Transient striations during gas breakdown under radio-frequency excitation.

During gas breakdown between two parallel-plate electrodes excited by radio frequency (RF), a time-dependent striated optical emission structure is experimentally observed. Its formation process is reproduced and explained using particle-based simulations. The striations appear due to significantly different mobilities of ions and electrons, which lead to the formation of space charge in the vicinity of the extrema in the charged-particle densities under a strong RF electric field. The striated structures of the charge density as well as other parameters are amplified by locally enhanced ionization rates associated with the growing charged-particle density, and are eventually suppressed as the RF electric field is progressively screened from the discharge central region.