JP2012083145A - Beam measuring apparatus and measuring method therefor, and beam transportation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily measure a momentum dispersion function and to correct the momentum dispersion function to a prescribed value.SOLUTION: The beam measuring apparatus measuring a momentum dispersion functions Dx and Dz showing, by a momentum difference, a difference of the position of a charged particle beam b in a beam transportation line 2 for transporting the charged particle beam b taken out of an accelerator 1 for accelerating charged particles up to an irradiation device for irradiating an irradiation object includes: a micro energy absorption body 11 which can be in-and-out from an orbit of the charged particle beam b in the beam transportation line 2 and allows the charged particle beam b to pass therethrough when entering the orbit of the charged particle beam b to change energy of the charged particle beam b; and momentum dispersion function measuring means 8B and S for measuring the momentum dispersion functions Dx and Dz of the charged particle beam b in the beam transportation line 2 based on the change in energy of the charged particle beam b by the micro energy absorption body 11.

Description

  The present invention relates to accelerator science, and more particularly to a beam measuring apparatus, a measuring method thereof, and a beam transport system for obtaining a momentum dispersion function that expresses a difference in position from a reference trajectory along which a charged particle beam travels using a momentum difference. .

If the X coordinate (horizontal direction) and Z coordinate (vertical direction) are provided on the plane perpendicular to the trajectory of the beam line on the beam line that transports the charged particle beam accelerated by the accelerator, the reference momentum can be obtained. There is a difference in the horizontal position between the trajectory traveled by the particle and the trajectory traveled by the charged particle having a momentum (ΔP) slightly different from the reference momentum (P), and the difference is calculated using the momentum difference. There is a momentum dispersion function (Dx) to represent. When ΔX is the difference between the positions of the trajectory, it is expressed by the following equation (1) using the momentum dispersion function Dx.
ΔX = Dx (ΔP / P) (1)

  In the above equation (1), the horizontal direction (X) is represented, but the momentum dispersion function Dz in the vertical direction (Z) is also represented in the same manner. The momentum dispersion function Dz is the same as the momentum dispersion function Dx except that the direction is different. Therefore, the momentum dispersion function Dx will be described below, and the description of the momentum dispersion function Dz will be omitted.

The charged particle beam passing through the beam transport line has a finite momentum spread on a plane orthogonal to its trajectory. From equation (1), particles with different momentum are separated from each other as the momentum dispersion function (Dx) is larger. The trajectory, that is, trajectory separated by ΔX.
Therefore, in the case of elementary particle experiments and particle beam therapy using many accelerators, when a charged particle beam is irradiated to the target (sample, tumor, etc.) at the most downstream side of the beam transport line, it is far from equation (1). In order to eliminate the trajectory (ΔX) and improve the irradiation accuracy, the momentum dispersion function (Dx) at the target position is required to be zero.

  Thus, as a method for measuring the momentum dispersion function (Dx) on the conventional beam transport line, the beam momentum is changed on the accelerator side upstream of the beam transport line, and the beam is monitored using a beam monitor or the like. There is a method of obtaining a momentum dispersion function (Dx) by measuring a change in the center of gravity of a beam on a plane perpendicular to the beam trajectory on the transport line.

T. Furukawa, et al., “Optical matching of a slowly extracted beam with transport line”, Nuclear Instruments and Methods in Physics Research A 560 (2006) 191-196

However, in the conventional method of measuring the momentum dispersion function (Dx) on the beam transport line, since the momentum of the beam is changed by the accelerator, it takes time and effort to make one measurement, and it is determined at one measurement point. It is very inconvenient to measure and adjust the momentum dispersion function (Dx) that is difficult to measure.
For example, the measurement of the change in the center of gravity of the beam takes several tens of minutes, and it takes several hours to correct the change in the momentum of the beam at the accelerator. Therefore, if the adjustment is performed three times a day by changing the energy of the particles, changing the nuclide of the particles, periodic inspection, etc., it takes too much time and cannot be put into practical use.

  In view of the above circumstances, an object of the present invention is to provide a beam measuring apparatus, a measuring method thereof, and a beam transport system capable of easily measuring a momentum dispersion function and correcting it to a predetermined value.

  In order to achieve the above object, a beam measuring apparatus according to the first aspect of the present invention is a charged particle in a beam transport line that transports a charged particle beam taken out from an accelerator that accelerates charged particles to an irradiation apparatus that irradiates an irradiation target. A beam measuring device that measures a momentum dispersion function that expresses a difference in beam position by a momentum difference, and is capable of entering and exiting the trajectory of the charged particle beam in the beam transport line and entering the trajectory of the charged particle beam A micro-energy absorber that passes the charged particle beam to change the energy of the charged particle beam, and the charged particles in the beam transport line based on the change of the energy of the charged particle beam by the micro-energy absorber Momentum dispersion function measuring means for measuring the momentum dispersion function of the beam.

  A beam transport system according to a second aspect of the present invention includes an accelerator for accelerating charged particles, a beam transport line for transporting a charged particle beam taken out from the accelerator to an irradiation device, and the beam measuring device according to the first aspect of the present invention. I have.

  According to a third measuring method of the beam measuring apparatus according to the present invention, the position of the charged particle beam in the beam transport line for transporting the charged particle beam taken out from the accelerator for accelerating the charged particle to the irradiation apparatus for irradiating the irradiation target is measured. A measurement method of a beam measuring device that measures a momentum dispersion function that expresses a difference by a momentum difference, wherein the beam measuring device includes a minute energy absorber that can enter and exit the trajectory of the charged particle beam and a momentum dispersion function measuring means. The minute energy absorber changes energy of the charged particle beam by allowing the charged particle beam to pass through when the charged particle beam is put in an orbit of the beam transport line, and the momentum dispersion function The measuring means is based on a change in energy of the charged particle beam by the minute energy absorber, and the beam transport line And we measured the momentum dispersion function of definitive the charged particle beam.

  ADVANTAGE OF THE INVENTION According to this invention, the momentum dispersion function can be measured easily, and the beam measuring apparatus which can correct | amend to a predetermined value, its measuring method, and a beam transport system are realizable.

It is the conceptual diagram which looked at the typical particle beam irradiation apparatus to which the beam measuring apparatus of embodiment which concerns on this invention is applied from upper direction. It is a longitudinal cross-sectional view along the advancing direction of the charged particle beam which shows the internal structure of the micro energy absorber replacement | exchange apparatus in the beam transport line of embodiment. It is a figure which shows the change of the momentum distribution of the charged particle beam in the beam transport line of embodiment. (a) is a figure showing the change of the beam profile observed with the 2nd beam monitor when the reference | standard momentum of the charged particle beam of embodiment changes, (b) is a position from the reference | standard momentum of a charged particle beam. It is a figure which shows difference (DELTA) X. It is a figure which shows the change (DELTA) X of the horizontal direction coordinate of the gravity center of the charged particle beam with respect to the change (DELTA) P / P of the momentum of the charged particle beam of embodiment. It is a flowchart which shows an example of the control which carries out the automatic measurement of the momentum dispersion function of the beam transport line by the beam measuring apparatus of an embodiment, and automatic correction of the momentum dispersion function within an allowable value. It is a perspective view which shows the minute energy absorption material replacement | exchange apparatus of the deformation | transformation form 1. FIG. It is a perspective view which shows the minute energy absorption material replacement | exchange apparatus of the deformation | transformation form 2. FIG.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram of a particle beam irradiation apparatus T to which a beam measurement apparatus according to an embodiment of the present invention is applied.
The particle beam irradiation apparatus (beam transport system) T is a typical particle beam irradiation apparatus to which a beam measurement apparatus is applied. The particle beam irradiation apparatus T irradiates a predetermined dose of a particle beam of charged particles such as hydrogen, helium, and carbon ion nuclei onto a sample, an affected part, or the like of an irradiation target (target).
Here, the beam measuring device obtains a momentum dispersion function (Dx, Dz) for expressing the difference in the passing positions of charged particles on a plane orthogonal to the trajectory in which the charged particles travel using a momentum difference. In this device, the momentum dispersion function Dx (Dz) is automatically corrected within the allowable value Δx (Δz).

The particle beam irradiation apparatus T includes a synchrotron 1 that accelerates charged particles to high energy and circulates as a charged particle beam, and a beam transport line 2 that transports a charged particle beam b extracted from the synchrotron 1.
In FIG. 1, the synchrotron 1 is illustrated as an example of the upstream accelerator of the beam transport line 2, but other circular accelerators, linear accelerators, and the like may be used.

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

  The synchrotron 1 includes, as main components (not shown), a high-frequency accelerating cavity that generates a high-frequency electric field applied to the charged particle beam in the synchrotron 1, a deflection electromagnet for keeping the charged particle beam traveling inside the circular orbit, A converging / diverging quadrupole magnet for converging / diverging a charged particle beam on an orbit, a beam profile of the charged particle beam in the synchrotron 1, a beam monitor for measuring a dose, and a third order of betatron oscillation of the charged particle beam A hexapolar electromagnet for separatrix generation that excites resonance and divides and forms a stable orbital region and a resonance region in the phase space, a chromocity correction hexapole electromagnet for adjusting chromaticity, and the synchrotron 1 RF (Radio Frequency)-KO (Knocko) when taking out charged particle beam to the beam transport line 2 ut) An RF-KO electrode for applying a voltage to the charged particle beam and a deflector electrode 3 for emitting the charged particle beam toward the beam transport line 2 are provided.

<Beam transport line 2>
The beam transport line 2 is a line for transporting the charged particle beam b accelerated by the synchrotron 1 to a predetermined speed and transported to an irradiation device (not shown). An irradiation device for irradiating the particle beam taken out is connected.
The beam transport line 2 has a first focusing quadrupole for converging the charged particle beam b in the beam transport line 2 from the upstream side of the pipe 2h near the synchrotron 1 and the minute energy absorber replacement device 10 constituting the beam measuring device. The electromagnet 5A, the first divergent quadrupole electromagnet 6A for diverging the charged particle beam b in the line, the first steering electromagnet 7A for correcting the trajectory of the charged particle beam b, the beam profile and the dose of the charged particle beam b are measured. And a deflection electromagnet 9 for deflecting the charged particle beam b in a predetermined direction.

  Further, the beam transport line 2 diverges the charged particle beam b emitted from the second converging quadrupole electromagnet 5B for converging the charged particle beam b emitted from the deflecting electromagnet 9 and the deflecting electromagnet 9 downstream of the deflecting electromagnet 9. The second diverging quadrupole electromagnet 6B, the second steering electromagnet 7B for correcting the trajectory of the charged particle beam b emitted from the deflecting electromagnet 9, the beam profile of the charged particle beam b emitted from the deflecting electromagnet 9, and the dose are measured. Two beam monitors (momentum dispersion function measuring means, automatic measurement control means) 8B are provided.

Further, the beam transport line 2 includes a third converging quadrupole electromagnet 5C for converging the charged particle beam b, a third diverging quadrupole electromagnet 6C for diverging the charged particle beam b, downstream of the second beam monitor 8B. A third steering electromagnet 7C for correcting the trajectory of the charged particle beam b and a third beam monitor 8C for measuring the beam profile and dose of the charged particle beam b are provided.
Control of the above-mentioned particle beam irradiation apparatus T is performed by a control means (not shown). The control means is composed of a computer, various power supply circuits, and the like.

  The beam measuring apparatus applied to the particle beam irradiation apparatus T includes a minute energy absorbing material exchanging apparatus 10 that changes the energy of the charged particle beam b at the time of measurement, and a second beam that measures the beam profile and dose of the charged particle beam b. Monitor 8B and control device for automatically measuring momentum dispersion function Dx (Dz) and controlling to automatically correct momentum dispersion function Dx (Dz) within allowable value Δx (Δz) (momentum dispersion function measuring means, automatic measurement control means) Automatic correction control means) S and first convergence / divergence quadrupole electromagnets 5A and 6A for correcting the momentum dispersion function Dx (Dz) within the allowable value Δx (Δz).

The control device S of the beam measuring device includes a computer, an interface circuit, and other circuits, and outputs a measurement control signal to the second beam monitor 8B and measures a measurement signal measured from the second beam monitor 8B. Is entered. Further, a signal for taking in and out the minute energy absorbing material 11 is transmitted from the control device S to the minute energy absorbing material replacing device 10. Further, the control device S outputs a control signal to a control circuit (correction electromagnet control means) that controls the convergence / divergence quadrupole electromagnets 5A and 6A used for automatic correction.
In addition, signals necessary for the control of the beam measuring device are input to and output from the control device S.

<Taking out the charged particle beam from the synchrotron 1 and transporting the taken out charged particle beam b in the beam transport line 2>
A large number of charged particles orbiting the orbit in the synchrotron 1 shown in FIG. 1 counterclockwise in the figure are perpendicular to the traveling direction and in the horizontal direction (parallel to the paper surface of FIG. 1: X-axis direction). Or it circulates while vibrating in the vertical direction (perpendicular to the paper surface of FIG. 1: Z-axis direction). This vibration is called betatron vibration, and the betatron vibration can be controlled by a quadrupole electromagnet for convergence / divergence in the synchrotron 1.
The particles in the synchrotron 1 are accelerated by the high frequency acceleration cavity and reach the maximum energy. Thereafter, the betatron amplitude is increased by applying an electric field based on the RF-KO voltage to the charged particle beam with the RF-KO electrode. Then, some of the many charged particles circulating around the synchrotron 1 are emitted toward the beam transport line 2 using the deflector electrode 3.

The charged particle beam b extracted from the synchrotron 1 is converged and diverged on the beam transport line 2 by the converging quadrupole magnets (5A, 5B, 5C) and the diverging quadrupole electromagnets (6A, 6B, 6C). The trajectory is deflected in a predetermined direction by the deflecting electromagnet 9, and the trajectory is corrected by the steering electromagnets (7A, 7B, 7C). Then, irradiation of a predetermined dose of the charged particle beam b is performed at a predetermined position of the irradiation target from an irradiation apparatus (not shown) to the irradiation target (target).
The beam profile and dose of the charged particle beam b in the beam transport line 2 are measured by beam monitors (8A, 8B, 8C), respectively.

<Fine energy absorber replacement device 10>
Next, the minute energy absorbing material replacing device 10 provided in the beam transport line 2 will be described.
FIG. 2 is a longitudinal sectional view along the traveling direction of the charged particle beam b showing the internal structure of the minute energy absorbing material replacing device 10 in the beam transport line 2.
The minute energy absorbing material replacement device 10 is for changing the momentum of the charged particle beam b from the reference momentum P and obtaining the momentum dispersion functions Dx and Dz expressed by the equation (1).
Therefore, the minute energy absorbing material exchanging device 10 absorbs minute energy such as a plate-shaped plastic thin film that can be taken in and out to transmit the charged particle beam b and give a momentum difference ΔP from the reference momentum P of the charged particle beam b. It has the material 11 (11a, 11b, 11c, 11d, 11e).

That is, the momentum dispersion functions Dx and Dz of the charged particle beam b in the beam transport line 2 are measured, and the minute projecting on the beam trajectory of the minute energy absorbing material replacing device 10 provided with the charged particle beam b in the beam transport line 2. By passing the energy absorbing material 11 and changing the momentum of the charged particle beam b (ΔP), the measurement can be easily performed.
The micro-energy absorber replacement apparatus 10 having the micro-energy absorber 11 is a beam monitor (8A, 8B) that measures the beam profile and dose of the charged particle beam b in the beam transport line 2 when measuring the momentum dispersion functions Dx, Dz. , 8C) and upstream of any quadrupole electromagnet (5A, 5B, 5C, 6A, 6B, 6C) for convergence / divergence used for correction. is there. The convergence / divergence quadrupole electromagnets (5A, 5B, 5C, 6A, 6B, 6C) used for correction may be any, but usually, for example, one set of convergence / divergence quadrupole electromagnets or a convergence / divergence quadrupole electromagnet Any one of these is used.

Each minute energy absorbing material 11 is located at the standby position Pa shown in FIG. 2 when the irradiation target (target) is irradiated from the actual irradiation apparatus of the charged particle beam b. Then, when measuring the momentum dispersion functions Dx and Dz, it moves to the measurement position Pb on the trajectory of the charged particle beam b shown by the solid line in FIG. 2, transmits the charged particle beam b, and changes its energy (momentum). change.
Therefore, each minute energy absorbing material 11 is configured to be movable between the standby position Pa and the measurement position Pb by using a driving device and a driving mechanism such as a hydraulic cylinder and a motor (not shown).

As each minute energy absorbing material 11, for example, in the case of a plastic thin film, a material using polyethylene or polypropylene or the main component is used. In addition, thin film glass (including silica airgel) and acrylic resin can be used. However, in principle, there are many materials that can be used as the minute energy absorbing material 11, and the material is not limited.
Each minute energy absorbing material 11 has a thickness of several hundred μm, such as 0.3 mm. However, the thickness dimension of each minute energy absorber 11 can be arbitrarily selected. Thus, the thickness and material of each minute energy absorbing material 11 (11a, 11b, 11c, 11d, 11e) can be arbitrarily selected. That is, each minute energy absorption material 11 (11a, 11b, 11c, 11d, 11e) can take the same or different material and / or the same or different thickness.

Although it is desirable that there are a plurality of minute energy absorbing materials 11, there may be only one, which is arbitrary. Moreover, when there are a plurality of sheets, the materials and thicknesses thereof may be different or the same.
For example, in the orbit of the charged particle beam b in the beam transport line 2, one minute energy absorbing material 11a is disposed as shown in FIG. 2, and two minute energy absorbing materials 11a and 11b are disposed. , 11b, 11c, four micro energy absorbers 11a, 11b, 11c, 11d, five micro energy absorbers 11a, 11b, 11c, 11d, 11e, When the absorbent material 11 is the same material and the same thickness, five kinds of change ΔP of momentum are possible.

  The minute energy absorbing material 11 (11a, 11b, 11c, 11d, 11e) of the minute energy absorbing material changing apparatus 10 shown in FIG. 2 is configured to enter and exit the trajectory of the charged particle beam b on the beam transport line 2 by linear motion. However, the minute energy absorbers 11 (11a, 11b, 11c, 11d, and 11e) may be independently rotated to enter and exit the trajectory of the charged particle beam b in the beam transport line 2.

<Momentum change ΔP of charged particle beam b and its density change>
FIG. 3 is a diagram showing a change in the momentum distribution of the charged particle beam b in the beam transport line 2. The horizontal axis represents ΔP (change in momentum) / P (reference momentum), and the vertical axis represents the density of the charged particle beam b. Have taken.
In FIG. 3, when the charged particle beam b is not transmitted through the minute energy absorbing material 11, that is, when the charged particle beam b has the reference momentum P is indicated by a broken line, and when the charged particle beam b is transmitted through the minute energy absorbing material 11, That is, a solid line indicates a case where the reference momentum P of the charged particle beam b is changed (ΔP).

For example, the charged particle beam b that has passed through the minute energy absorber 11a inserted in the trajectory of the charged particle beam b shown by the solid line in FIG. 2 loses its energy (momentum) slightly, and as shown in FIG. The reference momentum P of the beam b changes by ΔP. Due to this change in momentum ΔP, the center of gravity of the charged particle beam b observed by the second beam monitor 8B also changes from the reference momentum P to the place where the momentum has changed by ΔP (from the broken line graph to the solid line graph in FIG. 3). change).
FIG. 4A is a diagram showing a change in the horizontal beam profile observed by the second beam monitor 8B when the reference momentum P of the charged particle beam b changes by ΔP, and the horizontal axis indicates the horizontal position X. And the vertical axis represents the density of the charged particle beam b. The Dx written in FIG. 4A is a horizontal momentum dispersion function. FIG. 4B is a diagram showing a difference ΔX in the position of the charged particle beam b from the reference momentum P, where the X coordinate is a horizontal coordinate and the Z coordinate is a vertical coordinate. 4B indicates the trajectory (X = 0) of the charged particle beam b having the reference momentum P, and the solid arrow indicates the difference ΔX from the trajectory (X = 0) of the reference momentum P. The trajectory of the charged particle beam b is shown.

In FIG. 4A, the case where the charged particle beam b is not transmitted through the minute energy absorber 11a, that is, the case where the charged particle beam b is the reference momentum P is indicated by a broken line, and the charged particle beam b is transmitted through the minute energy absorber 11a. In other words, a solid line indicates a case where the reference momentum P of the charged particle beam b is changed (ΔP).
The difference in position from X = 0 (see FIG. 4B) in FIG. 4A corresponds to ΔX (see FIG. 4B) in equation (1). Therefore, ΔX at a predetermined position in the beam transport line 2 can be measured by the beam monitor (8A, 8B, 8C).
On the other hand, the reference momentum P of the charged particle beam b can be arbitrarily set by the synchrotron 1.

When the charged particle beam b is transmitted through the minute energy absorber 11a (solid line graph in FIG. 4A), the charged particle beam b is passed through the minute energy absorber 11a because it is scattered by the minute energy absorber 11a. The distribution of the charged particle beam b slightly spreads compared with the case where the transmission is not performed (the broken line graph in FIG. 4A).
As can be seen from FIG. 4A, when the change ΔP from the reference momentum P is 0 or the horizontal momentum dispersion function Dx is 0, the X coordinate (horizontal position) at the reference momentum P is the charged particle beam. It becomes the center of gravity of b.

  Therefore, if the momentum dispersion function Dx (Dz) is adjusted to zero by adjusting the converging quadrupole electromagnets (5A, 5B, 5C) and the diverging quadrupole electromagnets (6A, 6B, 6C), the momentum is applied to the charged particle beam b. Even if there is a change ΔP, the X (Z) coordinate position at the reference momentum P of the charged particle beam b becomes the center of gravity of the charged particle beam b, and the charged particle beam from the irradiation device connected to the beam transport line 2 Irradiation of the irradiation target (target) of b can be accurately performed regardless of the change ΔP or spread of the momentum of the charged particle beam b.

  Alternatively, by obtaining the value of the momentum dispersion function Dx (Dz) in the beam transport line 2, the horizontal deviation of the center of gravity of the charged particle beam b with respect to the change ΔP of the momentum with respect to the reference momentum P of the charged particle beam b (corresponding to ΔX). ) (Vertical deviation (corresponding to ΔZ)) is obtained, so that the irradiation target (target) of the charged particle beam b from the irradiation device connected to the beam transport line 2 is the reference of the charged particle beam b. It can be accurately performed by grasping the change ΔP and the spread of the momentum with respect to the momentum P.

FIG. 5 is a diagram showing a change ΔX of the horizontal coordinate X of the center of gravity of the charged particle beam b with respect to a change ΔP / P of the momentum of the charged particle beam b.
Since the slope of the straight line graph of FIG. 5 is Dx, the value of Dx can be obtained by obtaining the straight line graph of FIG.
That is, the reference momentum P is changed (ΔP) by transmitting the charged particle beam b in the beam transport line 2 through the different minute energy absorbers 11, and different plot points in FIG. 5 are obtained. Each plot point has an error bar due to measurement error of the beam monitor or statistical error due to multiple measurements.
Then, by interpolating and extrapolating the plot points with error bars in FIG. 5, the straight line graph of FIG. 5 is obtained, and the momentum dispersion function Dx (Dz) of equation (1) is obtained from the slope of this straight line. It is done.

<Automatic measurement of momentum dispersion function Dx (Dz) and control for automatically correcting the momentum dispersion function Dx (Dz) within the allowable value Δx (Δz)>
Next, the automatic measurement of the momentum dispersion function Dx (Dz) of the beam transport line 2 by the beam measurement device mounted on the particle beam irradiation apparatus T and the momentum dispersion function Dx (Dz) are automatically corrected within the allowable value Δx (Δz). Control will be described.
The control for correcting the momentum dispersion function Dx in the horizontal direction of the beam transport line 2 within the allowable value Δx will be described. However, the momentum dispersion function Dz in the vertical direction (Z direction) is corrected within the allowable value Δz. Since the control is similar and can be performed at the same time, the description of the vertical direction (Z direction) is omitted. The allowable value Δx and the allowable value Δz may be the same value or different values.

FIG. 6 is a flowchart showing an example of automatic measurement of the momentum dispersion function Dx of the beam transport line 2 by the beam measurement device and control for automatically correcting the momentum dispersion function Dx within the allowable value Δx.
In the flowchart illustrated in FIG. 6, a plurality of plate-like minute energy absorbing materials 11 illustrated in FIG. 2 are assumed. The minute energy absorbing material 11 (11a, 11b, 11c, 11d, 11e) has the same material and the same thickness.
The target value (allowable value Δx) of | Dx | at the time of automatic correction is determined by the beam use conditions and the measurement accuracy of any of the beam monitors (8A, 8B, 8C) used for measurement. Here, the second beam monitor 8B is used for measurement.

The quadrupole electromagnet used for automatic correction is one of the correction sections of the converging / diverging quadrupole electromagnets (5A, 5B, 5C, 6A, 6B, 6C) on the beam transport line 2, or two quadrupoles. Electromagnet. In the present embodiment, automatic correction is performed by the first convergence / divergence quadrupole electromagnets 5A and 6A.
Here, this control is performed by the control device S of the beam measuring device.
Before the automatic measurement of the momentum dispersion function Dx and the control that automatically corrects Dx within the allowable value Δx, the quadrupole electromagnets for convergence / divergence (5A, 5B, 5C, 6A, 6B, 6C) are roughly based on the theoretical values. Is set.

Then, according to the flow of FIG. 6, the current values to the convergence / divergence quadrupole electromagnets 5A and 6A used for automatic correction are automatically adjusted so that the momentum dispersion function Dx (Dz) becomes a predetermined value.
The automatic measurement of the momentum dispersion function Dx (Dz) and the control for automatically correcting the momentum dispersion function Dx (Dz) within the allowable value Δx (Δz) are performed as follows.
First, the number of used minute energy absorbers 11 is input to N by a user using a terminal device such as a PC (Personal Computer) (not shown) (S101 in FIG. 6). Here, “N” is the number of minute energy absorbers 11 when the minute energy absorbers 11 are the same material and have the same thickness. For example, in the example of FIG. 2, “5” is input.

The number “N” indicates the minute energy absorbing material 11 when the minute energy absorbing material 11 is of the same thickness and different materials other than those exemplified, or when the different thickness, same material, or different thickness, different materials. By combining 11, different combinations of the minute energy absorbing material 11 can be obtained. Therefore, in these cases, “N” may be the number of combinations of the different minute energy absorbing materials 11. Alternatively, it is possible to configure so that “N” is appropriately selected within a range equal to or less than the above-determined value in consideration of variations in measurement points.
Note that “N” may be initially set in the control device S or may be automatically set by acquiring necessary information such as the material and thickness of each minute energy absorbing material 11.

Subsequently, the power supply of the second beam monitor 8B used for the measurement is turned on, and a preparation for measuring the dose by the second beam monitor 8B is made (S102). Then, the deflector electrode 3 and the like of the synchrotron 1 are controlled, and the charged particle beam b is extracted to the beam transport line 2 (S103).
Then, in the control device S of the beam measuring device, 0 is set to the count variable n (S104), and the control device S of the beam measuring device determines whether n> N (S105).

  If it is determined in S105 that n> N is not satisfied (No in S105), that is, if the predetermined number of plot points shown in FIG. 5 are not collected, as shown in FIG. The nth sheet is inserted into the trajectory of the charged particle beam b. In the example of FIG. 2, a state where the first minute energy absorbing material 11 a of the minute energy absorbing material 11 is inserted in the trajectory of the charged particle beam b is shown. For example, when n = 3rd sheet, in addition to the minute energy absorbing materials 11a and 11b, the third minute energy absorbing material 11c is inserted into the trajectory of the charged particle beam b (S106). When “N” is determined by the combination of the minute energy absorbers 11, the combination “n” -th minute energy absorber 11 is inserted into the trajectory of the charged particle beam b.

Subsequently, the beam profile of the charged particle beam b is measured by the second beam monitor 8B (S107), and the centroid calculation (calculation for obtaining the position of the centroid) of the charged particle beam b in the beam transport line 2 is performed (S108). ). The calculation of the center of gravity of the charged particle beam b may be performed by the second beam monitor 8B or by the control device S of the beam measuring device.
Subsequently, n = n + 1 is calculated in the control device S of the beam measuring device (S109), and the process proceeds to S105.

On the other hand, if it is determined in S105 of FIG. 6 that n> N (Yes in S105), that is, if a predetermined number of plot points shown in FIG. An operation for obtaining the momentum dispersion function Dx is performed. That is, from the predetermined number of plot points (see FIG. 5) obtained by changing the momentum of the beam transport line 2 using the minute energy absorbing material 11, the equation (1) of the straight line of ΔX is obtained, and the slope of the straight line is obtained. An operation for obtaining (Dx) is performed (S110).
Subsequently, in the control device S of the beam measuring apparatus, it is determined whether or not the automatic correction of the first converging / diverging quadrupole electromagnets 5A and 6A is performed (S111). Whether or not automatic correction is performed may be configured to be input and set by a user using a terminal device before measurement, or may be configured to be set in advance in the system.

If it is determined in S111 that automatic correction of the first converging / diverging quadrupole electromagnets 5A and 6A is not performed (No in S111), the minute energy absorption put in the trajectory of the charged particle beam b in the beam transport line 2 Control is performed so as to pull out the minute energy absorbing material 11, the second beam monitor 8B, and the like of the material changing device 10 (S112). Then, the emission of the charged particle beam b to the beam transport line 2 is turned off (S113), and the process ends.
On the other hand, if it is determined in S111 of FIG. 6 that automatic correction of the first converging / diverging quadrupole electromagnets 5A and 6A is performed (Yes in S111), | Dx | < It is determined whether or not Δx (allowable value) is satisfied (S114).

If it is determined in S114 that | Dx | <Δx is not satisfied (No in S114), feedback calculation such as a combination with proportional control or integral control is performed so that | Dx | <Δx (S115). Needless to say, the method of the feedback calculation is arbitrary.
Then, the current values of the first convergence / divergence quadrupole electromagnets 5A and 6A are changed based on the result of the feedback calculation in S115 (S116), and the process proceeds to S104.

If it is determined in S114 that | Dx | <Δx (Yes in S114), the minute energy absorbing material 11 of the minute energy absorbing material replacing device 10 placed in the trajectory of the charged particle beam b in the beam transport line 2, The second beam monitor 8B is controlled to be pulled out (S117). Then, the emission of the charged particle beam b to the beam transport line 2 is turned off (S118), and the process ends.
The above is the flow of control for automatically measuring the momentum dispersion function Dx of the beam transport line 2 and automatically correcting the momentum dispersion function Dx within the allowable value (Δx) by the beam measuring apparatus shown in FIG.

In the above example, the control for automatically correcting the momentum dispersion function Dx in the horizontal direction within the allowable value has been described. However, the control for automatically correcting the momentum dispersion function Dz in the vertical direction (Z direction) within the allowable value is simultaneously performed. Alternatively, either the control for automatically correcting the momentum dispersion function Dx in the horizontal direction (X direction) within the allowable value or the control for automatically correcting the momentum dispersion function Dz in the vertical direction (Z direction) within the allowable value. You may control to perform.
In the above example, the case of | Dx | <Δx (allowable value) is illustrated, but | Dx | ≦ Δx (allowable value) (| Dz | ≦ Δz (allowable value)) or | Dx | = predetermined value (| Dz | = predetermined value) or | Dx | = 0 (| Dz | = 0) may be controlled. In the case of | Dx | = 0 (| Dz | = 0), ΔX is 0 regardless of the value of the momentum difference (ΔP), which is more desirable, as can be seen from the equation (1).

  According to the above configuration, in the measurement of the momentum dispersion function Dx (Dz) in the beam transport line 2 which is troublesome and very inconvenient in the conventional method, a plurality of minute pieces that can be taken in and out provided on the beam transport line 2 are used. The momentum of the charged particle beam b passing through the energy absorbing material 11 is changed, and the change in the center of gravity of the charged particle beam b on the beam transport line 2 is measured using the beam monitor 8B or the like. The dispersion function Dx (Dz) can be measured.

In this configuration, when the momentum dispersion function Dx (Dz) is not measured, the minute energy absorber 11 is pulled out of the beam transport line 2 to quickly switch between the measurement state of the momentum dispersion function Dx (Dz) and the normal emission state. It is also possible. Therefore, by using the minute energy absorbing material 11, the same effect as the change of the momentum by the conventional method can be obtained easily and simply.
The momentum dispersion function Dx (Dz) is difficult to determine at one measurement point (momentum difference). By using a plurality of minute energy absorbers 11, the upstream synchrotron 1 (accelerator) can be used. While emitting the charged particle beam b, it is possible to measure a large number of points by calculating the center of gravity (calculation for obtaining the position of the center of gravity) by the beam monitor 8B of the beam transport line 2, and the measurement speed can be increased.

Further, since the routine of measurement work is very simple, there is an advantage that automation by those computer controls in combination with the calculation of the center of gravity by the beam monitor 8B can be easily performed, and the beam transport line 2 on the extremely high speed is provided. The momentum dispersion function Dx (Dz) can be measured.
In addition, based on the measurement results, correction is made such that the momentum dispersion function Dx (Dz) at the irradiation symmetry (target) position where the charged particle beam b is irradiated is less than or less than a predetermined value, or is set to a predetermined value or 0. It is also possible to add a control function that can be performed automatically and an automatic correction section of any of the converging / diverging quadrupole electromagnets 5A, 6A, 5B, 6B, 5C, and 6C to the beam transport line 2.

<Micro energy absorbing material replacement device 20 according to modified embodiment 1>
Next, the minute energy absorbent replacement device 20 according to the first modification will be described with reference to FIG. FIG. 7 is a perspective view showing the minute energy absorbing material replacing device 20 according to the first modification.
The minute energy absorbing material replacing device 20 according to the first modified embodiment is configured such that the minute energy absorbing material 11 according to the embodiment is a rotating minute energy absorbing rotating body 21.

The minute energy absorbing material replacing device 20 according to the first modification includes a first minute energy absorbing rotating face 21A, a second minute energy absorbing rotating face 21B, and a third minute energy absorbing rotating face 21C having different thicknesses and / or materials, A minute energy absorption rotator 21 having a notch 21S that forms a gap 21p through which the charged particle beam b passes as it is is provided and is rotatably supported.
The minute energy absorption rotator 21 is rotated by a predetermined angle (arrow α1 in FIG. 7) by a rotation drive mechanism such as a stepping motor (not shown), whereby the first, second, and third minute energy absorption rotators 21A, 21B, Either 21C or the gap 21p of the notch 21S is arranged so as to face the charged particle beam b passing through the beam transport line 2 substantially perpendicularly, that is, on the trajectory of the charged particle beam b.

For example, in FIG. 7, when the minute energy absorption rotator 21 is rotated, the gap 21p of the cutout portion 21S of the minute energy absorption rotator 21 is arranged in the charged particle beam b passing through the beam transport line 2 and charged. A state in which the particle beam b passes through the gap 21p of the cutout portion 21S of the minute energy absorption rotator 21 is illustrated.
In FIG. 7, the first, second, and third minute energy absorption rotating surfaces 21A, 21B, and 21C of the minute energy absorbing rotator 21 are formed of the same material as the minute energy absorbing material 11, and each has a thickness. The case where the energy (momentum) is changed by changing the charged particle beam b passing through the beam transport line 2 and passing through each of them is illustrated.

  As described above, the first, second, and third minute energy absorption rotating surface bodies 21A, 21B, and 21C of the minute energy absorption rotating body 21 may have the same thickness and may be made of different materials. Further, the first, second, and third minute energy absorption rotating surface bodies 21A, 21B, and 21C of the minute energy absorption rotating body 21 may have different thicknesses and be made of different materials.

  According to the minute energy absorbing material replacing device 20 of the first modification, the minute energy absorbing rotating body 21 having the first, second, and third minute energy absorbing rotating face bodies 21A, 21B, 21C and the gap 21p of the notch 21S. , And the energy (momentum) of the charged particle beam b is changed easily and smoothly. In addition, maintenance of the minute energy absorbing material replacement device 20 is easy.

The minute energy absorption rotator 21 includes first, second, and third minute energy absorption rotators 21A, 21B, and 21C and a gap 21p of the notch 21S, and each of them is a charged particle of the beam transport line 2. Although the case where the energy (momentum) is changed in three stages by passing the beam b is exemplified, the minute energy absorption rotator 21 is constituted by the first minute energy absorption rotator 21A and the notch 21S, and the beam The energy (momentum) of the charged particle beam b in the transport line 2 may be changed in one stage, or the minute energy absorption rotator 21 may be replaced with the first and second minute energy absorption rotators 21A and 21B. The notch 21S may be used to change the energy (momentum) of the charged particle beam b in the beam transport line 2 in two stages, or a minute energy Energy of the charged particle beam b of the beam transport line 2 at yield rotating body 21 (momentum) 4,5,6, may be configured to change the ... stage.
As described above, the number of steps for changing the energy (momentum) of the charged particle beam b in the beam transport line 2 by the minute energy absorption rotating body 21 can be arbitrarily selected.

<Small Energy Absorbing Material Replacement Device 30 of Modification 2>
Next, the minute energy absorbent replacement device 30 according to the second modification will be described with reference to FIG. FIG. 8 is a perspective view showing a minute energy absorbent replacement device 30 according to the second modification.
The micro energy absorbing material replacing device 30 according to the modified embodiment 2 includes the micro energy absorbing rotating bodies 31, 32,... In which a plurality of the micro energy absorbing rotating bodies 21 of the micro energy absorbing material replacing device 20 according to the above modified embodiment 1 are arranged in parallel. The number of changes in the energy (momentum) of the charged particle beam b in the beam transport line 2 is increased.

  The minute energy absorbing material replacing device 30 according to the second modified embodiment passes through the first, second, and third minute energy absorbing rotating surface bodies 31A, 31B, and 31C and the charged particle beam b as they are with the same or different thickness and / or material. A minute energy absorption rotator 31 having a notch 31S that forms a gap 31p to be formed, and first, second, and third minute energy absorption rotators 32A, 32B having the same or different thickness and / or material. The minute energy absorption rotator 32 having a notch 32S that forms a gap 32p through which the charged particle beam b passes as it is, and the first, second, and third of the same or different thickness and / or material. A gap 33p is formed through which the minute energy absorption rotating surface bodies 33A, 33B, 33C and the charged particle beam b pass as they are. Ri-outs and a small energy absorbing rotating body 33 having a 33S, are rotatably supported, respectively.

For example, the first, second, and third minute energy absorption rotating surfaces 31A, 31B, and 31C of the minute energy absorbing rotator 31 are formed of the same material as the minute energy absorbing material 11 of the above-described embodiment, and each has a different thickness. Thus, the energy (momentum) is changed by passing the charged particle beam b passing through the beam transport line 2.
Similarly, the first, second, and third minute energy absorption rotating surfaces 32A, 32B, and 32C of the minute energy absorbing rotator 32 are formed of the same material as the minute energy absorbing material 11 of the above-described embodiment, and each has a thickness. The energy (momentum) is changed when the charged particle beam b passing through the beam transport line 2 passes through each of them.

  Similarly, the first, second, and third minute energy absorption rotating surfaces 33A, 33B, and 33C of the minute energy absorbing rotator 33 are formed of the same material as the minute energy absorbing material 11 of the above-described embodiment, and each has a thickness. The energy (momentum) is changed when the charged particle beam b passing through the beam transport line 2 passes through each of them.

  Alternatively, the first, second, and third minute energy absorption rotating surfaces 31A, 31B, and 31C of the minute energy absorbing rotator 31 may be made of different materials or the same thickness. Further, the first, second, and third minute energy absorption rotating bodies 32A, 32B, and 32C of the minute energy absorbing rotator 32 may be formed of different materials or the same thickness. Further, the first, second and third minute energy absorption rotating surface bodies 33A, 33B and 33C of the minute energy absorption rotating body 33 may be formed of different materials or the same thickness.

  The minute energy absorption rotator 31 is rotated by a predetermined angle (arrow α2 in FIG. 8) by a rotation drive mechanism such as a stepping motor (not shown), whereby the first, second, and third minute energy absorption rotators 31A, 31B, The gap 31p between 31C and the notch 31S is arranged so as to face the charged particle beam b passing through the beam transport line 2 substantially perpendicularly, that is, on the trajectory of the charged particle beam b.

  Similarly, the minute energy absorption rotator 32 is rotated by a predetermined angle (arrow α3 in FIG. 8) by a rotation drive mechanism such as a stepping motor (not shown), whereby the first, second, and third minute energy absorption rotators 32A. 32B, 32C and the gap 32p of the notch 32S are arranged so as to face the charged particle beam b passing through the beam transport line 2 substantially perpendicularly, that is, on the trajectory of the charged particle beam b.

  Similarly, the minute energy absorption rotator 33 is rotated by a predetermined angle (arrow α4 in FIG. 8) by a rotation drive mechanism such as a stepping motor (not shown), whereby the first, second, and third minute energy absorption rotators 33A. , 33B, 33C and the gap 33p of the notch 33S are arranged so as to face the charged particle beam b passing through the beam transport line 2 substantially perpendicularly, that is, on the trajectory of the charged particle beam b.

  Similarly, when other minute energy absorbing rotating bodies are provided in addition to these, the first, second and third minute energy absorbing rotating face bodies and the cutout portions are rotated by a predetermined angle by a stepping motor or the like. Are arranged so as to face the charged particle beam b passing through the beam transport line 2 substantially perpendicularly, that is, on the trajectory of the charged particle beam b.

  With this configuration, the first, second, and third minute energy absorption rotating bodies 31A, 31B, and 31C of the minute energy absorption rotator 31 and the gaps of the notch 31S with respect to the charged particle beam b passing through the beam transport line 2 are used. Any one of 31p, any one of the first, second and third minute energy absorption rotating surfaces 32A, 32B, 32C of the minute energy absorption rotating body 32 and the gap 32p of the notch 32S, and minute energy absorbing rotation. Any one of the first, second, and third minute energy absorption rotating surface bodies 33A, 33B, and 33C of the body 33 and the gap 33p of the notch 33S are opposed substantially vertically, that is, on the trajectory of the charged particle beam b. .

  As a result, the charged particle beam b is changed to any one of the first, second, and third minute energy absorption rotating surfaces 31A, 31B, and 31C of the minute energy absorbing rotator 31 and the gap 31p of the notch 31S and the minute energy. Any of the first, second, and third minute energy absorption rotating surface bodies 32A, 32B, and 32C of the absorption rotating body 32 and the gap 32p of the notch 32S, and the first, second, and second of the minute energy absorbing rotating body 33 Any combination of the third minute energy absorption rotating surface bodies 33A, 33B, 33C and the gap 33p of the notch 33S is allowed to pass, and the energy (momentum) of the charged particle beam b can be changed by the number of the combinations.

  In FIG. 8, the charged particle beam b passing through the beam transport line 2 is exposed to the gap 31p of the notch 31S of the minute energy absorption rotator 31, the gap 32p of the notch 32S of the minute energy absorption rotator 32, and the minute. The gap 33p of the cutout portion 33S of the energy absorption rotator 33 is disposed, and the charged particle beam b is transmitted through the gap 31 of the cutout portion 31S of the minute energy absorption rotator 31, 32, 33, the gap 32p of the cutout portion 32S, The state which passes the space | gap 33p of the notch 33S is shown in figure.

  According to the minute energy absorbing material replacement device 30 of the second modification, any one of the first, second, and third minute energy absorbing rotating bodies 31, 32, 33 is combined and passed through the charged particle beam b of the beam transport line 2. Since the energy (momentum) is changed, the energy (momentum) of the charged particle beam b can be changed many times, and the selection range is widened. Further, the energy (momentum) of the charged particle beam b can be changed easily and smoothly.

  Each of the minute energy absorption rotators 31, 32, 33 has first, second, and third minute energy absorption rotators and a notch, through which the charged particle beam b of the beam transport line 2 passes. In this example, the energy (momentum) is changed in three stages, but the number of changing the energy (momentum) of the charged particle beam b passing through each of the minute energy absorption rotating bodies 31, 32, 33 is as follows. The natural number (positive integer) can be selected as appropriate.

For example, the minute energy absorption rotator 31 may be changed to two stages, the minute energy absorption rotator 32 may be changed to six stages, and the minute energy absorption rotator 33 may be changed to five stages.
As described above, the number of steps of the minute energy absorbing rotating body of the minute energy absorbing rotating body can be arbitrarily selected as appropriate.

Further, the number of minute energy absorbing rotating bodies provided in the minute energy absorbing material replacing device 30 can be arbitrarily selected. For example, the number of minute energy absorbing rotating bodies provided in the minute energy absorbing material replacing device 30 may be two, six, seven,...
Note that although various configurations have been described in the above-described embodiments and modifications, they can be combined as appropriate.

  Although various embodiments of the present invention have been described above, the description is intended to be exemplary rather than limiting. It will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the present invention. Accordingly, various modifications and changes may be made in the present invention within the scope of the appended claims.

1 Synchrotron (accelerator)
2 Beam transport line 5A First focusing quadrupole electromagnet (correction electromagnet)
6A First divergent quadrupole magnet (correction electromagnet)
8B Second beam monitor (beam monitor, momentum dispersion function measuring means)
11 Micro energy absorber (micro energy absorber)
11a, 11b, 11c, 11d, 11e Minute energy absorber (multiple minute energy absorbers)
21 Micro-energy absorption rotating body (micro-energy absorber)
21A First minute energy absorption rotating face (beam transmission region)
21B Second minute energy absorption rotating face (beam transmission region)
21C 3rd minute energy absorption rotating body (beam transmission region)
21p Air gap 21S Notch 31, 32, 33 Minute energy absorption rotating body (minute energy absorber, single minute energy absorber)
31A, 32A, 33A First minute energy absorption rotating face (beam transmission region)
31B, 32B, 33B Second minute energy absorption rotating face (beam transmission region)
31C, 32C, 33C Third minute energy absorption rotating body (beam transmission region)
31p, 32p, 33p Air gap 31S, 32S, 33S Notch b Charged particle beam Dx, Dz Momentum dispersion function S controller (Momentum dispersion function measurement means, automatic measurement control means, automatic correction control means)
T Particle beam irradiation system (beam transport system)

Claims (15)

Beam measurement that measures the momentum dispersion function that expresses the difference in the position of the charged particle beam in the beam transport line that transports the charged particle beam extracted from the accelerator that accelerates the charged particles to the irradiation device that irradiates the irradiation target. A device,
A micro energy absorber capable of entering and exiting the charged particle beam trajectory of the beam transport line, and changing the energy of the charged particle beam by passing the charged particle beam when entering the trajectory of the charged particle beam; ,
And a momentum dispersion function measuring means for measuring a momentum dispersion function of the charged particle beam in the beam transport line based on a change in energy of the charged particle beam by the minute energy absorber. . The minute energy absorber comprises a plurality of,
The beam measuring apparatus according to claim 1, wherein any one of the plurality of minute energy absorbers is arranged alone or in combination on the trajectory of the charged particle beam. The minute energy absorber has a beam transmission region having a different thickness and / or a different material through which the charged particle beam passes, and a notch portion in which a gap through which the charged particle beam passes is formed. Provided freely,
The minute energy absorber is rotated, and either the beam transmission region of the minute energy absorber or the gap of the notch is arranged on the trajectory of the charged particle beam. Item 2. The beam measuring apparatus according to Item 1. The minute energy absorber includes a beam transmission region having the same or different thickness and / or the same or different material through which the charged particle beam passes, and a notch in which a gap through which the charged particle beam passes is formed. A single minute energy absorber having a plurality of the minute energy absorbers, each of the plurality of single minute energy absorbers being rotatably provided;
Each single minute energy absorber is rotated, and either one of the beam transmission region or the notch gap of each single minute energy absorber is arranged on the trajectory of the charged particle beam. The beam measuring apparatus according to claim 1. The momentum dispersion function measuring means has a beam monitor that measures a beam profile of the charged particle beam that has passed through the minute energy absorber,
The momentum dispersion function measuring means changes the energy of the charged particle beam by entering or exiting the orbit of the charged particle beam of the minute energy absorber, and then changes the energy of the charged particle beam measured by the beam monitor. 5. The apparatus according to claim 1, further comprising an automatic measurement control unit that automatically measures the momentum dispersion function by calculating a gravity center position of the charged particle of the charged particle beam based on a beam profile. The beam measuring apparatus according to one item. Automatic correction control means for correcting the value of the momentum dispersion function to a target value based on the measured value of the momentum dispersion function measured;
A correction electromagnet provided downstream of the minute energy absorber in the beam transport line and applying a magnetic field to the charged particle beam;
6. The beam measuring apparatus according to claim 1, further comprising: a correction electromagnet control unit that changes a current applied to the correction electromagnet in accordance with the correction of the automatic correction control unit. . The beam measurement apparatus according to claim 6, wherein the target value is 0.   A beam comprising an accelerator for accelerating charged particles, a beam transport line for transporting a charged particle beam extracted from the accelerator to an irradiation device, and the beam measuring device according to any one of claims 1 to 7. Transport system. Beam measurement that measures the momentum dispersion function that expresses the difference in the position of the charged particle beam in the beam transport line that transports the charged particle beam extracted from the accelerator that accelerates the charged particles to the irradiation device that irradiates the irradiation target. A method for measuring a device,
The beam measuring device includes a minute energy absorber capable of entering and exiting the trajectory of the charged particle beam and a momentum dispersion function measuring unit,
The micro-energy absorber changes energy of the charged particle beam by allowing the charged particle beam to pass through when the charged particle beam is orbited in the beam transport line,
The momentum dispersion function measuring means measures a momentum dispersion function of the charged particle beam in the beam transport line based on a change in energy of the charged particle beam by the minute energy absorber. Measuring method. The minute energy absorber comprises a plurality of,
Any one of a plurality of the minute energy absorbers are arranged alone or in combination on the trajectory of the charged particle beam,
The measurement method of the beam measuring apparatus according to claim 9, wherein the charged particle beam passes through the single or overlapping minute energy absorber. The minute energy absorber has a beam transmission region having a different thickness and / or a different material, and a notch portion in which a gap is formed, and is provided rotatably.
The minute energy absorber is rotated, and either the beam transmission region or the gap of the notch is placed on the trajectory of the charged particle beam,
10. The beam according to claim 9, wherein the charged particle beam passes through either the beam transmission region or the gap of the notch that is placed on the orbit of the minute energy absorber. Measuring method of the measuring device. The minute energy absorber is composed of a plurality of single minute energy absorbers having a beam transmission region having the same or different thickness and / or the same or different material and a notch portion in which a gap is formed, A plurality of single minute energy absorbers are rotatably provided,
Each of the single minute energy absorbers is rotated, and either the beam transmission region or the notch gap of each of the single minute energy absorbers is placed in the trajectory of the charged particle beam.
The charged particle beam passes through either the beam transmission region or the gap of the notch of each single minute energy absorber placed in the trajectory. Measuring method of the beam measuring apparatus. The momentum dispersion function measuring means has a beam monitor that measures a beam profile of the charged particle beam that has passed through the minute energy absorber,
The momentum dispersion function measuring means has automatic measurement control means,
The energy of the charged particle beam is changed by entering and exiting the charged particle beam of the minute energy absorber,
The automatic measurement control means automatically calculates the momentum dispersion function by calculating a gravity center position of the charged particle of the charged particle beam based on a beam profile of the charged particle beam whose energy measured by the beam monitor is changed. It measures. The measuring method of the beam measuring apparatus as described in any one of Claims 9-12 characterized by the above-mentioned. The beam measuring device includes an automatic correction control unit, a correction electromagnet provided downstream of the minute energy absorber in the beam transport line and applying a magnetic field to the charged particle beam, and a correction electromagnet control unit.
The automatic correction control unit corrects the value of the momentum dispersion function to be a target value based on the measured value of the measured momentum dispersion function,
The beam measuring apparatus according to claim 9, wherein the correction electromagnet control unit changes a current applied to the correction electromagnet according to the correction of the automatic correction control unit. Measuring method. The measurement value of the beam measuring apparatus according to claim 14, wherein the target value is 0.

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