JP2022073477A - High Frequency Accelerator Cavity and High Frequency Accelerator System - Google Patents

Abstract

To obtain a high-frequency accelerator cavity and a linear accelerator system that can suppress gas leakage and gas permeation from a seal portion of a metal seal, maintain a high degree of ultimate vacuum, and achieve stable operation for a long period of time.SOLUTION: In a high-frequency accelerator cavity 1, a metal seal 55 which is a vacuum-sealing member is arranged on the contact surface between constituent members 11, 12, and 13 of the high-frequency accelerator cavity 1 divided by a plane parallel to the acceleration axis of charged particles.SELECTED DRAWING: Figure 2

Description

Embodiments of the present invention relate to high frequency accelerating cavities and high frequency accelerator systems.

Generally, to accelerate charged particles, acceleration by an electrostatic field or acceleration by a high-frequency electric field is used.

Acceleration by a high-frequency electric field requires that the part where particles pass and are accelerated must be in a vacuum state. Further, it is important to reduce the power loss in the resonance cavity of the high frequency power from the viewpoint of power efficiency and heat generation of the resonance cavity.

High-frequency acceleration cavities such as RFQ (Radio Frequency Quadrupole Linac) and DTL (Drift Tube Linac) are used as ion accelerators using high-frequency electric fields.

As one of the manufacturing methods of this RFQ, an example in which an O-ring is used to vacuum-seal between the parts when connecting the parts of the high-frequency acceleration cavity is described.

Japanese Unexamined Patent Publication No. 2011-86494.

In the above-mentioned high-frequency acceleration cavity, since the vacuum is sealed by the O-ring, there is a problem that the ultimate vacuum degree is lowered due to the leakage or permeation of gas from the O-ring. Further, the O-ring may be deteriorated in a short time depending on the material, and there is a problem that it is difficult to use the O-ring for a long period of time.

The high-frequency accelerating cavity according to the above embodiment is a high-frequency accelerating cavity for accelerating charged particles, and the contact surface between the constituent members of the high-frequency accelerating cavity divided by a plane parallel to the acceleration axis of the charged particles is vacuum-sealed. It is characterized in that a metal seal which is a stopping member is arranged.

Further, the high frequency accelerator system according to the above embodiment is characterized in that the high frequency accelerating cavity is excited by using a semiconductor amplifier.

The embodiment of the present invention has been made to solve the above-mentioned problems, and can suppress gas leakage and gas permeation from the seal portion of the metal seal to maintain a high ultimate vacuum degree for a long period of time. It is possible to obtain a high-frequency acceleration cavity and a high-frequency accelerator system capable of stable operation.

The perspective view of the high frequency acceleration cavity which concerns on this invention. The schematic perspective view which cut the high frequency acceleration cavity in line AA in FIG. The schematic perspective view of the central member shown in FIG. The schematic perspective view of the side member shown in FIG. In the metal seal shown in FIG. 2, (a) is a side sectional view, and (b) is a schematic sectional view cut along the line BB of (a). Schematic block diagram of the high frequency accelerator system according to the present invention.

(Example 1)
Hereinafter, the high frequency acceleration cavity 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 5. In the drawings, the same parts are designated by the same reference numerals, and the description of the configuration will be omitted as appropriate.

FIG. 1 is a perspective view of the high frequency acceleration cavity 1 in the present embodiment. The high frequency acceleration cavity 1 has a tubular portion 2 formed in a cylindrical shape. The high-frequency acceleration cavity 1 projects inward from the tubular portion 2 and is provided with electrodes 21 to 24 called vanes. Each of the electrodes 21 to 24 is electrically connected to the tubular portion 2.

The high frequency acceleration cavity 1 in the present embodiment includes a first electrode 21, a second electrode 22, a third electrode 23, and a fourth electrode 24. The four electrodes 21 to 24 in the present embodiment are integrally formed with a member constituting the tubular portion 2, and each of the electrodes 21 to 24 is along the extending direction 100 of the acceleration axis of the charged particles. It is formed to extend.

The electrodes 21 to 24 are formed in a triangular columnar shape having a triangular cross section, and each of the electrodes 21 to 24 is formed so that the apex of the triangle having a cross section is directed toward the acceleration axis of the charged particles. The tip portion of each of the electrodes 21 to 24 toward the acceleration axis is formed with a corrugated end in order to form an electric field that accelerates and focuses the charged particles in the direction of the acceleration axis. The shape of the electrodes 21 to 24 is not limited to this form, and any shape that protrudes from the tubular portion 2 and the tip of the electrodes 21 to 24 is close to the acceleration axis can be adopted. For example, the electrode may be formed in a plate shape.

The high frequency acceleration cavity 1 includes a power supply device for supplying high frequency power. This power supply has a high frequency generator connected to a pre-stage amplifier and a main amplifier (not shown). The high frequency power generated by the high frequency generator is amplified by the pre-stage amplifier and the main amplifier. The high frequency power output from the main amplifier is supplied to the high frequency acceleration cavity 1 via the coupler. The power supply device is not limited to this form, and any device capable of supplying high frequency power to the high frequency acceleration cavity 1 can be adopted.

The high frequency acceleration cavity 1 has stray capacitance and stray inductance depending on the shape of the cylindrical portion 2 and the respective electrodes 21 to 24. These stray capacitances and stray inductances form part of an electrical circuit. An accelerating electric field is formed by supplying high-frequency power to the high-frequency accelerating cavity 1. When the electromagnetic field of TE210 mode or TE211 mode suitable for the quadrupole accelerator is excited, the respective voltages of the first electrode 21, the second electrode 22, the third electrode 23 and the fourth electrode 24 ( The absolute value) is the same, and the electrode pair of the first electrode 21 and the second electrode 22 facing each other and the electrode pair of the third electrode 23 and the fourth electrode 24 facing each other are mutually opposite. It has the opposite polarity (plus or minus). The acceleration shaft is arranged in a space sandwiched between the four electrodes 21 to 24. Charged particles move while being accelerated along the acceleration axis.

FIG. 2 is a perspective view when the high frequency acceleration cavity 1 is cut along the line AA in FIG. The arrow 100 is the direction in which the acceleration axis of the charged particle extends. The high-frequency acceleration cavity 1 in the present embodiment is formed so as to extend in parallel with the extending direction 100 of the acceleration axis.

In FIGS. 1 and 2, the high-frequency acceleration cavity 1 in the present embodiment is divided by a plane parallel to the acceleration axis of the charged particles, and the central member 11 including the first electrode 21 and the second electrode 22 and the third. It includes three constituent members, a first side member 12 including an electrode 23 and a second side member 13 including a fourth electrode 24.

The first side member 12 is arranged on one side of the central member 11. The second side member 13 is arranged on the other side of the central member 11. Each of the central member 11, the first side member 12, and the second side member 13 in the present embodiment is integrally formed from one member. That is, the central member 11 and the side members 12, 13 are made of one material without having a joining line, a welding line, or the like of a plurality of parts. In addition, an additional member such as a vacuum port may be arranged in advance on the central member 11 or the side member 12.

The central member 11, the first side member 12, and the second side member 13 are fastened and fixed to each other by a fixing member using a bolt 51 and a nut 52.

A metal seal 55, which will be described later, is arranged as a vacuum sealing member on the contact surface between the central member 11 and the first side member 12 and the contact surface between the central member 11 and the second side member 13. ing. The high frequency acceleration cavity 1 is sealed by arranging the vacuum sealing member between the respective constituent members.

FIG. 3 shows a schematic perspective view of the central member 11 in the present embodiment.

The central member 11 has a central outer frame portion 11a that constitutes a central portion of the outer frame portion of the high frequency acceleration cavity 1. The central outer frame portion 11a is formed in an annular shape when viewed in a plan view. The central member 11 has a first electrode 21 and a second electrode 22 protruding inward from the central outer frame portion 11a. The first electrode 21 and the second electrode 22 are arranged so that the tip portions thereof face the acceleration axis.

Of the outer surface of the central member 11, an incident port 61 on which charged particles are incident is formed on the end surface in the direction of the acceleration axis. Further, an exit port 62 from which charged particles are emitted is formed on the end surface opposite to the end surface on which the incident port 61 is formed. The entrance port 61 and the exit port 62 are formed on an extension of the acceleration axis.

A through hole 14 for passing the bolt 51 is formed in the central outer frame portion 11a. A plurality of through holes 14 are formed along the shape of the central outer frame portion 11a. A recess 16 for arranging the metal seal 55 is formed on the contact surface of the central outer frame portion 11a that comes into contact with the first side member 12 or the second side member 13. The recess 16 is formed in a closed shape when viewed in a plan view. Needless to say, the recess 16 for arranging the metal seal 55, which is a vacuum sealing member, may be arranged in the first side member 12 and the second side member 13.

The central member 11 is formed with a reference mark 31 for determining the positions of the members in the assembly process of assembling each member. The reference mark 31 is formed linearly on the end face where, for example, the entrance port 61 and the exit port 62 are formed.

FIG. 4 shows a schematic perspective view of the side member 12 in the present embodiment.

The first side member 12 has a first side outer frame portion 12a that constitutes a side portion of the outer frame portion of the high frequency acceleration cavity 1. The first lateral outer frame portion 12a is formed in an annular shape when viewed in a plan view. The first side member 12 has a first wall portion 12b having the shape of a part of the acceleration cavity. The first wall portion 12b constitutes the tubular portion 2 of the acceleration cavity 1. The first wall portion 12b is formed so as to extend outward from the first lateral outer frame portion 12a. The first wall portion 12b is formed in a plate shape and is connected to the first lateral outer frame portion 12a. The first side member 12 has a third electrode 23 projecting inward from the first wall portion 12b.

A through hole 15 for passing the bolt 51 is formed in the first side outer frame portion 12a. The first side outer frame portion 12a is formed with an alignment mark 32 for determining an assembly position in the assembly process. In the present embodiment, the alignment marks 32 are formed on both end faces in the direction of the acceleration axis in the end faces of the first lateral outer frame portion 12a.

In FIG. 4, the first side member 12 of the two side members is taken as an example for explanation, but the second side member 13 has the same configuration as the first side member 12. Have. The second side member 13 has an annular second side outer frame portion 13a, which extends outward from the second side outer frame portion 13a and is a part of the high frequency acceleration cavity 1. A second wall portion 13b having the shape of is formed. The second side member 13 is provided with a fourth electrode 24 that projects inward from the second wall portion 13b.

In the high frequency acceleration cavity 1 of the present embodiment, the central outer frame portion 11a, the first side outer frame portion 12a, and the second side outer frame portion 13a are fixed to each other by bolts 51 and nuts 52, and a metal seal is provided. It is closely configured by 55 to form an outer frame portion of the acceleration cavity 1.

The metal seal 55 will be described with reference to FIG. 5 (a) is a side sectional view of the metal seal 55, and FIG. 5 (b) is a schematic sectional view cut along the line BB of FIG. 5 (a).

In FIG. 5, as the metal seal 55, a metal spring 56 is incorporated and integrated, and a metal seal material 58 having a metal coating 57 and a C-shaped cross section is processed so as to fit into the recess 16 shown in FIG. It is composed.

Further, even if the metal sealing material 58 does not have a C-shaped cross section, it has a built-in metal spring 56 and is covered with a metal coating 57, or at least one of the inner and outer surfaces is formed of the metal coating 57. The configuration using 55 may be used. Further, the metal seal 55 may have a configuration in which a spring force is applied only to the C-shaped metal coating 57 without the metal spring 56.

The metal coating 57 has a double structure of an outer skin and an endodermis, and the outer skin may be formed of a metal such as silver, aluminum, indium, or copper, which is a soft metal having good electrical conductivity.

Further, as the metal seal 55, a rod-shaped metal such as silver, aluminum, indium, or copper, which is a soft metal having good electrical conductivity, may be used. By adopting such a metal seal material, since the metal seal 55 is made of metal, it is possible to secure electrical contact between the constituent members of the high frequency acceleration cavity 1, and there is an advantage that it is not necessary to arrange the metal spring 56.

Then, in order to apply a uniform tightening force over the entire circumference of the metal seal 55, the spacing p of the through holes 14 which are bolt holes is set so that all the flange joint surfaces which are the contact surfaces between the constituent members of the high frequency acceleration cavity 1 are compressed. Therefore, if the nominal diameter of the bolt is d and the thickness of the plate to be tightened is t, it is set as in the equation (1).

(Number 2)
p <1.52d + 2t ... (1)

If the interval p of the through holes 14 is equal to or less than the value obtained on the right side of the equation (1), the uniformity of the tightening force increases, which is effective.

In the present embodiment configured as described above, in the high-frequency acceleration cavity 1 vacuum-sealed using the metal seal 55, gas leakage and gas permeation from the seal portion of the metal seal 55 can be suppressed and the ultimate vacuum can be suppressed. It is possible to keep the degree high. In addition, since it is a metal seal, there is almost no deterioration, so stable operation for a long period of time is possible.

According to the present embodiment, by adopting a metal seal as the vacuum sealing material, it is possible to prevent gas leakage and gas permeation from the sealing portion for a long period of time and maintain a high degree of ultimate vacuum.

(Example 2)
Next, Example 2 will be described with reference to FIG. FIG. 6 is a schematic block diagram of the linear accelerator system according to the present embodiment.

In FIG. 6, the high-frequency accelerator system 70 is composed of an ion source 71, which is a particle generation source for generating charged particles, an RFQ73 using the high-frequency acceleration cavity 1 shown in the first embodiment, and two DTL74s. The RFQ73 and the two DTL74s are configured to be excited by supplying high frequency power by a semiconductor amplifier (AMP) which is an RFQ high frequency power supply 73a and a DTL high frequency power supply 74a, respectively.

The RFQ73 using a semiconductor amplifier can maintain a high degree of ultimate vacuum without gas leakage or permeation. Further, since the metal seal 55 does not deteriorate, stable operation for a long period of time is possible. Further, by exciting using the RFQ high frequency power supply 73a and the DTL high frequency power supply 74a, which are semiconductor amplifiers, it is not necessary to replace the conventional vacuum tube periodically, and the maintainability can be improved.

In the high-frequency accelerator system according to the present embodiment configured as described above, stable operation for a long period of time is possible and maintainability can be improved.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention.

These embodiments can be implemented in various other embodiments, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention.

These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1 ... High frequency accelerator cavity, 2 ... Cylindrical part, 11 ... Central member, 11a ... Central outer frame part, 12 ... First side member, 12a ... First side outer frame part, 12b ... First wall Part, 13 ... second side member, 13a ... second side outer frame part, 13b ... second wall part, 14 ... through hole, 16 ... recess, 21 ... first electrode, 22 ... second Electrode, 23 ... 3rd electrode, 24 ... 4th electrode, 31 ... Reference mark, 32 ... Alignment mark, 51 ... Bolt, 52 ... Nut, 55 ... Metal seal, 56 ... Metal spring, 57 ... Metal coating , 58 ... Metal sealant, 61 ... Incident port, 62 ... Exit port, 70 ... High frequency accelerator system, 71 ... Ion source, 73 ... RFQ (high frequency quadrupole linear accelerator), 73a ... RFQ high frequency power supply, 74 ... DTL (Drift tube linear accelerator), 74a ... DTL high frequency power supply, 75 ... beamline, 100 ... direction in which the acceleration axis of charged particles extends.

Claims (8)

In a high frequency accelerating cavity that accelerates charged particles
A high-frequency acceleration cavity characterized in that a metal seal, which is a vacuum-sealing member, is arranged on a contact surface between constituent members of the high-frequency acceleration cavity divided by a plane parallel to the acceleration axis of the charged particles. The high-frequency acceleration cavity according to claim 1, wherein the metal seal has a structure integrated by using a metal seal material having a built-in metal spring. The high-frequency acceleration cavity according to claim 2, wherein the metal sealing material has a metal film formed on at least one surface of an inner surface or an outer surface. The high frequency acceleration cavity according to claim 1, wherein the metal seal is made of one member selected from rod-shaped silver, aluminum, indium, and copper. The high-frequency acceleration cavity according to any one of claims 1 to 4, wherein the cavity member of the high-frequency acceleration cavity is fastened with bolts and nuts and fixed to each other. The high-frequency acceleration cavity according to claim 5, wherein the interval p of the through holes through which the bolt penetrates is set by the equation (1), where d is the nominal diameter of the bolt and t is the thickness of the plate to be tightened.
(Number 1)
p <1.52d + 2t ... (1) A high-frequency accelerator system according to any one of claims 1 to 6, wherein the high-frequency accelerator cavity is excited by using a semiconductor amplifier. The high-frequency accelerator system according to claim 7, wherein a particle generation source for generating charged particles is connected to the high-frequency acceleration cavity.

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