回旋加速器主磁铁非理想磁场垫补方法研究  

Research on Non-ideal Magnetic Field Shimming Method of Cyclotron Main Magnet

作　　者：陆锦荣 安世忠[1] 边天剑 陈忻禹 王飞[1] 杨光[1] 凌丽 魏素敏[1] LU Jinrong;AN Shizhong;BIAN Tianjian;CHEN Xinyu;WANG Fei;YANG Guang;LING Li;WEI Sumin(Department of Nuclear Technology and Application,China Institute of Atomic Energy,Beijing 102413,China)

机构地区：[1]中国原子能科学研究院核技术综合研究所,北京102413

出　　处：《原子能科学技术》2024年第5期1127-1136,共10页Atomic Energy Science and Technology

基　　金：国家重点研发计划(2016YFC0105302);国家自然科学基金(12375156,12105370);中核集团“青年英才”项目(FY212406000404)。

摘　　要：回旋加速器主磁场的精密测量和误差垫补技术是回旋加速器技术研究的一个重要方向,也是设备建造的关键环节之一。由于受铁材料内部缺陷、机械加工误差等因素的影响,回旋加速器主磁铁所产生非理想磁场通常会偏离所需要的等时性磁场分布,且含有一定幅值的谐波磁场。因此,在研制回旋加速器的过程中需对非理想磁场进行多次垫补,通过修正实际磁场的分布而最终达到使用要求。与传统磁场垫补算法相比,本文提出了一种基于多元线性回归模型的垫补算法,加入对一次谐波磁场的计算,实现对磁场等时性误差与一次谐波误差同时进行定量化垫补,省去了单独针对一次谐波磁场的垫补过程。为避免增加有限元计算量,本文在新算法中使用了基于1/4磁铁模型获取平均磁场、一次谐波磁场的垫补形状函数。最后使用本文所提垫补方法,将中国原子能科学研究院16 MeV回旋加速器主磁场的等时性误差降低至10-4量级、一次谐波磁场降低至6 Gs以内。实验结果表明,本文提出的算法具有形状函数计算量小、垫补精度高、迭代次数少的特点。The precise measurement and error compensation technique of the main magnetic field in cyclotron accelerator are important research directions and key components in the construction of the device.Due to factors such as internal defects in the iron material and mechanical processing errors,the non-ideal magnetic field generated by the main magnet of the cyclotron accelerator usually deviates from the required isochronous magnetic field distribution and contains a certain amplitude of harmonic magnetic field.Therefore,in the process of developing a cyclotron accelerator,it is necessary to perform multiple shimming on the non-ideal magnetic field,and ultimately achieve the required distribution by correcting the actual magnetic field.Compared with traditional magnetic field compensation algorithms,this paper proposes an algorithm based on a multivariate linear regression model,incorporating the calculation of the first harmonic magnetic field.This algorithm achieves simultaneous quantitative shimming for both temporal errors in the magnetic field and first harmonic errors,eliminating the need for a separate iterative process for shimming the first harmonic magnetic field.In order to avoid increasing the finite element calculation workload,this paper uses a 1/4 magnet model in the new algorithm to obtain the shape function for the first harmonic magnetic field and the average magnetic field.Simplifying the full model finite element calculation of the main magnet to a 1/4 model can save approximately 80%of CPU time.By using the algorithm proposed in this paper,after three iterations of shimming,the isochronism error of the magnetic field in the 16 MeV cyclotron at the China Institute of Atomic Energy is reduced to the order of 10-4,and the integral sliding phase control of particles is controlled within±14°,while the magnitude of the first harmonic of the magnetic field is reduced to within 6 Gs.The transverse free oscillation frequency of the magnetic field was also adjusted,improving the axial focusing frequency a

关 键 词：回旋加速器 等时性误差 一次谐波磁场 同时垫补 多元线性回归 

分 类 号：TL542[核科学技术—核技术及应用]