JP2857598B2 - Accelerator operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an accelerator , and more particularly, to a method for operating an accelerator using a charged particle beam for therapy .

[0002]

2. Description of the Related Art At present, particle accelerators are used not only for research on high energy physics until now, but also for medical use such as generation of radioisotopes and particle beam therapy for cancer, and industrial use such as material irradiation.
It is used for agricultural applications such as seed irradiation, and one accelerator may be used for multiple purposes.

When a particle accelerator is used, an operation pattern of injection of a particle beam from a pre-stage accelerator to a circular accelerator, acceleration of a particle beam by a circular accelerator, and emission of a particle beam from a circular accelerator is repeated at intervals of about several seconds. There is. Conventionally, the operation of such a particle accelerator has been performed in the form of a sine-wave or step-like operation, as shown in Monthly Physics / Vol.6 No.1, 1985 p. This is performed by repeating the pattern at a predetermined cycle.

[0004]

In the conventional driving method,
The excitation pattern of the electromagnet constituting the accelerator is constant.
For example, when performing cancer treatment, the affected part is irradiated with a particle beam. By adjusting the beam energy to an energy corresponding to the depth of the affected part, normal cells around the affected part can be prevented from being damaged. That is, when changing the patient to be treated, it is necessary to perform the operation in which the beam energy is adjusted for each patient.

When the user changes the beam energy to be used, that is, when the excitation amount of the electromagnet is changed, the initialization operation is performed to erase the operation history of the electromagnet, that is, the hysteresis (magnetic history) of the electromagnet. Required.
The initialization operation is indispensable in order to repeat the operation pattern actually used a plurality of times in advance and to make the hysteresis of the electromagnet constant under the operation conditions.

However, there is a problem that a time during which no beam is emitted due to the initialization operation is generated, so that the operation time of the beam is greatly reduced. In addition, since the operation pattern of the accelerator is different for each user, there is a problem that it takes time to perform beam adjustment or the like until the beam can be actually used.

It is an object of the present invention to increase the operating rate of an accelerator.
It is an object of the present invention to provide an accelerator operating method.

[0008]

A first aspect of the present invention for achieving the above object is as follows.
The feature of the invention is that the charged particle beam is incident, accelerated and emitted, and in the operating method of the accelerator for demagnetizing the electromagnet used in the accelerator after this emission, the magnetic field strength of the electromagnet is
After the emission of the charged particle beam and before the demagnetization, the intensity of the magnetic field is increased to a value equal to or higher than the maximum magnetic field used by the electromagnet, and then the demagnetization is performed. The magnetic field strength of the electromagnet is preferably
Or the saturation magnetic field strength of the electromagnet. The features of the second invention that achieves the above object include, in addition to the features of the first invention,
The operation cycle including the incidence, the acceleration, the emission, the increase in the magnetic field strength after the emission, and the demagnetization is repeated.
Emission in a certain operation cycle when driving
The energy of the charged particle beam is
Is different from the energy of the charged particle beam emitted in the step (1). A feature of the third invention that achieves the above object is a charged particle.
Injects and accelerates a child beam, and configures an accelerator during the acceleration
The intensity of the magnetic field of the electromagnet is set to the first value when the charged particle beam is emitted.
Increase to the magnetic field strength, after which the charged particle beam
Light is emitted, and the magnetic field strength of the electromagnet is
After the beam is emitted, when the electromagnet is used at a maximum magnetic field strength or higher,
Increase to a certain second magnetic field strength, and then
An operation method of an accelerator for performing demagnetization, wherein the incidence, the
Operate by repeating the operation cycle including acceleration and the emission
Charged particle beam emitted during a certain operation cycle
Energy from the load emitted during the previous driving cycle
When the energy is different from the electron beam, the former and the latter
Of the increase of the magnetic field strength up to the first magnetic field strength in the operation cycle of
Is to make the same .

[0009]

[Action] The first invention is a magnetic field strength of the electromagnet, the decrease磁前after extraction of the charged particle beam, the use of the electromagnet top
Since the demagnetization is performed after the magnetic field intensity is increased to a value higher than or equal to the large magnetic field intensity , the initialization operation becomes unnecessary, and the operating rate of the accelerator can be increased. The second invention is directed to the energy of the emitted charged particle beam.
In different operation cycles,
When the operation is performed with the energy of the emitted charged particle beam changed, the operation can be continued without the initialization operation in order to increase to the maximum magnetic field intensity to be used. The third invention operates by repeating an operation cycle including the incidence, acceleration, and emission , and
Of the charged particle beam emitted in the different operation cycle
Is the charged particle beam emitted in the previous operation cycle
The former and latter driving cycle
The same increase rate of the magnetic field strength up to the first magnetic field strength.
Since that can simplify the control system.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. First, the principle of the present invention will be described. In general, an electromagnet includes a magnetic body typified by a laminated iron plate, an exciting coil, and the like. The magnetic material draws a hysteresis ring (magnetic hysteresis curve) as shown in FIG. 2 with the excitation. As the electromagnet current increases, the magnetic field H increases, and the magnetic field H is excited from the origin 0 to the point a in the figure. Thereafter, when the current is reduced, demagnetization is performed from point a to point b. However, even if the current is returned to 0, the magnetic field does not become 0 and has a certain value Br determined by the magnetic material. This is called residual magnetization or residual magnetic flux density.

With reference to FIG. 3, consider the operation of the accelerator at the time of constant energy emission based on the conventional operation pattern.
The operation is performed by repeating “injection → acceleration → exit → demagnetization” as one operation cycle as necessary.
The magnetic history of the electromagnet for each operation is schematically shown in the lower part of FIG. In the first operation, the magnetic body moves on the initial magnetization curve from the origin 0 to the point a in FIG. 2 and returns to the residual magnetization Br. From the second time, a magnetic history is obtained in which the excitation is started from Br to B2 and then returns to Br again.

Therefore, an operation for stabilizing the magnetic history of the electromagnet, that is, an initialization operation is required before the beam is actually accelerated. Then, the excitation amount B2 when the operation pattern is emitted
Since the electromagnets have the same magnetic history unless the value is changed, the beam can be repeatedly accelerated and emitted with the same energy.

Next, referring to FIG. 4, what happens when the electromagnet excitation amount at the time of emission is changed between the operation cycles n-1 and n is considered. In this case, the magnetic histories in n-1 and n cycles are shown in the lower part of FIG. 4, respectively. n-1 cycles and n
In the cycle, since the excitation amounts (B2 and B3) at the time of emission are different, the magnetic history changes. That is, the residual magnetization changes from Br to Br '. Thereby, the residual magnetization at the end of n cycles changes.

Accordingly, the exciting current corresponding to the (n + 1) th or later incident energy is changed from I1 (H1) to I2 in FIG.
(H2), and the beam cannot be incident. Therefore, after the n + 1 cycle, the beam is accelerated
It cannot be emitted. To avoid this, a new initialization operation is required before starting n cycles. Therefore, the utilization rate of beam utilization is greatly reduced.

The residual magnetization is determined by the magnetic field H applied to the electromagnet.
, Ie, proportional to the amount of exciting current. Therefore, in the embodiment of the present invention to be described later, regardless of the magnitude of the excitation amount at the time of emission, before the electromagnet is "demagnetized" in each operation cycle, for example, a certain value or saturation of the maximum magnetic field used by the electromagnet or more. The magnetic field demagnetizes after re-excitation once, regardless of the presence or absence of the beam in the accelerator. This allows
The magnitude of the residual magnetization can be kept constant.

Therefore, even when the amount of excitation is different as shown in FIG. 4, the operation can be continued without the initialization operation. This situation is schematically shown in FIG. After the first cycle, the residual magnetic field of the electromagnet becomes Br. From the second cycle onward, the magnetic history different from that of the first cycle changes with this Br as a start point and an end point. At this time, even if the magnetic field for emitting the beam is fixed at a magnetic field different from B1 or B2, in both cases, if the electromagnet is demagnetized after being re-excited to a certain magnetic field Bmax selected to reproduce Br, It is possible to always keep the residual magnetic field Br constant. Therefore, even if the magnetic field at the time of beam emission is changed, the operation rate of the beam can be increased without the need for the initialization operation.

FIG. 1 is a diagram showing an operation pattern in a particle accelerator according to one embodiment of the present invention. FIG. 1 shows an operation method in which after the beam is emitted, the electromagnet is re-excited to its saturation magnetic field and then demagnetized so that the effect of the invention is maximized. The excitation amount of the electromagnet corresponding to the energy of the incident beam is Binj, the first emission energy is B1, the second emission energy is B2, and the saturation magnetic field of the electromagnet is Bmax.

The electromagnet is first excited by Binj and waits for an incident beam. Thereafter, while the beam is circulated in the circular accelerator at this excitation amount, a voltage is generated in the high-frequency acceleration cavity placed in the circular accelerator to capture the beam and prepare for acceleration. After the capture is completed, while gradually increasing the excitation amount of the electromagnet from Binj to B1, and adjusting the voltage and phase of the accelerating cavity according to the change in the excitation amount of the electromagnet, on a stable orbit in the accelerator. The ion energy is gradually increased, that is, an acceleration operation is performed.

When the excitation amount reaches B1, the excitation amount is fixed and the emission operation is started. After the emission is completed, the excitation amount of the electromagnet is re-excited again from B1 to the saturation magnetic field Bmax. After the magnetic field generated by the electromagnet becomes the saturation magnetic field, it is demagnetized. Thereafter, the magnetic field is raised to the incident magnetic field Binj, and the next incidence is performed.

The operation of the accelerator system is executed by repeating the above operation cycle. In this operation, since the maximum magnetic field experienced by the electromagnet is not the magnetic field B1 or B2 that actually emits the beam but the saturation magnetic field Bmax, the residual magnetization Br at the end of the demagnetization is B1 or B2. The value is constant regardless of. Therefore, the beam emission energy, that is, the emission magnetic field of the electromagnet and the flat top magnetic fields B1 and B2 can be easily changed for each operation cycle.

FIG. 6 is a block diagram of a medical ion synchrotron system. The medical synchrotron system includes a pre-accelerator 100, an incident beam transport system 200, a synchrotron 300, an output beam transport system 400, and an irradiation room 500. Ion beam 10 generated by the pre-accelerator 100
Is shaped and shaped by the incident beam transport system 200, enters the synchrotron 300, is accelerated by the synchrotron 300 to a desired energy, and is emitted. The emission beam transport system 400 transports the beam 10 emitted from the synchrotron 300 to the irradiation chamber 500 while shaping. And
In the irradiation room 500, the affected part of the patient is irradiated.

In medical applications, the affected part of a patient is irradiated three-dimensionally. That is, in addition to irradiation in a plane perpendicular to the beam traveling direction, irradiation in the beam traveling direction, that is, in the depth direction is important. This irradiation is performed by changing the energy of the ion beam from the synchrotron for each operation cycle. A method for realizing this operation method will be described below.

FIG. 7 is a timing chart of the irradiation operation. Pre-accelerator 100, beam transport system for input and output 200, 40
0, each of the synchrotrons 300 performs an initializing operation, and the deflection magnet 301 and the quadrupole magnet 302 in the synchrotron 300
And other magnetic histories. After that, the beam transport system for incidence
200 stands by at the excitation amount of the electromagnet corresponding to the incident energy. Next, the pre-accelerator 100 is turned on, and the ion beam 10
Generate. The ion beam 10 is incident on the synchrotron via the beam transport system 200 using an incident system device (for example, configured with the inflector 303, the incident bump electromagnet 304, and the like).

The incident ion beam receives an accelerating electric field by the accelerating cavity 305 while increasing the excitation amount of the electromagnet, receives synchrotron acceleration to a desired energy, and is fixed at the energy. After being fixed to a desired energy, for example, synchronized with a patient's breathing or synchronized with a fixed time interval, an output radio frequency source installed in a synchrotron
The beam 306 and the resonance excitation magnet 309 are used to increase the betatron amplitude of the beam, and the emission device (for example, the emission deflector 30)
7. Emission bump electromagnet 308 and the like. ). The extracted particles are used as an emission beam transport system that has been waiting in advance with the excitation amount corresponding to the energy.
The 400 guides the patient to the irradiation room 500 where the patient is fixed.

When all ions orbiting the synchrotron 300 have been emitted or the required irradiation amount has been secured, the emission high-frequency source 306 is turned off to stop beam emission. Thereafter, the electromagnet group of the synchrotron is re-excited by the pattern operation up to the excitation amount selected to match the residual magnetization. At this time, similarly to the synchrotron, the emission beam transport system 400 is re-excited by the set value operation up to an arbitrary excitation amount selected in order to align the residual magnetization. After the re-excitation, the electromagnet of the synchrotron is demagnetized by the set value operation in which the set value of the electromagnet of the beam transport system is set to 0 according to the determined demagnetization pattern. After the end of the demagnetization, the electromagnet of the beam transport system receives the set value corresponding to the beam energy in the next operation cycle, excites the electromagnet group, and waits for beam emission.

As described above, the operation of the output beam transport system, which was considered to be essential for pattern operation as in the case of the conventional synchrotron, is changed to the operation of only the set value operation even when the energy changes for each operation cycle. The emitted beam can be transported to the irradiation chamber. Further, since the operation of the beam transport system is only the set value operation, the control device can be greatly simplified and the cost can be reduced.

In the embodiment shown in FIGS. 6 and 7, the particle beam orbiting the synchrotron is emitted with its betatron amplitude increased to exceed the stability limit, but the present invention employs such an emission method. The method is not limited to the case of applying to a synchrotron, and an extraction method by another method, for example, a method of applying a high-speed deflection magnetic field to a circulating particle beam to remove all particles from the orbit in a short time and emit it. It goes without saying that the present invention can be applied to the synchrotron to be employed. In the present invention, the particle beam is emitted by the magnetic fields B1 and B2 as shown in FIG. 1. At the time of the emission, the emission method and the operation method according to the present invention can maintain the excitation amount of the electromagnet group constituting the synchrotron almost constant. It is preferable to combine Incidentally, Japanese Patent Application Laid-Open No. 5-1 previously proposed by the inventors of the present application relates to a method of emitting a particle beam.
No. 98397.

Next, a method of changing the energy for each operation cycle will be described with reference to FIGS. First, as shown in FIG. 8, a pattern for accelerating up to the maximum excitation amount used in the accelerator system is generated, and it is established that the ion beam can be surely accelerated by this pattern. Next, a plurality of excitation amounts used in one operation are set as B1 and B2. In order to keep the emission time at each emission energy constant, the flat top at Bmax in FIG. 8 is translated in parallel with the acceleration gradient. By this operation, an acceleration pattern between B1 and B2 can be generated.
Then, a re-excitation pattern from B1 or B2 to Bmax is generated with the same gradient.

Finally, a demagnetization pattern between Bmax and Binj is generated. In this manner, pattern data corresponding to a new emission energy can be generated based only on the pattern data capable of reliably accelerating and emitting the beam, only by translating and exchanging the data. In addition, since it is only translation and replacement, if a memory duplex device such as a butterfly memory is used for the pattern data transmission device,
The next data can be stored in the memory while sending the data, and the emission energy can be easily changed for each operation cycle, that is, for each pulse. Further, since the acceleration gradient is constant at any energy, the control data can be reduced, and the control device can be simplified and the cost can be reduced.

[0030]

According to the first aspect, the initialization operation is not required.
Therefore, the operating rate of the accelerator can be increased. According to the second invention
Operation with changing the energy of the emitted charged particle beam
, The operation can be continued without the initialization operation. Third
According to the invention, the control device can be simplified .

[Brief description of the drawings]

FIG. 1 is an operation pattern diagram showing an operation method according to an embodiment of the present invention.

FIG. 2 is a magnetic hysteresis curve graph.

FIG. 3 is an explanatory diagram of a constant energy operation according to a conventional operation method.

FIG. 4 is an explanatory diagram when energy is changed by a conventional operation method.

FIG. 5 is a diagram showing a state of a magnetic history when the driving method shown in FIG. 1 is applied.

FIG. 6 is a configuration diagram of a particle accelerator according to one embodiment of the present invention.

7 is an acceleration operation time chart of the particle accelerator shown in FIG.

FIG. 8 is a basic pattern diagram of an operation method according to another embodiment of the present invention.

9 is a diagram illustrating a method of generating an arbitrary pattern by the driving method shown in FIG.

[Explanation of symbols]

Reference Signs List 10: ion beam, 100: pre-accelerator, 200: incident beam transport system, 300: synchrotron, 301: deflecting magnet, 302: quadrupole magnet, 303: inflector, 3
04 ... Bump electromagnet for incidence, 305 ... Acceleration cavity, 306
... High-frequency source for output, 307… Deflector for output, 308
... Bump electromagnet for emission, 309 ... Resonance excitation magnet, 40
0: outgoing beam transport system, 500: irradiation room.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Matsuda 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Energy Research Laboratory, Hitachi, Ltd. (56) References JP-A-5-198394 (JP, A) JP-A-1-232700 (JP, A) JP-A-63-307700 (JP, A) JP-A-2-304906 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05H13 / 04 A61N 5/10 H01F 13/00 G21K 1/08-1/093

Claims (7)

(57) [Claims] 1. An accelerator operating method for injecting, accelerating and emitting a charged particle beam, and demagnetizing an electromagnet used in the accelerator after the emission, comprising the steps of:
A method of operating an accelerator, comprising: increasing the intensity of a magnetic field used by the electromagnet to be equal to or higher than the maximum magnetic field intensity used after the emission of the charged particle beam and before the demagnetization, and thereafter performing the demagnetization. 2. An accelerator operating method for injecting, accelerating and emitting a charged particle beam, and demagnetizing an electromagnet used in the accelerator after the emission, comprising:
A method for operating an accelerator, comprising: increasing the saturation magnetic field strength of the electromagnet after the emission of the charged particle beam and before the demagnetization, and thereafter performing the demagnetization. 3. The method according to claim 2 , wherein said input, said acceleration, said output, and said output.
Repeatedly increasing the magnetic field strength after irradiation and demagnetizing
3. The method for operating the accelerator according to claim 1, wherein the accelerator is rotated. Wherein said incident, the acceleration, the emission, increase of the magnetic field strength after the emission, and driving support including the demagnetization
When driving a vehicle repeatedly,
Energy of the charged particle beam emitted from the
Of the charged particle beam emitted in the operation cycle of
3. The method for operating the accelerator according to claim 1, which is different from the method of claim 1 . 5. A charged particle beam is incident, accelerated, and applied.
When the speed is high, the magnetic field strength of the
Increase to the first magnetic field strength at the time of beam emission, and then
Emitting the charged particle beam, the magnetic field strength of the electromagnet
After the emission of the charged particle beam, the
Increase to a second magnetic field strength that is greater than or equal to the maximum magnetic field strength for
Then, the method of operating the accelerator for demagnetizing the electromagnet is performed.
Thus, the rate of increase of the magnetic field strength up to the first magnetic field strength,
Magnetic field strength from the first magnetic field strength to the second magnetic field strength
A method of operating an accelerator, wherein the rate of increase of the accelerator is the same . 6. A charged particle beam is incident, accelerated, and applied.
When the speed is high, the magnetic field strength of the
Increase to the first magnetic field strength at the time of beam emission, and then
Emitting the charged particle beam, the magnetic field strength of the electromagnet
The degree, after emission of the load electric particle beam, use of the electromagnet
Increase to a second magnetic field strength that is greater than or equal to the maximum magnetic field strength for
Then, the method of operating the accelerator for demagnetizing the electromagnet is performed.
Thus, an operation site including the entrance, the acceleration, and the exit
Operate the vehicle repeatedly and emit in a certain operation cycle
The energy of the charged particle beam
Different from the energy of the charged particle beam emitted by the
In the case of the former and latter driving cycles, up to the first magnetic field strength
A method of operating the accelerator, wherein the rate of increase in the magnetic field strength of the accelerator is the same . 7. The method according to claim 7, wherein the second magnetic field strength is determined by the saturation of the electromagnet.
7. The method for operating the accelerator according to claim 5, wherein the accelerator is a magnetic field intensity .