  In a plasma of multiple ion species, thermodynamic forces such as pressure
and temperature gradients can drive ion species separation via inter-species
diffusion. Unlike its neutral mix counterpart, plasma thermo-diffusion is found
comparable to, or even much larger than, baro-diffusion. It is shown that such
a strong effect is due to the long-range nature of the Coulomb potential, as
opposed to short-range interactions in neutral gases. A special composition of
the tritium and 3He fuel is identified to have vanishing net diffusion during
adiabatic compression, and hence provides an experimental test in which yield
degradation is minimized during ICF implosions.
