Cylindrical implosion experiments using laser direct drive

Abstract

Direct-drive cylindrical-implosion experiments are performed to study perturbed hydrodynamic flows in convergent geometry. Two experimental campaigns have been conducted, to demonstrate the advantages of direct over indirect drive and to validate numerical simulations of zeroth-order hydrodynamics and single-mode perturbation growth. Results and analysis of three unperturbed-target shots and two perturbed-target shots are discussed in detail. For unperturbed-target implosions, positions of inner and outer shell edges agree between simulation and experiment during the laser pulse. However, observed shell thickness is greater than simulated in unperturbed targets during deceleration and rebound; the effect appears only at the shell’s exterior edge. For perturbed-target implosions, growth factors ∼10–14 are observed, whereas growth factors near 30 are expected from simulation. Rayleigh–Taylor growth appears to differ between simulation and experiment. Observed zeroth-order flow at the exterior edge of imploding, perturbed targets appears to differ from simulation, even during acceleration. A possible physical model to explain such apparent differences is identified.