PW级脉冲驱动器的整体径向传输线的研究

Investigation on Monolithic Radial Transmission Line Used in Petawatt-class Pulsed Power Drivers

PW级脉冲功率驱动器中通常需要使用整体径向传输线(MRTL),以便将能量汇聚到负载上。为了了解MRTL的脉冲功率传输特性,基于多段均匀传输线级联模型,推导出了非均匀传输线输出电压的解析表达式。并从数学上证明了非均匀传输线的一些重要传输特性(首达波特性、脉冲压缩特性、高通特性)。利用CST微波计算软件包,对MRTL进行了3维电磁场模拟。结果表明:和电路模拟结果类似,指数线的最大功率传输效率高于Gaussian线和双曲线。但是,所有电磁场模拟得到的最大功率传输效率均比电路模拟大约低15%,这表明存在可观的非TEM模电磁场分量,因而基于TEM假设得到的电路模拟结果存在相当的误差。考虑到采用平板电极以便将几个MRTL叠在一起的要求,重点比较了双曲线和开孔指数线。虽然双曲线传输效率略低于指数线,但双曲线不需要开孔而易于加工,显然是最佳的选择。

Monolithic radial transmission lines （MRTLs） are used to combine the outputs from several-hundred tera- watt-level pulse generators to produce petawatt-level pulses. Based on a model of cascaded multiple section lines, a mathematical expression of the output voltage from a nonuniform line was deduced. The transmission characteristics of a nonuniform line, such as the first arriving wave, high-pass and pulse-compression, were clarified by the theoretical analy- sis of the mathematical expressions. Meanwhile, the 3τD electromagnetic simulation of MRTLs for future Z-pinch was performed. The results show that the power efficiency of exponential line is higher than that of Gaussian lines and hyper- bolic line, which is similar to that from the circuit simulation. However, all the power efficiencies are about 15% lower than those obtained with the circuit simulation, indicating the existence of considerable non-TEM modes and a non-ignorable error in the circuit simulation based on the quasi-TEM mode approximation. In consideration of several monolithic radial transmission lines being stacked together and the flat electrodes required by the stacked lines, the hyperbolic line was compared with the exponential line with several wide radial slots cut on the fiat electrodes. While the hyperbolic line has a slightly lower transmitted power efficiency than that of the exponential line, it is much easier in fabrication. Therefore, the hyperbolic line is recommended as the best choice.