2.5 Levitation Diffusion Chamber Measurements of Ice Vapor Growth: Variability in the Deposition Coefficient

Monday, 7 July 2014: 11:30 AM
Essex Center/South (Westin Copley Place)
Jerry Y. Harrington, Pennsylvania State University, University Park, PA; and A. Harrison and A. M. Moyle

A new diffusion chamber with split button electrodes was used to grow levitated ice particles from the vapor. Ice particles were formed from 5 to 10 micron drops frozen while levitated inside the chamber at surface atmospheric pressure and temperatures ranging from -30 to -40C. Chamber supersaturation was determined from scattering by levitated sulfuric acid drops of a known composition. The traditional capacitance model overestimates the measured growth rates for all cases. The measured growth rates can be matched using a kinetically-limited growth model that predicts the deposition coefficient based on a critical supersaturation for growth. The derived critical supersaturations increase with decreasing temperature and are within the ranges of those determined from other experiments (2% to 7%). The deposition coefficients are not constant during growth and range from 0.01 to 0.3.
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