Gas convection caused by electron pressure drop in the afterglow of a pulsed inductively coupled plasma discharge

Neutral depletion is an important phenomenon in high-density plasmas. We show that in pulsed discharges, the neutral depletion caused by the electron pressure Pe plays an important role on radical transport. In the afterglow, Pe drops rapidly by electron cooling. So, a neutral pressure gradient built up between the plasma bulk and the reactor walls, which forces the cold surrounding gas to move rapidly toward the reactor center. Measured drift velocity of Al atoms in the early afterglow of Cl2/Ar discharge by time-resolved laser induced fluorescence is as high as 250 ms-1. This is accompanied by a rapid gas cooling.