Non-equilibrium and self-organization evolution in hot-spot ignition processes

Abstract

In inertial confinement fusion systems, achieving ignition can be pursued through two main approaches—central hot-spot ignition and fast ignition. Due to disparate formation mechanisms in these methods, the initial temperatures of electrons and ions in the hot spot often differ, highlighting the limitations of equilibrium theoretical models in accurately capturing the ignition conditions and evolution of the hot spot. In this work, we present a non-equilibrium model and extended this model to both isobaric and isochoric scenarios, characterized by varying hot-spot densities, temperatures, and expansion velocities. In both cases, a spontaneous self-organization evolution was observed, manifesting as the bifurcation of ion and electron temperatures. Notably, the ion temperature is particularly prominent during the ignition process. This inevitability can be traced to the preponderant deposition rates of alpha-particles into D–T ions and the decreasing rate of energy exchange between electrons and D–T ions at elevated temperatures. The inherent structure, characterized by higher ion temperature and lower electron temperature during ignition, directly contributes to the augmentation of D–T reactions and mitigates energy losses through electron conduction and bremsstrahlung, thereby naturally facilitating nuclear fusions.