WO2019085339A1

WO2019085339A1 - Stable beam flow intensity modulation device of circular accelerator

Info

Publication number: WO2019085339A1
Application number: PCT/CN2018/076214
Authority: WO
Inventors: 李为; 樊宽军; 陈曲珊; 王健; 李小飞; 唐凯; 疏坤; 曾志杰
Original assignee: 华中科技大学
Priority date: 2017-10-31
Filing date: 2018-02-11
Publication date: 2019-05-09
Also published as: CN107864546A; CN107864546B

Abstract

A stable beam flow intensity modulation device of a circular accelerator, comprising a first electrostatic deflection device (1), a second electrostatic deflection device (2) and a vertical flow-limiting gap (3), wherein the first electrostatic deflection device (1) and the second electrostatic deflection device (2) have the same structure and respectively comprise an upper pole plate and a lower pole plate which are vertically symmetric about a central plane of the circular accelerator; the vertical flow-limiting gap (3) comprises: a pair of plates, having L-shaped cross sections and being vertically symmetric around the central plane; the first electrostatic deflection device (1), the second electrostatic deflection device (2) and the vertical flow-limiting gap (3) are respectively arranged on upper surfaces and lower surfaces of three peak region magnetic poles in the circular accelerator; a beam flow generates a vertical rail projection by the combined effect of the first electrostatic deflection device (1) and the second electrostatic deflection device (2); the vertical flow-limiting gap (3) is used for blocking a beam flow which has relatively large vertical deflection; and the beam flow intensity is adjusted by changing the size of a vertical protruding rail of the beam flow and adjusting a beam scraping proportion. The vertical motion of a beam flow is prevented from becoming unstable by correcting a scraped beam flow back to the central plane, so that the intensity of a lead-out beam flow is stably adjusted.

Description

Beam intensity stable modulation device for cyclotron

[Technical Field]

The present invention belongs to the field of cyclotrons, and more particularly to a beam intensity stabilization modulation device for a cyclotron.

【Background technique】

Accurate and rapid radiotherapy is the development direction of particle beam radiotherapy. Proton radiotherapy devices based on cyclotrons occupy more markets due to their advantages in volume and cost. However, the cyclotron can only output a beam of constant energy. In order to meet the treatment requirements for different depth tumors in clinical treatment, it is necessary to adjust the thickness of the beam on the transmission line through the graphite of the degrader to perform beam energy modulation. This energy regulation method causes the high-energy particle beam transmission efficiency to differ from the low-energy particle beam by tens or even hundreds of times, which is not conducive to clinical application, and thus requires beam intensity adjustment for particle beams of different energies. On the other hand, the current particle beam precision radiotherapy frontier technology can continuously and stably adjust the beam intensity, so as to achieve a specific dose distribution on the continuous scan curve, shorten the treatment time, and maximize the potential of the particle beam radiotherapy. Therefore, it is necessary to achieve a rapid and stable adjustment of the beam current extracted from the cyclotron.

There are three main ways to adjust the beam intensity of the cyclotron: (1) adjust the ion source bias and airflow, but this mode of regulation is slow and will cause unstable operation of the ion source; (2) use on the transport line The quadrupole magnet expands the beam and uses the collimator to scrape the beam. This method causes the high-energy beam loss at the collimator to be severe, resulting in a high local radiation dose and a slower adjustment speed. (3) In the central area, A vertical deflection electric field is applied to the beam by a static deflection device for vertical deflection, and then subjected to scraping through the vertical restriction hole, thereby realizing the adjustment of the beam intensity.

Since the single electrostatic deflection device scheme operates on a low energy beam, the beam loss causes a lighter material activation problem and a fast response speed, so it is often used. However, the beam passing through the vertical restrictor still retains the vertical momentum and vertical orbital offset obtained by the vertical electric field deflection. When the beam is adjacent to the phase boundary of the phase, it is lost due to the small disturbance. The experimentally measured "deflection electrode bias vs. beam intensity" mapping relationship shows that when the bias voltage between the deflection electrodes of the electrostatic deflection device is relatively large, the trend of the beam current intensity to the deflection electrode bias is nonlinear. Affect the accuracy of beam intensity adjustment.

[Summary of the Invention]

In view of the deficiencies of the prior art, an object of the present invention is to provide a beam intensity stable modulation device for a cyclotron, which aims to solve the introduction of beam axial momentum caused by beam current intensity modulation for a single electrostatic deflection device in the prior art. The problem of beam current regulation nonlinearity affects the accuracy of beam intensity adjustment.

The present invention provides a beam intensity stabilization modulation device for a cyclotron, comprising: a first electrostatic deflection device, a second electrostatic deflection device, and a vertical current limiting slit; the first electrostatic deflection device and the second electrostatic deflection device have the same structure. Each includes: an upper plate and a lower plate symmetrically disposed about a center plane of the cyclotron; the vertical current limiting slit includes: a pair of L-shaped sections and symmetrically placed plates, wherein one plate is disposed in the cyclotron An upper surface of the magnetic pole of the two-peak region, another plate is disposed on a lower surface of the magnetic pole of the second peak region of the cyclotron; the vertical current limiting slit is configured to move a beam with a large vertical deflection to the slit wall Loss, to achieve beam intensity adjustment.

Further, an upper plate of the first electrostatic deflection device is disposed on an upper surface of the first peak magnetic pole in the cyclotron, and a lower plate of the first electrostatic deflection device is disposed in the first peak of the cyclotron a lower surface of the magnetic pole; an upper plate of the second electrostatic deflection device is disposed on an upper surface of the third peak magnetic pole in the cyclotron, and a lower plate of the second electrostatic deflection device is disposed on the cyclotron The lower surface of the magnetic pole in the third peak region.

Further, in operation, by applying a first deflection voltage between the upper and lower plates of the first electrostatic deflection device, a first space between the upper and lower plates of the first electrostatic deflection device is formed. a first electrostatic field vertically upward, applying a second deflection voltage opposite to the first deflection voltage between the upper and lower plates of the second electrostatic deflection device, such that the second electrostatic deflection device is A vertically downward second electrostatic field is formed between the lower plates; when the beam passes, the first action of the first electrostatic field is shifted upward in the vertical direction, and after the 1/4 turn in the forward direction Vertical current limiting slits, the beam with large vertical deviation is intercepted by the vertical restricting slit, only part of the beam passes and continues to move forward; after the beam is moved through the vertical restricting slit by 1/4 turn Reaching the second electrostatic deflection device, and under the action of the second electrostatic field, the beam moves in the vertical direction and starts to move downward; when the beam moves in the forward direction for 1/2 turn, it reaches the first electrostatic deflection device again. And in the first electrostatic field Under the action of the beam, the velocity of the beam in the vertical direction is gradually zero, and the vertical orbit returns to the center plane.

Further, when the cyclotron needs to extract a beam having a weaker intensity, the beam is controlled to form a larger orbital protrusion in the vertical direction by simultaneously adjusting the bias amounts of the first electrostatic deflection device and the second electrostatic deflection device, so that the beam More particles in the stream are intercepted by the vertical current limiting slit, and fewer beam particles are passed through the beam channel to achieve weaker beam extraction; when the cyclotron needs to extract a stronger beam, it is simultaneously adjusted The biasing size of the first electrostatic deflection device and the second electrostatic deflection device controls the beam to form smaller orbital protrusions in the vertical direction, so that a small number of particles in the beam are intercepted by the vertical current limiting slit, and more The beam particles are beamed out through the beam channel to achieve a stronger beam.

According to the present invention, a pair of electrode plates of the first electrostatic deflection device and a pair of electrode plates of the second electrostatic deflection device are respectively mounted on the upper and lower surfaces of the first peak region magnetic pole and the third peak region magnetic pole in the central region of the cyclotron, at a distance of 90 a vertical limiting slit is mounted on the upper and lower surfaces of the magnetic poles of the second peak region of the degree position; by adjusting the voltage difference between the upper and lower electrode plates of the first electrostatic deflection device, the particle beam from the ion source is vertically deflected to meet the strength requirement. The beam passes through the vertical current limiting slit; the beam current is deflected toward the center plane by adjusting the voltage difference between the upper and lower electrode plates of the second electrostatic deflection device; when passing through the first electrostatic deflection device again, the beam returns to the center plane And move in the horizontal direction. Therefore, while realizing the beam intensity adjustment, the vertical oscillating motion of the beam current is suppressed, and the vertical motion stability of the beam current is improved.

After the deflection voltage is applied to the upper and lower electrode plates of the first electrostatic deflection device, a first electrostatic field in the vertical direction is formed between the two electrode plates, and when the particle beam passes, vertical deflection occurs under the action of the electrostatic field; When the slit is vertically restricted, particles larger than the center plane are scraped off, and only the intermediate slit is a beam passage. After the deflection voltage is applied to the upper and lower electrode plates of the second electrostatic deflection device, a second electrostatic field perpendicular to the first electrostatic deflection device is formed between the two electrode plates, and when the particle beam passes, the second static electricity is generated. Under the action of the field, vertical deflection occurs and moves toward the center plane. When the beam continues to move forward and reaches the first electrostatic deflection device again, the vertical flow of the beam under the action of the electrostatic field is completely eliminated, starting to move in the horizontal direction, and the vertical orbit returns to the center plane. Thereby, the vertical oscillation of the beam current is suppressed, and the vertical motion instability is reduced.

By adjusting the deflection voltages on the deflection electrode plates of the first electrostatic deflection device and the second electrostatic deflection device in combination, the beam corresponding to the strength requirement is ensured to pass through the vertical current limiting slit, and the beam after adjusting the intensity is modulated back to the central plane. ,Stable operation.

[Description of the Drawings]

FIG. 1 is a schematic structural diagram of a beam intensity stable modulation apparatus of a cyclotron according to an embodiment of the present invention.

2 is a schematic diagram showing relative positions of a first electrostatic deflection device, a second electrostatic deflection device, a vertical current limiting slit, and a beam horizontal track in a beam intensity stabilization modulation device of a cyclotron according to an embodiment of the present invention.

3 is a schematic cross-sectional structural view of an electrostatic deflection device in a beam intensity stabilization modulation device of a cyclotron according to an embodiment of the present invention.

4 is a schematic structural view of a vertical current limiting slit in a beam intensity stable modulation device of a cyclotron according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a beam current stable modulation principle of a cyclotron according to an embodiment of the present invention.

Wherein, 1 is a first electrostatic deflection device, 2 is a second electrostatic deflection device, 3 is a vertical current limiting slit, 4 is a first peak magnetic pole, 5 is a second peak magnetic pole, and 6 is a third peak magnetic pole. 7 is the fourth peak magnetic pole, 8 is the first electrostatic field, 9 is the second electrostatic field, and 10 is the beam current.

【Detailed ways】

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

On the basis of realizing the beam intensity adjustment, the beam current in the cyclotron is corrected back to the center plane to improve the vertical direction motion stability, thereby improving the adjustment precision and stability of the beam current intensity of the cyclotron. The invention aims to introduce the vertical direction momentum of the beam during the beam intensity modulation of the single electrostatic deflection device, which causes the nonlinearity of the beam regulation and affects the adjustment precision of the beam intensity. A beam intensity modulation of a novel cyclotron is proposed. The method, on the basis of realizing the rapid beam intensity adjustment, simultaneously ensures the stability of the extracted beam and improves the beam intensity adjustment precision.

The beam intensity stable modulation device of the cyclotron according to the embodiment of the present invention includes: upper and lower plates in the first electrostatic deflection device 1 respectively disposed on upper and lower surfaces of the first peak region magnetic pole 4 in the central region of the cyclotron. The upper and lower plates of the second electrostatic deflection device 2 are respectively disposed on the upper and lower surfaces of the third peak magnetic pole 6 in the central region of the cyclotron, and the active region of the first electrostatic deflection device 1 covers the beam through the two consecutive passes. Two plates of the vertical current limiting slits 3 are respectively disposed on the upper and lower surfaces of the second peak region magnetic pole 5; the vertical direction of the particle beam is adjusted by adjusting the voltage difference between the upper and lower electrode plates of the first electrostatic deflection device 1 Deflecting, the beam 10 complying with the strength requirement is passed through the vertical current limiting slit 3; by adjusting the voltage difference between the upper and lower electrode plates of the second electrostatic deflection device 2, the beam 10 is deflected to move toward the center plane; The active area of the first electrostatic deflection device 1 causes the beam to again obtain a vertical direction of force, returning to the center plane. Therefore, the beam current intensity is suppressed while the beam current is adjusted, and the beam intensity adjustment accuracy is improved.

In the embodiment of the present invention, after the deflection voltage is applied to the deflection electrode plate of the first electrostatic deflection device 1, a vertical first electrostatic field 8 is formed between the two electrode plates, and when the particle beam passes, the first Vertical deflection occurs under the action of an electrostatic field 8; when passing through the vertical restriction slit 3, particles that are larger from the center plane are scraped off, and only the particle beam passing through the intermediate slit beam passage passes. After the deflection voltage is applied to the deflection electrode plate of the second electrostatic deflection device 2, a second electrostatic field 9 in the vertical direction opposite to that in the first electrostatic deflection device 1 is formed between the two electrode plates, when the particle beam 10 passes In the second electrostatic field 9, the vertical deflection occurs and moves toward the center plane. When the beam again passes through the active area of the first electrostatic deflection device 1, the beam begins to move in the horizontal direction under the action of the electrostatic field while the motion track returns to the center plane.

In the embodiment of the present invention, by adjusting the deflection voltages on the deflection electrode plates of the first electrostatic deflection device 1 and the second electrostatic deflection device 2 in combination, it is ensured that the beam corresponding to the strength requirement passes through the vertical current limiting slit 3 and is deflected back. Center plane, stable operation.

The invention adjusts the

electric field strengths

8, 9 between the deflection electrode plates by adjusting the bias voltages in the two pairs of first

electrostatic deflection devices

1, 2, thereby eliminating the vertical position and momentum of the beam while adjusting the beam intensity. Offset. The beam intensity adjustment method can achieve fast, accurate and stable beam intensity adjustment.

In order to further illustrate the beam intensity stabilization modulation device of the cyclotron provided by the embodiment of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1, in the embodiment of the present invention, the cyclotron includes: a first peak region magnetic pole 4, a second peak region magnetic pole 5, a third peak region magnetic pole 6 and a fourth peak region magnetic pole 7; and each peak region magnetic pole position Rotating at a 90 degree angle along the center of the cyclotron; the beam intensity stabilization modulation device based on the cyclotron includes: a first electrostatic deflection device 1, a second electrostatic deflection device 2, and a pair of L-shaped cross-section plates forming a vertical current limiting slit 3 . The vertical current limiting slit 3 is used for intercepting a beam current that is larger from the center plane to achieve beam intensity adjustment. The reason why the vertical restricting slit 3 is set to the L shape is that the longitudinal distance of the beam current can be prolonged, the vertical deflection movement time of the beam is increased, and the biasing requirement for the deflection device 1 is lowered.

The first electrostatic deflection device 1 includes two electrode plates of the same shape and structure, and the two electrode plates are vertically symmetrical with respect to the center plane of the cyclotron. The two electrode plates of the first electrostatic deflection device 1 are respectively mounted on the lower surface of the first peak region magnetic pole 4 and its corresponding upper peak region magnetic pole surface.

The two plates of the L-type vertical current limiting slit 3 are respectively mounted on the lower peak magnetic pole surface and the corresponding upper peak magnetic pole surface which are rotated by 90 degrees with the first peak magnetic pole 4; the second electrostatic deflection device 2 The two electrode plates are respectively mounted on the lower surface magnetic pole lower surface and the corresponding upper peak region magnetic pole surface which are disposed at 180 degrees symmetrical with the first peak region magnetic pole 4.

As shown in FIG. 2, the first electrostatic deflection device 1 has a horizontal section approximately trapezoidal and is mounted on the upper and lower surfaces of the first peak magnetic pole 4, and the radial dimension covers the 2-3 rotation path of the beam movement, and the shape and size are appropriate. Adjusted for installation; the second electrostatic deflection device 2 is similar to the first electrostatic deflection device 1, the radial dimension covers the third movement path of the beam movement, and the vertical current limiting slit 3 is mounted on the first electrostatic deflection device 1 and the second static electricity Between the deflection devices 2.

As shown in FIG. 3, the electrode plate of the electrostatic deflection device has a three-dimensional T-shaped structure and is nested in the frame-shaped structure base to fix the electrode plate to the surface of the magnetic pole.

As shown in FIG. 4, the upper and lower plates of the vertical current limiting slit are respectively L-shaped, and some particles in the beam are intercepted on the two L-shaped poles, thereby adjusting the particle beam passing through the middle of the slit to realize the cyclotron. The adjustment of the beam intensity is extracted.

As shown in FIG. 5, when the beam intensity stabilization modulation device is in an operating state, a deflection voltage is applied to the deflection electrode plate of the first electrostatic deflection device 1, and a vertically upward first electrostatic field 8 is formed between the electrode plates. A deflection voltage opposite to 1 is applied to the deflection electrode plate of the second electrostatic deflection device 2 to form a vertically downward second electrostatic field 9 between the electrode plates. When the beam current 10 passes, since the first action of the first electrostatic field 8 is shifted upward in the vertical direction, the vertical current limiting slit 3 is reached after running 1/4 turn in the forward direction, as shown in the figure, the vertical direction The beam that is larger off the center plane is intercepted by the vertical restrictor slit 3, and only part of the beam passes through and continues to move forward. After the beam current of the vertical current limiting slit 3 is moved by 1/4 turn, the second electrostatic deflection device 2 is reached. Under the action of the second electrostatic field 9, the vertical movement of the beam is reversed and begins to move downward, and moves in the forward direction. After /2 turns, the first electrostatic deflection device 1 is again reached. Under the action of the first electrostatic field 8, the velocity in the vertical direction gradually decreases to zero, and the vertical orbital position also returns to the center plane.

The intensity of the second electrostatic field 9 has a certain adjustment relationship with the intensity of the first electrostatic field 8, and its intensity varies with the intensity of the first electrostatic field 8. The first action of the first electrostatic field 8 on the beam 10 causes the beam to deflect in a sufficient vertical direction such that a portion of the particles of the beam 10 are intercepted by the vertical current limiting slit 3, thereby effecting adjustment of the beam intensity, thus The adjustment of the beam intensity can be achieved by adjusting the intensity of the first electrostatic field 8, i.e., the bias of the first electrostatic deflection device 1. The combination of the action of the second electrostatic field 9 on the beam 10 and the second action of the first electrostatic field 8 on the beam 10 corrects the beam 10 from the off-center plane position to the center plane, thereby suppressing vertical oscillation of the beam. Improve beam stability and adjustment accuracy.

When the cyclotron needs to extract a beam having a weaker intensity, the magnitude of the bias of the first electrostatic deflection device 1 and the second electrostatic deflection device 2 can be adjusted in combination to form a large orbital projection in the vertical direction. More particles in the beam are intercepted by the vertical current limiting slit 3, and fewer beam particles pass through the beam channel to achieve a weaker beam.

When the cyclotron needs to extract a beam having a stronger intensity, the beam current can be slightly shifted in the vertical direction by adjusting the bias voltages of the first electrostatic deflection device 1 and the second electrostatic deflection device 2, thereby making the beam current A small number of particles are intercepted by the vertical current limiting slit 3, and more beam particles pass through the beam channel, thereby achieving a stronger beam outgoing.

Under the guidance of the present invention, the position, size, shape, number of times of action of the first electrostatic deflection device 1, the second electrostatic deflection device 2, the vertical current limiting slit 3, and the like can be adjusted to achieve stable adjustment of the beam current.

Under the guidance of the present invention, it is within the scope of the present invention to increase the number of electrostatic deflection devices or vertical current limiting slits.

Those skilled in the art will appreciate that the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and scope of the present invention, All should be included in the scope of protection of the present invention.

Claims

A beam intensity stabilization modulation device for a cyclotron, comprising: a first electrostatic deflection device (1), a second electrostatic deflection device (2) and a vertical current limiting slit (3);

The first electrostatic deflection device (1) and the second electrostatic deflection device (2) are identical in structure, and each includes: an upper plate and a lower plate symmetrically disposed about a center plane of the cyclotron;

The vertical current limiting slit (3) comprises: a pair of L-shaped sections and symmetrically placed plates, wherein one plate is disposed on the upper surface of the second peak magnetic pole (5) in the cyclotron, and the other plate is disposed a lower surface of the second peak magnetic pole (5) in the cyclotron; the vertical current limiting slit (3) is used for moving a beam with a large vertical deflection to the slit wall to lose the beam Strength adjustment.
The beam intensity stabilization modulation apparatus according to claim 1, wherein an upper plate of said first electrostatic deflection device (1) is disposed on an upper surface of said first peak magnetic pole (4) in said cyclotron The lower plate of the first electrostatic deflection device (1) is disposed on a lower surface of the first peak magnetic pole (4) in the cyclotron;

An upper plate of the second electrostatic deflection device (2) is disposed on an upper surface of a third peak magnetic pole (6) in the cyclotron, and a lower plate of the second electrostatic deflection device (2) is disposed at The lower surface of the third peak magnetic pole (6) in the cyclotron.
A beam intensity stabilizing modulation apparatus according to claim 1 or 2, wherein, in operation, a first deflection voltage is applied between the upper and lower plates of said first electrostatic deflection device (1), Forming a vertically upward first electrostatic field (8) between the upper and lower plates of the first electrostatic deflection device (1), and upper and lower plates of the second electrostatic deflection device (2) Applying a second deflection voltage opposite to the first deflection voltage, such that a vertically downward second electrostatic field is formed between the upper and lower plates of the second electrostatic deflection device (2) ;

When the beam current (10) passes, since the first action of the first electrostatic field (8) is shifted upward in the vertical direction, the vertical current limiting slit (3) is reached after running 1/4 turn in the forward direction, vertical The beam with a large deviation in direction is intercepted by the vertical current limiting slit (3), only part of the beam passes through and continues to move forward; the beam current through the vertical limiting slit (3) moves 1/4 turn to reach a second electrostatic deflection device (2), and under the action of the second electrostatic field (9), the beam moves in the vertical direction and starts to move downward; when the beam moves in the forward direction for 1/2 turn, it reaches the first again. At the electrostatic deflection device (1), and under the action of the first electrostatic field (8), the velocity of the beam in the vertical direction is gradually zero, and the vertical orbit also returns to the center plane.
The beam intensity stabilization modulation apparatus according to any one of claims 1 to 3, wherein when the cyclotron needs to take out a beam having a weaker intensity, by simultaneously adjusting the first electrostatic deflection device (1) and The biasing size of the second electrostatic deflection device (2) controls the beam current to form a large orbital protrusion in the vertical direction, so that more particles in the beam are intercepted by the vertical current limiting slit (3), and less The beam particles are deflected by the beam passage to achieve a weaker beam;

When the cyclotron needs to extract a beam having a stronger intensity, the beam current is controlled to be smaller in the vertical direction by simultaneously adjusting the bias voltages of the first electrostatic deflection device (1) and the second electrostatic deflection device (2). The orbital protrusions cause a small number of particles in the beam to be intercepted by the vertical current limiting slit (3), and more beam particles pass through the beam channel to achieve a stronger beam current.