阅读说明：本技术 回旋加速器 (Cyclotron ) 是由 森江孝明 樋口晃人 于 2020-08-26 设计创作，主要内容包括：本发明提供一种提高磁通道的位置精确度的回旋加速器。回旋加速器(1)利用旋绕轨道(B)对带电粒子进行加速来射出带电粒子线,其具备：磁极(21、23),产生用于对带电粒子进行加速的磁场；及磁通道部(61),具有磁通道(9B),该磁通道(9B)配置在旋绕轨道(B)的外周部且将带电粒子线引导至引出轨道(F),并且使带电粒子线聚焦,磁通道部(61)安装在磁极(21)上,且能够调整磁通道(9B)相对于该磁极(21)的相对位置。(The invention provides a cyclotron which improves the position accuracy of a magnetic tunnel. A cyclotron (1) which accelerates charged particles by a convoluted orbit (B) and emits a charged particle beam, comprising: magnetic poles (21, 23) that generate a magnetic field for accelerating charged particles; and a magnetic tunnel part (61) having a magnetic tunnel (9B), wherein the magnetic tunnel (9B) is arranged on the outer periphery of the convoluted orbit (B), guides the charged particle beam to the extraction orbit (F), focuses the charged particle beam, and the magnetic tunnel part (61) is mounted on the magnetic pole (21), and can adjust the relative position of the magnetic tunnel (9B) relative to the magnetic pole (21).)

1. A cyclotron that accelerates charged particles using a orbit to emit a charged particle beam, comprising:

a magnetic pole generating a magnetic field required for accelerating the charged particles; and

a magnetic tunnel section having a magnetic tunnel which is disposed on an outer peripheral portion of the orbiting track, guides the charged particle beam to a lead-out track, and focuses the charged particle beam,

the magnetic channel part is arranged on the magnetic pole.

2. The cyclotron of claim 1,

the magnetic tunnel part can adjust the relative position of the magnetic tunnel relative to the magnetic pole.

3. The cyclotron of claim 1,

the magnetic tunnel part comprises:

a radial positioning portion that positions a relative position of the magnetic tunnel with respect to the magnetic pole in a radial direction of the magnetic pole; and

a circumferential positioning portion that positions a relative position of the magnetic tunnel with respect to the magnetic pole in a circumferential direction of the magnetic pole.

Technical Field

The present application claims priority based on japanese patent application No. 2019-155843, applied on 28/8/2019. The entire contents of this japanese application are incorporated by reference into this specification.

The present invention relates to a cyclotron.

Background

Conventionally, as a technique in this field, a cyclotron described in the following patent document 1 is known. The cyclotron is provided with a magnetic tunnel for focusing and transferring charged particle lines to an extraction orbit. A position adjusting mechanism of the magnetic channel is provided outside the acceleration space of the charged particles, and the position adjusting mechanism is held by, for example, a frame of the vacuum vessel. The position adjusting mechanism extends in the radial direction on the outer peripheral side of the acceleration space, and a magnetic tunnel is attached to an end portion on the inner peripheral side of the position adjusting mechanism. That is, the magnetic tunnel is held by, for example, a frame of the vacuum chamber via the position adjustment mechanism.

Patent document 1: japanese Kokai publication Sho 62-012299

Disclosure of Invention

However, in order to accurately generate a prescribed magnetic gradient, such a magnetic tunnel needs to be accurately positioned at its installation position. The present invention is directed to a cyclotron in which the positional accuracy of a magnetic tunnel is improved.

The cyclotron of the present invention is a cyclotron that accelerates charged particles using a convoluted orbit to emit a charged particle beam, and includes: a magnetic pole generating a magnetic field required for accelerating charged particles; and a magnetic tunnel part having a magnetic tunnel which is disposed on an outer peripheral portion of the orbiting track, guides the charged particle beam to the extraction track, and focuses the charged particle beam, the magnetic tunnel part being attached to the magnetic pole, and the magnetic tunnel part being capable of adjusting a relative position of the magnetic tunnel with respect to the magnetic pole.

The magnetic tunnel portion may have: a radial positioning portion that positions a relative position of the magnetic tunnel with respect to the magnetic pole in a radial direction of the magnetic pole; and a circumferential positioning portion that positions a relative position of the magnetic tunnel with respect to the magnetic pole in a circumferential direction of the magnetic pole.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a cyclotron in which the positional accuracy of the magnetic tunnel is improved.

Drawings

Fig. 1 is a plan view of the interior of a cyclotron according to the present invention.

Fig. 2 is a schematic view of a pair of magnetic poles provided in the cyclotron of fig. 1.

Fig. 3 is a perspective view of the magnetic tunnel.

Fig. 4 is a plan view showing the end of the magnetic pole.

Description of the symbols

1-cyclotron, 9A, 9B-magnetic channel, 9C, 9D-diamagnetic channel, 21, 23-magnetic pole, 61-magnetic channel portion, 65-theta positioning member (circumferential positioning portion), 67-pin (circumferential positioning portion), 73, 75-R positioning portion (radial positioning portion), B-orbit, F-outgoing orbit.

Detailed Description

Hereinafter, embodiments of the magnetic tunnel and the cyclotron according to the present invention will be described in detail with reference to the drawings. In the cyclotron 1 of the present embodiment, the spiral orbit B of the charged particles is considered to be on a horizontal plane. The orbit B of the cyclotron of the present invention may be disposed on a vertical plane.

As shown in fig. 1, the cyclotron 1 has a vacuum vessel 3, Dee electrodes 5A and 5B, an electrostatic bias plate 90, and a magnetic tunnel 9. The vacuum vessel 3 is a vessel for maintaining an acceleration space of charged particles in a high vacuum state. A pair of magnetic poles 21 and 23 for forming a magnetic field necessary for particle acceleration are provided in the vacuum chamber 3. The magnetic poles 21 and 23 are circular in plan view and have a vertically symmetrical shape with respect to the median plane, which is the acceleration plane. The magnetic poles 21 and 23 are arranged so as to face each other in the vertical direction (direction perpendicular to the paper surface of fig. 1) with the orbit B of the charged particle interposed therebetween. Coils are arranged around the respective magnetic poles 21, 23, and a magnetic field is generated between the magnetic pole 21 and the magnetic pole 23.

Fig. 2 is a perspective view schematically showing only the magnetic poles 21 and 23. As shown, the magnetic poles 21, 23 are cylindrical. The terms "radial direction" and "circumferential direction" used hereinafter denote the profile shapes of the magnetic poles 21, 23 as viewed from the direction of fig. 1, that is, the radial direction and the circumferential direction of a circle. The upper surface of the magnetic pole 21 is formed with 4 convex portions 21a and 4 concave portions 21b that are spirally curved and alternately arranged in the circumferential direction. Also, 4 convex portions 23a and 4 concave portions 23b, which are spirally curved, are alternately arranged and formed in the circumferential direction on the lower surface of the magnetic pole 23. The convex portion 21a and the convex portion 23a, and the concave portion 21b and the concave portion 23b are arranged with a gap therebetween so as to be plane-symmetric with respect to the median plane.

Here, the convex portions 21a and 23a of the magnetic poles 21 and 23 are portions that protrude toward the median plane, and the concave portions 21b and 23b are portions that are recessed so as to be away from the median plane. The median plane is a plane on which the orbit B for accelerating the charged particle beam is located. Strictly speaking, since the charged particle beam travels while vibrating in the direction in which the magnetic poles 21 and 23 face each other (the vertical direction in fig. 2), a plane that is substantially the median of the positions of the vibrating charged particle beam in the direction in which the magnetic poles 21 and 23 face each other becomes the median plane. The shapes of the convex portions 21a and 23a and the concave portions 21b and 23b are not limited to the above-described spirally curved shapes, and may be fan-shaped.

Between the magnetic pole 21 and the magnetic pole 23, a peak region 25h of a narrow gap sandwiched between the convex portion 21a and the convex portion 23a and a valley region 25v of a wide gap sandwiched between the concave portion 21b and the concave portion 23b are formed. A spiral orbit B of the charged particles is formed on the symmetric surface of the magnetic poles 21 and 23.

The DEE electrodes 5A and 5B are electrodes that generate an electric field for accelerating charged particles inside the vacuum chamber 3. Both the DEE electrodes 5A and 5B are disposed in the valley region 25v and are disposed so as to radially face each other. The DEE electrodes 5A and 5B are formed in a shape along the valley region 25v in a plan view. A deflector 11 for deflecting charged particles transferred from an ion source (not shown) provided outside or inside the cyclotron 1 and transferring the deflected charged particles to the median plane is disposed in the center of the magnetic pole 21. However, in the case of an internal ion source, charged particles appear on the median plane, and thus the deflector 11 is not provided.

The electrostatic deflector 90 has a function of deflecting charged particles that have convoluted on the convoluted track B in a magnetic field and extracting the particles to the extraction track F. As the magnetic tunnel 9, 4 magnetic tunnels 9A and 9B and diamagnetic tunnels 9C and 9D are provided.

The magnetic tunnels 9A and 9B have both a function of focusing the charged particle beam in the horizontal direction by a predetermined magnetic field gradient and a function of guiding and transferring the charged particle beam to the extraction orbit F by weakening the average magnetic field itself. The "horizontal direction" as a direction in which the magnetic tunnels 9A and 9B focus the charged particle beam means a substantially radial direction, and more strictly, a direction orthogonal to a traveling direction of the charged particle beam and orthogonal to a facing direction of the magnetic poles 21 and 23. The magnetic tunnel 9A is disposed at a position corresponding to the outermost peripheral portion of the orbiting track B in a plan view. The magnetic tunnel 9B is provided apart from the magnetic tunnel 9A toward the downstream side on the orbit B of the charged particles. Magnetic tunnel 9B is located outside magnetic poles 21 and 23 in a plan view.

The diamagnetic path 9C is disposed at a position substantially symmetrical to the magnetic path 9A with respect to the center position of the magnetic pole 21 (for example, the position of the deflector 11). Similarly, the diamagnetic tunnel 9D is disposed at a position substantially symmetrical with respect to the magnetic tunnel 9B with reference to the central position of the magnetic pole 21. By providing the demagnetizing channels 9C and 9D with respect to the magnetic channels 9A and 9B as described above, double symmetry (two-fold symmetry) of the magnetic field around the track B can be ensured.

In the cyclotron 1, a magnetic field is generated between the magnetic poles 21 and 23, and a high-frequency voltage is applied to the DEE electrodes 5A and 5B, whereby charged particles travel on a spiral orbit B on the median plane while being accelerated. The charged particles reaching the outer peripheral portions of the magnetic poles 21 and 23 are separated from the orbit by the electrostatic deflector 90, pass through the introduction gaps of the magnetic channels 9A and 9B, are repeatedly deflected and focused, and are extracted to the outside through the beam extraction channel and are emitted.

Next, the configurations of the magnetic tunnels 9A and 9B and the diamagnetic tunnels 9C and 9D will be described. Since the 4 magnetic channels 9 have the same configuration, the magnetic channel 9B will be described below, and redundant description thereof will be omitted.

Fig. 3 is a perspective view showing a main part of the magnetic tunnel 9B. As shown in fig. 3, the magnetic tunnel 9B includes a curved inner-periphery-side magnetic member 40 and an outer-periphery-side magnetic member 50 located on the outer periphery side of the inner-periphery-side magnetic member 40 and curved similarly to the inner-periphery-side magnetic member 40. The outer peripheral magnetic member 50 is composed of two magnetic members 50a and 50b arranged in the vertical direction. The curved gap G formed between the inner magnetic member 40 and the outer magnetic member 50 serves as a passage for the charged particle beam. The inner-peripheral magnetic member 40 and the outer-peripheral magnetic member 50 form a magnetic tunnel of a focusing type (Radial focusing type) for radially focusing the charged particle beam passing through the gap G. The inner magnetic member 40 and the outer magnetic member 50 are made of a magnetic material such as pure iron or cobalt iron. In reality, the magnetic tunnel 9B includes a support structure for supporting the inner and outer magnetic members 40 and 50, a cooling medium flow path for cooling them, and the like, but illustration and description thereof are omitted.

The magnetic channels 9A, 9B and the diamagnetic channels 9C, 9D need to receive the main magnetic field formed by the magnetic poles 21, 23 to accurately produce a prescribed magnetic gradient. Therefore, it is required to accurately (e.g., within 0.1mm of error) position the magnetic channels 9A, 9B and the diamagnetic channels 9C, 9D with respect to the magnetic poles 21, 23. Therefore, in the cyclotron 1, at least 1 of the magnetic channels 9A, 9B and the diamagnetic channels 9C, 9D adopts a setting structure for accurately positioning the positions relative to the magnetic poles 21, 23. In the present embodiment, the above arrangement structure is adopted for both the magnetic tunnel 9B and the diamagnetic tunnel 9D.

The above-described arrangement of the magnetic tunnel 9B and the diamagnetic tunnel 9D will be described below. Since both the installation structures are the same, the following description will be given of the installation structure of the magnetic tunnel 9B, and redundant description will be omitted. Fig. 4 is a plan view showing an outer peripheral end of magnetic pole 21 on which magnetic tunnel 9B is arranged. In fig. 4, a detailed description of the magnetic tunnel 9B is omitted, and only the outline is mainly illustrated.

In the cyclotron 1, a magnetic tunnel portion 61 including the magnetic tunnel 9B is mounted on and supported by the magnetic pole 21. Specifically, as shown in fig. 4, the magnetic tunnel portion 61 is attached to the outer peripheral side surface 22 of the magnetic pole 21 having a cylindrical surface. The magnetic tunnel part 61 includes a SUS plate 63 attached to the outer peripheral side surface 22 and a magnetic tunnel 9B provided on the upper surface of the SUS plate 63.

In order to position and adjust the position of magnetic tunnel 9B with respect to magnetic pole 21, magnetic tunnel portion 61 includes the following mechanism. In the following description, an R θ polar coordinate system is assumed with the central position of the magnetic pole 21 as the origin in a plan view, and the radial direction is assumed as the "R direction" and the circumferential direction is assumed as the "θ direction".

A θ positioning member 65 (circumferential positioning portion) is attached to the upper surface of the SUS plate 63 so as to protrude toward the magnetic pole 21 side. The θ position of the SUS plate 63 relative to the magnetic pole 21 is accurately positioned by bringing the θ positioning member 65 into close contact with a predetermined position (for example, a fan-shaped side surface of the magnetic pole 21) on the outer peripheral portion of the magnetic pole 21. Further, a pin 67 is provided which penetrates the magnetic tunnel 9B and the SUS plate 63 together in the vertical direction (direction orthogonal to the paper surface of fig. 4). The pin 67 is accurately fitted with the magnetic tunnel 9B and the SUS plate 63 in the θ direction. Thereby, the relative θ position of the magnetic tunnel 9B with respect to the SUS plate 63 is accurately positioned. Thereby, the relative θ position of the magnetic tunnel 9B with respect to the magnetic pole 21 is accurately positioned.

The through-hole of the pin 67 formed on the SUS plate 63 is a long hole 63a extending in the R direction, and the relative R position of the magnetic tunnel 9B with respect to the SUS plate 63 is not limited by the pin 67. A guide 69 is fixed to the upper surface of the SUS plate 63, a screw 71 extending in the substantially R direction is screwed to the guide 69, and the tip of the screw 71 abuts against the side surface of the pin 67. When the screw 71 is rotated, the pin 67 follows the tip of the screw 71, is guided by the long hole 63a, and moves in the R direction together with the entire magnetic tunnel 9B. With this structure, the magnetic tunnel 9B can be finely moved only in the R direction.

In order to position magnetic tunnel 9B in R direction relative to magnetic pole 21, R positioning portions 73 and 75 (radial positioning portions) are provided at 2 locations on magnetic tunnel 9B. The R positioning portions 73, 75 are aligned in the θ direction, and the pin 67 is present between the R positioning portions 73, 75. The R positioner 73 includes a bar 77 protruding in the R direction from the magnetic tunnel 9B toward the magnetic pole 21 side. The tip of the bar 77 abuts against the outer peripheral side surface 22 of the magnetic pole 21. The amount of protrusion of the bar material 77 can be adjusted by rotating the nut 79 engaged with the bar material 77. The amount of protrusion of the rod 77 can be fixed by tightening the nut 81. The R positioning portion 75 also has the same configuration as the R positioning portion 73 described above. As described above, by adjusting the amount of projection of the bar material 77 in the R positioning portions 73, 75 so that the tip of each bar material 77 abuts against the outer peripheral side surface 22 of the magnetic pole 21, the relative R position of the magnetic tunnel 9B with respect to the magnetic pole 21 can be accurately positioned.

Further, since the projecting amount of each bar 77 in the R positioning portions 73 and 75 can be individually adjusted, for example, the position in the rotational direction in the R θ plane of the magnetic tunnel 9B centering on the position of the pin 67 can be accurately positioned and adjusted.

Next, the operation and effect of the cyclotron 1 will be described. If a method of holding the magnetic tunnel via a position adjustment mechanism provided outside the acceleration space is adopted as described in patent document 1, for example, it is considered that sufficient relative positional accuracy of the magnetic tunnel with respect to the magnetic pole cannot be obtained because positional errors of respective portions of the position adjustment mechanism accumulate. In contrast, in the cyclotron 1, the magnetic tunnel part 61 is attached to the magnetic pole 21, and therefore the relative position (R position, θ position) of the magnetic tunnel 9B with respect to the magnetic pole 21 can be directly positioned, and as a result, the positioning can be accurately performed.

Then, a case is considered in which the magnetic tunnel 9B is held by the frame body of the vacuum chamber 3. As described above, the vacuum chamber 3 is evacuated to make the acceleration space of the charged particles in a high vacuum state. Thus, the frame of the vacuum chamber 3 is distorted by the vacuum suction, and the positional accuracy of the magnetic path 9B held by the frame is also affected. In contrast, in the cyclotron 1, the magnetic tunnel portion 61 is attached to the magnetic pole 21. Further, the magnetic pole 21 has extremely high rigidity as compared with the frame of the vacuum chamber 3, and distortion and the like due to vacuum suction are extremely small. Therefore, high positional accuracy of the magnetic tunnel 9B can be maintained also when the cyclotron 1 is used.

The present invention can be implemented in various forms including the above-described embodiments, and various modifications and improvements can be made according to the knowledge of those skilled in the art. Further, a modification can be configured by using the technical matters described in the above embodiment. The structures of the embodiments may be used in appropriate combinations. For example, the magnetic tunnel part 61 may be mounted on the magnetic pole 23 instead of the magnetic pole 21.