AVS 51st International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThM

Paper PS-ThM5
Diagnostics of High Pressure DC Helium Microplasma Discharge

Thursday, November 18, 2004, 9:40 am, Room 213A

Session: Atmospheric and Microdischarges
Presenter: Q. Wang, University of Houston
Authors: Q. Wang, University of Houston
I. Koleva, University of Sofia, Belgium
D.J. Economou, University of Houston
V.M. Donnelly, University of Houston
Correspondent: Click to Email
Gas and plasma diagnostics were performed in a slot-type DC microplasma (200 microns gap) discharge at high pressures. The gas temperature in a helium discharge was estimated by adding small quantities of nitrogen (<100 ppm) into the gas feed. Specific vibrational bands (v'v"), namely (1,3), (0,2) and (1,4) of the N@sub 2@ second positive system, were carefully selected to avoid interference with emission from He atoms and He@sub 2@ excimer. At 250 Torr pressure and 200 mA/cm@super 2@ current density, the gas temperature was T@sub g@ = 350 ± 25 K. The measured gas temperature was almost independent (to within experimental uncertainty) of pressure (in the range of 150 Torr - 600 Torr), and current density (in the range of 100 mA/cm@super 2@ - 400 mA/cm@super 2@). These measurements were consistent with a simplified heat transfer model. Spatially resolved measurements of electron temperature were also performed using trace rare gas optical emission spectroscopy (TRG-OES). These measurements are greatly complicated by collisional quenching at the high operating pressures. Electron density and electron temperature profiles was deduced by comparing emission intensities from the Paschen 2p@sub x@ (x = 1-10) manifold of Ne, Ar, Kr and Xe trace gases. Results suggest that the electron temperature peaks in the cathode sheath region, while the plasma density peaks away from the cathode sheath. A self-consistent fluid model of a DC helium microdischarge was in agreement with the experimental data. Work supported by DOE/NSF.