Vlasov–Fokker–Planck Modeling of Heat Flow Modifications Caused by Laser Absorption and Pondermotive Transport Effects*

It has long been recognized that intense laser fields can modify electron transport in inertial confinement fusion (ICF) plasmas, especially near the critical density where a steep intensity gradient develops. A detailed kinetic understanding of transport in this scenario demands accounting for ponderomotive forces, collisional absorption, and electron–electron collisions with minimal approximations. To study these effects, we developed an extended Vlasov–Fokker–Planck approach where the distribution function is split into quasi-static (dc) and quasi-harmonic (ac) components, which obey coupled kinetic equations. The coupling terms give rise to inverse bremsstrahlung absorption, pondermotive forces, and modifications to the electron–electron collision operator. We demonstrate that these effects combine to dramatically alter the heat flux near the critical density. We discuss implications for direct-drive ICF and highlight the role of bandwidth relevant to next-generation broadband laser systems.