高能同步辐射光源直线加速器初期调束取得重要进展

高能同步辐射光源（HEPS）是中国第一台第四代高能同步辐射光源,其加速器由直线加速器、增强器、储存环及输运线组成。报道了HEPS直线加速器的初期束流调试重要进展。HEPS直线加速器是一台500 MeV S波段常温直线加速器,由热阴极电子枪、聚束系统、主直线加速器构成。在按时完成设备加工、安装和老练的基础上,于2023年3月9日启动束流调试,当天实现束流全线贯通。3月14日束流能量达到500 MeV,束团电荷量达到2.5 nC。经过测量,直线加速器出口束流能散0.4%,能量稳定度0.06%,水平和垂直几何发射度分别为233 nm和145 nm。目前直线加速器束团电荷量可达到7.0 nC,相关束流调试正在进行。     

直线感应加速器束包络数值计算模型

给出的直线感应加速器束输运的计算模型,能够计算束流从注入器经加速器直到最后聚焦的束包络.利用该编码可以方便地研究各种磁场位形及隙压参数对束流输运的影响.作为算例,给出了束流为3kA在长达40余米直线感应加速器的多种磁场位形下的束包络.     

BEPCⅡ直线加速器发射度测量

BEPCⅡ直线加速器采用改变四极磁铁励磁电流,测量获取的束流横截面荧光图像得到束流包络,进而通过对束流包络和励磁电流的拟合计算得到束流发射度和Twiss参数.在BEPCⅡ直线加速器的改进过程中,发现并解决了影响发射度测量结果准确性的多个问题,改进了束流横截面测量方法和发射度计算方法,提高了测量结果的准确性.根据BEPCⅡ直线加速器的具体情况,还编写了束流截面测量程序和发射度计算程序,提高了发射度的测量和计算速度,方便了发射度测量实验的使用.     

上海光源直线加速器的能量反馈控制

海光源恒流注入的运行模式,需要直线加速器提供持续、稳定和高品质的束流。阐述了八条形电极束流位置探测器(BPM)的工作原理及其对直线加速器至增强器低能运输线的束流进行能散的测量,并以（微波）幅度或相位作为调节参数,采用比例积分(PI)控制算法对束流能散进行反馈控制,实现了束流能量的长期稳定性,保证了直线加速器束流的高效率注入。     

BEPCⅡ直线加速器发射度测量

BEPCⅡ直线加速器采用改变四极磁铁励磁电流, 测量获取的束流横截面荧光图像得到束流包络, 进而通过对束流包络和励磁电流的拟合计算得到束流发射度和Twiss参数. 在BEPCⅡ直线加速器的改进过程中, 发现并解决了影响发射度测量结果准确性的多个问题, 改进了束流横截面测量方法和发射度计算方法, 提高了测量结果的准确性. 根据BEPCⅡ直线加速器的具体情况, 还编写了束流截面测量程序和发射度计算程序, 提高了发射度的测量和计算速度, 方便了发射度测量实验的使用.     

BEPCⅡ直线加速器重大改造和束流调试进展

BEPCⅡ直线加速器的重大改造旨在获得高流强、小发射度和小能散的正负电子束, 以满足对撞机亮度提高两个两级的要求. 这对直线加速器各系统和束流物理是一个挑战. 文章介绍了直接决定束流性能的新电子源、新正电子源、新微波功率源、相位控制系统和束流测量系统等的改造情况; 叙述了束流物理研究; 介绍了束流调试进展情况和进一步改进计划.     

准周期聚焦–加速耦合系统的均温设计方法

强流质子直线加速器要求严格控制束流损失和束流发射度增长.理论已经证明,强的空间电荷作用在不同自由度之间的耦合,会因为其间的温度差异,通过束流的相干不稳定性,使束流发射度增长.因此,有必要按照均温的原则设计强流加速器.但是,由于质子直线加速器的各种加速结构均为准周期耦合系统,使得均温设计十分繁琐而难以达到完全均温.我们利用国际上通用的束流动力学软件TRACE3-D,给它补充了均温设计功能,通过与PARMILA程序的配合使用,可以方便地在加速器设计中实现均温条件.本文将介绍我们对TRACE3-D的修改补充,并以强流质子直线加速器设计实例,说明均温设计的必要性.     

基于多级级联BP神经网络的加速器束流轨道预测

加速器束流轨道校正对于加速器稳定运行具有非常重要的作用,精确预测加速器束流轨道的变化对于实现束流自动化校准也具有重要意义。通过对束流轨道变化的准确预测,可以为调整加速器控制参数提供可靠的信息,从而实现对束流的精确控制和调节。通过研究束流在直线加速器中等能量传输段的传输过程,利用模拟加速器数据,基于多级级联的反向传播（BP）神经网络搭建了加速器束流轨道预测模型,能够实现对束流轨道参数的预测。结果表明,与采用传统单隐层BP神经网络建立的预测模型相比,多级级联BP神经网络能够实现更高的预测精度与可靠性,为直线加速器中等能量传输段的优化设计和束流轨道自动化校准提供了一种有效的方法。     

直线感应加速器束流崩溃不稳定性数值模拟

在理论分析的基础上,开发了直线感应加速器束流崩溃不稳定性数值模拟程序。描述了利用该程序开展的研究工作,这些研究揭示了束流崩溃不稳定性的一般规律,分析了相关参数对束流崩溃不稳定性的影响,最后提出了直线感应加速器束流崩溃不稳定性抑制方法。     

束流传输管道孔径变化引起的束团场能差

由直线加速器提供的用于自由电子激光(FEL)的电子束团,在其传输过程中常会遇到传输管道孔径变化的情况.本文在电荷密度均匀分布假定下,应用直线加速器中空间电荷束团的有限长柱模型,推导得到了束流传输管道孔径变化引起的束团场能变化及场能差公式.数值计算结果表明,它与国外以往所采用的以连续束流来代表直线加速器中电荷束团而得到的结果,有很大的差别,并且是更符合直线加速器中的电荷束团的实际情况,因而是更精确和可靠的.     

国产首台交变相位聚焦漂移管加速器的冷测与试运行

质子直线注入器是质子治癌系统的重要组成部分。出于项目进度的考虑,上海先进质子治癌示范装置APTRON采用了进口自美国的直线注入器。为了加快质子治癌产业进程,掌握质子放疗关键技术,保证产业链安全可控,注入器团队研发了国产医用质子直线注入器。该直线注入器采用了电子回旋共振（ECR）离子源和四翼型射频四极加速器（RFQ）的技术方案,并在漂移管加速器（DTL）段创新性地采用了交变相位聚焦（APF）结构。在这个过程中,通过研究APF DTL的束流运动规律和设计思想,自主开发了APF DTL的底层物理设计软件,相继完成了物理设计、电磁设计、机械设计、加工建造、腔体冷测、高频老练和载束实验等多个阶段的工作,最终成功引出了7 MeV、7 mA的质子束流。经过束诊系统的测量分析,认定束流中心能量为6.975 MeV,动量分散在±0.35%以内的束流流强为6.07 mA。成为国产首台医用质子直线注入器和首个实现成功载束的APF加速腔。     

ATPF—a dedicated proton therapy facility

A proton therapy facility based on a linac injector and a slow-cycling synchrotron is proposed. To obtain good treatments for different cancer types, both the spot scanning method and the double-scattering method are adopted in the facility, whereas the nozzles include both gantry and fixed beam types. The proton accelerator chain includes a synchrotron of 250 MeV in maximum energy, an injector of 7 MeV consisting of an RFQ and a DTL linac, with a repetition rate of 0.5 Hz. The slow extraction using the third-order resonance and together with the RFKO method is considered to be a good method to obtain a stable and more-or-less homogenous beam spill. To benefit the spot scanning 200 between 60 MeV and 230 MeV. A new method method, the extraction energy can be as many as about - the emittance balancing technique of using a solenoid or a quadrupole rotator is proposed to solve the problem of unequal emittance in the two transverse planes with a beam slowly extracted from a synchrotron. The facility has been designed to keep the potential to be upgraded to include the carbon therapy in the future.     

ATPF–a dedicated proton therapy facility

A proton therapy facility based on a linac injector and a slow-cycling synchrotron is proposed. To obtain good treatments for different cancer types, both the spot scanning method and the double-scattering method are adopted in the facility, whereas the nozzles include both gantry and fixed beam types. The proton accelerator chain includes a synchrotron of 250 MeV in maximum energy, an injector of 7 MeV consisting of an RFQ and a DTL linac, with a repetition rate of 0.5 Hz. The slow extraction using the third-order resonance and together with the RFKO method is considered to be a good method to obtain a stable and more-or-less homogenous beam spill. To benefit the spot scanning method, the extraction energy can be as many as about 200 between 60 MeV and 230 MeV. A new method – the emittance balancing technique of using a solenoid or a quadrupole rotator is proposed to solve the problem of unequal emittance in the two transverse planes with a beam slowly extracted from a synchrotron. The facility has been designed to keep the potential to be upgraded to include the carbon therapy in the future.     

Design of a 10 MeV normal conducting CW proton linac based on equidistant multi-gap CH cavities

Continuous wave(CW) high current proton linacs have wide applications as the front end of high power proton machines. The low energy part of such a linac is the most difficult and there is currently no widely accepted solution. Based on the analysis of the focusing properties of the CW low energy proton linac, a 10 Me V low energy normal conducting proton linac based on equidistant seven-gap Cross-bar H-type(CH) cavities is proposed. The linac is composed of ten 7-gap CH cavities and the transverse focusing is maintained by quadrupole doublets located between the cavities. The total length of the linac is less than 6 meters and the average acceleration gradient is about1.2 Me V/m. The electromagnetic properties of the cavities are investigated by Microwave Studio. At the nominal acceleration gradient the maximum surface electric field in the cavities is less than 1.3 times the Kilpatrick limit,and the Ohmic loss of each cavity is less than 35 k W. Multi-particle beam dynamics simulations are performed with Tracewin code, and the results show that the beam dynamics of the linac are quite stable, the linac has the capability to accelerate up to 30 m A beam with acceptable dynamics behavior.     

Design study for a 500 MeV proton synchrotron with CSNS linac as an injector

Using the China Spallation Neutron Source(CSNS) linac as the injector, a 500 MeV proton synchrotron is proposed for multidisciplinary applications, such as biology, material science and proton therapy. The synchrotron will deliver proton beam with energy from 80 MeV to 500 MeV. A compact lattice design has been worked out, and all the important beam dynamics issues have been investigated. The 80 MeV H-beam is stripped and injected into the synchrotron by using multi-turn injection. In order to continuously extraction the proton with small beam loss,an achromatic structure is proposed and a slow extraction method with RF knock-out is adopted and optimized.     

医用质子加速器注入器7 MeV漂移管直线加速器的设计

针对质子治癌直线加速器功耗少、长度短的要求,设计了一台工作频率为324 MHz的漂移管型质子直线加速器(DTL)。该DTL把粒子从2.5 MeV加速到7 MeV,功耗为265 kW, 总长1.9 m。横向聚焦采用FODO结构,漂移管内放置永磁铁。提出一种新的束流匹配方案,在射频四极场加速器(RFQ)与DTL之间不设束运线,而是以 DTL入口处的4个单元为匹配段,把RFQ出口处相椭圆匹配到DTL周期结构入口处的相椭圆。 用PARMILA程序对该DTL进行了动力学模拟,结果表明该方案的束流发射度增长很小。     

医用质子加速器注入器7MeV漂移管直线加速器的设计

 针对质子治癌直线加速器功耗少、长度短的要求,设计了一台工作频率为324 MHz的漂移管型质子直线加速器(DTL)。该DTL把粒子从2.5 MeV加速到7 MeV,功耗为265 kW, 总长1.9 m。横向聚焦采用FODO结构,漂移管内放置永磁铁。提出一种新的束流匹配方案,在射频四极场加速器(RFQ)与DTL之间不设束运线,而是以 DTL入口处的4个单元为匹配段,把RFQ出口处相椭圆匹配到DTL周期结构入口处的相椭圆。 用PARMILA程序对该DTL进行了动力学模拟,结果表明该方案的束流发射度增长很小。     

Initial Part of a Compact Proton Linac for Applied Purposes

Physics of Particles and Nuclei Letters - The initial part (IP) of a compact pulsed proton linac with an output energy of ?230 MeV is intended for the formation and acceleration of a beam...     

Mismatch study of C-ADS main linac

The ADS accelerator in China is a Continuous-Wave(CW) proton linac with 1.5 Ge V beam energy,10 m A beam current, and 15 MW beam power. To meet the extremely low beam loss rate and high reliability requirements, it is very important to study the beam halo caused by beam mismatch, which is one major sources of beam loss. To avoid envelope instability, the phase advances per period are all smaller than 90 degrees in the main linac design. In this paper, simulation results of the emittance growth and the envelope oscillations caused by mismatch in the main linac section are presented. To meet the emittance growth requirement, the transverse and longitudinal mismatch factors should be smaller than 0.4 and 0.3, respectively.