CN106163073B - A kind of line outbound course of middle energy superconduction bevatron - Google Patents
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Abstract
本发明涉及一种中能超导质子回旋加速器的束流引出方法，该方法引入一次谐波进动的方式增加引出圈间距，并结合超导回旋加速器的特点，在两个静电偏转板引出束流的基础上，在束流轨迹上设置多个小型无源磁通道，可进行类似束流线设计的方式进行引出路径上的束流相空间匹配，最大程度上减小偏转板后的束流损失，最终的引出效率可达到80％以上。
The invention relates to a beam extraction method of a medium-energy superconducting proton cyclotron. The method introduces a method of first-order harmonic precession to increase the distance between extraction circles, and combines the characteristics of a superconducting cyclotron to extract beams from two electrostatic deflection plates. Based on the current flow, multiple small passive magnetic channels are set on the beam trajectory, and the beam phase space matching on the extraction path can be carried out in a manner similar to the beam line design, so as to minimize the beam current behind the deflection plate Loss, the final extraction efficiency can reach more than 80%.
Description
技术领域technical field
本发明属于回旋加速器设计技术，具体涉及一种中能超导质子回旋加速器的束流引出方法。The invention belongs to cyclotron design technology, in particular to a beam extraction method of a medium-energy superconducting proton cyclotron.
背景技术Background technique
100-300MeV中能超导质子回旋加速器在核医学、航天军工和核物理基础研究等领域有广泛的应用。相对于常温质子回旋加速器而言，超导质子回旋加速器具有结构紧凑，运行功率损耗小的优点。其中，束流引出效率是此类加速器的核心指标之一。引出过程中损失的粒子打在加速器磁铁、高频腔等其它部件上，会影响部件的使用寿命和运行稳定性，同时加速器活化会使加速器保持较高的辐照剂量水平，不利于加速器发生故障后进行维修。特别是超导线圈恒温器内壁，长时间遭受束流轰击可能导致损坏，从而影响加速器的超导性，对加速器带来重大影响。100-300MeV medium-energy superconducting proton cyclotrons are widely used in the fields of nuclear medicine, aerospace military industry and basic research of nuclear physics. Compared with proton cyclotrons at room temperature, superconducting proton cyclotrons have the advantages of compact structure and low operating power loss. Among them, the beam extraction efficiency is one of the core indicators of this type of accelerator. The particles lost during the extraction process hit the accelerator magnet, high-frequency cavity and other components, which will affect the service life and operation stability of the components. At the same time, the activation of the accelerator will keep the accelerator at a high radiation dose level, which is not conducive to the failure of the accelerator. repairs afterwards. In particular, the inner wall of the superconducting coil thermostat may be damaged if subjected to beam bombardment for a long time, thereby affecting the superconductivity of the accelerator and having a major impact on the accelerator.
静电偏转板是质子回旋加速器中常用的束流引出方法。采用静电偏转电压向粒子施加向外的作用力，使粒子脱离加速区进入边缘场区域，边缘磁场快速下降，导致粒子最终偏转入加速器磁轭孔内引出。由于静电偏转板受到打火击穿的限制，产生的静电高压往往在60-100kV左右，对粒子的偏转力有限。粒子在经过偏转后，还有长时间运行在边缘磁场区域受到负磁场梯度的径向束流散焦作用。这时，往往可以在边缘场区域加入大范围的磁通道进行束流径向聚焦。即便如此，这种加速器的束流引出效率往往不高。比如，TBA C235质子治疗回旋加速器采用在谷区加入静电偏转板的方式，并在随后的磁极边缘场区域加入磁通道进行聚焦，运行时需要的偏转电压约为65kV，初期可达到的引出效率约为40％，经过长期运行优化后，引出效率可达到60％。Electrostatic deflection plates are commonly used beam extraction methods in proton cyclotrons. The electrostatic deflection voltage is used to exert an outward force on the particles, so that the particles leave the acceleration zone and enter the fringe field region, and the fringe magnetic field drops rapidly, resulting in the final deflection of the particles into the hole of the accelerator yoke. Since the electrostatic deflection plate is limited by the ignition breakdown, the generated electrostatic high voltage is often around 60-100kV, and the deflection force on the particles is limited. After the particles are deflected, they still have the radial beam defocusing effect of the negative magnetic field gradient in the fringe magnetic field region for a long time. At this time, it is often possible to add a large-scale magnetic channel in the fringe field region to focus the beam radially. Even so, the beam extraction efficiency of such accelerators is often not high. For example, the TBA C235 proton therapy cyclotron adopts the method of adding an electrostatic deflection plate in the valley area, and adding a magnetic channel in the subsequent magnetic pole edge field area for focusing. The deflection voltage required for operation is about 65kV, and the initial extraction efficiency is about It is 40%, and after long-term operation optimization, the extraction efficiency can reach 60%.
束流的引出效率η＝引出束流流强I/内部束流流强×100％。导致引出效率低的主要原因来自两方面。引出效率η与最后一圈引出轨道的间隔直接相关，轨道间隔小会造成较多离子撞在切割板上损失。要想达到较高的引出效率，必须使用轨道间距明显大于切割板的厚度，这就要求有较高的电压。而偏转板在过高电压情况下容易发生击穿，偏转板可耐高压是受到空间、材料选择和结构设计等限制的。其次，束流在引出路径上的匹配也对束流引出效率有重要影响，束流在运行过程中发生聚散焦，粒子往往损失在束流包络过大的位置上。Beam extraction efficiency η=extracted beam current intensity I/internal beam current intensity×100%. The main reasons leading to the low eliciting efficiency come from two aspects. The extraction efficiency η is directly related to the spacing of the last extraction track, and a small track spacing will cause more ions to hit the cutting board and be lost. In order to achieve higher extraction efficiency, the track spacing must be significantly greater than the thickness of the cutting board, which requires a higher voltage. However, the deflection plate is prone to breakdown when the voltage is too high, and the high voltage resistance of the deflection plate is limited by space, material selection, and structural design. Secondly, the matching of the beam on the extraction path also has an important impact on the efficiency of the beam extraction. The beam is focused and defocused during operation, and the particles are often lost at the position where the beam envelope is too large.
发明内容Contents of the invention
本发明的目的在于针对目前常用的中能质子回旋加速器中导致引出效率低的问题，提供一种可实现引出效率大于80％的中能超导质子回旋加速器的束流引出方法。The object of the present invention is to solve the problem of low extraction efficiency in the currently commonly used intermediate-energy proton cyclotron, and provide a beam extraction method for an intermediate-energy superconducting proton cyclotron that can achieve an extraction efficiency greater than 80%.
本发明的技术方案如下：一种中能超导质子回旋加速器的束流引出方法，包括如下步骤：The technical scheme of the present invention is as follows: a beam extraction method of a medium-energy superconducting proton cyclotron, comprising the following steps:
(1)计算加速器的静态平衡轨道，找到径向振荡频数υr＝1的半径位置，在该半径位置附近放置一次谐波，调节一次谐波振幅幅值和相位，使圈间距尽量分离的同时保证分离后的束流包络尽量小，确定最佳的一次谐波分布；(1) Calculate the static balance orbit of the accelerator, find the radial position where the radial oscillation frequency υ r = 1, place the first harmonic near the radial position, adjust the amplitude and phase of the first harmonic, and make the circle spacing as far as possible while separating Ensure that the beam envelope after separation is as small as possible to determine the best first harmonic distribution;
(2)在紧邻的两个磁极峰区各放置一个静电偏转板，第一个静电偏转板入口放置在两圈束流之间，调节静电偏转板曲率半径，使静电偏转板形状与束流轨迹形状匹配良好，调节两个静电偏转板电压，使束流正好从磁铁引出孔引出；(2) An electrostatic deflection plate is placed in each of the two adjacent magnetic pole peaks, the entrance of the first electrostatic deflection plate is placed between the two circles of beam current, and the curvature radius of the electrostatic deflection plate is adjusted so that the shape of the electrostatic deflection plate is consistent with the beam trajectory The shape is well matched, and the voltage of the two electrostatic deflectors is adjusted to make the beam current just lead out from the magnet lead-out hole;
(3)在引出偏转板后的中心粒子轨迹上，逐一加入若干个小型磁通道，调节磁通道的尺寸和磁场梯度，直到径向和轴向束流包络的聚焦良好；(3) Add several small magnetic channels one by one on the central particle trajectory after the deflection plate is drawn out, and adjust the size and magnetic field gradient of the magnetic channels until the radial and axial beam envelopes are well focused;
(4)重新调整静电偏转板电压，并调节各个磁通道的位置使束流从磁通道中心通过，反复调整直到束流正好能够从磁铁引出孔引出。(4) Readjust the voltage of the electrostatic deflection plate, and adjust the position of each magnetic channel so that the beam current passes through the center of the magnetic channel, and adjust repeatedly until the beam current can just be drawn out from the magnet outlet hole.
进一步，如上所述的中能超导质子回旋加速器的束流引出方法，步骤(1)中所述的圈间距的表达式如下：Further, the above-mentioned beam extraction method of the medium-energy superconducting proton cyclotron, the expression of the circle spacing described in step (1) is as follows:
Δr＝Δrseo+Δx sin(2πn(vr-1))+2π(vr-1)x cos(2πn(vr-1))Δr＝Δr seo +Δx sin(2πn(v r -1))+2π(v r -1)x cos(2πn(v r -1))
式中，r为粒子在回旋加速器中的径向位置，rseo为平衡轨道半径，vr为径向振荡频数，x为径向振荡振幅，Δx为相邻两圈径向振荡振幅的变化，n为束流的圈数；In the formula, r is the radial position of the particle in the cyclotron, r seo is the radius of the equilibrium orbit, v r is the radial oscillation frequency, x is the radial oscillation amplitude, Δx is the change of the radial oscillation amplitude between two adjacent circles, n is the number of turns of the beam;
Δrseo为能量增益带来的圈间距，第二项为共振使振荡振幅增加带来的圈间距，第三项为进动带来的圈间距；Δr seo is the loop spacing brought by energy gain, the second item is the loop spacing brought about by the increase of oscillation amplitude caused by resonance, and the third item is the loop spacing brought by precession;
所述的进动带来的圈间距与引入一次谐波的振幅与相位有关，根据多粒子跟踪模拟确定最佳的一次谐波振幅和相位。The ring spacing brought about by the precession is related to the amplitude and phase of the first harmonic, and the optimal amplitude and phase of the first harmonic are determined according to the multi-particle tracking simulation.
进一步，如上所述的中能超导质子回旋加速器的束流引出方法，步骤(2)中所述的静电偏转板的电场由下式计算得到：Further, in the beam extraction method of the above-mentioned medium-energy superconducting proton cyclotron, the electric field of the electrostatic deflection plate described in step (2) is calculated by the following formula:
式中，q、Ek为粒子的电荷和动能，ρ、分别为偏转板的曲率半径和角宽度，Δs为偏转板出口处粒子的径向偏移。In the formula, q, E k are the charge and kinetic energy of the particle, ρ, are the radius of curvature and angular width of the deflector, respectively, and Δs is the radial deviation of the particles at the exit of the deflector.
进一步，如上所述的中能超导质子回旋加速器的束流引出方法，步骤(3)中所述的磁通道由三块沿束流方向设置的铁块组成，其中一块铁块朝向束流的表面积较大，另外两块铁块朝向束流的表面积较小，表面积较大的铁块位于束流的内侧，另外两块表面积较小的铁块位于束流的外侧，所述的两块表面积较小的铁块呈上、下对称布置，束流从三块铁块形成的中间空隙通过。Further, the above-mentioned method for extracting the beam of the medium-energy superconducting proton cyclotron, the magnetic channel described in step (3) is composed of three iron blocks arranged along the direction of the beam, and one of the iron blocks faces the direction of the beam. The surface area is larger, and the surface area of the other two pieces of iron toward the beam is smaller. The iron piece with a larger surface area is located on the inside of the beam, and the other two iron pieces with a smaller surface area are located on the outside of the beam. The two surface areas The smaller iron blocks are symmetrically arranged up and down, and the beam passes through the middle gap formed by the three iron blocks.
本发明的有益效果如下：本发明在传统偏转板和大型磁通道引出方法的基础上，引入了一次谐波进动的方法增加引出圈间距，并结合超导回旋加速器的特点，采用多个小型无源磁通道，可进行类似束流线设计的方式进行引出路径上的束流相空间匹配，最大程序上减小偏转板后的束流损失，最终的引出效率可达到80％以上。The beneficial effects of the present invention are as follows: On the basis of the traditional deflection plate and large-scale magnetic channel extraction method, the present invention introduces the method of first harmonic precession to increase the spacing between the extraction circles, and combines the characteristics of the superconducting cyclotron to adopt multiple small The passive magnetic channel can match the phase space of the beam on the extraction path in a manner similar to the design of the beam line, and reduce the beam loss behind the deflection plate to the greatest extent, and the final extraction efficiency can reach more than 80%.
附图说明Description of drawings
图1为本发明束流引出方法的流程图；Fig. 1 is a flow chart of the beam extraction method of the present invention;
图2为本发明所采用的小型磁通道的结构示意图；Fig. 2 is the structural representation of the small-sized magnetic channel that the present invention adopts;
图3为基于双静电偏转板和多个磁通道的束流引出方法元件布局示意图；Figure 3 is a schematic diagram of the component layout of the beam extraction method based on double electrostatic deflection plates and multiple magnetic channels;
图4为基于双静电偏转板(ESD1-2)和6个磁通道(MC1-6)引出轨迹上的束流包络示意图。Fig. 4 is a schematic diagram of the beam current envelope on the extraction track based on double electrostatic deflection plates (ESD1-2) and six magnetic channels (MC1-6).
具体实施方式Detailed ways
下面结合附图和实施例对本发明进行详细的描述。The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.
如图1所示，本发明提出的中能超导质子回旋加速器的束流引出方法的流程如下：As shown in Figure 1, the flow process of the beam extraction method of the medium-energy superconducting proton cyclotron proposed by the present invention is as follows:
首先，结合加速器磁场数据，采用CYCLONE程序计算加速器的静态平衡轨道，找到径向振荡频数υr＝1的半径位置，在该半径位置附近放置一次谐波，分布函数如下：Firstly, combined with the magnetic field data of the accelerator, the CYCLONE program is used to calculate the static equilibrium orbit of the accelerator, find the radial position where the radial oscillation frequency υ r = 1, and place the first harmonic near this radial position, the distribution function is as follows:
其中，为一次谐波的相位，b(r-r0)为一次谐波的振幅分布函数，r0为一次谐波的中心位置，r为粒子在回旋加速器中的径向位置。r由下式表示：in, is the phase of the first harmonic, b(rr 0 ) is the amplitude distribution function of the first harmonic, r 0 is the center position of the first harmonic, and r is the radial position of the particle in the cyclotron. r is represented by the following formula:
r＝rseo+x sin(vrθ)r＝r seo +x sin(v r θ)
rseo为该能量对应的平衡轨道半径，vr为径向振荡频数，x为径向振荡振幅，(r，θ)为极坐标下粒子的位置。对上式求微分，假定vr≈1，可以得到第n圈的圈间距：r seo is the radius of the equilibrium orbit corresponding to the energy, v r is the frequency of radial oscillation, x is the amplitude of radial oscillation, and (r, θ) is the position of the particle in polar coordinates. Differentiate the above formula, assuming that v r ≈ 1, the circle spacing of the nth circle can be obtained:
Δr＝Δrseo+Δx sin(2πn(vr-1))+2π(vr-1)x cos(2πn(vr-1))Δr＝Δr seo +Δx sin(2πn(v r -1))+2π(v r -1)x cos(2πn(v r -1))
上式中，Δx为相邻两圈径向振荡振幅的变化，Δrseo为能量增益带来的圈间距，第二项为共振使振荡振幅增加带来的圈间距，第三项则为进动带来的圈间距。在超导质子回旋加速器中，能量增益带来的圈间距有限。由于等时性的要求，υr在加速过程中随着半径(能量)增加且大于1，直到接近磁极边缘，υr逐渐下降。在υr＝1的半径位置上加入一次谐波，激发束流径向振荡振幅，而在υr下降到约0.8时，可以产生较大的进动圈间距。In the above formula, Δx is the change of the radial oscillation amplitude of two adjacent circles, Δr seo is the circle spacing brought about by energy gain, the second term is the circle spacing brought about by the increase of the oscillation amplitude caused by resonance, and the third term is the precession Bring the circle spacing. In a superconducting proton cyclotron, the energy gain is limited by the circle spacing. Due to the requirement of isochronism, υ r increases with the radius (energy) and is greater than 1 during the acceleration process, until it approaches the edge of the magnetic pole, υ r gradually decreases. Adding the first harmonic at the radial position of υ r =1 excites the radial oscillation amplitude of the beam, and when the υ r drops to about 0.8, a larger precession circle spacing can be produced.
通过调节一次谐波振幅幅值和相位，使圈间距尽量分离的同时保证分离后的束流包络尽量小，确定最佳的一次谐波分布。加速器中引入一次谐波可以采用调节线圈和调节棒的方法，这里不作特别要求。By adjusting the amplitude and phase of the first harmonic, the circle spacing is separated as much as possible and the beam envelope after separation is kept as small as possible to determine the best first harmonic distribution. The first harmonic can be introduced into the accelerator by means of adjusting coils and adjusting rods, and there is no special requirement here.
其次，在紧邻的两个峰区各放置一个偏转板，第一个偏转板入口放置在两圈束流之间，调节偏转板曲率半径，使偏转板形状与束流轨迹形状匹配良好，调节两个偏转板电压，使束流正好从磁铁引出孔引出。Secondly, place a deflection plate in each of the two adjacent peaks, and place the entrance of the first deflection plate between the two circles of beams. Adjust the radius of curvature of the deflection plate to make the shape of the deflection plate match the shape of the beam trajectory well. A deflection plate voltage, so that the beam is just drawn out from the magnet lead-out hole.
在束流经过进动作用后，为了使粒子产生足够的向外偏转力，在磁极峰区和紧邻的下一个磁极峰区各放置一块静电偏转板。静电偏转板主要由接地切割板和负高压电极组成，电极形状为圆弧，曲率半径设计为与束流轨迹最为匹配的形状；束流入口处的切割板厚度要求小于0.2mm，尽量减小束流打在切割板上。静电偏转板的电场可由下式计算所得：After the beam passes through the precession, in order to make the particles generate sufficient outward deflection force, an electrostatic deflection plate is placed in the magnetic pole peak area and the next magnetic pole peak area next to each other. The electrostatic deflection plate is mainly composed of a grounding cutting plate and a negative high-voltage electrode. The shape of the electrode is an arc, and the radius of curvature is designed to best match the beam trajectory; Stream hit on a cutting board. The electric field of the electrostatic deflection plate can be calculated by the following formula:
其中，q、Ek为粒子的电荷和动能，ρ、分别为偏转板的曲率半径和角宽度，Δs为偏转板出口处粒子的径向偏移。越高的电压可以使粒子最大程度上往外偏移，有利于引出。但偏转板的耐压能力受到真空环境、材料和机械结构的影响，加速器稳定性要求偏转板电压一般要求小于70kV。Among them, q, E k are the electric charge and kinetic energy of particle, ρ, E k are the radius of curvature and angular width of the deflector, respectively, and Δs is the radial deviation of the particles at the exit of the deflector. A higher voltage can make the particles move outward to the greatest extent, which is beneficial to extraction. However, the withstand voltage of the deflector is affected by the vacuum environment, material and mechanical structure, and the stability of the accelerator requires that the voltage of the deflector is generally less than 70kV.
接下来，根据束流的散焦情况，在引出偏转板后的中心粒子轨迹上，逐一加入小型磁通道，采用多粒子跟踪的方式，调节磁通道的尺寸，改变磁场梯度大小，直到径向和轴向束流包络的聚焦良好。Next, according to the defocusing situation of the beam, small magnetic channels are added one by one on the central particle trajectory after the deflection plate is drawn out, and the size of the magnetic channel is adjusted by using the multi-particle tracking method, and the magnetic field gradient is changed until the radial and The axial beam envelope is well focused.
在经过偏转板后的束流轨迹上增加多个小型引出磁通道。由于超导加速器中的磁场较高，磁通道在磁场中很容易会产生磁化，因此磁通道可以是无源的，即不需要通电。磁通道在粒子轨迹附近产生的磁场可以表示为：A plurality of small extraction magnetic channels are added on the beam trajectory after passing the deflection plate. Due to the high magnetic field in the superconducting accelerator, the magnetic channel is easily magnetized in the magnetic field, so the magnetic channel can be passive, that is, it does not need to be powered. The magnetic field generated by the magnetic channel near the particle trajectory can be expressed as:
Bz＝b+kxB z =b+kx
其中，x为垂直于粒子轨迹的距离，b、k分别磁通道产生的二极和四极磁场分量。由于磁铁完全饱和，小型磁通道仅对束流轨迹附近的磁场有影响，对主磁场的影响很小。因此，可以在引出轨迹上放置多块小型磁通道，其作用类似于束流线上的四极透镜，调节各个磁通道的尺寸和磁场梯度，优化束流包络，完成引出轨迹上的束流匹配，可以最大程度上提高束流的引出效率。Among them, x is the distance perpendicular to the particle trajectory, b and k are the dipole and quadrupole magnetic field components generated by the magnetic channel, respectively. Since the magnets are fully saturated, the small magnetic channel only has an effect on the magnetic field near the beam trajectory and has little effect on the main magnetic field. Therefore, multiple small magnetic channels can be placed on the extraction track, which acts like a quadrupole lens on the beam line, adjusts the size and magnetic field gradient of each magnetic channel, optimizes the beam envelope, and completes the beam on the extraction track. Matching can maximize the extraction efficiency of the beam.
小型磁通道的结构如图2所示，由三块沿束流11方向设置的铁块组成，其中一块铁块12朝向束流11的表面积较大，另外两块铁块13朝向束流11的表面积较小，表面积较大的铁块12位于束流的内侧，另外两块表面积较小的铁块13位于束流的外侧，所述的两块表面积较小的铁块13呈上、下对称布置，束流11从三块铁块形成的中间空隙通过。为了使磁通道产生的磁场对主磁场的影响足够小并通过束流，要求该区域孔径尺寸在5-7mm，磁通道的长度为10mm-20mm，产生的磁场梯度范围为1-5kGs/cm。小型磁通道的具体描述可参见申请人同期申请的专利“适用于200-250MeV超导质子回旋加速器束流引出的超小型磁通道”。The structure of the small-sized magnetic channel is shown in Figure 2. It consists of three iron blocks arranged along the direction of the beam 11. One of the iron blocks 12 has a larger surface area facing the beam 11, and the other two iron blocks 13 face the direction of the beam 11. The surface area is smaller, and the iron block 12 with a larger surface area is located on the inside of the beam, and the other two iron blocks 13 with a smaller surface area are located on the outside of the beam, and the two iron blocks 13 with a smaller surface area are symmetrical up and down Arranged, the beam 11 passes through the middle gap formed by the three iron blocks. In order to make the magnetic field generated by the magnetic channel have a small enough influence on the main magnetic field and pass the beam, the aperture size of this area is required to be 5-7mm, the length of the magnetic channel is 10mm-20mm, and the magnetic field gradient generated is in the range of 1-5kGs/cm. For the specific description of the small magnetic channel, please refer to the patent "ultra-small magnetic channel suitable for 200-250 MeV superconducting proton cyclotron beam extraction" filed by the applicant at the same time.
采用小型磁通道的方式进行聚束的实施例如图3所示，图中1为磁极，超导质子回旋加速器的质子由两个静电偏转板2、3引出，在出口位置放置一个磁通道元件4，随后在引出轨迹10上依次放置五个磁通道5、6、7、8、9进一步聚束。由于磁通道很小，可以通过非导磁材料进行封装，固定在恒温器内壁上，安装非常方便。The embodiment of beamforming in the form of a small magnetic channel is shown in Figure 3, in which 1 is the magnetic pole, the protons of the superconducting proton cyclotron are drawn out by two electrostatic deflection plates 2, 3, and a magnetic channel element 4 is placed at the exit position , and then sequentially place five magnetic channels 5, 6, 7, 8, 9 on the lead-out track 10 for further bunching. Because the magnetic channel is very small, it can be packaged by non-magnetic conductive material and fixed on the inner wall of the thermostat, so the installation is very convenient.
最后，由于磁通道不能完全等效为磁四极透镜，其中还有二极分量，意味着磁通道不仅影响束流包络，对束流轨迹也是有影响的，因此，加入磁通道调节完束流包络后，依然要重新调节偏转板电压使束流正好从磁轭引出孔内引出。因此，束流包络匹配是个迭代的过程，直到满足所有要求(偏转板电压、引出轨迹和束流包络)的设计结果产生。Finally, since the magnetic channel cannot be completely equivalent to a magnetic quadrupole lens, there is a dipole component in it, which means that the magnetic channel not only affects the beam envelope, but also has an impact on the beam trajectory. Therefore, adding a magnetic channel to adjust the beam After the current envelope, it is still necessary to re-adjust the voltage of the deflection plate to make the beam current just lead out from the lead-out hole of the yoke. Therefore, beam envelope matching is an iterative process until a design result that satisfies all requirements (deflector voltage, extraction trajectory, and beam envelope) is produced.
实施例Example
下面介绍一个具体的实例，某超导质子回旋加速器可引出240MeV的质子束，采用四叶片螺旋扇结构，磁极半径为85cm。根据有限元模拟给出的磁场计算加速器的静态束流动力学，得到加速器υr＝1的位置为80.4cm，在r＝79cm位置加入一次谐波。调节一次谐波相位，发现当一次谐波相位为135°时，引出束流圈间距较大，且引出后进入偏转板的束流包络可控。在紧邻的两个磁极峰区各放置一个偏转板，偏转板形状和电压设计成使束流恰好通过且损失最小。根据CYCLONE程序进行多粒子跟踪光学匹配，多次迭代的结果表明，该加速器需要6块小型磁通道进行聚束，完成匹配后的引出束流包络如图4所示。A specific example is introduced below. A superconducting proton cyclotron can extract a 240MeV proton beam. It adopts a four-blade spiral fan structure and the magnetic pole radius is 85cm. The static beam dynamics of the accelerator is calculated according to the magnetic field given by the finite element simulation, and the position of the accelerator υ r =1 is 80.4cm, and the first harmonic is added at the position of r=79cm. Adjusting the phase of the first harmonic, it is found that when the phase of the first harmonic is 135°, the distance between the extracted beam current coils is relatively large, and the envelope of the beam entering the deflection plate after extraction is controllable. A deflection plate is placed in each of the adjacent two magnetic pole peaks, and the shape and voltage of the deflection plate are designed to allow the beam to pass just right with minimal loss. The multi-particle tracking optical matching is carried out according to the CYCLONE program. The results of multiple iterations show that the accelerator needs 6 small magnetic channels for beamforming. The extracted beam envelope after matching is shown in Figure 4.
完成设计后，从加速器中心区进行大量粒子的跟踪，结果表明，引出过程中每个偏转板上的束流损失均小于10％，而通过偏转板后由于束流匹配良好，几乎没有束流损失，束流引出效率可达80％以上。After the design is completed, a large number of particles are tracked from the central area of the accelerator. The results show that the beam loss on each deflection plate is less than 10% during the extraction process, and there is almost no beam loss after passing through the deflection plate due to the good beam matching. , The beam extraction efficiency can reach more than 80%.
显然，本领域的技术人员可以对本发明进行各种改动和变型而不脱离本发明的精神和范围。这样，倘若对本发明的这些修改和变型属于本发明权利要求及其同等技术的范围之内，则本发明也意图包含这些改动和变型在内。Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these modifications and variations.
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| US10375815B2 (en) | 2017-11-30 | 2019-08-06 | Hefei Cas Ion Medical And Technical Devices Co., Ltd. | Method for adjusting particle orbit alignment by using first harmonic in cyclotron |
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| CN109451648B (en) * | 2018-11-27 | 2019-10-15 | 中国原子能科学研究院 | A high-current circular accelerator extraction structure and method |
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