Investigation of electron heat conduction in laser produced exponential plasma density profiles

Abstract

In laser produced plasmas, the exponential electron density profiles makes modeling electron heat conduction difficult due to the variation in the electron mean free path. As a result, most radiation hydrodynamic simulations implement a flux limited diffusion model which applies a fractional multiplier to the Spitzer conductivity. While comparisons with experimental observations have provided guidance on the value of the flux limiter for various experimental configurations, there is always uncertainty especially when modeling new types of targets. In the work here, Collective Thomson scattering measurements of the spatial and temporal electron temperature profile resulting from a on micron laser incident on a preformed exponential density profile is presented. The spatial measurements straddle the critical surface for the 1ω light observe both heat conduction into the over-dense and under-dense regions of the plasma. These measurements provide a proof-of-principle approach to performing well diagnosed experiments that can validate Fokker-Planck or analytic heat conduction models. The development of such models should provide a first principles approach to modeling heat conduction in radiation hydrodynamic codes replacing the current ad hoc method.