Growth and Saturation of Instability of Spherical Implosions Driven by Laser or Charged Particle Beams

Abstract

The inertial confinement approach to controlled fusion requires that small thin walled spherical shells of fuel and other materials by imploded, compressed and heated by laser or charged particle beams. In most cases of interest the implosion of such thin shells is unstable to the growth of spherical asymmetries. Two numerical simulation techniques were developed to study these instabilities. The first technique is used to study the small amplitude growth of the instabilities by employing a perturbation method. The derivation of the Hamiltonian model on which the technique is based is developed here. The second technique is a fully nonlinear two dimensional hydrodynamics and heat flow technique (PAL) which we have used to follow the large amplitude development and saturation of the instabilities. The examples of calculations shown demonstrate the utility of the method and the range of different saturation phenomena which may be expected.