  Inertial confinement fusion fuel suffers increased X-ray radiation losses
when carbon from the capsule ablator mixes into the hot-spot. Here we present
one and two-dimensional ion Vlasov-Fokker-Planck simulations that resolve
hot-spot self heating in the presence of a localized spike of carbon mix,
totalling 1.9% of the hot-spot mass. The mix region cools and contracts over
tens of picoseconds, increasing its alpha particle stopping power and radiative
losses. This makes a localized mix region more severe than an equal amount of
uniformly distributed mix. There is also a purely kinetic effect that reduces
fusion reactivity by several percent, since faster ions in the tail of the
distribution are absorbed by the mix region. Radiative cooling and contraction
of the spike induces fluid motion, causing neutron spectrum broadening. This
artificially increases the inferred experimental ion temperatures and gives
line of sight variations.
