JPH05307999A - Energy variable type rfq linear accelerator - Google Patents

Abstract

PURPOSE:To provide a four pole RFQ linear accelerator capable of arbitraly changing the energy of charged beam to be taken from an accelerator. CONSTITUTION:An energy variable type RFQ linear accelerator 10 is provided with four sheets of metal plates 13 along the vicinity of the tip between four vanes 12, 12 adjacent to each other in the circumferential direction of a resonant cavity 11, so as to function as earth vanes and move to and fro in the radial direction of the cavity 11. The accelerator 10 increases equivallent capacitance C in the cavity 11 and changes the capacitance C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, an RFQ linear accelerator for efficiently accelerating a low energy charge beam, and more particularly to a variable energy type RFQ linear accelerator suitably used as an ion implanter or the like.

[0002]

2. Description of the Related Art As conventional techniques of this kind, for example,
Some were published in Accelerator Science in 1984. This will be described with reference to FIGS. 3 (a) and 3 (b). In the figure, 1 is a cylindrical cavity that forms a resonator, and 2 is mounted in the cylindrical cavity 1 at equal intervals in the circumferential direction so as to project radially inward from its inner peripheral surface. Each of the vanes 2 has a corrugated tip as shown in FIG. 2B, and the corrugated shapes of the vanes 2 and 2 facing each other. A gap is formed between the tips of the. Further, 3 is formed on the inner surface of the cylindrical cavity 1 by a cylindrical metal block attached between the vanes 2 and 2 which are adjacent to each other in the circumferential direction, and is used for fine adjustment of the resonance frequency and adjustment of the electromagnetic field distribution. It is a side tuner used, and is installed in two places in the longitudinal direction of the cylindrical cavity 1, and each tuner 3
A drive device 4 projecting from the outer surface of the cylindrical cavity 1 is attached to each of these, and the drive device 4 is attached to the side tuner 3
I put it in and out. Further, a loop coupler 5 for supplying high-frequency power to the cylindrical cavity is attached approximately in the middle of the side tuners 3, 3 in the longitudinal direction. And each of the above-mentioned members is formed of a conductor,
An apparatus having such a configuration is an apparatus for converging and accelerating a charged beam by a high frequency electric field, and is generally used in the first stage part of a high energy accelerator for carrying out a nuclear experiment or the like. In addition, what attached the vane 2 attached in the said cylindrical cavity 1 is hereafter defined as an acceleration cavity or a resonance cavity.

When an alternating voltage of the same sign is applied between the pair of vanes 2 and 2 facing each other and an alternating voltage of the opposite sign is applied to the other pair of vanes 2 and 2 in the same manner, the charged beam A quadrupole electric field is generated in the aperture surrounded by the four vanes 2 passing through. The quadrupole electric field exerts a focusing force on the charged beam, but since the electric field is generated in the traveling direction of the charged beam by the corrugated tip of each vane 2, the charged beam also receives an accelerating force. At this time, since the period of the wave shape at the tip of the vane 2 must be a value proportional to the product of the wavelength of the AC voltage and the beam velocity, the period is formed to be longer as the charged beam is accelerated. ing. Therefore, once the vanes 2 are processed, the velocity of the charged beam is determined by the frequency of the alternating voltage. Therefore, in order to change the extraction energy for any charged particle, other than changing the frequency of the alternating voltage. There is no way to do it.

On the other hand, the high frequency power to the accelerating cavity is generated through the loop coupler 5. The magnetic field generated in the loop coupler 5 travels in the chamber partitioned by the vane 2 in the length direction of the acceleration cavity, returns through the end space of the acceleration cavity toward both adjacent chambers. At this time, a strong electric field is generated in the gap between the tip ends of the respective vanes 2 and 2, and electric charges are also induced in the tip end portions of the opposing vanes 2, so that an electric field is also generated at the same time. As a result, the above-mentioned AC voltage is generated between the vanes 2 and 2.

Further, in order to efficiently supply a high frequency wave to the accelerating cavity, the high frequency must match the resonance frequency of the accelerating cavity. In a general electric circuit, this resonance frequency is determined by the product of the capacitance C and the inductance L connected in parallel, and this is given by the following mathematical expression 1. 2πfr = 1 / (LC) ^1/2 (Equation 1)

In the case of this acceleration cavity, the inductance L and the vanes 2 and 2 are equivalently proportional to the cross-sectional area of the chamber.
It can be considered that the capacitance C between is connected in parallel. Therefore, when the frequency of the high frequency is determined, the gap length between the vanes 2 and 2 and the cross-sectional area of the chamber must be determined so that the frequencies of the cavity resonators are equal. Generally, since the gap between the vanes 2 and 2 is determined so that a high electric field can be generated at a voltage as low as possible, the cross-sectional area of the chamber is determined so that the required resonance frequency can be obtained from the capacitance C determined thereby.

That is, in the apparatus shown in FIG. 3, the inductance L, that is, the resonance frequency can be changed by changing the space capacity of the chamber by moving the driving apparatus 4 in and out of the side tuner 3. However, although the inductance L is proportional to the cross-sectional area of the chamber as described above, when the cross-sectional area in the longitudinal direction is not constant as in the present acceleration cavity, the inductance L with respect to the cross-sectional area of the chamber is the one with respect to the space volume. You have to think as. In such a resonance frequency adjusting method by putting the drive unit 4 in and out of the side tuner 3, the variation width of the resonance frequency is about 1% at maximum. In the conventional quadrupole RFQ linear accelerator, the resonance frequency is adjusted in order to match the resonance frequency changed due to the manufacturing error of the accelerating cavity with the set value. In that case, this degree of adjustment is sufficient. ..

[0008]

However, when the above-mentioned conventional quadrupole RFQ linear accelerator is used as the first stage part of a high energy accelerator in nuclear experiments etc., the velocity of the charged beam extracted from this accelerator, that is, the energy is variable. Although it is not necessary to do so, when the conventional quadrupole RFQ linear accelerator is used as a single accelerator such as an ion implanter, it is required to significantly change the energy for the same charged particle. As described above, the linear accelerator has a problem that the adjustment width of the resonance frequency is about 1% at the maximum and cannot be significantly adjusted, so that it is impossible to meet the demand of a single accelerator such as an ion implanter. ..

The present invention has been made to solve the above problems, and an object of the present invention is to provide a quadrupole RFQ linear accelerator capable of arbitrarily changing the energy of the charged beam extracted from the accelerator.

[0010]

The variable energy type RFQ linear accelerator according to claim 1 of the present invention uses the metal plate as a ground electrode along the vicinity of the tips of the electrodes adjacent in the circumferential direction of the resonance cavity to cause the resonance. Provided so that it can move back and forth in the radial direction of the cavity,
It is configured such that the equivalent capacitance in the resonance cavity is increased and moved variably by advancing and retracting each metal plate.

A variable energy type RFQ linear accelerator according to a second aspect of the present invention is configured by dividing the metal plate according to the first aspect of the invention into a plurality of pieces.

[0012]

According to the present invention as set forth in claim 1, the capacitance between electrodes is changed by moving each metal plate forward and backward in the radial direction of the resonance cavity, that is, by changing the resonance frequency. The extraction energy of the charge beam can be changed.

According to the present invention as set forth in claim 2,
The extraction energy of the charge beam from the accelerator can be changed by individually advancing and retracting each metal plate divided in the longitudinal direction.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in FIGS. In each of the drawings, FIG. 1 is a diagram showing an embodiment of a variable energy type RFQ linear accelerator according to the present invention. FIG. 1 (a) is a cross-sectional view in a direction orthogonal to its axial direction, and FIG. FIG. 2A is a cross-sectional view of the variable energy RFQ linear accelerator shown in FIG. 7A taken along the line BB, and FIG. 2 is a view showing another embodiment of the variable energy RFQ linear accelerator of the present invention.
1A is a diagram corresponding to FIG. 1A, and FIG.
(B) It is a corresponding figure.

Example 1. Variable energy type R of this embodiment
As shown in FIGS. 1 (a) and 1 (b), the FQ linear accelerator 10 includes four electrodes (hereinafter referred to as “electrodes”) arranged in a cylindrical resonant cavity 11 at equal intervals in the circumferential direction along the axial direction. , "Vane"
12). The variable energy RFQ linear accelerator 10 uses the four metal plates 13 as ground electrodes along the vicinity of the tip between the four vanes 12, 12 that are adjacent to each other in the circumferential direction of the resonant cavity 11 to cause the resonance. The cavity 11 is provided so as to be movable back and forth in the radial direction, and by moving back and forth each metal plate 13, the equivalent capacitance C in the resonant cavity 11 can be increased and the capacitance C can be changed.

That is, as shown in FIG. 1, each of the metal plates 13 is formed in a channel shape having an L-shaped cross section orthogonal to the axial direction, and the corner portions thereof are adjacent to each other in the circumferential direction of the resonance cavity 11. Each of the vanes 1 is located between the tip portions of the four vanes 12 and 12 and has an elongated surface.
It is parallel to the tip of 1. In addition, each metal plate 13 has two back surfaces penetrating from the outer side to the inner side through two holes 11A, 11A formed on the peripheral surface of the resonance cavity 11 at predetermined intervals in the axial direction. The support rods 14 are fixed to the tips of the rods 14, 14, and the support rods 14 are electrically connected to the resonance cavity 11. A drive mechanism 15 for moving the metal plate 13 in the radial direction is connected to the outer end of each support rod 14. 1
Reference numeral 6 is a loop coupler for supplying high frequency power into the resonance cavity 11.

Thus, the energy emitted from the RFQ linear accelerator 10 is related to the resonance frequency of the acceleration cavity 11 as described above, and this resonance frequency is also applied to each of the vanes 12, 12.
It is related to the capacitance C between the tips. In addition, the capacitance C between the respective vanes 12 is 12
It is inversely proportional to the gap length between 2 and 12. Therefore, in the present embodiment, by operating the respective drive mechanisms 15, the respective metal plates 13 are advanced inward of the resonance cavity 11, and the metal plates 13, 13 facing each other are brought close to each other, so that each vane 12, The gap length between the 12 is reduced equivalently, and the capacitance C between the vanes 12, 12 is increased.
As a result of this operation, the resonance frequency of the acceleration cavity 11 changes, and the emitted energy can be made variable.

Therefore, according to the present embodiment, the energy emitted from the RFQ linear accelerator 10 can be arbitrarily changed by arbitrarily changing the gap length between the metal plates 13 and 13, and the ion implanter can be changed. Etc. can be effectively used as a single accelerator. Further, according to the present embodiment, it is also possible to adjust the electromagnetic field distribution in the acceleration cavity, that is, the resonance cavity 11 by finely adjusting each of the metal plates 13, so that each metal plate 13 serves as a side tuner. Can also play the role of.

Example 2. Variable energy type R of this embodiment
The FQ linear accelerator 10 divides the elongated metal plate 13 in the first embodiment into two at the middle in the longitudinal direction, and
As shown in (a) and (b), two metal plates 13A, 1
3B, the support rod 14 and the drive mechanism 15 are connected to the metal plates 13A and 13B, respectively.
Even if 3A and 13B are operated independently, Embodiment 1
The same action and effect as can be expected.

Example 3. Variable energy type R of this embodiment
The FQ linear accelerator 10 has the same structure as that of the first or second embodiment except that a cooling device (not shown) is provided, and when cooling is required, each metal plate 13 is cooled by this cooling device. It is a thing. This cooling device includes a first cooling pipe arranged along the back surface side of the metal plate 13 and a hollow support rod 14 connected to the first cooling pipe.
A second cooling pipe passing through the inside of the resonance cavity 11. The second cooling pipe is drawn to the outside of the resonant cavity 11, and a cooling medium from the outside is circulated to each cooling pipe to cool the metal plate 13, The temperature rise of the plate 13 and the like can be suppressed.

The present invention is not limited to the above-described embodiment, and any metal plate capable of moving forward and backward in the radial direction is provided in the resonance cavity so that the energy emitted from the accelerator can be varied. For example, all are included in the present invention.

[0022]

As described above, according to the present invention, a metal plate that can be moved forward and backward in the radial direction is provided in the resonance cavity to change the equivalent capacitance in the resonance cavity. It is possible to provide a quadrupole RFQ linear accelerator that can arbitrarily change the energy of the beam.

[Brief description of drawings]

1A and 1B are views showing an embodiment of a variable energy type RFQ linear accelerator according to the present invention, in which FIG. 1A is a sectional view in a direction orthogonal to the axial direction thereof, and FIG. FIG. 4 is a cross-sectional view of the variable energy type RFQ linear accelerator shown in FIG.

2A and 2B are views showing another embodiment of the variable energy type RFQ linear accelerator according to the present invention, wherein FIG. 2A is a view corresponding to FIG. 1A and FIG. 2B is a view corresponding to FIG. Is.

3A and 3B are diagrams showing an example of a conventional variable energy type RFQ linear accelerator, in which FIG. 3A corresponds to FIG. 1A and FIG. 1B corresponds to FIG. 1B.

[Explanation of symbols]

 10 Energy Variable RFQ Linear Accelerator 11 Resonant Cavity 12 Vein (Electrode) 13 Metal Plate 14 Support Rod 15 Drive Mechanism

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[Procedure amendment]

[Submission date] July 9, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (2)

[Claims] 1. An RFQ having four electrodes arranged in a cylindrical resonance cavity at equal intervals in the circumferential direction along the axial direction.
In the linear accelerator, a metal plate is provided as a ground electrode along the vicinity of the tips of the electrodes adjacent to each other in the circumferential direction so as to be able to move forward and backward in the radial direction of the resonance cavity, and the forward and backward movement of each metal plate causes an equivalent in the resonance cavity. Variable energy type RFQ linear accelerator characterized by having a variable capacitance. 2. The variable energy RFQ linear accelerator according to claim 1, wherein the metal plate is divided into a plurality of pieces in the longitudinal direction.