CN108112154B

CN108112154B - Heavy ion synchrotron

Info

Publication number: CN108112154B
Application number: CN201711362947.7A
Authority: CN
Inventors: 石健; 夏佳文; 杨建成
Original assignee: Huizhou Ion Science Research Center; Institute of Modern Physics of CAS
Current assignee: Huizhou Ion Science Research Center; Institute of Modern Physics of CAS
Priority date: 2017-12-13
Filing date: 2017-12-13
Publication date: 2020-05-15
Anticipated expiration: 2037-12-13
Also published as: CN108112154A

Abstract

The utility model provides a heavy ion synchrotron, includes the annular vacuum pipe, the annular vacuum pipe has a plurality of straight line ion beam sections and a plurality of curve ion beam section, wherein a plurality of straight line ion beam sections with a plurality of curve ion beam sections are arranged in turn, and heavy ion is injected from first straight line ion beam section, draws forth from another straight line ion beam section, and every curve ion beam section includes first dipolar magnet and the second dipolar magnet of series connection, and heavy ion is moved to the second dipolar magnet by first dipolar magnet, is provided with vertical correction magnet and vertical focusing quadrupole magnet between first dipolar magnet and the second dipolar magnet in proper order, and the straight line ion beam section of second dipolar magnet low reaches sets gradually horizontal correction magnet, sextupole magnet and horizontal focusing quadrupole magnet. The synchrotron of the invention has simple structure, can save processing cost, is convenient for the installation and debugging of equipment, is easier to achieve higher cumulative flow intensity, and can fully utilize the transverse acceptance of the synchrotron.

Description

Heavy ion synchrotron

Technical Field

The invention relates to the field of synchrotrons, in particular to a heavy ion synchrotron with an FODO structure.

Background

Because the irradiation of the heavy ion beam to the organism has the characteristics of reversed depth dose distribution, smaller side scattering, higher relative biological effect, lower oxygen increment ratio and the like, the heavy ion cancer therapy becomes an international advanced and effective cancer radiotherapy method. The beam energy of the common deep heavy ion cancer therapy is 120MeV/u-400 MeV/u.

The synchrotron is a device which can inject, accelerate and extract charged particle beams by controlling the time sequence structure of a front end injector, the magnetic field of a magnet of the synchrotron, a longitudinal high-frequency electric field, a beam diagnosis element, an injection element and the like. It is widely used in the fields of nuclear physics, atomic nucleus physics, material irradiation, biological irradiation, cancer treatment and the like. The positions of the magnet elements such as the dipolar magnet, the quadrupole magnet, the hexapole magnet and the like and the corresponding magnetic field intensity are reasonably arranged, so that the control on beam envelope can be realized, the uniform and slow extraction of the beam can be realized by utilizing a three-order resonance slow extraction system, and the medical heavy ion treatment requirement is met.

There are currently available medical synchrotron devices mainly of patent nos. 201010252492.5 and 201210264179.2. 201210264179.2 is very suitable for proton cancer treatment accelerator, and for heavy ion cancer treatment accelerator, although it is suitable, because of adopting 6 dipolar magnet structure, the single dipolar magnet weight is up to 20 tons, the bending radian is up to 60 degrees, it is not convenient for processing the magnet, also brings difficulty for magnet installation; patent 201010252492.5, however, uses 8 deflecting dipole magnets of 45 degrees and uses a cyclotron as an injector, so it is not easy to reach higher beam current intensity, resulting in longer treatment time. In addition, the scheme needs the electrostatic cutter to provide higher voltage because the deviation angle of the beam current relative to the central track of the synchrotron at the position of the electrostatic cutter. In the prior art, an accelerator adopting an FODO structure adopts a multi-turn injection mode, a slow-leading-out electrostatic cutter and a leading-out magnetic cutting iron are placed at a position where the envelope of a horizontal beam current is close to an average value, a convex rail is not adopted for slow leading-out, and the utilization rate of the transverse acceptance of the synchrotron is low.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a heavy ion synchrotron with an FODO structure, which can improve the injection gain to the maximum extent and realize the full utilization of the transverse receptivity of an accelerator device.

The heavy ion synchrotron comprises an annular vacuum pipeline, wherein the annular vacuum pipeline is provided with a plurality of linear ion beam sections and a plurality of curve ion beam sections, the plurality of linear ion beam sections and the plurality of curve ion beam sections are alternately arranged, heavy ions flow to a first curve ion beam section after being injected from the first linear ion beam section, are led out from another linear ion beam section after being accelerated, each curve ion beam section comprises a first dipolar magnet and a second dipolar magnet which are connected in series, the heavy ions run from the first dipolar magnet to the second dipolar magnet, a vertical correction magnet and a vertical focusing quadrupole magnet are sequentially arranged between the first dipolar magnet and the second dipolar magnet, and a horizontal correction magnet, a hexapole magnet and a horizontal focusing quadrupole magnet are sequentially arranged in the linear ion beam section at the downstream of the second dipolar magnet.

Preferably, the number of said rectilinear and curvilinear ion beam segments is six or eight.

Preferably, two of the curved ion beam segments comprise a six-pole magnet disposed between the vertical focusing quadrupole magnet and the second two-pole magnet.

Preferably, the ion beam implanter further comprises an injection cutting magnet, a stripping film device and a plurality of injection convex track magnets, wherein the injection cutting magnet is arranged in the first straight-line ion beam section, the stripping film device is arranged in the first two-pole magnet of the first curved ion beam section, and the first injection convex track magnet is arranged in the curved ion beam section upstream of the first straight-line ion beam section and is positioned between the vertical focusing quadrupole magnet and the second two-pole magnet; the second injection convex track magnet is arranged in the first curved beam section and is positioned between the vertical focusing quadrupole magnet and the second dipolar magnet; the third convex rail magnet is arranged at the second linear beam section and is positioned at the downstream of the horizontal focusing quadrupole magnet.

Preferably, the injection device may further comprise a fourth injection ledge magnet disposed in the first linear ion beam section upstream of the horizontal focusing quadrupole magnet. For example, between the horizontal focusing quadrupole magnet and the hexapole magnet, or between the horizontal corrector magnet and the second dipole magnet.

Preferably, the injection convex track magnet is in a ferrite structure, and preferably, the rise time of the magnetic field of the injection convex track magnet is less than 1ms, and the fall time of the magnetic field is less than 100 us.

Preferably, the ion beam extraction device further comprises an extraction device, the extraction device comprises an extraction electrostatic cutter, an extraction cutting magnet, a transverse excitation device and a plurality of extraction convex rail magnets, the extraction cutting magnet is arranged on a linear ion beam section for extracting heavy ions, the extraction electrostatic cutter is arranged on a linear ion beam section at the upstream of the linear ion beam section for extracting heavy ions, the transverse excitation device is arranged on any linear ion beam section, a first extraction convex rail magnet is arranged on the linear ion beam section at the upstream of the linear ion beam section for extracting heavy ions, a second extraction convex rail magnet is arranged on the linear ion beam section for extracting heavy ions and is positioned at the downstream of the extraction electrostatic cutter, a third extraction convex rail magnet is positioned at the linear ion beam section for extracting heavy ions and is positioned at the downstream of the extraction cutting magnet, and the first extraction convex rail magnet, The second leading-out convex rail magnet and the third leading-out convex rail magnet are arranged at the upstream of the adjacent curved ion beam section and are close to the first two-pole magnet.

Preferably, the extraction device further comprises a fourth extraction convex rail magnet, and the fourth extraction convex rail magnet is positioned on the linear ion beam section where the extraction electrostatic cutter is positioned and is positioned at the upstream of the horizontal focusing quadrupole magnet. For example, between the horizontal focusing quadrupole magnet and the hexapole magnet, or between the horizontal pitch magnet and the second dipole magnet.

Preferably, said extraction electrostatic cutter and said extraction cutting magnet are mounted in close proximity to a horizontal focusing quadrupole magnet to ensure that said extraction electrostatic cutter and said extraction cutting magnet are located as far as possible at the maximum horizontal envelope.

Preferably, the ion beam further comprises a high frequency accelerating device arranged in one linear ion beam segment.

Compared with the prior art, the invention has the following advantages:

1. a plurality of repeated FODO (Focus-Drift-Defocus-Drift) structures are adopted, and a magnetic focusing structure (lattice) is simple and convenient for beam debugging and installation;

2. the high flow intensity is easier to obtain by adopting stripping injection than multi-circle injection;

3. the layout of the extraction element is optimized, and a 3-bump (or 4-bump) extraction convex rail structure is adopted, so that the transverse acceptance of the synchrotron is fully utilized.

Drawings

FIG. 1 is an overall layout of the synchrotron of the present invention;

FIG. 2 is a diagram of the beam envelope in the synchrotron of the present invention;

FIG. 3 is a schematic view of the injection system and injection trajectory of the synchrotron of the present invention;

FIG. 4 is an envelope of injected beam current at the location of the electrostatic cutter and cutting magnet in the synchrotron of the present invention;

fig. 5 is an envelope of the slow-out beam and the circulating beam in the synchrotron of the present invention.

List of reference numerals:

1-12: dipolar magnet

13-24: four-pole magnet

25-32: six-pole magnet

33-44: calibration magnet

45-47: injection convex rail magnet

48: injection cutting magnet

49: stripping film device

50-52: magnet for leading out convex rail

53: leading-out electrostatic cutter

54: leading-out cutting magnet

55: transverse excitation device

56: high-frequency accelerator cavity

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

The heavy ion synchrotron of the invention utilizes a closed annular vacuum pipeline to provide a high vacuum environment for beam operation, adopts dipolar magnets to realize beam deflection, adopts quadrupole magnets to realize beam focusing, adopts hexapole magnets to realize chromaticity correction and beam resonance, and adopts corrective iron to perform closed-orbit correction.

Fig. 1 is a general layout diagram of the synchrotron, and it can be seen that the synchrotron has a hexagonal structure, and the dipole magnets and the quadrupole magnets are arranged very regularly. Starting from the six o' clock direction, rotating counterclockwise, the elements are: injection cut magnet 48, two-pole magnet 1, stripping film device 49, correction magnet 33, four-pole magnet 13, injection convex track magnet 46, two-pole magnet 2, correction magnet 34, six-pole magnet 25, four-pole magnet 14, injection convex track magnet 47, extraction convex track magnet 50, two-pole magnet 3, correction magnet 35, four-pole magnet 15, six-pole magnet 26, two-pole magnet 4, correction magnet 36, six-pole magnet 27, four-pole magnet 16, extraction electrostatic cut magnet 53, extraction convex track magnet 51, two-pole magnet 5, correction magnet 37, four-pole magnet 17, two-pole magnet 6, correction magnet 38, six-pole magnet 28, four-pole magnet 18, extraction cut magnet 54, extraction convex track magnet 52, two-pole magnet 7, correction magnet 39, four-pole magnet 19, two-pole magnet 8, correction magnet 40, six-pole magnet 29, magnet 20, high-frequency acceleration chamber 56, two-pole magnet 9, correction magnet 41, four-pole magnet 21, six-pole magnet 30, two-pole magnet 10, correction magnet 42, six-pole magnet 31, four-pole magnet 22, transverse excitation device 55, two-pole magnet 11, correction magnet 43, four-pole magnet 23, injection-land magnet 45, two-pole magnet 12, correction magnet 44, six-pole magnet 32, and four-pole magnet 24.

It can be seen that the synchrotron actually employs 6 repetitive linear units, each unit comprising two dipole magnets 1/2, 3/4, 5/6, 7/8, 9/10 and 11/12, two quadrupole magnets 13/14, 15/16, 17/18, 19/20, 21/22 and 23/24, one or two

hexapole magnets

25, 26, 27, 28, 29, 30, 31 and 32, a linear ion beam segment a, b, c, d, e and f having a length of about 3m, and two corrective irons 33/34, 35/36, 37/38, 39/40, 41/42 and 43/44. The magnets are alternately connected by vacuum pipes. The beam current is injected from the linear ion beam section a and is led out from the linear ion beam section d. The high frequency accelerator chamber 56 is disposed at the linear ion beam segment e.

The 12 dipole magnets each have a deflection angle of 30 degrees, and the 12 quadrupole magnets are 6 vertical focusing

quadrupole magnets

13, 15, 17, 19, 21 and 23, and 6 horizontal focusing

quadrupole magnets

14, 16, 18, 20, 22 and 24, and among the 8 hexapole magnets, 4

hexapole magnets

27, 31, 32 and 38 are used for driving beam resonance, 2 hexapole magnets 25 and 29 are used for chromaticity correction in the horizontal direction, 2

hexapole magnets

30 and 26 are used for chromaticity correction in the vertical direction, and the 12 correction magnets are 6

horizontal correction magnets

34, 36, 38, 40, 42 and 44, and 6

vertical correction magnets

33, 35, 37, 39, 41 and 43, respectively.

In each unit, a vertical focusing quadrupole magnet is located between two dipole magnets, and a vertical correction magnet is placed next to the vertical focusing quadrupole magnet, a horizontal focusing quadrupole magnet is located downstream of the two dipole magnets, and a hexapole magnet and a horizontal correction iron are installed between the horizontal focusing quadrupole magnet and the dipole magnets.

The arrangement of the vertical focusing quadrupole magnet and the horizontal focusing quadrupole magnet is opposite to that of the synchronous accelerator adopting an FODO structure in the prior art, and the focusing quadrupole magnet is arranged on the long linear ion beam section, so that the arrangement of an extraction element is facilitated.

The synchrotron of the invention is composed of 6 same FODO units, 6 vertical focusing quadrupole magnets and 6 horizontal focusing quadrupole magnets are respectively connected in series for power supply, thus saving the manufacturing cost of a power supply and being convenient for adjusting the working point. And each unit comprises two dipolar magnets, the length of each dipolar magnet is about 2m, the weight of each dipolar magnet is about 10t, and the installation of the dipolar magnets can be completed without a high-tonnage crane.

It should be noted that the number of the repeating linear units in the synchrotron of the present invention is not limited to 6, and may be, for example, 8.

Fig. 2 is a beam envelope of the synchrotron, in which the upper diagram is a beam envelope in the horizontal direction and the lower diagram is a beam envelope in the vertical direction, in which the emittance of the beams in the horizontal and vertical directions is 200/30pi, respectively, and the momentum dispersion of the beams is ± 0.3%.

As shown in fig. 1, the injection system includes 3 injection

convex rail magnets

45, 46, 47 and a stripping film device 49. The injection convex rail magnet adopts a ferrite structure, and the rise time of a magnetic field is required to be less than 1ms, and the fall time of the magnetic field is required to be less than 100 us. The stripping film device is positioned in the vacuum chamber of the dipolar magnet 1, the side surface installation of the stripping film is realized by punching holes on the transverse side surface of the dipolar magnet, and the layout of the injection system is shown in figure 3.

The injection mode of the prior synchrotron mainly comprises multi-circle injection, multiple times of multi-circle injection under the assistance of cooling action, stripping injection and the like, and the injection gain is generally about 15 times by adopting the multi-circle injection due to the restriction of the Living theorem; the adoption of multiple times and multiple circles can realize larger beam gain, but a phase space cooling device is needed, such as electronic cooling, random cooling and the like, the cooling device has higher technical difficulty and higher manufacturing cost, and is not suitable for being used on a medical heavy ion device; the stripping injection is a method for realizing the beam injection by breaking through the restriction of the Liuwei theorem and changing the running track of the beam by causing the beam to strike on a stripping film and losing the extranuclear electrons of the beam. More than 50 times the implant gain can be achieved more easily with a lift-off implant, which has been demonstrated in patent 201010252492.5.

The invention adopts a stripping injection mode, more particles are easier to inject under the same condition, and the simulation calculation and practical experience show that the gain of the number of particles obtained by adopting the stripping injection is at least doubled compared with that of the multi-circle injection.

Fig. 4 shows the injected beam envelope at the location of the electrostatic cutter and the cutting magnet, and it can be seen that both the electrostatic cutter and the cutting magnet are located at a greater horizontal envelope and near the maximum of the horizontal envelope. Generally, during slow extraction, the electrostatic cutter must be placed within the lateral acceptance of the synchrotron, otherwise, the beam current is severely lost during extraction. However, the electrostatic cutter is positioned within lateral acceptance, which in turn affects the acceptance of the implant beam, i.e., the implant beam can now utilize an aperture that is only a fraction of the synchrotron acceptance, with another fraction being "occupied" by the exiting electrostatic cutter. The solution to this problem is to use local raised rails during the extraction process. Namely, the electrostatic cutter is placed beyond the transverse acceptance of the synchrotron, and the transverse acceptance of the electrostatic cutter can not be occupied in the injection and acceleration processes. When the beam is to be led out, a 3-bump (or 4-bump) raised rail structure is adopted, so that the rail of the beam generates local bulge at the leading-out section, and enters an electrostatic cutter to be led out. Due to the adoption of the 3-bump raised track system, the lead-out electrostatic cutter can be completely positioned outside the envelope of the injected beam, namely the electrostatic cutter is positioned outside the transverse acceptance of the synchrotron, so that the transverse acceptance of the synchrotron is fully utilized.

As shown in FIG. 1, the lead-out system mainly comprises 3-bump

land track systems

50, 51 and 52, a transverse excitation system 55, a lead-out electrostatic cutter 53 and a lead-out cutting magnet 54. The lead-out convex rail adopts the design of a conventional magnet, and the rise time of a magnetic field is less than 50 ms; the transverse excitation is arranged on any long linear ion beam section, and is arranged on the f linear ion beam section in the figure; the extraction electrostatic cutter 53 and the extraction cutting magnet 54 are located at the long linear ion beam sections c and d, respectively, and are mounted next to the focusing quadrupole magnet.

The angles of the inlets of the electrostatic cutting plate and the magnetic cutting plate are consistent with the envelope of the beam current, so that the beam current vertically enters the cutter, and the highest extraction efficiency is ensured.

The leading-out element is arranged at the place with the maximum horizontal beam envelope, so that the voltage of the electrostatic cutter can be reduced more favorably, and the stable operation of a machine can be facilitated.

Generally, to separate the chromaticity correction and resonance drive functions of the synchrotron, the horizontal operating point of the machine is chosen to be around 5/3. And at the working point, 6 repeated FODO structures are adopted, and the phase shift of adjacent straight line sections is close to 90 degrees.

The electrostatic cutter and the cutting magnet are elements which must be adopted for slow extraction, the cutting magnet is arranged at the downstream of the electrostatic cutter, and after the beam current is deflected by the electrostatic cutter, a certain gap is generated between the beam current and the circulating beam at the position of the cutting magnet, and the gap is used for installing a magnetic cutting plate. The size of the gap is related to the envelope function of the position of the electrostatic cutter and the cutting magnet, the phase shift of the electrostatic cutter and the cutting magnet, and the like. The concrete relation is as follows:

β therein_ESAs a function of the horizontal envelope at the electrostatic cutter, β_MSAs a function of the horizontal envelope at the cutting magnet, (μ)_MS-μ_ES) Is the phase difference between the cutting magnet and the electrostatic cutter.

Under the same condition, the larger the horizontal envelope function of the position where the electrostatic cutter and the cutting magnet are positioned, and the closer the phase shift of the electrostatic cutter and the cutting magnet is to 90 degrees, the smaller the required kicking track angle of the electrostatic cutter is. The present invention satisfies exactly all of the above conditions.

Fig. 5 is a comparison of a slow-out beam envelope and a cyclic beam envelope. It can be seen from the figure that after the beam excited by the transverse excitation enters the electrostatic cutter, the beam deflects under the action of the high-voltage electric field of the electrostatic cutter, so as to be separated from the circulating beam, and then enters the cutting magnet so as to be led out to a high-energy beam line. At the cutting magnet, the outgoing beam and the circulating beam generate a sufficient separation distance, and a sufficient gap is reserved for installation of the magnetic cutting plate.

The synchrotron of the invention can meet the requirements of strong convection and energy of heavy ion clinical treatment, and can provide heavy ion beams with the requirements of energy, strong flow, beam uniformity and on-off time for heavy ion cancer treatment under the condition of saving construction cost as much as possible. Besides medical use, the synchrotron of the invention can also be applied to the fields of nuclear physics research, material irradiation, biophysical experiments and the like.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A heavy ion synchrotron, comprising:

the ion beam acceleration device comprises an annular vacuum pipeline, a plurality of ion beam acceleration units and a plurality of ion beam acceleration units, wherein the annular vacuum pipeline is provided with a plurality of linear ion beam sections and a plurality of curved ion beam sections, the linear ion beam sections and the curved ion beam sections are alternately arranged, heavy ions are injected from a first linear ion beam section, flow to a first curved ion beam section, are extracted from another linear ion beam section after acceleration is completed, each curved ion beam section comprises a first dipolar magnet and a second dipolar magnet which are connected in series, the heavy ions run from the first dipolar magnet to the second dipolar magnet, a vertical correction magnet and a vertical focusing quadrupole magnet are sequentially arranged between the first dipolar magnet and the second dipolar magnet, and a horizontal correction magnet, a hexapole magnet and a horizontal focusing quadrupole magnet are sequentially arranged in the linear ion beam section at the downstream of the second dipolar magnet;

an injection device comprising an injection cut magnet disposed in the first linear ion beam segment, a stripping film device disposed in the first dipole magnet of the first curved ion beam segment, and a plurality of injection convex track magnets disposed in the curved ion beam segment upstream of the first linear ion beam segment and between the vertical focusing quadrupole magnet and the second dipole magnet; the second injection convex track magnet is arranged in the first curved beam section and is positioned between the vertical focusing quadrupole magnet and the second dipolar magnet; the third injection convex track magnet is arranged at the second linear beam section and is positioned at the downstream of the horizontal focusing quadrupole magnet;

the leading-out device comprises a leading-out electrostatic cutter, a leading-out cutting magnet, a transverse excitation device and a plurality of leading-out convex rail magnets, wherein the leading-out electrostatic cutter and the leading-out cutting magnet are arranged close to the horizontal focusing quadrupole magnet so as to ensure that the leading-out electrostatic cutter and the leading-out cutting magnet are positioned at the maximum horizontal envelope position as far as possible.

2. The heavy ion synchrotron of claim 1, wherein said linear and curvilinear ion beam segments are six or eight in number.

3. The heavy ion synchrotron of claim 1, wherein the two curved ion beam segments comprise a hexapole magnet disposed between the vertical focusing quadrupole magnet and the second dipole magnet.

4. The heavy ion synchrotron of claim 1, wherein said injection means further comprises a fourth injection ledge magnet disposed in said first linear ion beam segment upstream of the horizontal focusing quadrupole magnet.

5. The heavy ion synchrotron of claim 1 or 4, wherein said injection ledge magnet is of ferrite construction.

6. The heavy ion synchrotron of claim 5, wherein said injection ledge magnet has a magnetic field rise time of less than 1ms and a magnetic field fall time of less than 100 us.

7. The heavy ion synchrotron of claim 1, wherein said extraction cut magnet is disposed on a linear ion beam segment from which heavy ions are extracted, said extraction electrostatic cutter is disposed on a linear ion beam segment upstream of a linear ion beam segment from which heavy ions are extracted, said lateral excitation means is disposed on any linear ion beam segment, a first extraction convex rail magnet is disposed on a linear ion beam segment upstream of a linear ion beam segment on which said extraction electrostatic cutter is disposed, a second extraction convex rail magnet is disposed on a linear ion beam segment on which said extraction electrostatic cutter is disposed and downstream of said extraction electrostatic cutter, a third extraction convex rail magnet is disposed on a linear ion beam segment from which heavy ions are extracted and downstream of said extraction cut magnet, said first extraction convex rail magnet, said second extraction convex rail magnet, and said third extraction convex rail magnet are disposed upstream of an adjacent curved ion beam segment, and is adjacent to the first dipole magnet.

8. The heavy ion synchrotron of claim 7, wherein said extraction means further comprises a fourth extraction male rail magnet located on the linear ion beam segment on which said extraction electrostatic cutter is located and upstream of the horizontal focusing quadrupole magnet.

9. The heavy ion synchrotron of claim 1, further comprising high frequency accelerating means disposed in one of the linear ion beam segments.