Hydrodynamic Symmetry and Stability of a Heavy Ion Beam-Driven Planar Icf Target.
The two-dimensional hydrodynamic stability and symmetry of a direct-driven planar inertial confinement fusion (ICF) target irradiated by a heavy ion beam is investigated in a four-step process. First, critical reviews and extensions of current theory are presented for hydrodynamic stability theory and its application to symmetry and stability problems in ICF (i.e., a new interpretation of limiting spike motion in the nonlinear R-T instability), analytical theory of beam-coupled hydrodynamics (i.e., a new steady-state 1 -D model), and charged-particle slowing-down theory (i.e., recognition of the applicability of the unified slowing -down theory). Second, a self-consistent two-dimensional particle-in-cell (PIC) representation of the ion beam-target interaction and hydrodynamic response is developed. This model, known as FLIP (fluid implicit particle), was developed specifically for the accurate modeling of unstable and distorted hydrodynamic flow in ion beam-driven ICF targets. Third, the PIC numerical model is studied, verified, and tested by comparison with exact analytic solutions and other published calculations. Fourth, the numerical model is used to study the hydrodynamic response of a tamped, HIBALL-like planar ICF target in two dimensions. Two-dimensional hydrodynamic flow of the planar HIBALL ICF target is numerically studied for the following cases: (1) an initially uniform target imploded by a normally incident, 10 GeV Bi^+ beam with a spatially uniform, time-dependent intensity (2) an initially uniform target imploded by a normally incident, 10 GeV Bi^+ beam with an intensity perturbed in a direction lateral to the beam propagation; and (3) an initially nonuniform target imploded by a normally incident, 10 GeV Bi^+ beam with a uniform intensity. Beam intensity perturbation wavelengths close to target shell thicknesses appear to have the most disastrous effects on implosion symmetry. Tolerable beam intensity perturbation amplitudes depend on the zero order intensity (5-10% at 1 TW/cm^2 and 1% at 1000 TW/cm^2 for intensities constant in time). Reactor beam pulses may possibly result in a target more tolerable to asymmetries. Initial surface perturbations in the planar HIBALL-like target irradiated at 1 TW/cm^2 were the most disastrous for those imposed at the tamper/absorber interface. Perturbation growth at the pusher/fuel interface appears to be more easily predicted and less complicated than in laser-driven targets.
- Pub Date:
- Physics: Fluid and Plasma