直线感应加速器中四极磁铁聚焦强流电子束研究  

Study on Focusing High Current Electron Beams with Quadrupole Magnets in LIA

作　　者：荆晓兵[1] 王毅[1] 杨治勇[1] 石金水[1] JING Xiaobing;WANG Yi;YANG Zhiyong;SHI Jinshui(Key Laboratory of Pulse Power Science and Technology,Institute of Fluid Physics,China Academy of Engineering Physics,Mianyang 621900,China)

机构地区：[1]中国工程物理研究院、流体物理研究所脉冲功率科学与技术重点实验室,四川绵阳621900

出　　处：《原子能科学技术》2023年第12期2435-2442,共8页Atomic Energy Science and Technology

摘　　要：为获取小尺寸束斑,研究了直线感应加速器(LIA)产生的强流电子束在四极磁铁作用下的聚焦特性,并对限制最小束斑尺寸的因素进行了分析。结果表明,使用聚焦能力强、像差小的四极磁铁作为聚焦元件具有获取小尺寸束斑的潜力。使用数值模拟程序完成了四极磁铁聚焦束线的初步设计,并在直线感应加速器平台上开展了实验研究,获得了对称性较好、横向尺寸小于2 mm的X射线焦斑,验证了四极磁铁聚焦强流电子束获取小尺寸束斑的可行性。同时,提出了优化的四极磁铁聚焦束线设计方案,预期可在同样入射电子束条件下获得横向尺寸约1 mm的束斑。Aimed to obtain small-sized beam spots,the focusing characteristics of high current electron beams generated by linear induction accelerators(LIA)with the quadrupole magnets were studied in this paper.The main factors which influence the minimum beam spot size of high current electron beams were analyzed.The high-order magnetic field components and nonlinear effects between a quadrupole magnet and a solenoid coil were compared,and the expressions for the minimum beam spot radius when focusing with quadrupole magnets were derived.Based on this,it is pointed out that under the same incident electron beam parameters,it is a potential to use a quadrupole magnet with stronger focusing ability and smaller aberration as a focusing element in order to achieve better focusing of high current electron beams and obtain smaller beam spot sizes.Then the key designing points for the focusing beam line of a quadrupole magnet were proposed.The quadrupole magnet focusing beam lines were simulated with Trace-3D and BEAMPATH,and two types of focusing beam line designs and the expected minimum beam spot sizes were given.The first type is based on the existing quadrupole magnets while the second type is an optimized layout of stronger focusing quadrupole magnets.It can be seen from the numerical simulation results that the influence of electron beam energy divergence and emittance is smaller when the focused beam line is designed with a stronger focusing magnetic field,smaller beam transmission envelope and shorter focal length.An experimental study using the first type design was conducted on a linear induction accelerator to obtain small X-ray spots with an existing quadrupole magnet.The parameters such as electron beam energy and current intensity were measured for each shot,and the beam spot distribution at the bremsstrahlung target surface was equivalently obtained by measuring the X-ray spot distribution using a pin-hole imaging setup.In the experiment,when a focal length at the end is 245 mm the X-ray focal spots with good sym

关 键 词：直线感应加速器 强流电子束 四极磁铁 聚焦 

分 类 号：TL53[核科学技术—核技术及应用]