Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusion

Abstract

Magnetized Liner Inertial Fusion (MagLIF) [1] is a concept that involves using a pulsed electrical current to implode an initially-solid, cylindrical metal tube (liner) filled with preheated and magnetized fusion fuel. One-and two-dimensional simulations predict that if sufficient liner integrity can be maintained throughout the implosion, then significant fusion yield (>100 kJ) is possible on the 25-MA, 100-ns Z accelerator. The greatest threat to the liner integrity is the Magneto-Rayleigh-Taylor (MRT) instability, which first develops on the outer liner surface, and then works its way inward toward the inner surface throughout the implosion. Two-dimensional simulations predict that a thick liner, with R outer /∆R=6, should be robust enough to keep the MRT instability from overly disrupting the fusion burn at stagnation. This talk will present the first experiments designed to study a thick, MagLIF-relevant liner implosion through to stagnation on Z [2]. The use of beryllium for the liner material enabled us to obtain penetrating monochromatic (6151±0.5 eV) radiographs that reveal information about the entire volume of the imploding liner. This talk will also discuss experiments that investigated Z's pulseshaping capabilities to either shock-or shocklessly-compress the imploding liners [3], as well as our most recent experiments that used 2-micron-thick aluminum sleeves to provide high-contrast tracers for the positions and states of the inner surfaces of the imploding beryllium liners. The radiography data to be presented provide stringent constraints on the simulation tools used by the broader high energy density physics and inertial confinement fusion communities, where quantitative areal density measurements, particularly of convergent fusion targets, are relatively scarce. We will also present power-flow tests of the MagLIF load hardware as well as new micro-B-dot measurements of the azimuthal drive magnetic field that penetrates the initially vacuum filled interior of the liner during the implosion.

Instability growth for magnetized liner inertial fusion seeded by electro-thermal, electro-choric, and material strength effects

“…Implosions of hollow beryllium liners on the Z generator 5,6 at Sandia National Laboratories carried out by McBride et al 7,8 resulted in higher MRT amplitudes and wavelengths than those predicted by randomly initialised 3D MHD simulations, including the MHD code Gorgon, 9,10 indicating worse than expected performance in terms of confinement and robustness to liner-fuel mix. Code agreement was achieved only with the addition of an artificially azimuthally correlated initialisation.…”

Design of magnetized liner inertial fusion experiments using the Z facility

“…Since pulsed power is energy-rich, the liners are thick and massive with aspect ratios of order $10 (ratio of outer radius to liner thickness) in order to improve implosion robustness to magnetoRayleigh-Taylor (MRT) instability. 28 Radiography data from liner implosions on Z prior to integrated MagLIF experiments suggest the inner liner surface is sufficiently stable up to at least CR % 7, [29][30][31][32] and the presence of the B z field may provide further stabilization. 31 The liner materials contain no high atomic number dopants normally used to prevent x-ray preheat of the fuel, drive symmetry is not influenced by the presence of complex radiation flux from laser-plasma interaction, and simulations suggest the fuel can withstand higher amounts of mix.…”

Stability of fusion target concepts on Z.

“…Thus, the main thrust of this LDRD proposal was to study the key physics issue of liner stability. These experiments were extremely successful and resulted in several high-profile publications [6,7,8,9,10,11,12]. The results of these studies are summarized in Section 2.…”

“…We expect to publish these images and the corresponding analysis in a Physics of Plasmas article to be submitted in November 2012 as part of an invited talk by Ryan McBride at the APS-DPP meeting [12]. …”