290900 (JP, A) JP-A-4-48599 (JP) JP-A-6-243999 (JP, A) JP-A-6-275398 (JP, A) JP-A-6-151095 (JP, A) JP-A-5-307999 (JP, A) JP-A-3-245498 (JP, A) JP-A-63-318100 (JP, A) JP-A-60-115199 (JP, A) JP-A-58-34600 (JP, A) A) Japanese Utility Model 1-73800 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05H 9/00

Claims (3)

(57) [Claims] 1. A high-frequency multipole accelerator having a cylindrical hollow tube and a plurality of sets of electrodes for accelerating particles in the hollow tube, the tip shape of which is formed in a waveform along the axial direction of the hollow tube. One of the radial matching section or the bunching section of the beam incident part as the tip shape of the electrode, or all or a part of the radial matching section and the bunching section by three-dimensional processing and the distance from the center of the hollow tube to the edge of the electrode. Edge of electrode
The radius of the radial arm
Three-dimensional with switching and bunching sections
Two-dimensional machining of unprocessed parts and accelerator parts
A high frequency multipole accelerator, wherein the radius of the edge of the electrode is formed to be constant . 2. An electrode provided in the hollow tube is attached via bellows to both edges of a plurality of axially extending openings provided in the hollow tube corresponding to respective electrode mounting positions. The high frequency multipole accelerator according to claim 1. 3. An electrode position adjusting mechanism capable of adjusting the position of the electrode in the horizontal direction, adjusting the position in the vertical direction, and adjusting the position in the beam axis direction at an end of the electrode on the mounting side. 2. The high-frequency multipole accelerator according to 1.