3D Magneto-Hydrodynamic Modeling of an Overstressed Helical Magnetic Flux Compression Generator

Lawrence Livermore National Laboratory (LLNL) is actively engaged in an experimental program using two-stage magnetic flux compression generators (MFCGs) as pulsed power sources for equation of state measurements [1], [2]. These MFCGs amplify a current pulse in two stages. The first stage uses a helical MFCG and the second stage uses a coaxial MFCG. In support of this program, LLNL recently conducted an overstress test of a megajoule class helical flux compression generator [3]. This experiment was designed to test the generator at both higher currents and operating voltage than previous tests. One of the goals of this experiment was to benchmark the suite of computational tools used to predict the performance of these devices. This paper will focus on analysis of this experiment using the LLNL developed magneto-hydrodynamic (MHD) code ALE3D [7], [8]. For this particular experiment, the MHD analysis demonstrated excellent agreement with experimental data. This approach may be particularly useful for predicting non-linear losses in high-stress regimes.

I. Introduction

LLNL has conducted a number of experiments with the “Mini-G” or “MG” MFCG system since 2010 [1]. This system consists of a helical first stage and a coaxial second stage that were designed to provide upwards of 60 MA to an inductive load [1]. A cutaway 3D model of the two stage MG system is shown in Figure 1. This two-stage generator has been tested extensively over the last decade and has been found to be reliable for its nominal designed operating conditions.