JPH07326499A - High frequency linear accelerator - Google Patents

Abstract

PURPOSE:To provide a high frequency linear accelerator in which the insertion length of an end tuner can be adjusted without mechanical machining while a high vacuum is maintained within a resonator. CONSTITUTION:In this high frequency linear accelerator, high frequency power is supplied to a plurality of electrodes 2 which are arranged in a radiating pattern on cross-sectional view with respect to an axis 3 within an evacuated cavity 1, and an end tuber 10 mounted on the axial end plate 11 of the cavity 1 is adjusted so that the cavity 1 resonates with the high frequency power, and particles are accelerated in the direction of the axis 3 inside the cavity by means of an accelerating electromagnetic field formed in the space surrounded by the electrodes 2. Insertion length adjustment means 15, 16a, 16b, 18 are provided whereby the length by which the end tuner 10 is inserted into the cavity 1 is adjusted while the inside of the cavity 1 is held evacuated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio frequency linear accelerator, and more particularly to a radio frequency quadrupole linac suitable for accelerating relatively slow particles.
ac, hereinafter referred to as RFQ) and other high-frequency linear accelerators.

[0002]

2. Description of the Related Art A high-frequency linear accelerator using protons or ions is an accelerator for ion implantation for surface modification in the field of materials, a driver accelerator for heavy ion inertial fusion devices in the field of energy, or a radioactive material in the field of nuclear power. It is used as an accelerator as a strong proton source for waste disposal. Among the radio frequency linear accelerators, the radio frequency quadrupole linear accelerator (RFQ) is particularly suitable for accelerating relatively low-speed particles.

Various structures have been proposed for RFQ. FIG. 3 shows a conceptual diagram of an example of typical RFQ. FIG. 3 shows a Forvein type RFQ in which four blade-shaped (vane) electrodes 2 are arranged inside a cylindrical type high frequency resonator 1. Inside the RFQ, accelerated particles such as ions travel along the central axis 3 of the resonator 1 and are accelerated while receiving a focusing force and a diverging force that alternately change with time.
High-frequency power is supplied to the inside of the resonator 1 by a high-frequency power supply, a high-frequency transmission system, or the like (not shown), and the quadrupole mode is excited.

FIG. 4 schematically shows a magnetic flux direction 4 and electric force lines 5 at a certain time in a cross section perpendicular to the central axis 3 of the resonator 1. The magnetic flux passes through a resonance chamber (cell) 6 having a sectoral cross section surrounded by the two vane electrodes 2 and the walls of the resonator 1,
The flow flows in the direction along the central axis 3, that is, in the direction perpendicular to the paper surface in FIG. 4, and the directions are opposite to each other between the adjacent cells 6. The vane electrodes 2 facing each other have the same potential, and the adjacent vane electrodes have opposite potentials.

Assuming that the particles to be accelerated are protons, in FIG. 4, the protons near the central axis 3 have a force toward the central axis 3 in the vertical direction, that is, a focusing force, and a central axis 3 in the lateral direction.
Receives a diverging force, that is, a force in the direction away from.
After a half cycle of the high frequency being excited, the polarities are reversed and the divergent force is applied vertically and the focusing force is applied laterally. As described above, the particles to be accelerated are transported without diverging while alternately receiving the focusing force and the diverging force for each half cycle of the high frequency in the vertical direction and the horizontal direction.

FIG. 5 is a schematic view of a VV cross section of the conceptual diagram of FIG.
Shown in. The tip of the vane electrode 2 is processed into a wavy shape called modulation. As a result, the lines of electric force 5 are inclined as shown in FIG.
An electric field component is generated along with to generate an acceleration force. If the modulation is designed so that the time for the accelerated particles to pass between the point 8 where the tip of the vane electrode 2 is closest to the central axis 3 and the point 9 that is farthest from the central axis 3 is equal to the half cycle of the high frequency, the accelerated particles are You can always be accelerating.

In order to obtain the acceleration performance as designed, the electric fields generated in the gaps at the tips of the four vane electrodes 2 are well-balanced in size with respect to the four gaps, and along the central axis 3. Therefore, the electric field distribution needs to be flat. The flatness of the electric field distribution along the central axis 3 is usually adjusted at the end of the resonator 1.

FIG. 6 shows an enlarged sectional view of a conventional RFQ end portion. In FIG. 6, Ed tuner 10 is an end plate 1 of RFQ.
1 has a structure in which a part of 1 projects toward the end surface 2a of the vane electrode 2. By changing the distance between the end surface 2a of the vane electrode 2 and the end portion 10a of the end tuner 10, the capacitance component formed between the end surface 2a and the end portion 10a is changed, and the flatness of the electric field is changed. adjust.

Between the end tuner 10 and the end plate 11,
A contactor 12 is inserted in order to secure a flow path of a wall current induced by an internal high frequency magnetic field of the resonator 1.

Further, the inside of the resonator 1 is kept in a high vacuum so that the particles to be accelerated are not dissipated by collision with the residual gas. Therefore, an O-ring 14 is inserted for vacuum sealing at the contact surface 13 between the end tuner 10 and the end plate 11. A beam duct (not shown) is connected to the end tuner 10 to keep the passage of the particles to be accelerated in a high vacuum.

In actual adjustment, the end tuner 10 is first used.
Was made so that the insertion length into the resonator 1 would be long,
A spacer having an appropriate thickness is sandwiched between the contact surfaces 13 and the insertion length is changed to determine the optimum insertion length. Next, the tip of the end tuner 10 is ground by the same thickness as the inserted spacer so that the insertion length of the end tuner 10 becomes the optimum value with the spacer removed.

[0012]

In the conventional end tuner 10, since machining is required to adjust the insertion length, it is difficult to obtain an optimum value due to machining error and the like.
In addition, the vacuum must be broken at the time of adjustment, and if readjustment becomes necessary due to aging or the like, the adjustment cannot be easily performed.

Therefore, an object of the present invention is to solve the problems of the prior art, to eliminate the need for machining, and to adjust the insertion length of the end tuner while maintaining a high vacuum inside the resonator. Is to provide.

[0014]

In order to achieve the above-mentioned object, a high frequency linear accelerator according to the present invention applies a high frequency power to a plurality of electrodes radially arranged in cross section with respect to an axis in a cavity under vacuum. It is supplied and adjusted by an end tuner attached to an end plate in the axial direction of the cavity so that the cavity resonates with the high frequency power, and an accelerating electromagnetic field formed in a space surrounded by the electrodes A high-frequency linear accelerator for accelerating particles in an axial direction is characterized by comprising insertion length adjusting means for adjusting a length of the end tuner inserted into the cavity while maintaining a vacuum in the cavity.

Further, the insertion length adjusting means has a bellows which is disposed between the end plate and the end tuner and which can be expanded and contracted in the axial direction, and an expansion and contraction means for expanding and contracting the bellows. .

Further, the insertion length adjusting means has a flexible member attached between the end plate and the end tuner, and an expansion / contraction means for expanding / contracting the flexible member in the axial direction. Characterize.

[0017]

The length by which the end tuner is inserted into the cavity can be adjusted by the insertion length adjusting means while maintaining the vacuum in the cavity, so that the inside of the resonator can be adjusted without machining. The insertion length of the end tuner can be adjusted while maintaining a high vacuum.

Further, the bellows is arranged between the hollow end plate and the end tuner, and the bellows is expanded and contracted in the axial direction by the expansion and contraction means to insert the end tuner while keeping the inside of the resonator in a high vacuum. The length can be adjusted.

Further, the flexible member is attached between the end plate of the cavity and the end tuner, and the flexible member is expanded and contracted in the axial direction by the expansion and contraction means, so that the inside of the resonator is kept in a high vacuum. The insertion length of the end tuner can be adjusted.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged sectional view of an end portion of a radio frequency quadrupole linear accelerator (RFQ) according to a first embodiment of the present invention. The same parts as those described above are designated by the same reference numerals and the description thereof will be omitted. In FIG. 1, the end tuner 10 is formed of an electric conductor and has a drum-shaped cylindrical portion 10c.
And an end portion 10a protruding inward from one end of the cylindrical portion 10c and facing the end surface 2a of the vane electrode 2, and the cylindrical portion 1
0c has a flange portion 10b protruding in the outer peripheral direction at the other end. A window 10d through which the accelerated particles are emitted is formed in the center of the end 10a.

A plurality of bolts 15 are erected in a circular shape on the end plate 11. Each bolt 15 penetrates the flange portion 10b of the end tuner 10, and the end tuner 10 is fixed by sandwiching the nuts 16a and 16b from both sides of the flange portion 10b. Nuts 16a, 16
The position of b can be adjusted. A cylindrical bellows 18 is disposed between the end plate 11 and the flange portion 10b of the end tuner 10 via a donut-shaped connecting flange 19. One end of the bellows 18 has a flange portion 10
It is welded to b and the other end is welded to the connecting flange 19. The O-ring 14 is arranged in the groove of the connection flange 19, and the connection flange 19 is pressed against the end plate 11 by the bellows 18 with the O-ring 14 interposed therebetween.

The cylindrical portion 10c of the end tuner 10
The contactor 1 is provided between the end plate 11 and the end plate 11 in order to secure a flow path of a wall current induced by the internal high-frequency magnetic field of the resonator 1.
2 is inserted.

In this embodiment, the insertion length adjusting means comprises a bellows 18 and an expanding / contracting means composed of bolts 15 and nuts 16a and 16b.

Next, the operation of this embodiment will be described.
By adjusting the positions of the nuts 16a and 16b along the bolt 15, the bellows 18 can be expanded and contracted, and the distance between the end surface 2a of the vane electrode 2 and the end portion 10a of the end tuner 10 becomes a desired value. Nut 16 in position
The positions of a and 16b are fixed.

According to the structure of this embodiment, the nuts 16a,
Since the bellows 18 can be expanded and contracted by adjusting the position of 16b along the bolt 15, the distance between the end surface 2a of the vane electrode 2 and the end portion 10a of the end tuner 10 can be adjusted, and the end tuner 10 can be adjusted. The length of insertion of the can into the cavity can be changed.

Further, since the insertion length of the end tuner is adjusted by adjusting the positions of the nuts 16a and 16b, the optimum value of the insertion length can be easily adjusted and readjustment can be easily performed.

Since the O-ring 14 is provided between the connecting flange 19 and the end plate 11 for vacuum sealing and the O-ring 14 is pressed against the end plate 11 by the bellows 18, the vacuum in the cavity is maintained. The insertion length of the end tuner 10 can be changed without changing.

As a result, the movement of the end tuner 10 can be absorbed by the expansion or contraction of the bellows 18, and the insertion length of the end tuner can be adjusted while keeping the inside of the resonator 1 at a high vacuum. This makes it possible to eliminate the need for machining for adjustment.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the end tuner 10
A donut-shaped flexible plate 20 is attached by welding between the lower outer surface of the cylindrical portion 10c and the end plate 11 so that the inside of the cavity can be vacuum-sealed. The flexible plate 20 is made of a conductive material.

A plurality of bolts 15 are erected on the end plate 11 in a circular shape. Each bolt 15 is an end tuner 1
0 through the flange portion 10b, and the end tuner 10 includes nuts 16a, 16 from both sides of the flange portion 10b.
It is fixed by inserting it in b. Nut 16
The positions of a and 16b can be adjusted. In this embodiment, the insertion length adjusting means is a flexible plate 20, and an expanding / contracting means composed of bolts 15 and nuts 16a and 16b.
It consists of

According to the structure of this embodiment, the nuts 16a,
Since the flexible plate 20 can be expanded and contracted in the axial direction by adjusting the position of 16b along the bolt 15, the distance between the end surface 2a of the vane electrode 2 and the end portion 10a of the end tuner 10 is adjusted. The insertion length of the end tuner 10 into the cavity can be changed.
As a result, the flexible plate 20 expands or contracts, so that the movement of the end tuner 10 can be absorbed, and the insertion length of the end tuner can be adjusted while maintaining a high vacuum inside the resonator 1. This makes it possible to eliminate the need for machining for adjustment.

The flexible plate 20 is the end tuner 10.
Since the inside of the cavity is attached by welding between the lower outer surface of the cylindrical portion 10c and the end plate 11 so that the inside of the cavity can be vacuum-sealed, the end tuner 1 with the vacuum inside the cavity maintained.
The insertion length of 0 can be changed.

Moreover, since the flexible plate 20 is formed of a conductive material, the function of the contactor 12 shown in FIG. 1 or 6 can be substituted by the flexible plate 20, and the contactor 12 can be omitted. it can.

In the above description of the embodiments, the radio frequency linear accelerator is a radio frequency quadrupole linear accelerator (RFQ).
However, the present invention is not limited to this, and the number of electrodes radially arranged with respect to the axis in the cavity may be other than four.

[0035]

As described above, according to the structure of the present invention, since the insertion length adjusting means is provided, the length by which the end tuner is inserted into the cavity is maintained while the vacuum inside the cavity is maintained. Adjustable Adjustable and adjustable insert length of end tuner without machining.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing an end portion of a radio frequency quadrupole linear accelerator (RFQ) of a first embodiment of a radio frequency linear accelerator of the present invention.

FIG. 2 is an enlarged sectional view showing an end portion of the second embodiment.

FIG. 3 is a perspective view showing a schematic configuration of a Forbes type RFQ.

FIG. 4 is a cross-sectional view as seen from a cross section perpendicular to the central axis of the Forvein type RFQ shown in FIG.

5 is a cross-sectional view showing a cross section viewed from VV in FIG.

FIG. 6 is an enlarged cross-sectional view showing an end portion of a conventional radio frequency quadrupole linear accelerator (RFQ).

[Explanation of symbols]

 1 resonator 2 vane electrode 3 axis 4 direction of magnetic flux 5 electric flux line 6 resonance chamber (cell) 8 point where the tip of the vane electrode is closest to the central axis 9 point where the tip of the vane electrode is farthest from the central axis 10 end tuner 10a End part of the end tuner 10b Flange part of the end tuner 10c Cylindrical part of the end tuner 11 End plate 12 Contactor 13 Contact surface between end tuner and end plate 14 O-ring 15 Bolts 16a, 16b Nut 18 Bellows 19 Connection flange 20 Flexible plate 20a End face of flexible plate

Claims (3)

[Claims] 1. A high-frequency power is supplied to a plurality of electrodes radially arranged with respect to an axis in a cavity under vacuum, and the cavity is formed by an end tuner attached to an axial end plate of the cavity. Is tuned to resonate with the high-frequency power, and a high-frequency linear accelerator for accelerating particles in an axial direction in the cavity by an accelerating electromagnetic field formed in a space surrounded by the electrodes, wherein the end tuner is inserted into the cavity. The length
A high-frequency linear accelerator comprising an insertion length adjusting means for adjusting the vacuum in the cavity while maintaining the vacuum. 2. The insertion length adjusting means includes a bellows which is arranged between the end plate and the end tuner and which can expand and contract in the axial direction, and a expanding and contracting means for expanding and contracting the bellows. The high frequency linear accelerator according to claim 1. 3. The insertion length adjusting means includes a flexible member mounted between the end plate and the end tuner, and an expansion / contraction means for expanding / contracting the flexible member in the axial direction. The high frequency linear accelerator according to claim 1, which is characterized in that.