JP4629121B2 - Foil stripper and particle accelerator - Google Patents

Description

  The present invention relates to a foil stripper for taking out accelerated particles and a particle accelerator including the same.

In a particle accelerator such as a cyclotron, usually accelerated particles extracted in a state where a uniform magnetic field is applied are subjected to multiple acceleration by an electric field generated in a high-frequency acceleration cavity (RF cavity). Then, the orbit radius is increased with acceleration, and finally the orbit is bent by the foil of the foil stripper and guided to a target for generating a radioisotope (see, for example, Patent Document 1).
JP 2005-38628 A

  In such a particle accelerator, it is preferable that one foil stripper can handle more targets. Therefore, it is conceivable that a plurality of targets are provided in the circumferential direction on the outer periphery of the magnet, and one foil stripper is moved along the trajectory of the acceleration particles to induce the acceleration particles to each target.

  However, when moving the foil stripper to induce accelerated particles to multiple targets, the beam space is hindered if a mechanism for moving the foil stripper is placed in the beam acceleration space that accelerates the accelerated particles. Therefore, the amount of beam generated by the cyclotron may be reduced.

  An object of the present invention is to provide a foil stripper and a particle accelerator capable of solving the above-described problems and capable of guiding accelerated particles to a plurality of targets by one foil stripper without obstructing beam space. To do.

  The foil stripper according to the present invention is a foil stripper for taking out accelerated particles, and the guide formed in an arc shape and the foil for bending the trajectory of the accelerated particle are located inside the arc-shaped track of the guide. A movable body that is movable along the guide; and a driving unit that is connected to the movable body and applies a driving force for moving the movable body.

  With this configuration, all the components of the foil stripper can be installed outside the foil arranged on the trajectory of the accelerating particles, so that multiple target can be formed by one foil stripper without obstructing the beam space. Accelerating particles can be induced.

  In the foil stripper according to the present invention, the moving body has an outer peripheral portion extending along the track by the guide, and a sector gear is provided on the outer peripheral portion, and the driving means is driven to the moving body via the sector gear. It is preferable to apply force.

  With this configuration, since a driving force is applied to the moving body via the sector gear, the connecting portion between the moving body and the driving means is less likely to be worn or deteriorated compared to driving with a wire or the like, and stable for a long time. Control can be realized.

  In the foil stripper according to the present invention, a roller is rotatably provided on the movable body, and the movable body is movable along the guide by being engaged with the guide from the side surface of the guide. Is preferred.

  With this configuration, the engagement portion between the guide and the moving body only needs to be engaged with the guide in a state where at least a pair of rollers can rotate. Since it is not necessary to strictly consider resistance, the design and maintenance of the engaging portion is simplified.

  Further, the particle accelerator according to the present invention includes a pair of magnetic poles that are each formed in a disk shape and arranged to face each other, a guide that is disposed on the outer peripheral side of the pair of magnetic poles and is formed in an arc shape, and an orbit of an accelerated particle A movable body that is provided so that a foil for bending is disposed between the pair of magnetic poles and is movable along the guide, and a driving means that is connected to the movable body and provides a driving force for moving the movable body And.

  With this configuration, since all the components for moving the foil are installed on the outer periphery of the pair of magnetic poles where the orbits of the acceleration particles exist, a plurality of foil strippers can be used by one foil stripper without hindering the beam space. Accelerated particles can be guided to the target.

  According to the foil stripper and the particle accelerator according to the present invention, the acceleration particles can be guided to a plurality of targets by one foil stripper without hindering the beam space.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a front view showing a configuration of a cyclotron 10 as a particle accelerator according to the present embodiment. As shown in FIG. 1, the cyclotron 10 includes a pair of magnetic poles 16, a pair of coils (not shown), a vacuum box 20, a pair of acceleration electrodes 22, a foil stripper 46, and targets 48 a to 48 c. Yes.

  Each of the pair of magnetic poles 16 has a disk-like outer shape as shown in FIGS. On the opposing surfaces of these magnetic poles 16, valley regions 16a and mountain regions 16b are alternately and continuously provided. More specifically, the opposing surfaces of these magnetic poles 16 are divided into eight sector sectors in which four valley regions 16a and four mountain regions 16b appear alternately. With such a configuration, the convergence effect of the orbits of the accelerated particles is enhanced by using sector focusing.

  As shown in FIG. 1, the vacuum box 20 has a box body 21 and a box lid (not shown). An opening 21b having substantially the same diameter as the outer shape of the magnetic pole 16 is provided in the bottom wall portion 21a of the box body 21, and a surface including a valley region 16a and a mountain region 16b of one magnetic pole 16 from the opening 21b. Is protruded into the vacuum box 20. Further, the box body 21 is provided with an exhaust port (not shown) for vacuum exhaust, and a vacuum pump (not shown) is connected to the exhaust port. The box lid closes the upper opening of the box body 21 so that the vacuum box 20 can be evacuated by a vacuum pump. Similarly to the box body 21, the box lid is provided with an opening having substantially the same diameter as the outer shape of the magnetic pole 16 so that the surface including the valley region 16 a and the mountain region 16 b of the other magnetic pole 16 protrudes from the vacuum box 20. It has been.

  A pair of coils (not shown) are provided around the side surfaces of the pair of magnetic poles 16 to constitute an electromagnet.

  As shown in FIG. 1, each of the pair of acceleration electrodes 22 has a triangular shape in front view. Each acceleration electrode 22 is made of an electrical conductor such as copper, and is formed by connecting two upper and lower triangular plates at the bottom. A tube 32 for passing a cooling refrigerant is provided on the plate surface of the acceleration electrode 22.

  The pair of acceleration electrodes 22 is located in the valley region 16 a of the pair of magnetic poles 16. And as shown in FIG. 1, the front-end | tip parts of the acceleration electrode 22 are mechanically and electrically connected by the connection member 34 which has an external shape like a butterfly wing.

  A foil stripper 46 for taking out accelerated particles is provided on one side of the acceleration electrode 22. The foil stripper 46 is provided with four foils 47 (see FIG. 3), and one of the foils is arranged on the trajectory of the acceleration particles. The foil is moved by the foil stripper 46 so as to be positioned at the first predetermined position 101a, the second predetermined position 101b, the third predetermined position 101c, and the fourth predetermined position 101d on the orbit of the accelerated particles. The

  On the orbit of the accelerated particles after passing through the foil 47 when the foil 47 of the foil stripper 46 is positioned at the first predetermined position 101a, the second predetermined position 101b, and the third predetermined position 101c, A first target 48a, a second target 48b, and a third target 48c for generation are provided. Each target is provided with collimators 49a, 49b, and 49c for limiting the beam width of the accelerated particles introduced into the target at the inlet for introducing the accelerated particles.

  Next, the details of the foil stripper 46 will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing a detailed configuration of the foil stripper 46. 4 is a cross-sectional view taken along the line IV-IV in FIG.

  As shown in FIG. 3, the foil stripper 46 includes a guide 51, a moving body 52, a drive mechanism 56, a foil changer 63, and a control device (not shown).

  The guide 51 is a plate member that is disposed on the outer peripheral side of the pair of magnetic poles 16 and has side surfaces 51a and 51b on the outer side and the inner side along the arc shape. The arc formed by the guide 51 is designed to have the same center point as the arc passing through the three points 101a, 101b, and 101c on the beam trajectory of the accelerated particles near the guide 51. The center of curvature of the arc formed by the guide 51 is a point P different from the center O of the magnetic pole 16, and the radius of curvature is smaller than the radius of the magnetic pole 16.

  A movable body 52 is engaged with the guide 51 so as to be movable along the guide 51. The moving body 52 includes a foil cassette unit 50 having four foils 47. The foil cassette unit 50 is provided in the moving body 52 so that one of the four foils 47 is positioned on the inner side of the arc formed by the guide 51 and arranged on the orbit of the accelerated particles. The single foil is used to pass the acceleration particles to bend the trajectory in the centrifugal direction of the magnetic pole 16, and the remaining three foils are provided in the foil cassette unit 50 as spare foils for replacement.

  The moving body 52 is provided with two pairs of flanged rollers 53 a, 53 b, 54 a, 54 b on the back surface of the surface including the foil cassette unit 50 so as to be rotatable about a rotation axis orthogonal to the back surface of the moving body 52. It has been. Among these, the rollers 53a and 54a are arranged to engage with the outer side surface 51a of the guide, and the rollers 53b and 54b are arranged to engage with the inner side surface 51b of the guide. That is, as shown in FIG. 4, the moving body 52 is engaged with the guide from the outer side surface 51a and the inner side surface 51b of the guide 51 by a pair of flanged rollers 53a and 53b. The movable body 52 is engaged with the guide from the outer side surface 51a and the inner side surface 51b of the guide 51 by the pair of flanged rollers 54a and 54b. As a result, the moving body 52 can move along the guide 51.

  The moving body 52 has an outer peripheral surface along the arc-shaped track of the guide 51, and a sector gear 55 is provided on the outer peripheral surface.

  A driving mechanism 56 that applies a driving force for moving the moving body 52 is connected to the moving body 52 via the sector gear 55 of the moving body 52. As shown in FIG. 4, the drive mechanism 56 includes a stepping motor 57 and a gear mechanism that decelerates rotation and converts it into rotation in an orthogonal direction. The gear mechanism is engaged with a first shaft 58 which is a rotation shaft of the stepping motor 57, a first bevel gear 59 attached to the first shaft 58, and a first bevel gear 59. An orthogonal second bevel gear 60, a second shaft 61 that is the rotation center of the second bevel gear 60, and a pinion gear 62 attached to the second shaft 61 are provided. As shown in FIG. 3, the pinion gear 62 is meshed with the sector gear 55 of the moving body 52.

  The foil stripper 46 is provided with a foil changer 63. The foil stripper 46 can be replaced with a new foil by using the foil changer 63 when the foil 47 arranged on the orbit of the accelerated particles is worn out due to long-term use or the like and deteriorates or breaks. The foil changer 63 contacts the foil cassette unit 50 when the foil 47 is moved from the third predetermined position 101c to the fourth predetermined position 101d. Configured to replace.

  The foil stripper 46 has a control device (not shown), and feedback control of the position of the foil 47 is performed by this control device. Specifically, the current value is detected by a pair of collimators 49a to 49c provided at the inlets of the targets 48a to 48c. Since these current values take a larger value as the area hit by the beam increases, the relative deviation between the center of the beam diameter and the center of the target entrance can be detected by comparing these current values. That is, when one of the current values is large, it indicates that the beam is biased in the direction of the detection point of the current value. It then shows that the beam has been correctly introduced to the desired target.

  A control device (not shown) of the foil stripper 46 controls a control command to the stepping motor 57 according to a difference between current values measured by a pair of collimators provided at an entrance of a target to which a beam is to be introduced among the targets 48a to 48c. Feedback control. As a result, the position of the foil 47 on the beam trajectory is adjusted so that the center of the beam diameter coincides with the center of the target entrance.

  Next, the operation of the cyclotron 10 and the foil stripper 46 configured as described above will be described.

  Accelerated particles such as protons or deuterons are extracted from the beam extraction portion O provided at the center of the magnetic pole 16 to a space where a uniform magnetic field is applied by the magnetic pole 16 and multiplexed by the electric field generated by the RF cavity. Accelerated. Accelerating particles have an orbital radius that increases with acceleration.

  In the foil stripper 46, the stepping motor 57 of the drive mechanism 56 is driven, and the pinion gear 62 rotates through the gear mechanism in the drive mechanism 56. The sector gear 55 of the moving body 52 meshed with the pinion gear 62 is interlocked, and the moving body 52 moves along the guide 51. The foil 47 of the foil cassette unit 50 mounted on the moving body 52 is positioned at the first predetermined position 101a, the second predetermined position 101b, or the third predetermined position 101c.

  Accelerated particles that have been subjected to multiple acceleration and have a large orbit radius are finally introduced into the target in a trajectory in which the center of curvature of the orbit changes from the inside to the outside of the magnetic pole 16 by the foil 47 of the foil stripper 46. In the present embodiment, when the foil 47 is at the first predetermined position 101a, the accelerated particles are introduced into the first target 48a. When the foil 47 is at the second predetermined position 101b, the accelerated particles are introduced into the second target 48b. When the foil 47 is at the third predetermined position 101c, the accelerated particles are introduced into the third target 48c.

  As described above, the cyclotron 10 and the foil stripper 46 according to the present embodiment can move the foil stripper 46 along the trajectory of the accelerating particles, so that a plurality of targets 48a to 48c can be obtained by one foil stripper 46. Accelerating particles can be induced. Further, since the guide 51, the moving body 52, and the driving mechanism 56, which are constituent elements of the foil stripper 46, are installed on the outer peripheral side of the magnetic pole 16 where the trajectory of the acceleration particles exists, the beam space is not hindered.

  Further, in the foil stripper 46, since the driving force is given to the moving body 52 through the pinion gear 62 of the driving mechanism 56 and the sector gear 55 of the moving body 52, the movement is performed as compared with the case of driving with a wire or the like. A connecting portion between the body 52 and the drive mechanism 56 is less likely to be worn or deteriorated, and long-term stable control can be realized.

  In the foil stripper 46, the two pairs of flanged rollers 53a, 53b, 54a, 54b of the moving body 52 are engaged with the guide 51 from the both side surfaces 51a, 51b of the guide 51. Thus, it is not necessary to strictly consider machining accuracy and frictional resistance, and the design and maintenance of the engaging portion between the guide 51 and the moving body 52 becomes simple.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the drive mechanism 56 of the foil stripper 46 may be a friction mechanism other than a gear mechanism, or may be a cylinder mechanism using a crank.

  Further, the number of targets for introducing accelerated particles from one foil stripper 46 may be other than three.

  Further, in the above embodiment, the acceleration particles are taken out from one place using one foil stripper 46. However, a plurality of foil strippers are arranged at equal intervals on the orbit of the acceleration particles, and accelerated from a plurality of places at the same time. You may comprise so that particle | grains may be taken out.

It is a front view which shows the structure of a cyclotron as a particle accelerator which concerns on this embodiment. It is a perspective view which shows the structure of a pair of magnetic pole. It is a figure which shows the detailed structure of a foil stripper. It is IV-IV sectional drawing of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Cyclotron, 16 ... Magnetic pole, 22 ... Acceleration electrode, 46 ... Foil stripper, 47 ... Foil, 48a, 48b, 48c ... Target, 50 ... Foil cassette unit, 51 ... Guide, 51a ... Outer side, 51b ... Inner side, 52... Moving body, 53 a, 53 b, 54 a, 54 b ... collar roller, 55... Sector gear, 56.

Claims (4)

A foil stripper for removing accelerated particles,
An arc-shaped guide;
A foil for bending the trajectory of the acceleration particles is provided so as to be located inside the arcuate trajectory of the guide, and a movable body movable along the guide;
Driving means connected to the moving body and providing a driving force for moving the moving body;
Foil stripper with The movable body includes an outer peripheral portion extending along a track by the guide, and a sector gear is provided on the outer peripheral portion,
The driving means gives a driving force to the moving body via the sector gear.
The foil stripper according to claim 1. A roller is rotatably provided on the moving body,
The roller is engaged with the guide from a side surface of the guide, so that the movable body can move along the guide.
The foil stripper according to claim 1 or 2. A pair of magnetic poles, each of which is formed in a disk shape and arranged oppositely,
A guide disposed on the outer peripheral side of the pair of magnetic poles and formed in an arc shape;
A foil for bending the trajectory of the accelerating particles is provided between the pair of magnetic poles, and a movable body movable along the guide;
Driving means connected to the moving body and providing a driving force for moving the moving body;
A particle accelerator comprising:

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