Experimental research on the transmission characteristic of monolithic radial transmission lines

Abstract

An experiment system of a scaled-down monolithic radial transmission line (MRTL) for future Z-pinch drivers was established to testify the validity of 3-D electromagnetic (EM) simulation. The MRTL had a hyperbolic impedance profile. Being immersed in deionized water, the MRTL was composed of two flat aluminum plates separated by a distance of 1 cm. The radius of both plates was 0.5 m, which corresponds to a one-way transit time of about 15 ns for the EM wave from the outer circumference to the center. As this was a linear system, the experiment could be performed at a low voltage. A high voltage pulse was divided into 21 low voltage pulses by a 1-way to 21-way convertor. 20 of the 21 pulses were fed into the MRTL by BNC connectors while the other one was connected to an oscilloscope. The input BNC connectors were uniformly distributed around and connected to the outer circumference of the MRTL. All input voltage pulses were same with each other, with a waveform of rectangle, about 2 ns in rise time, 10 ns in full width at half maximum (FWHM) and 30 V in amplitude. 20 paralleled resisters, each of which was 154 Ω in resistance, were put around the center to match the output impedance of the MRTL. The waveform of the output voltage on the load was measured and compared to the result from 3-D EM simulation of the same hyperbolic line. The two waveforms nearly superimposed onto each other, which validated the correctness of both the experimental method and 3-D EM simulation method.