Corona-glow transition in the atmospheric pressure RF-excited plasma needle

Y. Sakiyama (University of Tokyo)

The atmospheric pressure RF-excited plasma needle is a non-thermal
discharge powered at 13.56 MHz with localized plasma sustained at the sharp
tip of a thin cylindrical conducting electrode. Using a finite element
solution to the governing fluid equations, we identify two discharge modes
of the plasma needle as well as the transition mechanism. The gas used is
helium with a small amount of nitrogen. The needle has a point-to-plane
geometry and an inter-electrode gap of 1 mm. The plasma needle operates as
a corona discharge at low power and a glow discharge at high power. In the
corona mode, the peak plasma density and ionization is confined near the
needle tip. On the other hand, an additional ionization peak appears near
the planar electrode in the glow mode. In addition, we observe the plasma
spreads back along the needle surface. The corona-glow transition is
characterized by a dramatic decrease in sheath thickness near the needle
tip as well as the sheath heating near the planar electrode. Experimental
validation of the model predictions is discussed.


Biography:
1997: BS at Mechano-Aerospace Engineering, Tokyo Institute of Technology
1999: MS at Mechano-Aerospace Engineering, Tokyo Institute of Technology
2002: PhD at Mechanical Engineering, University of Tokyo
2002-present: Research associate at Mechanical Engineering, University of Tokyo
2003-2004: Visiting scholar at MST-8, Los Alamos National Laboratory
2005-present: Visiting scholar at Chemical Engineering, UC Berkeley, Prof.
D.B.Graves group