Particle simulation studies of low impedance nested double-ring electron beam diodes
-
摘要: 低阻抗嵌套型双环电子束二极管是一种自磁绝缘二极管。本文采用全电磁粒子模拟程序对低阻抗嵌套型双环二极管中电子束的产生和传输特性进行了较为细致的数值模拟，重点考查了电压脉冲上升过程中电子束传输特性的演化情况，并对二极管的物理特性和运行规律进行了物理分析和总结。通过数值模拟，给出了二极管中电场和角向自磁场空间分布、电子在实空间和相空间的分布、阳极靶面电子数能谱、电子落点和入射角分布等典型物理图像；给出了结构参数固定的情况下二极管电压波形和纵向间距的变化对二极管阻抗、电流以及电子束运行轨迹等的影响规律，加深了对二极管工作过程和物理特性的理解，同时可为后续利用蒙特卡罗（MC）程序计算电子轫致辐射产生的X射线剂量和辐射场的空间分布等提供电子源输入参数。当二极管电压峰值为1.5 MV时，模拟得到了到靶电流强度约为2.47 MA，阻抗约为0.6 Ω的电子束，二极管中自磁场的最大强度达到了1.7 T。Abstract:
Background As a high-energy radiation source, X-ray sources have been widely used in many research areas, such as radiation detection, radiation effects and surface thermodynamic effects. Bremsstrahlung diodes can produce X-ray sources with adjustable energy spectrum and pulse width.Purpose In order to improve the quality of X-ray source, the physical process of electron beam generation and transmission to target in Bremsstrahlung diode needs to be studied deeply.Methods In this paper, the generation and transmission characteristics of the electron beam in a bremsstrahlung diode which is called the low impedance nested double-ring diode are numerically simulated using the all electromagnetic PIC(Particle-in-Cell) code. Evolution of the electron beam propagation characteristics during the voltage pulse rise process is investigated emphatically, and the physical characteristics and operation principles of the diode are analyzed and summarized.Results When the peak diode voltage is 1.5 MV, simulation results showed that the total beam current obtained on the target is about 2.47 MA, the impedance is 0.6 Ω and the maximum intensity of the self-magnetic field in the diode reaches 1.7 T. The typical physical images such as the spatial distribution of electric field and angular self-magnetic field in the diode, the distribution of electrons in real space and phase space, the distribution of electron numbers versus the electron energy, the radial position, and impact angles on the anode target surface are given by simulations. The influence of diode voltage waveform and end axial gap length on diode impedance, current and electron beam trajectory are also obtained by simulations when the other structural parameters are fixed.Conclusions The simulation results will be used as the input parameters for subsequent calculation of X-ray dose and spatial distribution generated by electron bremsstrahlung using the Monte Carlo (MC) code.-
Key words:
- double-ring diode /
- diode impedance /
- magnetic insulation /
- particle simulation
-
图 1 低阻抗嵌套型双环电子束二极管的基本结构，rz截面
Figure 1. Schematic drawings of the nested double-ring electron beam diode, rz cross section
图 3 打在阳极2侧壁的电子电流随时间变化图，图上方1、2、3和4标注了4个不同的时间段
Figure 3. Time plot of the beam current on the side wall of anode 2.And 4 different time periods 1, 2, 3 and 4 are marked at top
图 4 对应图3中1、2、3和4时间段中某一时刻的电子实空间相位图
Figure 4. The real space plots of electrons at given times during the time periods 1, 2, 3, and 4 marked in Fig.3
图 5 靶面电流强度随时间的变化曲线
Figure 5. Time plots of the beam current on the anode target surface
图 7 电压达到稳定时二极管中电场的等高图，t=80.166 ns
Figure 7. Contour plots of electric field in the diode at t=80.166 ns
图 8 二极管中不同位置角向自绝缘磁场随时间的变化曲线
Figure 8. Time plots of the angular self-insulating magnetic field at different positions in the double-ring diode
图 9 电压达到稳定时二极管中角向自绝缘磁场等高图，t=80.166 ns
Figure 9. The contour plot of the angular self-insulating magnetic field in the double-ring diode when the voltage reaches stable, t=80.166 ns
图 10 不同时刻外环阴极发射的电子束轨迹图
Figure 10. Trajectories of electron beams emitted from the outer ring cathode at different times
图 11 不同时刻靶面电子数随能量和位置变化的等高图
Figure 11. Contour plot of electron number on target as a function of the energy and position at different times
图 12 电压达到稳定后某一时段阳极靶面电子数能谱、电子落点和入射角分布图，Δt≈0.5 ns，t0 = 80.166 ns
Figure 12. The electron number energy spectrum, electron impact point and incident angle distribution on the target surface at a certain period of time when the voltage reaches stable, Δt≈0.5 ns，t0 = 80.166 ns
图 13 稳定时二极管阻抗和电流随二极管峰值电压的变化曲线，纵向间距为6 mm
Figure 13. Time plots of the diode impedance and current as a function of the diode peak voltage at stable state with the axial gap length of 6 mm
图 14 不同二极管峰值电压下，打在阳极2侧壁的电子电流随时间变化图，曲线1、2和3分别代表峰值电压为1.0 MV，1.5 MV和2.0 MV，纵向间距为6 mm
Figure 14. Time plots of the electron current on the side wall of anode 2 under different peak diode voltages with the axial gap length of 6mm, curves 1, 2 and 3 stands for 1.0 MV, 1.5 MV and 2.0 MV respectively
图 15 稳定时二极管阻抗和电流随二极管纵向间距的变化曲线，峰值电压为1.5 MV
Figure 15. Variation of the diode impedance and current as a function of the axial gap length at stable state,the peak voltage is 1.5 MV
-
[1] Ware K D, Gullickson R L, Pierre J M, et al. Development of affordable technologies for large X-ray simulators[J]. IEEE Transactions on Plasma Science, 2000, 28(5): 1397-1404. doi: 10.1109/27.901205 [2] Maenchen J, Cooperstein G, O’Malley J, et al. Advances in pulsed power-driven radiography systems[J]. Proceedings of the IEEE, 2004, 92(7): 1021-1042. doi: 10.1109/JPROC.2004.829056 [3] 邱爱慈. 脉冲X射线模拟源技术的发展[J]. 中国工程科学, 2000, 2(9): 24-28Qiu Aici. The development of technology for pulsed X-ray simulators[J]. Engineering Science, 2000, 2(9): 24-28 [4] Swanekamp S B, Commisso R J, Cooperstein G, et al. Particle-in-cell simulations of high-power cylindrical electron beam diodes[J]. Physics of Plasmas, 2000, 7(12): 5214-5222. [5] 黄种亮, 邱孟通, 徐启福, 等. 轫致辐射反射三极管辐射场模拟[C]//中国核科学技术进展报告(第五卷)——中国核学会2017年学术年会论文集第7册(计算物理分卷、核物理分卷、粒子加速器分卷、核聚变与等离子体物理分卷、脉冲功率技术及其应用分卷、核工程力学分卷). 2017: 6-10Huang Zhongliang, Qiu Mengtong, Xu Qifu, et al. Numerical study on radiation field of bremsstrahlung reflex triode[C]//Progress Report on China Nuclear Science & Technology (Vol. 5). 2017: 6-10 [6] 钟甜城, 陈林, 郭帆, 等. 耦合同轴磁绝缘传输线的低阻抗大面积轫致辐射二极管设计[J]. 强激光与粒子束, 2017, 29: 065002Zhong Tiancheng, Chen Lin, Guo Fan, et al. Initial design of a low-impendence large-area-bremsstrahlung diode coupled with coaxial MITL[J]. High Power Laser and Particle Beams, 2017, 29: 065002 [7] Iwan D C. Computer simulation of the ring diode for Saturn[J]. Sandia report, 1986, SAND–85-2585. [8] 丁柏文, 郝建红, 张芳, 等. 大面积均匀轫致辐射场模拟及其源设计[J]. 强激光与粒子束, 2024, 36: 124003Ding Baiwen, Hao Jianhong, Zhang Fang, et al. Simulation and source design of large area uniform bremsstrahlung field[J]. High Power Laser and Particle Beams, 2024, 36: 124003 [9] 胡杨, 孙江, 张金海, 等. “强光一号”加速器短γ二极管径向箍缩率计算方法[J]. 物理学报, 2021, 70: 185202 doi: 10.7498/aps.70.20210472Hu Yang, Sun Jiang, Zhang Jinhai, et al. Methods of calculating radial collapse velocity of short-γ diode field on Qiangguang-I accelerator[J]. Acta Physica Sinica, 2021, 70: 185202 doi: 10.7498/aps.70.20210472 [10] 胡杨, 孙江, 张金海, 等. “晨光号”加速器二极管辐照面积和寿命提升技术[J]. 原子能科学技术, 2022, 56(7): 1448-1455Hu Yang, Sun Jiang, Zhang Jinhai, et al. Improvement of radiation area and lifetime of “Chenguang” accelerator diode[J]. Atomic Energy Science and Technology, 2022, 56(7): 1448-1455 [11] 李进玺, 吴伟, 来定国, 等. 强流二极管产生大面积脉冲X射线参数计算[J]. 强激光与粒子束, 2014, 26: 035005 doi: 10.3788/HPLPB20142603.35005Li Jinxi, Wu Wei, Lai Dingguo, et al. Calculation of pulse X-ray spectrum field generated by intense diode[J]. High Power Laser and Particle Beams, 2014, 26: 035005 doi: 10.3788/HPLPB20142603.35005 [12] 黄种亮, 徐启福, 来定国, 等. 低阻抗大面积二极管的研制[J]. 强激光与粒子束, 2016, 28: 014005Huang Zhongliang, Xu Qifu, Lai Dingguo, et al. A low impedance large surface diode[J]. High Power Laser and Particle Beams, 2016, 28: 014005 [13] 屈俊夫, 冯元伟, 耿力东, 等. 0.45~4 MV杆箍缩二极管阳极等离子体研究[J]. 原子能科学技术, 2023, 57(3): 655-665Qu Junfu, Feng Yuanwei, Geng Lidong, et al. Study on plasma emission from anode rod of 0.45-4 MV rod-pinch diode[J]. Atomic Energy Science and Technology, 2023, 57(3): 655-665 [14] Foster J C, McClory J W, Swanekamp S B, et al. Particle-in-cell simulations of ion beam properties produced from a planar pinched-beam diode[J]. IEEE Transactions on Plasma Science, 2023, 51(1): 90-103. doi: 10.1109/TPS.2022.3229285 [15] Ottinger P F, Schumer J W. Rescaling of equilibrium magnetically insulated flow theory based on results from particle-in-cell simulations[J]. Physics of Plasmas, 2006, 13: 063109. doi: 10.1063/1.2212831 -
下载:
点击查看大图
计量
- 文章访问数: 27
- HTML全文浏览量: 14
- PDF下载量: 2
- 被引次数: 0
