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WO2022130680A1 - Accélérateur et dispositif thérapeutique à faisceau de particules - Google Patents

Accélérateur et dispositif thérapeutique à faisceau de particules Download PDF

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Publication number
WO2022130680A1
WO2022130680A1 PCT/JP2021/028894 JP2021028894W WO2022130680A1 WO 2022130680 A1 WO2022130680 A1 WO 2022130680A1 JP 2021028894 W JP2021028894 W JP 2021028894W WO 2022130680 A1 WO2022130680 A1 WO 2022130680A1
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Prior art keywords
magnetic field
region
particle beam
charged particle
accelerator
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English (en)
Japanese (ja)
Inventor
裕人 中島
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Hitachi Ltd
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Hitachi Ltd
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K5/00—Irradiation devices
    • G21K5/04—Irradiation devices with beam-forming means
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H13/00—Magnetic resonance accelerators; Cyclotrons
    • H05H13/02—Synchrocyclotrons, i.e. frequency modulated cyclotrons
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
    • H05H7/04—Magnet systems, e.g. undulators, wigglers; Energisation thereof
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
    • H05H7/10—Arrangements for ejecting particles from orbits

Definitions

  • This disclosure relates to accelerators and particle beam therapy devices.
  • Particle beam therapy which is one of the cancer treatment methods, irradiates the affected area with a charged particle beam such as protons and carbon ions.
  • a charged particle beam such as protons and carbon ions.
  • the energy and spatial spread of the charged particle beam are adjusted to form a dose distribution that matches the shape of the affected area.
  • the particle beam therapy device includes an accelerator, a beam transport system, and an irradiation device.
  • An accelerator is a device that accelerates a charged particle beam to the energy used for treatment. Examples of accelerators used for particle beam therapy include synchrotrons, cyclotrons, and synchrocyclotrons.
  • the miniaturization of the accelerator will realize the miniaturization of the particle beam therapy device.
  • a superconducting magnet as an electromagnet for deflecting a charged particle beam, it is possible to reduce the size of the accelerator.
  • an accelerator to which a superconducting electromagnet is applied there is a synchrocyclotron described in Non-Patent Document 1.
  • the particle beam orbits in the static magnetic field formed by the superconducting coil, and the particle beam is accelerated by the high-frequency accelerating electric field synchronized with the orbit.
  • the frequency around the beam decreases as the beam accelerates, so the frequency of the high-frequency accelerating electric field is modulated as the frequency around the beam decreases.
  • the orbits in the horizontal plane of the beam in the synchrocyclotron are concentric circles for each energy, and the beam that has reached the designed maximum energy is taken out from the emission channel.
  • Patent Document 1 There is a circular accelerator described in Patent Document 1 as an accelerator in which the energy of the beam taken out is variable for this synchro cycloton.
  • the main magnetic field distribution is formed so as to eccentric the orbits of beams having different energies from the center of the circular accelerator to one side in the radial direction.
  • the circular accelerator of Patent Document 1 is characterized in that a beam of a specific energy is extracted by generating a disturbance in the main magnetic field in this way. With this configuration, it is possible to change the energy of the emitted beam without using a decelerating body such as a scattering body.
  • a scanning irradiation method described in Patent Document 1 as a method of forming an emitted beam into a dose distribution that matches the shape of the affected area.
  • a desired dose distribution is formed by scanning the beam using a scanning electromagnet installed upstream of the affected area.
  • an accelerator in which the beam orbits in a static magnetic field and is accelerated such as the synchrocyclotron described above, in order to take the beam out of the accelerator, it is formed by magnetic poles to accelerate or orbit the beam. It is necessary to pass the beam from the magnetic field region (called the main magnetic field) to the outside in the radial direction of the accelerator and reach the inner wall of the accelerator.
  • One object of the present disclosure is to provide a technique for reducing beam loss due to betatron vibration between the magnetic field and the inner wall of the accelerator.
  • the accelerator comprises a main electric field that forms a cylindrical region inside the yoke and forms a static magnetic field in the cylindrical region, and a beam that transports a charged particle beam from the inside of the main electric field to the outside.
  • the emission path the accelerator electric field adapter that applies a frequency-modulated accelerating electric field to accelerate the charged particle beam orbiting in the static magnetic field, and the amplitude of the betatron vibration of the charged particle beam accelerated by the accelerating electric field.
  • the main electric field has a first magnetic field for allowing a charged particle beam whose betatron vibration amplitude has been increased by the kicker to enter the beam emission path, and the static in the yoke.
  • a second magnetic field is created to suppress the divergence of the charged particle beam between the region of the magnetic field and the inner wall of the yoke.
  • the particle beam therapy device includes the above accelerator.
  • the beam loss due to betatron vibration between the main magnetic field and the inner wall of the accelerator can be reduced.
  • FIG. It is an external view of the circular accelerator 30 of Example 1.
  • FIG. It is sectional drawing which cut the circular accelerator 30 of Example 1 in the central plane. It is sectional drawing in the vertical direction of the circular accelerator 30 of Example 1.
  • FIG. It is a graph which shows the distribution of the main magnetic field on the r axis shown in FIG. It is a graph which shows the distribution of the magnetic field strength Bz in the r direction of the region including a resonance suppression magnetic field 46.
  • FIG. It is an external view of the circular accelerator 30 of Example 2.
  • FIG. It is sectional drawing which cut the eccentric orbital type accelerator of Example 2 in the central plane. It is sectional drawing in the vertical direction of the eccentric orbital type accelerator of Example 2.
  • FIG. A conceptual diagram of the design trajectory for each energy is shown.
  • FIG. 1 It is a graph which shows the relationship between the amplitude ⁇ r and the phase ⁇ of the horizontal betatron vibration for each energy. It is a graph which shows the relationship between the amplitude ⁇ z of the vertical betatron vibration for each energy, and the phase ⁇ . It is an overall block diagram of the particle beam therapy apparatus of Example 3.
  • FIG. 1 It is a graph which shows the relationship between the amplitude ⁇ r and the phase ⁇ of the horizontal betatron vibration for each energy. It is a graph which shows the relationship between the amplitude ⁇ z of the vertical betatron vibration for each energy, and the phase ⁇ .
  • FIG. 1 is an external view of the circular accelerator 30 according to the first embodiment.
  • FIG. 2 is a cross-sectional view of the circular accelerator 30 cut along the central plane.
  • FIG. 3 is a cross-sectional view of the circular accelerator 30 in the vertical direction (AA'arrow view of FIG. 2).
  • the circular accelerator 30 of this embodiment is an accelerator that accelerates charged particles applicable to a particle beam therapy device.
  • the outer shell of the circular accelerator 30 is formed by a main electromagnet 40 that can be divided in the vertical direction.
  • the region for accelerating the beam inside the main electromagnet 40 (hereinafter referred to as “acceleration region”) is kept in a vacuum.
  • An ion source 50 that generates a beam of ions for incident on the main electromagnet 40 is installed above the main electromagnet 40.
  • the beam generated by the ion source 50 reaches the ion incident portion 52 provided near the center of the main magnetic pole 38 via the low energy beam transport system 51.
  • the beam that has reached the ion incident portion 52 is incident on the acceleration region inside the main electromagnet 40 by the ion incident portion 52.
  • an ECR ion source, a laser ion source, or the like can be applied.
  • the beam is incident from the outside, for example, the beam is incident on the acceleration region through the electrostatic inflator 53.
  • the ion source 50 may be arranged inside the vacuumed acceleration region inside the main electromagnet 40. In that case, a PIG type ion source or the like is suitable.
  • the main electromagnet 40 includes a main magnetic pole 35, a yoke 37, and a main coil 38.
  • the yoke 37 forms the appearance of the main electromagnet 40 and constitutes a substantially cylindrical region inside.
  • the main coil 38 is an annular coil and is installed along the inner wall of the yoke 37.
  • the main coil 38 is a superconducting coil.
  • a cryostat 36 is installed around the main coil 38.
  • the cryostat 36 cools the main coil 38.
  • the main magnetic poles 35 are installed on the inner peripheral side of the main coil 38 so as to face each other in the vertical direction.
  • the magnetic field formed by the energized main coil 38 and the main magnetic pole 35 is called a main magnetic field.
  • the acceleration region is a region for accelerating the beam in the main magnetic field.
  • the yoke 37 has a plurality of through holes. Among them, a through hole 44 for a beam, a through hole 47 for a coil, a through hole 48 for evacuation, and a through hole 49 for a high frequency system are provided on the connection surface of the yoke 37.
  • the beam through hole 44 is a through hole for emitting an accelerated beam.
  • the coil through hole 47 is a through hole for pulling out various coil conductors inside the yoke 37 to the outside.
  • the evacuating through hole 48 is a through hole for evacuating the inside of the yoke 37.
  • the high frequency system through hole 49 is a through hole for providing the high frequency acceleration cavity 10.
  • the high frequency acceleration cylinder 10 is a ⁇ / 2 resonance type cylinder, and has a dee electrode 12, a dummy dee electrode 13, an inner conductor 14, an outer conductor 15, and a rotary capacitor 31.
  • the D electrode 12 is a D-shaped hollow electrode and is connected to the inner conductor 14.
  • the dummy D electrode 13 is an electrode connected to the outer conductor 15 that encloses the inner conductor 14, and has a ground potential.
  • the dummy dee electrode 13 forms an acceleration gap 11 with the dee electrode 12.
  • An acceleration voltage frequency-modulated by the rotating capacitor 31 is generated in the acceleration gap 11 between the dee electrode 12 and the dummy dee electrode 13.
  • the acceleration gap 11 illustrated in FIG. 2 is when the number of harmonics is 1, that is, when the orbital frequency and the acceleration frequency are the same. Further, the shape of the acceleration gap 11 is designed according to the trajectory shape of the beam.
  • the input coupler 20 is a device for supplying high-frequency power to the high-frequency accelerating cavity 10, and is connected to the inner conductor 14 by an electrostatic coupling type or a magnetic coupling type. Power is supplied to the input coupler 20 from the acceleration high frequency power supply 21, and high frequency power is supplied to the inner conductor 14 through the input coupler 20. As a result, a high-frequency acceleration voltage for accelerating the beam is generated in the acceleration gap 11 between the dee electrode 12 and the dummy dee electrode 13, and a high-frequency electric field is generated by the high-frequency acceleration voltage.
  • the rotary capacitor 31 is a device for modulating the resonance frequency of the high-frequency acceleration cavity 10, and includes a motor 32, a fixed electrode 33, and a rotary electrode 34 facing the fixed electrode 33.
  • the fixed electrode 33 is formed on the inner conductor 14.
  • the rotating electrode 34 is adjacent to the outer conductor 15, and although it is not physically connected to the outer conductor 15, it is electrically connected to the outer conductor 15 via a capacitance. Note that this configuration is an example, and as another configuration, the fixed electrode 33 may be formed on the outer conductor 15 and the rotating electrode 34 may be electrostatically coupled to the inner conductor 14.
  • the beam incident on the circular accelerator 30 from the ion source 50 is accelerated by a high-frequency electric field and orbits in the main magnetic field while increasing energy.
  • the trajectory of the beam becomes spiral with the radius of curvature increasing as the beam accelerates.
  • the orbit that the beam passes from the start of acceleration to the maximum energy is called an orbit.
  • the orbit through which the beam of maximum energy passes is referred to as the maximum energy beam orbit 80.
  • the surface on which the orbit draws a spiral is called the orbital plane.
  • the main magnetic field has an n value larger than 0 and the n value represented by the equation (1) is larger than 0.
  • the beam stabilization condition of less than 1 is satisfied.
  • ⁇ is the deflection radius of the ideal design trajectory (hereinafter referred to as "design trajectory")
  • Bz is the magnetic field strength
  • ⁇ Bz / ⁇ r is the magnetic field gradient in the r direction. ..
  • a beam that deviates slightly in the radial direction from the design orbit receives a restoring force in the direction of returning to the design orbit.
  • the beam displaced in the vertical direction with respect to the orbital plane also receives a restoring force from the main magnetic field in the direction of returning to the orbital plane.
  • the vibration of the beam generated by these is called the betatron vibration, and the frequency of the betatron vibration is called the betatron frequency.
  • the main magnetic field ⁇ Bz / ⁇ r is designed so that the beam can stably orbit and accelerate the beam while betatron vibrating in the vicinity of the design trajectory.
  • the frequency per orbit is called tune, and the displacement of the beam to the outside of the orbital plane per orbit is called turn separation.
  • the betatron vibration in the orbital plane and in the direction orthogonal to the trajectory of the beam is called the horizontal betatron vibration, and the tune of the horizontal betatron vibration is called the horizontal tune.
  • Resonance increases the amplitude of betatron oscillations when the appropriate high frequency voltage of the beam is applied.
  • the horizontal tune ⁇ r is set to a value close to 1 for the entire range of beam energy.
  • main magnetic field distribution The magnetic field distribution of the main magnetic field described above (hereinafter referred to as "main magnetic field distribution") is formed by the main magnetic pole 38 and the trim coil and / or the magnetic pole piece installed on the surface of the main magnetic pole 38. These components forming the main magnetic field distribution are arranged symmetrically with respect to the orbital plane. Therefore, the main magnetic field has only the magnetic field component in the direction perpendicular to the orbital plane on the orbital plane.
  • the circular accelerator 30 of this embodiment has a high-frequency kicker 81, a septum coil 41, and a high-energy beam transport system 45 as devices for emitting a beam.
  • the beam accelerated by the circular accelerator 30 is emitted from the beam emission path inlet 82 to the outside of the acceleration region.
  • the septum coil 41 is arranged at the beam emission path inlet 82. Two or more septum coils 41 may be arranged along the beam traveling direction.
  • the high energy beam transport system 45 is a transport system for transporting an emitted beam from the inside of the main electromagnet 40 to the outside.
  • the high energy beam transport system 45 is arranged at a position after the septum coil 41, passing through the beam through hole 44 and extending to the outside of the main electromagnet 40.
  • the high frequency kicker 81 is a device that applies a high frequency voltage to the beam passing through the inside thereof.
  • the septum coil 41 is a coil for deflecting a beam toward the outer peripheral side in the horizontal direction, and has two coil conductors (not shown).
  • the septum coil 41 is on the outer peripheral side of the acceleration region, and one coil conductor is in contact with the acceleration region. By passing a current through the two coil conductors, a magnetic field in the vertical direction with respect to the orbit around the beam is generated inside the septum coil 41. The beam that has entered the inside of the septum coil 41 is deflected by the magnetic field and transported to the high energy beam transport system 45.
  • a peeler magnetic field region 42 and a regenerator magnetic field region 43 which are disturbing magnetic fields composed of a bipolar magnetic field or a multipolar magnetic field, are formed.
  • the peeler magnetic field region 42 is arranged on the upstream side and the regenerator magnetic field region 43 is arranged on the downstream side in the orbit around which the beam circulates, sandwiching the beam emission path inlet 82 and the high frequency kicker 81.
  • the peeler magnetic field region 42 and the regenerator magnetic field region 43 are used to emit the beam.
  • the beam When the beam is accelerated to the maximum energy in the acceleration gap 11 to which the high frequency acceleration voltage is applied, the application of the frequency acceleration voltage to the acceleration gap 11 is stopped. As a result, the beam orbits on the maximum energy beam trajectory 80.
  • a high frequency kicker 81 is installed in the maximum energy beam orbit 80.
  • the amplitude of the betatron vibration of the beam increases due to the high frequency voltage generated by the high frequency kicker 81.
  • the beam with increased betatron vibration amplitude eventually reaches the peeler magnetic field region 42 and the regenerator magnetic field region 43 installed on the outer peripheral side of the maximum energy beam orbit 80 at a predetermined distance from the maximum energy beam orbit 80. ..
  • the beam that has reached the peeler magnetic field region 42 is kicked to the outer peripheral side of the orbital plane.
  • the beam that has reached the regenerator magnetic field region 43 is kicked to the inner peripheral side of the orbital plane.
  • the kick by the quadrupole magnetic field component of the peeler magnetic field region 42 further increases the amplitude of the betatron vibration of the beam and increases the turn separation of the beam.
  • the magnetic field in the regenerator magnetic field region 43 suppresses abrupt fluctuations in the horizontal tune of the beam, and before the beam is emitted from the circular accelerator 30, betatron vibration occurs in the vertical direction orthogonal to the horizontal direction. It prevents the beam from diverging and being lost.
  • the beam enters the septum coil 41 and is kicked to the outside of the raceway surface by the septum coil 41.
  • the beam kicked by the septum coil 41 passes through the high energy beam transport system 45 and is emitted to the outside of the circular accelerator 30.
  • the amount generated by the peeler magnetic field region 42 and the regenerator magnetic field region 43 is much larger than the amount generated by the high frequency kicker 81. Therefore, by adjusting the high-frequency voltage applied by the high-frequency kicker 81, the amount of the beam that reaches the peeler magnetic field region 42 and the regenerator magnetic field region 43 among the beams that orbit the maximum energy beam orbit 80 is adjusted. Can be done. As a result, if the application of the high frequency voltage to the high frequency kicker 81 is stopped during the beam emission, the beam can be prevented from reaching the peeler magnetic field region 42 and the regenerator magnetic field region 43, and the beam from the circular accelerator 30 can be prevented. Can be interrupted.
  • the emission of the beam can be restarted. Further, by controlling one or more of the strength, amplitude, phase, and frequency of the high frequency voltage applied to the high frequency kicker 81, the strength of the beam emitted from the circular accelerator 30 can be controlled.
  • the peeler magnetic field region 42 and the regenerator magnetic field region 43 are regions in which a multipolar magnetic field acting on the beam passing therethrough exists.
  • This multipolar magnetic field contains at least a quadrupole magnetic field component.
  • This multipolar magnetic field may further include a multipolar magnetic field having four or more poles or a bipolar magnetic field.
  • the peeler magnetic field region 42 has a magnetic field gradient such that the main magnetic field weakens toward the outer peripheral side in the radial direction.
  • the regenerator magnetic field region 43 has a magnetic field gradient such that the main magnetic field becomes stronger toward the outer peripheral side in the radial direction.
  • As the peeler magnetic field region 42 a region where the main magnetic field decreases at the magnetic pole end can also be used.
  • the peeler magnetic field region 42 and the regenerator magnetic field region 43 are arranged on the outer peripheral side of the maximum energy beam orbit 80 in regions having a predetermined azimuth angle with the beam emission path inlet 82 interposed therebetween. Further, the peeler magnetic field region 42 and the regenerator magnetic field region 43 have a maximum energy beam trajectory 80 so that the beam before the betatron vibration amplitude is increased by the high frequency kicker 81 does not enter the peeler magnetic field region 42 or the regenerator magnetic field region 43. Therefore, it is desirable that the betatron vibration is arranged at a position on the outer peripheral side by a width larger than the amplitude before resonance. Further, it is desirable that the peeler magnetic field region 42 is arranged on the upstream side in the beam traveling direction with respect to the beam emission path inlet 82 and the regenerator magnetic field region 43 is arranged on the downstream side, but vice versa.
  • a plurality of magnetic pole pieces or coils, or both are fixedly arranged on the yoke 37 by a non-magnetic material to form a desired multipolar magnetic field.
  • a multipolar magnetic field is formed by a plurality of magnetic pole pieces
  • a bipolar magnetic field is formed by a coil.
  • the plurality of magnetic pole pieces and the coil can be arranged close to each other, or can be arranged at spatially separated positions.
  • FIG. 4 is a graph showing the distribution of the main magnetic field on the r-axis shown in FIG.
  • the magnetic field strength Bz of the main magnetic field shows a magnetic field gradient ⁇ Bz / ⁇ r that slightly decreases from the center of the acceleration region to the maximum energy beam orbit 80 on the r-axis.
  • the n value of the equation (1) satisfies the stabilization condition, and the beam orbits stably.
  • the magnetic field gradient ⁇ Bz / ⁇ r is shown so that the magnetic field strength Bz of the main magnetic field rises sharply. In this region, the beam is not stable and is kicked to the inner circumference of the orbital plane.
  • the magnetic field strength Bz drops sharply in the peeler magnetic field region 42, contrary to the regenerator magnetic field region 43.
  • the magnetic field gradient ⁇ Bz / ⁇ r is shown.
  • the beam is not stable as in the regenerator magnetic field region 43, and the beam is kicked to the outer peripheral side of the orbital plane, contrary to the regenerator magnetic field region 43.
  • the peeler magnetic field region is used to emit the beam from the circular accelerator 30.
  • the configuration using 42 and the regenerator magnetic field region 43 was illustrated. However, it is not limited to this configuration.
  • the beam may be emitted from the circular accelerator 30 due to the effect of the high frequency kicker 81 increasing the amplitude of the betatron vibration without using the peeler magnetic field region 42 and the regenerator magnetic field region 43.
  • the position where the high frequency kicker 81 is arranged may be on the maximum energy beam trajectory 80 and is not particularly limited, but here, as an example, the high frequency kicker 81 is arranged in the vicinity of the beam emission path inlet 82 as shown in FIG. ..
  • betatron vibration has the property that the amplitude increases resonantly when the product of either one of the tune or the fractional part of the tune and the frequency of the beam is substantially the same as the frequency of the applied high frequency voltage.
  • the frequency frequency of the high frequency voltage applied by the high frequency kicker 81 is the product ⁇ r of the decimal part ⁇ r of the horizontal tune ⁇ r of the maximum energy beam and the orbital frequency f rev of the maximum energy beam. It should be substantially the same as r ⁇ f rev .
  • the amplitude of the horizontal betatron vibration continues to increase resonantly, and eventually the beam reaches the peeler magnetic field region 42 and the regenerator magnetic field region 43.
  • the frequency frequency of the high frequency voltage applied by the high frequency kicker 81 is set to be equal to the product ⁇ r ⁇ f rev of the horizontal tune ⁇ r of the maximum energy beam and the circumferential frequency f rev of the maximum energy beam. May be good.
  • the septum coil 41 is installed at the beam emission path inlet 82. Eventually, when the turn separation is obtained so that the beam greatly exceeds the thickness of the coil conductor installed on the inner peripheral side of the septum coil 41, the beam is guided to the inside of the septum coil 41 and is guided by the septum coil 41. It is sufficiently deflected, guided to the high energy beam transport system 45, and emitted from the circular accelerator 30.
  • the linear coupling between the horizontal tune ⁇ r and the vertical tune ⁇ z at the time of emission matches a half-integer or an integer
  • a resonance phenomenon of betatron vibration called resonance is excited and beam divergence occurs.
  • the beam current can be increased by suppressing the beam divergence due to the resonance called Walkinshaw resonance.
  • Walkinshaw resonance occurs when the condition represented by the equation (2) is satisfied by the horizontal tune ⁇ r and the vertical tune ⁇ z .
  • resonance has a width called resonance width in which resonance is excited, and in reality, resonance occurs if the right side of equation (2) is equal to or less than the predetermined resonance width ⁇ .
  • the resonance width ⁇ is expressed by the equation (3).
  • Equation (3) Jr is a canonical transformation of the horizontal particle coordinates with the design trajectory as the origin.
  • G is a complex number represented by the equation (4) and is called a driving term.
  • j is an imaginary unit.
  • ⁇ is any phase.
  • s is the coordinates of the beam traveling direction.
  • ⁇ r and ⁇ z are the phase leads of the horizontal and vertical betatron oscillations, respectively.
  • ⁇ is an angular coordinate in the traveling direction coordinate s.
  • k 2 is obtained by dividing the second derivative of B z in the r direction by B ⁇ , and represents the magnitude of the hexapolar magnetic field component.
  • the resonance width ⁇ becomes 0, and resonance can be generated only when the equation (2) is satisfied, so that the beam diverged by the resonance can be reduced.
  • the magnitude of the driving term is set to 0 or its vicinity by applying a resonance suppression magnetic field 46 that corrects k 2 to an arbitrary section in the s direction of the outer circumference of the maximum energy beam orbit 80.
  • the beam diverges between the inner wall and the cylindrical region where the static magnetic field is formed inside the yoke 37, separately from the magnetic fields (peer magnetic field and regenerator magnetic field) for allowing the beam to enter the beam emission path.
  • a magnetic field for suppression (resonance suppression magnetic field 46)
  • the resonance suppression magnetic field 46 is created outside the region through which the beam passes during acceleration when viewed radially. It is possible to effectively suppress the increase in the amplitude of the betatron vibration due to the orbiting and accelerated beam reaching the inner wall of the yoke 37. Further, the resonance suppression magnetic field 46 is arranged on the upstream side of the peeler magnetic field region 42 and the downstream side of the acceleration gap 11 in the orbit around the beam when viewed in the orbital direction.
  • the multipolar magnetic field component included in the resonance suppression magnetic field 46 may be, for example, a multipolar magnetic field component having four or more poles. By applying the multipolar magnetic field component, the magnitude of the driving term can be brought close to zero and the resonance width can be brought close to zero.
  • the main electromagnet 40 includes a generator that creates a resonance suppression magnetic field 46, and the generator may be, for example, a coil, a magnetic pole piece, or both installed on the surface of the main magnetic pole 38. If the resonance suppression magnetic field 46 is formed by the coil, the degree of freedom of adjustment is increased, and a robust device can be realized. Alternatively, the generator that creates the resonance suppression magnetic field 46 may be an iron piece installed on the surface of the main magnetic pole 38. Since the resonance suppression magnetic field 46 is formed of iron pieces, it is not necessary to excite each time it is used, and it is possible to realize easy and rapid use of the device.
  • FIG. 5 is a graph showing the distribution of the magnetic field strength Bz in the r direction in the region including the resonance suppression magnetic field 46.
  • the magnetic field strength Bz shown in FIG. 5 is corrected by the resonance suppression magnetic field 46.
  • the resonance suppression magnetic field 46 is applied to only one place.
  • a plurality of resonance suppression magnetic fields 46 may be present in any region in the s direction.
  • the product of the first power of the horizontal betatron vibration amplitude ⁇ r and the square of the vertical betatron vibration amplitude ⁇ z is used.
  • the magnitude of the hexapolar magnetic field component and the driving term become large in the region where the product of the amplitude of the horizontal betatron vibration and the square of the amplitude of the vertical betatron vibration is large, so that the horizontal betatron
  • the resonance width can be reduced by providing a second magnetic field that reduces the magnitude of the hexapole magnetic field component. ..
  • the product of the horizontal betatron vibration amplitude ⁇ r to the real number power and the vertical betatron vibration amplitude ⁇ z to the real number power can be used.
  • the resonance width can be set to 0.
  • the circular accelerator of this embodiment forms a main magnetic field so as to eccentric the trajectory of the beam toward the beam exit path inlet 82 so that the energy of the emitted beam can be arbitrarily changed between 70 MeV and 235 MeV. It is an eccentric orbital accelerator.
  • FIG. 6 is an external view of the circular accelerator 30 of the second embodiment.
  • FIG. 7 is a cross-sectional view of the eccentric orbital accelerator of Example 2 cut along the central plane.
  • FIG. 8 is a cross-sectional view of the eccentric orbital accelerator of the second embodiment in the vertical direction (AA'arrow view of FIG. 7).
  • the radius of the orbit around the beam increases as the beam accelerates, and the center of the orbit moves in a predetermined direction (to the right in FIG. 7) as the radius increases. do.
  • the direction opposite to the direction in which the center of the orbit moves there is a region where the orbit becomes dense according to the velocity, and the beam emission path inlet 82 is arranged in the vicinity of the region. Since the orbit becomes dense in the vicinity of the beam emission path inlet 82, a beam of desired energy can be easily emitted.
  • the structural changes from the circular accelerator of Example 1 shown in FIGS. 2 and 3 in the eccentric orbital accelerator shown in FIGS. 7 and 8 include the shapes of the dee electrode 12 and the dummy dee electrode 13. There is a shape of the acceleration gap 11 formed between them.
  • the line passing through the rotation axis of the rotary capacitor 31 and the center of the circle in the acceleration region is used as the center line.
  • the ion incident portion 52 is arranged on the center line at a position closer to the beam emission path inlet 82 side than the center of the acceleration region.
  • the shape of the vertically opposed surfaces of the main magnetic pole 38 is also significantly different from that of the first embodiment in order to form the main magnetic field described later.
  • the structure of the high-frequency kicker 81 is also different from that of the first embodiment because a high-frequency electric field is applied to a plurality of energy trajectories.
  • FIG. 9 shows a conceptual diagram of the design trajectory for each energy.
  • the dotted line is a line connecting the same orbital phases of each orbit, and is called an equal orbital phase line.
  • the acceleration gap 11 formed between the dee electrode 12 and the dummy dee electrode 13 facing the dee electrode 12 is installed along the equicircling phase line.
  • the Dee electrode 12 has two curves whose tip is near the center of the lowest emission energy orbit 83 and reaches the circumference along the equicircumferential phase line from the tip, and two curves thereof. It has a hollow shape like a fan surrounded by an arc connecting the reached points on the circumference. Further, the dummy dee electrode 13 has a shape having two curves facing each of the above two curves of the dee electrode 12 in its outer shape.
  • the orbit of the beam In the region where the energy of the beam is low, the orbit of the beam is close to the concentric orbit centered on the vicinity of the ion incident portion 52 like the cyclotron. However, in the region where the energy is larger, the orbits of the beam are densely concentrated in the vicinity of the beam exit path inlet 82, and conversely, the orbits of the respective energies are separated from each other in the vicinity of the inner conductor 14.
  • the region where these orbits are densely gathered is called the aggregate region, and the discrete region is called the discrete region.
  • the magnetic field distribution is such that the magnetic field strength of the main magnetic field decreases toward the outer peripheral side in the radial direction. It is formed by the shape of the main magnetic pole 38 and the trim coil and / or the magnetic pole piece installed on the surface thereof.
  • the main magnetic field is a constant value on the line along the design trajectory. Therefore, the design trajectory at each energy is circular.
  • a high-frequency kicker 81 installed near the aggregation region where the trajectories of all energy beams are aggregated in order to emit a beam from the circular accelerator 30, and a peeler magnetic field region 42 and a regenerator magnetic field region 43 arranged on both sides thereof. , The septum coil 41, and the high energy beam transport system 45 are used.
  • the configuration of the high frequency kicker 81 is different from that of the first embodiment.
  • the procedure for emitting the beam is basically the same as that described in the first embodiment.
  • the timing of cutting off the high-frequency acceleration voltage applied to the acceleration gap 11 and the timing of starting the application of the high-frequency voltage to the high-frequency kicker 81 are shifted forward, a beam of arbitrary energy can be emitted.
  • the amplitude of the betatron vibration of the beam of the desired energy is increased by the high frequency kicker 81.
  • the beam reaches the peeler magnetic field region 42 and the regenerator magnetic field region 43, and is emitted from the circular accelerator 30.
  • the circular accelerator 30 of this embodiment is also a circular accelerator in which the n value of the formula (1) satisfies the stabilization condition, as in the case of the first embodiment. It is possible to increase the current of the beam by suppressing the divergence of the beam by resonance called Walkinshaw resonance. Similar to the circular accelerator of the first embodiment, in the second embodiment, the beam emitted by the resonance can be reduced by setting the size of the driving term to 0. Further, from the equation (4), the magnitude of the driving term is set to 0 or its own by applying the resonance suppression magnetic field 46 for correcting k2 to an arbitrary section in the s direction of the outer circumference of the maximum energy beam orbit 80. It becomes possible to make it in the vicinity.
  • FIG. 10 shows the relationship between the amplitude ⁇ r and the phase ⁇ of the horizontal betatron vibration for each energy.
  • FIG. 11 shows the relationship between the amplitude ⁇ z of the vertical betatron vibration for each energy and the phase ⁇ .
  • the second is such that the magnitude of the hexapolar magnetic field component is reduced in the vicinity thereof.
  • the resonance width can be reduced.
  • the circular accelerator 30 of this embodiment may have a plurality of resonance suppression magnetic fields 46 in any region in the s direction.
  • the Walkinshaw resonance has been described, but similarly to other types of resonance, the resonance width is set to 0 by applying a multipolar magnetic field component so as to make the magnitude of the driving term 0. Can be.
  • Example 3 a particle beam therapy device using a circular accelerator will be described.
  • FIG. 12 is an overall configuration diagram of the particle beam therapy apparatus of Example 3.
  • the particle beam therapy device includes a circular accelerator 30, a rotary gantry 90, an irradiation device 92 including a scanning electromagnet, a treatment table 101, and a control device 91 for controlling them, as shown in Example 1 or Example 2.
  • the beam emitted from the circular accelerator 30 is transported to the irradiation device 92 by the rotating gantry 90.
  • the ion beam transported to the irradiation device 92 is formed according to the affected area by adjusting the beam energy in the irradiation device 92, and irradiates a predetermined amount to the affected area of the patient 100 lying on the treatment table 101.
  • the irradiation device 92 includes a dose monitor and monitors the dose irradiated to each irradiation spot on the patient 100. Based on this dose data, the treatment control device 91 calculates the required dose to each irradiation spot and uses it as input data to the accelerator control device 93. The accelerator control device 93 controls the incident, accelerated, and emitted of the charged particle beam in the circular accelerator 30.
  • Resonance suppression magnetic field 47 ... Coil through hole, 48 ... Vacuum pulling through hole, 49 ... High frequency system through hole, 50 ... Ion source, 51 ... Low energy beam transport system, 52 ... Ion incident part, 53 ... Electrostatic inflator, 80 ... Maximum energy beam trajectory, 81 ... High frequency kicker, 82 ... Beam emission Path entrance, 83 ... Minimum emission energy trajectory, 90 ... Rotating gantry, 91 ... Treatment control device, 91 ... Control device, 92 ... Irradiation device, 93 ... Accelerator control device, 100 ... Patient, 101 ... Treatment table

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Abstract

L'invention concerne une caractéristique qui réduit la perte de faisceau à partir d'une oscillation de bêtatron entre un champ magnétique et une paroi interne d'accélérateur. Un accélérateur selon la présente invention comprend : un électroaimant principal qui constitue une région cylindrique à l'intérieur d'une culasse et qui forme un champ magnétique statique dans la région cylindrique; un trajet d'émission de faisceau qui transporte un faisceau de particules chargées depuis l'intérieur de l'électroaimant principal vers l'extérieur de celui-ci; un applicateur de champ électrique d'accélération qui applique un champ électrique d'accélération modulé en fréquence pour accélérer le faisceau de particules chargées circulant dans le champ magnétique statique; et un éjecteur qui amplifie l'oscillation de bêtatron du faisceau de particules chargées accéléré par le champ électrique d'accélération, l'électroaimant principal créant un premier champ magnétique pour l'introduction, dans le trajet d'émission de faisceau, du faisceau de particules chargées dans lequel l'oscillation de bêtatron a été amplifiée par l'éjecteur, ainsi qu'un second champ magnétique pour supprimer la diffusion du faisceau de particules chargées entre la région de champ magnétique statique dans la culasse et une paroi interne de la culasse.
PCT/JP2021/028894 2020-12-14 2021-08-04 Accélérateur et dispositif thérapeutique à faisceau de particules Ceased WO2022130680A1 (fr)

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WO2013098089A1 (fr) * 2011-12-28 2013-07-04 Ion Beam Applications S.A. Dispositif d'extraction pour synchrocyclotron
JP2015181854A (ja) * 2014-03-26 2015-10-22 国立研究開発法人放射線医学総合研究所 粒子線照射制御装置およびその制御方法
JP2016110941A (ja) * 2014-12-10 2016-06-20 株式会社東芝 加速器および粒子線治療装置
WO2018142495A1 (fr) * 2017-02-01 2018-08-09 株式会社日立製作所 Accélérateur circulaire
US20190070438A1 (en) * 2017-09-05 2019-03-07 The Trustees Of Columbia University In The City Of New York Fixed field alternating gradient ion accelerator for variable energy extraction
JP2019133745A (ja) * 2018-01-29 2019-08-08 株式会社日立製作所 円形加速器、円形加速器を備えた粒子線治療システム、及び円形加速器の運転方法

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Publication number Priority date Publication date Assignee Title
WO2011019036A1 (fr) * 2009-08-11 2011-02-17 国立大学法人群馬大学 Procédé d'extraction de faisceaux de particules chargées mettant en œuvre une tension pulsatoire
WO2013098089A1 (fr) * 2011-12-28 2013-07-04 Ion Beam Applications S.A. Dispositif d'extraction pour synchrocyclotron
JP2015181854A (ja) * 2014-03-26 2015-10-22 国立研究開発法人放射線医学総合研究所 粒子線照射制御装置およびその制御方法
JP2016110941A (ja) * 2014-12-10 2016-06-20 株式会社東芝 加速器および粒子線治療装置
WO2018142495A1 (fr) * 2017-02-01 2018-08-09 株式会社日立製作所 Accélérateur circulaire
US20190070438A1 (en) * 2017-09-05 2019-03-07 The Trustees Of Columbia University In The City Of New York Fixed field alternating gradient ion accelerator for variable energy extraction
JP2019133745A (ja) * 2018-01-29 2019-08-08 株式会社日立製作所 円形加速器、円形加速器を備えた粒子線治療システム、及び円形加速器の運転方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119233513A (zh) * 2024-08-19 2024-12-31 国电投核力同创(北京)科技有限公司 用于消色散偏转磁铁的调节块和消色散偏转磁铁调节方法

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