Review of the NRL Liner Implosion Program

Abstract

For the past several years, the Naval Research Laboratory has been investigating the use of imploding liner magnetic flux compression techniques to achieve high energy densities. Of particular interest has been the possibility of utilizing liner implosions to compress plasma adiabatically to thermonuclear fusion temperatures. Initial concepts followed the work at IAE Kurchatov and involved the electromagnetic implosion of copper and aluminum cylinders in the manner of a theta pinch. Experiments at NRL achieved radial compressions of 28:1 and fields of 1.4 MG using 30 cm initial-diam aluminum liners driven by an inductively-powered, single-turn solenoid. To avoid irreversible solid-mechanical behavior (buckling, shrapnel, etc.) experiments were later performed with rotationally stabilized, liquid sodium-potassium liners, again imploded electromagnetically. To stabilize the liquid liner motion completely, a new implosion technique, utilizing free pistons driven by high pressure gas, has been developed. Radial compressions of 30:1 and repetitive implosion-reexpansion cycles have been obtained with this technique. Stabilized-liner implosion systems have been constructed at NRL which allow a matrix of hydrodynamic and high magnetic field phenomena to be investigated. Smaller devices (“water models”) are used to study basic dynamical behavior of incompressible fluid liners. Two other devices, LINUS-O and HELIUS, with initial bores of 30 cm and 15 cm, respectively, can be used to study compressible liner dynamics and magnetic diffusion.