阅读说明：本技术 一种高梯度返波型行波加速器及其快速能量调节方法 (High-gradient backward wave type traveling wave accelerator and rapid energy adjusting method thereof ) 是由 窦为平 何源 王志军 黄燃 马力祯 石健 于 2020-12-30 设计创作，主要内容包括：本发明涉及一种高梯度返波型行波加速器及其快速能量调节方法,其由一系列反行波加速单元串联而成,每一反行波加速单元包括加速腔、盘片和反行波漂移管；加速腔为两端开口的筒形结构,盘片一体形成于加速腔内部,且盘片的中心开设有束流中心孔；反行波漂移管沿轴向固定在盘片的束流中心孔内,用于集中加速电场；在位于反行波漂移管两侧的盘片上对称地开设有两磁耦合孔,用于使相邻两个反行波加速单元的加速腔以磁耦合的方式工作；一系列反行波加速单元通过加速腔依次串联在一起,且相邻两个返波型行波加速器加速单元的反行波漂移管之间存在加速间隙。本发明可以提升加速梯度,缩短质子治疗直线加速器的长度,同时可以缩短能量切换时间,增加有效治疗时间。(The invention relates to a high-gradient backward wave type traveling wave accelerator and a rapid energy adjusting method thereof, which are formed by connecting a series of backward wave accelerating units in series, wherein each backward wave accelerating unit comprises an accelerating cavity, a disc and a backward wave drift tube; the accelerating cavity is of a cylindrical structure with openings at two ends, the disc is integrally formed in the accelerating cavity, and a beam central hole is formed in the center of the disc; the reverse traveling wave drift tube is axially fixed in a beam central hole of the disk and is used for concentrating an accelerating electric field; two magnetic coupling holes are symmetrically arranged on the disk sheets positioned on the two sides of the reverse traveling wave drift tube and used for enabling the accelerating cavities of two adjacent reverse traveling wave accelerating units to work in a magnetic coupling mode; a series of backward wave accelerating units are connected in series in sequence through accelerating cavities, and an accelerating gap exists between the backward wave drift tubes of two adjacent backward wave type traveling wave accelerator accelerating units. The invention can improve the acceleration gradient, shorten the length of the proton treatment linear accelerator, and simultaneously can shorten the energy switching time and increase the effective treatment time.)

1. A high-gradient backward wave type traveling wave accelerator is characterized in that the accelerator is formed by connecting a series of backward wave accelerating units (1) in series, and each backward wave accelerating unit (1) comprises an accelerating cavity (11), a disc (12) and a backward wave drift tube (13);

the acceleration cavity (11) is of a cylindrical structure with openings at two ends, the disc (12) is integrally formed inside the acceleration cavity (11), and a beam central hole is formed in the center of the disc (12); the reverse traveling wave drift tube (13) is axially fixed in a beam central hole of the disc (12) and is used for concentrating an accelerating electric field; two magnetic coupling holes (14) are symmetrically formed in the disk (12) positioned on two sides of the reverse wave drift tube (13) and used for enabling the acceleration cavities (11) of two adjacent reverse wave acceleration units (1) to work in a magnetic coupling mode;

therefore, a series of the backward wave accelerating units (1) are sequentially connected in series through the accelerating cavities (11) to form a high-gradient backward wave type traveling wave accelerator, and an accelerating gap exists between the backward wave drift tubes (13) of two adjacent backward wave type traveling wave accelerating units (1).

2. The traveling wave accelerator of high gradient backward wave type according to claim 1, wherein 12 to 20 backward wave accelerating units (1) are connected in series, and a power feeding unit and a power extraction unit are respectively added to the front and rear ends of the traveling wave accelerator of high gradient backward wave type;

the power feed-in unit mainly comprises an input waveguide and a first coupler, and the power feed-in unit mainly has the function of coupling radio-frequency power output from a radio-frequency power source from the input waveguide into the high-gradient backward wave type traveling wave accelerator through the first coupler so as to establish a backward wave field;

the power leading-out unit consists of an output waveguide and a second coupler and is mainly used for coupling residual radio frequency power in the high-gradient backward wave type traveling wave accelerator into the output waveguide through the second coupler so as to ensure that a pure backward wave field is formed in the high-gradient backward wave type traveling wave accelerator.

3. The high gradient backward-wave traveling wave accelerator according to claim 1, wherein one end of the accelerating cavity (11) has an annular positioning boss, and the other end of the accelerating cavity (11) has an annular positioning groove corresponding to the annular positioning boss, whereby two adjacent backward-wave traveling wave accelerator accelerating units (1) are completely assembled by the annular positioning boss and the annular positioning groove on the accelerating cavity (11).

4. The high-gradient backward-wave traveling wave accelerator according to claim 1, wherein the magnetic coupling holes (14) of two adjacent backward-wave traveling wave accelerator accelerating units (1) are arranged in a 90 ° staggered manner.

5. The high-gradient backward-wave traveling wave accelerator according to any one of claims 1 to 4, further comprising a timing system for controlling the timing relationship between the beam current and the high-frequency power, and a low-level control system for adjusting the magnitude and phase of the radio-frequency power.

6. A method for fast energy adjustment of high gradient backward type traveling wave accelerator as claimed in claim 5, wherein the method controls the time sequence between the beam and each high gradient backward type traveling wave accelerator by the timing system, and controls the power value and phase relationship of each high gradient backward type traveling wave accelerator by the low level system, so as to realize fast switching of several specific energies at the exit of multiple high gradient backward type traveling wave accelerators, and the switching time is in the order of microseconds.

7. The fast energy adjustment method according to claim 6, wherein the energy gain step size of the single high gradient backward type traveling wave accelerator is arbitrarily set in accordance with a pre-optimized value within a range of 2-10 MeV.

Technical Field

The invention relates to a proton treatment accelerator, in particular to a high-gradient backward wave type traveling wave accelerator and a rapid energy adjusting method thereof, belonging to the technical field of nuclear medicine.

Background

Current proton therapy accelerators typically employ cyclotrons and synchrotrons, while heavy ion accelerators typically employ synchrotrons. The cyclotron can provide continuous and stable beams, but the cyclotron is a weak focusing structure, has low transmission efficiency, can bring about more serious activation problems, and leads out energy to be fixed.

Although the energy of the synchrotron can be adjusted, the injection, energy rising and standard circulation of the synchrotron takes a long time, the transduction time is about the second level, the ineffective treatment time is increased, and the flow uniformity and flow strength of the extracted beam are low, so that the synchrotron cannot adapt to the requirements of quick and continuous treatment. In addition, the synchrotron occupies a large area, and the whole system architecture is complex.

The linear accelerator has the main advantages of small transverse size, easy extraction and injection, and almost no beam loss in the transmission and acceleration processes. Therefore, the application of the linear accelerator to the field of proton therapy is the main direction of research, in order to reduce the length of the accelerator, the commonly adopted accelerating structure is RFQ (Radio Frequency Quadrupole accelerator) + DTL (Drift Tube Linac) + CCL (Coupled Cavity Linac), the outlet energy of the accelerating structure is fixed, but the requirement of precise therapy is difficult to meet; the RFQ + DTL + disk-charge waveguide forward traveling wave is also considered, the scheme can realize the adjustment of energy, but the acceleration gradient is still low, the length of a 230MeV proton treatment accelerator still needs tens of meters, and the installation scale of a hospital is difficult to meet.

The existing energy regulation mainly uses an energy reduction sheet, the energy reduction sheet can bring the problem of activation, the size of a shielding system is increased, and the beam quality can be deteriorated after the energy reduction sheet is used. When the traveling wave accelerator is used, energy adjustment can be realized through the accelerator, the change of the energy at the outlet of the accelerator is completed by sweeping the cavity, the phase sweeping process usually needs a plurality of minutes, the power source is in a closed state and in a cold state for the cavity without loading a certain output energy point, when the cavity needs to be converted to another energy point, the cavity needs to be reloaded with power and is switched to a hot state, the power loading process needs a minute level, and the ineffective treatment time is increased.

Disclosure of Invention

In view of the above problems, it is an object of the present invention to provide a high gradient backward traveling wave accelerator, which can improve the acceleration gradient and shorten the length of a proton treatment linear accelerator; another objective of the present invention is to provide a fast energy adjusting method for the high gradient backward wave type traveling wave accelerator, which shortens the energy switching time and increases the effective treatment time.

In order to achieve the purpose, the invention adopts the following technical scheme: a high-gradient backward wave type traveling wave accelerator is formed by connecting a series of backward wave accelerating units in series, wherein each backward wave accelerating unit comprises an accelerating cavity, a disc and a backward wave drift tube; the disc is integrally formed in the accelerating cavity, and a beam central hole is formed in the center of the disc; the reverse traveling wave drift tube is axially fixed in a beam central hole of the disk and is used for concentrating an accelerating electric field; two magnetic coupling holes are symmetrically formed in the disc sheets positioned on two sides of the reverse wave drift tube and used for enabling the accelerating cavities of two adjacent reverse wave accelerating units to work in a magnetic coupling mode; therefore, a series of the backward wave accelerating units are sequentially connected in series through the accelerating cavities to form the high-gradient backward wave traveling wave accelerator, and an accelerating gap exists between the backward wave drift tubes of two adjacent backward wave traveling wave accelerating units.

The high-gradient backward wave type traveling wave accelerator is preferably formed by connecting 12-20 backward wave accelerating units in series, and a power feed-in unit and a power extraction unit are respectively added at the front end and the rear end of the high-gradient backward wave type traveling wave accelerator; the power feed-in unit mainly comprises an input waveguide and a first coupler, and the power feed-in unit mainly has the function of coupling radio-frequency power output from a radio-frequency power source from the input waveguide into the high-gradient backward wave type traveling wave accelerator through the first coupler so as to establish a backward wave field; the power leading-out unit consists of an output waveguide and a second coupler and is mainly used for coupling residual radio frequency power in the high-gradient backward wave type traveling wave accelerator into the output waveguide through the second coupler so as to ensure that a pure backward wave field is formed in the high-gradient backward wave type traveling wave accelerator.

Preferably, one end of the accelerating cavity is provided with an annular positioning boss, and the other end of the accelerating cavity is provided with an annular positioning groove corresponding to the annular positioning boss, so that two adjacent accelerating units of the backward wave type traveling wave accelerator are assembled through the annular positioning boss and the annular positioning groove on the accelerating cavity.

The high-gradient backward wave type traveling wave accelerator is characterized in that magnetic coupling holes in accelerating units of two adjacent backward wave type traveling wave accelerators are preferably arranged in a 90-degree staggered manner.

The high-gradient backward wave type traveling wave accelerator preferably further comprises a timing system and a low level control system, wherein the timing system is used for controlling the time sequence relation between beam current and high-frequency power, and the low level control system is used for adjusting the size and the phase of radio-frequency power.

The method controls the time sequence between the beam current and each high-gradient backward-wave type traveling wave accelerator through a timing system, and controls the power value and the phase relation of each high-gradient backward-wave type traveling wave accelerator through a low-level system so as to realize the rapid switching of a plurality of specific energies at the outlets of a plurality of high-gradient backward-wave type traveling wave accelerators, wherein the switching time is microsecond level.

According to the rapid energy adjustment method, preferably, the energy gain step length of a single high-gradient backward wave type traveling wave accelerator can be arbitrarily set within the range of 2-10MeV according to a pre-optimized value.

Due to the adoption of the technical scheme, the invention has the following advantages:

1. the high-gradient backward wave type traveling wave accelerator is additionally provided with the magnetic coupling hole on the disk and works in a magnetic coupling mode, so that a beam central hole can be made very small, the backward wave drift tube is additionally arranged on the high-gradient backward wave type traveling wave accelerator, an electric field is more concentrated between two adjacent drift tubes, the shunt impedance is improved by about one time, the effective shunt impedance can be more than 100M omega/M, and the effective acceleration gradient can reach 50-60 MV/M.

2. Compared with a double-period standing wave accelerating structure, the high-gradient backward wave type traveling wave accelerator has the advantages that the accelerating gradient is improved by 2-3 times, compared with a forward traveling wave accelerating structure, the accelerating gradient is improved by about 1 time, and the applicable energy is reduced to 30MeV, so that the characteristic of the high accelerating gradient can be fully utilized, and the length of a 230MeV linear accelerator is further reduced.

3. The rapid energy adjusting method shortens the energy switching time from a minute level to a microsecond level, increases the effective treatment time, can control the energy switching step length to be about 2MeV, can not use an energy reduction sheet any more, reduces the activation, and simplifies a shielding system.

Drawings

FIG. 1 is a schematic diagram of a three-dimensional structure of a high-gradient backward wave type traveling wave accelerator according to the present invention;

FIG. 2 is a top view of a high gradient backward wave type traveling wave accelerator according to the present invention;

FIG. 3 is a sectional view taken along line A-A of FIG. 2;

FIG. 4 is a sectional view taken along line B-B of FIG. 2;

fig. 5 is a time structure diagram of beam current and high frequency power.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. Meanwhile, in the description of the present invention, it is to be understood that the terms "upper", "lower", "inside", "outside", "front", "rear", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the scope of the present invention.

As shown in fig. 1 to 4, the high-gradient backward wave traveling wave accelerator provided by the present invention is formed by connecting a series of backward wave accelerating units 1 in series (only two are shown in the figure, but not limited thereto), and each backward wave accelerating unit 1 includes an accelerating cavity 11, a disk 12 and a backward wave drift tube 13. The acceleration cavity 11 is a cylindrical structure with openings at two ends, the disk 12 is integrally formed inside the acceleration cavity 11, and a beam central hole is formed in the center of the disk 12; the backward traveling wave drift tube 13 is axially fixed in a beam central hole of the disk 12 and is used for concentrating an accelerating electric field to increase the amplitude of the accelerating electric field, so that the accelerating capacity is improved; two magnetic coupling holes 14 are symmetrically arranged on the disk 12 at two sides of the backward wave drift tube 13 for enabling the accelerating cavities 11 of two adjacent backward wave accelerating units 1 to work in a magnetic coupling mode, so that the beam center hole can be made small, and the backward wave drift tube 13 is additionally arranged, so that an accelerating electric field is more concentrated between two adjacent backward wave drift tubes 13, therefore, compared with a forward traveling wave accelerator, the shunt impedance is improved by about one time, the effective shunt impedance can be more than 100M omega/M, and the effective accelerating gradient can reach 50-60 MV/M.

Therefore, a series of backward wave accelerating units 1 are connected in series in sequence through the accelerating cavities 11 to form a high-gradient backward wave accelerating unit, and an accelerating gap exists between the backward wave drift tubes 13 of two adjacent backward wave accelerating units 1.

In the above embodiment, preferably, a high-gradient backward wave type traveling wave accelerator is formed by connecting 12 to 20 backward wave accelerating units 1 in series, and a power feeding unit and a power extraction unit are respectively added to the front end and the rear end of the high-gradient backward wave type traveling wave accelerator. The power feed-in unit mainly comprises an input waveguide and a coupler, and the main function of the power feed-in unit is to couple the radio-frequency power output from the radio-frequency power source from the input waveguide to the high-gradient backward wave type traveling wave accelerator through the coupler so as to establish a backward wave field. The power leading-out unit consists of an output waveguide and a coupler and is mainly used for coupling residual radio frequency power in the high-gradient backward wave type traveling wave accelerator into the output waveguide through the coupler so as to ensure that a pure backward wave field is formed in the high-gradient backward wave type traveling wave accelerator.

In the above embodiment, it is preferable that one end of the acceleration cavity 11 has an annular positioning boss, and the other end of the acceleration cavity 11 has an annular positioning groove corresponding to the annular positioning boss, so that two adjacent backward-wave traveling wave accelerator acceleration units 1 are assembled by the annular positioning boss and the annular positioning groove on the acceleration cavity 11.

In the above embodiment, it is preferable that the magnetic coupling holes 14 of two adjacent backward-wave traveling wave accelerator acceleration units 1 are arranged in a 90 ° staggered manner.

In the above embodiment, preferably, the high-gradient backward wave type traveling wave accelerator further includes a timing system and a low-level control system, where the timing system is configured to control a time sequence relationship between the beam current and the high-frequency power, and the low-level control system is configured to adjust the magnitude and the phase of the radio-frequency power.

It should be noted that, in the energy adjustment process of the existing traveling wave accelerator, the radio frequency power of the accelerator is sequentially loaded, the phase of the accelerator is swept, the phase of the accelerator is set, and the adjustment output of the energy is obtained. The phase sweeping process usually requires several minutes, and for a cavity which does not need to be loaded at a certain output energy point, the power source is in a closed state and is in a cold state, when the cavity needs to be switched to another energy point, the cavity needs to be reloaded with power and is switched to a hot state, and the power loading process needs minutes. As shown in fig. 5, a time structure diagram of the beam current and the high frequency power is shown. The two dotted lines represent the temporal structure of the high frequency power, and the solid line represents the temporal structure of the beam current. When the beam current appears, the high-frequency power exists and reaches a preset value, and the high-gradient backward wave type traveling wave accelerator can obtain a preset energy gain. When the beam current appears, the high-frequency power does not exist or is not lower than the preset value, and the high-gradient backward wave type traveling wave accelerator can not obtain the energy gain or can obtain a small amount of energy gain.

Therefore, based on the high-gradient backward-wave traveling wave accelerator provided by the above embodiment, the present invention further provides a method for adjusting the fast energy of the high-gradient backward-wave traveling wave accelerator, the method controls the time sequence between the beam and each high-gradient backward-wave traveling wave accelerator through the timing system, and controls the power value and the phase relationship of each high-gradient backward-wave traveling wave accelerator through the low-level system, so that the fast switching of a plurality of specific energies can be realized at the outlets of a plurality of high-gradient backward-wave traveling wave accelerators, and the switching time is microsecond.

In the above embodiment, preferably, the energy gain step size of the single high-gradient backward-wave traveling wave accelerator (12-20 accelerating units) can be arbitrarily set in accordance with the pre-optimized value within the range of 2-10 MeV.

The fast energy adjustment method of the present invention is described below by taking an example of switching the beam current from 230MeV to 202MeV, and the specific process is as follows:

the method comprises the steps that firstly, a beam is accelerated to 230MeV from 70MeV, 16 high-gradient backward-wave type traveling wave accelerators are normally loaded, and a timing system enables the beam to stably sense a preset accelerating electric field when passing through the high-gradient backward-wave type traveling wave accelerators, so that stable acceleration is completed. If the beam current is to be quickly switched to 202MeV, the beam current cannot feel the accelerating electric field of the last 2 high-gradient backward wave type traveling wave accelerators through a timing system, and the response time of the process is nanosecond level; meanwhile, the phase relation between the 13 th high-gradient backward wave type traveling accelerator and the 14 th high-gradient backward wave type traveling accelerator is rapidly adjusted through a low level control system, so that the energy of the 14 th high-gradient backward wave type traveling accelerator is increased by only 2MeV, and the response time of the process is microsecond level. Thus, the microsecond switching of the beam current from 230MeV to 202MeV is completed.

It should be noted that the main reason why the present invention can complete the microsecond level switching of energy output is that when the high gradient backward wave type traveling wave accelerator is not in use, the high frequency power is still loaded, so that the loading time from the cold state to the hot state is not required, and the power amplitude and the phase of the high gradient backward wave type traveling wave accelerator at each energy point have preset values, and the phase sweeping process is not required, and the setting can be rapidly performed, so that the microsecond level switching of energy output can be realized.

In addition, if the treatment terminal needs to improve the energy controllable precision, an energy reduction sheet with a certain thickness can be matched on the basis of the rapid energy adjusting method, and the activation can be better controlled because the energy required to be reduced is low and the thickness required by the energy reduction sheet is low.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.