Robert E. Reinovsky

Electromagnetic-implosion generation of pulsed high-energy-density plasma

The generation of pulsed high‐energy‐density plasmas by electromagnetic implosion of cylindrical foils (i.e., imploding liners or hollow Z pinches) has been investigated experimentally and theoretically at the Air Force Weapons Laboratory. The experimental studies involve discharging a 1.3‐μsec 1.1‐MJ capacitor bank through 7‐cm‐radius 2‐cm‐tall 3–30‐mg cylindrical foil liners. Typical discharge parameters are 7–12‐MA peak current and 1–1.5‐μsec current rise time. Current and voltage waveforms indicate strong coupling of the load to the capacitor bank, and analysis of the waveforms indicates good implosion of the current sheath. Optical‐ and magnetic‐probe measurements are consistent with 1–2‐cm thickness of the imploding plasma shell and with final implosion velocities ∼15–20 cm/sec. Radiation‐diagnostic measurements indicate ultrasoft x‐ray yields ∼50–100 kJ with the FWHM of the photon pulse ∼80–100 nsec. The radiation data is consistent with a quasiblackbody spectrum (T∼30–50 eV) comprising most of the...

Crenulation-­1 Flash Report

We briefly report on the first of PHELIX driven Crenulation experiments diagnosed with proton radiography. PHELIX is a 300 kJ capacitor bank located at the LANL LANSCE pRad facility. It is capable of delivering a 4 MA, 10 us current pulse to a low inductance cylindrical load. Using a magnetically driven cylindrical liner, we have shocked a concentric tin cylindrical shell to melt-on-release and compared to theory and calculations. The inner surface of the tin cylinder has three sectors of single-mode perturbations, which are subject to Richtmyer-Meshkov Instability (RMI). Recent theoretical work on the EOS of tin has modified both the Hugoniot and the isentropes for release into various states in tabular data. The new multiphase EOS for tin, SESAME 2161, includes the beta and gamma solid phases as well as a liquid phase. It predicts a lower pressure boundary for release to pure solid (~20 GPa) and a higher pressure boundary for release to pure liquid (~35 GPa) than the existing SESAME 2160 table.

Cren(ulation)-­1,2 Preshot Report

There is great interest in the behavior of the free surface of tin under shock loading. While it is known that meso-scale surface imperfections can seed the RichtmyerMeshkov Instability (RMI) for a surface that is melted on release, much less is known about a tin surface that is solid, but plastically deforming. Here material properties such as shear and yield strength come into play especially in converging geometry. Previous experiments have been driven by direct contact HE. Usually a thin, flat target coupon is fielded with various single-mode, sinusoidal, machined, profiles on the free surface. The free surface is adjacent to either vacuum or an inert receiver gas. Most of these previous driver/target configurations have been nominal planer geometry. With modern HE it has been straightforward to shock tin into melt on release. However it has been challenging to achieve a low enough pressure for solid state on release. Here we propose to extend the existing base of knowledge to include the behavior of the free surface of tin in cylindrical converging geometry. By shock loading a cylindrical tin shell with a magnetically driven cylindrical liner impactor, the free surface evolution can be diagnosed with proton radiography. With the PHELIXmorexa0» capacitor bank, the drive can easily be varied to span the pressure range to achieve solid, mixed, and liquid states on release.«xa0less

Results and Prospects of Material Strength Studies on Electrophysical Facilities Based on Perturbation Growth in Liner Systems

Data of refined perturbation growth simulations of the three-layer cylindrical liner systems, tested during experiments with DEMGs (Disk Explosive Magnetic flux compression Generators) to study the strength properties of copper and polyethylene at shockless pressures up to ~15 GPa, and calculated performance data of the same liner systems for the Atlas experiments to study the strength properties of copper at shockless compression to ~40 GPa are presented. The feasibility of similar strength experiments with quasi-isentropic material compression to ~ 2000 GPa using DEMGs is demonstrated.