TEMPORAL BEHAVIOR OF CHARGED-PARTICLES IN A RADIO-FREQUENCY AFTERGLOWPLASMA CONTAINING NEGATIVE-IONS

Temporal behavior of charged particles in pure He and He-SF6 radio fre quency (rf) afterglow plasmas has been experimentally clarified for va rious SF6 gas concentrations (1, 25, 50%). The electron density in the pure He plasma increased just after the rf power was switched off, un like in a pure Ar plasma, and then decreased slowly. The increase was probably due to collisional ionization of metastable He atoms. The ele ctron density in the He-SF6 plasmas decreased exponentially. This was due to electron attachment to various molecules in the afterglow plasm a.