Relaxation oscillations in a capacitive discharge chamber connected to a peripheral grounded chamber

We have observed relaxation oscillations in an argon capacitive discharge connected to a peripheral grounded chamber through a slot with dielectric spacers. The oscillations, observed from time-varying optical emission of the main discharge chamber, show, for example, a high frequency (similar to 40 kHz) relaxation oscillation at 100 mTorr, with absorbed power near that for peripheral breakdown, and a low frequency (similar to 3 Hz) oscillation, at higher absorbed power. The high frequency oscillation is found to ignite a plasma in the slot, but usually not in the periphery. We interpret the high frequency oscillations using an electromagnetic model of the slot impedance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations and indicate a variety of behaviors dependent on the matching conditions. (c) 2006 American Institute of Physics.