Exploring the Physics of the Plasma Liner Experiment: A Multi-dimensional Study with FLASH, OSIRIS, and HELIOS

TL;DR

The paper addresses the challenge of achieving fusion via Plasma-Jet-Driven Magneto-Inertial Fusion by simulating all three PLX phases (target formation, liner formation, target compression) with the codesFLASH, OSIRIS, and HELIOS. The approach integrates fluid, kinetic, and radiation-transport physics to capture shocks, inter-jet interpenetration, and magnetized conduction, with cross-code validation across 1D to 3D regimes. Key findings include the formation of a preheated, magnetized target with electron Hall parameter >1 and peak temperature around 40 eV, and a quasi-collisional liner capable of compressing the target to fusion-relevant temperatures (>1 keV) in reactor-scale scenarios, with a 5% liner perturbation tolerance. Magnetic diffusion is identified as a constraint, mitigable by higher preheat or alternative liner materials, supporting the case for scaling PLX toward a reactor-scale fusion concept.

Abstract

The Plasma Liner Experiment (PLX) at Los Alamos National Laboratory (LANL) is a platform that seeks to achieve fusion via the Plasma-Jet-Driven Magneto-Inertial Fusion (PJMIF) concept. The experiment utilizes a constellation of plasma guns to generate fusion-relevant conditions and consists of three main phases: (1) target formation, in which up to four plasma guns shoot magnetized hydrogen or deuterium-tritium jets to form a quasi-spherical target, (2) liner formation, in which a 36 guns fire high-atomic-number (e.g., xenon) jets to form a liner shell, and (3) target compression, in which the formed liner implodes the pre-formed target. Each phase of the PLX operates in different plasma regimes, with different physics at play, thus each phase must be simulated separately with appropriate codes. In this study we highlight 1-, 2-, and 3-D simulation results of all three phases using the FLASH, OSIRIS, and HELIOS codes. Some of the key physical processes involved include shock dynamics, kinetic effects, anisotropic thermal conduction, resistive magnetic diffusion, radiation transport, and magnetized jet dynamics. The simulations show that the PLX can form a preheated ($\sim$40 eV), magnetized (electron Hall parameter $>$1) target plasma, and a quasi-collisional liner shell, which can subsequently compress the target to fusion-relevant conditions, reaching temperatures in excess of 1 keV.

Figures (12)

• Figure 1: Mass density (g cm-3 and electron temperature (eV) of two colliding jets that have formed a target plasma from a 2D axisymmetric FLASH simulation. This target reaches a volume-averaged density of $1.67\times10^{-10}$ g cm-3 and peak preheat temperatures of around 40 eV.
• Figure 2: Volume-averaged electron (red) and ion (blue) Hall parameters from the 2D jet collision simulation as a function of time. The values are averaged in a region where the target plasma is forming from $r = 0$ to $r = 25$ cm and $z = -15$ to $z = 15$ cm. Charged particles are considered magnetized when their Hall parameter is above unity (denoted by the black dashed line), which in this case eventually occurs for electrons but not for ions.
• Figure 3: Density evolution of two Xe liner plasma jets modeled using 1D OSIRIS. The horizontal axis is position (cm), left vertical axis is time in units of jet crossing times, and the total density (normalized to the initial value) is represented by the color map. The white lines represent the density profile of the left jet at the end of the simulation, normalized to the initial value and plotted with the right vertical axis; the location of the peak indicates how much the jets have interpenetrated. More interpenetration was observed at higher jet velocities.
• Figure 4: Total density evolution in the 1D liner jet merging simulations using OSIRIS, FLASH without radiation transport, and FLASH with radiation transport, for four jet velocities. FLASH simulations without radiation transport align with OSIRIS in the low-velocity (non-interpenetrating) regime. The inclusion of radiation transport in FLASH results in a more pronounced collapse of the liner.
• Figure 5: The $v_x$--$x$ phase space (plotted with left vertical axes) of the liner (upper row) and the fuel (bottom row) at $t=0$ (left column) and $t=3.7$$\mu$s (right column). The color bars represents particle number density in arbitrary units, to illustrate where in phase space the liner and fuel plasmas exist. The blue and orange solid lines correspond to the densities of the liner ($n_\mathrm{Xe}$) and fuel ($n_\mathrm{H}$) plasmas, respectively. The black dashed line corresponds to the amplitude of the external magnetic field ($B$). The densities were normalized to the initial value of the fuel, the external magnetic field was normalized to its initial value (50 T), and they are both plotted with the right vertical axes.