  We report on simulations of counter-propagating laser-produced plasmas in an
inertial confinement fusion (ICF) hohlraum surrogate, aiming to replicate
observations reported by Le Pape et. al in recent work. The conditions of the
colliding plasmas are relevant to ICF hohlraums used for indirect-drive
ignition, and are obtained both with and without low-density He-gas fill. We
compare experimental diagnostics to outputs from simulations using the 1D-2V
Vlasov-Fokker-Planck kinetic code iFP and the xRAGE radiation-hydrodynamics
code. These include the inferred radial lineouts of inferred ion number
fraction and ion and electron temperatures, as well as the reported
experimental Thomson-scattering (TS) spectra (compared via synthetic TS
diagnostics). We observe that 1D kinetic simulations capture the plasma states
reported in the experimental diagnostics quite well. Counter-intuitively, the
kinetic simulations capture the gas-fill experiment (expected to be more
`hydro-like') better than the vacuum experiment, while the reverse is observed
for hydrodynamic simulations. This is attributed to the presence of non-trivial
multi-dimensional hydrodynamic effects which are more dominant in the vacuum
experiment. These effects are somewhat inhibited in the gas-fill experiment,
permitting quasi-1D kinetic plasma transport to play more of a role in
producing plasma interpenetration. Differences between the effects of
Maxwellian vs. non-Maxwellian (`full f') synthetic TS diagnostics are
investigated for the kinetic simulations. We find non-Maxwellian TS spectra
differ non-trivially from Maxwellian spectra, which suggests caution may be
warranted when applying Maxwellian TS models to infer plasma conditions via
backward modeling when kinetic effects may be present.
