JP2011076819A - Annular accelerator and particle beam therapy system employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an annular accelerator capable of switching ON/OFF of taking out of beams at high speed, and to provide a particle beam therapy system capable of performing soft radiation with the accelerator. <P>SOLUTION: The system includes an annular accelerator 200 for acceleration and deceleration of circulating charged particle beams, and an accelerator control device 501 for controlling the annular accelerator. The annular accelerator 200 has at least one sextupole electromagnetic field component generator 26 on the beam orbit of the charged particle beams, and at least one orbit deflection electromagnet making deflect the beam orbit of the charged particle beams in the installation position of the sextupole electromagnetic field component generator 26. The accelerator control device 500 controls to start excitation of the orbit deflection electromagnet during taking out of the charged particle beams from the annular accelerator 200 by exciting the sextupole electromagnetic field component generator 26. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an annular accelerator for accelerating and decelerating a charged particle beam to a predetermined energy, and a particle beam therapy system using the annular accelerator.

  Reflecting the recent aging society, as one of the cancer treatment methods, radiotherapy that is minimally invasive, has less burden on the body, and can maintain a high quality of life after treatment is attracting attention. Among them, a particle beam therapy system using a charged particle beam of protons or carbon accelerated by a ring accelerator is particularly promising because of excellent dose concentration on the affected area. The particle therapy system consists of an annular accelerator such as a synchrotron that accelerates the charged particle beam generated by the ion source to near the speed of light, a beam transport system that transports the charged particle beam extracted from the annular accelerator, and the position and shape of the affected area. In addition, an irradiation apparatus for irradiating a patient with a charged particle beam is provided.

  In the annular accelerator, each particle constituting the charged particle beam circulates while oscillating (meandering) around a central trajectory (design trajectory) called betatron vibration, and is accelerated and decelerated by the high-frequency acceleration cavity 25. The This frequency per round is called a tune, and is added to each of the particles whose decimal part is 0 (zero), 1/2, 1/3, ..., 1 / n (n is an integer). In the presence of a two-pole electromagnetic field, a quadrupole electromagnetic field, a hexapole electromagnetic field,..., A 2n-pole electromagnetic field, a phenomenon called resonance occurs, and the betatron oscillation amplitude of each particle increases rapidly. In many cases, the aforementioned additional electromagnetic field is due to an error electromagnetic field or the like, and the increase in the betatron oscillation amplitude thereby causes an increase in beam size or beam loss. On the other hand, a method of extracting a beam from the annular accelerator by skillfully utilizing and controlling this phenomenon is an extraction method called a slow extraction method or a resonance extraction method. If the slow extraction method is used, the charged particle beam can be slowly extracted over a plurality of laps, unlike the fast extraction method in which all the beams are extracted during one round of the annular accelerator. The extracted beam is mainly used in particle beam therapy and physics experiments.

  The principle of slow extraction will be described with reference to FIGS. 2 and 3 by taking an example of using third-order resonance. FIG. 2 shows the horizontal tune of the beam on the horizontal axis and the vertical tune on the vertical axis. The beam tune can be controlled by a quadrupole electromagnetic field component, and the resonance intensity and width (stop band) in the figure can be controlled by the additional electromagnetic field strength described above. FIG. 3 shows the phase space distribution due to the difference in the relationship between the resonance line and the tune for the slow extraction using the third-order resonance. In the case of the tunes shown in FIGS. 2A and 2C, that is, when the hexapole electromagnetic field component is small, or when the tune is sufficiently away from the resonance line, the particles are as shown in FIG. Stable elliptical motion is performed in the phase space as 1 → 2 → 3 → 4. On the other hand, when it is close to (B) in FIG. 2, particles with a small amplitude circulate stably as shown in FIG. 3 (b), but particles with a large amplitude rapidly increase in amplitude every lap due to the resonance phenomenon. Increase. The boundary between the stable region and the unstable region is called a separatrix, and the size of the separatrix is determined by the relationship between the tune and the strength of resonance as described above. Slow extraction is a method of using the increase in amplitude to extract from the annular accelerator in order of increasing amplitude.

Conventionally, in the slow extraction method, as a means for controlling ON / OFF of a beam to be extracted, there is one that uses a quadrupole electromagnet that is a quadrupole electromagnetic field component generator installed in the annular accelerator (see, for example, Patent Document 1). This is a method in which a quadrupole magnetic field component is applied to a beam by a quadrupole electromagnetic field component generator so that the tune is moved away from the resonance line and the beam is shifted from the resonance state to the stable circulation state and vice versa. Further, as a quadrupole electromagnetic field component generator, there is a method in which a quadrupole electric field is applied by a high-frequency cavity (see, for example, Patent Document 2). As another method, in the slow extraction method using high frequency, there is a method in which extraction of the beam is turned on / off by using ON / OFF of an extraction high-frequency device installed in the annular accelerator.
This is a method of stopping the beam extraction by stopping the increase of the beam vibration amplitude by turning off the electric field generated by the high frequency device for emission. In this method, there is one that performs synchronous operation with ON / OFF of an acceleration high frequency for the purpose of turning ON / OFF at a higher speed (for example, see Non-Patent Document 1).

JP 2005-332794 A JP 2005-353610 A

“Advanced RF-KO slow-extraction method for the reduction spill ripple”, Nuclear Instruments and Methods in physics Research A 492 (2002) 253-263.

In recent years, means for turning on / off an irradiation beam in several tens of microseconds or less has been demanded from the viewpoint of dose management and spot scanning in the field of particle beam therapy. When the slow extraction method is used, as a means for controlling ON / OFF of the extraction beam, there is one using a quadrupole electromagnet installed in the annular accelerator as the quadrupole electromagnetic field component generator described in Patent Document 1. However, when a general quadrupole electromagnet constituting an annular accelerator is used, it takes several ms to turn on / off the beam. Faster beam ON / O
In order to control the FF, it is necessary to use the quadrupole electromagnetic field component generating device described in Patent Document 1 that operates at high speed, and it has been a problem to suppress the size and cost of the accelerator. Patent Document 2 describes a method of using an electric field as a quadrupole electromagnetic field component generator, but even in this case, it is necessary to newly install a cavity. As another method, in a slow extraction method using a high frequency, it is possible to control the beam ON / OFF using an extraction high frequency device installed in the annular accelerator. In this case, the beam emission can be stopped in several hundred microseconds. Further, as a means for realizing higher speed, a synchronous operation method with a high-frequency acceleration cavity described in Non-Patent Document 1 has been devised. This method realizes high-speed beam stop in about 50 microseconds. However, in order to change the voltage that is a control parameter of the high-frequency acceleration cavity, disturbance is given to the circulating beam in the annular accelerator. For this reason, advanced adjustments are required for beam loss suppression, outgoing beam amount control, timing control, and the like.

  A feature of the present invention includes an annular accelerator that accelerates and decelerates a circulating charged particle beam, and an accelerator controller that controls the annular accelerator, and the annular accelerator is arranged on at least one six on the beam trajectory of the charged particle beam. A polar electromagnetic field component generator and at least one orbital deflecting electromagnet for displacing the beam trajectory of the charged particle beam at the installation position of the hexapole electromagnetic field component generator; In the period when the charged particle beam is taken out from the annular accelerator by exciting the orbit, the excitation of the orbital deflection electromagnet is started and the beam orbit of the charged particle beam is controlled to be displaced.

  According to the present invention, since the charged particle beam extraction ON / OFF control from the annular accelerator can be performed at high speed, the charged particle beam can be emitted with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system configuration diagram showing a configuration of a particle beam therapy system that is a preferred embodiment (embodiment 1) of the present invention. It is explanatory drawing of the slow beam extraction method in a cyclic | annular accelerator. It is explanatory drawing of the slow beam extraction method in a cyclic | annular accelerator. It is a figure which shows the driving | operation pattern of the annular accelerator with which the particle beam therapy system which is one preferable Example (Example 1) of this invention is equipped. It is a figure which shows the driving | operation pattern of the annular accelerator with which the particle beam therapy system which is another Example (Example 2) of this invention is equipped. It is a figure which shows the driving | running pattern of the annular accelerator with which the particle beam therapy system which is another Example (Example 3) of this invention is equipped. It is explanatory drawing of a spot scanning irradiation method. It is a figure which shows the driving | running pattern of the annular accelerator with which the particle beam therapy system which is another Example (Example 4) of this invention is equipped.

  Embodiments of the present invention will be described with reference to the drawings.

  Hereinafter, the configuration and operation of the particle beam therapy system according to the first embodiment of the present invention will be described with reference to FIGS.

  First, the whole structure of the particle beam therapy system 1 by this embodiment is demonstrated using FIG. The particle beam therapy system 1 includes a low energy beam injection system 100, an annular accelerator 200 (for example, a synchrotron), a beam transport system 300, an overall controller 400, and an accelerator controller 500.

  The low energy beam injection system 100 includes an ion source 11, a pre-stage accelerator 12, a beam transport system deflection electromagnet 13 and a focusing / divergence quadrupole electromagnet 14 arranged as necessary. The annular accelerator 200 has a function of accelerating the charged particle beam preliminarily accelerated by the pre-stage accelerator 12 to a predetermined energy and then emitting the accelerated charged particle beam. The beam transport system 300 includes a beam transport system deflecting electromagnet 31 and a focusing / diverging quadrupole electromagnet 32, and has a function of guiding the charged particle beam emitted from the annular accelerator 200 to the irradiation device 33 that irradiates the affected area of the patient 41. . The overall control device 400 has a function of controlling ON / OFF of the extraction beam. Overall control device 400 is connected to accelerator control device 500.

  The accelerator control device 500 includes an incident bump electromagnet control unit 501, a resonance excitation hexapole electromagnet control unit 502, and an extraction high frequency device control unit 503, and has a function of controlling the annular accelerator 200. The incident bump electromagnet control unit 501 is connected to the incident bump electromagnet power supply 221 A connected to the incident bump electromagnet 221 and the incident bump electromagnet power supply 222 A connected to the incident bump electromagnet 222. To control. The incident bump electromagnet control unit 501 controls the excitation amount of the incident bump electromagnet 221 by changing the excitation current excited from the incident bump electromagnet power source 221A to the incident bump electromagnet 221. Similarly, the incident bump electromagnet control unit 501 controls the excitation amount of the incident bump electromagnet 222 by changing the excitation current excited from the incident bump electromagnet power supply 222A to the incident bump electromagnet 222. The resonance excitation hexapole electromagnet controller 502 is connected to the resonance excitation hexapole electromagnet power supply 26A connected to the resonance excitation hexapole electromagnet 26, and controls the resonance excitation hexapole electromagnet power supply 26A. The resonance excitation hexapole electromagnet control unit 502 controls the excitation amount of the resonance excitation hexapole electromagnet 26 by changing the excitation current excited from the resonance excitation hexapole electromagnet power supply 26A to the resonance excitation hexapole electromagnet 26. To do. The emission high-frequency device control unit 503 is connected to the emission high-frequency power source 27A connected to the emission high-frequency device 27, and controls the emission high-frequency power source 27A. The emission high-frequency device control unit 503 controls the excitation amount of the emission high-frequency device 27 by controlling the excitation current that excites the emission high-frequency device 27 from the emission high-frequency power source 27A.

  The annular accelerator 200 includes an incident deflector (incident septa) 21 that receives the charged particle beam preliminarily accelerated by the former accelerator 12, incident bump electromagnets 221 and 222 for shifting the circular orbit at the time of incidence, A deflecting electromagnet 23 that deflects the particle beam and circulates on a fixed orbit, a converging / diverging quadrupole electromagnet 24 that applies a convergence force in the horizontal / vertical direction so that the charged particle beam does not spread, and a charged particle beam with a high-frequency acceleration voltage A high-frequency acceleration cavity 25 for accelerating the beam to a predetermined energy, a hexapole electromagnet 26 for resonance excitation that forms a separatrix with respect to the vibration amplitude of the circulating charged particle beam, and the vibration amplitude of the charged particle beam in the high-frequency electromagnetic field Is increased to exceed the separatrix and extracted to the outside, and deflected to emit a charged particle beam Comprising a morphism deflection device 28. The incident deflection device 21, the incident bump electromagnets 221 and 222, the deflection electromagnet 23, the quadrupole electromagnet 24, the high frequency acceleration cavity 25, the hexapole electromagnet 26, the emission high frequency device 27, and the emission deflection device 28 are along the beam trajectory. Be placed. An incident deflecting device 21 is connected to the low energy beam incident system 100. A plurality of incident bump electromagnets 221 and incident bump electromagnets 222 (two incident bump electromagnets 221 and 222 in this embodiment) are arranged with the incident deflecting device 21 interposed therebetween. The resonance excitation hexapole electromagnet 26 is disposed between the incident bump electromagnet 221 and the incident bump electromagnet 222. The resonance excitation hexapole electromagnet 26 is more preferably installed in a bump trajectory generated by the incident bump electromagnets 221 and 222 in a region where the trajectory displacement is large. This is because the product of the magnetic field intensity by the resonance excitation hexapole electromagnet 26 and the orbital displacement of the bump trajectory becomes a force for moving the tune (a force for moving from A to B shown in FIG. 2). In the present embodiment, as shown in FIG. 1, an example in which two incident bump electromagnets 221 and 222 are installed on the beam trajectory is shown, but three or more incident bump electromagnet devices may be installed. . For example, when three incident bump electromagnets are installed, a configuration in which the incident bump electromagnet 221 and the resonance excitation hexapole electromagnet 26 of this embodiment are arranged on the beam trajectory, or the resonance excitation hexapole electromagnet 26 and A configuration in which the bump electromagnet 222 is disposed between the incident bump electromagnets 222 is conceivable. Even when a plurality of incident bump electromagnets are arranged in this way, the resonance excitation hexapole electromagnet 26 is placed in a bump trajectory generated by the plurality of incident bump electromagnets and in a region where the trajectory displacement is large. Even better. An exit deflector 28 is connected to the beam transport system 300.

  Next, the operation of the annular accelerator 200 according to the first embodiment will be described using an example of the operation pattern of the annular accelerator 200 shown in FIG.

  When the pre-stage accelerator 12 accelerates the charged particle beam to a predetermined energy (energy necessary for the incidence of the annular accelerator 200), the accelerated charged particle beam is incident on the annular accelerator 200 through the incident deflecting device 21. In order to efficiently enter many charged particle beams, the circular accelerator 200 includes two or more bump electromagnets. In this embodiment, two bump electromagnets 221 and 222 form a bump trajectory (a trajectory shifted from the central trajectory), and a charged particle beam is incident while changing this temporally. The accelerator controller 501 controls the amount of excitation of the incident bump electromagnet 221 and the incident bump electromagnet 222 by controlling the incident bump electromagnet power supply 221A and the incident bump electromagnet power supply 222A. The incident charged particle beam is accelerated by the high-frequency accelerating cavity 25 while stably circling by the deflection electromagnet 23 and the quadrupole electromagnet 24. At this time, since the charged particle beam becomes difficult to bend with acceleration, the magnetic field strengths of the deflection electromagnet 23 and the quadrupole electromagnet 24 are adjusted to change the circular orbit to be constant. As shown in FIG. 1, the hexapole electromagnet 26, which is a means for exciting resonance, is disposed in a bump trajectory formed by an incident bump electromagnet, which is an area between a plurality of bump electromagnets. Thus, exciting the bump electromagnets 221 and 222 makes it possible to control the tune by applying a quadrupole magnetic field component to the circular beam.

  Next, the beam extraction ON / OFF procedure is shown below. As shown in FIG. 4A, the annular accelerator 200 is controlled so that the charged particle beam repeats incidence, acceleration, emission, and deceleration. After the charged particle beam incident on the circular accelerator 200 is accelerated to a predetermined energy, the operation tune is set near the point B shown in FIG. 2, and the hexapole electromagnet 26, which is a means for exciting resonance, is excited. Starting and exciting as shown in FIG. 4B, a separatrix is formed, and preparation for beam extraction is completed. When the overall control device 400 transmits an emission start signal (ON signal) indicating the start of beam emission to the accelerator control device 500 as shown in FIG. 4C with the hexapole electromagnet 26 excited, accelerator control is performed. In accordance with the emission start signal, the apparatus 500 turns on the emission high-frequency device 27 as shown in FIG. The amplitude of the charged particle beam is increased by applying a high frequency by the high frequency device 27 for extraction, and the charged particle beam that has spread to the outside of the separatrix is taken out from the annular accelerator 200. When the overall control device 400 outputs an extraction stop signal (OFF signal) to the accelerator control device 500, the accelerator control device 500 stops (OFF) high-frequency application to the extraction high-frequency device 27. At the same time or at a predetermined timing, the accelerator controller 500 excites the incident bump electromagnets 221 and 222 as shown in FIG. Conventionally, this incident bump electromagnet is used only at the time of incidence and has not been excited at the time of emission. This incident bump electromagnet is used to change the trajectory during several hundred microseconds, which is a typical incident time, and can respond at a high speed with a magnetic field rising in about 100 to 300 microseconds for that purpose. Equipment. In this embodiment, when the charged particle beam is emitted from the annular accelerator 200, the orbiting bump electromagnets 221 and 222 can be excited to change the orbit from the central orbit at high speed. A quadrupole magnetic field component can be applied to the charged particle beam by the interaction between the resonance excitation hexapole magnet 26 and the incident bump electromagnets 221 and 222 installed on the orbit. As a result, the tune deviates from resonance, and beam extraction stops as shown in FIG. According to the present embodiment, when the emission of the charged particle beam from the annular accelerator 200 is stopped, the amount of excitation of the incident bump electromagnets 221 and 222 is increased during the period in which the resonance excitation hexapole magnet 26 is excited. Thus, the time until the charged particle beam emitted from the annular accelerator 200 is stopped can be shortened to a fraction of the rise time, that is, to several tens of microseconds.

  In this way, as means for controlling the trajectory at high speed, the incident bump electromagnets 221 and 222 are used, and the resonance excitation hexapole electromagnet 26 used for resonance excitation is arranged in the bump trajectory, so that the annular accelerator 200 is newly added. It is possible to realize high-speed beam emission and stop easily and inexpensively without adding equipment. This makes it possible to stop high-speed beams in an emergency or reduce unnecessary beam irradiation during irradiation, thereby improving irradiation accuracy and realizing planned treatment.

  In this embodiment, an annular accelerator 200 for accelerating / decelerating a charged particle beam includes an incident bump electromagnet (orbit deflection electromagnet) that forms a bump trajectory, and at least one resonance excitation hexapole electromagnet (six in the bump trajectory). The electromagnetic beam component generator), and the orbital beam trajectory at the position of the exciting hexapole electromagnetic field component generator device is displaced by the orbital deflection electromagnet, thereby allowing A quadrupole electromagnetic field component is applied. As a result, the beam tune can be changed, the state can be changed from the unstable region to the stable region at high speed, and the charged particle beam can be extracted at high speed. That is, according to the present embodiment, the ON / OFF time of the extraction beam from the annular accelerator 200 can be increased. As a result, it is possible to provide an annular accelerator and a particle beam therapy system that can reduce an unnecessary dose irradiated when the beam is turned ON / OFF. In addition, since the time resolution is improved by increasing the beam ON / OFF time, it is useful in other industrial accelerator systems, accelerator systems for physical experiments, and the like.

  According to the present embodiment, an orbital deflection electromagnet that forms a bump trajectory and at least one hexapole electromagnetic field component generator in the bump trajectory are arranged, and the orbiting beam trajectory at the position of the hexapole electromagnetic field component generator being excited. Is displaced by an orbital deflection electromagnet, and the extraction of the charged particle beam can be controlled ON / OFF. In this case, in order to perform beam extraction ON / OFF at high speed, it is only necessary to increase the speed of the orbital deflection electromagnet, and the electrode / magnetic pole shape is simpler than that of a quadrupole electromagnetic field component generator having an equivalent response time. Manufacture is easy and it is easy to ensure the electromagnetic field accuracy. Therefore, the charged particle beam extraction ON / OFF can be speeded up relatively inexpensively and with high accuracy.

  In this embodiment, as shown in FIG. 4, the accelerator controller 500 has a positive polarity (FIG. 4B) for exciting the resonance excitation hexapole electromagnet 26 and a polarity for exciting the incident bump electromagnets 221 and 222. Is controlled to be positive (FIG. 4E). That is, when stopping the charged particle beam emitted from the annular accelerator 200 (when the beam OFF signal shown in FIG. 4C is output), the accelerator control device 500 is positive for the resonance excitation hexapole electromagnet 26. With the magnetic field excited, the magnetic field is excited with respect to the incident bump electromagnets 221 and 222 so that the displacement at the position of the resonance excitation hexapole electromagnet 26 becomes positive. In the present embodiment, the case where the displacement at the position of the resonance excitation hexapole electromagnet 26 becomes positive when the incident bump electromagnets 221 and 222 are excited positively is shown. Thus, by exciting the incident bump electromagnets 221 and 222 positively, the tune is moved away from the resonance and the emission of the charged particle beam from the annular accelerator 200 is stopped. Also, by stopping the excitation of the incident bump electromagnets 221 and 222, the tune returns to the resonance state and starts emitting the charged particle beam from the annular accelerator 200. However, the accelerator controller 500 excites the resonance excitation hexapole electromagnet 26 to a negative polarity and the incident bump electromagnets 221 and 222 at the same timing as in this embodiment (FIG. 4). Excitation may be performed so that the displacement at the position of the electromagnet 26 becomes negative (excitation of a magnetic field having a polarity opposite to that of the present embodiment). In such a case, the same effect as in the present embodiment can be obtained.

  In the first embodiment, the extraction beam is turned off when the incident bump electromagnets 221 and 222 are excited (the charged particle beam emitted from the annular accelerator 200 is stopped). When the bump electromagnets 221 and 222 are excited, the extraction beam is turned on (a charged particle beam is emitted from the annular accelerator 200), and when the excitation of the incident bump electromagnets 221 and 222 is stopped, the extraction beam is turned off (annular accelerator). An example of stopping the charged particle beam emitted from 200) is shown.

  The operation pattern of the annular accelerator 200 of the present embodiment is shown in FIG. In this case, the hexapole electromagnet 26, which is a means for exciting resonance, is excited and the operation tune is set to the point A shown in FIG. When the overall control device 400 outputs an extraction start signal (ON signal) indicating the start of beam extraction to the accelerator control device 500 as shown in FIG. 5C with the hexapole electromagnet 26 excited, the accelerator control device. In accordance with this emission start signal, 500 controls the emission high-frequency device 27 at a predetermined timing as shown in FIG. 5 (d), and as shown in FIG. 5 (e), an incident bump at a predetermined timing. The electromagnets 221 and 222 are excited to form bump trajectories, and the tune is brought close to the point in FIG. 2B. As a result, the charged particle beam enters a resonance state, and is sequentially extracted from the annular accelerator 200 in the order from which the betatron oscillation is increased. When stopping the extraction of the charged particle beam, the accelerator controller 500 controls the extraction high-frequency device 27 to stop the extraction high-frequency (OFF), and controls the incident bump electromagnets 221 and 222 to control the bump trajectory. By moving the tune away from the resonance.

  According to the present embodiment, an orbital deflection electromagnet that forms a bump trajectory and at least one hexapole electromagnetic field component generator in the bump trajectory are arranged, and the orbiting beam trajectory at the position of the hexapole electromagnetic field component generator being excited. Is displaced by an orbital deflection electromagnet, and the extraction of the charged particle beam can be controlled ON / OFF. In order to turn on / off the beam at high speed, it is only necessary to increase the speed of the orbital deflection electromagnet, and the electrode / magnetic pole shape is simple compared to a quadrupole electromagnetic field component generator having the same response time, making it easy to manufacture. Therefore, it is easy to ensure the accuracy of the electromagnetic field. Therefore, the charged particle beam extraction ON / OFF can be speeded up relatively inexpensively and with high accuracy.

  According to this embodiment, the ON / OFF time of the extraction beam from the annular accelerator 200 can be increased. As a result, it is possible to provide an annular accelerator and a particle beam therapy system that can reduce an unnecessary dose irradiated when the beam is turned ON / OFF. In addition, since the time resolution is improved by increasing the beam ON / OFF time, it is useful in other industrial accelerator systems, accelerator systems for physical experiments, and the like.

  According to the present embodiment, when the incident bump electromagnets 221 and 222 are excited by bringing the charged particle beam into a resonance state by forming the bump trajectory, the charged bump beam magnets 221 and 222 are extracted. It is possible to turn off the charged particle beam (outgoing beam) emitted from the annular accelerator 200 when is not excited. In this case, since the charged particle beam is emitted from the annular accelerator 200 and irradiated to the patient only when the incident bump electromagnets 221 and 222 are being excited, the irradiation accuracy is further improved.

  In this embodiment, as shown in FIG. 5, the accelerator controller 500 has a positive polarity (FIG. 5B) for exciting the resonance excitation hexapole electromagnet 26 and a polarity for exciting the incident bump electromagnets 221 and 222. Is controlled to be negative (FIG. 5E). That is, when the emission of the charged particle beam from the annular accelerator 200 is started (when the beam ON signal shown in FIG. 5C is output), the accelerator control device 500 applies the positive polarity to the resonance excitation hexapole magnet 26. In this state, the incident bump electromagnets 221 and 222 are excited so that the displacement at the position of the resonance excitation hexapole electromagnet 26 is negative. In this state, a charged particle beam is emitted from the annular accelerator 200. Further, when the emission of the charged particle beam from the annular accelerator 200 is stopped (when the beam OFF signal shown in FIG. 5C is output), the resonance excitation hexapole magnet 26 is excited with a positive magnetic field. Thus, the excitation to the incident bump electromagnets 221 and 222 is stopped to move the tune away from the resonance. In this manner, the charged bumps 221 and 222 are excited so that the displacement at the position of the resonance excitation hexapole electromagnet 26 becomes negative, thereby bringing the tune closer to resonance, so that the charged particle beam from the annular accelerator 200 is obtained. Is started, and excitation of the incident bump electromagnets 221 and 222 is stopped, so that the tune is moved away from the resonance and the emission of the charged particle beam from the annular accelerator 200 is stopped. However, the accelerator control device 500 excites the resonance excitation hexapole electromagnet 26 to a negative polarity at the same timing as in the present embodiment (FIG. 5), and the incident bump electromagnets 221 and 222 become resonance excitation hexapole electromagnets. Excitation (a magnetic field having a polarity opposite to that of the present embodiment) may be performed so that the displacement at the position 26 becomes positive. In such a case, the same effect as in the present embodiment can be obtained.

  In the first and second embodiments, an example in which the hexapole electromagnet 26 that is a means for exciting resonance is provided between the plurality of incident bump electromagnets 221 and 222 has been described. An example in which a device (a correcting hexapole electromagnet) 26A having a hexapole electromagnetic field component such as a hexapole electromagnet for correcting chromaticity is installed instead of the electromagnet 26 will be described.

  The operation pattern of the annular accelerator 200 of the present embodiment is shown in FIG. As shown in FIG. 6G, a typical operation pattern of the correcting hexapole electromagnet 26A is excited over the entire period from incidence to completion of acceleration and extraction. By controlling the excitation state correcting hexapole electromagnet 26A and the incident bump electromagnets 221 and 222 to control the displacement of the bump trajectory at the time of emission, the tune can be changed in the same manner as in the first and second embodiments. The particle beam can be turned on / off at high speed.

  According to this embodiment, the ON / OFF time of the extraction beam from the annular accelerator 200 can be increased. As a result, it is possible to provide an annular accelerator and a particle beam therapy system that can reduce an unnecessary dose irradiated when the beam is turned ON / OFF. In addition, since the time resolution is improved by increasing the beam ON / OFF time, it is useful in other industrial accelerator systems, accelerator systems for physical experiments, and the like.

  According to the present embodiment, an orbital deflection electromagnet that forms a bump trajectory and at least one correction hexapole electromagnet 26A are arranged in the bump trajectory, and the orbiting beam trajectory at the position of the correction hexapole electromagnet 26A being excited. Is displaced by an orbital deflection electromagnet, and the extraction of the charged particle beam can be controlled ON / OFF. In this case, in order to perform beam extraction ON / OFF at high speed, it is only necessary to increase the speed of the orbital deflection electromagnet, and the electrode / magnetic pole shape is simpler than that of a quadrupole electromagnetic field component generator having an equivalent response time. Manufacture is easy and it is easy to ensure the accuracy of the electromagnetic field. Therefore, the charged particle beam extraction ON / OFF can be speeded up relatively inexpensively and with high accuracy.

  In the first to third embodiments, the case where the number of excitations of the incident bump electromagnets 221 and 222 at the time of beam extraction is shown as one, but in this embodiment, the incident bump electromagnets 221 and 222 are turned ON / OFF a plurality of times. An example of such control will be shown. According to the present embodiment, the present invention can be applied to an irradiation method called discrete spot scanning that irradiates a plurality of spots in one emission period.

  The spot scanning irradiation method will be briefly described with reference to FIG. As shown in FIG. 7A, the beam irradiation apparatus includes a horizontal and vertical scanning electromagnet which is a means for two-dimensionally scanning the charged particle beam guided by the beam transport system 300 in accordance with the cross-sectional shape of the affected part 42. 33a, 33b, and a measuring instrument (for example, a beam monitor 33c) for measuring beam current, shape, position, and the like are provided as necessary. The affected part 42 is divided into a plurality of layers in the depth direction as shown in FIG. 7A, and each layer is further divided two-dimensionally as shown in FIG. 7B. In the depth direction, each layer is selectively irradiated by changing the energy of the irradiation beam by changing the energy of the extracted beam of the annular accelerator (synchrotron) 200 or the like. Within each layer, the scanning electromagnets 33a and 33b scan the irradiation beam two-dimensionally to give a predetermined dose to each irradiation spot SP.

Next, an operation pattern of the annular accelerator 200 of the present embodiment is shown in FIG. Since it is the same as that of Example 1 until the start of beam extraction, it is omitted here. When the dose of one irradiation spot SP expires, the overall control device 400 outputs an irradiation end signal (c) to the accelerator control device 500, and the accelerator control device 500 outputs an extraction high frequency (d) to the extraction high frequency device 27. Turn off (stop). Upon receiving the irradiation end signal (c), the accelerator controller 500 excites the incident bump electromagnet (e) at the same time or at a predetermined timing. Thereby, the extraction beam (f) can be turned off (stopped). The extraction beam is moved to the next irradiation spot by changing the set value of the scanning electromagnets 33a and 33b with the extraction beam turned off. After the movement, the irradiation of the next spot SP is started by turning off the incident bump electromagnets 221 and 222.
Similarly, irradiation of a plurality of spots SP in the same layer is performed by performing these irradiations and stops a plurality of times.

  According to this embodiment, an orbital deflection electromagnet that forms a bump trajectory and at least one hexapole electromagnetic field component generator in the bump trajectory are arranged, and the orbiting beam trajectory at the position of the hexapole electromagnetic field component generator being excited. Is displaced by an orbital deflection electromagnet, and the extraction of the charged particle beam can be controlled ON / OFF. In this case, in order to perform beam extraction ON / OFF at high speed, it is only necessary to increase the speed of the orbital deflection electromagnet, and the electrode / magnetic pole shape is simpler than that of a quadrupole electromagnetic field component generator having an equivalent response time. Manufacture is easy and it is easy to ensure the accuracy of the electromagnetic field. Therefore, the charged particle beam extraction ON / OFF can be speeded up relatively inexpensively and with high accuracy.

  According to the present embodiment, the extraction beam ON / OFF time can be increased. As a result, it is possible to provide an annular accelerator and a particle beam therapy system that can reduce an unnecessary dose irradiated when the beam is turned ON / OFF. Furthermore, it is possible to provide an annular accelerator and a particle beam therapy system that can supply an extraction beam having a time structure suitable for the spot scanning irradiation method by performing beam ON / OFF a plurality of times. In addition, since the time resolution is improved by increasing the beam ON / OFF time, it is useful in other industrial accelerator systems, accelerator systems for physical experiments, and the like.

  When this embodiment is used, spot scanning irradiation capable of turning on and off the beam can be realized at low cost and simply as described above. Compared with the method of spreading the beam using a scatterer in advance and cutting and irradiating it according to the shape of the affected area, this method can irradiate the affected area of the patient more precisely, so it is unnecessary for normal tissues Irradiation can be reduced and a high therapeutic effect can be expected. Furthermore, since the beam utilization efficiency can be increased, the treatment time can be shortened and the burden on the patient can be reduced.

DESCRIPTION OF SYMBOLS 1 Particle beam therapy system 11 Ion source 12 Previous stage accelerators 13, 31 Beam transport system deflection electromagnets 14, 32 Beam transport system convergence / divergence quadrupole electromagnet 21 Incident deflection device (incident scepter)
23 Deflection electromagnet 24 Convergence / divergence quadrupole electromagnet 25 High frequency acceleration cavity 26 Resonance excitation hexapole electromagnet 26A Resonance excitation hexapole electromagnet power supply 27 Emission high frequency device 27A Emission high frequency power supply 28 Ejection deflection device 33 Irradiation device 33a Scanning Electromagnet 1
33b Scanning Electromagnet 2
33c Beam monitor 41 Patient 42 Affected part 51 Control device 100 Low energy beam injection system 200 Annular accelerator (circular accelerator)
221 and 222 Incident bump electromagnets 221A and 222A Incident bump electromagnet power supply 300 Beam transport system 400 Overall controller 500 Accelerator controller

Claims (4)

An annular accelerator that accelerates and decelerates the circulating charged particle beam;
An accelerator controller for controlling the annular accelerator,
The annular accelerator is
At least one hexapole electromagnetic field component generator on the beam trajectory of the charged particle beam;
And at least one orbital deflection electromagnet for displacing the beam trajectory of the charged particle beam at the installation position of the hexapole electromagnetic field component generator,
The accelerator control device comprises:
During excitation of the hexapole magnetic field component generator and extraction of the charged particle beam from the annular accelerator, excitation of the orbital deflection electromagnet is started to control the beam orbit of the charged particle beam to be displaced. An annular accelerator characterized by that. The hexapole electromagnetic field component generator is a hexapole electromagnet for resonance excitation;
The orbital deflection magnet is an incident bump electromagnet,
The annular accelerator according to claim 1, wherein the resonance excitation hexapole electromagnet is disposed in a bump trajectory formed by the incident bump electromagnet.   The resonance excitation hexapole magnet is disposed between a first incident bump electromagnet and a second incident bump electromagnet, and is disposed in a bump trajectory formed by the incident bump electromagnet. The annular accelerator according to claim 2. An annular accelerator according to any one of claims 1 to 3,
An irradiation device for irradiating an irradiation target with the charged particle beam emitted from the annular accelerator;
A particle beam therapy system comprising: a beam transport system that connects the annular accelerator and the irradiation device and transports the accelerated charged particle beam to the irradiation device.

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