JP2012009181A - Beam emission device and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a beam emission device and a control method thereof capable of simultaneously supplying emission beams to two or more transport lines from one synchrotron without beam loss and increasing a synchrotron use efficiency per unit time in accordance with a beam use request.SOLUTION: The beam emission device R according to the present invention comprise: a synchrotron 1 where a particle beam goes around with betatron oscillation; a high-frequency acceleration cavity 3 that is provided in the synchrotron 1 and accelerates or decelerates when the particle beam is applied to a longitudinal high-frequency electric field parallel to an advance direction of the particle beam; and a beam transport line 2 to which the particle beam connected to and emitted from the synchrotron 1 is transported. This beam emission device includes control means for controlling a phase of the longitudinal high-frequency electric field caused by the high-frequency acceleration cavity 3 so that the phase is shifted by 180 degrees to the particle beam that goes around in a predetermined stationary state in the synchrotron 1 and for polarizing a momentum and an emission angle of the particle beam emitted from the synchrotron 1.

Description

  The present invention relates to accelerator science, and more particularly to a beam extraction apparatus that divides and emits a beam such as heavy particles and a control method thereof.

Conventionally, methods often used for slow extraction of beams such as heavy particles circulating in the synchrotron include the following.
The first method is to use betatron frequency control by changing the amount of excitation of the quadrupole electromagnet, widen the size of the beam that circulates in the synchrotron, and kick the beam out of the synchrotron by the electric field of the deflector electrode. Is emitted.
As a second method, by applying a voltage (RF-KO voltage) perpendicular to the beam traveling direction to the RF-KO electrode installed in the synchrotron, the betatron amplitude is increased, and the deflector A beam is emitted from the synchrotron by the electric field of the electrode (Non-Patent Document 1).

  Here, for the beam particles bunched by a longitudinal high-frequency electric field parallel to the beam traveling direction in the synchrotron and rotating around the synchrotron, the ring (synchrotron) ), The momentum distribution of the outgoing beam depends on the amplitude and phase of the synchrotron oscillation (Non-Patent Document 2).

M. Tomizawa, et al., “Slow beam extraction at TARN II”, Nuclear Instruments and Methods in Physics Research A 326 (1993) 399-406. T. Furukawa, et al., “Contribution of synchrotron oscillation to spill ripple in RF-knockout slow-extraction”, Nuclear Instruments and Methods in Physics Research A 539 (2005) 44-53.

By the way, in the beam emission from the synchrotron using the slow extraction method, in the conventional method, one beam is emitted for one synchrotron and one outgoing beam transport line from the synchrotron. Therefore, it is very difficult to divide a beam from one synchrotron into two at the same time without beam loss, or to divide a beam passing through one outgoing beam transport line into two or more.
Therefore, the beam can be supplied only from one beam port, and when the beam rate is limited, the beam that cannot be used up and remains in the synchrotron is discarded, and the beam is wasted.

  In view of the above situation, the present invention makes it possible to supply an exit beam to two or more transport lines simultaneously from one synchrotron without beam loss. It is an object of the present invention to provide a beam extraction apparatus capable of increasing the utilization efficiency and a control method thereof.

  In order to achieve the above object, a beam extraction apparatus according to the first aspect of the present invention includes a synchrotron in which a particle beam circulates while oscillating with a betatron, and a vertical beam provided in the synchrotron and parallel to the traveling direction of the particle beam. A beam extraction apparatus comprising: a high-frequency acceleration cavity that accelerates or decelerates by applying a directional high-frequency electric field; and a beam transport line that is connected to the synchrotron and transports a particle beam emitted from the synchrotron, Control is made so that the phase of the longitudinal high-frequency electric field by the high-frequency acceleration cavity is shifted by 180 degrees with respect to the particle beam circulating in a predetermined steady state in the synchrotron, and the momentum and emission of the particle beam emitted from the synchrotron Control means for making the angle bipolar is provided.

  The control method of the beam extraction apparatus according to the second aspect of the present invention includes a synchrotron in which a particle beam circulates while oscillating with a betatron, and a vertical high-frequency electric field that is provided in the synchrotron and is parallel to the traveling direction of the particle beam. A control method of a beam extraction apparatus comprising: a high-frequency acceleration cavity that accelerates or decelerates by application; a beam transport line that is connected to the synchrotron and transports a particle beam emitted from the synchrotron; and a control unit. The high-frequency accelerating cavity applies the longitudinal high-frequency electric field to the particle beam to circulate the particle beam in a predetermined steady state, and the control means is configured to phase the longitudinal high-frequency electric field by the high-frequency accelerating cavity. Is controlled so as to be shifted by 180 degrees, and the momentum and the emission angle of the particle beam emitted from the synchrotron are controlled. To poling.

  According to the present invention, it is possible to supply an outgoing beam to two or more transport lines simultaneously from one synchrotron without beam loss, and use efficiency of the synchrotron per unit time according to the beam usage requirements. Can be raised.

It is the figure which looked at the typical particle beam irradiation apparatus from the upper part. It is a conceptual diagram showing the mode of the slow extraction of the beam of a particle beam using the third-order resonance of betatron oscillation on transverse phase space, and the perturbation of a hexapole magnetic field. It is the figure which looked at the particle beam irradiation apparatus of an embodiment from the upper part. FIG. 5 is a diagram illustrating a trajectory in a longitudinal phase space of particles bunched without acceleration / deceleration by a longitudinal high-frequency electric field in a direction parallel to a traveling direction of a beam in the synchrotron according to the embodiment; ) Is a diagram in the case of γ <γ _t , and (b) is a diagram in the case of γ> γ _t . (a), (b) and (c) is a diagram of figures and the steady state in the initial state when shifted 180 degrees the phase of the figure, the high-frequency electric field bunching state in each case gamma <gamma _t . (a), (b), and (c) are respectively a bunched state diagram when γ> γ _t , an initial state diagram and a steady state diagram when the phase of the high-frequency electric field is shifted by 180 degrees. . FIG. 6C is a diagram showing how the output beam momentum distribution is dipolarized when the beam in the state of FIG. 5C is emitted using the third-order resonance of betatron oscillation and a hexapole magnetic field, and FIG. It is a figure in the case of ξ <0, and (b) is a figure in the case of chromaticity ξ> 0. It is a figure showing on the phase space of a horizontal direction the bipolarization of the beam outgoing angle which arises when the momentum distribution of an outgoing beam is bipolarized. FIG. 3 shows a state in which a beam having a polarized momentum and a beam exit angle X ′ separates the first and second beams by a deflection angle difference of a deflecting electromagnet provided in the exit beam transport line and a three-plate electrode. FIG. It is a perspective view which shows the state which is irradiating a patient (irradiation object) with the 1st beam and the 2nd beam.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a view of the particle beam irradiation apparatus T as viewed from above.
The particle beam irradiation apparatus T is a typical particle beam irradiation apparatus to which the present invention is applied, and is an apparatus that irradiates a diseased part to be irradiated with a predetermined dose of a particle beam of a charged particle such as a carbon ion nucleus by scanning irradiation or the like. .

The particle beam irradiation apparatus T includes a synchrotron 1 that accelerates charged particles to high energy and circulates as a particle beam, and an outgoing beam transport line 2 that transports the particle beam extracted from the synchrotron 1. Yes.
In addition to the equipment shown in FIG. 1, the actual particle beam irradiation apparatus T includes a beam profile monitor that measures the dose of the synchrotron 1, a beam profile monitor that measures the dose of the outgoing beam transport line 2, and the like. In FIG. 1, it is omitted.

<Synchrotron 1>
The synchrotron 1 is configured in a ring shape, and accelerates charged particles such as carbon nuclei to high energy by synchronizing the period of the acceleration high-frequency electric field applied to the particle beam with the particle rotation period. Therefore, the synchrotron 1 corresponds to an “accelerator”.

  The synchrotron 1 has, as main components, a high-frequency accelerating cavity 3 that generates a high-frequency electric field applied to a particle beam of charged particles in the synchrotron 1 and a beam of particle beams traveling in the synchrotron 1 in a circular orbit. Deflection electromagnet 4, a converging quadrupole electromagnet 5 for converging the spread of the beam of particle beams on the circular orbit, a divergent quadrupole electromagnet 6 for diverging the narrowing of the beam, and third-order resonance of betatron oscillation of the beam , And a separatrix generating hexapole electromagnet 7 that divides and forms a stable circulation region and a resonance region in the phase space, and a chromaticity correction hexapole electromagnet 12 for adjusting the chromaticity of the ring (synchrotron 1). And when taking out the beam of the particle beam that circulates in the synchrotron 1 to the outgoing beam transport line 2, RF (Radio Frequency) − The RF-KO electrode 8 O the (Knockout) voltage is applied to the beam, and a deflector electrode 9 for emitting towards the beam of the particle beam on the emission beam transport line 2. Separatrix means between the stable circulation region and the resonance region.

Control of the particle beam irradiation apparatus T is performed by a control means (not shown). The control means is composed of circuits such as a computer and various power supply circuits.
The high-frequency acceleration cavity 3 is a device that generates a high-frequency electric field for accelerating or decelerating particles (charged particles) in the synchrotron 1.
The high-frequency accelerating cavity 3 is accelerated or decelerated when particles (charged particles) reach an acceleration gap (not shown) by supplying high-frequency power into the synchrotron 1 by the control means. Energy is supplied to the particles (charged particles) by well synchronizing the phase of the high-frequency voltage generated in the high-frequency acceleration cavity 3 and the position of the particles (charged particles). Thereby, energy is supplied to the particles (charged particles), and the particles (charged particles) are accelerated or decelerated.

<Extraction of particle beam from synchrotron 1>
A large number of particles orbiting the orbit in the synchrotron 1 shown in FIG. 1 are horizontal (parallel to the paper surface of FIG. 1: X-axis direction) or vertical direction (perpendicular to the paper surface of FIG. 1: Z-axis). Around the direction of vibration. This vibration is called betatron vibration, which can be controlled by the converging quadrupole electromagnet 5, the diverging quadrupole electromagnet 6, and the like. The S-axis direction is the direction in which the particle beam travels in the synchrotron 1 (the tangential direction of the beam circulating in the synchrotron 1), and the X-axis direction is perpendicular to the S-axis direction and is horizontal. This is the direction in which the synchrotron 1 extends.

  The particles in the synchrotron 1 are accelerated by the high-frequency acceleration cavity 3 and reach the maximum energy. Thereafter, the betatron amplitude is increased by applying an electric field by an RF-KO voltage to the particle beam by the RF-KO electrode 8. Then, a part of a large number of particles circulating in the synchrotron 1 is emitted toward the outgoing beam transport line 2 using the deflector electrode 9. An irradiation device (ports (13A, 13B) (see FIG. 10)) for irradiating the extracted particle beam to the irradiation target in the irradiation chamber is connected downstream of the outgoing beam transport line 2.

  Specifically, in order to take out the beam of the particle beam in the synchrotron 1 toward the outgoing beam transport line 2 outside the synchrotron 1, the beam of the particle beam distributed around the center of the tube of the synchrotron 1 An electric field by an RF-KO voltage is applied between the RF-KO electrode 8 in a direction perpendicular to the trajectory and in a horizontal direction. Thereby, the beam size of the particle beam is expanded in the horizontal direction. The emission of the particles is performed by utilizing the resonance of the betatron oscillation of the particles traveling on the orbit in the synchrotron 1.

  That is, the RF-KO electrode 8 is frequency-modulated and amplitude-modulated to resonate with betatron oscillation in a direction perpendicular to the orbit and in the horizontal direction (X-axis direction in FIG. 1) with respect to the beam traveling on the orbit of the synchrotron 1. An electric field by the RF-KO voltage thus applied is applied to widen the beam width of the particle beam traveling on the orbit. As a result, part of the particle beam is put into the two electrodes of the deflector electrode 9.

  When the beam enters the two electrodes of the deflector electrode 9, the particle beam is kicked outward by the electric field in the deflector electrode 9 and extracted toward the outgoing beam transport line 2. When the RF-KO voltage 8 is OFF, the increase in the particle beam size is stopped, so that the particle beam is not extracted from the deflector electrode 9, so that the irradiation can be stopped.

Next, a method for slowly extracting a beam of particle beams that circulate in the synchrotron 1 of a typical particle beam irradiation apparatus T to the outgoing beam transport line 2 will be described in detail.
FIG. 2 is a conceptual diagram showing the slow extraction of the particle beam using the third-order resonance of betatron oscillation in the lateral phase space and the perturbation of the hexapole magnetic field by the hexapole magnet 7 for generating the separatrix. The horizontal phase space in FIG. 2 is a direction (X axis direction) in which the horizontal axis is perpendicular to the beam traveling direction (S axis direction) in the horizontal direction, and the vertical axis is the displacement X in the X axis direction. It is an X ′ axis indicating a differential value (dX / dS) differentiated by the displacement S in the direction S.

  Due to the third-order resonance of betatron oscillation of a large number of particles circulating in the synchrotron 1 and the perturbation of the hexapole magnetic field by the hexapole electromagnet 7 for generating the separatrix for the large number of particles, the lateral phase space (horizontal axis shown in FIG. Is seen on the X axis and the vertical axis is the X ′ axis), the particle beam is divided into a stable region and a resonant region. Since the outside of the stable region drawn by the triangle in the beam of the particle beam becomes a resonance region, the betatron amplitude of the particles entering the resonance region increases and is extracted from the synchrotron 1 by the deflector electrode 9.

<< Particle Beam Irradiation Apparatus R of Embodiment >>
The particle beam irradiation apparatus R of the embodiment shown in FIG. 3 is an application of the present invention to a typical particle beam irradiation apparatus T. Drawing 3 is a figure which looked at particle beam irradiation device R of an embodiment from the upper part.
The basic configuration of the particle beam irradiation apparatus R of the embodiment is the same as that of the typical particle beam irradiation apparatus T shown in FIG. 1, and the same components are denoted by the same reference numerals, and detailed description thereof is omitted. To do.
The particle beam irradiation apparatus R includes control means (not shown) for controlling each component. The control means is composed of circuits such as a computer and various power supply circuits.

Hereinafter, a method of continuously emitting a beam from the synchrotron 1 by increasing the betatron amplitude of particles in the stable region using the RF-KO electrode 8 of the particle beam irradiation apparatus R shown in FIG. For example, see
4A and 4B show the longitudinal direction of particles (charged particles) bunched without acceleration / deceleration by a longitudinal high-frequency electric field in a direction parallel to the traveling direction of the particle beam in the synchrotron 1. FIG. the trajectory (the line with an arrow) on the direction phase space, <for gamma _t, gamma> each gamma represents the case of gamma _t. As described above, the lines with arrows in FIGS. 4A and 4B are the trajectories (orbits) that the particles in the synchrotron 1 follow.

4A and 4B, the horizontal axis φ represents the phase of the longitudinal high-frequency electric field generated by the high-frequency acceleration cavity 3, and the vertical axis P represents the momentum of the particles in the traveling direction. P _S is the movement amount of the reference in the direction of travel of particles circulating in the synchrotron 1 in synchronization with the vertical direction high frequency electric field of frequency and phase.
γ is a Lorentz factor proportional to the total energy of the particles, and is expressed by the following equation (1).

ここで、ｖは粒子の速度であり、ｃは光速度である。

Where v is the velocity of the particles and c is the speed of light.

Further, γ _t is a transition energy. The transition energy γ _t is expressed by the following equation (2) using a known α (momentum compaction factor).

For gamma <gamma _t, as shown in FIG. 4 (a), the particles circling in a predetermined steady state longitudinal high-frequency electric field is applied in the synchrotron 1 is a P = 0 φ = 0,2π, ..., −2π, −4π,... (Indicated as Beam in FIG. 4A) (this is called bunching). In FIG. 4 (a), when particles in the synchrotron 1 orbit around the orbit, the faster the particles, the longer the speed, the longer the trajectory (the higher the speed, the more the outer trajectory travels), Because the moving distance by speed is long, it returns around the orbit faster than the reference particle.

That is, <the case of γ _t, ΔvT> γ is a case where a relationship of 2Paiderutaaru. Δv is a speed component in which the speed of the particles orbiting the synchrotron 1 is faster than the speed of the reference particles, and Δr is an average of the distance variation toward the outside in the synchrotron 1 due to the higher speed. Is a period in which the reference particles return around the orbit in the synchrotron 1. Particles with a high speed go outside due to their speeds, but the moving distance (ΔvT) of the speed Δv that is faster than the fluctuation of the orbit (2πΔr) is longer, so they return around the orbit faster than the reference particles. Become.

On the other hand, from the state of gamma <gamma _t in FIG. 4 (a), exceeds the go when gamma _t by increasing the gamma, the state shown in Figure 4 (b).
In FIG. 4B, particles that circulate in a predetermined steady state when a longitudinal high-frequency electric field in the synchrotron 1 is applied are φ = π, 3π, 5π,..., −π, −3π. , −5π,... (In the same manner as FIG. 4A, this is called bunching).

In FIG. 4B, when the particles in the synchrotron 1 orbit along the trajectory, the faster the particles, the longer the speed, the longer the trajectory (the higher the speed, the more the outer trajectory advances), Unlike 4 (a), the moving distance due to the speed is short, so it returns around the orbit later than the reference particle.
That is, the case of gamma <gamma _t, is the case where the relation of ΔvT <2πΔr. That is, particles with a high speed go around the outer orbit because of their high speed, but the orbital distance (ΔvT) of the speed Δv that is faster than the fluctuation of the orbit (2πΔr) is shorter, so the orbit is slower than the reference particle. It will come back around.

FIG. 5 shows that the phase of the high-frequency electric field is shifted by 180 degrees in a very short time with respect to the beam bunched without acceleration / deceleration by the vertical high-frequency electric field when γ <γ _t in FIG. It is a figure showing the transition of the steady state of the beam on the vertical direction phase space in the case of.
For gamma <gamma _t, with respect to the beam of particles which are bunched orbiting at a predetermined steady state by longitudinal high-frequency electric field shown in FIG. 5 (a), the very short time in a high-frequency acceleration cavity 3 by the control means When a switching command for shifting the phase of the high-frequency electric field by 180 degrees is issued, the phase of the particle beam is shifted by 180 degrees in a very short time as shown in FIG. 5B as an initial state. Thereafter, the particle beam advances along the particle trajectory line (line with an arrow) in FIG. 5B, and the particle beam is in a steady state as shown in FIG. 5C.

FIG. 6 shows that the phase of the high-frequency electric field is shifted by 180 degrees in a very short time with respect to the beam bunched without acceleration / deceleration by the vertical high-frequency electric field when γ> γ _t in FIG. Represents the steady state transition of the beam on the longitudinal phase space.
In the case of γ> γ _t , the control means makes the high-frequency accelerating cavity 3 close to the high-frequency accelerating cavity 3 in a very short time with respect to the beam of particles bunched around the predetermined steady state by the longitudinal high-frequency electric field shown in FIG. When a switching command for shifting the phase of the high frequency electric field by 180 degrees is issued, the phase of the particle beam is shifted by 180 degrees in an extremely short time as shown in FIG. 6B as an initial state. Then, after the phase of the particle beam is shifted by 180 degrees, the particle beam advances along the particle trajectory line (line with an arrow) in FIG. 6B, and the particle beam is changed to FIG. 6C. It becomes the steady state shown.

The time for shifting the phase of the particle beam by 180 degrees by the longitudinal high-frequency electric field of the high-frequency accelerating cavity 3 is not particularly limited as long as the particle beam can be in the state shown in FIG. 5C and FIG.
Since the faster time can be more clearly shown in FIGS. 5C and 6C, the interval between the bunch beams shown in FIGS. 5A and 6A is less than the time (= t1). It is desirable to shift the phase by 180 degrees in a short time.
7, the state of polarization of the outgoing beam momentum distribution which occurs when emitting with tertiary resonance and sextupole magnetic field of betatron oscillation of the beam in the state shown in FIG. 5 (c) in the case of gamma <gamma _t Represents. FIG. 7A shows a case where chromaticity ξ <0, and FIG. 7B shows a case where chromaticity ξ> 0.

The chromaticity ξ is expressed by the following equation (3).
_{ΔQ = ξ × ΔP / P S} (3)
Here, P _S is the reference motion of the particles, [Delta] P is the deviation of the momentum from the reference motion of the particles, is ΔQ a shift of betatron frequency.
The chromaticity ξ of the ring (synchrotron 1) is adjusted by a chromaticity correcting hexapole electromagnet 12 (see FIG. 3).
Further, the stable circular area A of the particle beam of particles is expressed by the following formula (4).

ここで、Ｓ_ｘはセパラトリクス生成用六極電磁石７の六極磁場強度、ｋは係数、Ｑは、ベータトロン振動数、Ｑ_ｒｅｓは共鳴条件のベータトロン振動数であり、三次共鳴の場合はｎ／３（ｎは３の倍数を除く自然数）である。

Here, S _x is the hexapole magnetic field strength of the separatrix generating hexapole electromagnet 7, k is a coefficient, Q is the betatron frequency, Q _res is the betatron frequency of the resonance condition, and in the case of the third resonance, n / 3 (n is a natural number excluding multiples of 3).

  When the momentum of the particles circulating around the synchrotron 1 is changed by the longitudinal high-frequency electric field generated by the high-frequency accelerating cavity 3, when the chromaticity ξ of the synchrotron 1 is negative, as shown in FIG. The higher the momentum, the easier the particles exit from the stable orbiting region to the resonance region.

When the chromaticity ξ is negative, when ΔP is the maximum from the equation (4), the area A of the particle beam beam is the minimum, so the area of the resonance region is the maximum (see FIG. 2). For this reason, when ΔP is maximum, the particles that circulate around the synchrotron 1 are easily taken out of the stable region, and the momentum density of the outgoing beam is maximized.
Therefore, xi] is the case of the negative and ΔP ≧ P _S, the peak momentum density of the output beam to a maximum value of [Delta] P from Eq. (4) comes out. However, [Delta] P is, since the particles enters the reduction zone 7 arrowed line (a) (trajectory of particles) becomes difficult is taken out of the stable region, the case of [Delta] P ≧ P _S of FIG. 7 (a), A peak of the momentum density of the outgoing beam appears before the maximum value of ΔP of the line with an arrow.

In contrast, if ξ is negative and [Delta] P <P _S, stable annular zone area A of the particle beam of the peak momentum density of the output beam to a maximum value of [Delta] P from Eq. (4) (formula (4) is minimum ) Appears. However, if [Delta] P is, since the particles enters the reduction zone 7 arrowed line (a) (trajectory of particles) becomes difficult is taken out of the stable region, the [Delta] P <P _S of FIG. 7 (a), A peak of the momentum density of the outgoing beam appears before the maximum value of ΔP of the line with an arrow.

On the other hand, when the chromaticity ξ is positive, as shown in FIG. 7B, the particles are more likely to exit from the stable circulation region to the resonance region as the particle momentum is lower.
When chromaticity ξ is positive, from equation (4), when ΔP is minimum, the stable orbital area A of the particle beam is minimum and the resonance area is maximum (see FIG. 2). For this reason, when ΔP is minimum, particles circulating around the synchrotron 1 are easily taken out of the stable region, and the momentum density of the outgoing beam is maximized.

This is because the area of the stable circulation region in the lateral phase space changes due to the change in momentum due to the effect of chromaticity ξ (see Non-Patent Document 2).
Therefore, if ξ is positive and [Delta] P ≧ P _S, the formula (4) peak momentum density of the output beam in the minimum value of [Delta] P is out (minimum stable annular zone area A of the particle beam from the equation (4)) is since [Delta] P is particles it becomes difficult retrieved outside the stable region enters the increasing range of 7 arrowed line (b) (trajectory of the particle), the case of [Delta] P ≧ P _S in FIG. 7 (b), arrows A peak appears on the front side of the minimum value of ΔP of the attached line.

In contrast, if ξ is positive and [Delta] P <P _S, the peak momentum density of the emitted beam comes out at the minimum value of [Delta] P, [Delta] P is 7 arrowed line in (b) of (trajectory of the particles) because Once in increased area particles becomes difficult is taken out of the stable region, the case of [Delta] P <P _S in FIG. 7 (b), the peak momentum density of the emitted beam comes out before the minimum value of [Delta] P of the arrowed line .
Incidentally, gamma> In each case gamma _t, as in the case of gamma <gamma _t shown in FIG. 7, polarization of the emission beam momentum distribution occurs.

  In FIG. 8, as shown in FIGS. 7 (a) and 7 (b), the momentum distribution of the exit beam is polarized (see the two peaks of the exit beam momentum density in FIGS. 7 (a) and 7 (b)). FIG. 6 is a diagram showing the beam emission angle dipole generation that occurs in the case of the above in a horizontal phase space. In FIG. 8, the horizontal phase space is a differential value X ′ (dX obtained by differentiating the horizontal position coordinate X by the horizontal axis and the horizontal position coordinate X by the position S in the beam traveling direction by the vertical axis. / DS). Further, the deflector electrode 9 in FIG. 8 is illustrated on the assumption that the beam travels from the front side to the back side in FIG.

  Bipolarization of the beam exit angle (see the two triangles in FIG. 8) is performed within the synchrotron 1 for particles of different momentum (see the two peaks of the exit beam momentum density of each of FIGS. 7 (a) and (b)). The difference between the equilibrium trajectory (dispersion) traveling in the synchrotron 1 caused by the difference in deflection angle of the deflection electromagnet 4 and the difference in the area of the stable circulation region in the lateral phase space caused by the effect of chromaticity ξ occurs. A difference in the area of the stable circulation area in the lateral phase space leads to a change in the position of the center of gravity of the stable circulation area of the two triangles shown in FIG.

  Next, the beam b (b1, b2) in which the momentum and the beam emission angle X ′ are polarized in the synchrotron 1 described with reference to FIGS. A configuration in which the deflection angle difference of the deflection electromagnet 10 provided in the beam transport line 2 and the beams polarized by the three-plate electrode 11 are separated from each other will be described.

FIG. 9 shows that the beam having the polarized momentum and the beam exit angle X ′ is separated from the first and second beams by the deflection angle difference of the deflecting electromagnet 10 provided in the exit beam transport line 2 and the triple plate electrode 11. It is the A section enlarged view of FIG. Note that FIG. 9 illustrates a case where a beam of charged particles (for example, C ⁶⁺ ) having positive electricity is extracted.

  An outgoing beam transport line 2 connected to the synchrotron 1 via a deflector electrode 9 deflects a beam b (first beam b1, second beam b2) having a polarized beam outgoing angle and momentum to 2 A deflecting electromagnet 10 is provided to greatly separate the difference between the two beam exit angles and the distance between the beams. Further, the beam b (the first beam b1 and the second beam b2) whose beam exit angle difference and inter-beam distance are greatly separated by the deflection electromagnet 10 is further separated to the outgoing beam transport line 2 downstream of the deflection electromagnet 10. A triple plate electrode 11 is provided.

In FIG. 9, since a particle beam having a positive charge is taken out, a negative voltage is applied to the first electrode 11a and the second electrode 11b of the three-plate electrode 11 by the control means. The third electrode 11c of the triple plate electrode 11 is a ground.
Unlike the case of FIG. 9, when a particle beam having a negative charge is taken out, a positive voltage is applied to the first electrode 11a and the second electrode 11b of the triple plate electrode 11 by the control means. Each will be applied. The third electrode 11c of the triple plate electrode 11 is a ground.

Then, downstream of the triple plate electrode 11 of the outgoing beam transport line 2, the first transport line 2 </ b> A and the second transport line for traveling the first beam b <b> 1 and the second beam b <b> 2 whose beam distance is increased, respectively. 2B is connected.
With the above configuration, extraction of the beam b (b1, b2) through the outgoing beam transport line 2 is performed as follows.

  The beam b (b1, b2) having the above-described bipolar beam emission angle and momentum is extracted from the synchrotron 1 by the voltage applied by the deflector electrode 9. The first beam b1 and the second beam are controlled by the deflection angle difference of the deflection electromagnet 10 controlled by the control means (the angle when the beam b exits the deflection electromagnet 10 with respect to the angle when the beam b enters the deflection electromagnet 10). The b2 emission angle difference and the inter-beam distance are widened.

  Thereafter, the first beam b1 having a positive charge passes between the first electrode 11a to which the negative voltage of the three-plate electrode 11 downstream of the deflecting electromagnet 10 is applied and the third electrode 11c on the ground, One beam b1 is drawn toward the first electrode 11a and proceeds in the first transport line 2A as indicated by an arrow. At the same time, the second beam b2 having a positive charge passes between the second electrode 11b to which the negative voltage of the three-plate electrode 11 downstream of the deflecting electromagnet 10 is applied and the third electrode 11c on the ground. The two beams b2 are drawn toward the second electrode 11b and travel in the second transport line 2B as indicated by arrows.

  The greater the distance between the first beam b1 and the second beam b2, the more the first beam b1 and the second beam b2 can be divided into the two transport lines (2A, 2B) without beam loss. Therefore, one beam that circulates in the synchrotron 1 is simultaneously extracted as two beams of the first beam b1 and the second beam b2 by the deflection electromagnet 10 and the three-plate electrode 11 without beam loss.

Next, a method of using the first beam b1 extracted from the first transport line 2A and the second beam b2 extracted from the second transport line 2B will be described.
FIG. 10 is a diagram illustrating a state in which the patient (irradiation target) P is irradiated with the first beam b1 and the second beam b2.
In the irradiation chamber 15, a first port 13A connected to the first transport line 2A is arranged in the vertical direction so that the first beam b1 can be irradiated in the vertical direction toward the irradiation target on the bed 14. . The irradiation chamber 15 is provided with a second port 13B connected to the second transport line 2B in the horizontal direction so that the second beam b2 can be irradiated toward the irradiation target on the bed 14 in the horizontal direction. ing.

  When the patient (irradiation target) P lies on the bed 14, the first beam b1 is irradiated downward from the first port 13A toward the affected part P1 of the patient (irradiation target) P on the bed 14, and the first The second beam b2 is irradiated in the horizontal direction toward the affected part P1 of the patient (irradiation target) P from the 2-port 13B.

  Conventionally, when two beams are irradiated simultaneously, two synchrotrons are required. According to this configuration, one synchrotron 1 (see FIG. 3) is irradiated simultaneously to one irradiation object. it can. Since one synchrotron 1 irradiates with two beams (b1, b2) at the same time, it is possible to start irradiation of two beams at the same time and simultaneously stop irradiation of the two beams (b1, b2) being irradiated. it can. Therefore, it is possible to irradiate the two beams (b1, b2) in synchronization with the respiration of the patient (irradiation target) P or stop the irradiation of the two beams (b1, b2) being irradiated.

In the example of FIG. 10, the case where the two beams (b1, b2) are irradiated from the vertical direction and the horizontal direction is illustrated, but it is needless to say that the vertical direction and the horizontal direction are not necessarily required.
Further, unlike the example of FIG. 10, it is of course possible to irradiate different patients (irradiation targets) P with the first beam b1 and the second beam b2, respectively.
In addition, the irradiation method of the two first beams b1 and the second beam b2 is not limited to the exemplified one, and various applications are possible.

According to the above-described embodiment, it is possible to emit a divided beam from one synchrotron 1 to two transport lines (2A, 2B) at the same time without beam loss, which is impossible with the conventional slow extraction method.
The principle of the present invention is that a beam bunched by a longitudinal high-frequency electric field parallel to the traveling direction of the beam in beam extraction using third-order resonance of betatron oscillation and perturbation of a hexapole magnetic field, which is often used for a slow extraction method. On the other hand, the momentum distribution of the outgoing beam entering the deflector electrode 9 is dipolarized through the chromaticity ξ of the synchrotron 1 by shifting the phase of the longitudinal high-frequency electric field by 180 degrees in a very short time. .

Due to the effect of the chromaticity ξ of the synchrotron 1, in addition to the bipolarization of the momentum distribution, a difference can also be given to the exit angles of the respective polarized beams.
The beam b having the polarized momentum and the emission angle can be divided into two beams (b1, b2) on the emission beam transport line 2 by a deflection angle difference by the deflection electromagnet 10 and the like. Further, if the three-plate electrode 11 or the like is used, it is possible to easily separate the beams (b1, b2) even larger without any beam loss. As the distance between the beams (b1, b2) separated into two is larger, the beam can be easily supplied to the separate beam transport lines (2A, 2B) simultaneously without any beam loss.

As described above, the split beam can be emitted from the single synchrotron 1 to the two transport lines (2A, 2B) simultaneously without any beam loss, so that the synchrotron 1 per unit time can be matched to the beam usage requirements. Use efficiency can be increased. Since two ports (13A, 13B) can be output from one synchrotron 1, the beam utilization efficiency is doubled.
In addition, more beam usage requirements can be answered within the same time.

  In the above-described embodiment, the case where the beam b (the first beam b1 and the second beam b2) having a polarized beam emission angle is separated using the deflecting electromagnet 10 and the three-plate electrode 11 is illustrated. Only the three-plate electrode 11 may be used. The triple plate electrode 11 has a simple structure and is easy to control.

Further, the angle difference between the first beam b1 and the second beam b2 may be given by using only the deflection electromagnet 10 and changing the excitation amount of the deflection electromagnet 10 without using the three-plate electrode 11.
As described above, it is more preferable to use the deflecting electromagnet 10 and the three-plate electrode 11 because the beams having the polarized beam emission angle can be separated at a short distance.

  In the above-described embodiment, the slow extraction method by the perturbation of the third-order resonance of the betatron oscillation and the hexapole magnetic field is used, but a combination of the secondary resonance and the octupole magnetic field or the combination of the fourth-order resonance and the octupole magnetic field may be used. . Further, the present invention is not limited to the slow extraction using the RF-KO electrode. For example, a beam intensity control device (beam control device) using betatron frequency control by changing a quadrupole electromagnet excitation current may be used.

  Further, in the beam intensity control device (beam control device) using the betatron frequency control method by changing the quadrupole electromagnet excitation current, the excitation current may be changed by controlling the power supply of the quadrupole electromagnet. . A plurality of quadrupole electromagnets are generally provided in the synchrotron, but the effect can also be obtained by controlling at least one of them.

1 Synchrotron 2 Outgoing beam transport line (beam transport line)
2A 1st transport line (beam transport line)
2B Second transport line (beam transport line)
3 High-frequency acceleration cavity 10 Bending electromagnet (beam splitting means)
11 Three-plate electrode (beam splitting means)
11a First electrode (first electrode)
11b Second electrode (second electrode)
11c Third electrode (third electrode)
13A First port 13B Second port P Patient (irradiation target)
R Particle beam irradiation device (beam extraction device)

Claims (14)

A synchrotron in which a particle beam circulates while oscillating with a betatron, a high-frequency acceleration cavity provided in the synchrotron for accelerating or decelerating the particle beam by applying a vertical high-frequency electric field parallel to the traveling direction thereof, and the synchrotron A beam extraction device comprising a beam transport line connected to a tron and transported by a particle beam emitted from the synchrotron,
Controlling the phase of the longitudinal high-frequency electric field by the high-frequency accelerating cavity 180 degrees with respect to the particle beam that circulates in a predetermined steady state in the synchrotron, and the momentum of the particle beam emitted from the synchrotron A beam extraction apparatus comprising control means for dipoleizing the emission angle. 2. The beam according to claim 1, wherein the control unit controls the phase of a longitudinal high-frequency electric field generated by the high-frequency accelerating cavity to be shifted by 180 degrees within a time between bunch beams in the betatron oscillation. Output device. The beam transport line includes beam splitting means that widens an exit angle difference and an inter-beam distance between the two emitted particle beams and bisects the two particle beams. 3. The beam extraction apparatus according to 2. As the beam splitting means, a three-plate electrode through which the two emitted particle beams pass between the first electrode and the third electrode and between the second electrode and the third electrode, respectively. Have
When the particles of the particle beam have a positive charge, the first electrode and the second electrode are applied with a lower voltage than the third electrode by the control means, while the negative charge is applied to the first electrode and the second electrode. The beam emitting apparatus according to claim 3, wherein a voltage higher than that of the third electrode is applied to the first electrode and the second electrode by the control means.   4. A deflecting electromagnet that imparts a deflection angle difference to the two particle beams by the amount of excitation when the two emitted particle beams pass as the beam splitting means. Item 5. The beam extraction device according to Item 4. A first port for irradiating an irradiation target with one of the two particle beams connected to the beam transport line and having an emission angle difference and an inter-beam distance widened by the beam splitting means;
And a second port for irradiating the irradiation target or an irradiation target different from the irradiation target with the other one of the two particle beams connected to the beam transport line. The beam extraction apparatus according to any one of claims 3 to 5. The first port irradiates the irradiation target with one of the two particle beams from a vertical direction,
The beam emitting apparatus according to claim 6, wherein the second port irradiates the irradiation target with the other of the two particle beams from a horizontal direction. A synchrotron in which a particle beam circulates while oscillating with a betatron; a high-frequency acceleration cavity provided in the synchrotron for accelerating or decelerating the particle beam by applying a vertical high-frequency electric field parallel to the traveling direction thereof; A beam extraction apparatus control method comprising a beam transport line connected to a tron and transported by a particle beam emitted from the synchrotron, and a control means,
The high-frequency acceleration cavity applies the longitudinal high-frequency electric field to the particle beam to circulate the particle beam in a predetermined steady state,
The control means includes
A method of controlling a beam extraction apparatus, wherein the phase of a longitudinal high-frequency electric field by the high-frequency acceleration cavity is controlled to be shifted by 180 degrees, and the momentum and the emission angle of the particle beam in the synchrotron are bipolarized. The beam according to claim 8, wherein the control means controls the phase of a longitudinal high-frequency electric field generated by the high-frequency acceleration cavity to be shifted by 180 degrees within a time between bunch beams in the betatron oscillation. A method for controlling the emission device. The beam transport line has beam splitting means;
10. The beam according to claim 8, wherein the beam splitting unit widens an exit angle difference and an inter-beam distance between the two emitted particle beams, and divides the two particle beams into two. A method for controlling the emission device. In the beam emitting device, as the beam splitting means, the two particle beams to be emitted are respectively between the first electrode and the third electrode and between the second electrode and the third electrode. With a three-plate electrode that passes through,
When the particles of the particle beam have a positive charge, the control means applies a lower charge to the first electrode and the second electrode than the third electrode while applying a negative charge. 11. The method of controlling a beam emitting device according to claim 10, wherein the control means applies a voltage higher than that of the third electrode to the first electrode and the second electrode. 11. . The beam emitting device has a deflection electromagnet as the beam splitting means,
The beam according to claim 10 or 11, wherein the deflecting electromagnet imparts a deflection angle difference to the two particle beams according to the excitation amount when the two emitted particle beams pass through. A method for controlling the emission device. The beam extraction device includes a first port and a second port connected to the beam transport line,
The first port irradiates an irradiation target with one of the two particle beams whose emission angle difference and inter-beam distance are expanded by the beam splitting means,
The said 2nd port irradiates the irradiation object different from the said irradiation object or the said irradiation object with the other of the said two particle beams. Any one of Claims 10-12 characterized by the above-mentioned. A control method of the beam extraction device described. The first port irradiates the irradiation target with one of the two particle beams from a vertical direction,
The method of controlling a beam emitting device according to claim 13, wherein the second port irradiates the irradiation target with the other of the two particle beams from the horizontal direction.

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