JP6042247B2 - cyclotron - Google Patents

Description

  The present invention relates to a cyclotron.

  As a cyclotron that accelerates charged particles and outputs a charged particle beam, for example, the one shown in Patent Document 1 is known. This cyclotron includes a pair of poles functioning as magnetic poles, and a resonator having a pair of de-electrodes disposed between the poles. The resonator generates an electric field at a predetermined resonance frequency and accelerates charged particles passing through an acceleration space formed between the de-electrodes.

JP 2002-43097 A

  Here, in the above-described cyclotron, the balance between the upper and lower electric fields centered on the median plane (the plane on which the circular orbit where the charged particle beam accelerates and moves) is caused by the influence of the dimensional error of the electrode. It may collapse. In this way, when the balance between the upper and lower electric fields is lost, the acceleration of charged particles may be affected by, for example, contact finger burnout or pole heat generation.

  Therefore, an object of the present invention is to provide a cyclotron capable of suppressing the balance of the electric field of the resonator from being lost and improving the acceleration performance of charged particles.

  The cyclotron according to the present invention has a plurality of valleys and a plurality of hills alternately formed in the circumferential direction, is provided between a pair of poles facing each other and a valley of the pair of poles, and is supplied with high-frequency power. A resonator, a detector disposed in the valley and detecting a high frequency from the resonator, and a resonance frequency adjusting unit capable of adjusting a resonance frequency of the resonator.

  The cyclotron according to the present invention includes a detection unit that is disposed in a valley and detects a high frequency from the resonator, and a resonance frequency adjustment unit that can adjust the resonance frequency of the resonator. Therefore, when the high frequency leaks from the resonator due to the balance of the electric field between the pair of poles, the leakage high frequency can be detected by the detection unit. Further, since the resonance frequency adjustment unit can adjust the resonance frequency of the resonator, the electric field imbalance can be eliminated by adjusting the resonance frequency based on the detection result by the detection unit. By the above, it can suppress that the electric field balance of a resonator collapses, and can improve the acceleration performance of a charged particle.

  In the cyclotron according to the present invention, the detection unit may be attached to the side wall of the valley. The high frequency leaked from the resonator passes through the hill adjacent to the resonator and travels from the side wall of the valley to the bottom surface. Therefore, by arranging the detection unit on the side wall of the valley, it is possible to detect a high frequency at a position close to the resonator.

  In the cyclotron according to the present invention, the detection unit may be arranged on the center side in the radial direction. Since the leakage high frequency is more likely to occur at the center side in the radial direction, the detection unit can easily detect the leakage high frequency.

  In the cyclotron according to the present invention, the resonance frequency adjustment unit may include a block tuner, and the block tuner may adjust the resonance frequency by changing the volume between the valleys of the pair of poles. Thereby, the resonance frequency can be easily adjusted.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the balance of the electric field of a resonator breaks, and can improve the acceleration performance of a charged particle.

It is a top view inside the cyclotron which concerns on embodiment of this invention. It is a schematic diagram of a pair of pole with which the cyclotron of FIG. 1 is provided. It is sectional drawing along the III-III line | wire shown in FIG. It is sectional drawing along the IV-IV line shown in FIG.

  Hereinafter, embodiments of a cyclotron according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view of the inside of a cyclotron 1 according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a pair of poles 4A and 4B provided in the cyclotron 1 of FIG. FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. 3 and 4 are cross-sectional views along a line (indicated by a broken line in FIG. 1) indicating a central position in the circumferential direction of the valley. The cyclotron 1 according to the present embodiment is a circular accelerator that supplies charged particles from an ion source (not shown) into the acceleration space G, accelerates the charged particles in the acceleration space G, and outputs a charged particle beam. In the cyclotron 1 of the present embodiment, the spiral orbit B of the charged particle beam is on the horizontal plane. Note that the cyclotron of the present invention may be arranged so that the orbit B is on the vertical plane. Examples of the charged particles include protons and heavy particles (heavy ions). The cyclotron 1 is used as an accelerator for charged particle beam therapy, for example. In the present embodiment, an AVF [Azimutally Varying Field] cyclotron, which is a cyclotron that forms a magnetic flux density that is strong and weak in the circumferential direction, will be described as an example.

  As shown in FIGS. 1 to 4, the cyclotron 1 includes a yoke 3, a pair of poles 4 </ b> A and 4 </ b> B, resonators 5 and 6, a coil 7, a detection unit 8, and a resonance frequency adjustment unit 9. Prepare.

  The yoke 3 supports the vacuum vessel 2 (see FIG. 4) and the coil 7. The vacuum container 2 is a container for maintaining the acceleration space of charged particles in a high vacuum state. In the yoke 3, a pair of poles 4A and 4B functioning as magnetic poles for forming a magnetic field necessary for particle acceleration are provided. The poles 4A and 4B have a circular shape in a plan view, and are above the median plane MP (the plane on which the orbit B where the charged particle beam accelerates and travels is located, and is indicated by a dashed line in FIGS. 3 and 4). It has a symmetrical shape on the bottom. A coil 7 is arranged around each of the poles 4A and 4B, and a magnetic field is generated between the poles 4A and 4B.

  FIG. 2 is a perspective view schematically showing only the poles 4A and 4B. As shown in the figure, the poles 4A and 4B are cylindrical. The terms “radial direction” and “circumferential direction” used below mean the radial direction and the circumferential direction of a circle which is the contour shape of the poles 4A and 4B as seen from the direction of FIG. On the upper surface of the pole 4A, a plurality of (four in the present embodiment) hills 11A that are spirally curved and a valley 12A that is a plurality of (four in the present embodiment) concave portions are circumferentially provided. Are alternately arranged. And on the lower surface of the pole 4B, there are a plurality of (four in the present embodiment) convex portions 11B that are spirally curved and a valley 12B that is a plurality (four in the present embodiment) concave portions, They are alternately arranged in the circumferential direction. The hill 11A and the hill 11B, and the valley 12A and the valley 12B are arranged with a gap so as to be symmetrical with respect to the median plane MP. Here, the hills 11A and 11B of the poles 4A and 4B are portions protruding toward the median plane MP, and the valleys 12A and 12B are portions recessed so as to be separated from the median plane MP. The protruding surfaces 11Aa and 11Ba of the hills 11A and 11B are surfaces extending in the horizontal direction, and the bottom surfaces 12Aa and 12Ba of the valleys 12A and 12B are surfaces extending in the horizontal direction. The projecting surfaces 11Aa and 11Ba of the hills 11A and 11B are gently curved so that the vertical distance from the median plane MP gradually decreases from the center toward the outer peripheral side (see FIG. 4). . Moreover, the surface which spreads to the up-down direction which connects protrusion surface 11Aa, 11Ba of hill 11A, 11B and bottom face 12Aa, 12Ba of valley 12A, 12B is called "the side wall 12Ab, 12Bb of valley 12A, 12B." . In addition, the shape of the hills 11A and 11B and the valleys 12A and 12B is not limited to the spirally curved shape as described above, and may be a sector shape.

Between the pole 4A and the pole 4B, a hill region 15h having a narrow gap sandwiched between the hills 11A and 11B and a valley region 15v having a wide gap sandwiched between the valleys 12A and 12B are formed. Yes. A spiral orbit B of the charged particle beam is formed on the symmetry plane (median plane MP) between the pole 4A and the pole 4B. It is assumed that valley regions 15v ₁ , 15v ₂ , 15v ₃ , 15v ₄ are formed in order in the circumferential direction, and hill regions 15h ₁ , 15h ₂ , 15h ₃ , 15h ₄ are formed. The valley region 15v ₁ is adjacent to the hill regions 15h ₁ and 15h ₄ in the circumferential direction. The valley region 15v ₂ is adjacent to the hill regions 15h ₂ and 15h ₁ in the circumferential direction. The valley region 15v ₃ is adjacent to the hill regions 15h ₃ and 15h ₂ in the circumferential direction. The valley region 15v ₄ is adjacent to the hill regions 15h ₄ and 15h ₃ in the circumferential direction.

The resonators 5 and 6 generate a high-frequency electric field for accelerating charged particles. The resonators 5 and 6 are disposed between the valleys 12A and 12B of the pair of poles 4A and 4B (valley regions 15v ₁ and 15v ₃ ), and are supplied with high-frequency power from a high-frequency power source (not shown). The resonators 5 and 6 are set so as to generate an electric field having a predetermined frequency (resonance frequency). One resonator 5 is arranged in _one valley region 15v1 among a plurality (four in this embodiment) of valley regions 15v, and the other resonator 6 is a valley in which one resonator 5 is arranged. is positioned on the opposite side of the valley regions 15v ₃ with respect to the center line for the region 15v ₁ (see FIG. 1). As shown in FIG. 3, the resonator 5 includes a lower resonator 5A and an upper resonator 5B, and the resonator 6 includes a lower resonator 6A and an upper resonator 6B. The lower resonators 5A and 6A are arranged in the valley 12A of the lower pole 4A. Upper resonators 5B and 6B are arranged in valley 12B of upper pole 4B.

  The lower resonators 5A and 6A include a de-electrode (acceleration electrode) 21A, inner conductors (stems) 22A and 23A, and an outer conductor 24A. The upper resonators 5B and 6B include de-electrodes (acceleration electrodes) 21B, inner conductors (stems) 22B and 23B, and an outer conductor 24B.

The de-electrodes 21A and 21B are electrodes that generate an electric field for accelerating charged particles inside the vacuum vessel 2 (see FIG. 4). The de-electrodes 21A and 21B are both disposed in the valley regions 15v ₁ and 15v _{3 and} are disposed so as to face each other in the vertical direction. The de-electrodes 21A and 21B are formed in a shape along the shape of the valley regions 15v ₁ and 15v ₃ in plan view. The de-electrodes 21A and 21B are separated from the bottom surfaces 12Aa and 12Ba of the valleys 12A and 12B, and the projecting surfaces 11Aa and 11Ba of the hills 11A and 11B are formed so as to form an acceleration space G formed near the median plane MP. Arranged at substantially the same position. At the center of the pole 4A, there is an inflector (not shown) that deflects charged particles sent from an ion source (not shown) provided outside or inside the cyclotron 1 and sends it on the median plane MP. Be placed. In addition, when using an internal ion source, an inflector is unnecessary. The outer conductors 24A and 24B are provided so as to surround the de-electrodes 21A and 21B. The outer conductors 24A and 24B have wall portions 24Aa and 24Ba extending along at least the bottom surfaces 12Aa and 12Ba of the valleys 12A and 12B and facing the de-electrodes 21A and 21B in the vertical direction. The inner conductors 22A and 22B extend in the vertical direction and connect the de-electrodes 21A and 21B to the wall portions 24Aa and 24Ba of the outer conductors 24A and 24B. The inner conductors 23A and 23B extend in the vertical direction and connect the de-electrodes 21A and 21B to the wall portions 24Aa and 24Ba of the outer conductors 24A and 24B. Inner conductors 22A, 22B are provided in the region of the inner peripheral side of the valley regions _15v 1, _{15v 3,} the inner conductor 23A, 23B is provided on the outer peripheral side of the region of the valley regions _15v 1, _{15v 3.}

  In the cyclotron 1, a magnetic field is generated between the pole 4A and the pole 4B, and high frequency power is supplied to the resonators 5 and 6, whereby the charged particle beam is accelerated and spiraled on the median plane MP. The orbit B of the vehicle advances. The charged particle beam that has reached the outer peripheral side in the radial direction passes through a magnetic channel and a deflector (not shown), and is extracted to the outside through a beam extraction duct.

As shown in FIGS. 1 and 4, the detection unit 8 is a sensor that is disposed in the valley 12 </ b> A and detects a high frequency from the resonators 5 and 6. When a high frequency leaks from the acceleration space G to the hill region 15h side due to the electric field balance being lost between the lower resonators 5A and 6A and the upper resonators 5B and 6B, the detection unit 8 Can be detected. As the detection unit 8, an electrode for picking up a high frequency may be provided. The detector 8 is disposed in a valley region 15v adjacent to the resonators 5 and 6 with the hill region 15h interposed therebetween. In the present embodiment, they are arranged in the valley regions 15v ₂ and 15v ₄ .

The detection unit 8 may be disposed at any position on the bottom surfaces 12Aa and 12Ba and the side walls 12Ab and 12Bb as long as it is within the valley regions 15v ₂ and 15v ₄ , but the leakage high frequency is detected at a position close to the resonators 5 and 6. That is, it is preferable to attach to the side walls 12Ab and 12Bb of the valleys 12A and 12B. Detector 8 for detecting the leakage high frequency resonator 5, the Hill region 15h ₁ adjacent to the resonator 5, the side walls 12Ab, well attached to 12Bb (FIGS. 1 and between the valley area 15v ₂ in the example shown in 4, it is attached to the side wall 12Ab), and Hill area 15h ₄ adjacent to the cavity 5, the side wall between the valley regions 15v ₄ 12Ab, may be attached to 12Bb. Note that the detection unit 8 attached at these positions may detect the leakage high frequency of the resonator 6. Detector 8 for detecting the leakage high frequency resonator 6, the Hill area 15h ₃ adjacent to the resonator 6, the side walls 12Ab, well attached to 12Bb (FIGS. 1 and between the valley area 15v ₄ in the example shown in 4, it is attached to the side wall 12Ab), and Hill area 15h ₂ adjacent to the resonator 6, the side wall between the valley regions 15v ₂ 12Ab, may be attached to 12Bb. Note that the detection unit 8 attached at these positions may detect the leakage high frequency of the resonator 5.

The detection unit 8 of the valley regions _15v 2, 15v _4, in the radial direction, are arranged on the center side. Specifically, as shown in FIG. 4, when the reference line CL is set at the center position in the radial direction of the valley region 15v ₂ , the detection unit is located in the region E1 on the center side (inner peripheral side) with respect to the reference line CL. 8 is arranged. However, the detection unit 8 may be arranged on the reference line CL or in a region E2 on the outer peripheral side of the reference line CL. As shown in FIG. 4, when the detection unit 8 is arranged on the side wall 12Ab, the detection unit 8 is arranged in a region on the median plane MP side of the side wall 12Ab. However, you may arrange | position in the area | region by the side of bottom face 12Aa of side wall 12Ab.

  In FIG. 4, the detection unit 8 is provided on the pole 4A side, but may be provided on the pole 4B or may be provided on both the valleys 12A and 12B of the poles 4A and 4B. Moreover, you may provide the detection part 8 in multiple places with respect to one valley 12A, 12B.

  The resonance frequency adjusting unit 9 is a mechanism capable of adjusting the resonance frequency of the resonators 5 and 6. The resonance frequency adjustment unit 9 can adjust the resonance frequency of the resonators 5 and 6 based on the detection result of the detection unit 8. The resonance frequency adjustment unit 9 performs adjustment so that the signal detected by the detection unit 8 is minimized. The adjustment method and the adjustment timing are not particularly limited. For example, when the cyclotron 1 is initially set, the operator manually adjusts the resonance frequency adjustment unit 9 while referring to the detection result of the detection unit 8 to resonate. The frequency may be adjusted. Or, for example, when the resonance frequency of the cyclotron 1 is changed and used, the control unit for adjusting the resonance frequency is provided in the cyclotron 1 and the resonance frequency adjustment unit 9 is controlled so that the signal from the detection unit 8 becomes small. Thus, the resonance frequency may be adjusted.

As shown in FIGS. 1 and 3, the resonance frequency adjusting unit 9 has a block tuner 33. The block tuner 33 adjusts the resonance frequency of the resonators 5 and 6 by changing the volume in the valley regions 15v ₁ and 15v ₃ of the pair of poles 4A and 4B. The block tuner 33 adjusts the resonance frequency of the resonators 5 and 6 by changing the amount of protrusion to the space surrounded by the de-electrodes 21A and 21B and the outer conductors 24A and 24B (that is, changing the volume of the space). can do. The resonance frequency can be increased by increasing the protruding amount of the block tuner 33 and reducing the volume of the space.

  The arrangement location of the resonance frequency adjusting unit 9 is not particularly limited, but may be arranged on the bottom surface 12Aa, 12Ba side of the valleys 12A, 12B. Moreover, although the arrangement | positioning location in planar view is not specifically limited, It is preferable to arrange | position in the place where magnetic flux is as much as possible. The resonance frequency adjusting unit 9 may be disposed at a position separated from the region between the inner conductor 22A and the inner conductor 23A. Specifically, in the example shown in FIG. 1, the resonance frequency adjusting unit 9 is disposed in the vicinity of the inner conductor 23A on the outer peripheral side and on the outer peripheral side from the inner conductor 23A. The resonance frequency adjusting unit 9 may be disposed in the vicinity of the inner conductor 22A on the inner circumference side and on the inner circumference side from the inner conductor 22A. Further, it is a region on the outer peripheral side from the inner conductor 22A and on the inner peripheral side from the inner conductor 23A, and from the line (indicated by a broken line in FIG. 1) indicating the center position in the circumferential direction of the valley 12A in the circumferential direction. The resonance frequency adjusting unit 9 may be disposed at a spaced position. Note that a C (capacitor) tuner may be used as the resonance frequency adjusting unit 9. The C tuner may be provided in the vicinity of the outer peripheral end of the resonators 5 and 6.

  Next, the operation and effect of the cyclotron 1 according to the present embodiment will be described.

  Here, in a conventional cyclotron that does not include the detection unit 8 and the resonance frequency adjustment unit 9, the balance of the upper and lower electric fields around the median plane MP is caused by the influence of the dimensional error of the deelectrodes 21A and 21B. It may collapse. Thus, when the balance between the upper and lower electric fields is lost, the acceleration of charged particles may be affected. For example, if the balance between the upper and lower electric fields is good, no current flows through the contact finger 31 (see FIG. 1). However, when the electric field is unbalanced, a slight current flows through the contact finger 31. As a result, heat is generated in the contact fingers 31 and burns out. When the contact finger 31 is burned out, the acceleration performance of the charged particles is deteriorated by changing the resonance frequency of the resonators 5 and 6. Moreover, the heat generation of the poles 4A and 4B occurs, the hills 11A and 11B of the poles 4A and 4B are distorted by the heat, and the acceleration performance of the charged particles is deteriorated by changing the gradient of the magnetic field.

  On the other hand, the cyclotron 1 according to the present embodiment is disposed in valleys 12A and 12B, and a detection unit 8 that detects a high frequency from the resonators 5 and 6, and a resonance frequency adjustment that can adjust the resonance frequency of the resonators 5 and 6. Part 9. Therefore, when a high frequency leaks from the resonators 5 and 6 due to the balance of the electric field between the pair of poles 4A and 4B (see, for example, the alternate long and short dash line RF shown in FIGS. 1 and 4), the detection unit 8 causes the leakage. High frequency can be detected. In addition, since the resonance frequency adjustment unit 9 can adjust the resonance frequency of the resonators 5 and 6, the electric field imbalance can be eliminated by adjusting the resonance frequency based on the detection result by the detection unit 8. Is possible. By the above, it can suppress that the electric field balance of the resonators 5 and 6 breaks down, and can improve the acceleration performance of a charged particle.

  In the cyclotron 1 according to the present embodiment, the detection unit 8 is attached to the side walls 12Ab and 12Bb of the valleys 12A and 12B. The high frequency leaking from the resonators 5 and 6 passes through the hills 11A and 11B adjacent to the resonators 5 and 6 and travels from the side walls 12Ab and 12Bb of the valleys 12A and 12B to the bottom surfaces 12Aa and 12Ba. Therefore, by arranging the detector 8 on the side walls 12Ab and 12Bb of the valleys 12A and 12B, a high frequency can be detected at a position close to the resonators 5 and 6.

  Moreover, in the cyclotron 1 according to the present embodiment, the detection unit 8 is disposed on the center side in the radial direction. Since the leakage high frequency is more likely to occur at the center in the radial direction, the detection unit 8 can easily detect the leakage high frequency.

  In the cyclotron 1 according to the present embodiment, the resonance frequency adjusting unit 9 includes a block tuner 33. The block tuner 33 resonates by changing the volume between the valleys 12A and 12B of the pair of poles 4A and 4B. Adjust the frequency. Thereby, the resonance frequency can be easily adjusted.

  The present invention is not limited to the embodiment described above. For example, in the above-described cyclotron 1, the poles 4A and 4B have four hills 11A and 11B and four valleys 12A and 12B, respectively, but may be more or less than four. Also, the type of cyclotron is not particularly limited, and a ring cyclotron may be applied.

  DESCRIPTION OF SYMBOLS 1 ... Cyclotron, 4A, 4B ... Pole, 5, 6 ... Resonator, 7 ... Coil, 8 ... Detection part, 9 ... Resonance frequency adjustment part, 11A, 11B ... Hill, 12A, 12B ... Valley.

Claims (3)

A pair of poles having a plurality of valleys and a plurality of hills alternately formed in the circumferential direction and facing each other;
A resonator provided between the valleys of the pair of poles and supplied with high-frequency power;
A detector that is disposed in the valley and detects a high-frequency current from the resonator;
A resonance frequency adjustment unit capable of adjusting the resonance frequency of the resonator,
The resonator includes an acceleration electrode that generates an electric field for accelerating charged particles by the high-frequency power supplied from a high-frequency power source, an outer conductor provided along a surface of the valley, the acceleration electrode, and the outer conductor And an inner conductor connecting the
The detection unit is a cyclotron attached to a sidewall of the valley . The cyclotron according to claim 1, wherein the detection unit is disposed on a center side in a radial direction. The resonance frequency adjustment unit has a block tuner,
Said block tuner adjusts the resonance frequency by changing the volume between the valley of the pair of poles, the cyclotron according to claim 1 or 2.

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