  A model to describe the output particle distribution generated by particles
impinging on a planar target has been developed. This model was developed to
simulate positron production in the Cornell CESR Linac but can be applied to
targets using different types of particles.
  To model a specific converter target, the output particle distribution is
first simulated by tracking particles using the Geant4 toolkit which models the
fundamental physics of the conversion process. The Monte Carlo distribution
from Geant4 is fitted to a set of functions and the function coefficients are
saved for use in simulations. Using the fit functions in a simulation is not
only more portable but is also more than an order of magnitude faster than
running Geant4. This model has been successfully incorporated into the Bmad
simulation toolkit.
  The output position, angular orientation, and momentum distribution is
modeled. Preliminary support for modeling the polarization distribution is also
discussed.
