JP3243683B2 - Accelerator tube and accelerator for charged particle acceleration, charged particle gun and standing wave accelerating cavity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accelerator for accelerating charged particles, and more particularly to an accelerator capable of supplying a large amount of electric power as accelerating power and a charged particle accelerating tube as a component thereof.

[0002]

2. Description of the Related Art In recent years, when an electron beam is used by a collision type linear accelerator "linear collider" for studying elementary particles, a free electron laser, or the like, it is required to minimize the emittance of the electron beam. The emittance is an index indicating the parallelism of a beam represented by the product of the beam gradient and the beam size. For example, in the case of the linear collider JLC proposed in Japan, according to "Physics of the linear collider-JLC-I-"("Scientific Research Grant of 1993 (Comprehensive Research A) Research Result Report")
The emittance of the beam at the final collision point is 3 × 10 to ⁸ ra
d · m. In order to generate such an extremely low emittance beam, measures such as the use of an emittance attenuating ring to optimize the electron gun and the suppression of the increase in emittance when accelerating the beam to high energy are to be minimized. There is a need.

In order to accelerate a charged particle beam to high energy, a high-frequency accelerator is used. FIG. 16 is a configuration diagram of a conventional acceleration tube. High frequency power 7 is transmitted from the high frequency source using the waveguide 1, and the high frequency power 7 is input to the acceleration tube 3 through the coupling hole 2. The dotted line 4 shown is
The dotted line 5 is the magnetic field distribution in the waveguide.

In the case of the accelerating tube according to the prior art, since high-frequency power is input from one coupling hole 2, the accelerating tube 3
The rotational symmetry of the distribution 5 of the electromagnetic field inside is broken. Therefore, the charged particle beam accelerated in the accelerating tube 3 receives a force perpendicular to the beam traveling direction, increasing the emittance and the problem that large power cannot be supplied to increase the acceleration efficiency. is there.

As a conventional technique for solving the problem of rotational symmetry of an electromagnetic field, there is, for example, a technique disclosed in Japanese Utility Model Laid-Open No. 4-40500. In this prior art, a notch groove is provided in the opposite wall of the coupling hole 2 to compensate for the symmetry of the electromagnetic field. But,
Even if such measures are taken, there is a limit, and the problem of supplying large power cannot be solved.

On the other hand, the prior art proposed by Stanford University Linear Accelerator Center, that is, SLAC-PUB-5887
August 1992 “SYMMETRICAL DOUBLE INPUT COUPLER DEV
According to ELOPMENT ”H. Deruyter, H. Hoag, K. Ko and C.-K Ng, high frequency power from a high frequency source is
The waveguide is divided into two waveguides having the same length, and guided to the accelerating tube.
There has been proposed a method of inputting data from two connection holes.

According to the method of inputting high-frequency power to an accelerator tube proposed by Stanford University, a large power can be supplied because power is input from two coupling holes, and the emittance of the beam is high because of high rotational symmetry. Has the advantage of being small.

[0008]

The above-mentioned proposal of Stanford University has the advantage that the beam emittance is small and large power can be supplied. However, the configuration according to this proposal has a problem that the size of the apparatus is increased and a cost is increased because a duplexer must be used, and there is a problem that it cannot be applied to an actual device. For example, when constructing a linear accelerator having a length of 1 km, the main body of the linear accelerator is to connect, for example, 1000 accelerator tubes having a length of 1 m in series. Since it is necessary to provide a demultiplexer for each accelerating tube,
In addition to the increase in the cost of the duplexer, the construction cost associated with the increase in the size of the device also increases.

It is an object of the present invention to provide a small and inexpensive charged particle accelerating tube and an accelerator using the same.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acceleration tube for accelerating a charged particle beam by high-frequency power input from the outside, provided at a rotationally symmetric position with respect to a center axis of an input end coupler of the acceleration tube. N (n: a positive integer of 2 or more)
A single waveguide in which the high-frequency power is input from one end and the other end is short-circuited, and is provided to be curved around the input end coupler and provided at the positions of the n coupling holes. This is achieved by providing a waveguide in communication with the input end coupler.

[0011]

The high-frequency power enters the acceleration tube from the n number of rotationally symmetric coupling holes, so that the beam emittance is small. Further, since the high-frequency power enters the acceleration tube from the n number of coupling holes, the number of coupling holes is one. More electric power is supplied into the accelerator tube while keeping the electric field due to the higher-order mode generated near the coupling hole smaller than in the case of the individual pieces.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a configuration diagram of a linear accelerator according to one embodiment of the present invention. In FIG. 4, four accelerator tubes 80a, 80b, 80c,
80d are connected in series, and converging magnets 601a, 601 for suppressing the divergence of the electron beam
b, 601c and 601d are provided. Each accelerator tube 8
0a, 80b, 80c, and 80d include klystrons 300a, which have been commanded by the control device 400 of the linear accelerator.
High-frequency power from 300b is input power coupler 100a, 100b, 100c, 100 which is the power input power of each accelerator tube.
A high-frequency electric field for accelerating the electron beam is generated inside each of the acceleration tubes 80a to 80d. In the illustrated example, four accelerators are connected, but if a long linear accelerator is required, similar accelerators may be connected on the order of several tens, hundreds, or thousands.

When a high voltage is applied to the electron gun 500a from the electron gun high voltage power supply 500b in response to a command from the control unit 400 of the linear accelerator, an electron beam is extracted from the electron gun 500a, and the first stage of the acceleration tube 80a. The electron beam input into the acceleration tube 80a is accelerated by the high-frequency electric field inside the acceleration tube and is emitted into the second stage acceleration tube 80b. Thereafter, similarly, the electron beams sequentially accelerated by the second, third, and fourth stage acceleration tubes 80b to 80c are emitted from the output end of the fourth stage acceleration tube 80d.

FIG. 2 is a sectional view of the accelerator tube 80a shown in FIG. 4, and FIG. 3 is a sectional view of the accelerator tube 80a shown in FIG. 2 as viewed from another direction. Although the structure of the acceleration tube 80a will be described, the other acceleration tubes 80b to 80d have the same structure. Generally, a coupler 90a and a coupler 90b are provided at both ends of the acceleration tube 80a. The present embodiment is characterized in that waveguides 1a and 1b are provided around the couplers 90a and 90b as described in detail later.
In FIG. 4, the couplers 90a and 90b to which are attached are the input coupler 100a and the output coupler 101a.

The high frequency power from the klystron 300a is introduced into the waveguide 1a of the input end coupler 100a, propagates through the waveguide 1a, and is provided on the central axis of the coupler 100a through the coupling holes 2a and 2b. Is input into the space 9 where the user is. Then, the high-frequency power propagates in the acceleration tube 80a in the direction 71 of the central axis, and generates a high-frequency electric field in the acceleration tube 80a.

The electron beam input from the electron gun 500a (FIG. 4) is accelerated by this high-frequency electric field, and
It is emitted as 00. The high frequency power not used for accelerating the electron beam is supplied to the coupling hole 2 of the output end coupler 101a.
The light enters the waveguide 1b from c and 2d (FIG. 3), propagates in the direction of arrow 72, and is absorbed by the non-reflection end 102. Although the waveguides 1a and 1b have the same configuration,
Is attached to the open end of the waveguide 1b (where the input end of the waveguide 1a is the high-frequency power).

FIG. 1 is a cross-sectional view (a cross-sectional view taken along the line II of FIG. 4) of an input end coupler 100a serving as a power input end of the acceleration tube 80a of FIG. 4 (the acceleration tube according to the first embodiment of the present invention). It is. One waveguide 1a is provided to be curved in a U-shape around a coupler 90a provided at the end of the acceleration tube 80a. The high-frequency power 7 from the klystron 300a is supplied to the open end of the waveguide 1a.

The coupler 90a has a space 9 on its central axis.
(Coaxially arranged with the central axis of the accelerating tube 80a) and the coupling holes 2a and 2b communicating the waveguide 1a are provided. The coupling holes 2a and 2b are arranged at rotationally symmetric positions with the central axis of the space 9 as the axis of symmetry. Waveguide 1a
In this embodiment, an H bend 50 is formed between the coupling holes 2a and 2b.
a, 50b, and the other end of the waveguide 1a is
(Or a dielectric). Each ring-shaped dotted line 4 shown in FIG. 1 indicates a high-frequency magnetic field distribution inside the waveguide 1a. The coupling holes 2a and 2b are provided at positions where the high-frequency magnetic field on the side surface of the waveguide 1a is the strongest and the magnetic field distribution 5 derived into the space 9 is strengthened. That is,
The coupling holes 2a and 2b are formed at positions where the distance L1 in the waveguide between the coupling holes 2a and 2b is three times the guide wavelength λg in the high-frequency waveguide used. In the present embodiment, the distance L1 is set to be three times the guide wavelength λg. However, the present invention is not limited to this. It is possible. Also,
The conductor 6 terminating the waveguide 1a is arranged at a position having a length L2 from the closest coupling hole (the coupling hole 2b in FIG. 1). A value of 4 is preferred. However, in general, the distance L2 may be substantially equal to the sum of the length of 1/4 of the guide wavelength and 0 or an integral multiple of the length of 1/2 of the guide wavelength.

In this embodiment, by adopting such a configuration, the rotational symmetry of the acceleration electromagnetic field distribution of the accelerator tube can be increased, and the emittance of the beam does not increase in principle. Also, by providing two coupling holes, the number of coupling holes is one.
When supplying the same power to the accelerating tube as in the case where there is only one, the power passing through one coupling hole can be reduced, and the coupling holes 2a, 2
The electric field near b can be reduced. Conversely, as compared with the case where there is only one coupling hole, more electric power can be supplied into the acceleration tube while the electric field due to the higher-order mode generated near the coupling hole is kept small, and the acceleration performance of the electron beam is enhanced. Therefore,
It is possible to obtain a small-sized, low-cost accelerator tube with a high electric field in which an increase in beam emittance is prevented.

FIG. 5 is a configuration diagram of a circular accelerator according to one embodiment of the present invention. Circular accelerator 220 according to the present embodiment
Transmits an electron beam from an electron beam injection system in which the acceleration tubes 8a and 80b shown in FIG.
It is taken into a circular orbit from No. 1 and orbited, and is used for synchrotron radiation generation and elementary particle experiments. The same reference numerals are given to the same component devices as those shown in FIG. According to the present embodiment, it is possible to obtain a high-energy electron synchrotron system which is small in size and low in cost and prevents an increase in beam emittance.

FIG. 6 is a sectional view of an acceleration tube according to a second embodiment of the present invention. The acceleration tube according to the second embodiment is a modification of the acceleration tube according to the first embodiment shown in FIG. Second
In the accelerating tube according to the embodiment, the output waveguide 1b is attached to the input waveguide 1a at a position rotated by 90 degrees as compared with the first embodiment. With this configuration, the same effect as in the first embodiment can be obtained.

FIG. 7 is a configuration diagram of an electron gun according to an embodiment of the present invention. The electron gun according to this embodiment includes a waveguide 1a having the same configuration as the waveguide shown in FIG. As described with reference to FIG. 1, when high-frequency power is supplied to the waveguide 1a, the high-frequency power propagates in the waveguide 1a, and the coupling holes 2a, 2b
Is supplied into the electron gun cavity 81. As a result, a high-frequency electric field is generated in the electron gun cavity 81. The electrons generated at the cathode 85 are extracted by this high-frequency electric field, accelerated, and emitted from the electron gun as an electron beam 200. As the cathode 85, a hot cathode for generating thermoelectrons, a photocathode for generating photoelectrons, a cold cathode for generating field emission electrons, or the like can be used. With such a configuration, an electron gun having a small emittance and capable of generating a high-energy electron beam can be obtained.

FIG. 8 is a block diagram showing an embodiment of a standing wave acceleration cavity using the coupler shown in FIG. Waveguide 1a
And the high frequency power is supplied into the cavity 83 through the coupling holes 2a and 2b. As a result, a high-frequency electric field is generated in the cavity 83, and electrons that have entered the cavity 83 from the left side in FIG. 8 are accelerated (or compressed) by the high-frequency electric field and emitted as a beam 200. With this configuration, it is possible to configure an acceleration cavity having a small emittance and a high electric field. The configuration of the present embodiment is applicable to all acceleration cavities that supply high-frequency power into the cavity using the coupling hole between the waveguide and the acceleration cavity.

FIG. 9 is a cross-sectional view of a coupler portion of an acceleration tube according to a third embodiment of the present invention. In the waveguide 1a of FIG.
High frequency power 7 is input from the opening end. This waveguide 1
a is tightly wound around the outer periphery of the coupler 90, and
It communicates with the space 9 provided on the central axis of the coupler 90 via a, 2a ', 2b, 2b'. Coupling holes 2a, 2
Each of a ′, 2b, and 2b ′ is disposed at a rotationally symmetric position by 90 degrees around the symmetry axis with the central axis of the coupler 90 as a symmetry axis. The coupling holes of the waveguide 1a are connected by H-bends 50a, 50b, 50c and terminated by the conductor 6.

Each dotted line 4 shown is the high-frequency magnetic field distribution of the waveguide. The coupling holes 2a and 2b are located at positions where the high-frequency magnetic field on the waveguide side surface is the strongest and the magnetic field distribution 5 derived in the space 9 is strengthened, that is, the distance between the coupling holes 2a and 2b is substantially equal to the guide wavelength. The distance between the holes 2b-2a 'is also substantially the same as the guide wavelength, the distance between the coupling holes 2b' and 2a 'is also substantially the same as the guide wavelength, and the first coupling hole 2a and the last coupling hole 2b'.
Are arranged so that the distance L1 between them is approximately three times the guide wavelength. Further, the conductor 6 terminating the waveguide is arranged at a position such that the distance L2 from the closest coupling hole 2a 'is substantially equal to the length of a quarter wavelength.

With this configuration, the coupler 90
The rotational symmetry of the acceleration electromagnetic field distribution 5 in the space 9 can be increased, and the emittance of the beam does not increase in principle. Therefore, it is possible to provide a small, low-cost, and highly efficient accelerator capable of accelerating the electron beam. . In FIG. 9, the distance between the coupling holes is substantially equal to the guide wavelength. However, it goes without saying that the distance may be any integer multiple of the guide wavelength.

FIG. 10 is a sectional view of a coupler part of an acceleration tube according to a fourth embodiment of the present invention. Coupler 90 of the present embodiment
The waveguide 1 provided around is made of a waveguide 55 that is curved in a circular shape, and the distance L1 between the coupling holes 2a and 2b is set to twice the guide wavelength. With such a configuration, a similar effect can be obtained.

FIG. 11 is a sectional view of a coupler portion of an accelerator according to a fourth embodiment of the present invention. Waveguide 1 of the present embodiment
Is a waveguide 55a having a wide cross section curved around the coupler 90.
While using a taper tube 56a for impedance matching. By using the waveguide 55a having a wide cross section around the coupler 90, the guide wavelength in the waveguide 55a can be shorter than the guide wavelength in the entrance portion. Therefore, the thickness of the windows of the coupling holes 2a and 2b provided in the coupler 90 can be reduced. The distance L1 in the waveguide between the coupling holes 2a and 2b is arranged to be an integral multiple of the guide wavelength in the waveguide 55a, and approximately twice in the present embodiment, and a conductor that terminates the waveguide. 6 is 1 / の of the guide wavelength from the closest coupling hole.
4 lengths. In this embodiment, the same effects as those of the first to third embodiments can be obtained.

FIG. 12 is a sectional view of a coupler portion of an accelerator according to a fifth embodiment of the present invention. Waveguide 1 of the present embodiment
Is a waveguide 55b having a narrow cross section curved around the coupler 90.
While using a taper tube 56b for impedance matching. By using the waveguide 55b having a narrow cross section around the coupler 90, the guide wavelength in the waveguide 55b can be made longer than the guide wavelength in the entrance portion. Therefore, the thickness of the windows of the coupling holes 2a and 2b provided in the coupler 90 can be reduced. The distance L1 in the waveguide between the coupling holes 2a and 2b is arranged so as to be an integral multiple of the guide wavelength in the waveguide 55b, and approximately equal in this embodiment, and a conductor that terminates the waveguide. 6 is 1 / の of the guide wavelength from the closest coupling hole.
4 lengths. In this embodiment, the same effects as those of the first to fourth embodiments can be obtained.

FIG. 13 is a sectional view of a coupler according to a sixth embodiment of the present invention. In FIG. 13, the waveguide 1 having a rectangular cross section to which the high-frequency power 7 is input has a wider width disposed on the coupler 90 side in this embodiment. In the coupler 90,
Coupling holes 2a and 2b are arranged at rotationally symmetric positions with the central axis of the accelerating tube as a symmetry axis, and communicate with the waveguide 1 through these coupling holes 2a and 2b. The coupling holes 2a of the waveguide 1,
The portion between 2b is constituted by E-bends 59a and 59b, and ends are terminated by the conductor 6. Dotted line 4 shows the high frequency magnetic field distribution of the waveguide. That is, in the waveguide 1 of this embodiment, the direction of the high-frequency magnetic field is different from that of the above-described embodiment. The distance L1 between the coupling holes 2a and 2b is set to be three times the wavelength λg of the high frequency wave used in the waveguide, and the distance between the terminal 6 and the coupling hole 2b is set to １ ／ wavelength. In this embodiment, the same effects as those of the above-described embodiment can be obtained.

FIG. 14 is a longitudinal sectional view of an accelerator tube using the coupler shown in FIG. FIG. 15 is a longitudinal sectional view of an accelerator tube using the coupler shown in FIG. 13 from another direction. The acceleration tube according to the present embodiment also has the same effect as the acceleration tube shown in FIG.

In the above-described embodiment, two coupling holes are provided.
Although four holes were used, the number of bonding holes is not limited to an even number, and it goes without saying that an odd number of three or more may be used. When three or more odd numbered coupling holes are provided, each coupling hole is provided at a position to be rotated with respect to the center axis of the acceleration tube (for example, when three coupling holes are provided, they are provided at intervals of 120 degrees).
At the same time, the distance between the coupling holes is an integral multiple of the guide wavelength, and the distance from the short-circuit end to the closest coupling hole is ([1
/ 4] + m / 2) times (m: 0 or a positive integer).

[0033]

According to the present invention, it is possible to realize a small-sized and low-cost accelerating cavity for preventing an increase in the emittance of a beam in principle. In addition, since at least two coupling holes are used to supply high-frequency power to the accelerating cavity, the high-frequency power to be supplied is increased while the electric field due to the higher-order mode generated near the coupling holes is increased, and the electric field strength in the accelerating cavity is increased. The electron beam can be efficiently accelerated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a coupler of an acceleration tube according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of an acceleration tube using the coupler shown in FIG.

FIG. 3 is a vertical cross-sectional view of the accelerator tube shown in FIG. 2 rotated by 90 degrees with respect to an axis.

4 is a configuration diagram of an example of a linear accelerator configured by vertically connecting the acceleration tubes shown in FIG. 2;

FIG. 5 is a configuration diagram of an example of a circular accelerator using the accelerator tube shown in FIG. 2 in a beam incidence system.

FIG. 6 is a cross-sectional view of the acceleration tube of the embodiment in which the exit-side coupler is rotated by 90 degrees with respect to the axis with respect to the entrance-side coupler of the acceleration tube shown in FIG.

FIG. 7 is a configuration diagram of an example of an electron gun using the same principle as the accelerator tube shown in FIG.

FIG. 8 is a configuration diagram of an embodiment of a standing wave acceleration cavity using the same principle as the acceleration tube shown in FIG. 1;

FIG. 9 is a cross-sectional view of a coupler of an acceleration tube according to a second embodiment of the present invention.

FIG. 10 is a cross-sectional view of a coupler of an acceleration tube according to a third embodiment of the present invention.

FIG. 11 is a sectional view of a coupler of an acceleration tube according to a fourth embodiment of the present invention.

FIG. 12 is a sectional view of a coupler of an acceleration tube according to a fifth embodiment of the present invention.

FIG. 13 is a sectional view of a coupler of an accelerator according to a sixth embodiment of the present invention.

14 is a longitudinal sectional view of an acceleration tube using the coupler shown in FIG.

FIG. 15 is a cross-sectional view in which the acceleration tube shown in FIG. 14 is rotated 90 degrees with respect to an axis.

FIG. 16 is a configuration diagram of a conventional acceleration tube.

[Explanation of symbols]

1, 1a, 1b ... waveguide, 2a, 2a ', 2b, 2
b ', 2c, 2d: coupling hole, 3: acceleration cavity, 4: magnetic field distribution of waveguide, 5: magnetic field distribution in acceleration cavity, 6: terminal conductor, 7: high-frequency power, 8: charged particle beam , 9: anti-reflection termination, 20: electron gun, 21, 21a, 21b: acceleration cavity, 56a, 56b: taper tube, 301a, 301b ...
Power supply, 300a, 300b ... klystron, 500a
... Electron guns, 601a to 601d.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-289096 (JP, A) JP-A-6-28983 (JP, A) JP-A-64-16000 (JP, A) JP-A-64 54902 (JP, A) Japanese Utility Model 4-40500 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05H 9/00 H05H 7/18 H05H 9/04

Claims (8)

(57) [Claims] 1. An accelerating tube for accelerating a charged particle beam by high-frequency power input from the outside, wherein n is provided at a rotationally symmetric position with respect to a center axis of an input end coupler of the accelerating tube.
(N: a positive integer equal to or greater than 2) coupling holes, and a single waveguide having the high-frequency power input from one end and the other end short-circuited and curved around the input end coupler. And a waveguide provided at said n coupling hole positions and communicated with said input end coupler. 2. The waveguide according to claim 1, wherein a distance between a short-circuited end of the waveguide provided around the input-end coupler and a coupling hole closest to the short-circuited end is a guide wavelength of the high-frequency power in the waveguide. [1/4] + m / 2) times (m: 0 or a positive integer) an acceleration tube for charged particle acceleration. 3. A high-frequency power supply according to claim 1, wherein a magnetic field penetrating from a waveguide provided around the input end coupler to an acceleration cavity inside the coupler through each coupling hole reinforces each other. An acceleration tube for accelerating charged particles, wherein the guide wavelength in the waveguide is determined. 4. A plurality of accelerated tubes for accelerating charged particles according to claim 1 connected in series,
A focusing magnet provided at the connection of each charged particle acceleration tube, a charged particle gun provided on one side of the charged particle acceleration tube connected in series, and a high frequency supplied to each charged particle acceleration tube Klystron, and linearly characterized by comprising control means for emitting charged particles from the charged particle gun and outputting a control command so as to supply high-frequency power synchronized with each klystron to each charged particle accelerating accelerating tube. Accelerator. 5. A circular accelerator for orbiting a charged particle beam, wherein a charged particle incident system of the circular accelerator is provided in the circular accelerator.
A circular accelerator comprising the charged particle accelerating tube according to claim 3. 6. A waveguide according to claim 1, wherein a charged particle gun for extracting charged particles is a mechanism for accelerating and emitting charged particles generated by a charged particle source with high-frequency power. A charged particle gun provided with the same mechanism as described above. 7. A standing wave acceleration cavity, wherein the same mechanism as the waveguide according to any one of claims 1 to 3 is provided in the standing wave acceleration cavity. 8. An accelerating tube for accelerating a charged particle beam by externally input high-frequency power, wherein said high-frequency power is input from one end and the other end is a short-circuited end, and said acceleration tube is a single waveguide. A waveguide curved around the input end coupler of the tube and communicated with the input end coupler through a plurality of coupling holes, and provided at a position to be rotated with respect to a central axis of the input end coupler; A plurality of coupling holes, the distance between adjacent coupling holes being an integral multiple of the wavelength of the high-frequency power in the waveguide.