  We present a series of experiments investigating the growth of ice crystals
from water vapor in the presence of a background gas. We measured growth
dynamics at temperatures ranging from -2 C to -25 C, at supersaturations
between 0.5 and 30 percent, and with background gases of nitrogen, argon, and
air at a pressure of one bar. We compared our data with numerical models of
diffusion-limited growth based on cellular automata to extract surface growth
parameters at different temperatures and supersaturations. These data represent
a first step toward obtaining precision ice growth measurements as a function
of temperature, supersaturation, background gas pressure and gas constituents.
  From these investigations we hope to better understand the surface molecular
dynamics that determine crystal growth rates and growth morphologies.
