Pulsed-Power Hydrodynamics: An Application of Pulsed-Power and High Magnetic Fields to the Exploration of Material Properties and Problems in Experimental Hydrodynamics

Pulsed-power hydrodynamics (PPH) is an evolving application of low-impedance pulsed-power technology. PPH is particularly useful for the study of problems in advanced hydrodynamics, instabilities, turbulence, and material properties. PPH techniques provide a precisely characterized controllable environment at the currently achievable extremes of pressure and material velocity. The Atlas facility, which is designed and built by Los Alamos National Laboratory, is the world's first, and only, laboratory pulsed-power system designed specifically for this relatively new family of pulsed-power applications. Atlas joins a family of low-impedance high-current drivers around the world, which is advancing the field of PPH. The high-precision cylindrical magnetically imploded liner is the tool most frequently used to convert electromagnetic energy into the hydrodynamic (particle kinetic) energy needed to drive strong shocks, quasi-isentropic compression, or large-volume adiabatic compression for the experiments. At typical parameters, a 30-g 1-mm-thick liner with an initial radius of 5 cm and a moderate current of 20 MA can be accelerated to 7.5 km/s, producing megabar shocks in medium density targets. Velocities of up to 20 km/s and pressures of > 20 Mbar in high-density targets are possible. The first Atlas liner implosion experiments were conducted in Los Alamos in September 2001. Sixteen experiments were conducted in the first year of operation before Atlas was disassembled, moved to the Nevada Test Site (NTS), and recommissioned in 2005. The experimental program resumed at the NTS in July 2005. The first Atlas experiments at the NTS included two implosion dynamics experiments, two experiments exploring damage and material failure, a new advanced hydrodynamics series aimed at studying the behavior of particles of damaged material ejected from a free surface into a gas, and a series exploring friction at sliding interfaces under conditions of high normal pressure and high relative velocities. Longer term applications of PPH and the Atlas system include the study of material interfaces subjected to multimegagauss magnetic fields, material strength at high strain rate, the properties of strongly coupled plasmas, and the equation of state of materials at pressures approaching 10 Mbar.

I. Introduction

Pulsed-power hydrodynamics (PPH) is an application of pulsed-power technology that has emerged recently from the steadily advancing worldwide capability in high-performance drivers. Important advancements in the technology include not only increasing power and energy but also improved reliability, reproducibility, and economy. The evolution of PPH has been shaped by need for high-precision experimental data to validate sophisticated numerical models used in modern computer simulations and to motivate and guide improvements in the physics in those models. Improved models are important for improving confidence in the results of the computer simulations that are, increasingly, replacing field testing in many disciplines. The development of the discipline of PPH has been aided by the availability of a variety of working platforms, including both laboratory and field test systems developed over the last 50 years. The discipline of PPH has, in less than a decade, made numerous contributions in the fields of material properties and advanced hydrodynamics.