We describe an experimental apparatus for making detailed morphological
observations of the growth of isolated plate-like ice crystals from water
vapor. Each crystal develops a plate-on-pedestal (POP) geometry, in which a
large, thin, plate-like crystal grows out from the top edge of an initially
prismatic seed crystal resting on a substrate. With the POP geometry, the
substrate is not in contact with the growing plate (except at its center), so
substrate interactions do not adversely affect the crystal growth. By
controlling the temperature and supersaturation around the crystal, we can
manipulate the resulting ice growth behavior in predictable ways, producing
morphologies spanning the full range from simple faceted hexagonal plates to
complex dendritic structures. We believe that the experimental apparatus
described here will allow unprecedented investigations of ice crystal growth
behaviors under controlled conditions, identifying and exploring robust
morphological features in detail. Such investigations will provide valuable
observational inputs for developing numerical modeling techniques that can
accurately reproduce the faceted and branched structures that frequently emerge
during diffusion-limited crystal growth
