Modeling Methods for the Main Switch of High Pulsed-Power Facilities Based on Transmission Line Code

Based on the transmission line code （TLCODE）, a circuit model is developed here for analyses of main switches in the high pulsed-power facilities. With the structure of the ZR main switch as an example, a circuit model topology of the switch is proposed, and in particular, calculation methods of the dynamic inductance and resistance of the switching arc are described. Moreover, a set of closed equations used for calculations of various node voltages are theoretically derived and numericMly discretized. Based on these discrete equations and the Matlab program, a simulation procedure is established for analyses of the ZR main switch. Voltages and currents at different key points are obtained, and comparisons are made with those of a PSpice L-C model. The comparison results show that these two models are perfectly in accord with each other with discrepancy less than 0.1%, which verifies the effectiveness of the TLCODE model to a certain extent.     

Numerical Simulation of Azimuthal Uniformity of Injection Currents in Single-Point-Feed Induction Voltage Adders

In order to investigate the injection current uniformity around the induction cell bores,two fully electromagnetic(EM) models are respectively established for a single-stage induction cell and an induction voltage adder(IVA) with three cells stacked in series,without considering electron emission.By means of these two models,some factors affecting the injection current uniformity are simulated and analyzed,such as the impedances of adders and loads,cell locations,and feed timing of parallel driving pulses.Simulation results indicate that higher impedances of adder and loads are slightly beneficial to improve injection current uniformity.As the impedances of adder and loads increase from 5 Ω to 30 Ω,the asymmetric coefficient of feed currents decreases from 10.3%to 6.6%.The current non-uniformity within the first cell is a little worse than that in other downstream cells.Simulation results also show that the feed timing would greatly affect current waveforms,and consequently cause some distortion in pulse fronts of cell output voltages.For a given driving pulse with duration time of 70-80 ns,the feed timing with a time deviation of less than 20 ns is acceptable for the three-cell IVAs,just causing the rise time of output voltages to increase about 5 ns at most and making the peak voltage decrease by 3.5%.     

感应电压叠加器次级非轴对称磁绝缘物理模型和数值分析

针对感应腔注入电流非均匀分布引起的感应电压叠加器次级非轴对称磁绝缘问题,在磁绝缘经典层流理论基础上,通过引入角向非均匀分布的模数,将经典一维轴对称磁绝缘Creedon理论推广至两维(r,θ)平面,建立了圆柱坐标系下二维层流物理模型,推导了磁绝缘电参数(电磁场、空间电子密度、电子鞘层等)与相对论因子γ(r,θ)的关系。当给定边界条件(阴极磁感应强度角向分布)时,数值求解物理模型,获得了感应电压叠加器次级非轴对称磁绝缘电参数的二维分布。当感应电压叠加器次级阴极磁感应强度满足余弦分布时,磁绝缘电子鞘层边界近似呈高斯分布。在靠近馈入点的角向位置,由于磁感应强度较大,电子鞘层较薄,磁绝缘电子密度较大。阳极磁感应强度分布均匀性优于阴极,且两者相位相差180°,数值分析结果与RITS-3装置实验结果基本相符。建立的物理模型和分析方法可用于长距离磁绝缘线内筒偏心等非轴对称磁绝缘问题。     

磁绝缘感应电压叠加器注入电流空间非均匀分布及影响因素分析

磁绝缘感应电压叠加器(MIVA)脉冲馈入方式导致感应腔注入电流空间非均匀分布,这对感应腔性能(如等效电感、电磁场分布、输出参数等)和MIVA次级磁绝缘特性(如电子鞘层、流阻抗、电流损失等)产生影响。建立MIVA感应腔全电磁模型,并得到典型结构下感应腔初级注入电流空间分布和次级磁场强度的分布特性。给出电流不均匀系数δ(t)的动态变化过程,仿真分析注入电流脉宽、感应腔初级绝缘介质、脉冲馈入路数及时间抖动等因素对δ(t)的影响规律。结果表明,δ(t)动态过程分为快速下降、稳定和缓慢下降三个阶段,注入电流脉宽影响稳定阶段持续时间和缓慢下降阶段;初级绝缘介质影响感应腔内电磁脉冲传播速率,进而对电流空间分布产生影响;注入脉冲路数对注入电流空间分布有决定性影响;双路脉冲馈入感应腔注入时间不同步时,不均匀系数发生改变。开展了单级感应腔注入电流空间分布实验,验证了电磁计算的正确性。     

Study on Performance Parameters of the Plasma Source for a Short-Conduction-Time Plasma Opening Switch

Plasma source performance parameters,including plasma ejection density and velocity,greatly affect the operation of a short-conduction-time plasma opening switch(POS).In this paper,the plasma source used in the POS of Qiangguang I generator is chosen as the study object.At first the POS working process is analyzed.The result shows that the opening performance of the POS can be improved by increasing the plasma ejection velocity and decreasing the plasma density.The influence of the cable plasma gun structure and number on the plasma ejection parameters is experimentally investigated with two charge collectors.Finally a semi-empirical model is proposed to describe the experimental phenomenon.     

Optimization of Cavity Combination for 20 MA LTD-Based Accelerators

Based on a transmission line code,a circuit model is proposed that could serve as the basic method for the analysis of linear transformer driver (LTD)-based accelerators.By using 1MA,100kV LTD cavities,the peak load current is optimized for a total of N cavities between 500 and 1200.The simulation results suggest that,with the same number of cavities,the peak current changes obviously with the types of combinations,and the maximum change can be as large as 1.2MA.The results also show that,for the cases considered,the optimized peak current as a function of the total number of cavities agrees with the exponential associate,and the peak current for one level LTD cannot be enhanced infinitely.Furthermore,it is found that,to obtain a 20MA peak load current,at least 1029 LTD cavities (49 in series and 21 in parallel connection) are needed.Finally,the typical parameters of the optimized design are compared to those of the existing Z accelerator.     

Dynamic Model for the Z Accelerator Vacuum Section Based on Transmission Line Code

The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al., is revised. The revised model uses diffe...     

Simulation Analysis of Transmission-Line Impedance Transformers for Petawatt-Class Pulsed Power Accelerators

Based on the transmission line code TLCODE, a 1D circuit model for a transmission- line impedance transformer was developed and the simulation results were comp...     

基于IBIS模型的多路脉冲信号源ADS仿真

使用高速比较器+两级时钟扇出buffer+比较器输出CMOS电平方案,利用ADS的Integrity–IBIS模块,搭建了80台示波器用脉冲信号源。介绍了IBIS模型原理、语法结构及模型适用性,并进行了瞬态仿真,分析了高速比较器IC、时钟扇出IC和脉冲输出IC之间的差分信号完整性,对最终输出信号的延迟和抖动进行了计算。仿真结果表明：使用高速比较器+两级时钟扇出buffer+比较器输出CMOS电平方案可获得80路同步触发信号;输入输出信号延迟<2.6ns,抖动<11ps,50Ω负载时输出信号幅值1.97V,前沿997ps,满足多路示波器外触发信号要求。