Pulsed Power Hydrodynamics: A Discipline Offering High Precision Data for Motivating and Validating Physics Models

The discipline of pulsed power hydrodynamics is a new application of low-impedance, pulsed power technology, developed to study implosion hydrodynamics, instabilities, turbulence, and material properties in a highly precise, controllable environment at the extremes of pressure and material velocity. The discipline of pulsed power hydrodynamics arose in response to the need for economical, high-precision data to validate sophisticated numerical models used in current numerical simulations and to motivate the development of new models for future simulations. The international capability in pulsed power technology that has evolved over several decades in response to numerous other programmatic needs played a pivotal role in the development of the new discipline by enabling demonstrations of the techniques and production of introductory data long before a dedicated facility could be conceived, planned, and built. The high-precision, cylindrically imploding 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-gr, 1-mm- thick liner with an initial radius of 5 cm, driven by a current of 20 MA, can be accelerated to 7.5 km/sec producing mega-bar shocks in medium density targets. Velocities up to 20 km/sec and pressures >20 Mbar in high density targets are possible. The Atlas facility, designed and built by Los Alamos, houses the world's first laboratory pulsed power system designed specifically to explore this relatively new family of pulsed power applications. Constructed in the year 2000 and commissioned in August 2001, Atlas is a 24-MJ, high-performance capacitor bank delivering currents up to 30 Megamperes with a rise time of 5 to 6 musec. The first Atlas liner implosion experiments were conducted in September 2001, and 16 experiments were conducted in the first year of operation before Atlas was disassembled to be moved to the Nevada Test Site, where experiments began again in July 2005. Applications of pulsed power hydrodynamics techniques currently include material property topics such as: exploration of material strength at high rates of strain; material failure including fracture, damage, and spall; and interfacial dynamics at high relative velocities and high interfacial pressures. Implosion dynamics and a variety of complex hydrodynamic geometries have been explored and experiments to explore perturbation growth and transition to turbulence are under consideration. Longer term applications include the study of the behavior and properties of strongly coupled plasmas and the equation of state of metals and non-metals at pressures above 10 Mbar. This paper will provide an overview of the programmatic evolution that led to the birth of the discipline of pulsed power hydrodynamics.

I. INTRODUCTION

Pulsed Power Hydrodynamics (PPH) is among the newest applications of pulsed power to emerge from the steadily advancing development of electromagnetic capability and techniques that include increasing power and energy, but also improved reliability, reproducibility, and economy. The evolution of pulsed power hydrodynamics has been shaped by the need for high precision experimental data to validate sophisticated physics models used in modern computer simulations and to improve the physics in those models. The development of the discipline has been aided by the availability of a variety of working platforms, world-wide, in the form of both laboratory and field test systems developed over the last 50 years. And the discipline has, in less than a decade, made numerous contributions motivating the development of new physics models and validating existing ones in order to increase confidence in the results of the computer simulations that are increasingly replacing field testing in many disciplines.