Explosive pulsed power experimental capability at LLNL

LLNL has developed a family of advanced magnetic flux compression generators (FCGs) used to perform high energy density physics experiments and material science studies. In recent years we have performed these experiments at explosive test sites in New Mexico and Nevada. In 2011, we re-established an explosive pulsed power test facility closer to Livermore. LLNL's Site 300 is a U.S. DOE-NNSA experimental test site situated on 7000 acres in rural foothills approximately 15 miles southeast of Livermore. It was established in 1955 as a non-nuclear explosives test facility to support LLNL's national security mission. On this site there are numerous facilities for fabricating, storing, assembling, and testing explosive devices. Site 300 is also home to some of DOE's premier facilities for hydrodynamic testing, with sophisticated diagnostics such as high-speed imaging, flash X-ray radiography, and other advanced diagnostics for performing unique experiments such as shock physics experiments, which examine how materials behave under high pressure and temperature. We have converted and upgraded one particular firing bunker at Site 300 (known as Bunker 851) to provide the necessary infrastructure to support high explosive pulsed power (HEPP) experiments. In doing so, we were able to incorporate our established practices for handling grounding, shielding, and isolation of auxiliary systems and diagnostics, in order to effectively manage the large voltages produced by FCGs, and minimize unwanted coupling to diagnostic data. This paper will discuss some of the key attributes of the Bunker 851 facility, including the specialized firesets and isolated initiation systems for multistage explosive systems, a detonator-switched seed bank that operates while isolated from earth and building ground, a fiber-optic based timing, triggering and control system, an EMI Faraday cage that completely encloses diagnostic sensors, cabling and high-resolution digitizers, optical fiber-based velocimetry and current sensor systems, and a flash X-ray radiography system. The photos and experimental results from recent FCG experiments will also be shown and discussed.

I. Introduction

A facility capable of firing HEPP experiments has several requirements that exceed the requirements of a conventional HE experimental facility. There are constraints on facility system design, due to the need to manage voltages and radiated electromagnetic energy produced during flux compression generator operation, and there are capabilities necessary to fire and diagnose the generator itself. A successful HEPP facility will provide the necessary capabilities, while incorporating design principles that manage the constraints.