Research

ATMOSPHERIC PRESSURE MICRO-DISCHARGES

Introduction

We are exploring the physics, chemistry and applications of atmospheric pressure micro-discharges. Unlike conventional high pressure plasmas, these discharges operate in a stable glow mode. We have constructed an optical emission spectroscopy microscope and a focused laser microprobe coupled with a triple grating spectrometer to obtain 3-D imaging of gas temperature, electron temperature, electron density and electric fields, and compare these quantities to model predictions. We are also starting to explore the use of micro-discharges for trace chemical sensors.

Miniaturized (~ 100s of microns), high pressure (~ 1 atm) microdischarges are non-equilibrium plasmas with applications or potential applications in plasma display panels, chemical microreactors, sensors, VUV radiation sources, microelectromechanical systems (MEMS), and even plasma medicine. Spatially resolved (~5 microns resolution) optical emission spectroscopy measurements are performed with added traces of probe gases. Gas temperature profiles are determined using N2 rovibrational spectroscopy. Stark splitting of the hydrogen Balmer-β line is employed to investigate the electric field distribution in the cathode sheath region. Electron density is evaluated from the analysis of the spectral line broadening of Hβ emission. Excited species densities are measured with diode laser absorption spectroscopy. The effect of gas flow on gas temperature is also studied. These measurements combined with simulations of neutral gas and plasma flow provide valuable information regarding the operation of microplasmas, and guidelines on how to extend the useful range of operating pressure and power before the system turns into a (not as useful) high temperature arc. (please click here for PDF files on microdischarges I andmicrodischarges II).

Selected Publications

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