Impact of Rayleigh--Taylor instabilities on the loss of confinement and on the ignition threshold in ICF implosions

Interfacial Rayleigh--Taylor instabilities (RTI) are ubiquitous in inertial-confinement-fusion (ICF) implosions and are an important limiting factor of ICF performance. To understand the connection between RTI and the developed asymmetries in areal density, we recently developed a first-principle variational theory that describes an imploding spherical shell undergoing RTI [1]. As a continuation of this work, we use this model to investigate the effects of RTI on the loss of confinement during the stagnation phase. In addition, we derive a generalized ignition criterion that accounts for the presence of RTI, and we study the dependencies of this ignition threshold on initial RTI parameters (e.g., the initial amplitude and Legendre mode), as well as the 1D implosion characteristics (e.g., the convergence ratio). We compare analytical results from quasilinear theory against fully nonlinear results obtained by numerically integrating the governing equations of this reduced model.

[1] D. E. Ruiz, “Degradation of performance in ICF implosions due to Rayleigh—Taylor instabilities: a Hamiltonian perspective,” to be submitted to Phys. Plasmas.