JP3047830B2 - Charged particle beam extraction method, circular accelerator, and circular accelerator system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charged particle beam.
The charged particle beam extraction method for exiting from the circular accelerator or irradiation device, and a circular accelerator which emits a charged particle beam, and to circular accelerator system having a circular accelerator and an irradiation device for emitting a charged particle beam.

[0002]

2. Description of the Related Art In a conventional circular accelerator, a charged particle beam such as an electron or an ion is accelerated and orbited, and the charged particle beam emitted from the orbit is transported by a transport system for use in a physical experiment or medical treatment. I've been. In the conventional charged particle beam emission, AIP Conference Proceedings No. 127 (1983) (AIP Conference
The resonance of the betatron oscillation of the beam has been used as discussed in Proceedings, pages 53-61.

[0003] The resonance of betatron oscillation is the following phenomenon. The charged particles orbit while oscillating left and right or up and down, and this oscillation is called betatron oscillation. The frequency per revolution of the orbit of the betatron oscillation is called tune,
The tune can be controlled by a bending electromagnet or a quadrupole electromagnet provided on the orbit. In the above conventional example, when the tune is brought close to an integer ± 整数 and the resonance generating six-pole electromagnet provided on the orbit is excited, the orbiting charged particles have an amplitude greater than a certain boundary. The betatron oscillation amplitude of charged particles increases sharply. This phenomenon is called resonance of betatron oscillation, and the boundary is called a stability limit. The magnitude of the betatron oscillation amplitude at the stability limit of the resonance depends on the deviation from the tune integer ± １ ／, and the smaller the deviation is, the smaller. Therefore, in the prior art, the tune is gradually approached to an integer ± １ ／, that is, the magnitude of the stability limit is gradually reduced, and resonance occurs first in charged particles having a large betatron oscillation amplitude among the orbiting charged particles. Thereafter, resonance is sequentially generated in the charged particles having a small vibration amplitude to gradually emit a charged particle beam.

[0004]

In the above-mentioned prior art, the common technique is used.
Charged particles by adjusting the size of the stability limit of the sound
Controls beam emission, ensuring reliable charging in a short time
The emission of the particle beam could not be stopped.

An object of the present invention is to provide a charged particle beam extraction method, a circular accelerator, and a circular accelerator system that can reliably stop the emission of a charged particle beam in a short time.

[0006]

[0007]

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

A feature of the present invention to achieve the above object is that a charged particle beam is emitted from a circular accelerator by applying a high-frequency electric or magnetic field or an electromagnetic field to a circulating charged particle beam. From beam system
Based on the stop signal output is to stop the extraction of the charged particle beam from O Ri circular accelerator to stop the application of the high frequency electric or magnetic fields, or electromagnetic fields.

The application of a high-frequency electric or magnetic field or an electromagnetic field can be stopped in a few μs .
By stopping the extraction of the charged particle beam from the circular accelerator by stopping the application of high frequency electric or magnetic fields, or electromagnetic fields based on the stop signal et output beam using
The emission of the charged particle beam is requested from the system
In a short time, the emission of the charged particle beam can be stopped reliably.

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a general outline of the present invention, which is a circular accelerator that emits an accelerated beam. The circular accelerator is composed of a bending electromagnet 3, a quadrupole electromagnet 5, 7, a resonance excitation electromagnet 9,
It is composed of an emission deflector 13 and the like. The resonance excitation electromagnet 9 is an electromagnet that generates a multipole magnetic field for generating resonance. In the coordinate system, the beam circling direction is s, the horizontal direction is x, and the vertical direction is y. The beam circulates while vibrating around the design trajectory 1 which is a circling trajectory. The betatron oscillation amplitude differs for each particle constituting the beam, and particles having a large amplitude to small particles are mixed. Therefore, the beam diameter during orbit of the design orbit 1 is determined by the maximum value of the betatron oscillation amplitude. The frequency of one orbit of the betatron oscillation per orbit is called tune, and the horizontal tune is νx and the vertical tune is νy. Horizontal,
The values of the vertical tunes νx and νy can be adjusted by the excitation amounts of the converging quadrupole electromagnet 5 and the diverging quadrupole electromagnet 7.

The quadrupole electromagnets 5 and 7 are adjusted to set the horizontal tune νx or the vertical tune νy to an integer ± p / q.
(Reduced fraction), and when the electromagnet 9 for resonance excitation is excited, the amplitude of particles having a betatron oscillation amplitude larger than the stability limit increases due to resonance. The resonance at this time is called a q-order resonance. Hereinafter, a case where a beam is extracted from the horizontal direction will be described by taking a third-order resonance as an example.

The quadrupole electromagnets 5 and 7 are adjusted so that the horizontal tune νx approaches an integer ± １ ／ and the resonance excitation electromagnet 9 (in the case of the tertiary resonance, a six-pole electromagnet is used), the vibration amplitude is reduced. Third-order resonance is excited by large particles. The position in the s direction at which the output deflector 13 of FIG. 1 is installed is so, and x and dx for each round of the beam at s = so
FIG. 2 shows the relationship (phase space) of / ds. The dashed line in FIG. 2 indicates the stability limit in the phase space. Particles outside the stability limit, that is, particles whose betatron oscillation amplitude is larger than the stability limit, have a sharp increase in oscillation amplitude every round due to resonance. The number given to the particle exceeding the stability limit in FIG. 2 indicates the number of turns. The stability limit becomes smaller as the deviation of the tune vx from the integer ± 1/3 is smaller and the strength of the multipole magnetic field for generating resonance is larger. Reference numeral 20 in FIG. 2 (indicated by 20i on the inside and 20o on the outside) indicates the electrode of the deflector 13 for emission shown in FIG. 1, and particles that collide with the electrode 20 are lost and enter the region between the electrodes 20. The particles are emitted out of the circular accelerator. The orbit gradient dx / ds of the emitted particles at the position of the exit deflector is substantially equal to A as can be seen from FIG. A is set to, for example, an angle formed between the orbit and the deflector for emission. The diameter of the beam emitted from the circular accelerator is determined by the beam diameter entering the deflector for emission. In the case of tertiary resonance, the displacement increase amount of the particle exceeding the stability limit in every three laps (in the case of q-order resonance, the displacement increase amount in q laps) is called a turn separation Ts.
Ts increases as the distance from the stability limit increases, and decreases as the stability limit decreases. Therefore, when the stability limit is reduced by changing the tune to emit particles having a small betatron oscillation amplitude as in the prior art, the turn separation Ts also decreases. Can't get over the beam and hits the wall and the beam disappears. Assuming that the thickness of the exit deflector wall is Td, the beam exit efficiency is (Ts-Td) / Ts as a primary evaluation. Therefore, the smaller the stability limit, the lower the emission efficiency.
In general, as the betatron oscillation amplitude is smaller, the distribution of the circulating beam is larger, so that the emission efficiency is lower. Thus, in the present invention, charged particles within the stability limit are moved out of the stability limit by increasing the betatron oscillation amplitude. As a result, even particles having a small betatron oscillation amplitude that cannot be extracted unless the stability limit is reduced can be emitted while maintaining a certain degree of turn separation Ts. Therefore, it is possible to provide a circular accelerator having a high emission efficiency or a large emission current, and a beam emission method and an emission device.

Next, the operation of keeping the stability limit substantially constant will be described. As described above, the stability limit can be controlled by adjusting the amount of excitation of the tune and the multipole electromagnet for generating resonance. FIG. 2 shows the trajectory of the representative particle in the phase space, and other particles move along the trajectory in the figure. That is, many particles exist between the trajectories in FIG. The beam emitted from the beam having the increased vibration amplitude is the beam incident between the two electrodes 20i and 20o of the output deflector. Therefore, if the stability limit is kept constant, not only the gradient of the output beam, that is, the output angle, can be kept constant, but also the output beam diameter and the output position can be kept constant. As described above, when the emission position is constant and the turn separation Ts is constant, the emission efficiency (Ts−
Td) / Ts also becomes constant. The gradient of the output beam and the turn separation Ts can be changed by selecting a tune when setting the stability limit before the output, that is, by adjusting the excitation amount of the quadrupole electromagnet and the excitation amount of the resonance excitation electromagnet. The output efficiency is constant and large.

Next, the emittance representing the beam characteristics will be described. The emittance of the beam indicates the area occupied by the beam in the phase space, and is proportional to the product of the beam size and the distribution width of the orbit gradient. For example, the emittance of a beam circling within the stability limit shown in the phase space of FIG.
It is equal to the area enclosed by the broken line in FIG. On the other hand, the phase space near the exit deflector electrode 20 of the exit beam is shown in FIG.
Shown in The emittance of the output beam is equal to the product of the width ΔX of the beam entering between the deflector electrodes 20i and 20o and the change width ΔP of the orbit gradient. When resonance is generated with the above-mentioned stability limit being substantially constant, the variation width ΔP of the orbital gradient shown in FIG. 6 can be suppressed to a negligible level, and the emittance of the output beam can be kept constant and small. it can.

Next, the means for increasing the betatron oscillation amplitude of particles within the stability limit of the resonance will be described. Means for increasing the vibration amplitude of particles within the stability limit are roughly classified into the three methods described in Means for Solving the Problems.

The magnetic field of (1) is applied in the vertical direction (y direction) when the emitting surface is a horizontal surface, and is applied in the horizontal direction (x direction) when the emitting surface is a vertical surface. This means that although the change in the orbital gradient for each revolution is small, the orbital gradient of the beam is changed by the magnetic field, and the accumulation of the beam increases the oscillation amplitude of the beam.
The time change of the magnetic field may be regular or irregular. As a device for applying a magnetic field to the beam, an electromagnet, a parallel linear electrode, a plate electrode, an arc electrode, or the like can be used. By passing a time-varying current through these devices, a time-varying magnetic field is applied to the beam and the betatron oscillation amplitude increases.

The electric field of (2) is applied in the circumferential direction of the beam, that is, in the s direction, or in the horizontal direction (x direction) when the emitting surface is a horizontal surface, and in the vertical direction when the emitting surface is a vertical surface. (Y direction). When an electric field is applied in the s direction, the energy of the beam changes. When the energy of the beam changes, the radius of curvature of the trajectory in the bending electromagnet portion changes, so that the center trajectory position of the betatron oscillation changes, and as a result, the betatron oscillation amplitude changes. When an electric field is applied in the x direction or the y direction, similarly to the magnetic field of (1), a transverse force is applied to the beam to change the orbit gradient,
Increase the betatron oscillation amplitude. The time change of the electric field may be regular or irregular. The electric field can be applied by applying a time-varying current to parallel linear, flat, or arc electrodes, by applying a time-varying voltage to a button or plate electrode, or by applying a high-frequency voltage to a high-frequency cavity. Is applied. Therefore, in the case of an electric field, the electric field can be decomposed into the s direction and the x direction or the y direction regardless of the direction of application, so that the above two effects occur and the amplitude of the betatron oscillation can be increased.

When a time-varying signal is applied to an electrode or a cavity, a magnetic field is also generated at the same time as an electric field. Therefore, when the effect of the electric field is mainly used, the effect of the magnetic field is superimposed, and the effect of the magnetic field is mainly used. The effect of the electric field is also superimposed. In either case, since the amplitude of the betatron oscillation increases, a beam can be emitted as in the case of a single case.

When an electric field or a magnetic field that changes with time perpendicular to the beam traveling direction is applied as described above to increase the betatron oscillation amplitude of the beam, the frequency component is synchronized with the betatron oscillation. It is desirable to include. This is because when an electromagnetic field including a frequency component synchronized with the betatron oscillation is applied to the beam, the electromagnetic field is synchronized with the betatron oscillation, and the amplitude of the betatron oscillation can be efficiently increased. The frequency of the electromagnetic field synchronized with the betatron oscillation is the fractional part of the tune, or 1
It can be obtained from the product of the value obtained by subtracting the decimal part of the tune from and the orbital frequency. A multipole electromagnet is required to generate resonance when the beam is emitted, but when the multipole electromagnet is excited, the tune of the beam changes depending on the betatron oscillation amplitude. That is, the tune of the beam having a large betatron oscillation amplitude is different from the tune of the beam having a small betatron oscillation amplitude. Also,
Since the betatron oscillation amplitude of the beam is continuously distributed from a large value to infinity, the tune of the beam is also continuously distributed. Therefore, if a plurality of frequency components are provided in an externally applied electromagnetic field and the values are set to values close to the tune of the beam, the betatron oscillation amplitude can be efficiently increased. In particular, since the tune of the beam is continuously distributed as described above, it is desirable to use an electromagnetic field containing noise having continuous frequency components and containing frequency components synchronized with betatron oscillation. However, even at a single frequency, it is possible to increase the betatron oscillation amplitude by using an electromagnetic field having a frequency approximately equal to the tune of the distributed beam. In this case, a larger electromagnetic field strength is required as compared with the above high frequency having a plurality of frequency components.

Another effect when the above-mentioned noise is used in an electromagnetic field applied from the outside will be described. When ripples are included in the current of the electromagnet of the accelerator, the tune changes with time in synchronization with this, and the magnitude of the stability limit in FIG. 5 changes. Therefore, in the conventional emission method in which the stability limit is gradually reduced as shown in FIG. 5, since the magnitude of the stability limit becomes smaller while oscillating in synchronization with the current ripple, the beam may be emitted intermittently. high. On the other hand, when an electromagnetic field whose intensity changes randomly is applied to the beam, the beam spreads in the phase space shown in FIG. 5 and the betatron oscillation amplitude increases. At this time, if the amount of change in the amplitude of the betatron oscillation due to noise is ΔAn, the time is t, and the constant is D,
(ΔAn ² ) = Dt. Here, (ΔAn ² ) indicates the average value of the change in vibration amplitude of the beam for all particles. From this, the time derivative of the vibration amplitude change of the beam is 0.5 (D /
t) ⁰ · ⁵ next, although the large rate of increase within a short period of time, the rate of increase in long-term decreases. Therefore, even if the oscillation amplitude of the beam is slowly increased over a long period of time, the increase width of the betatron oscillation amplitude can be larger than the change width of the stability limit within a time period of about the ripple period of the electromagnet current.
The beam can be emitted with little influence from the power supply ripple.

In the method (3), particles other than the beam circling the circular accelerator are introduced into the circular accelerator and collide with the circular beam. As a result of the collision-induced scattering, the orbital gradient changes and the betatron oscillation amplitude of the orbiting beam increases.
The particles to be collided may be neutral particles or charged particles. The particles to be collided may be injected as a gas, or may be provided as a thin film in the accelerator and collide with the beam.

Finally, the operation of the means for controlling the rate of increase in the betatron oscillation amplitude will be described. The emission current can be adjusted by controlling the rate of increase of the betatron oscillation amplitude of particles within the stability limit. When the betatron oscillation amplitude is increased using the above-mentioned electromagnetic field (1) or (2), the intensity of an electric field or a magnetic field is changed by changing the signal strength applied to an electrode or the like. When the emission current is increased and the beam is emitted quickly, the intensity of the applied signal is increased. When the emission current is reduced and the beam is emitted slowly, the intensity of the applied signal is decreased. By using the same method, the emission current can be temporally changed in the emission process. Furthermore, when keeping the emission current constant,
The rate of increase is adjusted according to the beam distribution during orbit.

The amount of the beam emitted per unit time is
At that time, it is roughly proportional to the number of particles of the beam circling the accelerator. Since the number of particles of the orbital beam decreases with the emission, in order to emit the beam at a constant rate, it is necessary to increase the speed of increase of the betatron oscillation amplitude by increasing the electromagnetic field intensity during the emission. In this way, since the amount of the emission current can be controlled by the increasing speed of the betatron oscillation amplitude, the start and stop of the emission can be controlled by the start and stop of the application of the electromagnetic field. Therefore, not only a predetermined operation plan, but also beam emission / stop at the request of the beam user side is possible, and further, emergency stop of beam emission can be performed.

In the case of using the method (3), by adjusting the number of other particles to be put in the circular accelerator, the adjustment can be performed in the same manner as in the case where the betatron oscillation amplitude is increased by the electromagnetic field.

In addition to the above-described adjustment of the emission current, a method of adjusting the emission current by changing the magnitude of the stability limit by adjusting the tuning or changing the excitation amount of the resonance excitation electromagnet may be added. The emission current can be controlled in the same manner as described above.

The gradient of the output beam and the turn separation Ts are changed by selecting a tune when setting the stability limit before the output, that is, by adjusting the excitation amount of the quadrupole electromagnet and the excitation amount of the resonance excitation electromagnet. be able to.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention in which protons having an energy of about 20 MeV
It is a figure which shows the device structure of the circular accelerator which emits after accelerating to eV. The circular accelerator is an injector 1 for inputting a beam 17 from a pre-stage accelerator 16 via a beam transport system 18.
5, a high-frequency accelerating cavity 8 for imparting energy to the incident beam 17, a bending electromagnet for bending the beam trajectory 3, a quadrupole electromagnet 5, 7 for controlling the betatron oscillation of the beam, and 6 for exciting resonance at the time of emission. A pole electromagnet 9, a high frequency applying device 14 for increasing the betatron oscillation amplitude of particles within the stability limit of resonance by applying a time-varying magnetic field and electric field to the beam, and beam transport for emission of particles having an increased betatron oscillation amplitude It is composed of an output deflector 13 for output to the system. Among these devices, the six-pole electromagnet 9, the high-frequency application device 14, and the deflector 13 are used only in the process of emitting the beam after accelerating the beam to the target energy.

The trajectory of the beam incident from the injector 15 is bent by the bending electromagnet 3 in the course of orbit. Also, 4
In the polar electromagnet, the trajectory gradient can be changed by a force proportional to the deviation from the design trajectory 1. The quadrupole electromagnet 5 changes the orbit gradient so as to converge the beam in the horizontal direction and diverge the beam in the vertical direction, and the quadrupole electromagnet 7 modulates the orbit gradient so as to diverge the beam in the horizontal direction and converge the beam in the vertical direction. It works to change. By the action of these quadrupole electromagnets, the beam circulates around the design trajectory 1 with betatron oscillation, and the frequency of the betatron oscillation depends on the excitation amount of the converging quadrupole electromagnet 5 and the diverging quadrupole electromagnet 7. Can control. In order to stably circulate the beam during the injection and acceleration processes, the betatron frequency (tune) for one revolution of the accelerator must be set to a value that does not cause resonance, especially, away from the tune that causes low-order resonance. Need to be kept. In this embodiment, the quadrupole electromagnets 5 and 7 are adjusted so that the horizontal tune νx is 1.73 and the vertical tune νy is 1.23. In this state, the beam circulates stably in the accelerator, and energy is given from the high-frequency acceleration cavity 8 in the process. The frequency f of the high frequency applied to the high frequency accelerating cavity is set to an integral multiple (n times) of the frequency at which the beam circulates. The beam circulates in the circling direction, that is, in the s direction, in n lumps (bunch shape) so as to synchronize with the high frequency. While applying energy to the beam from the high-frequency accelerating cavity 8, the magnetic field intensity is increased while maintaining the magnetic field intensity ratio between the bending electromagnet 3 and the quadrupole electromagnets 5, 7 constant.
Then, in the curved portion of the bending electromagnet, an increase in centrifugal force due to an increase in the beam energy and an increase in the centripetal force due to an increase in the amount of excitation of the bending electromagnet balance and orbit around the same orbit. FIG. 3 shows a trajectory in the phase space (x, dx / ds) at the emission position s = so in the s direction in this process. The trajectory in the phase space in FIG. 3 appears to have many similar ellipses with different diameters, but the diameter of the ellipse corresponds to the magnitude of the betatron oscillation amplitude, and the diameter of the ellipse is small. The smaller the betatron oscillation amplitude is, the smaller the betatron oscillation amplitude is.

FIG. 4 shows an operation method in the process of emitting light after accelerating to the target energy. First, as shown in FIG. 4A, the application of energy to the beam from the high-frequency acceleration cavity 8 is stopped. Thereby, the beam changes from a bunch shape to a continuous beam. Next, in FIG. 4 (2), the power of the converging quadrupole electromagnet 5 and the power of the diverging quadrupole electromagnet 7 are adjusted to set the horizontal tune νx to 1.67. Next, as shown in FIG. 4C, a current for resonance excitation is supplied to the hexapole electromagnet 9. The current flowing through the hexapole electromagnet 9 is set to a value such that particles having a large betatron oscillation amplitude of the circulating beam fall within the stability limit, and the value is obtained in advance by calculation or by repeating the emission operation. At this time, the phase space at the position of the output deflector 13 is as shown in FIG. 5, and the trajectory in the phase space is triangular. Next, as shown in FIG. 4D, an irregular time-varying signal is applied to the beam by the high-frequency application device 14 of the circular accelerator in FIG. FIG.
2 shows the configuration of the high frequency applying device 14. Electrode 2 of FIG.
Numerals 5 and 26 are rod-shaped electrodes which are arranged so as to face each other in the horizontal direction, and a magnetic field and an electric field in the direction shown in FIG. The load resistor 23 in FIG. 7 is installed so that the applied current does not reflect from the electrode end to the power supply side. The orbital gradient of the beam changes due to the effects of electric and magnetic fields, and the betatron oscillation amplitude of the beam in the phase space shown in FIG. 5 begins to increase. Particles exceeding the stability limit shown in FIG. The amplitude sharply increases and the light is emitted from the emission deflector 13. Thereafter, when an irregular signal is applied to the electrodes 25 and 26, the betatron oscillation amplitude of each particle increases, and the particles having an initial small betatron oscillation amplitude soon exceed the stability limit of FIG. 5 and are emitted from the emission deflector 13. You. The stability limit is constant in the phase space of FIG. 5, and the orbit gradient dx / ds and the turn separation Ts of the output beam are also kept constant during the output process. Here, an electrode as shown in FIG. 7 was used. However, a time-varying component is superimposed on a power supply current of one of the electromagnets constituting the accelerator, or a new component is set within the stability limit of resonance at the time of emission. By providing a dedicated electromagnet for increasing the betatron oscillation of the particles and changing the power supply current irregularly, the same emission as described above can be performed.

In the above embodiment, the tune of the beam having an extremely small betatron oscillation amplitude is 1.67 set by the quadrupole electromagnet. However, due to the effect of the multipole electromagnet for generating resonance, the beta tune near the stability limit is obtained. The tune of particles with large thoron oscillation amplitude is 1.67-1.6666 from this value.
The tune of the beam, with a deviation of about 0.003 and an oscillation amplitude between them, is continuously distributed between 1.6666 and 1.67. On the other hand, as described in the operation section, in order to increase the betatron oscillation amplitude of the beam, it is desirable to apply an electromagnetic field having a frequency component approximately equal to the tune distribution of the beam to the beam. Therefore, the irregular signal power supply 24 of FIG. 7 may be a noise having an extremely wide frequency spectrum or a frequency band whose frequency is about 0.6 of the revolving frequency.
The frequency spectrum may be in the range of 5 times to 0.70 times, or a frequency spectrum obtained by adding a frequency in the above range to an integral multiple of the circulating frequency. FIG. 8 shows a configuration example of the irregular signal power supply. As shown in FIG. 8, after passing a frequency component from 0 to 0.025 times the circulating frequency from a noise source 51 having an almost infinite frequency spectrum through a filter 52, the noise source 51 has a frequency of 0.675 times the circulating frequency of the beam. When the signal is generated by the local oscillator 53 and the product of the signal and the output signal of the filter 52 is obtained by the multiplier 54, an irregular signal having a spectrum from 0.65 to 0.7 times the circulating frequency can be produced. . Alternatively, a high-frequency source having a required frequency spectrum can be produced by changing the pass frequency of the filter 52 without using the local oscillator 53. Also,
In this embodiment, an irregular signal is used as a disturbance to the beam,
By diffusing the beam in the phase space, the beam can be emitted with a constant current without being affected by the current ripple of the electromagnet power supply.

Next, a second embodiment of the present invention will be described.
The second embodiment has the same equipment configuration as the first embodiment except that the signals applied to the electrodes are made regular, and the operating method at the time of emission is also the same as that of FIG. As shown in FIG.
A single frequency signal source 55 shown in FIG. 9 is used in place of the irregular signal power supply 24 of FIG. The frequency f is a frequency Frev at which the beam circulates, and a fraction 0.33 (= 1-0.6) of the tune at the time of emission.
7) is equal to the product of When a signal of such a frequency is applied, the period of the external signal applied from the electrode and the period of the betatron oscillation substantially coincide with each other. Therefore, even for particles within the stability limit of FIG. Then, the light is emitted in the same manner as in the first embodiment. As described above, when an AC signal having a single frequency is applied, particles having a tune synchronized with this frequency are resonated by an external signal, and as a result, the vibration amplitude is rapidly increased and emission can be performed in a short time. . However, many particles that do not resonate with an external signal are emitted later than the resonance particles.

In the above embodiment, the single-frequency disturbance shown in FIG. 9 is used. However, a plurality of single-frequency signal sources 55 shown in FIG.
When the signal of n is added to the electrodes 25 and 26 through the adder 56, it becomes easier to emit a beam having a tune width as compared with a case where a single-frequency disturbance is used. In this case, the frequency of the signal to be applied is desirably set to a value close to a tune having a distribution.

In the first and second embodiments, 25 and 26 in FIG.
By applying signals of opposite polarities to both electrodes using the two electrodes shown in (1), an electromagnetic field was added to the beam, and the orbital gradient was changed. On the other hand, when the same electrode is used and a signal of the same polarity is applied to the two electrodes, an electric field in the s direction is generated at the ends of the electrodes 25 and 26 in the s direction, the beam is accelerated or decelerated, and the orbit gradient of the beam changes. Therefore, the betatron oscillation amplitude of the beam increases. At this time, the structure of the electrode may be not only a rod shape but also a plate shape. When signals of opposite polarities are applied to both electrodes, an electric field in the x direction or y direction can be generated by using a small disc-shaped electrode. Generally, when a time-varying signal is externally applied to the metal electrode, an electromagnetic field is generated and the orbit gradient of the beam can be changed, so that the betatron oscillation amplitude of the beam can be increased.

Next, a third embodiment of the present invention will be described.
FIG. 11 shows the device configuration of the third embodiment. 1 in that the octupole electromagnet 30 is used as a multipole electromagnet for exciting a secondary resonance (half-integer resonance) for emission, and that the betatron oscillation amplitude is within the stability limit of resonance. Is to use the high-frequency application cavity 31 to increase the number of the cavities.
However, the high frequency applying cavity 31 is a high frequency accelerating cavity 8 for accelerating the beam from low energy to high energy.
Use a different cavity. FIG. 12 shows an operation method after accelerating the beam to a predetermined energy for the third embodiment. After the acceleration, the high-frequency accelerating cavity 8 is stopped in FIG. 12 (1), and the convergence quadrupole electromagnet 5 and the divergence quadrupole electromagnet 7 are adjusted in FIG. 12 (2) to set the horizontal tune νx to 1.5.
Close to 5. Thereafter, the octupole electromagnet 30 is excited.
The magnetic field strength of the octupole electromagnet is set such that the particles circulate stably while undergoing betatron oscillation with different amplitudes. Here, a signal that changes irregularly with time is applied to the high-frequency application cavity 31. This high frequency application cavity 31 is shown in FIG.
As shown in the figure, an electric field is generated in the circling (s) direction of the beam,
A cavity in which a magnetic field is generated in the vertical (y) direction. In this cavity, the orbit gradient of the beam changes irregularly with each orbit, and the initial betatron oscillation amplitude sequentially exceeds the stability limit from large particles, and the deflector for emission. 13 is emitted. By continuously applying a signal that changes irregularly to the high-frequency application cavity 31, particles having small initial betatron oscillation amplitude are also increased by the same operation as in the first embodiment, and are emitted beyond the stability limit. You.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment relates to a method for adjusting the beam position and the beam current during the emission. FIG. 14 shows the device configuration of the fourth embodiment. In addition to the device configuration of the first embodiment shown in FIG. 1, an electromagnet 35 for correcting the trajectory of the emitted beam, a beam position measuring device 32, a current measuring device 33, and a control computer 34 are provided. FIG. 15 shows an operation method using this device configuration. In the present embodiment, according to the pattern stored in advance in the control computer 34 shown in FIG.
The intensity of an irregular time-varying signal applied to the high-frequency applying device 14 is controlled. The signal intensity pattern to be stored in the control computer 34 is determined for each operation, assuming that the operation after the beam is incident and accelerated on the circular accelerator and then emitted is one operation. Fig. 4 shows the operation method of incidence, acceleration, and emission.
It is the same as the driving method. The intensity pattern of the signal to be applied to the high-frequency application device 14 includes the time change of the target beam position and the beam current stored in advance in the computer and the beam position measured by the beam position measurement device 32 and the beam current measurement device 33. And the difference from the beam current is minimized. The target beam current can be easily realized not only in a temporally constant pattern but also in a pattern in which current emission and stop are repeated by using and stopping the means for increasing the betatron oscillation amplitude.

In this embodiment, a desired characteristic is obtained by changing the high-frequency signal intensity pattern using the beam measuring device. However, the signal applied to the high-frequency applying device 14 can be obtained without using the beam measuring device. By increasing the intensity of the beam during the emission, it is possible to emit a temporally constant beam current.
This is because, in the early stage of emission, there are many particles with large betatron oscillation amplitude that can be emitted with a small intensity signal, but in the late stage of emission, the number of orbiting particles decreases, and in order to obtain a constant emission current This is because it is necessary to increase the increasing speed of the betatron oscillation amplitude of the beam. Therefore, if such a time-varying high-frequency signal intensity pattern is given in advance, the target pattern can be realized in a shorter time in the operation of FIG.

In this embodiment, in order to obtain a target beam characteristic, only the intensity of the signal applied to the high-frequency application device 14 is adjusted. However, the frequency and frequency spectrum of the high-frequency signal are adjusted. Adjustment of the magnitude of the stability limit of resonance, that is, adjustment of tune by a quadrupole electromagnet, adjustment of the strength of the multipole electromagnet 9 for resonance excitation, or other electromagnets, such as the bending electromagnet 3 and the trajectory correcting electromagnet 35. Similar adjustments can be made when used.

In the above embodiment, the control of the output beam during normal operation is explained. Next, referring to FIG. 16, a description will be given of an operation method during an emergency stop during output according to a fifth embodiment. FIG.
Up to (5) is a normal operation, which is the same as the operation method of FIG. In FIG. 16 (6), it is determined whether there is a stop signal from the beam use system or an emergency stop signal from various safety systems. If there is a stop signal, the high frequency signal for increasing the beam system is stopped, and the beam is emitted. To stop. Since the high-frequency signal for beam emission can be stopped in a few microseconds, the beam emission can be stopped reliably in a short time. Further, if the stop of this high-frequency signal and the orbit change by the electromagnet of the output beam transport system are used simultaneously, it will be more reliable Beam can be stopped. Further, even if the beam emission is stopped halfway, the beam remaining in the accelerator can be emitted by applying the irregular signal for emission again. FIG. 16 shows a case where an irregular signal is applied for emission, but the same applies to a case where an AC signal having a single or a plurality of frequencies is applied.

Next, a sixth embodiment will be described with reference to FIG. In the sixth embodiment, neutral particles collide with the orbital beam to increase the betatron oscillation amplitude of particles within the stability limit of resonance. In the embodiment shown in FIG. 1, the high-frequency application device 14 is used to apply a time-varying electromagnetic field to the beam, but in this embodiment, a neutral particle injection device 36 is used instead of the high-frequency application device 14. FIG. 18 shows an operation method in this embodiment. The operation method is the same as that of FIG. 4 except for the part of (4) of FIG. 18 where neutral particles are injected. Neutral particle collisions can gradually increase the betatron oscillation amplitude of the orbiting beam, so that the beam position, beam diameter, and turn separation are all constant while maintaining the stability limit of resonance constant. it can. The emission current can be adjusted by adjusting the injection amount of the neutral particles.

Next, a seventh embodiment will be described. In the seventh embodiment, a charged particle different from the orbiting beam is made to collide with the orbiting beam to increase the betatron oscillation amplitude of the particle within the stability limit of resonance. In the sixth embodiment shown in FIG. 17, the neutral particle implanter 36 is used, but in this embodiment, an ion injector whose cross section is shown in FIG. 19 is used instead. Ions emitted from the ion source are implanted horizontally into the orbiting beam region. The ion implantation from this ion source is performed in place of the neutral particle implantation of the operation method shown in FIG. 18, but the same characteristics as those of the other embodiments described above can be realized with respect to beam emission. Further, the same emission can be realized even if a thin film is provided in a region where gas or ions are implanted and a charged particle beam is collided.

Hereinafter, effects of the present embodiment will be shown by simulation. The simulation conditions were that protons were used as charged particles, and the final energy during orbit was 300.
MeV, the resonance used is the secondary resonance shown in the third embodiment. The position of the electrode of the output deflector is 60 mm in the horizontal direction. 20 and 21 show a conventional operation method, in which the amplitude of the betatron oscillation before resonance is 10 mm,
For a 3 mm proton, the phase space is shown when the deviation from １ ／ of tune is set to 0.01, and the deviation is changed from 0.01 to 0.001 for resonance. The stability limit of the secondary resonance has an elliptical shape unlike the tertiary resonance. On the other hand, FIG.
2 and FIG. 23 are diagrams showing the operation method of the present embodiment. FIG. 22 shows the deviation from １ ／ of tune of 0.01 for protons having a betatron oscillation amplitude of 3 mm before resonance generation.
FIG. 4 shows a phase space when the high frequency applying device 14 irregularly increases the betatron oscillation amplitude of the beam while adjusting the resonance to a high frequency. FIG. 23 shows the phase space when the state of FIG. 22 is further advanced and protons exceeding the stability limit (about 10 mm) are being emitted. In the conventional driving method,
When the betatron oscillation amplitude before resonance is 10 mm and 3 mm, the turn separation Ts is about 10 mm and about 1 mm, respectively. Therefore, in the prior art, the betatron oscillation amplitude is 3
mm protons collide with the electrode and can hardly be emitted. Also, the deviation from １ ／ of the tune is set to 0.
Since the adjustment is made from 01 to 0.001, the emission gradient changes by 7 mrad. On the other hand, in the present embodiment, even if the betatron oscillation amplitude before the occurrence of resonance is 3 mm, the betatron oscillation amplitude gradually increases to about 10 mm, and resonance occurs.
As in the case of No. 1, the light is emitted with a turn separation Ts of 10 mm. The difference between the orbit gradient at the exit deflector position when the initial betatron oscillation amplitude is smaller than 3 mm and the orbit gradient when the initial oscillation amplitude is 10 mm is 0.0 mm.
Less than 1 mrad and the emittance of the output beam is 1πm
m · mrad or less. In this manner, a beam having a small initial betatron oscillation amplitude of 10 mm or less can be emitted similarly to the case of 10 mm. In the present embodiment, since the tune and the turn separation Ts can be made constant, the emission gradient, the emission position, and the beam diameter can be made constant. Furthermore, since the beam distribution often has a smaller betatron oscillation amplitude, it is impossible to obtain an emission efficiency of 50% by the conventional operation method, whereas the emission efficiency is increased to 90% or more by the operation method of the present embodiment. can do.

Finally, an embodiment of the medical accelerator system of the present invention will be described with reference to FIG. In the present embodiment, the beam from the pre-accelerator 16 is converted by the injector 15 into a circular accelerator 10.
Incident at 1. The configuration of the circular accelerator 101 and the method of emitting a beam are the same as those of the first embodiment shown in FIG. 1. After the beam is incident from the pre-stage accelerator 16, the beam is accelerated to a desired energy in 0.5 seconds, and A long pulsed beam is emitted over seconds. In the next 0.5 seconds, the amount of excitation of the electromagnet is reduced to prepare for the next incidence and acceleration. In this manner, the incidence, acceleration, and emission of the beam are repeated every two seconds.
At the time of emission, the stability limit of resonance is kept constant, and the emission frequency of the betatron is increased by the emission high-frequency application device 14 to generate resonance in the beam. Since the stability limit of the resonance is constant, the orbit gradient and turn separation at the position of the deflector for emission are constant, and the light can be emitted with a constant emission efficiency over time, and an emission efficiency of 90% or more can be obtained. The beam emitted from the emission deflector 13 is transported by the beam transport system 102 to a plurality of treatment rooms 103.
The transport system 102 is provided with a transport system electromagnet 104 for adjusting the beam diameter and the orbit gradient. The emittance of the transported beam is equal to or less than 1πmm · mrad as described with reference to FIGS. The size of the beam is one half of the product of the emittance and the quantity called the betatron function.
It is obtained from twice the power. The betatron function varies depending on the position of the beam transport system, but can be suppressed to 20 m or less by adjusting the amount of excitation of the transport system electromagnet 104, so that the maximum beam size in the transport system is about 10 mm. Therefore, the diameter of the vacuum duct used for the transport system 102 can be reduced to 20 mm or less even with a margin. The transport switching of the output beam to the plurality of treatment rooms is performed using the beam switching electromagnet 105. The switching of the beam is repeatedly performed in the beam emission process, that is, in a short time within 1 second. Thus, the beam is repeatedly distributed to a plurality of treatment rooms during one extraction. Of course, it is also possible to transport the beam to only one treatment room during one extraction, and to switch the beam to the next treatment room at the next extraction. The size and position of the beam irradiated to the patient in the treatment room are adjusted using an irradiation beam adjusting electromagnet (not shown). In the emission method of the present invention, the emittance of the emitted beam is constant at 1πmm · mrad or less. Therefore, the change in the size and position of the beam irradiated to the patient can be suppressed to 3 mm or less.

[0056]

According to the present invention, charging from a beam system is performed.
When the stop of the emission of the particle beam is requested, the emission of the charged particle beam can be surely stopped in a short time.

[0057]

[0058]

[0059]

[0060]

[Brief description of the drawings]

FIG. 1 is a diagram showing a circular accelerator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a stability limit in a phase space.

FIG. 3 is a diagram showing a phase space at the time of beam incidence / acceleration.

FIG. 4 is a diagram showing an operation method at the time of emission according to the first embodiment.

FIG. 5 is a diagram showing a phase space immediately before emission according to the first embodiment.

FIG. 6 is a diagram showing an output deflector electrode of the first embodiment.

FIG. 7 is a diagram illustrating a configuration of a high-frequency application device according to the first embodiment.

8 is a diagram showing a configuration example of the irregular signal power supply of FIG. 7;

FIG. 9 is a diagram illustrating a configuration example of a single frequency signal source according to a second embodiment.

FIG. 10 is a diagram illustrating a configuration example of a multi-frequency signal source according to a second embodiment.

FIG. 11 is a diagram illustrating an accelerator according to a third embodiment.

FIG. 12 is a diagram illustrating an operation method according to a third embodiment.

FIG. 13 is a diagram illustrating a high-frequency application cavity according to a third embodiment.

FIG. 14 is a diagram illustrating an accelerator according to a fourth embodiment.

FIG. 15 is a diagram showing an operation method according to a fourth embodiment.

FIG. 16 is a diagram showing an operation method according to a fifth embodiment.

FIG. 17 is a diagram illustrating an accelerator according to a sixth embodiment.

FIG. 18 is a diagram showing an operation method according to a sixth embodiment.

FIG. 19 is a view showing an ion injector of a seventh embodiment.

FIG. 20 is a diagram showing a phase space when protons having a betatron oscillation amplitude of 10 mm before resonance are resonated by a conventional operation method.

FIG. 21 is a diagram showing a phase space when protons having a betatron oscillation amplitude of 3 mm before resonance are resonated by a conventional operation method.

FIG. 22 is a diagram showing a phase space when a proton having a betatron oscillation amplitude before resonance of 3 mm is resonated by the operating method of the present invention.

FIG. 23: The state of FIG. 22 advances, and the stability limit (about 10 mm)
FIG. 7 is a diagram showing a phase space when protons exceeding the number are emitted.

FIG. 24 is a diagram showing a configuration example of a medical accelerator system of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Design track | truck, 3 ... Bending electromagnet, 5 ... Quadrupole electromagnet for convergence, 7 ... Quadrupole electromagnet for divergence, 8 ... High frequency acceleration cavity, 9 ...
Electromagnet for resonance excitation, 13 ... Deflector for emission, 14 ...
High frequency applying device, 15: injector, 20: deflector electrode for emission, 22: vacuum duct, 23: load resistance, 24:
Power supply, 25, 26 ... rod-shaped electrode, 31 ... high frequency application cavity,
32: Position measuring device, 33: Current measuring device, 34: Computer, 50: Amplifier, 51: Noise source, 52: Filter,
53: local oscillator, 54: multiplier, 55: single frequency signal source, 56: adder

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Watanabe 3-1-1 Sachimachi, Hitachi-shi, Ibaraki Hitachi, Ltd. Hitachi Plant (56) References JP-A-3-263800 (JP, A) Kaihei 5-266999 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05H 13/04 H05H 7/10

Claims (9)

(57) [Claims] 1. A charged particle beam emission method for emitting a charged particle beam from a circular accelerator by applying a high-frequency electric or magnetic field or an electromagnetic field to a circulating charged particle beam, wherein a stop signal is output from a beam use system. In this case, the emission of the charged particle beam from the circular accelerator is stopped by stopping the application of the high-frequency electric or magnetic field or the electromagnetic field. 2. A charged particle beam is emitted from a circular accelerator by applying a high-frequency electric or magnetic field or an electromagnetic field to a circulating charged particle beam, and the charged particle beam emitted from the circular accelerator is emitted from an irradiation device. In the particle beam emission method, when a stop signal is output from the beam using system , the emission of the charged particle beam from the circular accelerator is stopped by stopping the application of the high-frequency electric or magnetic field or the electromagnetic field. And stopping the emission of the charged particle beam from the irradiation device. 3. The charged particle beam emitted from the circular accelerator is transported to the irradiation device by a beam transport system,
3. The charged particle beam emitting method according to claim 2, wherein the trajectory of the charged particle beam is changed by an electromagnet constituting the beam transport system when the application of the high-frequency electric or magnetic field or the electromagnetic field is stopped. 4. The emission of a charged particle beam from the circular accelerator
After stopping irradiation, high-frequency electric or magnetic field or electromagnetic field
Charged particle beam from the circular accelerator
The charged particle beam emitting method according to any one of claims 1 to 3, wherein the emitting of the charged particle beam is started. 5. A charged particle beam orbiting along a circular orbit.
And applying a high-frequency electric or magnetic field or electromagnetic field
Makes the charged particle beam within the stability limit of the resonance
A high-frequency applying device for moving out of the stability limit;
Moved outside the stability limit of the resonance by the application device
A deflector for emitting a charged particle beam
A circular accelerator, wherein the high-frequency application device outputs a stop signal from a beam use system.
When applied, the high-frequency electric or magnetic field or electromagnetic
Deactivating the output deflector by stopping the application of the field
The emission of the charged particle beam from the
Circular accelerator. 6. A charged particle beam orbiting along a circular orbit.
To apply high frequency electric or magnetic or electromagnetic fields
A charged particle beam within the stability limit of resonance
A high-frequency application device that moves out of a fixed limit, and the high-frequency device
Moved outside the stability limit of the resonance by the application device
Has a deflector for emitting charged particle beam
Circular accelerator and emitted from the emission deflector
Circular acceleration with irradiation device for emitting charged particle beam
The high-frequency application device outputs a stop signal from the beam use system.
When applied , the irradiation of the charged particle beam from the deflector for emission is stopped by stopping the application of the high-frequency electric or magnetic field or the electromagnetic field, and the irradiation device
The emission of the charged particle beam from the
Circular accelerator system . 7. A charged particle beam orbiting along an orbit.
And applying a high-frequency electric or magnetic field or electromagnetic field
-Frequency marking that increases the vibration amplitude of the charged particle beam due to
The vibration amplitude is increased by the heating device and the high frequency applying device.
Deflector for emitting the charged charged particle beam
A circular accelerator with bets, the high frequency applying device, output stop signal from the beam used system
When the force is applied, the emission of the charged particle beam from the emission deflector is stopped by stopping the application of the high-frequency electric or magnetic field or the electromagnetic field .
Circular accelerator . 8. A charged particle beam orbiting along an orbit.
To apply high frequency electric or magnetic or electromagnetic fields
High frequency application to increase vibration amplitude of charged particle beam
The vibration amplitude is increased by the device and the high frequency applying device.
Exit deflector for which y de Serra charged particle beam
A circular accelerator having
And an irradiation device for emitting the emitted charged particle beam.
In a circular accelerator system, the high-frequency application device outputs a stop signal from a beam use system.
When applied , the irradiation of the charged particle beam from the deflector for emission is stopped by stopping the application of the high-frequency electric or magnetic field or the electromagnetic field, and the irradiation device
The emission of the charged particle beam from the
Circular accelerator system. 9. A load emitted from the output deflector.
Transporting an electron particle beam to the irradiation device using an electromagnet
A beam transport system, wherein the high-frequency
When the application of a frequency electric or magnetic field or electromagnetic field is stopped,
The electromagnet constituting the beam transport system is a charged particle beam.
9. The method according to claim 6, wherein the trajectory is changed.
A circular accelerator system according to any of the preceding claims.