Ice Grain Structure and Growth in the Caltech Water-Ice Dusty Plasma Experiment

The Water-Ice Dusty Plasma Experiment at Caltech investigates the nucleation and dynamics of water-ice dust grains in a plasma. Capacitively-coupled RF electrodes are cooled to cryogenic temperatures, creating a weakly-ionized plasma with very cold neutral temperature. Water vapor injected into the plasma nucleates spontaneously to form quickly-growing ice grains. The ice grains are observed to have an elongated fractal structure reaching up to 700 microns in length, and are imaged with both a long-distance microscope camera and a laser diffraction scheme[1,2]. A Fourier Transform Infrared (FTIR) Spectrometer is being set up to characterize composition and phase of the solid dust grains, giving insight into the microstructure of the ice grains. These properties will be studied at a range of pressures and temperatures, determining the ice phase diagram and examining the transition between crystalline and amorphous ice grains.



[1] K. B Chai and P. M. Bellan, Geophysical Research Letters 40, 6258 (2013)

[2] K. B Chai and P. M. Bellan, Astrophysical Journal 802, Art. No. 112 (2015)



Supported by NSF/DOE Partnership in Plasma Science and Engineering via DOE Award DE-SC0020079