Abstract
Time-resolved Langmuir probe technique has been applied to the afterglow of pulsed discharge in low pressure Hg-Ar mixtures. The basic procedure consists in applying a ramp voltage, with a rise time of the order of a few minutes, to the probe and sampling with a 2-channel boxcar integrator the probe current and the probe voltage at specified times during the afterglow. The pmobe current _??_ voltage characteristics during the most portion of time of the afterglow exhibit normal curves for the positive ion saturation region, transition region and the electron saturation region, giving quite reasonable results of electron temperatures, plasma densities and space potentials respectively. From the logarithmic plotting of the plasma density against time we have obtained the ambipolar diffusion coefficient Dap=350cm2•s-1•Torr, in good agreement with calculated value Dap=360cm2•s-1•Torr, which is derived using Chanin's atomic mercury ion mobility in argon.
An unexpected result is that the probe characteristics just after the cut-off of the pulsed discharge (within 100μs after the ionizing field is removed).demonstrate the presence of high energy electrons. These are assigned to the acceleration by the field that possibly occurs between the plasma and the wall of the discharge tube
