Progress in high-energy-density physics and pulsed-power ICF on the refurbished Z facility

Abstract

Pulsed power provides efficient and low cost compression of energy in space and time. A five-year upgrade of the 18 MA Z pulsed-power facility was completed in September of 2007. This upgrade has doubled the stored electrical energy of the facility to 22 MJ and has already enabled peak currents of up to 26 MA in some experiments. In particular, the facility design enables current pulse shaping out to drive pulse-lengths of 300 to 600 ns for flyer plate and isentropic compression experiments on the dynamic properties of materials at high pressures. A vigorous high energy density physics program was pursued in parallel with facility and diagnostic commissioning over the last 20 months. Experiments were routinely executed over a broad range of applications including dynamic materials, z-pinch instability physics, x-ray source optimization for soft x-ray and K-shell x-ray sources, and spectroscopic measurements of photo-ionized neon plasmas, and iron opacity. Recent results, demonstrated at facility charging voltages of up to 82 kV, include the re-establishment of a dynamic hohlraum opacity platform at peak currents of nearly 24 MA generating higher electron temperatures and densities than previously, demonstration of peak currents of 26 MA into loads at short (120 ns) and long pulses (300 ns), peak soft x-ray powers of 250 TW produced by a z-pinch, isentropic compression of Ta up to pressures of nearly 4 Mbar, and measurements of the strength of Be at pressures of up to 1 Mbar. Significant advances have also been made in diagnostics. Routine two-frame and two-color radiography using the Z-Beamlet laser with bent crystal imaging at spatial resolutions of 20 µm has been demonstrated. Load currents measurements have been performed close to the load by inferring magnetic pressures from VISAR velocity measurements. Spectroscopy has been used to measure z-pinch implosion and stagnation dynamics in detail. Recent work on new concepts for pulsed power driven Inertial Confinement Fusion (ICF) will be shown. Finally, advances in pulsed power technology and implications for a next-generation z-pinch facility will also be discussed.