JP2946363B2 - High frequency acceleration focusing device - 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 accelerating focusing device for linearly accelerating and focusing charged particles incident in a quadrupole accelerating focusing electric field.

[0002]

2. Description of the Related Art Conventionally, this kind of high-frequency acceleration focusing apparatus has
As shown in FIG. 3, a conductive outer cylinder 1 having a through hole along a beam acceleration axis B, and a beam is provided in the conductive outer cylinder 1.
And a high-frequency resonator (cavity) constituted by four conductive wings (vanes) 40 arranged at 90-degree intervals from each other around the acceleration axis B, and the high-frequency resonator is excited. And a high-frequency introducing device (not shown) for performing the operation. In this configuration, by introducing a high frequency from the high frequency introducing device to the high frequency resonance device, a quadrupole accelerated focusing electric field is generated on the beam acceleration axis, and the charged particles are accelerated and focused linearly. Such a high-frequency accelerating focusing apparatus is usually provided with an RFQ linac (Radio Frequenc).
y Quaduapole Linac).

[0003] In a high-frequency accelerating and focusing device actually used, as is apparent from FIG.
Numerals 0 are respectively provided inside the conductive outer cylinder portion 1 and are electrically connected to a high-frequency bonding portion (not shown).

[0004] More specifically, four conductive wings 4
Numeral 0 is fixed at a predetermined position on the side surface of the conductive outer cylinder portion 1. For this reason, a plug for fixing each conductive wing portion 40 is provided at a predetermined position of the conductive outer cylinder portion 1, and an adjacent conductive wing portion 40 is provided inside the conductive outer cylinder portion 1.
An electric field adjusting device is provided in the space between the two, which improves the symmetry of the quadrupole electric field, and
It is useful for generating a quadrupole electric field with high flatness along the beam acceleration axis B.

[0005] In the above configuration, the TE of the conductive outer cylinder portion is
_When a resonance mode called ₂₁₀ mode is excited by high-frequency power supplied from the high-frequency introducing device, a high-frequency current flows in the cavity inner surface in a direction perpendicular to the beam acceleration axis. At this time, a high-frequency current having a half-period transition flows to the adjacent conductive wings 40, and a high-frequency voltage of the opposite polarity is applied.
An accelerating focused electric field of the heavy pole is generated.

[0006]

Normally, in the RFQ linac high-frequency accelerating focusing device, a quadrupole accelerating focusing electric field must be generated in the space inside the four conductive wings with good symmetry with respect to the beam acceleration axis. Must. For this reason, adjustment of the mounting position of the four conductive wings requires particularly strict adjustment. Further, a final adjustment of the quadrupole electric field requires an electric field adjusting device, and since this adjustment is performed by changing the projecting volume of the electric field adjusting device, the structure is complicated, complicated, and delicate. Adjustment work is required.

Further, another problem in the conventional RFQ linac is that the symmetry and flatness of the quadrupole electric field are disturbed during acceleration of a large current beam. In the RFQ linac, high-frequency power having the same frequency as the reference vibration (TE ₂₁₀ mode) of the high-frequency resonator used for acceleration focusing is introduced from the high-frequency introduction device, and a high high-frequency voltage is generated in the conductive wing portion, and beam acceleration is performed. An accelerating focused electric field is generated on the shaft. In other words, high-frequency energy is stored in the high-frequency resonator, and this energy is used to accelerate and focus the charged particles.

Here, attention is paid to the balance of the high-frequency energy when the charged particle group (beam) is accelerated in the high-frequency acceleration convergence device. As the beam is accelerated on the acceleration axis, the beam receives energy proportional to its energy increase from the RF acceleration convergence device, and the RF acceleration convergence device loses equal RF energy. Also, the amount of energy lost by the high-frequency acceleration convergence device in this manner is proportional to the beam current value .

[0009] Therefore, it is stored in the high-frequency acceleration convergence device.
High energy that the beam carries away
In the case of accelerating a relatively large current beam whose wave energy is not negligible, a region where the amount of high-frequency energy is locally reduced occurs on the beam acceleration axis, causing non-uniformity of the amount of high-frequency energy. Such non-uniformity in the amount of high-frequency energy increases with time, causing disturbance in the symmetry and flatness of the accelerating electric field, and consequently, lowering the acceleration performance. Therefore, the conventional R
In the FQ linac, there is a problem that the performance tends to deteriorate when a beam of a relatively large current is accelerated.

[0010] These problems become more serious as the tube length L of the conductive outer tube portion becomes longer than the space free wavelength λ. This is because the degree of symmetry and flatness of the quadrupole accelerating focused electric field is disturbed by the structural variation of the conductive outer cylinder and the conductive wing, especially the variation in dimensions and mounting positions, and the degree of instability of the electric field. Is increased in proportion to (L / λ) ² . As described above, as the cylinder length L becomes longer, it is difficult to achieve a quadrupole electric field having high symmetry and flatness by adjustment. The fundamental cause of the problem is that in the conventional RFQ linac, in the high-frequency acceleration focusing device, Is that the TE ₂₁₀ mode in which the group velocity (propagation velocity of high-frequency energy) is almost zero.

An object of the present invention is to provide a high-frequency accelerating and focusing apparatus capable of generating a quadrupole accelerated and focused electric field having high stability and good symmetry regardless of the length of the conductive outer cylinder. To provide. It is another object of the present invention to provide a high-frequency acceleration focusing device that can easily adjust a quadrupole electric field.

[0012]

According to the present invention, in a resonance device having a large group velocity, high-frequency energy propagates from a relatively high-frequency energy region to a low-frequency region, so that a high electric field stability can be realized. , The high-frequency acceleration focusing device is configured so that the group velocity in the beam acceleration axis direction is not zero.

More specifically, according to the present invention, a cylindrical conductive outer cylindrical portion having a space defining a passage hole inside along the beam acceleration axis, and the conductive outer cylindrical portion includes: Passing
Are spaced apart from each other across the hole,
A conductive metal plate fixed to the cylindrical portion, and the conductive metal plate
A conductive wing positioned so as to surround the passage hole, and the conductive metal plates and the conductive wing are connected therebetween.
And a plurality of resonant cells constituted by
Are arranged along the beam acceleration axis, while
Exciting the vibration cells and including the through holes in each of the resonance cells
A high frequency introduction device for generating a quadrupole electric field in a space , wherein the high frequency introduction device excites the plurality of resonance cells in a resonance mode in which at least one node is formed in a direction of the beam acceleration axis. A high-frequency acceleration focusing device characterized by the above feature is obtained.

[0014]

According to the present invention, the beam acceleration axis, TE _11N mode to form at least one section - have together using de, a configuration that combines multiple resonant cells to the beam acceleration axis direction, the resonance Since the RF energy is easily transmitted between the cells, the quadrupole electric field has high stability, and the symmetry and flatness of the quadrupole electric field are not disturbed even when the cylinder length is increased.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The high frequency accelerating and focusing apparatus according to the present invention will be described in detail below, taking an example using a TE ₁₁₂ mode as an embodiment. FIGS. 1 and 2A, 2B, and 2C are views showing a high-frequency acceleration focusing apparatus according to one embodiment of the present invention.

As shown in the drawing, the high-frequency acceleration focusing apparatus includes a cylindrical conductive outer cylinder portion 100 having a through hole extending along a beam acceleration axis B. In the conductive outer cylindrical portion 100, three pairs of conductive metal plates (ridges) 2A and 2B facing each other with a space therebetween with respect to the beam acceleration axis B,
2C and 2D, 2E and 2F are arranged along the beam acceleration axis B, and these conductive metal plate pairs 2A and 2B, 2C and 2D, 2E and 2F are fixed to the conductive outer cylinder part 100, respectively. In other words, in this embodiment, three pairs of conductive metal plates protrude into the outer cylindrical portion 100 from two opposite directions in the beam acceleration axis direction. The conductive metal plate pairs 2A and 2B are a first set of conductive metal plates, the conductive metal plate pairs 2C and 2D are a second set of conductive metal plates, and the conductive metal plate pairs 2E and 2F are a third set. Of the conductive metal plate.
In addition, a gap is provided between the conductive metal plates of each set along the direction of the beam acceleration axis B. Further, the conductive metal plates 2A, 2C, and 2E provided on the upper side of the drawing are provided. The conductive metal plates 2B, 2D, and 2F provided on the lower side are also disposed linearly.

As best shown in FIGS. 2B and 2C, conductive metal plate pairs 2A and 2B, 2C and 2
In the space between D, 2E and 2F, the beam acceleration axis B
, Four conductive wings 4A to 4D are arranged at an angular interval of 90 degrees from each other, and each conductive wing 4A to 4D extends along the beam acceleration axis B. .

Here, one conductive metal plate 2A of the first set of conductive metal plates is, as shown in FIGS. 2B and 2A, a pair of semi-circular conductive metal plates. The conductive metal plate 2B is connected to the conductive wings 4B and 4D facing each other by the conductive insert 3B, while the conductive metal plate 2B is connected to the remaining conductive wings by a pair of semicircular conductive inserts 3A. Parts 4A and 4C
It is connected to the. The first conductive metal plates 2A and 2B, the conductive inserts 3A and 3B, and the conductive wings 4A to 4D form a first resonance cell.

As is clear from FIGS. 2C and 2A, the conductive metal plate 2C of the second set of conductive metal plates has a pair of semicircular conductive insertion portions 3C. Are connected to the conductive wing portions 4A and 4C facing each other, and one conductive metal plate 2D is connected to a pair of conductive insertion portions 3D.
Thus, the second conductive cell is connected to the remaining conductive wings 4B and 4D, thereby forming a second resonance cell. Further, similarly to the first set of conductive metal plates, the third set of conductive metal plates 2E and 2F are connected to the conductive wing portions 4A to 4D via semicircular conductive inserts 3E and 3F. Thus, a third resonance cell is configured.

An electric field adjusting means for adjusting an electric field, that is, a tuner 7 is provided in a gap between adjacent conductive metal plates.

When the RFQ linac having such a configuration is excited in a TE ₁₁₂ mode by a high frequency supplied from a high frequency introducing device (not shown), FIG.
As shown in (B) and (C), a high-frequency current flows on the surfaces of the conductive metal plates 4A to 4D. That is, high-frequency currents flow in mutually opposite directions in the resonance cells adjacent to each other. However, the connection relation between the conductive wings 4A to 4D and the pair of conductive metal plates in the adjacent resonance cells by the conductive insertion portions is reversed. Therefore,
High-frequency voltages as shown in FIGS. 2B and 2C are generated in the conductive wings 4A to 4D. As is clear from FIG. 2B, adjacent conductive wings of the first resonance cell include:
Voltages of opposite polarities are generated, which causes the beam acceleration axis surrounded by the conductive wings 4A to 4D to have 4
A dipole electric field is generated. On the other hand, a high-frequency voltage having the same polarity as that of the conductive wings 4A to 4D of the first resonance cell is also applied to the conductive wing of the second resonance cell, and a quadrupole electric field is generated on the beam acceleration axis. This is the same in the third resonance cell.

As described above, the conductive wings, 4A and 4C, and 4B and 4D, which face each other, have the conductive insertion portions (3A).
And 3C, 3F and 3B, 3D and 3E),
They are electrically short-circuited and the potentials at both are always equal. The polarities of potentials applied to adjacent conductive wings are opposite to each other, and the potentials have the same absolute value. Therefore, a quadrupole electric field with good symmetry can be generated at an arbitrary position on the beam acceleration axis. still,
The direction of the high-frequency current and the polarity of the high-frequency voltage shown in FIGS. 2A, 2B, and 2C are inverted every half cycle of the high frequency.

Further, in the illustrated example, three resonance cells are arranged in the beam acceleration axis direction, and are excited in a resonance mode having two nodes in the electric field distribution in the beam acceleration axis direction. In such a resonance mode, the group velocity in the beam acceleration axis direction is large, and the electric field stability in the beam acceleration axis direction can be increased. Even if a beam load or the like is present, high-frequency energy can easily be transmitted between the resonance cells, so that the electric field flatness in the beam acceleration axis direction is maintained.

In the space between the conductive metal plates 2A, 2D, 2E and the conductive metal plates 2B, 2D, 2F in the direction along the beam acceleration axis B in the conductive outer cylinder portion 100, A plurality of tuners 7 are provided. The tuner 7 forms a coupled resonance circuit of the resonance cells, and the frequency can be corrected by adjusting the protrusion amount of the tuner 7.

[0025]

As described above, according to the present invention, TE _11N
Is used, a quadrupole electric field with good symmetry can be generated, the group velocity can be increased, and the stability of the electric field in the beam acceleration axis direction can be improved. Also,
The frequency can be corrected with a small number of tuners without adversely affecting the uniformity of the electric field. Further, according to the present invention, it is extremely easy to generate a uniform quadrupole electric field even when the conductive outer cylinder is long.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a basic configuration of a high-frequency acceleration focusing apparatus according to an embodiment of the present invention, with a part thereof cut away.

FIG. 2 is a diagram shown for explaining electric flux lines of a high-frequency current in each part of FIG. 1;

FIG. 3 shows a basic configuration of a conventional high-frequency acceleration focusing device;
FIG.

FIG. 4 is a view for explaining a cross section of the high-frequency acceleration focusing apparatus shown in FIG. 3;

[Explanation of symbols]

 1,100 conductive outer cylinder part 2A to 2F conductive metal plate 3A to 3F conductive insertion part 4A to 4D, 40 conductive wing part 7 tuner

Claims (2)

(57) [Claims] A cylindrical conductive outer cylindrical portion having a space defined inside a passage hole along a beam acceleration axis ;
In the outer cylinder part, they are spaced from each other with the passage hole
And a conductive metal plate fixed to the conductive outer cylinder portion, between the conductive metal plate and surrounding the passage hole.
A conductive wing portion positioned thereon, and each of the conductive metal plates
Structure by a conductive insertion member for connecting the conductive blade portion and
A plurality of formed resonance cells are arranged along the beam acceleration axis.
While arranging, the respective resonance cells are excited and the respective resonance cells are excited.
A quadrupole electric field in the space containing the passage hole in the
A plurality of resonance cells are excited in a resonance mode in which at least one node is formed in the direction of the beam acceleration axis by the high-frequency introduction device. . 2. The method according to claim 1, wherein the resonance mode is T
E _11N (where N is a natural number).