COLLABORATIVE RESEARCH: Laboratory Simulation of Lightning and Dusty Plasmas

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(In collaboration with EPS 00-80862)Scientists at the Desert Research Institute (Atmospheric Sciences); University of Nevada, Reno (Department of Physics, High Energy Density Science Group), and the School of Meteorology at the University of Oklahoma will collaborate to design and construct a system to simulate and study, in the laboratory, electrical discharges through atmospheres containing cloud and aerosol particles over a wide range of terrestrial and also extraterrestrial conditions. Lightning, as an electrical discharge, occurs through the atmosphere in and above thunderstorms, in volcanic eruptions and in clouds of other planets, notably Jupiter. The system will also be well suited to study certain industrial processes for producing and modifying aerosol (such as diamond) and the technology of protection from lightning strikes to spacecraft launch vehicles and electrical transmission systems. It will have a high voltage capability, up to one million volts, with a discharge current of up to 100,000 amps through a cubic meter laboratory cloud chamber with controlled gas composition, pressure, temperature and relative humidity and will be capable of being filled with particulate clouds of both volatile materials, such as water droplets and ice crystals, as well as aerosol of low volatility, such as certain minerals and alkali halides. The electrical system will consist of a Marx bank parallel - series arrangement of capacitors together with additional elements, with capability for control of voltage, current and current rise and fall time. The chamber will carry appropriate feed-throughs and electrodes for direct discharge and an inductive loop to give an electrode-less ring discharge. The time constants of current rise and fall (on the order of 100 nanoseconds and 10 microseconds, respectively) will be controlled to give direct simulation of atmospheric and other processes. Measurements will be made of the form and speed of the discharge using a streak camera and gated optical detectors. The role of particulates of different size, shape and composition as they relate to changes in trace gas composition will be investigated and emissivity/absorption measurements in selected visible, UV and x-ray wavelengths will also be performed. The chamber will be designed with internal sensors and appropriate transmission windows for external laser diagnostics. The utility of the system will be demonstrated in the second year through initial studies of the leading discharge tip through ice and water cloud interfaces and in the rate of NOx production, both of which are current scientific issues in atmospheric science.