  Radio-frequency (RF) carpets with ultra-fine pitches are examined for ion
transport in gases at atmospheric pressures and above. We develop new analytic
and computational methods for modeling RF ion transport at densities where
dynamics are strongly influenced by buffer gas collisions. An analytic
description of levitating and sweeping forces from phased arrays is obtained,
then thermodynamic and kinetic principles are used to calculate ion loss rates
in the presence of collisions. This methodology is validated against detailed
microscopic SIMION simulations. We then explore a parameter space of special
interest for neutrinoless double beta decay experiments: transport of barium
ions in xenon at pressures from 1 to 10 bar. Our computations account for
molecular ion formation and pressure dependent mobility as well as finite
temperature effects. We discuss the challenges associated with achieving
suitable operating conditions, which lie beyond the capabilities of existing
devices, using presently available or near-future manufacturing techniques.
