WO2023162640A1 - Accelerator and particle beam treatment system comprising accelerator - Google Patents

Accelerator and particle beam treatment system comprising accelerator Download PDF

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Publication number
WO2023162640A1
WO2023162640A1 PCT/JP2023/003662 JP2023003662W WO2023162640A1 WO 2023162640 A1 WO2023162640 A1 WO 2023162640A1 JP 2023003662 W JP2023003662 W JP 2023003662W WO 2023162640 A1 WO2023162640 A1 WO 2023162640A1
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frequency
ions
accelerator
magnetic field
electric field
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PCT/JP2023/003662
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French (fr)
Japanese (ja)
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孝道 青木
武一郎 横井
風太郎 ▲えび▼名
裕人 中島
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株式会社日立製作所
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Publication of WO2023162640A1 publication Critical patent/WO2023162640A1/en

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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
    • H05H7/10—Arrangements for ejecting particles from orbits

Definitions

  • the present invention relates to an accelerator and a particle beam therapy system comprising the accelerator.
  • High-energy ion beams used in particle beam therapy and physical experiments are generated using accelerators.
  • accelerators There are several types of accelerators that obtain beams with a kinetic energy of around 200 MeV per nucleon.
  • a cyclotron, a synchrotron, a synchrocyclotron as described in Patent Document 1, and a variable energy accelerator as described in Patent Document 2 are known.
  • a feature of cyclotrons and synchrocyclotrons is that they accelerate a beam circulating in a static magnetic field with a high-frequency electric field.
  • the beam increases the radius of curvature of its trajectory as it is accelerated, moves to outer trajectories, reaches maximum energy and is then extracted. Therefore, the energy of the extracted beam is basically fixed.
  • a pair of ferromagnetic poles having a substantially circular cross section with a radius R are arranged vertically with the median plane interposed therebetween with their central axes aligned.
  • a pair of poles are separated by a gap that defines a cavity having a substantially symmetrical profile with respect to the median plane.
  • the height of the gap varies in the radial direction of the pole.
  • the height of the gap is Hcenter at the center axis, and in the circular portion from the center axis to the radius R2, the height gradually increases from Hcenter as the radius increases, reaching a maximum value Hmax at the radius R2.
  • the annular portion larger than the radius R2 gradually decreases in gap height as the radius increases, and the gap height at the edge of the pole is Hedge.
  • a synchrocyclotron with such a gap-shaped cavity is disclosed in US Pat. No. 6,300,000 to minimize the size of the synchrocyclotron while minimizing the magnetic field in the gap.
  • Patent Document 2 discloses an orbital accelerator that accelerates a beam by a main magnetic field and a frequency-modulated high-frequency electric field as a compact accelerator capable of extracting a beam of variable energy, and is capable of frequency modulation.
  • an acceleration high-frequency applying device for applying an accelerating high-frequency wave for accelerating the beam;
  • an extracting high-frequency applying device for applying an extracting high-frequency wave having a different frequency from the accelerating high-frequency wave for extracting the beam; and a magnetic field having a number of poles of two or more.
  • a septum electromagnet having a magnetic shim and a septum coil. Accelerators are described.
  • variable energy accelerator of Patent Document 2 the energy of the extraction beam is variable, so it is possible to emit a beam with an energy that matches the irradiation dose determined in the treatment plan. Therefore, the variable energy accelerator can shorten the beam irradiation time of particle beam therapy compared to the synchrocyclotron.
  • the variable energy accelerator is equivalent in accelerator size to cyclotrons and synchrocyclotrons, and is small. Therefore, the variable energy accelerator is expected to further shorten the beam irradiation time as an accelerator of a particle beam therapy system.
  • the accelerator operates in a cycle of about several milliseconds.
  • an ion beam (hereafter referred to as a beam) is extracted during the period during which ions are injected from the ion source into the accelerator, the period during which the ions are accelerated, and the period from when all the injected ions are irradiated until they are injected again. I can't.
  • the purpose of the present invention is to provide an accelerator capable of efficiently generating beams and a particle beam therapy system equipped with the accelerator.
  • an accelerator according to the present invention is an orbital accelerator that accelerates ions supplied from an ion source to generate a beam by means of a main magnetic field and a frequency-modulated high-frequency electric field.
  • a stray magnetic field region forming portion to form and a septum electromagnet for beam extraction are provided, and new ions are supplied from the ion source and accelerated during beam extraction.
  • beams can be efficiently generated and extracted.
  • FIG. 1 is an overall schematic diagram of an accelerator of Example 1.
  • FIG. Internal structure of the accelerator FIG. 10 is a diagram showing the relationship between beam energy during circulation and circulation frequency. Explanatory drawing of a design track
  • FIG. 11 is a diagram showing the relationship between the beam energy during orbit and the design on-orbit magnetic field. Schematic diagram of high frequency modes excited in the Dee electrode. Schematic diagram of a high frequency bucket. Explanatory drawing which shows the phase space just before the end of acceleration. Explanatory drawing which shows the phase space immediately after the completion
  • finish of acceleration. Accelerator control block diagram. Timing chart of accelerator operation. 4 is a flowchart showing control processing of an accelerator; 4 is a flowchart of processing for measuring beam amount; FIG. 10 is a structural example of a high-frequency cavity according to Example 3; FIG. Overall configuration diagram of a particle beam therapy system.
  • the accelerator will be explained below based on the drawings.
  • temporally serial processes of injection of ions output of ions
  • acceleration of injected ions acceleration of injected ions
  • extraction of accelerated ions deceleration
  • the injection process and the acceleration process are repeatedly performed to maintain a state in which the beam corresponding to the irradiation energy is constantly replenished in the accelerator.
  • the injection process, the acceleration process, and the extraction process can be executed in parallel, so that the time during which the beam cannot be irradiated can be shortened and the efficiency can be improved.
  • the accelerator 1 includes a high-frequency acceleration cavity 21 that forms an acceleration electric field for accelerating ions, and a rotary variable cavity for modulating the frequency of the acceleration electric field.
  • An additional magnetic field generating shim 311 that gives a kick action from the stable region to the ions orbiting by the magnetic field formed by the capacitance capacitor 212 and the magnetic pole 123, and the ions given the kick action by the additional magnetic field generating shim 311 are transferred to the accelerator.
  • a plurality of annular circulating trajectories of ions, each circulating, has a converging region and a discrete region, and ions injected in different cycles circulate at the same time with approximately the same energy.
  • FIG. 1 A first embodiment will be described with reference to FIGS. 1 to 13.
  • FIG. 1 The accelerator 1 of this embodiment is a frequency modulated variable energy accelerator.
  • This accelerator has a temporally constant magnetic field as its main magnetic field, and is a circular accelerator that accelerates protons orbiting in the main magnetic field by a high-frequency electric field. Its appearance is shown in FIG.
  • the accelerator 1 uses electromagnets 11 that can be divided vertically to generate a main magnetic field in a region through which the beam passes during acceleration and circling (hereinafter referred to as a beam passage region 20 (see FIG. 2)).
  • Electromagnet 11 is an example of a "pair of magnets.” The inside of the electromagnet 11 is evacuated by a vacuum pump (not shown).
  • the electromagnet 11 is provided with a plurality of through holes for connecting the outside and the beam passage area 20 .
  • through-hole 111 for extraction beam for taking out the accelerated beam through-holes 112 and 113 for drawing out the coil conductor arranged in electromagnet 11 to the outside, through-hole 114 for high-frequency power input, etc.
  • Through holes are provided on the upper and lower split connection surfaces of the electromagnet 11 .
  • a high-frequency acceleration cavity (acceleration electrode) 21 is installed through the high-frequency power input through-hole 114 to form an acceleration electric field for accelerating ions into an ion beam.
  • the high-frequency acceleration cavity 21, which is an example of the "high-frequency acceleration applying device" includes a dee electrode 221 for acceleration (see FIG. 2) and a rotary variable capacitor for modulating the frequency of the electric field for acceleration.
  • a capacitor (modulation unit) 212 is installed.
  • An ion source 12 for supplying hydrogen ions is installed at a position shifted from the center of the upper part of the electromagnet 11 .
  • the ion source 12 injects ions between the electromagnets 11 inside the accelerator 1 through the beam injection through-hole 115 and the injection section 130 (see FIG. 2). Electric power necessary for injecting ions into the beam passing region 20 is supplied from the outside to the injection section 130 through the through hole 115 .
  • FIG. 2 is a diagram showing the arrangement of equipment when a plane obtained by dividing the electromagnet 11 into upper and lower parts is viewed from above.
  • the upper and lower portions of the electromagnet 11 each have a cylindrical return yoke 121 and a top plate 122, and a cylindrical magnetic pole 123 is provided inside them, as shown in FIG. have.
  • the beam passing region 20 described above is present in the cylindrical space sandwiched by the magnetic poles 123 facing each other vertically.
  • a surface where the upper and lower magnetic poles 123 face each other is defined as a magnetic pole surface.
  • a plane sandwiched between magnetic pole faces and parallel to the magnetic pole face and equidistant from the upper and lower magnetic pole faces is called a track surface.
  • the annular coil 13 is installed along the wall on the outer peripheral side of the magnetic pole 123.
  • the magnetic poles 123 facing up and down are magnetized, and a magnetic field is excited in the beam passing region 20 with a predetermined distribution, which will be described later.
  • the high frequency acceleration cavity 21 excites an acceleration high frequency electric field for accelerating ions into the acceleration gap 223 by a ⁇ /4 type resonance mode.
  • a portion of the high-frequency acceleration cavity 21 that is fixedly installed with respect to the accelerator 1 is defined as a Dee electrode 221 .
  • the high frequency acceleration cavity 21 forms a dee electrode 221 surrounding a partial area of the beam passage area 20 through the through hole 114 . Ions are accelerated by a high-frequency electric field excited by an acceleration gap 223 which is a region sandwiched between a Dee electrode 221 and a ground electrode 222 arranged to face the Dee electrode 221 .
  • the frequency of the high-frequency electric field needs to be an integer multiple of the beam's circulating frequency.
  • the frequency of the high-frequency electric field is one times the circulating frequency of the beam.
  • the magnetic pole 123 is provided with a plurality of systems of trim coils 33 for fine adjustment of the magnetic field.
  • the trim coil 33 is connected to an external power source through through holes 112 and 113 .
  • the trim coil current is adjusted before operation so as to approximate the distribution of the main magnetic field described later and realize stable betatron oscillation.
  • the ions generated by the ion source 12 are extracted to the beam passage region 20 in the state of low-energy ions by the voltage applied to the extraction electrode of the injection section 130 .
  • the injected ions are accelerated by the high-frequency electric field excited by the high-frequency acceleration cavity 21 each time they pass through the acceleration gap 223 to form an ion beam.
  • two additional magnetic field generating shims (kick portions) 311 for exciting a quadrupole magnetic field or a multipolar magnetic field of six or more poles and a high-frequency electric field are applied.
  • a disturbance electrode (disturbance portion) 313 is provided in an electrically insulated state on a part of the magnetic pole face.
  • An incident part of the extraction septum electromagnet 312 is installed at one of the ends of the magnetic pole face.
  • the disturbing electrode 313 is capable of applying a radio frequency (RF) electric field of minute amplitude, which kicks orbiting particles in the direction of the trajectory plane, causing the particles to deviate from the designed trajectory. Particles whose trajectories deviate from the designed trajectory pass near the additional magnetic field generating shim 311 .
  • RF radio frequency
  • the magnetic field generated by the additional magnetic field generating shim 311 restricts the stable region of the ion beam circulating in the beam passing region 20, and introduces the particles outside the stable region to the extraction septum electromagnet 312.
  • the pair of additional magnetic field generating shims 311 superimpose and excite magnetic fields of opposite polarities on the main magnetic field formed by the magnetic poles 123 .
  • the beam When the beam is disturbed by applying a high-frequency voltage of an appropriate frequency to the disturbing electrode 313, the beam is turned on/off in synchronization with the on/off of the RF electric field applied to the disturbing electrode 313 according to the principle described later. /OFF control becomes possible. Details of the additional magnetic field generating shim 311 and the disturbance electrode 313 will be described later.
  • the upper and lower magnetic poles 123, the coil 13, the trim coil 33, the additional magnetic field generating shim 311, the extraction septum electromagnet 312, and the disturbance electrode 313 are shaped and arranged so that the in-plane component of the main magnetic field is approximately 0 on the orbital plane. is designed, and has a symmetrical arrangement and current distribution with respect to the orbital plane.
  • the magnetic pole 123, the dee electrode 221, the coil 13, the trim coil 33, and the disturbance electrode 313 are shaped so that, as shown in FIG. The shape is symmetrical with respect to the line segment connecting the center of the
  • the trajectory and motion of the beam orbiting inside the accelerator 1 will be described.
  • the beam is accelerated while circulating in the beam passing area 20 .
  • the kinetic energy of the beam that can be extracted from the accelerator 1 is 70 MeV minimum and 235 MeV maximum. The higher the kinetic energy, the lower the circulating frequency of the beam.
  • the beam of kinetic energy immediately after incidence circulates in the beam passing region 20 at 76 MHz, and the beam reaching kinetic energy of 235 MeV at 59 MHz.
  • the relationship between these energies and the circulating frequency is as shown in FIG.
  • the vertical axis in FIG. 3 indicates the lap frequency
  • the horizontal axis in FIG. 3 indicates the kinetic energy.
  • the formed magnetic field creates a distribution that is uniform along the trajectory of the beam and that the magnetic field decreases as the energy increases. That is, a magnetic field is formed such that the magnetic field on the radially outer side is reduced. Under such a magnetic field, the betatron oscillates stably in each of the radial direction in the orbital plane of the beam and the direction perpendicular to the orbital plane.
  • Figure 4 shows the trajectory of each energy.
  • a plurality of orbits are shown in FIG.
  • FIG. 4 there is a circular orbit with a radius of 0.497 m corresponding to the orbit with the maximum energy of 252 MeV on the outermost side, and from there, a total of 51 circular orbits are shown, which are divided into 51 by the magnetic rigidity up to the energy of 0 MeV.
  • a dotted line is a line connecting the same orbital phases of each orbit, and this line is called an isometric phase line.
  • the beam trajectory center moves in one direction within the trajectory plane as the beam is accelerated.
  • the design trajectory there are places where trajectories with different kinetic energies are close to each other (regions where the loop trajectories converge) and regions where they are far from each other (regions where the loop trajectories are discrete). That is, the design trajectory of the beam is eccentric.
  • a line segment orthogonal to all the design trajectories is obtained by connecting points of the design trajectories that are farthest apart from each other. These two line segments are on the same straight line. If this straight line is defined as the axis of symmetry, the shape of the design raceway passes through the axis of symmetry and is symmetrical with respect to a plane perpendicular to the raceway surface.
  • the isochronous phase lines shown in FIG. 4 are plotted every circulating phase ⁇ /20 from the aggregated region.
  • An acceleration gap 223 formed between the Dee electrode 221 and the ground electrode 222 facing the Dee electrode 221 is set along an equicircular phase line that rotates ⁇ 90 degrees when viewed from the consolidation point.
  • the accelerator 1 has a main magnetic field distribution in which the magnitude of the magnetic field decreases toward the outside in the deflection radial direction of the design orbit.
  • the magnetic field is assumed constant along the design trajectory. Therefore, the designed trajectory is circular, and as the beam energy increases, the trajectory radius and lap time increase.
  • FIG. 5 shows the value of the magnetic field in the beam of each energy. The magnetic field reaches a maximum of 5 T at the incident portion 130 and decreases to 4.91 T at the outermost circumference.
  • the main magnetic field distribution described above is excited by magnetizing the magnetic pole 123 by passing a predetermined excitation current through the coil 13 and the trim coil 33 that assists it.
  • the distance (gap) between the magnetic poles 123 facing each other is the smallest at the injection part 130 and increases toward the outer periphery. becomes.
  • the shape of the magnetic pole 123 is symmetrical with respect to a plane (orbital plane) passing through the center of the gap, and has only a magnetic field component in a direction perpendicular to the orbital plane on the orbital plane. Further, fine adjustment of the magnetic field distribution is performed by adjusting the current applied to the trim coils 33 installed on the magnetic pole faces to excite a predetermined magnetic field distribution.
  • the high frequency acceleration cavity 21 excites an electric field in the acceleration gap 223 .
  • high-frequency power is introduced from an external high-frequency power supply (see low-level high-frequency generator 42 and amplifier 43 in FIG. 10) through input coupler 211, and a high-frequency electric field is generated in acceleration gap 223 between dee electrode 221 and ground electrode 222.
  • the electromagnetic field excited by the Dee electrode 221 is an electromagnetic field with a specific resonance frequency and spatial distribution determined by the shape of the electrode.
  • An electromagnetic field with a specific frequency and spatial distribution is called an eigenmode.
  • FIG. 6 shows the fundamental mode electromagnetic field distribution and surface current distribution.
  • the fundamental mode an electric field is generated in the same direction from the dee electrode 221 to the ground electrode 222 everywhere in the gap.
  • the accelerator 1 modulates the frequency of the electric field corresponding to the energy of the orbiting beam in order to excite a high-frequency electric field in synchronization with the orbiting of the beam.
  • the control is performed by changing the capacitance of a rotary variable capacitor 212 installed at the end of the high frequency acceleration cavity 21 .
  • the rotary variable capacitor 212 controls the electrostatic capacitance generated between the conductor plate directly connected to the rotary shaft 213 and the external conductor (both not shown) by the rotation angle of the rotary shaft 213 . That is, the rotation angle of the rotating shaft 213 is changed as the beam is accelerated.
  • low-energy ions are output from the ion source 12 and guided to the beam passing region 20 via the beam-incident through-hole 115 and the incident portion 130 .
  • the beam incident on the beam passage area 20 increases its energy and increases the radius of rotation of the trajectory while being accelerated by the high-frequency electric field.
  • the beam is then accelerated while ensuring directional stability due to the high-frequency electric field.
  • the center of gravity of the beam does not pass through the acceleration gap 223 at the time when the high-frequency electric field is maximum, but passes through the acceleration gap 223 when the high-frequency electric field decreases over time. Since the frequency of the high-frequency electric field and the circulating frequency of the beam are synchronized at a ratio of just an integral multiple, the particles accelerated by a given phase of the accelerating electric field are accelerated in the next turn with substantially the same phase. On the other hand, particles accelerated in a phase earlier than the acceleration phase are accelerated in a phase delayed in the next turn because the amount of acceleration is greater than that of particles accelerated in the acceleration phase. Conversely, particles accelerated in a phase later than the acceleration phase when present are accelerated in a phase advanced in the next turn because the amount of acceleration is smaller than that of particles accelerated in the acceleration phase.
  • Fig. 7 shows a schematic diagram of the shape of the high-frequency bucket Bu on the phase plane and the trajectory of the particles moving inside it.
  • the width of the high-frequency bucket Bu in both directions of motion is proportional to the square root of the voltage amplitude applied to the acceleration cavity, and the area of the high-frequency bucket Bu is monotonic with respect to the beam energy increase (acceleration speed) per unit time. It is known that each
  • the critical voltage Vc monotonically increases with the beam energy during acceleration. Conversely, when high-frequency power is input to the high-frequency acceleration cavity 21 so as to provide a constant voltage amplitude, the area of the high-frequency bucket Bu gradually decreases as the beam is accelerated. Under the condition that the area of the high-frequency bucket Bu gradually decreases, the momentum dispersion of the beam during acceleration also decreases.
  • the high frequency electric field applied to the high frequency acceleration cavity 21 is gradually lowered, and when the target energy is reached, the amplitude of the high frequency electric field becomes zero. 40 controls the output from the external high frequency power supply. This allows the beam to circulate stably at the target energy.
  • a high frequency is applied to the disturbance electrode 313 .
  • the frequency of the high frequency matches the frequency of the betatron oscillation of the beam.
  • the beam is disturbed depending on its position in the direction of travel, ie the time of passage through the disturbing electrode 313 . Focusing on a specific particle, since the frequency of the perturbing electric field and the orbiting betatron oscillation are the same, they resonate and the betatron oscillation amplitude of a certain particle increases.
  • the kick magnetic field excited by the additional magnetic field generating shim 311 installed outside the design orbit causes the betatron oscillation to diverge abruptly.
  • beam is displaced to As a result, the beam is introduced into the extraction septum magnet 312 .
  • the boundary between this stable region and unstable region is called a separatrix.
  • the individual particles that make up the beam are positioned in the horizontal direction of the beam by the quadrupolar magnetic field derived from the additional magnetic field generating shim 311 and the multipolar magnetic field of six or more poles.
  • the orbit is divided into a stable orbital area and an unstable orbital deviation increasing area.
  • the particles inside the separatrix continue to oscillate in betatron stably. Particles outside the separatrix undergo a large displacement in the horizontal direction with respect to the design trajectory because the kick action by the additional magnetic field generating shim 311 is accumulated for each revolution. Particles that have undergone a large displacement in the horizontal direction are moved along the extraction orbit 322 by the electric field for disturbance by the disturbance electrode 313 described later and the magnetic field formed by the septum electromagnet 312 for extraction on the extraction orbit 322 set in advance. , and is taken out of the accelerator 1.
  • the betatron oscillation amplitude of the beam stops increasing and the beam orbits within the stable region. This makes it possible to stop beam extraction.
  • suppressing the momentum dispersion of the circulating beam can suppress the spatial spread of the beam and reduce the amount of the beam lost by colliding with the septum electromagnet 312 or the like. It is valid. Therefore, it is desirable that the area of the high-frequency bucket is made as small as possible at the end of the acceleration to suppress the momentum dispersion of the beam during the orbit.
  • the attenuation of the accelerating electric field takes a certain amount of time based on the Q value of the resonance of the high-frequency accelerating cavity 21 .
  • the Q value is about 3000
  • the high frequency voltage amplitude becomes small and the high frequency bucket disappears in about 3000 cycles from the time when the power input to the high frequency acceleration cavity 21 is stopped.
  • the arrival energy of each particle varies according to the time when the high-frequency bucket collapses as the high-frequency bucket contracts. The more time it takes for the high-frequency bucket to disappear, the more the momentum dispersion of the subsequent orbiting beam spreads in proportion to that time.
  • the high frequency bucket should be kept as small as possible to improve the extraction efficiency and result. It is effective for shortening the irradiation time.
  • the high-frequency bucket may disappear during acceleration, making it impossible to accelerate the beam to the desired energy. For example, there is an optimum RF voltage amplitude value for acceleration up to 70 MeV. However, even if an attempt is made to accelerate to 235 MeV with that high-frequency voltage amplitude value, the high-frequency bucket disappears during acceleration, so acceleration to 235 MeV is not possible.
  • the accelerator 1 of this embodiment includes the voltage amplitude calculator 45 that holds the correspondence relationship between the arrival energy and the voltage amplitude described above.
  • the accelerator 1 repeats similar operations in subsequent cycles.
  • the already accelerated beam is circulating in the beam passage area 20 with a predetermined energy.
  • the high-frequency electric field that accelerates the beam in the second cycle also acts on the accelerated beam.
  • the energy of the high frequency that accelerates the beam immediately after incidence does not match the circulating frequency, so the energy only oscillates minutely. Therefore, until the beam in the second cycle approaches the energy of the accelerated beam sufficiently, the accelerated beam stably circulates with almost no change in energy or motion, and part of the beam is extracted.
  • a beam that is already circulating can also be referred to as a leading beam, and a beam that is generated after that as a trailing beam.
  • the high-frequency bucket containing the second cycle beam in the phase space becomes the accelerated beam does not have a significant effect on the accelerated beam from the radio frequency until it begins to overlap the region where the is present.
  • FIG. 8 is a schematic diagram of the distribution on the phase space at this timing.
  • a region A1 shaded in gray in FIG. 8 is a region in which the circulating beam that has already been accelerated exists, and the high-frequency bucket Bu containing the beam of the second cycle is included therein.
  • the high-frequency bucket is controlled to an appropriate shape so that the momentum dispersion is small, and its height in the momentum direction is smaller than the orbiting beam.
  • the circulating beam cannot enter the high frequency bucket and moves to another position in the phase space so as to be pushed away by the high frequency bucket.
  • FIG. 9 shows the beam distribution in the phase space at the moment the second cycle beam acceleration is completed.
  • the high frequency bucket passes through a region where the leading beam is already circling, the effect of which is to disturb the distribution of the leading beam and increase the momentum dispersion.
  • the second cycle beam (subsequent beam) spills out of the high-frequency bucket as it contracts, and is arranged in a certain area on the phase space.
  • the region on the phase space between the accelerated beam and the newly accelerated beam has a clear boundary at this timing.
  • the area A2 where the accelerated beam (preceding beam) exists is indicated by a dot pattern
  • the area A3 where the newly accelerated beam (following beam) exists is indicated by oblique lines. In this way, it is possible to add a new beam at the expense of increasing the momentum dispersion of the circulating beam.
  • FIG. 10 shows a control block diagram of the accelerator 1 of this embodiment.
  • the configuration for accelerating the beam and its control system include a rotary variable capacitor 212 attached to the high frequency acceleration cavity 21 and a rotating shaft 213 of the rotary variable capacitor 212 (see FIG. 1). ), and a motor control device 41 that controls the servo motor 214 . Further, there is an input coupler 211 (see FIG. 1) for inputting high frequency power to the high frequency acceleration cavity 21, and a low level high frequency generator 42 and amplifier 43 for generating the high frequency power to be supplied.
  • the rotary variable capacitor 212 is controlled by the motor control device 41 .
  • the motor control device 41 is controlled by the overall control device 40 .
  • the overall control device 40 controls the motor control device 41 based on the indicated values predetermined by the treatment plan data in the treatment plan database 60 .
  • the rotary shaft 213 rotates.
  • the capacitance is temporally modulated by temporally changing the rotation angle of the rotating shaft 213 . This changes the resonant frequency of the fundamental mode.
  • a high frequency input to the high frequency acceleration cavity 21 is generated by amplifying the high frequency signal generated by the low level high frequency generator 42 with the amplifier 43 .
  • the frequency of the high-frequency signal generated by the low-level high-frequency generator 42 follows the resonance frequency of the fundamental mode.
  • the amplitude of the high-frequency signal is determined by the treatment plan database 60 and instructed by the general control device 40 .
  • a high-frequency signal generated by a device 42 for generating low-level high-frequency waves for harmonic mode is amplified by an amplifier 43 to generate high-frequency power to be input to the high-frequency acceleration cavity 21 .
  • the frequency of the high-frequency signal produced by the low-level high-frequency generator 42 for harmonic mode follows the resonance frequency of the harmonic mode, and the amplitude is determined by the energy of the beam determined by the treatment plan database 60.
  • 45 refers to and the amplitude value determined by the calculation of the voltage amplitude calculator 45 is specified by the overall controller 40 .
  • the configuration and control system for extracting the beam out of the accelerator 1 includes a high-frequency power source 46 for applying a high-frequency voltage to the disturbance electrode 313 and a high-frequency disturbance control device for controlling the high-frequency power source 46, as shown in FIG. 47.
  • the voltage value output from the high-frequency power supply 46 to the disturbance electrode 313 is controlled by the high-frequency disturbance control device 47 .
  • the specified value of the voltage output from the high-frequency power supply 46 is determined by the treatment plan data stored in the treatment plan database 60 as a value uniquely determined from the extraction beam energy and the output current of the extraction beam.
  • the general control device 40 acquires the specified value from the treatment plan data and instructs the disturbance high-frequency control device 47 .
  • FIG. 11 is a timing chart of the operation of each device.
  • FIG. 12 is a flowchart showing the operation flow.
  • the vertical axis of the chart in FIG. 11 represents, from the top, (1) the rotation angle of the rotary shaft 213 of the rotary variable capacitor 212, (2) the resonance frequency of the high frequency acceleration cavity 21, and (3) the high frequency acceleration cavity 21. (4) the amplitude of the high frequency for acceleration in the acceleration gap 223; (5) the current waveform of the beam output by the ion source 12; The disturbance high frequency input to the disturbance electrode 313 and (8) the beam current waveform output from the accelerator 1 are shown.
  • the horizontal axis of the chart shown in FIG. 11 is all time.
  • the resonance frequency of the high-frequency acceleration cavity 21 changes periodically depending on the rotation angle of the rotary shaft 213 of the rotary variable capacitor 212 .
  • the frequency of the high-frequency signal output from the low-level high-frequency generator 42 and input to the high-frequency acceleration cavity 21 also changes synchronously.
  • the period from the time when the resonance frequency reaches its maximum to the next time when it reaches its maximum is defined as the operation period.
  • a beam is output from the ion source 12 immediately after the start of the operation cycle.
  • a beam is accelerated if it is injected into a range where stable synchrotron oscillation is possible.
  • the injection process includes step S11 of starting application of acceleration voltage and step S12 of outputting ions from the ion source.
  • the beam is accelerated as the resonance frequency decreases, and is accelerated to near the predetermined extraction energy.
  • the amplitude of the high frequency input to the high frequency acceleration cavity 21 begins to decrease.
  • the start timing of this decrease is set to start from a predetermined timing before the ion beam reaches the target energy. For example, it is desirable to start the decrease at the timing when the energy expected to reach the target energy is reached before the acceleration electric field generated in the acceleration gap 223 becomes 0 after the input of the high-frequency power is turned off.
  • the acceleration process includes step S13 of accelerating the ion beam and step S14 of stopping the application of the acceleration voltage.
  • the beam when the amplitude of the accelerating electric field becomes sufficiently small, the beam reaches a predetermined extraction energy. When the acceleration is completed, the amount of beam that can be extracted reaches a certain value, and beam extraction becomes possible.
  • the beam circulates to fill the separatrix defined by the additional magnetic field generating shim 311 .
  • a disturbance high frequency is applied by the disturbance electrode 313 .
  • the time for extracting the beam is predetermined.
  • the high-frequency disturbance is applied and the beam continues to be extracted until all the circulating charges are extracted or a predetermined irradiation dose is irradiated.
  • the servomotor 214 associated with the high-frequency acceleration cavity 21 continues to rotate, and the resonance frequency continues to fluctuate.
  • the beam is output again from the ion source, and while the beam is accelerated in the same manner as described above, the extraction of the beam proceeds in parallel.
  • the disturbance high frequency is turned off to suppress the energy fluctuation of the irradiation beam. Since the acceleration high frequency generated by the high frequency acceleration cavity 21 does not match the circulating frequency of the beam during the acceleration process, it hardly affects the beam. Therefore, the beam is circulated with constant energy and is sequentially extracted by the applied disturbing high frequency waves.
  • the irradiation process includes a step S15 for starting application of the extraction high-frequency wave, a step S16 for stopping the application of the extraction high-frequency wave, a step S17 for determining whether the irradiation process is completed, a step S18 for measuring the circulating charge amount, and a next cycle. It includes a step S19 of comparing the amount of charge that can be irradiated with a reference value.
  • step S19 If it is determined in step S19 that the amount of charge that can be irradiated by the next cycle is greater than the reference value (amount of charge>reference value), the process returns to step S15. If it is determined that the charge amount that can be irradiated by the next cycle is equal to or less than the reference value (charge amount ⁇ reference value), the process returns to step S11.
  • the second operation cycle (subsequent beam operation cycle) shown in FIG. 11 shows a timing chart when irradiating different energy from the first operation cycle (preceding beam operation cycle).
  • the operation of the trailing beam differs from the operation of the leading beam in the amplitude value of the accelerating high-frequency wave and its application period. Acceleration to higher energy is achieved by increasing the application time of the high frequency.
  • the amplitude value calculated by the voltage amplitude calculator 45 is determined for each energy in order to suppress the momentum dispersion of the circulating beam after acceleration. This avoids making the high-frequency bucket unnecessarily large, and suppresses the momentum dispersion of the circulating beam. Furthermore, it is possible to increase the beam extraction efficiency and shorten the beam irradiation time.
  • the accelerator 1 is provided with an electrode-type orbiting beam intensity monitor BM (see FIG. 2) as means for monitoring the beam intensity.
  • the beam amount monitor BM is an electrode installed at an arbitrary position on the beam trajectory, and can extract a signal proportional to the voltage and charge amount excited on the electrode. If the amount of charge circulating is greater than the predetermined amount of charge, the injection of ions is skipped.
  • calibration is performed in advance in consideration of the circulating frequency of the beam and the bunch structure of the beam, and a calibration table based on the energy of the beam and the elapsed time from acceleration stop is prepared.
  • FIG. 13 shows a flowchart of processing for measuring the beam amount.
  • the beam amount measurement process includes, for example, a step S20 of acquiring a pick-up signal of the acceleration electrode, a step S21 of analyzing the frequency of the acquired signal, a step S22 of acquiring the signal intensity corresponding to the beam frequency, and frequency characteristics and acceleration stop.
  • a step S23 is included in which the amount of beam is converted with the elapsed time from .
  • the signal of the specific frequency component of the monitor signal is extracted (S21, S22) and converted to the circulating beam amount from the calibration table (S23). Accordingly, it is possible to determine whether or not to skip the injection of new ions based on the circulating charge amount.
  • the high frequency acceleration cavity 21 is not limited to the configuration described above.
  • a modulating mechanism for the high-frequency cavity instead of changing the electrostatic capacity of the rotary variable capacitor 212, the change in magnetic permeability can be used.
  • By placing a ferrite magnetic material inside the cavity it is possible to utilize the change in magnetic permeability caused by an external magnetic field, which is the property of the ferrite magnetic material.
  • FIG. 14 shows a resonance cavity in which one end of the acceleration cavity has a coaxial structure, and a ferrite magnetic body 231 is placed in the gap surrounded by the inner body and the outer conductor in the coaxial structure.
  • a bias current coil 232 is wound around the ferrite magnetic body 231 and connected to an external power source. The current applied to the bias current coil 232 depends on the radio frequency. Since the magnetic permeability of the ferrite magnetic body 231 is determined by the value of the bias current, it is possible to form a table of the relationship between the resonance frequency and the bias current in advance. Therefore, when using this type of acceleration cavity, unlike modulation using a variable capacitor, the high frequency is controlled by controlling the bias current.
  • the accelerator 1 of this embodiment repeatedly executes the injection process and the acceleration process, and maintains a state in which the beam corresponding to the irradiation energy is constantly replenished within the accelerator. Therefore, the accelerator 1 of this embodiment can shorten the time during which the beam cannot be irradiated and improve the efficiency of beam extraction.
  • Example 2 will be explained. In the following examples including this example, differences from the first example will be mainly described. Embodiment 2 is not shown, but can be understood and implemented by those skilled in the art.
  • Example 1 hydrogen ions were used as accelerating nuclides, but in Example 2, carbon ions were used as accelerating nuclides.
  • the accelerator of Example 2 is a frequency-modulated variable energy accelerator capable of extracting carbon ions with a kinetic energy per nucleon in the range of 140 MeV to 430 MeV.
  • Example 2 The operating principle, equipment configuration, and operation procedure of the accelerator of Example 2 are the same as those described in Example 1, so detailed descriptions will be omitted.
  • the difference between the accelerator of Example 2 and the accelerator 1 of Example 1 is the relationship between the size of the orbital radius, the magnetic field and energy, and the relationship between the orbital frequency and energy. They can be determined from the accelerator 1 shown in Example 1 by making the product of the orbital radius and the magnetic field proportional to the ratio of the magnetic stiffness of the beam.
  • the accelerator of the second embodiment also has the same effects as the first embodiment by using the same configuration and method as the accelerator 1 of the first embodiment. That is, the accelerator of Example 2 can suppress the momentum dispersion of the orbiting beam, can improve the extraction efficiency and shorten the irradiation time when used for particle beam therapy, compared to the operation method of the conventional technology.
  • Example 3 will be described with reference to FIG.
  • a third embodiment describes a particle beam therapy system 1000 including the accelerator 1 described in the first embodiment or the accelerator described in the second embodiment.
  • FIG. 15 is an overall configuration diagram of a particle beam therapy system.
  • the particle beam therapy system 1000 sets the energy of proton beams or carbon beams (hereinafter collectively referred to as beams) to an appropriate value depending on the depth from the body surface of the affected area, and treats the patient. It is an irradiation device.
  • the particle beam therapy system 1000 includes an accelerator 1, a beam transport system 2, an irradiation device 3, a treatment table 4, a general control device 40, an irradiation control device 50, a treatment plan database 60, and a treatment planning device 70.
  • Accelerator 1 was described in Example 1 or Example 2.
  • the beam transport system 2 is a mechanism that transports the beam accelerated by the accelerator 1 to the irradiation device 3 .
  • the irradiation device 3 is a device that irradiates a target in the patient 5 fixed on the treatment table 4 with the beam transported by the beam transport system 2 .
  • a general controller 40 controls the accelerator 1 , the beam transport system 2 and the irradiation device 3 .
  • the irradiation controller 50 controls beam irradiation to the target.
  • the treatment plan database 60 stores treatment plans created by the treatment planning device 70 .
  • the treatment planning device 70 creates a beam irradiation plan for the target.
  • the energy and dose of the irradiated particle beam are determined by the treatment plan.
  • the energy and dose of the particle beam determined by the treatment plan are sequentially input from the overall control device 40 to the irradiation control device 50 .
  • the particle beam therapy system 1000 performs a procedure of transferring to the next energy when an appropriate dose is applied, and irradiating the particle beam again.
  • the particle beam therapy system 1000 of the third embodiment configured in this manner, it is possible to utilize the characteristic of the accelerator 1 of the first embodiment or the accelerator of the second embodiment that irradiation can be completed in a short time. , can provide a system with a short irradiation time.
  • the beam transport system 2 of the particle beam therapy system 1000 can also use a rotating gantry instead of a fixed irradiation device.
  • the rotating gantry can rotate around the patient 5 together with the irradiation device 3 to irradiate the beam.
  • a plurality of fixed irradiation devices 3 may be provided.
  • the beam may be directly transported from the accelerator 1 to the irradiation device 3 without providing the beam transport system 2 .
  • each component of the present invention can be selected arbitrarily, and inventions having selected configurations are also included in the present invention.
  • the configurations described in the claims can be combined in addition to the combinations specified in the claims.

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Abstract

Provided are an accelerator which can efficiently generate a beam and a particle beam treatment system comprising the accelerator. The accelerator is a circumference orbital-type accelerator that uses a main magnetic field and a frequency-modulated high-frequency electrical field to accelerate ions supplied from an ion source and generate a beam. The accelerator comprises: an acceleration high frequency application device that applies an acceleration high frequency which can be frequency modulated and which accelerates the ions; an extraction high frequency application device that applies an extraction high frequency which has a different frequency than that of the acceleration high frequency and which is for extracting a beam; a disturbance magnetic field region formation unit that forms a disturbance magnetic field region; and a septum electromagnet for beam extraction. During the beam extraction, new ions are supplied from the ion source and accelerated (fig. 11 (1)-(8)).

Description

加速器および加速器を備える粒子線治療システムParticle beam therapy system with accelerator and accelerator
　本発明は、加速器および加速器を備える粒子線治療システムに関する。 The present invention relates to an accelerator and a particle beam therapy system comprising the accelerator.
　粒子線治療や物理実験などで使用する高エネルギのイオンビームは、加速器を用いて生成される。核子当たりの運動エネルギが２００ＭｅＶ前後のビームを得る加速器には、種類がいくつかある。例えば、サイクロトロンやシンクロトロン、特許文献１に記載されているようなシンクロサイクロトロン、特許文献２に記載されているような可変エネルギ加速器が知られている。サイクロトロンおよびシンクロサイクロトロンの特徴は、静磁場中を周回するビームを高周波電場で加速する点である。サイクロトロンおよびシンクロトロンでは、加速されるにつれてビームはその軌道の曲率半径を増し、外側の軌道に移動し、最高エネルギまで到達した後に取り出される。そのため取り出すビームのエネルギは、基本的には固定される。 High-energy ion beams used in particle beam therapy and physical experiments are generated using accelerators. There are several types of accelerators that obtain beams with a kinetic energy of around 200 MeV per nucleon. For example, a cyclotron, a synchrotron, a synchrocyclotron as described in Patent Document 1, and a variable energy accelerator as described in Patent Document 2 are known. A feature of cyclotrons and synchrocyclotrons is that they accelerate a beam circulating in a static magnetic field with a high-frequency electric field. In cyclotrons and synchrotrons, the beam increases the radius of curvature of its trajectory as it is accelerated, moves to outer trajectories, reaches maximum energy and is then extracted. Therefore, the energy of the extracted beam is basically fixed.
　特許文献１のシンクロサイクロトロンでは、半径Ｒの略円形の断面を有する一対の強磁性体のポールが、中心軸を一致させて、正中面を挟んで上下に配置されている。一対のポールは、ギャップによって離隔され、このギャップは、正中面に対して実質的に対称なプロファイルを有するキャビティを形成している。ギャップの高さは、ポールの半径方向において変化している。ギャップの高さは、中心軸ではＨｃｅｎｔｅｒであり、中心軸から半径Ｒ２までの円形の部分では、半径が大きくなるにつれてＨｃｅｎｔｅｒから徐々に増大し、半径Ｒ２において最大値Ｈｍａｘとなる。半径Ｒ２より大きい環状の部分は、半径が大きくなるにつれて、そのギャップの高さが徐々に減少し、ポールの縁におけるギャップの高さは、Ｈｅｄｇｅである。このようなギャップ形状のキャビティを備えるシンクロサイクロトロンは、ギャップ内の磁場を最小化する一方で、シンクロサイクロトロンのサイズを最小化することができると特許文献１には開示されている。 In the synchrocyclotron of Patent Document 1, a pair of ferromagnetic poles having a substantially circular cross section with a radius R are arranged vertically with the median plane interposed therebetween with their central axes aligned. A pair of poles are separated by a gap that defines a cavity having a substantially symmetrical profile with respect to the median plane. The height of the gap varies in the radial direction of the pole. The height of the gap is Hcenter at the center axis, and in the circular portion from the center axis to the radius R2, the height gradually increases from Hcenter as the radius increases, reaching a maximum value Hmax at the radius R2. The annular portion larger than the radius R2 gradually decreases in gap height as the radius increases, and the gap height at the edge of the pole is Hedge. A synchrocyclotron with such a gap-shaped cavity is disclosed in US Pat. No. 6,300,000 to minimize the size of the synchrocyclotron while minimizing the magnetic field in the gap.
　特許文献２には、小型で、かつ可変エネルギのビームの取出しが可能な加速器として、主磁場、および周波数変調した高周波電場によりビームを加速する周回軌道型加速器であって、周波数変調が可能であり、前記ビームを加速する加速高周波を印加する加速高周波印加装置と、前記加速高周波とは周波数が異なり、ビームを取出すための取出し高周波を印加する取出し高周波印加装置と、２極以上の極数の磁場成分を含み、少なくとも４極磁場成分を含む高次磁場よりなる擾乱磁場領域を形成する擾乱磁場領域形成部と、磁性体のシム、およびセプタムコイルを有するセプタム電磁石と、を備えたことを特徴とする加速器が記載されている。 Patent Document 2 discloses an orbital accelerator that accelerates a beam by a main magnetic field and a frequency-modulated high-frequency electric field as a compact accelerator capable of extracting a beam of variable energy, and is capable of frequency modulation. an acceleration high-frequency applying device for applying an accelerating high-frequency wave for accelerating the beam; an extracting high-frequency applying device for applying an extracting high-frequency wave having a different frequency from the accelerating high-frequency wave for extracting the beam; and a magnetic field having a number of poles of two or more. and a septum electromagnet having a magnetic shim and a septum coil. Accelerators are described.
特表２０１３－５４１１７０号公報Japanese Patent Publication No. 2013-541170 特開２０２０－３８７９７号公報JP 2020-38797 A
　粒子線治療では、治療計画などで予め定められた照射線量の許容範囲を超過することなく、照射対象の腫瘍にビームを照射することが求められる。特許文献１のシンクロサイクロトロンを用いる粒子線治療装置では、シンクロサイクロトロンの一運転周期内で加速し取り出しの可能なビーム量を、照射線量の許容範囲に対して十分小さくする必要が有る。よって、特許文献１では、一運転周期に加速する電荷量が加速器の性能で決まる上限より小さくせざるを得ず、照射完了に時間がかかる。 In particle beam therapy, it is required to irradiate the target tumor with the beam without exceeding the permissible range of irradiation dose that is predetermined in the treatment plan. In the particle beam therapy system using the synchrocyclotron of Patent Document 1, it is necessary to make the amount of beam that can be accelerated and extracted within one operation cycle of the synchrocyclotron sufficiently smaller than the allowable range of irradiation dose. Therefore, in Patent Document 1, the amount of charge accelerated in one operation cycle must be smaller than the upper limit determined by the performance of the accelerator, and it takes time to complete the irradiation.
　特許文献２の可変エネルギ加速器は、取り出しビームのエネルギが可変であるため、治療計画で定められた照射線量に合わせたエネルギのビームを出射できる。よって、可変エネルギ加速器は、シンクロサイクロトロンと比較して、粒子線治療のビーム照射時間を短縮できる。可変エネルギ加速器は、加速器サイズにおいても、サイクロトロンやシンクロサイクロトロンと同等であり、小型である。そのため、可変エネルギ加速器は、粒子線治療装置の加速器として、ビーム照射時間のさらなる短縮が期待されている。しかしながら、特許文献２に記載の加速器の運転方法において、加速器は数ｍｓ程度のサイクルで動作する。このサイクル中にイオン源から加速器にイオンを入射する期間と、イオンを加速する期間と、入射したイオンを全量照射してから再度入射するまでの期間などで、イオンビーム（以下、ビーム）を取り出すことができない。 In the variable energy accelerator of Patent Document 2, the energy of the extraction beam is variable, so it is possible to emit a beam with an energy that matches the irradiation dose determined in the treatment plan. Therefore, the variable energy accelerator can shorten the beam irradiation time of particle beam therapy compared to the synchrocyclotron. The variable energy accelerator is equivalent in accelerator size to cyclotrons and synchrocyclotrons, and is small. Therefore, the variable energy accelerator is expected to further shorten the beam irradiation time as an accelerator of a particle beam therapy system. However, in the accelerator operation method described in Patent Document 2, the accelerator operates in a cycle of about several milliseconds. During this cycle, an ion beam (hereafter referred to as a beam) is extracted during the period during which ions are injected from the ion source into the accelerator, the period during which the ions are accelerated, and the period from when all the injected ions are irradiated until they are injected again. I can't.
　本発明の目的は、効率よくビームを生成することができる加速器および加速器を備える粒子線治療システムを提供することにある。 The purpose of the present invention is to provide an accelerator capable of efficiently generating beams and a particle beam therapy system equipped with the accelerator.
　上記課題を解決すべく、本発明に従う加速器は、主磁場と周波数変調された高周波電場とにより、イオン源から供給されたイオンを加速してビームを生成する周回軌道型加速器であって、周波数変調が可能であり、イオンを加速する加速高周波を印加する加速高周波印加装置と、加速高周波とは異なる周波数であって、ビームを取出すための取出し高周波を印加する取出し高周波印加装置と、擾乱磁場領域を形成する擾乱磁場領域形成部と、ビーム取り出し用のセプタム電磁石と、を備え、ビームの取り出し中において、イオン源から新たなイオンが供給されて加速される。 In order to solve the above problems, an accelerator according to the present invention is an orbital accelerator that accelerates ions supplied from an ion source to generate a beam by means of a main magnetic field and a frequency-modulated high-frequency electric field. An acceleration high-frequency applying device for applying an accelerating high-frequency wave for accelerating ions, an extraction high-frequency applying device for applying a high-frequency wave for extracting a beam at a frequency different from the accelerating high-frequency wave, and a disturbing magnetic field region. A stray magnetic field region forming portion to form and a septum electromagnet for beam extraction are provided, and new ions are supplied from the ion source and accelerated during beam extraction.
　本発明によれば、効率よくビームを生成し、取り出すことができる。 According to the present invention, beams can be efficiently generated and extracted.
実施例１の加速器の全体概形図。1 is an overall schematic diagram of an accelerator of Example 1. FIG. 加速器の内部構造。Internal structure of the accelerator. 周回中のビームエネルギと周回周波数の関係図。FIG. 10 is a diagram showing the relationship between beam energy during circulation and circulation frequency. 設計軌道形状の説明図。Explanatory drawing of a design track|orbit shape. 周回中のビームエネルギと設計軌道上磁場との関係図。FIG. 11 is a diagram showing the relationship between the beam energy during orbit and the design on-orbit magnetic field. ディー電極に励起される高周波モードの概略図。Schematic diagram of high frequency modes excited in the Dee electrode. 高周波バケツの概形図。Schematic diagram of a high frequency bucket. 加速終了直前の位相空間を示す説明図。Explanatory drawing which shows the phase space just before the end of acceleration. 加速終了直後の位相空間を示す説明図。Explanatory drawing which shows the phase space immediately after the completion|finish of acceleration. 加速器の制御ブロック図。Accelerator control block diagram. 加速器の運転のタイミングチャート。Timing chart of accelerator operation. 加速器の制御処理を示すフローチャート。4 is a flowchart showing control processing of an accelerator; ビーム量を測定する処理のフローチャート。4 is a flowchart of processing for measuring beam amount; 実施例３に係り、高周波空胴の構造例。FIG. 10 is a structural example of a high-frequency cavity according to Example 3; FIG. 粒子線治療システムの全体構成図。Overall configuration diagram of a particle beam therapy system.
　以下、図面に基づいて、加速器を説明する。本実施形態では、イオンを入射（イオンの出力）するプロセス、入射されたイオンを加速するプロセス、加速されたイオン（ビーム）を取り出すプロセス、減速プロセスという時間的に直列なプロセスを並列的に実行する。本実施形態では、入射プロセスおよび加速プロセスを繰り返して実行し、照射エネルギに対応するビームが常に加速器内に補充されている状態を維持する。これにより、本実施形態では、入射プロセス、加速プロセスおよび取り出しプロセスを同時並行して実行することができるため、ビームを照射できない時間を短くし、効率を高めることができる。 The accelerator will be explained below based on the drawings. In this embodiment, temporally serial processes of injection of ions (output of ions), acceleration of injected ions, extraction of accelerated ions (beam), and deceleration are executed in parallel. do. In this embodiment, the injection process and the acceleration process are repeatedly performed to maintain a state in which the beam corresponding to the irradiation energy is constantly replenished in the accelerator. As a result, in this embodiment, the injection process, the acceleration process, and the extraction process can be executed in parallel, so that the time during which the beam cannot be irradiated can be shortened and the efficiency can be improved.
　さらに、本実施形態で述べる加速器を備える粒子線治療システムでは、加速器の制御の面で照射不可能な時間を削減することができ、ビームを照射可能な時間的割合を増加させて、治療時間を短縮することができる。 Furthermore, in the particle beam therapy system equipped with the accelerator described in this embodiment, it is possible to reduce the time during which irradiation is not possible in terms of accelerator control, increase the proportion of time during which beam irradiation is possible, and increase the treatment time. can be shortened.
　本実施形態に係る加速器１は、図１～図１３で後述するように、イオンを加速する加速用電場を形成する高周波加速空胴２１と、加速用電場の周波数を変調するための回転式可変容量キャパシタ２１２と、磁極１２３が形成する磁場により周回するイオンに対して安定領域からのキック作用を与える付加磁場発生用シム３１１と、付加磁場発生用シム３１１によってキック作用が与えられたイオンを加速器１から取り出すための擾乱用電場を発生させる擾乱用電極３１３と、加速用電場を制御する低レベル高周波発生装置４２と、擾乱用電場を制御する擾乱高周波制御装置４７と、を備え、異なるエネルギのイオンがそれぞれ周回する環状の複数のイオンの周回軌道が集約する領域と離散する領域を有しており、異なるサイクルで入射されたイオンが同時に略同一のエネルギで周回させる。 1 to 13, the accelerator 1 according to the present embodiment includes a high-frequency acceleration cavity 21 that forms an acceleration electric field for accelerating ions, and a rotary variable cavity for modulating the frequency of the acceleration electric field. An additional magnetic field generating shim 311 that gives a kick action from the stable region to the ions orbiting by the magnetic field formed by the capacitance capacitor 212 and the magnetic pole 123, and the ions given the kick action by the additional magnetic field generating shim 311 are transferred to the accelerator. 1, a low-level high-frequency generator 42 for controlling the accelerating electric field, and a high-frequency disturbance control device 47 for controlling the electric field for disturbance. A plurality of annular circulating trajectories of ions, each circulating, has a converging region and a discrete region, and ions injected in different cycles circulate at the same time with approximately the same energy.
　図１～図１３を用いて第１実施例を説明する。本実施例の加速器１は、周波数変調型の可変エネルギ加速器である。この加速器は時間的に一定な磁場を主磁場として持ち、主磁場中を周回する陽子を高周波電場によって加速する円形加速器である。その外観を図１に示す。 A first embodiment will be described with reference to FIGS. 1 to 13. FIG. The accelerator 1 of this embodiment is a frequency modulated variable energy accelerator. This accelerator has a temporally constant magnetic field as its main magnetic field, and is a circular accelerator that accelerates protons orbiting in the main magnetic field by a high-frequency electric field. Its appearance is shown in FIG.
　図１に示すように、加速器１は、上下に分割可能な電磁石１１によって、加速・周回中のビームが通過する領域（以下、ビーム通過領域２０（図２参照）と呼ぶ）内に主磁場を励起する。電磁石１１は「一対の磁石」の例である。電磁石１１の内側は、図示を省略した真空ポンプによって真空引きされている。 As shown in FIG. 1, the accelerator 1 uses electromagnets 11 that can be divided vertically to generate a main magnetic field in a region through which the beam passes during acceleration and circling (hereinafter referred to as a beam passage region 20 (see FIG. 2)). Excite. Electromagnet 11 is an example of a "pair of magnets." The inside of the electromagnet 11 is evacuated by a vacuum pump (not shown).
　電磁石１１には、外部とビーム通過領域２０とを接続するための貫通口が複数設けられている。例えば、加速されたビームを取り出す取り出しビーム用貫通口１１１、電磁石１１内に配置されたコイル導体を外部に引き出すための引き出し用の貫通口１１２，１１３、高周波電力入力用貫通口１１４等の、各種貫通口が電磁石１１の上下の分割接続面の面上に設けられている。 The electromagnet 11 is provided with a plurality of through holes for connecting the outside and the beam passage area 20 . For example, through-hole 111 for extraction beam for taking out the accelerated beam, through- holes 112 and 113 for drawing out the coil conductor arranged in electromagnet 11 to the outside, through-hole 114 for high-frequency power input, etc. Through holes are provided on the upper and lower split connection surfaces of the electromagnet 11 .
　高周波電力入力用貫通口１１４を通じて、イオンを加速してイオンビームとするための加速用電場を形成する高周波加速空胴（加速電極）２１が設置されている。「加速高周波印加装置」の例である高周波加速空胴２１には、後述のように、加速用のディー電極２２１（図２参照）と、加速用電場の周波数を変調するための回転式可変容量キャパシタ（変調部）２１２とが設置されている。 A high-frequency acceleration cavity (acceleration electrode) 21 is installed through the high-frequency power input through-hole 114 to form an acceleration electric field for accelerating ions into an ion beam. As will be described later, the high-frequency acceleration cavity 21, which is an example of the "high-frequency acceleration applying device", includes a dee electrode 221 for acceleration (see FIG. 2) and a rotary variable capacitor for modulating the frequency of the electric field for acceleration. A capacitor (modulation unit) 212 is installed.
　電磁石１１の上部の中心からずれた位置に、水素イオンを供給するためのイオン源１２が設置されている。イオン源１２は、ビーム入射用貫通口１１５および入射部１３０（図２参照）を通して、イオンを加速器１内部の電磁石１１間に入射する。入射部１３０には、貫通口１１５を通じて、外部からビーム通過領域２０へイオンを入射するのに必要な電力が供給されている。 An ion source 12 for supplying hydrogen ions is installed at a position shifted from the center of the upper part of the electromagnet 11 . The ion source 12 injects ions between the electromagnets 11 inside the accelerator 1 through the beam injection through-hole 115 and the injection section 130 (see FIG. 2). Electric power necessary for injecting ions into the beam passing region 20 is supplied from the outside to the injection section 130 through the through hole 115 .
　加速器１の内部構造について図１および図２を用いて説明する。図２は、電磁石１１を上下に分割した面を上から見たときの機器配置を示す図である。 The internal structure of the accelerator 1 will be explained using FIGS. 1 and 2. FIG. 2 is a diagram showing the arrangement of equipment when a plane obtained by dividing the electromagnet 11 into upper and lower parts is viewed from above.
　図１に示すように、電磁石１１の上下部それぞれは、円筒状のリターンヨーク１２１および天板１２２を有しており、その内部側には、図２に示すように、円柱状の磁極１２３を有している。上下対向した磁極１２３によって挟まれる円筒状の空間内に、上述のビーム通過領域２０がある。この上下の磁極１２３が互いに対向している面を磁極面と定義する。また磁極面に挟まれた磁極面に平行かつ上下の磁極面から互いに等距離にある面を軌道面と呼ぶ。 As shown in FIG. 1, the upper and lower portions of the electromagnet 11 each have a cylindrical return yoke 121 and a top plate 122, and a cylindrical magnetic pole 123 is provided inside them, as shown in FIG. have. The beam passing region 20 described above is present in the cylindrical space sandwiched by the magnetic poles 123 facing each other vertically. A surface where the upper and lower magnetic poles 123 face each other is defined as a magnetic pole surface. A plane sandwiched between magnetic pole faces and parallel to the magnetic pole face and equidistant from the upper and lower magnetic pole faces is called a track surface.
　磁極１２３とリターンヨーク１２１の間に形成される凹部には、円環状のコイル１３が磁極１２３の外周側の壁に沿って設置されている。コイル１３に電流を流すことによって上下対向する磁極１２３が磁化し、ビーム通過領域２０に後述する所定の分布で磁場が励起される。 In the recess formed between the magnetic pole 123 and the return yoke 121, the annular coil 13 is installed along the wall on the outer peripheral side of the magnetic pole 123. When a current is passed through the coil 13 , the magnetic poles 123 facing up and down are magnetized, and a magnetic field is excited in the beam passing region 20 with a predetermined distribution, which will be described later.
　高周波加速空胴２１は、λ／４型の共振モードによって加速ギャップ２２３にイオンを加速するための加速用高周波電場を励起させる。高周波加速空胴２１のうち、加速器１に対して固定的に設置された部分をディー電極２２１と定義する。高周波加速空胴２１は、貫通口１１４を通じて、ビーム通過領域２０の一部領域を囲むディー電極２２１を形成する。イオンは、ディー電極２２１とこのディー電極２２１に対向するように配置される接地電極２２２とによって挟まれる領域である加速ギャップ２２３により励起される高周波電場によって加速される。前述のビームの周回周波数に同期するために、高周波電場の周波数は、ビームの周回周波数の整数倍であることが必要である。加速器１では、高周波電場の周波数はビームの周回周波数の１倍としている。 The high frequency acceleration cavity 21 excites an acceleration high frequency electric field for accelerating ions into the acceleration gap 223 by a λ/4 type resonance mode. A portion of the high-frequency acceleration cavity 21 that is fixedly installed with respect to the accelerator 1 is defined as a Dee electrode 221 . The high frequency acceleration cavity 21 forms a dee electrode 221 surrounding a partial area of the beam passage area 20 through the through hole 114 . Ions are accelerated by a high-frequency electric field excited by an acceleration gap 223 which is a region sandwiched between a Dee electrode 221 and a ground electrode 222 arranged to face the Dee electrode 221 . In order to synchronize with the aforementioned beam's circling frequency, the frequency of the high-frequency electric field needs to be an integer multiple of the beam's circulating frequency. In the accelerator 1, the frequency of the high-frequency electric field is one times the circulating frequency of the beam.
　磁極１２３には、磁場の微調整用のトリムコイル３３が複数系統設けられている。トリムコイル３３は、貫通口１１２，１１３を通じて外部電源に接続されている。各系統別に励磁電流を調整することで、後述の主磁場分布に近づけ、安定なベータトロン振動を実現するように、運転前にトリムコイル電流が調整される。 The magnetic pole 123 is provided with a plurality of systems of trim coils 33 for fine adjustment of the magnetic field. The trim coil 33 is connected to an external power source through through holes 112 and 113 . By adjusting the excitation current for each system, the trim coil current is adjusted before operation so as to approximate the distribution of the main magnetic field described later and realize stable betatron oscillation.
　上述の加速器１では、イオン源１２で生成されたイオンは、入射部１３０の引き出し電極に印加された電圧によって、低エネルギのイオンの状態でビーム通過領域２０に引き出される。入射されたイオンは、高周波加速空胴２１によって励起される高周波電場によって、加速ギャップ２２３を通過する毎に加速され、イオンビームとなる。 In the accelerator 1 described above, the ions generated by the ion source 12 are extracted to the beam passage region 20 in the state of low-energy ions by the voltage applied to the extraction electrode of the injection section 130 . The injected ions are accelerated by the high-frequency electric field excited by the high-frequency acceleration cavity 21 each time they pass through the acceleration gap 223 to form an ion beam.
　図２に示すように、ビームを加速器１の外部へ取り出すために、四極磁場や六極以上の多極磁場を励磁する二か所の付加磁場発生用シム（キック部）３１１と高周波電場を印加する擾乱用電極（擾乱部）３１３とが、磁極面の一部に電気的に絶縁された状態で設置されている。磁極面の端部の一か所に取り出し用セプタム電磁石３１２の入射部が設置されている。 As shown in FIG. 2, in order to extract the beam from the accelerator 1, two additional magnetic field generating shims (kick portions) 311 for exciting a quadrupole magnetic field or a multipolar magnetic field of six or more poles and a high-frequency electric field are applied. A disturbance electrode (disturbance portion) 313 is provided in an electrically insulated state on a part of the magnetic pole face. An incident part of the extraction septum electromagnet 312 is installed at one of the ends of the magnetic pole face.
　擾乱用電極３１３は、微小な振幅の高周波（ＲＦ）電場を印加することが可能であり、周回中の粒子を軌道面内方向にキックし、設計軌道から粒子を外れさせる。その軌道が設計軌道から外れた粒子は、付加磁場発生用シム３１１の近くを通過する。 The disturbing electrode 313 is capable of applying a radio frequency (RF) electric field of minute amplitude, which kicks orbiting particles in the direction of the trajectory plane, causing the particles to deviate from the designed trajectory. Particles whose trajectories deviate from the designed trajectory pass near the additional magnetic field generating shim 311 .
　付加磁場発生用シム３１１による磁場は、ビーム通過領域２０中を周回するイオンビームに対して安定領域を制限し、安定領域外に出た粒子を取り出し用セプタム電磁石３１２へ導入する。一対の付加磁場発生用シム３１１は、それぞれ逆極性の磁場を磁極１２３が形成する主磁場に対して重畳励磁する。 The magnetic field generated by the additional magnetic field generating shim 311 restricts the stable region of the ion beam circulating in the beam passing region 20, and introduces the particles outside the stable region to the extraction septum electromagnet 312. The pair of additional magnetic field generating shims 311 superimpose and excite magnetic fields of opposite polarities on the main magnetic field formed by the magnetic poles 123 .
　擾乱用電極３１３に適当な周波数の高周波電圧を印加することでビームに擾乱を与えると、後に述べる原理により、擾乱用電極３１３に印加されるＲＦ電場のオン／オフに同期して、ビームのオン／オフ制御が可能となる。これら付加磁場発生用シム３１１および擾乱用電極３１３の詳細は後述する。 When the beam is disturbed by applying a high-frequency voltage of an appropriate frequency to the disturbing electrode 313, the beam is turned on/off in synchronization with the on/off of the RF electric field applied to the disturbing electrode 313 according to the principle described later. /OFF control becomes possible. Details of the additional magnetic field generating shim 311 and the disturbance electrode 313 will be described later.
　軌道面において主磁場の面内成分がほぼ０となるように、上下の磁極１２３、コイル１３、トリムコイル３３、付加磁場発生用シム３１１、取り出し用セプタム電磁石３１２、擾乱用電極３１３の形状と配置が設計されており、軌道面に対して面対称の配置および電流分布となっている。磁極１２３、ディー電極２２１、コイル１３、トリムコイル３３、擾乱用電極３１３の形状は、図２に示すように、加速器１を上面側から見たときに、貫通口１１４の中心部と貫通口１１２の中心部とを結ぶ線分に対して、左右対称の形状となっている。 The upper and lower magnetic poles 123, the coil 13, the trim coil 33, the additional magnetic field generating shim 311, the extraction septum electromagnet 312, and the disturbance electrode 313 are shaped and arranged so that the in-plane component of the main magnetic field is approximately 0 on the orbital plane. is designed, and has a symmetrical arrangement and current distribution with respect to the orbital plane. The magnetic pole 123, the dee electrode 221, the coil 13, the trim coil 33, and the disturbance electrode 313 are shaped so that, as shown in FIG. The shape is symmetrical with respect to the line segment connecting the center of the
　加速器１内を周回するビームの軌道および運動について述べる。ビームは、ビーム通過領域２０中を周回しながら加速される。加速器１から取り出し可能なビームの運動エネルギは、最小７０ＭｅＶ、最大２３５ＭｅＶである。運動エネルギが大きいほどビームの周回周波数は小さくなる。入射直後の運動エネルギのビームは７６ＭＨｚで、運動エネルギ２３５ＭｅＶに達したビームは５９ＭＨｚで、ビーム通過領域２０中を周回する。これらのエネルギと周回周波数の関係は図３のようになる。図３の縦軸は周回周波数を示し、図３の横軸は運動エネルギを示す。 The trajectory and motion of the beam orbiting inside the accelerator 1 will be described. The beam is accelerated while circulating in the beam passing area 20 . The kinetic energy of the beam that can be extracted from the accelerator 1 is 70 MeV minimum and 235 MeV maximum. The higher the kinetic energy, the lower the circulating frequency of the beam. The beam of kinetic energy immediately after incidence circulates in the beam passing region 20 at 76 MHz, and the beam reaching kinetic energy of 235 MeV at 59 MHz. The relationship between these energies and the circulating frequency is as shown in FIG. The vertical axis in FIG. 3 indicates the lap frequency, and the horizontal axis in FIG. 3 indicates the kinetic energy.
　図５に示すように、形成される磁場は、ビームの軌道に沿って一様、かつエネルギが高くなるにつれ磁場が低下していくような分布を作る。つまり、径方向外側の磁場が低下するような磁場を形成する。このような磁場下においては、ビームの軌道面内の動径方向と軌道面とに対して垂直な方向のそれぞれに対して安定にベータトロン振動する。 As shown in Fig. 5, the formed magnetic field creates a distribution that is uniform along the trajectory of the beam and that the magnetic field decreases as the energy increases. That is, a magnetic field is formed such that the magnetic field on the radially outer side is reduced. Under such a magnetic field, the betatron oscillates stably in each of the radial direction in the orbital plane of the beam and the direction perpendicular to the orbital plane.
　図４に各エネルギの軌道を示す。図４には複数の周回軌道が示されている。図４では、最も外側に最大エネルギ２５２ＭｅＶの軌道に対応した半径０．４９７ｍの円軌道が存在し、そこから、エネルギ０ＭｅＶまで磁気剛性率で５１分割した計５１本の円軌道が示されている。点線は、各軌道の同一の周回位相を結んだ線であり、この線を等周回位相線と呼ぶ。 　Figure 4 shows the trajectory of each energy. A plurality of orbits are shown in FIG. In FIG. 4, there is a circular orbit with a radius of 0.497 m corresponding to the orbit with the maximum energy of 252 MeV on the outermost side, and from there, a total of 51 circular orbits are shown, which are divided into 51 by the magnetic rigidity up to the energy of 0 MeV. . A dotted line is a line connecting the same orbital phases of each orbit, and this line is called an isometric phase line.
　図４に示すように、加速器１では、ビームの加速に従って、ビームの軌道中心（設計軌道）が軌道面内で一方向に移動する。設計軌道が移動する結果、異なる運動エネルギの軌道が互いに近接している箇所（周回軌道が集約する領域）と、互いに遠隔している領域（周回軌道が離散する領域）とが存在する。つまりビームの設計軌道が偏心している。 As shown in FIG. 4, in the accelerator 1, the beam trajectory center (design trajectory) moves in one direction within the trajectory plane as the beam is accelerated. As a result of the movement of the design trajectory, there are places where trajectories with different kinetic energies are close to each other (regions where the loop trajectories converge) and regions where they are far from each other (regions where the loop trajectories are discrete). That is, the design trajectory of the beam is eccentric.
　最も設計軌道同士が近接している設計軌道の各点を結ぶと、すべての設計軌道に直交する線分となる。最も設計軌道同士が遠隔している設計軌道の各点を結ぶと、すべての設計軌道に直交する線分となる。これら二つの線分は、同一直線上に存在する。この直線を対称軸と定義すると、設計軌道の形状は対称軸を通り、軌道面に垂直な面に対して面対称となる。 Connecting the points of the design trajectories where the design trajectories are closest to each other results in a line segment orthogonal to all the design trajectories. A line segment orthogonal to all the design trajectories is obtained by connecting points of the design trajectories that are farthest apart from each other. These two line segments are on the same straight line. If this straight line is defined as the axis of symmetry, the shape of the design raceway passes through the axis of symmetry and is symmetrical with respect to a plane perpendicular to the raceway surface.
　図４に示す等周回位相線は、集約領域から周回位相π／２０ごとにプロットされている。ディー電極２２１とディー電極２２１に対向する接地電極２２２との間に形成される加速ギャップ２２３は、集約点から見て±９０度周回した等周回位相線に沿って、設置されている。 The isochronous phase lines shown in FIG. 4 are plotted every circulating phase π/20 from the aggregated region. An acceleration gap 223 formed between the Dee electrode 221 and the ground electrode 222 facing the Dee electrode 221 is set along an equicircular phase line that rotates ±90 degrees when viewed from the consolidation point.
　上記のような軌道構成と軌道周辺での安定な振動とを生じさせるために、加速器１では、設計軌道の偏向半径方向外側に行くにつれて、磁場の大きさが小さくなる主磁場分布としている。設計軌道に沿って磁場は、一定とする。よって、設計軌道は円形となり、ビームエネルギが高まるにつれて、その軌道半径・周回時間は増大する。 In order to generate the above-described orbit configuration and stable oscillation around the orbit, the accelerator 1 has a main magnetic field distribution in which the magnitude of the magnetic field decreases toward the outside in the deflection radial direction of the design orbit. The magnetic field is assumed constant along the design trajectory. Therefore, the designed trajectory is circular, and as the beam energy increases, the trajectory radius and lap time increase.
　このような体系では、設計軌道から半径方向へ微小にずれた粒子は、設計軌道に戻すような復元力を受けると同時に、軌道面に対して鉛直な方向にずれた粒子も軌道面に戻す方向へ主磁場から復元力を受ける。すなわち、ビームのエネルギに対して適切に磁場を小さくしていけば、設計軌道からずれた粒子には、設計軌道に戻そうとする向きに常に復元力が働き、設計軌道の近傍を振動することになる。これにより、安定にビームを周回させ加速させることが可能である。この設計軌道を中心とする振動をベータトロン振動と呼ぶ。各エネルギのビームにおける磁場の値を図５に示した。磁場は、入射部１３０で最大の５Ｔとなり、最外周では４．９１Ｔまで低下する。 In such a system, particles slightly deviated from the design trajectory in the radial direction receive a restoring force that returns them to the design trajectory, and at the same time, particles that deviate in the direction perpendicular to the orbital plane are also returned to the orbital plane. receives a restoring force from the main magnetic field. In other words, if the magnetic field is appropriately reduced with respect to the energy of the beam, the particles deviated from the designed trajectory will always have a restoring force acting in the direction of returning them to the designed trajectory, and will vibrate in the vicinity of the designed trajectory. become. This makes it possible to stably circulate and accelerate the beam. Oscillations centered on this design orbit are called betatron oscillations. FIG. 5 shows the value of the magnetic field in the beam of each energy. The magnetic field reaches a maximum of 5 T at the incident portion 130 and decreases to 4.91 T at the outermost circumference.
　上述の主磁場分布は、コイル１３とそれを補助するトリムコイル３３とに所定の励磁電流を流して、磁極１２３が磁化されることにより、励起される。イオンの入射部１３０で磁場を大きくし、外周に向かって磁場を小さくする分布を形成するために、磁極１２３が対向する距離（ギャップ）は入射部１３０において最も小さく、外周に向かって大きくなる形状となる。さらに、磁極１２３の形状は、ギャップ中心を通る平面（軌道面）に対して面対称の形状であり、軌道面上では軌道面に垂直な方向の磁場成分のみを持つ。さらに、磁場分布の微調整を、磁極面に設置されたトリムコイル３３に印加する電流を調整することで行い、所定の磁場分布を励起させる。 The main magnetic field distribution described above is excited by magnetizing the magnetic pole 123 by passing a predetermined excitation current through the coil 13 and the trim coil 33 that assists it. In order to form a distribution in which the magnetic field is increased at the ion injection part 130 and decreased toward the outer periphery, the distance (gap) between the magnetic poles 123 facing each other is the smallest at the injection part 130 and increases toward the outer periphery. becomes. Furthermore, the shape of the magnetic pole 123 is symmetrical with respect to a plane (orbital plane) passing through the center of the gap, and has only a magnetic field component in a direction perpendicular to the orbital plane on the orbital plane. Further, fine adjustment of the magnetic field distribution is performed by adjusting the current applied to the trim coils 33 installed on the magnetic pole faces to excite a predetermined magnetic field distribution.
　上述のように、高周波加速空胴２１は、加速ギャップ２２３に電場を励起させる。そのために、外部高周波電源（図１０の低レベル高周波発生装置４２およびアンプ４３を参照）から入力カプラ２１１を通じて高周波電力が導入され、ディー電極２２１と接地電極２２２の間の加速ギャップ２２３に高周波電場が励起される。 As described above, the high frequency acceleration cavity 21 excites an electric field in the acceleration gap 223 . For this purpose, high-frequency power is introduced from an external high-frequency power supply (see low-level high-frequency generator 42 and amplifier 43 in FIG. 10) through input coupler 211, and a high-frequency electric field is generated in acceleration gap 223 between dee electrode 221 and ground electrode 222. Excited.
　一般に、ディー電極２２１が励起する電磁場は、電極形状によって定まる特定の共振周波数および空間分布の電磁場となる。特定の周波数と空間分布を持つ電磁場を固有モードと称する。固有モードには複数種類あり、加速のために励起するモードを基本モードと称する。基本モードの電磁場分布と表面電流分布を図６に示す。図６には、共振器の外形、太矢印にて電場の分布（Ｅ）、点線矢印で磁場の分布（Ｂ）、実線矢印で共振器表面の電流分布（ｊ）の概形を示している。基本モードではギャップのいたるところで、ディー電極２２１から設置電極２２２に対して同じ向きの電場が生じる。 In general, the electromagnetic field excited by the Dee electrode 221 is an electromagnetic field with a specific resonance frequency and spatial distribution determined by the shape of the electrode. An electromagnetic field with a specific frequency and spatial distribution is called an eigenmode. There are multiple types of eigenmodes, and the mode excited for acceleration is called the fundamental mode. FIG. 6 shows the fundamental mode electromagnetic field distribution and surface current distribution. In FIG. 6, the external shape of the resonator, the distribution of the electric field (E) by the thick arrow, the distribution of the magnetic field (B) by the dotted arrow, and the outline of the current distribution (j) on the surface of the resonator by the solid arrow. . In the fundamental mode, an electric field is generated in the same direction from the dee electrode 221 to the ground electrode 222 everywhere in the gap.
　加速器１は、ビームの周回に同期して高周波電場を励起するために、電場の周波数を周回中のビームのエネルギに対応して変調させる。本実施例の共振モードを用いた高周波加速空胴２１では、共振の幅よりも広い範囲で、高周波の周波数を掃引する必要がある。そのために、高周波加速空胴２１の共振周波数も変更する必要が有る。その制御は、高周波加速空胴２１の端部に設置された回転式可変容量キャパシタ２１２の静電容量を変化させることで実施する。回転式可変容量キャパシタ２１２は、回転軸２１３に直接接続された導体板と外部導体（いずれも図示せず）との間に生じる静電容量を、回転軸２１３の回転角によって制御する。すなわち、ビームの加速に伴って、回転軸２１３の回転角を変化させる。 The accelerator 1 modulates the frequency of the electric field corresponding to the energy of the orbiting beam in order to excite a high-frequency electric field in synchronization with the orbiting of the beam. In the high-frequency acceleration cavity 21 using the resonance mode of this embodiment, it is necessary to sweep the high-frequency frequency over a range wider than the resonance width. Therefore, it is necessary to change the resonance frequency of the high-frequency acceleration cavity 21 as well. The control is performed by changing the capacitance of a rotary variable capacitor 212 installed at the end of the high frequency acceleration cavity 21 . The rotary variable capacitor 212 controls the electrostatic capacitance generated between the conductor plate directly connected to the rotary shaft 213 and the external conductor (both not shown) by the rotation angle of the rotary shaft 213 . That is, the rotation angle of the rotating shaft 213 is changed as the beam is accelerated.
　加速器１のビーム入射から取り出しまでのビームの挙動を述べる。まずイオン源１２から低エネルギのイオンが出力され、ビーム入射用貫通口１１５および入射部１３０を介してビーム通過領域２０へ低エネルギのイオンビームが導かれる。 　The behavior of the beam from the beam injection to the extraction of the accelerator 1 is described. First, low-energy ions are output from the ion source 12 and guided to the beam passing region 20 via the beam-incident through-hole 115 and the incident portion 130 .
　ビーム通過領域２０に入射されたビームは、高周波電場による加速を受けながら、そのエネルギが増大するとともに、軌道の回転半径を増加させていく。その後ビームは、高周波電場による進行方向安定性を確保しながら加速される。 The beam incident on the beam passage area 20 increases its energy and increases the radius of rotation of the trajectory while being accelerated by the high-frequency electric field. The beam is then accelerated while ensuring directional stability due to the high-frequency electric field.
　ビームの重心は、高周波電場が最大となる時刻に加速ギャップ２２３を通過するのではなく、時間的に高周波電場が減少しているときに加速ギャップ２２３を通過する。高周波電場の周波数とビームの周回周波数とはちょうど整数倍の比で同期させているため、所定の加速電場の位相で加速された粒子は、次のターンもほぼ同じ位相で加速を受ける。一方、加速位相より早い位相で加速された粒子は、加速位相で加速された粒子よりもその加速量が大きいため、次のターンでは遅れた位相で加速を受ける。逆に有るときに加速位相より遅い位相で加速された粒子は、加速位相で加速された粒子よりもその加速量が小さいため、次のターンでは進んだ位相で加速を受ける。 The center of gravity of the beam does not pass through the acceleration gap 223 at the time when the high-frequency electric field is maximum, but passes through the acceleration gap 223 when the high-frequency electric field decreases over time. Since the frequency of the high-frequency electric field and the circulating frequency of the beam are synchronized at a ratio of just an integral multiple, the particles accelerated by a given phase of the accelerating electric field are accelerated in the next turn with substantially the same phase. On the other hand, particles accelerated in a phase earlier than the acceleration phase are accelerated in a phase delayed in the next turn because the amount of acceleration is greater than that of particles accelerated in the acceleration phase. Conversely, particles accelerated in a phase later than the acceleration phase when present are accelerated in a phase advanced in the next turn because the amount of acceleration is smaller than that of particles accelerated in the acceleration phase.
　このように、所定の加速位相からずれたタイミングの粒子は、加速位相に戻る方向に動き、この作用によって、運動量と位相からなる位相平面（進行方向）内においても安定に振動することができる。この振動をシンクロトロン振動と呼ぶ。すなわち、加速中の粒子はシンクロトロン振動をしながら、徐々に加速され、取り出しされる所定のエネルギまで達する。安定なシンクトロン振動をする間、個々の粒子は、位相平面上に高周波バケツと呼ばれる安定領域内で回転運動をする。 In this way, particles whose timing deviates from the predetermined acceleration phase move in the direction of returning to the acceleration phase, and due to this action, they can oscillate stably even within the phase plane (advancing direction) consisting of momentum and phase. This oscillation is called synchrotron oscillation. That is, the accelerating particles are gradually accelerated while undergoing synchrotron oscillation and reach a predetermined energy to be taken out. During stable synchrotron oscillation, individual particles rotate on the phase plane within a stable region called a high-frequency bucket.
　図７に位相平面上の高周波バケツＢｕの形状とその内部を動く粒子の軌跡との模式図を示す。この高周波バケツＢｕの運動両方向の幅は加速空胴に印加する電圧振幅の平方根に比例すること、および、高周波バケツＢｕの面積が単位時間当たりのビームのエネルギ増加（加速速度）に対して単調現象であることは、それぞれ知られている。 Fig. 7 shows a schematic diagram of the shape of the high-frequency bucket Bu on the phase plane and the trajectory of the particles moving inside it. The width of the high-frequency bucket Bu in both directions of motion is proportional to the square root of the voltage amplitude applied to the acceleration cavity, and the area of the high-frequency bucket Bu is monotonic with respect to the beam energy increase (acceleration speed) per unit time. It is known that each
　回転式可変容量キャパシタ２１２の回転速度によって決まる運転周期下では、加速速度は自然と決まる。したがって、ある電圧振幅以下では高周波バケツＢｕの面積が０となり、安定なシンクロトロン振動を実現できない。高周波バケツＢｕの面積が初めて０を超える電圧振幅を臨界電圧Ｖｃと呼ぶことにすると Under the operating cycle determined by the rotation speed of the rotary variable capacitor 212, the acceleration speed is naturally determined. Therefore, below a certain voltage amplitude, the area of the high-frequency bucket Bu becomes 0, and stable synchrotron oscillation cannot be realized. If the voltage amplitude when the area of the high-frequency bucket Bu exceeds 0 for the first time is called the critical voltage Vc
　臨界電圧Ｖｃは、加速中のビームエネルギに対して単調増加となる。逆に一定の電圧振幅になるように高周波加速空胴２１に対して高周波電力を入力したとき、ビームの加速に伴い、高周波バケツＢｕの面積は徐々に小さくなる。高周波バケツＢｕの面積が徐々に小さくなる状況下においては加速中のビームの運動量分散も小さくなる。 The critical voltage Vc monotonically increases with the beam energy during acceleration. Conversely, when high-frequency power is input to the high-frequency acceleration cavity 21 so as to provide a constant voltage amplitude, the area of the high-frequency bucket Bu gradually decreases as the beam is accelerated. Under the condition that the area of the high-frequency bucket Bu gradually decreases, the momentum dispersion of the beam during acceleration also decreases.
　所定の取り出しビームを目標のエネルギで取り出すために、高周波加速空胴２１に印加されている高周波電場が徐々に低くなり目標エネルギに達したところで、高周波電場の振幅が０となるように、制御装置４０は外部高周波電源からの出力を制御する。これにより、ビームは、目標エネルギにて安定に周回する。そして、擾乱用電極３１３に高周波が印加される。 In order to extract a predetermined extraction beam with a target energy, the high frequency electric field applied to the high frequency acceleration cavity 21 is gradually lowered, and when the target energy is reached, the amplitude of the high frequency electric field becomes zero. 40 controls the output from the external high frequency power supply. This allows the beam to circulate stably at the target energy. A high frequency is applied to the disturbance electrode 313 .
　その高周波の周波数は、ビームのベータトロン振動の周波数に一致している。ビームは、その進行方向の位置、すなわち擾乱用電極３１３を通過する時刻に依存する擾乱を受ける。特定の粒子に着目すると、擾乱用電場と周回のベータトロン振動の周波数とが一致しているため、両者は共鳴し、ある粒子のベータトロン振動振幅が増大する。ベータトロン振動振幅が増大し続けると、設計軌道の外側に設置された付加磁場発生用シム３１１が励起するキック磁場の作用を受けて、急激にベータトロン振動が発散し、設計軌道から見て外側にビームが変位する。その結果、ビームは、取り出し用セプタム電磁石３１２に導入される。この安定領域と不安定領域との境界を、セパラトリクスと称する。 The frequency of the high frequency matches the frequency of the betatron oscillation of the beam. The beam is disturbed depending on its position in the direction of travel, ie the time of passage through the disturbing electrode 313 . Focusing on a specific particle, since the frequency of the perturbing electric field and the orbiting betatron oscillation are the same, they resonate and the betatron oscillation amplitude of a certain particle increases. When the betatron oscillation amplitude continues to increase, the kick magnetic field excited by the additional magnetic field generating shim 311 installed outside the design orbit causes the betatron oscillation to diverge abruptly. beam is displaced to As a result, the beam is introduced into the extraction septum magnet 312 . The boundary between this stable region and unstable region is called a separatrix.
　上記目標エネルギに達してから取り出されるまでの間、ビームを構成する個々の粒子は、付加磁場発生用シム３１１由来の四極磁場と六極以上の多極磁場とによって、ビームの水平方向の位置と傾きで定まる位相空間上において、安定に周回できる領域と不安定に軌道ずれが増大し続ける領域とに分けられた状態で、周回する。 From the time the target energy is reached until the beam is extracted, the individual particles that make up the beam are positioned in the horizontal direction of the beam by the quadrupolar magnetic field derived from the additional magnetic field generating shim 311 and the multipolar magnetic field of six or more poles. In the phase space determined by the inclination, the orbit is divided into a stable orbital area and an unstable orbital deviation increasing area.
　セパラトリクスの内側に存在する粒子は、安定にベータトロン振動を続ける。セパラトリクスの外にいる粒子は、付加磁場発生用シム３１１によるキック作用が周回ごとに蓄積されるため、設計軌道に対して水平方向に大きな変位を生じる。水平方向に大きな変位を生じた粒子は、後述の擾乱用電極３１３による擾乱用電場と、あらかじめ設置された取り出し軌道３２２上の取り出し用セプタム電磁石３１２によって形成される磁場とによって、取り出し軌道３２２上を通り、加速器１の外へ取り出される。 The particles inside the separatrix continue to oscillate in betatron stably. Particles outside the separatrix undergo a large displacement in the horizontal direction with respect to the design trajectory because the kick action by the additional magnetic field generating shim 311 is accumulated for each revolution. Particles that have undergone a large displacement in the horizontal direction are moved along the extraction orbit 322 by the electric field for disturbance by the disturbance electrode 313 described later and the magnetic field formed by the septum electromagnet 312 for extraction on the extraction orbit 322 set in advance. , and is taken out of the accelerator 1.
　擾乱用電極３１３に印加される電場が切られると、ビームのベータトロン振動振幅の増大が停止し、安定領域内でビームが周回する。これにより、ビームの取り出しを停止することができる。 When the electric field applied to the perturbation electrode 313 is turned off, the betatron oscillation amplitude of the beam stops increasing and the beam orbits within the stable region. This makes it possible to stop beam extraction.
　上記ビームの取り出しのプロセスにおいて、周回中のビームの運動量分散を抑制することは、ビームの空間的な広がりを抑えることができ、セプタム電磁石３１２などに衝突して失われるビームの量を減らすのに有効である。したがって、前述の高周波バケツの面積は、加速終了時点でなるべく小さくし、周回中のビームの運動量分散を抑制することが望ましい。 In the process of extracting the beam, suppressing the momentum dispersion of the circulating beam can suppress the spatial spread of the beam and reduce the amount of the beam lost by colliding with the septum electromagnet 312 or the like. It is valid. Therefore, it is desirable that the area of the high-frequency bucket is made as small as possible at the end of the acceleration to suppress the momentum dispersion of the beam during the orbit.
　しかも、加速電場の減衰には、高周波加速空胴２１の共振のＱ値に基づいて、ある程度の時間がかかる。典型的にはＱ値は３０００程度であり、高周波加速空胴２１への電力入力を停止した時刻から３０００周期程度の時間で高周波電圧振幅が小さくなり、高周波バケツが消失する。高周波電圧振幅の減衰中には、高周波バケツの収縮に伴い、高周波バケツからこぼれる時刻によって各粒子の到達エネルギがばらつく。高周波バケツの消失に時間をかけるほど、その時間に比例してその後の周回ビームの運動量分散が広がる。 Moreover, the attenuation of the accelerating electric field takes a certain amount of time based on the Q value of the resonance of the high-frequency accelerating cavity 21 . Typically, the Q value is about 3000, and the high frequency voltage amplitude becomes small and the high frequency bucket disappears in about 3000 cycles from the time when the power input to the high frequency acceleration cavity 21 is stopped. During the attenuation of the high-frequency voltage amplitude, the arrival energy of each particle varies according to the time when the high-frequency bucket collapses as the high-frequency bucket contracts. The more time it takes for the high-frequency bucket to disappear, the more the momentum dispersion of the subsequent orbiting beam spreads in proportion to that time.
　以上より、加速中の高周波電圧振幅は、高周波バケツを形成できるように、そして加速できるビームの電荷量が充分確保できるならば、高周波バケツはなるべく小さく維持することが、取り出し効率の向上や結果的に照射時間の短縮に有効である。 From the above, if the high frequency voltage amplitude during acceleration can form a high frequency bucket and if the charge amount of the beam that can be accelerated can be secured sufficiently, the high frequency bucket should be kept as small as possible to improve the extraction efficiency and result. It is effective for shortening the irradiation time.
　しかしながら、高周波振幅の電圧を過少にすると、加速途中で高周波バケツが消失し、ビームを目的のエネルギまで加速できないことも起きえる。たとえば、７０ＭｅＶまで加速する際の最適な高周波電圧振幅の値が存在する。しかし、その高周波電圧振幅値で２３５ＭｅＶまで加速しようとしても、加速途中で高周波バケツが消失してしまうため、２３５ＭｅＶまで加速できない。 However, if the high-frequency amplitude voltage is too low, the high-frequency bucket may disappear during acceleration, making it impossible to accelerate the beam to the desired energy. For example, there is an optimum RF voltage amplitude value for acceleration up to 70 MeV. However, even if an attempt is made to accelerate to 235 MeV with that high-frequency voltage amplitude value, the high-frequency bucket disappears during acceleration, so acceleration to 235 MeV is not possible.
　すなわち、目標とする到達エネルギに応じて、取り出し効率あるいは照射時間の観点で最適な電圧振幅が存在する。その最適な電圧振幅で高周波を励起することで、取り出し効率の向上あるいは照射時間の短縮を実現できる。本実施例の加速器１は、上述した、到達エネルギと電圧振幅との対応関係を保持する電圧振幅計算装置４５を備える。 That is, there is an optimum voltage amplitude in terms of extraction efficiency or irradiation time, depending on the target energy to be reached. By exciting the high frequency with the optimum voltage amplitude, it is possible to improve the extraction efficiency or shorten the irradiation time. The accelerator 1 of this embodiment includes the voltage amplitude calculator 45 that holds the correspondence relationship between the arrival energy and the voltage amplitude described above.
　以上、１サイクル中の、ビームの入射から取り出しに関するビームのふるまいについて述べた。加速器１は、以降のサイクルも同様の動作を繰り返す。２サイクル目以降では、すでに加速されたビームが所定のエネルギでビーム通過領域２０内を周回中である。この場合、加速済みのビームに対しても、２サイクル目のビームを加速する高周波電場が作用する。しかし、加速済みのビームにとっては、入射直後のビームを加速する高周波はその周波数が周回周波数とマッチしないため、エネルギが微小に振動するに過ぎない。よって、２サイクル目のビームが十分加速済みのビームのエネルギに近づくまでは、加速済みのビームは、ほとんどエネルギや運動の状態を変化させることなく安定に周回しながら一部は取り出されていく。既に周回中のビームを先行ビームと、その後に発生するビームを後続ビームと、呼ぶこともできる。 So far, we have described the behavior of the beam from its incidence to its extraction during one cycle. The accelerator 1 repeats similar operations in subsequent cycles. After the second cycle, the already accelerated beam is circulating in the beam passage area 20 with a predetermined energy. In this case, the high-frequency electric field that accelerates the beam in the second cycle also acts on the accelerated beam. However, for the beam that has already been accelerated, the energy of the high frequency that accelerates the beam immediately after incidence does not match the circulating frequency, so the energy only oscillates minutely. Therefore, until the beam in the second cycle approaches the energy of the accelerated beam sufficiently, the accelerated beam stably circulates with almost no change in energy or motion, and part of the beam is extracted. A beam that is already circulating can also be referred to as a leading beam, and a beam that is generated after that as a trailing beam.
　２サイクル目のビーム（後続ビーム）のエネルギが加速済みのビーム（先行ビーム）のエネルギに近接すると、より具体的には位相空間上で２サイクル目のビームを内包する高周波バケツが加速済みのビームが存在している領域に重なり始めると、はじめて加速済みのビームに対して有意な影響が高周波から及ぼされる。 When the energy of the second cycle beam (subsequent beam) approaches the energy of the accelerated beam (previous beam), more specifically, the high-frequency bucket containing the second cycle beam in the phase space becomes the accelerated beam does not have a significant effect on the accelerated beam from the radio frequency until it begins to overlap the region where the is present.
　図８は、このタイミングでの位相空間上の分布についての模式図である。図８のグレーに網掛けした領域Ａ１が加速済みの周回ビームが存在する領域であり、ここに２サイクル目のビームを内包する高周波バケツＢｕが入る。 FIG. 8 is a schematic diagram of the distribution on the phase space at this timing. A region A1 shaded in gray in FIG. 8 is a region in which the circulating beam that has already been accelerated exists, and the high-frequency bucket Bu containing the beam of the second cycle is included therein.
　前述の通り、高周波バケツは、運動量分散が小さくなるように適切な形状に制御されており、その運動量方向の高さは周回中のビームよりも小さい。高周波バケツと周回中のビームとが近接すると、周回中のビームは高周波バケツに入ることができず、高周波バケツに押しのけられるように位相空間上の別の位置に移動する。 As mentioned above, the high-frequency bucket is controlled to an appropriate shape so that the momentum dispersion is small, and its height in the momentum direction is smaller than the orbiting beam. When the high frequency bucket and the circulating beam approach each other, the circulating beam cannot enter the high frequency bucket and moves to another position in the phase space so as to be pushed away by the high frequency bucket.
　図９に、２サイクル目のビームを加速完了した瞬間の位相空間におけるビームの分布を示す。図９に示す瞬間では、高周波バケツは、先行ビームがすでに周回している領域を通過し、その影響で先行ビームの分布が乱され、運動量分散が増加している。さらに２サイクル目ビーム（後続ビーム）が高周波バケツの収縮とともにバケツからこぼれ、位相空間上のある領域に配置される。加速済みのビームと新たに加速されたビームとの位相空間上の領域は、このタイミングでは明確な境界をもつ。図９では、加速済のビーム（先行ビーム）が存在する領域Ａ２をドット柄で示し、新たに加速されたビーム（後続ビーム）の存在領域Ａ３を斜線で示す。このように、周回ビームの運動量分散が増える代わりに、新たなビームを追加することが可能となる。 FIG. 9 shows the beam distribution in the phase space at the moment the second cycle beam acceleration is completed. At the instant shown in FIG. 9, the high frequency bucket passes through a region where the leading beam is already circling, the effect of which is to disturb the distribution of the leading beam and increase the momentum dispersion. Furthermore, the second cycle beam (subsequent beam) spills out of the high-frequency bucket as it contracts, and is arranged in a certain area on the phase space. The region on the phase space between the accelerated beam and the newly accelerated beam has a clear boundary at this timing. In FIG. 9, the area A2 where the accelerated beam (preceding beam) exists is indicated by a dot pattern, and the area A3 where the newly accelerated beam (following beam) exists is indicated by oblique lines. In this way, it is possible to add a new beam at the expense of increasing the momentum dispersion of the circulating beam.
　図１０および図１１を用いて、上述の原理によってビームを加速し、加速器１の外へ取り出すときの各機器の制御ダイアグラムと運転フローを説明する。図１０に本実施例の加速器１の制御ブロック図を示す。 Using FIGS. 10 and 11, the control diagram and operation flow of each device when the beam is accelerated according to the principle described above and taken out of the accelerator 1 will be explained. FIG. 10 shows a control block diagram of the accelerator 1 of this embodiment.
　ビームを加速するための構成とその制御系としては、図１０に示すような、高周波加速空胴２１に付随する回転式可変容量キャパシタ２１２と、回転式可変容量キャパシタ２１２の回転軸２１３（図１参照）に接続されるサーボモータ２１４と、サーボモータ２１４を制御するモーター制御装置４１とがある。さらに、高周波加速空胴２１に高周波電力を入力するための入力カプラ２１１（図１参照）と、供給する高周波電力を生成する低レベル高周波発生装置４２およびアンプ４３がある。 As shown in FIG. 10, the configuration for accelerating the beam and its control system include a rotary variable capacitor 212 attached to the high frequency acceleration cavity 21 and a rotating shaft 213 of the rotary variable capacitor 212 (see FIG. 1). ), and a motor control device 41 that controls the servo motor 214 . Further, there is an input coupler 211 (see FIG. 1) for inputting high frequency power to the high frequency acceleration cavity 21, and a low level high frequency generator 42 and amplifier 43 for generating the high frequency power to be supplied.
　回転式可変容量キャパシタ２１２は、モータ制御装置４１により制御される。モータ制御装置４１は、全体制御装置４０により制御される。全体制御装置４０は、治療計画データベース６０中の治療計画データにより予め定められた指示値に基づいて、モータ制御装置４１を制御する。 The rotary variable capacitor 212 is controlled by the motor control device 41 . The motor control device 41 is controlled by the overall control device 40 . The overall control device 40 controls the motor control device 41 based on the indicated values predetermined by the treatment plan data in the treatment plan database 60 .
　予め定められた回転速度でサーボモータ２１４が回転すると、これにより回転軸２１３が回転する。回転軸２１３の回転角が時間的に変化することで、静電容量を時間的に変調される。これにより、基本モードの共振周波数が変化する。 When the servomotor 214 rotates at a predetermined rotational speed, the rotary shaft 213 rotates. The capacitance is temporally modulated by temporally changing the rotation angle of the rotating shaft 213 . This changes the resonant frequency of the fundamental mode.
　低レベル高周波発生装置４２によって発生させた高周波信号をアンプ４３によって増幅することで、高周波加速空胴２１に入力される高周波を作る。低レベル高周波発生装置４２において作る高周波信号の周波数は、前記の基本モードの共振周波数に追従させる。高周波信号の振幅は、治療計画データベース６０によって定められており、全体制御装置４０より指示される。 A high frequency input to the high frequency acceleration cavity 21 is generated by amplifying the high frequency signal generated by the low level high frequency generator 42 with the amplifier 43 . The frequency of the high-frequency signal generated by the low-level high-frequency generator 42 follows the resonance frequency of the fundamental mode. The amplitude of the high-frequency signal is determined by the treatment plan database 60 and instructed by the general control device 40 .
　高調波モード用の低レベル高周波を発生させる装置４２によって発生させた高周波信号をアンプ４３によって増幅することで、高周波加速空胴２１へ入力される高周波電力を作る。高調波モード用低レベル高周波発生装置４２により作られる高周波信号の周波数は、前記の高調波モードの共振周波数に追従させ、振幅は、治療計画データベース６０によって定められたビームのエネルギを電圧振幅計算装置４５が参照し、電圧振幅計算装置４５の演算によって定められた振幅値を全体制御装置４０より指定される。 A high-frequency signal generated by a device 42 for generating low-level high-frequency waves for harmonic mode is amplified by an amplifier 43 to generate high-frequency power to be input to the high-frequency acceleration cavity 21 . The frequency of the high-frequency signal produced by the low-level high-frequency generator 42 for harmonic mode follows the resonance frequency of the harmonic mode, and the amplitude is determined by the energy of the beam determined by the treatment plan database 60. 45 refers to and the amplitude value determined by the calculation of the voltage amplitude calculator 45 is specified by the overall controller 40 .
　ビームを加速器１外に取り出すための構成とその制御系としては、図１０に示す、擾乱用電極３１３に高周波電圧を印加するための高周波電源４６と、この高周波電源４６を制御する擾乱高周波制御装置４７とがある。 The configuration and control system for extracting the beam out of the accelerator 1 includes a high-frequency power source 46 for applying a high-frequency voltage to the disturbance electrode 313 and a high-frequency disturbance control device for controlling the high-frequency power source 46, as shown in FIG. 47.
　高周波電源４６から擾乱用電極３１３に出力される電圧値は、擾乱高周波制御装置４７によって制御されている。高周波電源４６から出力される電圧の指定値は、取り出しビームエネルギと取り出しビームの出力電流とから一意に定まる値として治療計画データベース６０内に保存された治療計画データによって定められている。全体制御装置４０は、その治療計画データから指定値を取得し、擾乱高周波制御装置４７へ指示する。 The voltage value output from the high-frequency power supply 46 to the disturbance electrode 313 is controlled by the high-frequency disturbance control device 47 . The specified value of the voltage output from the high-frequency power supply 46 is determined by the treatment plan data stored in the treatment plan database 60 as a value uniquely determined from the extraction beam energy and the output current of the extraction beam. The general control device 40 acquires the specified value from the treatment plan data and instructs the disturbance high-frequency control device 47 .
　図１１および図１２に基づいて、以上のような加速器１の制御系における、ある二種類のエネルギのビームを連続的に取り出す際の各機器の動作（運転方法）を説明する。図１１は、各機器の動作のタイミングチャートである。図１２は、運転の流れをフローチャートである。 　Based on Figs. 11 and 12, the operation (operating method) of each device in the control system of the accelerator 1 as described above when continuously extracting beams of certain two types of energy will be described. FIG. 11 is a timing chart of the operation of each device. FIG. 12 is a flowchart showing the operation flow.
　図１１のチャートの縦軸は、上から順に、（１）回転式可変容量キャパシタ２１２の回転軸２１３の回転角、（２）高周波加速空胴２１の共振周波数、（３）高周波加速空胴２１に入力される高周波の周波数、（４）加速ギャップ２２３における加速用高周波の振幅、（５）イオン源１２が出力するビームの電流波形、（６）取り出し可能な周回中の電荷量、（７）擾乱用電極３１３に入力される擾乱高周波、（８）加速器１から出力されるビーム電流波形、を示している。図１１に示すチャートの横軸はすべて時間である。 The vertical axis of the chart in FIG. 11 represents, from the top, (1) the rotation angle of the rotary shaft 213 of the rotary variable capacitor 212, (2) the resonance frequency of the high frequency acceleration cavity 21, and (3) the high frequency acceleration cavity 21. (4) the amplitude of the high frequency for acceleration in the acceleration gap 223; (5) the current waveform of the beam output by the ion source 12; The disturbance high frequency input to the disturbance electrode 313 and (8) the beam current waveform output from the accelerator 1 are shown. The horizontal axis of the chart shown in FIG. 11 is all time.
　図１１に示すように、回転式可変容量キャパシタ２１２の回転軸２１３の回転角によって、高周波加速空胴２１の共振周波数は周期的に変化する。それに合わせて、低レベル高周波発生装置４２から出力され、高周波加速空胴２１へ入力される高周波信号の周波数も同期して変化する。ここで、共振周波数が最大となる時刻から次に最大となる時刻までの期間を運転周期と定義する。 As shown in FIG. 11, the resonance frequency of the high-frequency acceleration cavity 21 changes periodically depending on the rotation angle of the rotary shaft 213 of the rotary variable capacitor 212 . Correspondingly, the frequency of the high-frequency signal output from the low-level high-frequency generator 42 and input to the high-frequency acceleration cavity 21 also changes synchronously. Here, the period from the time when the resonance frequency reaches its maximum to the next time when it reaches its maximum is defined as the operation period.
　図１１（５）に示すように、運転周期の開始直後から、イオン源１２からビームが出力される。ビームは、安定なシンクロトロン振動が可能な範囲に入射された場合、加速される。これに対し、シンクロトロン振動が安定しない粒子は、加速できずに加速器１内部の構造物に衝突し、失われる。ここまでが図１２に示す入射プロセスである。入射プロセスは、加速電圧の印加を開始するステップＳ１１と、イオン源からイオンを出力するステップＳ１２を含む。 As shown in FIG. 11(5), a beam is output from the ion source 12 immediately after the start of the operation cycle. A beam is accelerated if it is injected into a range where stable synchrotron oscillation is possible. On the other hand, particles whose synchrotron oscillation is not stable collide with structures inside the accelerator 1 without being accelerated, and are lost. The process up to this point is the injection process shown in FIG. The injection process includes step S11 of starting application of acceleration voltage and step S12 of outputting ions from the ion source.
　図１１に戻り、共振周波数が低下するにつれてビームは加速され、所定の取り出しエネルギ近くまで加速される。その後、高周波加速空胴２１に入力される高周波の振幅を低下させ始める。この低下の開始タイミングは、イオンビームが目標エネルギになる前の所定のタイミングから開始するようにする。例えば、高周波電力の入力を切ってから加速ギャップ２２３に生じていた加速用電場が０になるまでに、目標エネルギに到達すると見込まれるエネルギに達するタイミングから低下を開始させることが望ましい。ここまでが図１２における加速プロセスである。加速プロセスは、イオンビームを加速するステップＳ１３と、加速電圧の印加を停止するステップＳ１４を含む。 Returning to FIG. 11, the beam is accelerated as the resonance frequency decreases, and is accelerated to near the predetermined extraction energy. After that, the amplitude of the high frequency input to the high frequency acceleration cavity 21 begins to decrease. The start timing of this decrease is set to start from a predetermined timing before the ion beam reaches the target energy. For example, it is desirable to start the decrease at the timing when the energy expected to reach the target energy is reached before the acceleration electric field generated in the acceleration gap 223 becomes 0 after the input of the high-frequency power is turned off. This is the acceleration process in FIG. The acceleration process includes step S13 of accelerating the ion beam and step S14 of stopping the application of the acceleration voltage.
　図１１に戻り、加速電場の振幅が十分小さくなった時点で、ビームは、所定の取り出しエネルギに達している。加速が完了した時点で、取り出し可能なビーム量はある値になり、これよりビーム取り出しが可能となる。ビームは、付加磁場発生用シム３１１によって定められたセパラトリクス内を満たすように周回することになる。 Returning to FIG. 11, when the amplitude of the accelerating electric field becomes sufficiently small, the beam reaches a predetermined extraction energy. When the acceleration is completed, the amount of beam that can be extracted reaches a certain value, and beam extraction becomes possible. The beam circulates to fill the separatrix defined by the additional magnetic field generating shim 311 .
　次いで、擾乱用電極３１３による擾乱高周波を印加する。ビームを取り出す時間はあらかじめ定められている。周回中の全電荷がすべて取り出されるか、所定の照射線量が照射されるまで擾乱高周波を印加し、ビームを取り出し続ける。 Next, a disturbance high frequency is applied by the disturbance electrode 313 . The time for extracting the beam is predetermined. The high-frequency disturbance is applied and the beam continues to be extracted until all the circulating charges are extracted or a predetermined irradiation dose is irradiated.
　この間、高周波加速空胴２１に付随のサーボモータ２１４は回転を続け、共振周波数は変動を続ける。入射の周波数と共振周波数とが一致したら、イオン源から再度ビームを出力し、上記同様にビームを加速しつつ、ビームの取り出しも並行して進める。加速終了のごくわずかな時間（加速高周波振幅が減衰中）のみは、擾乱用高周波をオフして照射ビームのエネルギ変動を抑制する。高周波加速空胴２１が作る加速用高周波は、加速プロセス中においてビームの周回周波数と一致しないため、ビームに対する影響はほとんど生じない。よって、ビームは一定のエネルギで周回しながら、印加されている擾乱高周波によって順次取り出されていく。 During this time, the servomotor 214 associated with the high-frequency acceleration cavity 21 continues to rotate, and the resonance frequency continues to fluctuate. When the incident frequency and the resonance frequency match, the beam is output again from the ion source, and while the beam is accelerated in the same manner as described above, the extraction of the beam proceeds in parallel. Only for a very short period of time after the end of acceleration (when the amplitude of the acceleration high frequency is attenuating), the disturbance high frequency is turned off to suppress the energy fluctuation of the irradiation beam. Since the acceleration high frequency generated by the high frequency acceleration cavity 21 does not match the circulating frequency of the beam during the acceleration process, it hardly affects the beam. Therefore, the beam is circulated with constant energy and is sequentially extracted by the applied disturbing high frequency waves.
　擾乱高周波の強度によってではあるが、図１１（６）に示すように、１回目の加速が終了して以降、加速高周波の振幅が減衰中の期間を除き、常に周回電荷量が追加されているため、いつでもビームのオン／オフの制御が可能である。以上が図１２に示す照射プロセスである。 Although it depends on the intensity of the disturbance high frequency, as shown in FIG. 11(6), after the first acceleration is completed, the cyclic charge is always added except for the period during which the amplitude of the acceleration high frequency is attenuating. Therefore, it is possible to control the on/off of the beam at any time. The above is the irradiation process shown in FIG.
　照射プロセスは、取り出し高周波の印加を開始させるステップＳ１５と、取り出し高周波の印加を停止させるステップＳ１６と、照射プロセスが完了したか判定するステップＳ１７と、周回電荷量を測定するステップＳ１８と、次サイクルまでに照射できる電荷量と基準値とを比較するステップＳ１９を含む。ステップＳ１７において、照射プロセスが完了したと判定されると、図１２に示す照射制御処理は終了する。照射プロセスが完了していない場合（Ｓ１７：ＮＯ）、ステップＳ１８へ進む。ステップＳ１９において、次サイクルまでに照射できる電荷量が基準値よりも大きいと判定されると（電荷量＞基準値）、ステップＳ１５へ戻る。次サイクルまでに照射できる電荷量が基準値以下であると判定されると（電荷量≦基準値）、ステップＳ１１へ戻る。 The irradiation process includes a step S15 for starting application of the extraction high-frequency wave, a step S16 for stopping the application of the extraction high-frequency wave, a step S17 for determining whether the irradiation process is completed, a step S18 for measuring the circulating charge amount, and a next cycle. It includes a step S19 of comparing the amount of charge that can be irradiated with a reference value. When it is determined in step S17 that the irradiation process has been completed, the irradiation control process shown in FIG. 12 ends. If the irradiation process has not been completed (S17: NO), the process proceeds to step S18. If it is determined in step S19 that the amount of charge that can be irradiated by the next cycle is greater than the reference value (amount of charge>reference value), the process returns to step S15. If it is determined that the charge amount that can be irradiated by the next cycle is equal to or less than the reference value (charge amount≦reference value), the process returns to step S11.
　図１１に戻る。ある一つのエネルギでの照射が終了すると、次の運転周期に到達するまでの間に、次の運転周期で取り出すべきイオンビームのエネルギに対応したパターンでの運転が開始される。上記のプロセスを繰り返すことで、任意のエネルギを任意の線量で照射可能な加速器１が実現する。 Return to Figure 11. When irradiation with a certain energy ends, operation is started in a pattern corresponding to the energy of the ion beam to be extracted in the next operation cycle until the next operation cycle is reached. By repeating the above process, the accelerator 1 that can irradiate arbitrary energy with arbitrary dose is realized.
　図１１に示した２回目の運転周期（後続するビームの運転周期）は、１回目の運転周期（先行するビームの運転周期）とは異なるエネルギを照射する場合のタイミングチャートを示す。 The second operation cycle (subsequent beam operation cycle) shown in FIG. 11 shows a timing chart when irradiating different energy from the first operation cycle (preceding beam operation cycle).
　ここでは、後続ビームの照射エネルギは、先行ビームの照射エネルギと比較して、より大きい場合を説明する。図１１（４）に示すように、後続ビームの運転が先行ビームの運転と異なるのは、加速高周波の振幅の値とその印加期間である。より大きなエネルギまで加速するには、高周波の印加時間をより長くすることで実現される。前述のとおり、加速後の周回ビームの運動量分散を小さく抑制するために、エネルギ毎に電圧振幅計算装置４５によって計算される振幅値が定められている。これにより高周波バケツを不要に大きくすることを避け、周回ビームの運動量分散を抑制できる。さらに、ビームの取り出し効率の増加とビーム照射時間の短縮とを実現できる。 Here, a case will be described in which the irradiation energy of the subsequent beam is greater than the irradiation energy of the preceding beam. As shown in FIG. 11(4), the operation of the trailing beam differs from the operation of the leading beam in the amplitude value of the accelerating high-frequency wave and its application period. Acceleration to higher energy is achieved by increasing the application time of the high frequency. As described above, the amplitude value calculated by the voltage amplitude calculator 45 is determined for each energy in order to suppress the momentum dispersion of the circulating beam after acceleration. This avoids making the high-frequency bucket unnecessarily large, and suppresses the momentum dispersion of the circulating beam. Furthermore, it is possible to increase the beam extraction efficiency and shorten the beam irradiation time.
　上記の説明では、常に、イオンが入射可能なタイミングでイオンの入射を行うことを想定している。照射すべき電荷量と現に周回しているビーム量とを比較して、周回電荷量が十分に大きい場合は、新たなイオンの入射（イオン源１２からのイオン出力）をしないことも考えられる。その場合は、加速器１にビーム量の監視手段として、電極型周回ビーム量モニタＢＭ（図２参照）が設置される。ビーム量モニタＢＭは、ビーム軌道上の任意の場所に設置される電極であり、電極に励起される電圧および電荷量に比例する信号を取り出すことが可能である。あらかじめ定められた電荷量と比較して大きな電荷量が周回している場合は、イオンの入射をスキップさせる。 In the above explanation, it is assumed that ions are always injected at the timing when ions can be injected. The amount of charge to be irradiated is compared with the amount of beam actually circulating, and if the amount of circulating charge is sufficiently large, it is conceivable not to inject new ions (ion output from the ion source 12). In that case, the accelerator 1 is provided with an electrode-type orbiting beam intensity monitor BM (see FIG. 2) as means for monitoring the beam intensity. The beam amount monitor BM is an electrode installed at an arbitrary position on the beam trajectory, and can extract a signal proportional to the voltage and charge amount excited on the electrode. If the amount of charge circulating is greater than the predetermined amount of charge, the injection of ions is skipped.
　ビーム量の監視手段は他の方式でもよい。直接ビーム量を計測する必要はない。ビームの取り出し量と擾乱用高周波振幅との比は、周回ビーム量に関連する量であるため、その比からビーム量を推測するなどの方法でもよい。 Other methods may be used for monitoring the beam amount. There is no need to measure the beam amount directly. Since the ratio of the amount of extracted beam to the high-frequency amplitude for disturbance is an amount related to the amount of circulating beam, a method of estimating the amount of beam from the ratio may be used.
　例えば、加速空胴のピックアップ信号取得用のループアンテナ、または、入力カプラからの反射波モニタなどによって、ビーム周回量を計測することも可能である。その場合、ビームの周回周波数とビームのバンチ構造とを考慮してあらかじめ校正されており、ビームのエネルギと加速停止からの経過時間とに基づいた校正テーブルが用意される。 For example, it is also possible to measure the amount of beam rotation by using a loop antenna for picking up the pick-up signal of the accelerating cavity or a reflected wave monitor from the input coupler. In this case, calibration is performed in advance in consideration of the circulating frequency of the beam and the bunch structure of the beam, and a calibration table based on the energy of the beam and the elapsed time from acceleration stop is prepared.
　図１３に、ビーム量を計測する処理のフローチャートを示す。ビーム量計測処理は、例えば、加速電極のピックアップ信号を取得するステップＳ２０、取得した信号の周波数を解析するステップＳ２１、ビーム周波数に対応する信号強度を取得するステップＳ２２、および、周波数特性と加速停止からの経過時間とでビーム量に換算するステップＳ２３を含む。 FIG. 13 shows a flowchart of processing for measuring the beam amount. The beam amount measurement process includes, for example, a step S20 of acquiring a pick-up signal of the acceleration electrode, a step S21 of analyzing the frequency of the acquired signal, a step S22 of acquiring the signal intensity corresponding to the beam frequency, and frequency characteristics and acceleration stop. A step S23 is included in which the amount of beam is converted with the elapsed time from .
　すなわち、ビーム量計測処理では、計測開始の後（Ｓ２０）、モニタ信号の特定周波数成分の信号を取り出し（Ｓ２１，Ｓ２２）、校正テーブルから周回ビーム量に換算する（Ｓ２３）。これにより、周回電荷量に基づいて、新たなイオンの入射をスキップさせるか否かを判定することができる。 That is, in the beam amount measurement process, after the measurement is started (S20), the signal of the specific frequency component of the monitor signal is extracted (S21, S22) and converted to the circulating beam amount from the calibration table (S23). Accordingly, it is possible to determine whether or not to skip the injection of new ions based on the circulating charge amount.
　高周波加速空胴２１は、上述の構成に限定されない。例えば、高周波空胴の変調機構として、回転式可変容量キャパシタ２１２による静電容量の変化に代えて、透磁率の変化を利用することもできる。空胴内部にフェライト磁性体を設置し、フェライト磁性体の性質である外部磁場による透磁率変化を利用することができる。 The high frequency acceleration cavity 21 is not limited to the configuration described above. For example, as a modulating mechanism for the high-frequency cavity, instead of changing the electrostatic capacity of the rotary variable capacitor 212, the change in magnetic permeability can be used. By placing a ferrite magnetic material inside the cavity, it is possible to utilize the change in magnetic permeability caused by an external magnetic field, which is the property of the ferrite magnetic material.
　その場合の高周波加速空胴２１の構造を図１４に示す。図１４は、加速空胴の一端が同軸構造となった共振空胴であり、同軸構造部に内胴体と外導体で囲まれた間隙中にフェライト磁性体２３１が設置されている。フェライト磁性体２３１にはバイアス電流コイル２３２が巻かれており、外部の電源に接続されている。バイアス電流コイル２３２に印加する電流は、高周波周波数から決まる。フェライト磁性体２３１の透磁率がバイアス電流の値によって決まることから、あらかじめ共振周波数とバイアス電流の関係をテーブル化することが可能である。そこで、この類型の加速空胴を用いる場合、可変容量キャパシタを用いる変調と異なり、バイアス電流の制御によって高周波の周波数を制御する。 The structure of the high frequency acceleration cavity 21 in that case is shown in FIG. FIG. 14 shows a resonance cavity in which one end of the acceleration cavity has a coaxial structure, and a ferrite magnetic body 231 is placed in the gap surrounded by the inner body and the outer conductor in the coaxial structure. A bias current coil 232 is wound around the ferrite magnetic body 231 and connected to an external power source. The current applied to the bias current coil 232 depends on the radio frequency. Since the magnetic permeability of the ferrite magnetic body 231 is determined by the value of the bias current, it is possible to form a table of the relationship between the resonance frequency and the bias current in advance. Therefore, when using this type of acceleration cavity, unlike modulation using a variable capacitor, the high frequency is controlled by controlling the bias current.
　このように構成される本実施例によれば、イオン入射プロセス、イオン加速プロセス、イオンビームの取出しプロセス、減速プロセスという時間的に直列なプロセスを並列的に実行することができる。本実施例の加速器１は、入射プロセスおよび加速プロセスを繰り返して実行し、照射エネルギに対応するビームが常に加速器内に補充されている状態を維持する。したがって、本実施例の加速器１は、ビームを照射できない時間を短くし、ビーム取り出しの効率を高めることができる。 According to this embodiment configured in this way, it is possible to execute time-series processes in parallel, namely, the ion injection process, the ion acceleration process, the ion beam extraction process, and the deceleration process. The accelerator 1 of this embodiment repeatedly executes the injection process and the acceleration process, and maintains a state in which the beam corresponding to the irradiation energy is constantly replenished within the accelerator. Therefore, the accelerator 1 of this embodiment can shorten the time during which the beam cannot be irradiated and improve the efficiency of beam extraction.
　実施例２を説明する。本実施例を含む以下の実施例では、実施例１との相違を中心に述べる。実施例２は、図示を省略するが、当業者であれば理解でき、実施可能である。 Example 2 will be explained. In the following examples including this example, differences from the first example will be mainly described. Embodiment 2 is not shown, but can be understood and implemented by those skilled in the art.
　実施例１では、加速核種を水素イオンとしたが、実施例２では、加速核種を炭素イオンとする。実施例２の加速器は、炭素イオンを、核子当り運動エネルギ１４０ＭｅＶ～４３０ＭｅＶの範囲での取り出しが可能な周波数変調型の可変エネルギ加速器である。 In Example 1, hydrogen ions were used as accelerating nuclides, but in Example 2, carbon ions were used as accelerating nuclides. The accelerator of Example 2 is a frequency-modulated variable energy accelerator capable of extracting carbon ions with a kinetic energy per nucleon in the range of 140 MeV to 430 MeV.
　実施例２の加速器の動作原理、その機器構成、その操作手順は、実施例１で述べたと同様であるため、詳細な説明は省略する。 The operating principle, equipment configuration, and operation procedure of the accelerator of Example 2 are the same as those described in Example 1, so detailed descriptions will be omitted.
　実施例２の加速器が実施例１の加速器１と異なるのは、軌道半径の大きさと磁場とエネルギの関係、周回周波数とエネルギの関係である。それらは、実施例１に示した加速器１から、ビームの磁気剛性率の比に軌道半径と磁場の積を比例させることで決定することができる。 The difference between the accelerator of Example 2 and the accelerator 1 of Example 1 is the relationship between the size of the orbital radius, the magnetic field and energy, and the relationship between the orbital frequency and energy. They can be determined from the accelerator 1 shown in Example 1 by making the product of the orbital radius and the magnetic field proportional to the ratio of the magnetic stiffness of the beam.
　よって、実施例２の加速器においても、実施例１の加速器１と同様の構成および手法によって、実施例１と同様の作用効果を奏する。すなわち、実施例２の加速器は、周回ビームの運動量分散を抑制することができ、従来技術の運転方法に比べて、取り出し効率を向上でき、粒子線治療に用いた場合の照射時間を短縮できる。 Therefore, the accelerator of the second embodiment also has the same effects as the first embodiment by using the same configuration and method as the accelerator 1 of the first embodiment. That is, the accelerator of Example 2 can suppress the momentum dispersion of the orbiting beam, can improve the extraction efficiency and shorten the irradiation time when used for particle beam therapy, compared to the operation method of the conventional technology.
　図１５を用いて、実施例３を説明する。実施例３は、実施例１で述べた加速器１、あるいは実施例２で述べた加速器を備える粒子線治療システム１０００について説明する。図１５は、粒子線治療システムの全体構成図である。 Example 3 will be described with reference to FIG. A third embodiment describes a particle beam therapy system 1000 including the accelerator 1 described in the first embodiment or the accelerator described in the second embodiment. FIG. 15 is an overall configuration diagram of a particle beam therapy system.
　図１５に示すように、粒子線治療システム１０００は、患部の体表からの深さによって照射する陽子線あるいは炭素線（以下ではまとめてビームと呼ぶ）のエネルギを適切な値にして、患者に照射する装置である。 As shown in FIG. 15, the particle beam therapy system 1000 sets the energy of proton beams or carbon beams (hereinafter collectively referred to as beams) to an appropriate value depending on the depth from the body surface of the affected area, and treats the patient. It is an irradiation device.
　粒子線治療システム１０００は、加速器１、ビーム輸送系２、照射装置３、治療台４、全体制御装置４０、照射制御装置５０、治療計画データベース６０、治療計画装置７０を備える。 The particle beam therapy system 1000 includes an accelerator 1, a beam transport system 2, an irradiation device 3, a treatment table 4, a general control device 40, an irradiation control device 50, a treatment plan database 60, and a treatment planning device 70.
　加速器１は、実施例１または実施例２で述べた。ビーム輸送系２は、加速器１で加速されたビームを照射装置３へ輸送する機構である。照射装置３は、ビーム輸送系２によって輸送されたビームを、治療台４に固定された患者５内の標的に照射する装置である。全体制御装置４０は、加速器１、ビーム輸送系２および照射装置３を制御する。照射制御装置５０は、標的に対するビーム照射を制御する。治療計画データベース６０は、治療計画装置７０により作成された治療計画を記憶する。治療計画装置７０は、標的に対するビームの照射計画を作成する。 Accelerator 1 was described in Example 1 or Example 2. The beam transport system 2 is a mechanism that transports the beam accelerated by the accelerator 1 to the irradiation device 3 . The irradiation device 3 is a device that irradiates a target in the patient 5 fixed on the treatment table 4 with the beam transported by the beam transport system 2 . A general controller 40 controls the accelerator 1 , the beam transport system 2 and the irradiation device 3 . The irradiation controller 50 controls beam irradiation to the target. The treatment plan database 60 stores treatment plans created by the treatment planning device 70 . The treatment planning device 70 creates a beam irradiation plan for the target.
　粒子線治療システム１０００では、照射する粒子線のエネルギと線量が治療計画によって定められる。治療計画により定められた、粒子線のエネルギと照射量を全体制御装置４０から照射制御装置５０に順次入力する。これにより、粒子線治療システム１０００は、適切な照射量を照射した時点で次のエネルギに移行し、再度粒子線を照射するという手順を実施する。 In the particle beam therapy system 1000, the energy and dose of the irradiated particle beam are determined by the treatment plan. The energy and dose of the particle beam determined by the treatment plan are sequentially input from the overall control device 40 to the irradiation control device 50 . As a result, the particle beam therapy system 1000 performs a procedure of transferring to the next energy when an appropriate dose is applied, and irradiating the particle beam again.
　このように構成される実施例３の粒子線治療システム１０００によれば、実施例１の加速器１または実施例２の加速器の特性である、短時間で照射完了できる点を利用することができるため、照射時間の短いシステムを提供できる。 According to the particle beam therapy system 1000 of the third embodiment configured in this manner, it is possible to utilize the characteristic of the accelerator 1 of the first embodiment or the accelerator of the second embodiment that irradiation can be completed in a short time. , can provide a system with a short irradiation time.
　粒子線治療システム１０００のビーム輸送系２は、固定式の照射装置に代えて、回転ガントリを用いることもできる。回転ガントリは、照射装置３ごと患者５の周りを回転し、ビームを照射することができる。さらに、固定式の照射装置３を複数設けてもよい。さらに、ビーム輸送系２を設けずに、加速器１から照射装置３へビームを直接輸送する構造としてもよい。 The beam transport system 2 of the particle beam therapy system 1000 can also use a rotating gantry instead of a fixed irradiation device. The rotating gantry can rotate around the patient 5 together with the irradiation device 3 to irradiate the beam. Furthermore, a plurality of fixed irradiation devices 3 may be provided. Furthermore, the beam may be directly transported from the accelerator 1 to the irradiation device 3 without providing the beam transport system 2 .
　なお、本発明は、上述した実施形態に限定されない。当業者であれば、本発明の範囲内で、種々の追加や変更等を行うことができる。上述の実施形態において、添付図面に図示した構成例に限定されない。本発明の目的を達成する範囲内で、実施形態の構成や処理方法は適宜変更することが可能である。 It should be noted that the present invention is not limited to the above-described embodiments. Those skilled in the art can make various additions, modifications, etc. within the scope of the present invention. The above-described embodiments are not limited to the configuration examples illustrated in the accompanying drawings. The configuration and processing method of the embodiment can be changed as appropriate within the scope of achieving the object of the present invention.
　また、本発明の各構成要素は、任意に取捨選択することができ、取捨選択した構成を具備する発明も本発明に含まれる。さらに特許請求の範囲に記載された構成は、特許請求の範囲で明示している組合せ以外にも組み合わせることができる。 In addition, each component of the present invention can be selected arbitrarily, and inventions having selected configurations are also included in the present invention. Furthermore, the configurations described in the claims can be combined in addition to the combinations specified in the claims.
１…加速器
２…ビーム輸送系
３…照射装置
１１…電磁石
１２…イオン源
１３…コイル
２０…ビーム通過領域
２１…高周波加速空胴
３３…トリムコイル
４０…全体制御装置
４１…モーター制御装置
４２…低レベル高周波発生装置
４３…アンプ
４５…電圧振幅計算装置
４６…高周波電源
４７…擾乱高周波制御装置
５０…照射制御装置
６０…治療計画データベース
７０…治療計画装置
１１１…取り出しビーム用貫通口
１１２，１１３…コイル接続用貫通口
１１４…高周波電力入力用貫通口
１１５…ビーム入射用貫通口
１２１…リターンヨーク
１２２…天板
１２３…磁極
１３０…入射部
２１１…入力カプラ
２１２…回転式可変容量キャパシタ
２１３…回転軸
２１４…サーボモータ
２２１…ディー電極
２２２…接地電極
２２３…加速ギャップ
２３１…フェライト磁性体
２３２…バイアス電流コイル
３１１…付加磁場発生用シム
３１２…取り出し用セプタム電磁石
３１３…擾乱用電極
３２２…取り出し軌道
１０００…粒子線治療システム Reference Signs List 1 Accelerator 2 Beam transport system 3 Irradiation device 11 Electromagnet 12 Ion source 13 Coil 20 Beam passage area 21 High frequency acceleration cavity 33 Trim coil 40 Overall control device 41 Motor control device 42 Low Level high-frequency generator 43 Amplifier 45 Voltage amplitude calculator 46 High-frequency power supply 47 High-frequency disturbance control device 50 Irradiation control device 60 Treatment plan database 70 Treatment planning device 111 Extraction beam through- holes 112, 113 Coil Through-hole for connection 114 High-frequency power input through-hole 115 Beam incident through-hole 121 Return yoke 122 Top plate 123 Magnetic pole 130 Incidence part 211 Input coupler 212 Rotary variable capacitor 213 Rotary shaft 214 Servo motor 221 Dee electrode 222 Ground electrode 223 Acceleration gap 231 Ferrite magnetic material 232 Bias current coil 311 Additional magnetic field generating shim 312 Extraction septum electromagnet 313 Disturbance abuse electrode 322 Extraction trajectory 1000 Particles Radiation therapy system

Claims (5)

  1. 　主磁場と周波数変調された高周波電場とにより、イオン源から供給されたイオンを加速してビームを生成する周回軌道型加速器であって、
    　　周波数変調が可能であり、イオンを加速する加速高周波を印加する加速高周波印加装置と、
    　　前記加速高周波とは異なる周波数であって、前記ビームを取出すための取出し高周波を印加する取出し高周波印加装置と、
    　　擾乱磁場領域を形成する擾乱磁場領域形成部と、
    　　ビーム取り出し用のセプタム電磁石と、を備え、
    　前記ビームの取り出し中において、前記イオン源から新たなイオンが供給されて加速される
    加速器。     An orbital accelerator that accelerates ions supplied from an ion source to generate a beam with a main magnetic field and a frequency-modulated high-frequency electric field,
    an accelerating high-frequency applying device capable of frequency modulation and applying an accelerating high-frequency wave for accelerating ions;
    an extracting high-frequency applying device for applying an extracting high-frequency wave for extracting the beam, the extracting high-frequency applying device having a frequency different from the accelerating high-frequency wave;
    a disturbance magnetic field region forming part for forming a disturbance magnetic field region;
    a septum magnet for beam extraction;
    An accelerator into which new ions are supplied from the ion source and accelerated during extraction of the beam.
  2. 　主磁場と周波数変調された高周波電場とにより、イオン源から供給されたイオンを加速してビームを生成する周回軌道型加速器であって、
    　　周波数変調が可能であり、イオンを加速する加速高周波を印加する加速高周波印加装置と、
    　　前記加速高周波とは異なる周波数であって、前記ビームを取出すための取出し高周波を印加する取出し高周波印加装置と、
    　　複数極数の磁場成分を含み、少なくとも４極磁場成分を含む高次磁場よりなる擾乱磁場領域を形成する擾乱磁場領域形成部と、
    　　ビーム取り出し用のセプタム電磁石と、を備え、
    　あるサイクルで前記イオン源から供給されたイオンが、前記サイクルより前の他サイクルで供給されたイオンであって既に周回しているイオンと略同一のエネルギを持つまで加速される
    加速器。     An orbital accelerator that accelerates ions supplied from an ion source to generate a beam with a main magnetic field and a frequency-modulated high-frequency electric field,
    an accelerating high-frequency applying device capable of frequency modulation and applying an accelerating high-frequency wave for accelerating ions;
    an extracting high-frequency applying device for applying an extracting high-frequency wave for extracting the beam, the extracting high-frequency applying device having a frequency different from the accelerating high-frequency wave;
    a disturbed magnetic field region forming unit for forming a disturbed magnetic field region composed of a high-order magnetic field including magnetic field components with a plurality of poles and including at least four pole magnetic field components;
    a septum magnet for beam extraction;
    An accelerator in which ions supplied from the ion source in one cycle are accelerated until they have approximately the same energy as ions supplied in another cycle prior to the said cycle and already orbiting.
  3. 　イオンを加速してビームを生成する加速器であって、
    　対向して配置される一対の磁石であって、その間に磁場を形成するための磁極を有する前記一対の磁石と、
    　イオンを前記一対の磁石間へ出力するイオン源と、
    　前記イオンを加速する加速用電場を形成する加速電極と、
    　前記加速用電場の周波数を変調するための変調部と、
    　前記一対の磁石の磁極間に配置され、前記磁極が形成する磁場により周回する前記イオンに対して安定領域からのキック作用を与えるキック部と、
    　前記イオンに動径方向の擾乱を与える擾乱用電場を発生させる擾乱部と、
    　前記加速用電場を制御する高周波電場制御部と、
    　前記加速用電場の振幅値を前記高周波電場制御部に入力する高周波電場振幅決定手段と、
    　前記擾乱用電場を制御する擾乱強度制御部と、
    を備え、
    　前記一対の磁石によって形成される、異なるエネルギのイオンがそれぞれ周回する環状の複数のイオンの周回軌道が集約する領域と離散する領域を有しており、
    　前記変調部はある周期によって周期的に電場周波数を変調させ、
    　前記高周波電場振幅決定手段は、照射するビームのエネルギに応じて電圧振幅を定めるものであり、
    　前記イオン源は、前記加速用電場の周波数が特定の値となる期間にイオンを出力し、
    　前記イオンが出力される周波数の値は、取り出されるビームのエネルギに対応する周回周波数とずれており、
    　前記イオン源から出力されたイオンが、別のサイクルで出力されたイオンであって、既に周回している状態のイオンとエネルギが略同一となるまで加速される
    加速器。     An accelerator for accelerating ions to produce a beam,
    a pair of magnets arranged facing each other, the pair of magnets having magnetic poles for forming a magnetic field therebetween;
    an ion source that outputs ions between the pair of magnets;
    an accelerating electrode that forms an accelerating electric field that accelerates the ions;
    a modulation unit for modulating the frequency of the accelerating electric field;
    a kick portion that is arranged between the magnetic poles of the pair of magnets and that gives a kick action from the stable region to the ions orbiting by the magnetic field formed by the magnetic poles;
    a disturbance unit that generates a disturbance electric field that disturbances the ions in the radial direction;
    a high-frequency electric field control unit that controls the electric field for acceleration;
    high-frequency electric field amplitude determination means for inputting the amplitude value of the acceleration electric field to the high-frequency electric field control unit;
    a disturbance intensity control unit that controls the electric field for disturbance;
    with
    Circular trajectories of a plurality of circular ions formed by the pair of magnets, in which ions of different energies respectively circulate, have an area where orbits are concentrated and an area where the orbits are discrete,
    The modulating unit periodically modulates the electric field frequency according to a period,
    The high-frequency electric field amplitude determining means determines the voltage amplitude according to the energy of the irradiated beam,
    The ion source outputs ions during a period in which the frequency of the accelerating electric field is a specific value,
    the value of the frequency at which the ions are output is deviated from the orbital frequency corresponding to the energy of the extracted beam;
    An accelerator in which ions output from the ion source are ions output in another cycle and are accelerated until they have substantially the same energy as ions already in orbit.
  4. 　さらに、ビーム量監視手段を備え、
    　前記ビーム量監視手段によって得られる周回ビーム量に基づいて、前記イオンを出力するか否かを判断する
    請求項１に記載の加速器。     Furthermore, a beam amount monitoring means is provided,
    2. The accelerator according to claim 1, wherein whether or not to output said ions is determined based on the circulating beam amount obtained by said beam amount monitoring means.
  5. 　請求項１～４のいずれか一項に記載の加速器で加速されたイオンを標的に照射する照射装置と、
    　前記加速器および前記照射装置を制御する制御装置と、
    を備える
    粒子線治療システム。     an irradiation device for irradiating a target with ions accelerated by the accelerator according to any one of claims 1 to 4;
    a control device that controls the accelerator and the irradiation device;
    A particle beam therapy system with
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008507826A (en) * 2004-07-21 2008-03-13 スティル・リバー・システムズ・インコーポレーテッド Programmable high-frequency waveform generator for synchrocyclotron
JP2021108759A (en) * 2020-01-07 2021-08-02 株式会社日立製作所 Particle beam treatment system, ion beam generation method, and control program

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008507826A (en) * 2004-07-21 2008-03-13 スティル・リバー・システムズ・インコーポレーテッド Programmable high-frequency waveform generator for synchrocyclotron
JP2021108759A (en) * 2020-01-07 2021-08-02 株式会社日立製作所 Particle beam treatment system, ion beam generation method, and control program

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
LINDBACK S.: "Beam Stacking and Long Burst Operation in Synchrocyclotrons", IEEE TRANSACTIONS ON NUCLEAR SCIENCE, IEEE, USA, vol. 18, no. 3, 1 January 1971 (1971-01-01), USA, pages 328 - 331, XP093087195, ISSN: 0018-9499, DOI: 10.1109/TNS.1971.4326043 *
SALMON G.L.: "Beam stacking in the Harwell synchrocyclotron", NUCLEAR INSTRUMENTS AND METHODS, NORTH-HOLLAND, vol. 21, 1 January 1963 (1963-01-01), pages 313 - 317, XP093087193, ISSN: 0029-554X, DOI: 10.1016/0029-554X(63)90130-7 *

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