Current adder with programmable pulse shaping

Advancements in fusion research and Equation of State (EOS) experiments have led to a need for greater control over the shape of the current waveform in the load. This added complexity will necessitate more sophisticated pulsed power designs. Challenges introduced by these new systems include the requirement for more elaborate control systems to accommodate multiple independent switching times and an improved understanding of how dwell times and jitter affect performance. A subscale programmable current adder has been built to investigate the issues. This system has six independently programmable bricks and is capable of achieving peak currents greater than 2 kA. The bricks were characterized and modeled as a prerequisite to the application of genetic algorithms (GA’s) to determine the required initial conditions, switch triggering times and the brick charge voltages necessary to achieve commanded current shapes. This paper presents a description of the system control, circuit topology, solid-state triggering, charging systems, and system characterization. All of these system parameters are discussed within the context of commanded and measured output currents.

I. Introduction

Independently sequencing the triggering of the different switches in a Pulsed Power system can significantly increase the flexibility of the system but also entails design and operational complexity. Some existing systems are already being operated with programmable output currents. The Z-machine uses 36 laser triggered gas switches that are staggered in time to conduct EOS research, [1], and sequentially-fired pulse forming networks have been designed for railgun and electromagnetic launchers [2], [3].