Status of the Z pulsed power driver

Abstract

The Z pulsed power driver at Sandia National Laboratories is used for a variety of high energy physics experiments. The Z system stores 20 megajoules at the present nominal ±85 kV Marx charge voltage. The Z system consists of 36 basically identical modules, each with a DC-charged Marx generator, water insulated intermediate store capacitor, laser triggered gas switch, and water insulated pulse-forming section. High current drivers such as Z are able to create energy densities of megajoules per cubic centimeter in ~1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volumes, used for creating extremes of temperature and pressure on a nanosecond time scale. The Z driver has delivered currents up to 27 MA with 85 nanosecond rise time (10%-90%) into fixed inductance and imploding plasma loads. Z has generated over 300 TW peak X-ray power, with more than 2 MJ total energy radiated from imploding tungsten plasma shells. Z is also used for studying dynamic compression of solid materials at megabar levels, using magnetic pressure from current densities of tens of megamperes per cm. Z is a confluence of pulsed energy storage and switching technologies. DC charged Marx generators are triggered with ten-nanosecond precision, transferring energy to water-insulated coaxial capacitors. Six megavolt laser triggered gas switches perform the final nanosecond time synchronization, and self-closing water switches further compress the pulse. Issues with the system include improving the reliability and performance of the components, and improving our conceptual understanding of the entire machine. Many of the Z components are unique: Z requires laser triggered gas switches operating at six million volts, water switches operating at three million volts, and large-area solid-vacuum interfaces operating reliably at 140 kV/cm. Synchronization with fast load diagnostics requires nanosecond predictability of the load current timing, while the pre-fire probability of any switch must be extremely small. We will describe the state of the machine, and specific measurements of subsystem performance.