Genesis: A 5-MA Programmable Pulsed-Power Driver for Isentropic Compression Experiments

Enabling technologies are being developed at Sandia National Laboratories to improve the performance and flexibility of compact pulsed-power drivers for magnetically driven dynamic materials properties research. We have designed a modular system that is capable of precision current pulse shaping through the selective triggering of pulse-forming components into a disk transmission line feeding a strip line load. The system is composed of 240 200-kV 60-kA modules in a low-inductance configuration that is capable of producing 250-350 kbar of magnetic pressure in a 1.75-nH 20-mm-wide strip line load. The system, called Genesis , measures approximately 5 m in diameter and is capable of producing shaped currents that are greater than 5 MA. This performance is enabled through the use of a serviceable solid-dielectric insulator system which minimizes the system inductance and reduces the stored energy and operating voltage requirements. Genesis can be programmed by the user to generate precision pulse shapes with rise times of 220-500 ns, allowing characterization of a range of materials from tungsten to polypropylene. This paper provides an overview of the Genesis design, including the use of genetic optimization to shape currents through selective module triggering.

I. Introduction

The USE OF pulsed-power systems to generate programmable output pulses has been researched for at least two decades. Initial work concentrated on electromagnetic launcher performance. Pulsewidths (FWHM) ranging from hundreds of microseconds to several milliseconds have been published [1]– [7]. More recently, submicrosecond pulse shaping has been introduced for material studies using isentropic compression experiments (ICEs). Magnetically driven isentropic compression in materials has generated a wealth of data on the properties of materials under dynamic shock loading [8]. This technique relies on current shaping to produce magnetic pressures that move the state of the materials along an isentrope while avoiding the formation of shock waves in the target material. The Z machine at Sandia National Laboratories (SNL) has demonstrated shaped current pulses for ICEs through the staged triggering of nine sets of pulse-forming lines [9]. On smaller platforms, SNL's Veloce pulser has demonstrated shaped current pulses up to 3 MA, with a rise time of 300 ns, using two independently controlled trigger points [10].