Spherical Void Electrodynamic Levitator

Spherical Void Electrodynamic Levitator

The Spherical Void Electrodynamic Levitator (SVEL) uses AC and DC electric fields to stably trap and levitate charged particles or liquid droplets for minutes to days at a time. Once a particle is trapped, we can vary the conditions inside the atmospheric cell (temperature, pressure, carrier gas, gas mixture partial pressures) to perform a myriad of experiments related to cloud and aerosol properties. These include but are not limited to the formation and dissipation of cloud particles, deliquescence and efflorescence of salts, the changing chemistry of atmospheric particulates with time, and scattering and polarization studies of atmospheric particulates. Our results have implications for planetary atmospheres both near (Earth, Mars) and far (exoplanets orbiting far away stars). 

Redesign of SVEL Vacuum Chamber 

Dr. Johnson contacted JAFCI to discuss a redesign of her SVEL chamber. Vacuum leaks during experiments were the major problem she was encountering. The original SVEL chamber was built directly into a vacuum pump. Feedthroughs for AC and DC power as well as for thermocouple and relative humidity sensor were not fully vacuum sealed.

The design started with the idea of taking all feedthroughs out of the vacuum part of the setup. This was achieved by having the SVEL chamber as a stand-alone unit with only the actual vacuum shroud between the inner experimental chamber and outer wall being pumped. The feedthroughs could now be put outside the shroud; BNC, SHV and sensor connectors can be directly plugged into the base plate of the design.

A combined temperature and %RH sensor was discovered and subsequently used in the new design. A small box for electronics, attached to the baseplate, sends all signals via USB cable to a computer.

Since the experiment is temperature-controlled (RT to 180°C) through the inner stand and temperature transfer should be avoided, the inner stand was made from a machinable ceramic. The feedthroughs of the heating tubes were also isolated using peek tubes to avoid contact with the baseplate.