JP2019039702A - Charged particle beam generation device, particle beam therapy equipment equipped with the same, and operation method of charged particle beam generation device - Google Patents

Abstract

To provide a charged particle beam generation device capable of reducing undesired stoppage of the device while, compared to conventional, constantly maintaining a beam current emitted from a straight line accelerator with a simple constitution, a particle beam therapy equipment equipped with the same, and an operation method of charged particle beam generation device.SOLUTION: The charged particle beam generation device comprises: an ion source 2; a pull-out electrode system 5; an electrostatic lens 7 for focusing a pull-out beam 14; a straight line accelerator 9 for accelerating the pull-out beam 14; a beam current detection unit 10 for detecting a beam current of an output beam 11 or the pull-out beam 14 after having passed the electrostatic lens 7; and a control unit 13 configured to control the voltage to be applied to the electrostatic lens 7 depending on the beam current detected the beam current detection unit 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a charged particle beam generator, a particle beam therapy apparatus including the same, and a method for operating the charged particle beam generator.

  As a background art in this technical field, there is a technique described in Patent Document 1. Patent Document 1 states that “the extraction electrode is a negative electrode as a beam transport device capable of transporting a large current beam with high beam utilization efficiency even in a long transport section while using an inexpensive and simple electrostatic lens. The electrostatic lens has a decelerating electrode to which a voltage is applied, and the electrostatic lens is negative between the beam incident side electrode and the central electrode to which a positive voltage is applied, and between the central electrode to which a positive voltage is applied and the beam emission side electrode. It has two electron suppression electrodes to which a voltage is applied. The deceleration electrode and the electron suppression electrode play a role in retaining electrons in the transport section, etc., and the beam space charge is effectively neutralized to suppress beam divergence. It is described.

JP 2005-235697 A

  In a ring-shaped circular accelerator such as a synchrotron, a charged particle beam generator for accelerating / injecting charged particles is used as a preceding stage.

  A charged particle beam generator for particle beam therapy accelerates charged particles generated by an ion source, accelerates them to a predetermined energy, and then emits them to a circular accelerator. Particles accelerated to a higher energy by a circular accelerator are used for particle beam therapy in which a charged particle beam is irradiated onto an affected part of a patient such as cancer.

  In a charged particle beam generator connected to a circular accelerator for particle beam therapy, an electrostatic lens for extracting and focusing from a charged particle beam plasma having a positive charge is provided.

  As an example of such an electrostatic lens, there is a technique described in Patent Document 1 described above.

  However, in the electrostatic lens described in Patent Document 1, it is necessary to add two negative electrodes and a high-voltage power supply to the commonly used electrostatic lens composed of three electrodes.

  This complicates the structure of the electrostatic lens and increases the distance from the ion source to the DC accelerator, resulting in a longer beam line. Furthermore, there was a problem that the addition of a high-voltage power supply would lead to an increase in cost.

  In addition, there is a problem that the effect of suppressing electrons generated by colliding with the residual gas in the electrostatic lens is small, and it is difficult to completely suppress the decrease in the output beam current.

  An object of the present invention is to provide a charged particle beam generator capable of maintaining an emitted beam current constant as compared with the prior art and suppressing unnecessary apparatus stop as compared with the prior art even with a simple configuration. It is to provide a particle beam therapy system including the same and a method of operating a charged particle beam generator.

  The present invention includes a plurality of means for solving the above-described problems. For example, an ion source for generating ions, and an extraction electrode for extracting the ions from the ion source to form a charged particle beam. A system, an electrostatic lens for focusing the charged particle beam extracted by the extraction electrode system, a linear accelerator for accelerating the charged particle beam, and a beam current of the charged particle beam after passing through the electrostatic lens And a control unit that controls a voltage applied to the electrostatic lens in accordance with a beam current detected by the current detector.

  According to the present invention, even with a simple configuration, it is possible to keep the beam current emitted from the linear accelerator constant compared to the prior art and to suppress unnecessary apparatus stop compared to the prior art.

It is a figure which shows the outline of the charged particle beam generator of Example 1 of this invention. It is a figure which shows the outline of the apparatus operation | movement timing at the time of the charged particle beam emission of the charged particle beam generator of Example 1. FIG. 2 is a control flow diagram of the charged particle beam generator according to Embodiment 1. FIG. It is a figure which shows the outline of the charged particle beam generator of the modification of Example 1 of this invention. It is a figure which shows the outline of the voltage drop of the electrostatic lens in the charged particle beam generator of Example 1. FIG. It is a figure which shows the outline of the charged particle beam generator of Example 2 of this invention. 6 is a control flow diagram of a charged particle beam generator according to Embodiment 2. FIG. It is a figure which shows the outline of the particle beam therapy apparatus of Example 3 of this invention.

  Embodiments of a charged particle beam generator of the present invention, a particle beam therapy apparatus equipped with the same, and a method for operating the charged particle beam generator will be described below with reference to the drawings.

<Example 1>
Embodiment 1 of a charged particle beam generator and its operating method according to the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic diagram showing the configuration of a charged particle beam generator according to the present embodiment. FIG. 2 is a diagram showing an outline of device operation timing when a charged particle beam is emitted and an outline of voltage drop of the electrostatic lens due to plasma ignition delay. FIG. 3 is a control flow diagram of the charged particle beam generator.

  As shown in FIG. 1, the charged particle beam generator 1 includes an ion source 2, a vacuum vessel 4, an extraction electrode system 5, an electrostatic lens 7, a linear accelerator 9, a beam current detector 10, An electrolens power supply 8, a control unit 13, a deceleration power supply 16, and a drawing power supply 15 are configured.

  The ion source 2 generates a plasma 3 as a source of a beam to be extracted. The type includes, for example, a microwave ion source, an ECR (Electron Cyclotron Resonance) ion source, a duoplasmatron, and the like, and any ion source can be used. In this embodiment, an example in which a microwave ion source is employed will be described.

  The plasma 3 is generated by a magnetic field in the direction of the extraction beam 14, a sample gas such as hydrogen, helium, carbon, and oxygen, and microwaves. In this case, the frequency of the microwave is, for example, 2.45 GHz.

  The extraction electrode system 5 is an electrode system for obtaining an extraction beam 14 by extracting ions from the plasma 3 generated by the ion source 2, and three or more electrodes having one or more holes are arranged side by side. .

  As shown in FIG. 1, the extraction electrode system 5 of this embodiment includes an extraction electrode 5 a in contact with the ion source 2, and a deceleration electrode 5 b and a ground electrode 5 c that are installed at a certain distance from the extraction electrode 5 a in order. It is composed of a single electrode.

  A positive potential is applied to the ion source 2 and the extraction electrode 5a by the extraction power source 15, and a negative potential is applied to the deceleration electrode 5b by the deceleration power source 16. The ground electrode 5c is set to the ground potential (0V). Depending on the specifications of the linear accelerator 9, the extraction power supply 15 is, for example, 30 kV, and the deceleration power supply 16 is, for example, -2 kV.

  The electrostatic lens 7 is a lens that focuses the extraction beam 14 extracted by the extraction electrode system 5, and is composed of three electrodes, that is, an incident side electrode 7a, a central electrode 7b, and an emission side electrode 7c. A hole through which the extraction beam 14 passes is provided at the center of each of the three electrodes.

  In the electrostatic lens 7, the incident-side electrode 7a and the emission-side electrode 7c at both ends are ground potential, and the central electrode 7b is positive potential.

  When the center electrode 7b has a positive potential, it is called a deceleration-acceleration mode. In focusing in the deceleration-acceleration mode, the beam spreads by receiving a divergence force between the incident side electrode 7a and the central electrode 7b due to the electric field distribution shape.

  On the other hand, a focusing force is received between the center electrode 7b and the emission side electrode 7c. Here, since the extraction beam 14 is positively charged, the velocity is high at the incident side electrode 7a, the velocity is decelerated near the central electrode 7b, and the velocity of passing through is slow. However, the beam is accelerated again by the emission side electrode 7c, and the beam speed is increased. For this reason, the time for passing through the vicinity of the central electrode 7b is longer than that in the vicinity of the incident side electrode 7a and the outgoing side electrode 7c, and the positively charged beam is repelled by the influence of the positive potential, that is, receives a strong focusing force.

  With such a mechanism, the electrostatic lens 7 functions as a focusing lens as a whole.

  In this embodiment, the potential of the central electrode 7 b of the electrostatic lens 7 is adjusted by the control unit 13 by detecting the current value of the outgoing beam 11 by the beam current detector 10.

  The extraction electrode system 5 and the electrostatic lens 7 are disposed in the vacuum vessel 4 and are kept in a vacuum.

  The linear accelerator 9 is an accelerator for accelerating the extraction beam 14. For example, the linear accelerator 9 is a high-frequency accelerator such as RFQ (Radio Frequency Quadrupole), DTL (Drift Tube Linac), or the like. Or it can be set as electrostatic accelerators, such as a cockcroft Walton type and a Van de Graaff type.

  The beam current detector 10 is installed on the downstream side of the linear accelerator 9 and is a detector such as a non-contact type CT (Current Transformer) that detects the beam current of the outgoing beam 11 accelerated by the linear accelerator 9. .

  The control unit 13 calculates the variation of the outgoing beam current detected by the beam current detector 10, determines the voltage to be applied to the electrostatic lens 7, and sets the value in the electrostatic lens power supply 8. The control unit 13 is composed of, for example, a CPU, ROM, RAM, and the like in the PC, and can exist as a single control unit 13. In addition, the charged particle beam generator 1 is incorporated into a control device (not shown) or a control device of a device (for example, a particle beam therapy device) in which the charged particle beam generator 1 is incorporated as shown in FIG. Can do.

  The control unit 13 includes a display unit 23 that displays various control parameters such as the beam current value detected by the beam current detector 10, the waveform of the voltage applied to the electrostatic lens 7, and the voltage value.

  The circular accelerator 12 on which the outgoing beam 11 is incident is various types of accelerators such as a cyclotron, a synchrocyclotron, and a synchrotron.

  Next, operations and problems for obtaining the outgoing beam 11 will be described with reference to FIG. FIG. 2 shows an example of using a microwave ion source as the ion source 2 and extracting a pulse beam. In FIG. 2, the vertical axis indicates the beam extraction trigger and the beam request trigger, the microwave power applied to the ion source 2, the current value of the extraction beam 14, the voltage of the electrostatic lens 7, and the electrostatic lens 7 in order from the top. The current value, the output current value of the linear accelerator 9 and the output value of the electrostatic lens power supply 8 are all represented on the horizontal axis.

  As described above, the extraction beam 14 is extracted from the ion source 2 by the extraction electrode system 5. The extracted extraction beam 14 is generally a diverging beam, and in order to enter the linear accelerator 9, it is necessary to shape this beam into a focused beam so that it does not hit an electrode or the like in the linear accelerator 9. Furthermore, it is necessary to shape the beam shape so that it can pass through the linear accelerator 9. For this reason, a focusing mechanism such as an electrostatic lens 7 composed of three electrodes is required.

  Beam extraction from the ion source 2 is performed as follows. A sample gas is introduced into the vacuumed ion source 2 and a magnetic field is applied. A predetermined voltage is applied to the extraction electrode system 5 and the electrostatic lens 7.

  Thereafter, when a beam extraction trigger is received and microwave power is applied to the ion source 2, electrons floating in the ion source 2 cause a circular motion by the microwave and the magnetic field, and collide with the introduced sample gas. Plasma 3 is generated. Thereafter, the generation of electrons due to collision increases and the generation of the plasma 3 accelerates, so that the current value of the extraction beam 14 from the ion source 2 gradually increases. Although the increase time depends on the microwave power, it is several tens to several hundreds of microseconds, for example.

  At this time, the divergence angle of the beam changes from large to small in accordance with the extracted beam current. Further, the beam temporarily collides with the incident side electrode 7a and the like of the electrostatic lens 7 and secondary electrons are generated. When these secondary electrons flow into the center electrode 7b of the electrostatic lens 7, a current flows through the deceleration power source 16, and the voltage of the electrostatic lens 7 temporarily decreases. The voltage drop of the electrostatic lens 7 depends on the internal circuit constant of the power source.

  After a beam extraction trigger, a beam request trigger is received after a certain period of time, a high frequency or the like is applied to the linear accelerator 9 to generate an electric field for acceleration, and an outgoing beam 11 is obtained. If the current of the extraction beam 14 is constant, the change in the voltage waveform of the electrostatic lens 7 between the pulse beams becomes small.

  Here, the experiment of the present inventor has revealed that the generation of electrons necessary for ignition is not constant due to a change in the state of the surface of the ion source 2 in contact with the plasma 3 and the ignition delay of the plasma 3 occurs. . It has also been clarified that this is particularly conspicuous when a microwave ion source or an ECR ion source that has a long lifetime and can improve the maintenance cycle and operating rate is used for the ion source 2. The outline of the waveform at that time is shown by a broken line in FIG.

  This ignition delay does not change with each pulse, but depends on the operation time, and is irregularly and unstablely generated until the cleanness of the surface inside the ion source 2 becomes high. The ignition delay time is, for example, about several tens of nanoseconds.

  When such an ignition delay occurs, the change in the extracted beam current drawn at the timing of the beam request trigger is small, but the voltage variation of the electrostatic lens 7 occurs as shown by the broken line in FIG. As a result, the focusing property at the electrostatic lens 7 deteriorates, the beam transmittance at the linear accelerator 9 decreases, and the current of the outgoing beam 11 changes. The voltage fluctuation is a transient phenomenon, for example, within a few tens to several hundreds of microseconds. Although it is possible to employ a power supply having a circuit that can solve this problem, it is not practical because it is very expensive.

  On the other hand, in order to make the current of the outgoing beam 11 constant, it is conceivable to increase the generation amount of the plasma 3 that determines the extraction beam amount. In order to increase the amount of plasma 3 generated, it is conceivable to adjust the conditions of the ion source 2 such as microwave power and gas flow rate.

  However, when the generation amount of the plasma 3 is increased, the divergence angle of the extraction beam 14 determined by the extraction electrode 5a and the deceleration electrode 5b, the size of the holes provided in these electrodes, and the plasma density that varies depending on the conditions of the ion source 2 is obtained. Therefore, the collision of particles with the electrostatic lens 7 due to the divergence of the extraction beam 14 increases, and the voltage drop of the electrostatic lens 7 due to the increase of secondary electrons and the damage of the electrostatic lens 7 occur more. Thus, the life of the electrostatic lens 7 may be shortened.

  Here, even if an ignition delay occurs, as shown in FIG. 2, the current of the extraction beam 14 at the extraction beam extraction timing does not change. Therefore, adjusting the voltage applied to the electrostatic lens 7 does not change the beam collision amount to the electrostatic lens 7 due to the change of the extraction beam current, and the secondary electron inflow to the electrostatic lens 7 does not change. For this reason, the present inventor has revealed that the controllability is good and a stable outgoing beam can be extracted. Further, it has been clarified that the damage of the electrode of the electrostatic lens 7 due to the collision of the extraction beam 14 can be reduced. The control of the voltage applied to the electrostatic lens 7 is effective because it can cope with a decrease in the voltage of the electrostatic lens 7 due to the influence of secondary electrons as described above even when the extraction beam current changes. Act on.

  Next, the operation of the charged particle beam generator 1 in FIG. 1 will be described.

  First, the extraction beam 14 is obtained from the plasma 3 generated by the ion source 2 by the extraction electrode system 5 including the extraction electrode 5a, the deceleration electrode 5b, and the ground electrode 5c. After that, the extraction beam 14 is shaped by the electrostatic lens 7 composed of the three electrodes of the incident side electrode 7a, the central electrode 7b, and the emission side electrode 7c, and further accelerated by the linear accelerator 9, and then the output beam 11 is obtained. The light enters the circular accelerator 12.

  After measuring the current of the outgoing beam 11 with the beam current detector 10 and calculating the necessary difference with the outgoing beam 11 with the control unit 13, if it has changed, the set value of the electrostatic lens power supply 8 is changed to reduce the static current. The voltage applied to the electric lens 7 is adjusted.

  Next, the flow of control by the controller 13 during operation will be described with reference to FIG. The controller 13 continues to execute the flow control as shown in FIG. 3 while the charged particle beam generator 1 is in operation.

  First, the control unit 13 receives an input of a beam current measurement result from the beam current detector 10 (step S11).

  Next, the control unit 13 calculates whether the output beam current value detected by the beam current detector 10 changes with respect to the beam current value required by the circular accelerator 12, and the amount of change is set in advance. It is determined whether it is within the allowable range (step S12).

  If it is determined in step S12 that the value is within the allowable range, the process ends. On the other hand, if it is determined that it is not within the allowable range, the process proceeds to step S13.

  Next, the control unit 13 adds the voltage dV corresponding to a set increase amount to the current electrostatic lens voltage and sets it to the electrostatic lens power supply 8, or reduces the voltage dV corresponding to the decrease amount to reduce the electrostatic lens. The power source 8 is set (step S13).

  According to the test, when the outgoing beam current is higher than the set value, the voltage is increased. Conversely, when the output beam current is lower than the set value, the voltage is decreased. As an increase or decrease, for example, when the voltage is about 30 kV, the voltage to be increased is 0.2 to 0.4 kV.

  Thereafter, the process ends.

  Next, the effect of the present embodiment will be described.

  The charged particle beam generator 1 according to the first embodiment described above includes the ion source 2, the extraction electrode system 5, the electrostatic lens 7 that focuses the extraction beam 14 extracted by the extraction electrode system 5, and the extraction beam 14. In accordance with the beam current detected by the beam current detector 10, the linear current accelerator 9 that accelerates, the beam current detector 10 that detects the beam current of the extraction beam 14 or the outgoing beam 11 after passing through the electrostatic lens 7, and the beam current detector 10. And a control unit 13 that controls a voltage applied to the electrostatic lens 7.

  By configuring as described above, the beam current emitted from the linear accelerator 9 can be kept constant without providing the negative electrode provided so as to sandwich the positive electrode on the electrostatic lens 7. That is, the output beam current from the linear accelerator 9 can be kept constant with a simple and low-cost configuration without changing the shape of the electrostatic lens 7. Therefore, it is possible to provide a charged particle beam generator 1 that operates stably and an operation method thereof, in which unnecessary apparatus stoppage is suppressed as compared with the conventional apparatus. Further, it is possible to cope with the change in the output beam current with respect to the voltage change of the electrostatic lens 7 due to the ignition delay of the plasma 3.

  Further, the control unit 13 keeps the beam current emitted from the linear accelerator 9 constant with higher accuracy by increasing or decreasing the voltage by a preset change amount according to the detected change amount of the beam current. And more stable operation can be realized.

  Further, by installing the beam current detector 10 on the downstream side of the linear accelerator 9, the beam current at the position closest to the beam required for the generator immediately before entering the system using the generated charged particle beam is obtained. Accordingly, the voltage applied to the electrostatic lens 7 can be controlled, and a more accurate and stable operation can be realized.

  Hereinafter, a modified example of the charged particle beam generator in the first embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic diagram showing the configuration of the charged particle beam generator according to the present embodiment. FIG. 5 is a diagram showing a voltage drop state of the electrostatic lens and a control method when the voltage of the electrostatic lens voltage drops when the ignition is delayed in the ion source.

  A charged particle beam generator 1A shown in FIG. 4 includes a voltmeter 8a that further detects the voltage of the electrostatic lens 7 in the charged particle beam generator 1 shown in FIG. Further, instead of the control unit 13, the variation of the electrostatic lens voltage set in advance is compared with the electrostatic lens voltage when the beam current that requires the electrostatic lens voltage detected by the voltmeter 8 a is obtained. Control unit 13A that controls to add an insufficient voltage when it is outside the allowable range, display unit 23 that displays the electrostatic lens voltage detected by voltmeter 8a, electrostatic lens voltage at the normal beam emission time Is stored.

  As shown in FIG. 2 and FIG. 5 described above, even when an ignition delay occurs, the rise of the extracted beam current is the same as when there is no ignition delay. Decreases with the amount of change. Further, since the beam emission time does not change, the electrostatic lens voltage at the beam emission time increases by dV.

  Therefore, each time the outgoing beam 11 is obtained, the electrostatic lens voltage is measured by the voltmeter 8a, and the controller 13A controls the voltage applied to the electrostatic lens 7 in accordance with the beam current measured by the beam current detector 10. To do. Further, in comparison with the normal electrostatic lens voltage stored in the storage unit 24, if the difference between the voltages exceeds a preset variation allowable range, the lens voltage is changed by the variation voltage dV from the stored lens voltage. Control is performed to output a signal to the electrostatic lens power supply 8 so as to raise or lower the value.

  It is possible to measure not only the voltage at the beam emission time but also the voltage waveform by the voltmeter 8a and control the voltage applied to the electrostatic lens 7 in comparison with the voltage waveform at the normal time.

  According to such control, the output beam current from the linear accelerator 9 can be kept constant with higher accuracy, and more stable operation can be realized.

  The beam current detector 10 is not limited to the configuration in which the beam current detector 10 is disposed downstream of the linear accelerator 9 and the current of the emitted beam 11 is observed, and the beam current detector 10 can be disposed immediately after the electrostatic lens 7. In this case, it is possible for the linear accelerator 9 to stop the beam emission, for example, by stopping the high frequency used for acceleration, and to stand by until a normal current value is obtained. Further, when the set beam current is not reached with several pulses, it is possible to control to stop the beam emission.

  As described above, when the voltage applied to the electrostatic lens 7 is changed, by stopping the operation of the linear accelerator 9, a more stable outgoing beam can be obtained, so that a stable operation can be realized.

  It is possible to arrange the beam current detector 10 either on the downstream side of the linear accelerator 9 or immediately after the electrostatic lens 7.

<Example 2>
A charged particle beam generator and its operation method according to Embodiment 2 of the present invention will be described with reference to FIGS. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The same applies to the following embodiments.

  The charged particle beam generator 1B of the present embodiment shown in FIG. 6 controls the voltage applied to the electrostatic lens 7 according to the degree of vacuum before and after the electrostatic lens 7, and uses a machine learning device 19. is there.

  A charged particle beam generator 1B shown in FIG. 6 includes an ion source 2, a vacuum vessel 4, an extraction electrode system 5, an electrostatic lens 7, a linear accelerator 9, a beam current detector 10, and an electrostatic lens power source. 8, a voltmeter 8 a, a control unit 13 </ b> B, a deceleration power supply 16, a drawer power supply 15, a machine learning device 19, a first vacuum gauge 17, and a second vacuum gauge 18.

  The first vacuum gauge 17 measures the degree of vacuum of the vacuum vessel 4 after the extraction electrode system 5 and before the electrostatic lens 7. The second vacuum gauge 18 measures the degree of vacuum in the linear accelerator 9.

  The extraction beam 14 is a particle having a positive charge and spreads due to the repulsive force between the particles. However, the divergence is suppressed by the electrons generated by the collision with the residual gas, but the residual gas decreases and the divergence increases as the degree of vacuum increases. For this reason, the focusing force of the electrostatic lens 7 changes, and the outgoing beam current changes.

  Although it is possible to cope with the change in the degree of vacuum in the vacuum vessel 4 by the control of the first embodiment, it is desired that the change in the degree of vacuum in the vacuum vessel 4 can be dealt with more reliably.

  Further, when the degree of vacuum in the linear accelerator 9 changes, the beam diverges due to the change in the degree of vacuum in the linear accelerator 9 even if the lens voltage is returned, and the outgoing beam current value finally changes more reliably. It is desired to perform control for suppressing the noise.

  Therefore, in the charged particle beam generator 1B of the present embodiment, the vacuum degree of the vacuum vessel 4 is measured by the first vacuum gauge 17, and the vacuum degree of the linear accelerator 9 is measured by the second vacuum gauge 18, so that the control unit 13B adjusts the voltage applied to the electrostatic lens 7 in accordance with the detected degree of vacuum and the value of the outgoing beam current.

  The machine learner 19 continuously learns the electrostatic lens voltage detected by the voltmeter 8a, and the control unit 13B applies a voltage to the electrostatic lens 7 according to the value of the voltage learned by the machine learner 19. To control. The machine learning method in the machine learner 19 is not particularly limited, and various known methods (for example, neural network, decision tree learning, correlation rule learning, genetic programming, support vector machine, Bayesian network, etc.) can be used. .

  Next, the flow of control by the control unit 13B will be described with reference to FIG. The controller 13B continues to execute the flow control as shown in FIG. 7 while the charged particle beam generator 1B is in operation.

  First, the control unit 13B receives an input of a beam current measurement result from the beam current detector 10 (step S21).

  Next, the control unit 13B receives the measurement result of the degree of vacuum by the first vacuum gauge 17 and the second vacuum gauge 18 and the measurement result of the electrostatic lens voltage by the voltmeter 8a (step S22).

  Next, the control unit 13B determines whether or not the current value input in step S21 and the degree of vacuum and electrostatic lens voltage input in step S22 are within allowable ranges (step S23). If it is determined that the value is within the allowable range, the process proceeds to step S24. On the other hand, if it is determined that it is not within the allowable range, the process proceeds to step S25.

  When it is determined in step S23 that it is within the allowable range, the control unit 13B performs machine learning using the machine learning device 19 with the measurement values of the respective parts when the emission beam current is within the set range as the normal range, Machine learning is performed in association with the degree of vacuum in the linear accelerator 9 and reflected in the subsequent set value change (step S24). Thereafter, the process ends.

  On the other hand, when it is determined in step S23 that it is not within the allowable range, the control unit 13B adjusts the voltage applied to the electrostatic lens 7 (step S25). At this time, in addition to the beam current value, the applied voltage is adjusted in consideration of the result of machine learning and the degree of vacuum. For example, when the degree of vacuum increases, adjustment such as increasing the lens voltage is performed. Thereafter, the process ends.

  Other configurations and operations are substantially the same configurations and operations as the charged particle beam generator and its operation method of the first embodiment described above, and the details are omitted.

  In the charged particle beam generator 1B and the operation method thereof according to the second embodiment of the present invention, substantially the same effects as those of the charged particle beam generators 1 and 1A and the operation method thereof according to the first embodiment can be obtained.

  Further, the controller further includes a first vacuum gauge 17 for detecting the degree of vacuum after the extraction electrode system 5 and before the electrostatic lens 7 and a second vacuum gauge 18 for detecting the degree of vacuum in the linear accelerator 9. 13B further controls the voltage applied to the electrostatic lens 7 in accordance with the degree of vacuum detected by the first vacuum gauge 17 and the second vacuum gauge 18, thereby allowing the beam to the linear accelerator 9 due to the change in the degree of vacuum. Since damage to electrodes and the like due to irradiation can be prevented, the life of the apparatus can be extended, and the effect of improving the operating rate can be obtained.

  In particular, by providing the first vacuum gauge 17 and performing control using the first vacuum gauge 17, control according to the state of the extraction beam 14 that is greatly affected by space charge due to low energy becomes possible, and a more stable outgoing beam Control becomes possible. Further, by providing the second vacuum gauge 18 and performing control using the second vacuum gauge 18, the outgoing beam control according to the change in the degree of vacuum in the linear accelerator 9 can be performed, and the outgoing beam current can be controlled more stably. .

  Further, the machine learning device 19 for continuously machine learning the voltage of the electrostatic lens 7 is further provided, and the control unit 13B further controls the electrostatic lens 7 according to the value of the electrostatic lens voltage learned by the machine learning device 19. By controlling the voltage to be applied, fluctuations in the output beam current can be suppressed more reliably.

  In the second embodiment described above, the case where all of the first vacuum gauge 17, the second vacuum gauge 18, and the machine learning device 19 are provided has been described. However, only the first vacuum gauge 17 can be provided. Similarly, it is possible to provide only the second vacuum gauge 18 and only the machine learning device 19. Furthermore, the first vacuum gauge 17 and the second vacuum gauge 18 may be provided, the first vacuum gauge 17 and the machine learner 19 may be provided, or the machine learner 19 and the second vacuum gauge 18 may be provided. .

  The machine learning device 19 can learn not only the form of machine learning of the electrostatic lens voltage detected by the voltmeter 8a but also the relationship between the electrostatic lens voltage and the outgoing beam current. By adopting such a configuration, the machine learning device 19 can be applied to the charged particle beam generators 1 and 1A of the first embodiment.

<Example 3>
A particle beam therapy system according to a third embodiment of the present invention will be described with reference to FIG.

  In FIG. 8, the particle beam therapy system 100 according to this embodiment includes a charged particle beam generator 1, a synchrotron accelerator 50, a beam transport system 51, an irradiation device 52, a treatment table 53, and a control device 56.

  The charged particle beam generator 1 is the device described in the first embodiment, and is a device that generates a charged particle beam used for treatment and accelerates it to a speed suitable for entering the synchrotron accelerator 50.

  The charged particle beam generator is not limited to the charged particle beam generator 1 shown in the first embodiment, and the charged particle beam generator 1A described in the modification of the first embodiment and the charged particle beam generator described in the second embodiment. 1B.

  The synchrotron accelerator 50 is an accelerator that further accelerates the charged particle beam accelerated to a predetermined speed by the charged particle beam generator 1 to energy suitable for irradiation. The synchrotron accelerator 50 includes a bending electromagnet, a high-frequency acceleration cavity, an emission device, and the like. Although the case of using the synchrotron accelerator 50 has been described, the accelerator may be provided with a high-frequency power supply device, and other accelerators such as a cyclotron accelerator and a synchrocyclotron accelerator may be used.

  The beam transport system 51 is connected to a synchrotron accelerator 50, and is accelerated by the synchrotron accelerator 50 and guides the emitted charged particle beam to the irradiation device 52.

  The irradiation device 52 is provided in the treatment room, and is a device for irradiating a charged particle beam. The irradiation device 52 is in two orthogonal directions in a plane perpendicular to the trajectory of the beam (hereinafter collectively referred to as a lateral direction). Are equipped with two scanning electromagnets, a beam monitor and the like that allow the beam to scan independently.

  The treatment table 53 is a bed on which a patient 54 to be irradiated with a charged particle beam is placed.

  The control device 56 controls the operation of each device and apparatus in the particle beam therapy system 100 including the synchrotron accelerator 50 described above. The control unit 13 shown in FIG. 1 is arranged in the control device 56 of the present embodiment.

  In the particle beam therapy system 100 as shown in FIG. 8, the charged particle beam generated by the charged particle beam generator 1 is further accelerated by increasing the energy by the synchrotron accelerator 50, and the irradiation device is used by using the beam transport system 51. Transported to 52. The transported charged particle beam is shaped by the irradiation device 52 so as to match the shape of the affected part, and is irradiated to a target of the patient 54 lying on the treatment table 53 by a predetermined amount.

  Since the control method and operation of the charged particle beam generator 1 are substantially the same as those in the first embodiment, the details are omitted.

  Since the particle beam therapy system according to the third embodiment of the present invention includes the charged particle beam generation apparatus according to the first embodiment described above, the beam current emitted from the linear accelerator 9 is kept constant, which is unnecessary. Device stoppage is suppressed. Therefore, stable charged particle beam irradiation is possible, and the treatment time can be shortened. In addition, operation at a low cost is possible.

<Others>
In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1,1A, 1B ... Charged particle beam generator 2 ... Ion source 3 ... Plasma 4 ... Vacuum container 5 ... Extraction electrode system 5a ... Extraction electrode 5b ... Deceleration electrode 5c ... Ground electrode 7 ... Electrostatic lens 7a ... Incident side electrode 7b ... center electrode 7c ... exit side electrode 8 ... electrostatic lens power supply 8a ... voltmeter 9 ... linear accelerator 10 ... beam current detector 11 ... exit beam 12 ... circular accelerators 13, 13A, 13B ... control unit 14 ... extraction beam 15 ... Drawer power supply 16 ... Deceleration power supply 17 ... First vacuum gauge 18 ... Second vacuum gauge 19 ... Machine learning device 23 ... Display unit 24 ... Storage unit 50 ... Synchrotron accelerator 51 ... Beam transport system 52 ... Irradiation device 53 ... Treatment table 54 ... Patient 56 ... Control device 100 ... Particle beam therapy device

Claims (15)

An ion source for generating ions;
An extraction electrode system for extracting the ions from the ion source into a charged particle beam;
An electrostatic lens for focusing the charged particle beam extracted by the extraction electrode system;
A linear accelerator for accelerating the charged particle beam;
A current detector for detecting a beam current of the charged particle beam after passing through the electrostatic lens;
A charged particle beam generation apparatus comprising: a control unit that controls a voltage applied to the electrostatic lens in accordance with a beam current detected by the current detector. The charged particle beam generator according to claim 1,
The charged particle beam generator according to claim 1, wherein the controller increases or decreases the voltage by a preset change amount according to the detected change amount of the beam current. The charged particle beam generator according to claim 1,
A voltmeter for detecting the voltage of the electrostatic lens;
The control unit is further compared with the electrostatic lens voltage when a beam current requiring the electrostatic lens voltage detected by the voltmeter is obtained, and is outside a preset lens voltage fluctuation range. A charged particle beam generator characterized by applying an insufficient voltage in the event of a failure. The charged particle beam generator according to claim 1,
A first vacuum gauge for detecting a degree of vacuum after the extraction electrode system and before the electrostatic lens;
The control unit further controls a voltage applied to the electrostatic lens according to a degree of vacuum detected by the first vacuum gauge. A charged particle beam generator. The charged particle beam generator according to claim 1,
A second vacuum gauge for detecting a degree of vacuum in the linear accelerator;
The controller further controls a voltage to be applied to the electrostatic lens according to a degree of vacuum detected by the second vacuum gauge. In the charged particle beam generator according to claim 3,
A machine learner for continuously machine learning the electrostatic lens voltage;
The controller further controls a voltage to be applied to the electrostatic lens according to the value of the electrostatic lens voltage learned by the machine learning device. The charged particle beam generator according to claim 1,
The charged particle beam generator, wherein the current detector is installed downstream of the linear accelerator. The charged particle beam generator according to claim 1,
The control unit stops the operation of the linear accelerator when changing the voltage applied to the electrostatic lens. In the charged particle beam generator according to claim 3,
A charged particle beam generator, further comprising a display unit for displaying the beam current detected by the current detector and the electrostatic lens voltage detected by the voltmeter. The charged particle beam generator according to claim 1,
The ion source is either a microwave ion source or an ECR ion source. The charged particle beam generator according to any one of claims 1 to 10,
A circular accelerator for accelerating the charged particle beam generated by the charged particle beam generator;
A beam transport system for transporting a charged particle beam accelerated by the circular accelerator;
An irradiation device for irradiating the charged particle beam transported by the beam transport system;
And a treatment table on which the charged particle beam irradiation target is placed. An ion source for generating ions; an extraction electrode system for extracting the ions from the ion source to form a charged particle beam; an electrostatic lens for focusing the charged particle beam extracted by the extraction electrode system; A linear accelerator for accelerating a charged particle beam, a current detector for detecting a beam current of the charged particle beam after passing through the electrostatic lens, and a controller for controlling a voltage applied to the electrostatic lens. A charged particle beam generator operating method comprising:
A method for operating a charged particle beam generator, comprising: controlling a voltage applied to the electrostatic lens in accordance with a beam current detected by the current detector. In the operation method of the charged particle beam generator according to claim 12,
A method for operating a charged particle beam generator, wherein the voltage is increased or decreased by a preset change amount according to a detected change amount of the beam current. In the operation method of the charged particle beam generator according to claim 12,
The method for operating a charged particle beam generator, wherein the beam current is detected downstream of the linear accelerator. In the operation method of the charged particle beam generator according to claim 12,
When the voltage applied to the electrostatic lens is changed, the operation of the linear accelerator is stopped.

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