中国原子能科学研究院目前正在研制用于硼中子俘获治疗(BNCT)的强流质子回旋加速器,该加速器设计引出能量14 MeV、质子束流强大于1 mA.相比引出流强为400μA的PET回旋加速器,BNCT强流质子回旋加速器对中心区相位接收度和轴向聚焦的要求更高.为实现mA量级的束流的加速和引出,BNCT强流质子回旋加速器采取了增加负氢束流注入能量、增大磁铁镶条孔径、使用用于增大D ee盒头部张角的阶梯状结构及调整加速间隙的入口和出口高度等一系列中心区结构优化设计,有效地提高了中心区的相位接收度,改善了轴向电聚焦.在新的离子源注入能量下通过数值计算得到实测场下的轴向电聚焦和间隙高度的关系,选取合适的间隙高度获得最佳的轴向聚焦,从而确定了mA量级束流的注入和加速的中心区结构.同时在设计中考虑空间电荷效应的影响,计算了不同流强下的束流尺寸变化.中心区结构在实测磁场下的优化设计计算结果表明,BNCT强流质子回旋加速器中心区的束流对中好于0.5 mm,相位接收度大于40°,中心区最高可接收流强3 mA.目前,新的中心区结构已进入机械加工阶段.

中国原子能科学研究院目前正在研制一台230 MeV超导回旋加速器,该回旋加速器未来是安装于医院应用于质子治疗,采用了非常紧凑型的超导磁体结构设计.其分子泵所安装位置有非常大的漏磁场,其漏磁场强度达到1000 Gs,是分子泵安全运行阈值(50 Gs)的20倍,导致分子泵不能正常工作.为了解决这个问题,首先进行了分子泵磁屏蔽体的结构设计,以及3D有限元仿真分析计算,然后开展对不同分子泵磁屏蔽体内的磁场进行详细测量,结果表明磁屏蔽体内部的剩磁场均小于50 Gs,且分子泵实际长时间运行过程中监测分子泵运行参数电流、轴承温度、转子温度、加速时间均与无磁场时运行参数一致.

A 230 MeV compact superconducting cyclotron CYCIAE-230 is being constructed by the China Institute of Atomic Energy, which can be used for proton therapy and space radiation physics research. The technology of magnetic field measurement, shimming and processing is the primary task to realize the isochronous acceleration of cyclotron. The CYCIAE-230 has high magnetic field, high field gradient and dense rotation orbits. Therefore, the isochronous field and tune diagram need to be amended simultaneously. The first harmonic is also shimmed at the same process to ensure a good extraction efficiency by using precessional extraction. The precision of field measurement, shimming and processing is much higher and the algorithm is much more difficult than those in normal temperature cyclotron. In addition, the compact structure of the magnet has very narrow installation space, which makes the design of the mapper more difficult. The process of main magnet construction includes strict control of room temperature and electromagnetic compatibility (EMC), precise measurement of magnetic field, comprehensive research of beam dynamics and multi-dimensional numerical control (NC) processing under the control of complex algorithms. In this paper, the magnetic field measurement, shimming and processing of the main magnet will be illustrated in detail.

At CIAE, we have been engaged in the development of isochronous accelerator for 60 years. From Cyclotron in the past to CW FFAG at present, isochronous accelerators have the technical advantages of high average beam intensity, fixed magnetic field and RF frequency, and low construction and operation costs. Therefore, the isochronous accelerator has been widely used. In this paper, a 100 MeV compact isochronous cyclotron CYCIAE-100 developed at CIAE in recent years is introduced. The successful commissioning of the cyclotron obtains a proton beam power up to 52 kW. Its stable operation provides dual-beam with the intensity ranges from 10 pA to 520 μA, and its applications are carried out annually for more than 30 users in different research fields. This paper also introduces a 2 GeV CW FFAG first proposed by CIAE. From the design of the 2 GeV CW machine, the energy limitation of the isochronous accelerator is increased from ∼1 GeV to 2 GeV, by our contribution of the beam dynamics study for high energy isochronous FFAG. The basic design of the key components, including HTS magnet, HP RF system, injection and extraction system, have also been explored. The preliminary conclusions suitable for engineering implementation are also presented.

Proton beam with an average power of 5 MW-10 MW have important applications in particle physics towards the intensity frontier, as well as in the advanced energy, and material science. The fixed field alternating gradient (FFAG) accelerator combines the advantages of existing accelerators, which has a higher limitation of beam energy than high power cyclotron and has a higher beam-to-grid efficiency than existing high power linac and synchrotron, thus is considered as a good candidate for high power proton machine. By utilizing the strong focusing and large acceptance features of FFAG in the theoretical framework of the fixed field and fixed frequency of isochronous cyclotron, a continue wave FFAG capable of producing 2 GeV/3 mA protons (with an beam power of 6 MW) has been proposed in China Institute of Atomic Energy (CIAE). Due to the beam loss of high power proton beams, the resulting high radiation will deposit a large amount of radiation dose and heat load on the superconducting (SC) magnet. As the high temperature superconductors (HTS) have a much larger thermal margin due to high critical temperature (> 90 K) and high upper critical field (>100 T) than the traditional low temperature superconductors, and have been also considered have the lower overall construction costs and power consumption than the conventional magnet, currently the HTS magnet is the favorable solution for the 2 GeV FFAG magnet design. In this paper, the lattice design along with the requirements on the F-D-F magnet of the 2 GeV FFAG design is briefly introduced first. Then, the design of the F-D-F magnet is outlined. The details of the HTS coil design utilizing ReBCO conductor and operating at ~30 K is also included.

In China, there is a strong demand of the medium-energy proton accelerators for proton therapy. A compact superconducting cyclotron named CYCIAE-230 is currently under construction at CIAE to provide 230 MeV proton beam. In this paper, the investigation and quantitative simulation of beam physics for CYCIAE-230 will be presented in detail, which mainly include: 1. The beam dynamics behavior in the ultra compact central region and the design challenges including the micro PIG ion source, the tips of magnetic poles and RF cavities; 2. the numerical simulation and optimization of the phase slip and tune diagram in acceleration region; 3. the orbit simulation in the extraction region, emphasizing on increasing the turn separation and the resonance study; 4. the fast intensity modulation, control of beam stabilization by a closed-loop feedback, and the basic algorithm for controlling the beam intensity, adjusting the phase and their implementations.

China Institute of Atomic Energy has developed a 230 MeV compact superconducting cyclotron CYCIAE-230 to meet the demands of proton therapy in China. Physical design requires a strict control of the average field error and first harmonic in the main field. A processing method of inclined 45° continuous cutting on the two pole sides is at the first time proposed to shim the field in compact superconducting cyclotron. For a spiral magnet pole, the field generated by the 45° continuous cutting on edges is relatively complicated to be calculated precisely by finite element method. In this paper, the analytical model of the linear equation for field shimming calculation is established. The shape function caused by the local cutting is solved by the magnetic saturation approximation. And then the shimming process is built with an iterative procedure based on the ridge regression method. The shimming algorithm is applied in CYCIAE-230, which achieve good results to reduce the shimming times and further the construction period. The process of the shimming algorithm and the corresponding shimming effect in CYCIAE-230 will be presented in detail.

经过60年的发展,中国原子能科学研究院(CIAE)独立自主地开展了基于PIC技术的强流回旋加速器束流动力学的大规模并行计算的核心算法研究,开发了CYCPIC2D、CYCPIC3D和OPAL-CYCL等强流回旋加速器束流动力学模拟程序,搭建了专用的高性能并行化计算机群PANDA.本文以CIAE已建成及在研的不同类型的回旋加速器为例,总结了回旋加速器基本束流动力学的分析方法和主要计算结果,并介绍了CIAE在回旋加速器束流动力学与多物理场模拟技术方面的发展与应用.

本文介绍了50 MeV负氢回旋加速器(CYCIAE-50)的总体设计考虑和主磁铁系统的优化设计过程及结果.确定了CYCIAE-50主磁铁的主要尺寸参数,建模计算出满足等时性的主磁铁中心平面磁场.通过调整参数,优化了主磁铁的峰值磁场 、局部饱和等,以控制建造及运行成本.优化了磁极张角与磁气隙高度等参数,使负氢离子满足轴向和径向的聚焦要求,避免穿越有害共振.最后对主磁铁的结构进行形变校核,并估计了形变对束流动力学的影响.设计结果表明,CYCIAE-50的主磁铁设计符合要求,可为后续其他系统的设计和建造提供重要参考.