Degradation of performance in ICF implosions due to Rayleigh--Taylor instabilities: a Hamiltonian perspective*

Interfacial Rayleigh--Taylor (RT) instabilities are ubiquitous in inertial-confinement-fusion (ICF) implosions and are an important limiting factor of ICF performance. In this work, we obtain a first-principle variational theory that describes an imploding spherical shell undergoing RT instabilities. The model is based on a thin-shell approximation and includes the dynamical coupling between the imploding spherical shell and an adiabatically compressed fluid within its interior. Based on the derived Hamiltonian framework, degradation trends of key ICF performance metrics (e.g., stagnation pressure, residual kinetic energy, and aerial density) are identified in terms of the initial RT-instability parameters (initial amplitude and Legendre mode). Nonlinear results are obtained by numerically integrating the governing equations of this reduced model.