Suppression of Rayleigh-Taylor Instability Using High-Z Doped Plastic Targets for Inertial Fusion Energy

Abstract

A scheme to suppress the ablative Rayleigh-Taylor (RT) instability using high-Z doped plastic target (brominated polystyrene;CHBr) has been proposed for a directly laser-driven IFE target. When an intense laser irradiates directly onto a high-Z doped target, radiation emitted from a corona plasma propagates and deposits locally its energy inside the target. The enhanced radiation forms the double-ablation structure, which consists of primaryelectron conduction ablation front and secondary radiative ablation front. The radiative ablation in the double-ablation structure has many advantages to suppress the growth of the RT instability in analogy of the indirect-drive approach, i.e. large mass ablation rate, long density scale length and low peak density. Two-dimensional (2D) hydrodynamic simulation code shows strong suppression of the RT instability in a brominated plastic (CHBr) target compared with that in an undoped polystyrene (CH) target. RT growth rates evaluated theoretically using the Betti-Goncharov procedure with one-dimensional(1D) radiation-hydrodynamic simulation are in good agreement with 2D simulation results. Several experiments were performed at the GEKKO XII- HIPER (High Intensity Plasma Experimental Research) laser facility. A trajectory of a laser-driven CHBr target observed in experiment was reproduced fairly well by 1D simulation code. The double-ablation structure formed inside a directly laser-driven CHBr target was clearly observed in experiments for the first time The strong suppression of the RT instability in the CHBr target was confirmed in experiments with face-on and side-on x-ray backlighting technique.